A thermal-economic analysis of a transcritical Rankine power cycle with reheat enhancement using a low-grade industrial waste heat is presented. Under the identical operating conditions, the reheat cycle is compared to the non-reheat baseline cycle with respect to the specific net power output, the thermal efficiency, the heat exchanger area, and the total capital costs of the systems. Detailed parametric effects are investigated in order to maximize the cycle performance and minimize the system unit cost per net work output. The main results show that the value of the optimum reheat pressure maximizing the specific net work output is approximately equal to the one that causes the same expansion ratio across each stage turbine. Relative performance improvement by reheat process over the baseline is augmented with an increase of the high pressure but a decrease of the turbine inlet temperature. Enhancement for the specific net work output is more significant than that for the thermal efficiency under each condition, because total heat input is increased in the reheat cycle for the reheat process. The economic analysis reveals that the respective optimal high pressures minimizing the unit heat exchanger area and system cost are much lower than that maximizing the energy performance. The comparative analysis identifies the range of operating conditions when the proposed reheat cycle is more cost effective than the baseline. Copyright © 2012 John Wiley & Sons, Ltd.

Drying is a high-energy-intensive operation and an important step in the pasta production. In this study, exergy analysis of a four-step drying system in a farfalle pasta production line using actual operational data obtained from a plant located in Izmir, Turkey, was performed. Exergy loss rates, evaporation rates, exergy efficiencies, and improvement in potential rates for each dryer section were determined in this drying system. The exergy efficiency values varied between 0.25% and 5.27% from the predrying to the final drying section. The exergy efficiency value for the entire drying system was calculated to be 2.96%, and the highest exergetic improvement in potential rate was 165.54 kW for the first dryer section. Copyright © 2012 John Wiley & Sons, Ltd.

A four-step drying system in a farfalle pasta production line was exergetically analyzed for assessing and improving the efficiency of the drying process and the entire system along with its main components. Actual operational data were used in the analysis. The exergy efficiency values varied between 0.25% and 5.27% from the predrying to the final drying section, being 2.96% for the entire drying system. The highest exergetic improvement in potential rate (IP) was 165.54 kW for the first dryer section.

Well-ordered Nafion-silica-HPW proton exchange membranes with Nafion ionomers as co-surfactant have been synthesized through a facile self-assembly between the positively charged silica, negatively charged HPW acids, and Nafion ionomers. The results exhibited uniform nanoarrays with long-range order when Nafion content in the complex is lower than 30 wt%. The electrolyte stripe textures were clearly presented with an interval channel of 5–6 nm. The well-ordered proton conducting sites made the proton move through the membrane freely with low humidity dependence of proton transportation through the Nafion-silica-HPW electrolyte. The proton conductivities of the Nafion-silica-HPW electrolyte with Nafion content of 10–30 wt% were 0.018–0.022 Scm⁻¹ at 25 °C without humidification, and the conductivities increased to 0.043–0.05 Scm⁻¹ when the temperature increased to 200 °C. The capillary condensation of the ordered structure also improved the water uptake of the Nafion-silica-HPW electrolyte at low humidity. With external humidifying of 25 RH%, the water uptake of the Nafion-silica-HPW electrolyte with Nafion content of 10–30 wt% reached to 15–23 wt% at elevated temperature of 100–200 °C. The improvement of the water uptake facilitated proton transport through the Nafion-silica-HPW electrolytes, resulting in proton conductivities of 0.082–0.095 Scm⁻¹ at temperature of 150–200 °C, 25 RH%. Copyright © 2012 John Wiley & Sons, Ltd.

This article examines the exhaust waste heat recovery potential of a microturbine (MT) using an organic Rankine cycle (ORC). Possible improvements in electric and exergy efficiencies as well as specific emissions by recovering waste heat from the MT exhaust gases are determined. Different dry organic working fluids are considered during the evaluation (R113, R123, R245fa, and R236fa). In general, it has been found that the use of an ORC to recover waste heat from MTs improves the combined electric and exergy efficiencies for all the evaluated fluids, obtaining increases of an average of 27% when the ORC was operated using R113 as the working fluid. It has also been found that higher ORC evaporator effectiveness values correspond to lower pinch point temperature differences and higher exergy efficiencies. Three different MT sizes were evaluated, and the results indicate that the energetic and exergetic performance as well as the reduction of specific emissions of a combined MT-ORC is better for small MT power outputs than for larger MTs. This article also shows how the electric efficiency can be used to ascertain under which circumstances the use of a combined MT-ORC will result in better cost, primary energy consumption, or emission reduction when compared with buying electricity directly from electric utilities. Copyright © 2012 John Wiley & Sons, Ltd.

Small hydropower (SHP) projects are considered by the developers as these provide renewable source of energy and are environment friendly. The basic cost components of SHP scheme are broadly classified as civil works and electromechanical equipment. The most important components under the electromechanical equipment are turbine and generator. In the present paper, an attempt has been made to review the different types of technological models and transfer function developed to evaluate the performance of the electromechanical equipment of SHP projects. A review on the different types of control strategies developed by earlier investigators has also been presented. The present review attempts to cover the different types of design and analysis made on different types of turbines, generator and control equipment of SHP. Copyright © 2012 John Wiley & Sons, Ltd.

A biomass fired double-stage Organic Rankine Cycle (ORC) for micro-cogeneration is studied. Focus is laid on optimizing thermal efficiency in summer mode by appropriate working fluid and pressure level selection. Simulation and thermodynamic analysis show that in double-stage ORC, the working fluid in the low-temperature circuit (LTC) effects total efficiency more than the working fluid in the high-temperature circuit (HTC). Within the chosen boundary conditions, isopentane gives best thermal efficiency, whereas R227ea is the least efficient in the LTC. Among the working fluids for the HTC, maximum total efficiency is similar for several working fluids. Simulations demonstrate that a prediction of thermal efficiencies with respect to physico-chemical characteristics of different working fluids is only feasible within certain chemical classes. In the HTC, low critical temperature, low molar mass, and high critical pressure increase the efficiency, whereas in the LTC, condensation pressure is most crucial for high efficiency. Constructional analysis indicate that in the majority of cases, an increase in thermal efficiency is connected with high-volume flow rates at the outlet of the turbine, which leads to voluminous expansion units and high investment costs, respectively. Appropriate working fluid combinations within a double-stage ORC reach total efficiencies of up to 35% at flue gas temperatures from 950 to 150 °C. Copyright © 2012 John Wiley & Sons, Ltd.

Double-stage Organic Rankine cycle have been studied thermodynamically and under constructional aspects of expansion unit. Analysis of 35 fluids out of 5 chemical classes showed that fluid combination decane/isopentane has high potential in efficiency. Transmitted heat flow to low temperature circuit divided to that of high-temperature circuit is a crucial factor for total efficiency.

In this study, four fatty acids of lauric acid (LA), myristic acid (MA), palmitic acid (PA), and stearic acid (SA) were selected to prepare six binary fatty acid eutectics of LA-MA, LA-PA, LA-SA, MA-PA, MA-SA, and PA-SA; thereafter, electrospun ultrafine composite fibers with the binary fatty acid eutectics encapsulated in the supporting matrices of polyethylene terephthalate (PET) were prepared as innovative form-stable phase change materials for storage and retrieval of thermal energy. The morphological structures and thermal energy storage properties of the ultrafine composite fibers were characterized by scanning electron microscope (SEM) and differential scanning calorimeter (DSC), respectively. The SEM results indicated that the fibers had the cylindrical morphology with diameters of 1–2 µm; some had smooth surfaces, while others had wrinkled surfaces with grooves. The DSC results indicated that the phase transition temperatures of binary fatty acid eutectics were lower than those of individual fatty acids; the enthalpy values associated with melting and crystallization for the eutectics encapsulated in the composite fibers were considerably reduced, whereas there were no appreciable changes on the phase transition temperatures. Copyright © 2012 John Wiley & Sons, Ltd.

This article develops the concept of renewable-energy-based multigeneration options for producing a number of outputs, such as power, heat, hot water, cooling, hydrogen, fresh water, and so forth; and discusses their benefits. Such multigeneration options obviously lead to improved system performance and reduced environmental impacts. First, single-generation (power generation only) and cogeneration systems are compared with respect to the energy utilization efficiency, exergy efficiency, green house gases (GHG) mitigation, and payback period. It is found that the cogeneration increases GHG mitigation about 2 to 4 times, whereas the payback time decreases about 2.8 times with respect to the single-generation case. Exergy efficiency is found to be between about 55% and 65%, depending on the degree of cogeneration. The exergy efficiency shows the maximum values for certain source temperatures. For the case studied here, the optimum source temperature is taken as 200°C for analysis purposes. The results show that multigeneration of energy systems helps increase both energy and exergy efficiencies, reduce cost and environmental impact, and increase sustainability. Copyright © 2012 John Wiley & Sons, Ltd.

Chemical looping reforming (CLR) is a novel technology that can be used for reforming of cheaply available abundant biofuel like ethanol for the production of hydrogen/syngas for fuel cells. A systematic thermodynamic study for the CLR process using selected oxygen carriers was done to analyze the products and energy requirements of the CLR process in the temperature range of 500–1200 °C at 1 bar pressure for ethanol. The results showed favorable conditions for syngas manufacture from this process. Fe₂O₃ was found to be the best performing oxygen carrier followed by calcium and sodium sulfates, while Mn oxides were the least preferred oxygen carriers for CLR of ethanol process. The optimum process temperature was found to be 1000 °C. The actual CLR-ethanol process shows exothermicity against the theoretical endothermic partial oxidation of ethanol. The results obtained in this theoretical study can pave the way for experimental programs for syngas generation for SOFC-type fuel cells. Similar studies can be undertaken for other fuels for fuel processor development by CLR process. Copyright © 2012 John Wiley & Sons, Ltd.

The solar-driven dissociation of CO₂ by thermochemical looping via Fe₃O₄/FeO redox reactions is considered. The process recycles and upgrades CO₂ to ultimately produce chemical synthetic fuels from high-temperature solar heat and abundant feedstock as only inputs. The two-step process encompasses the endothermic reduction of Fe₃O₄ to FeO and O₂ using concentrated solar energy as the high-temperature source for reaction enthalpy and the nonsolar exothermic oxidation of FeO with CO₂ to generate CO. The resulting Fe₃O₄ is then recycled to the first step and carbon monoxide can be further processed to syngas and serve as the building block to synthesise various synfuels by catalytic processes. This study examines the thermodynamics and kinetics of the pertinent reactions. The high-temperature thermal reduction of Fe₃O₄ is realised above the oxide melting point by using concentrated solar thermal power. The reactivity of the synthesised FeO-rich material with CO₂ at moderate temperature is then investigated by thermogravimetry. FeO conversion higher than 90% can be achieved with reaction rates depending on temperature, particle size and CO₂ concentration. The solar-produced nonstoichiometric FeO is more reactive with CO₂ than commercial pure FeO. Activation energies of 57 and 68 kJ/mol are derived from a kinetic analysis of the CO₂-splitting reaction in the range of 600 °C to 800 °C with solar and commercial FeO, respectively. Copyright © 2012 John Wiley & Sons, Ltd.

A solar thermochemical process to recycle and upgrade the CO₂ emissions has been experimentally demonstrated. CO₂ is dissociated by two-step solar chemical looping with iron oxides for the production of synthetic fuels. Thermogravimetric analysis showed the high reactivity of solar-produced FeO with CO₂ to generate CO that can be further processed to syngas and liquid fuels by catalytic processes. The process thus converts low-grade feedstock to high-value solar fuels.

Thermal management systems (TMS) are one of the key components of electric and hybrid electric vehicles to achieve high vehicle efficiency and performance under all operating conditions. Current improvements in electric battery technology allow vehicles to have relatively long ranges, fast acceleration, and long life while keeping low-maintenance costs and considerably lower emissions. However, the vehicle performance is significantly affected by the battery operating conditions. Moreover, the cell life cycle, safety, and possibility of thermal runaway significantly depend on peak temperature rise and temperature uniformity of the battery. Therefore, various TMSs are created to keep batteries within ideal operating ranges. In this article, three different TMS systems—passive cabin cooling (via air), active moderate liquid circulation (via refrigerant), and active liquid circulation (via refrigerant and coolant)—are analyzed and compared with electric and hybrid electric vehicles. A second law analysis is used to examine the areas of low exergy efficiency in each system and minimize the entropy generation based on the system configuration. Moreover, TMS systems are compared on the basis of battery temperature increase and temperature uniformity. Various parametric studies are conducted to compare the TMS in different ambient and operating conditions. On the basis of the analysis, the active liquid circulation (via refrigerant and coolant) is determined to have the lowest battery temperature increase (3.9 °C in 30 min) and most cell temperature uniformity (2.5 °C median) as well as the lowest entropy generation rate (0.0121 W/K) among the compared systems. Copyright © 2012 John Wiley & Sons, Ltd.

Performance, emissions and combustion characteristics of a port-injected engine fuelled with hydrous ethanol gasoline blend (E10 - 10% of hydrous ethanol by volume in gasoline) were compared with gasoline operation. Hydrous ethanol blend produced higher power output with lean mixtures at part throttle condition. Higher flame velocity and wider flammability limits of the blend resulted in lower cycle-by-cycle variations in indicated mean effective pressure as compared to gasoline. Hydro carbon emission was also lower due to the oxygen available in the fuel (E10), which enhanced the combustion rate. Higher latent heat of evaporation of the ethanol blend and water present in it resulted in lower in-cylinder temperature, which in turn led to lesser NOx emissions. Thermal efficiency with the blend was higher in the leaner operating conditions than gasoline. Not much difference in performance, emission and combustion characteristics between neat gasoline and E10 were observed at full throttle operation. On the whole, hydrous ethanol blends can be used as a fuel with good performance and low emissions at part load condition. Copyright © 2012 John Wiley & Sons, Ltd.

The feasibility of a direct internal reforming (DIR) solid oxide fuel cell (SOFC) running on wet palm-biodiesel fuel (BDF) was demonstrated. Simultaneous production of H₂-rich syngas and electricity from BDF could be achieved. A power density of 0.32 W cm⁻² was obtained at 0.4 A cm⁻² and 800 °C under steam to carbon ratio of 3.5. Subsequent durability testing revealed that a DIR-SOFC running on wet palm-BDF exhibited a stable voltage of around 0.8 V at 0.2 A cm⁻² for more than 1 month with a degradation rate of approximately 15 % / 1000 h. The main cause of the degradation was an increase in the ohmic resistance. Copyright © 2012 John Wiley & Sons, Ltd.

Thermal issues associated with electric vehicle battery packs can significantly affect performance and life cycle. Fundamental heat transfer principles and performance characteristics of commercial lithium-ion battery are used to predict the temperature distributions in a typical battery pack under a range of discharge conditions. Various cooling strategies are implemented to examine the relationship between battery thermal behavior and design parameters. By studying the effect of cooling conditions and pack configuration on battery temperature, information is obtained as to how to maintain operating temperature by designing proper battery configuration and choosing proper cooling systems. It was found that a cooling strategy based on distributed forced convection is an efficient, cost-effective method which can provide uniform temperature and voltage distributions within the battery pack at various discharge rates. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, a detailed review is presented to discuss biomass-based hydrogen production systems and their applications. Some optimum hydrogen production and operating conditions are studied through a comprehensive sensitivity analysis on the hydrogen yield from steam biomass gasification. In addition, a hybrid system, which combines a biomass-based hydrogen production system and a solid oxide fuel cell unit is considered for performance assessment. A comparative thermodynamic study also is undertaken to investigate various operational aspects through energy and exergy efficiencies.

The results of this study show that there are various key parameters affecting the hydrogen production process and system performance. They also indicate that it is possible to increase the hydrogen yield from 70 to 107 g H₂ per kg of sawdust wood. By studying the energy and exergy efficiencies, the performance assessment shows the potential to produce hydrogen from steam biomass gasification. The study further reveals a strong potential of this system as it utilizes steam biomass gasification for hydrogen production. To evaluate the system performance, the efficiencies are calculated at particular pressures, temperatures, current densities, and fuel utilization factors. It is found that there is a strong potential in the gasification temperature range 1023–1423 K to increase energy efficiency with a hydrogen yield from 45 to 55% and the exergy efficiency with hydrogen yield from 22 to 32%, respectively, whereas the exergy efficiency of electricity production decreases from 56 to 49.4%. Hydrogen production by steam sawdust gasification appears to be an ultimate option for hydrogen production based on the parametric studies and performance assessments that were carried out through energy and exergy efficiencies. Finally, the system integration is an attractive option for better performance. Copyright © 2012 John Wiley & Sons, Ltd.

In this study, effects of increase in the coolant outlet temperature for the modular helium reactor (MHR) were studied. Therefore, the inlet temperature, flow rate and bypass flow fraction were modified to increase the outlet temperature. The simulations were carried out by using computational fluid dynamics software (ANSYS 12 FLUENT CFD code) as the steady-state condition in three dimensions with k-ε turbulence model and enhanced wall treatment. The simulated geometry was chosen as a unit cell. Four alternative operating conditions were proposed to MHR. The studied modifications substantially increased coolant outlet temperatures. In addition, they resulted in an increase of fuel centerline temperatures. In all of the cases considered, the maximum fuel temperature was obtained 1443 °C with a coolant inlet temperature of 491 °C and a coolant flow rate of 226 kg/s. Copyright © 2011 John Wiley & Sons, Ltd.

Among several liquid alternative fuels, biobutanol has shown great promise because of its very similar properties to gasoline. This review provides an overview of research activities in acetone–butanol–ethanol (ABE) fermentation over the past two and a half decades. We have addressed seven important facets of ABE fermentation, viz. biochemistry, microbial cultures, alternative substrates, solvent recovery, fermentation mode and reactor designs, mathematical modeling, and economics. Development of mutant strains having higher yield, selectivity and tolerance to inhibition, and search for cheap alternative substrates for fermentation are most important thrust areas in biobutanol production. New and efficient processes have been developed for in situ removal and recovery of the ABE solvents. Several rigorous kinetic and physiological models for fermentation have been formulated, which form useful tool for optimization of the process. These research activities have been reviewed in this paper. Finally, we have summarized studies on the economic viability of large-scale ABE fermentation processes employing various process designs, substrates, and microbial cultures. With the use of new strains, inexpensive substrates, and superior reactor designs, economic potential of ABE fermentation has been found to be highly attractive. Research efforts in science, engineering, and economics of ABE fermentation have brought biobutanol close to commercialization as liquid alternate fuel. Copyright © 2011 John Wiley & Sons, Ltd.

A methane-producing microbial electrolysis cell (MEC) is a technology to convert CO₂ into methane, using electricity as an energy source and microorganisms as the catalyst. A methane-producing MEC provides the possibility to increase the fuel yield per hectare of land area, when the CO₂ produced in biofuel production processes is converted to additional fuel methane. Besides increasing fuel yield per hectare of land area, this also results in more efficient use of land area, water, and nutrients. In this research, the performance of a methane-producing MEC was studied for 188 days in a flat-plate MEC design. Methane production rate and energy efficiency of the methane-producing MEC were investigated with time to elucidate the main bottlenecks limiting system performance. When using water as the electron donor at the anode during continuous operation, methane production rate was 0.006 m³/m³ per day at a cathode potential of −0.55 V vs. normal hydrogen electrode with a coulombic efficiency of 23.1%. External electrical energy input was 73.5 kWh/m³ methane, resulting in a voltage efficiency of 13.4%. Consequently, overall energy efficiency was 3.1%. The maximum achieved energy efficiency was obtained in a yield test and was 51.3%. Analysis of internal resistance showed that in the short term, cathode and anode losses were dominant, but with time, also pH gradient and transport losses became more important. The results obtained in this study are used to discuss the possible contribution of methane-producing MECs to increase the fuel yield per hectare of land area. Copyright © 2011 John Wiley & Sons, Ltd.

Many factors, such as mole fractions of oxygen and hydrogen, help improve the performance of proton exchange membrane fuel cells. The variation of mole fractions can be achieved by changing the operating pressure and relative humidity of the fuel cells. The changes in operating conditions are directly related to the electrochemical reaction and water generation of the fuel cells. The geometrical shape of the fuel cells also should be considered a factor in predicting performance because this affects the species' reaction speed and distribution. The current study considers four geometrical cell shapes with varied lengths and electrode and gas channel numbers. The variation in inlet pressure is considered in analyzing the current density distribution of the fuel cells and, subsequently, of liquid water generation. A serpentine gas flow channel is assumed, and its two-dimensional arrangement is considered in the different gas channel numbers and its length. Four inlet pressure variations and four geometrical shape variations also are considered in analyzing the fuel cells' current density and water generation distributions. The results obtained from this research can be utilized in identifying the fuel cells' optimal operating pressure and designing their gas channel number and arrangement. Copyright © 2011 John Wiley & Sons, Ltd.

Heat transfer fluids (HTFs) play an essential role in solar water heating systems by transferring collected energy from the collector, perhaps via a heat exchanger to the store. If the store is at a much higher temperature than the fluid, the store acts as a heat source, whereas the fluid acts as a coolant, thus reversing the collection process. This action must be avoided through good controls. Experimental performance analysis and comparison of three different types of solar collectors; a non-concentrating evacuated tube heat pipe and two concentrating single-sided and double-sided coated evacuated tube heat pipes collectors are installed and tested using Dow-corning 550® silicon oil as an HTF under the same operating in-door control conditions, and results are presented in this paper. The performance of these solar collectors was determined from the overall increase in inlet and outlet fluid temperatures, overall fluid temperature differential, energy collection rate, optical efficiencies, and thermal performances. Temperature differential, energy, and collection efficiency diagrams plotted against time were used to represent and compare the solar collectors. Finally, a comparative analysis of these solar collectors using either pressurised water or Dow-corning 550 silicon oil as HTF is presented. Copyright © 2011 John Wiley & Sons, Ltd.

A peak-shaving technology is recently proposed, which integrates peak-electricity generation, cryogenic energy storage and CO₂ capture. In such a technology, off-peak electricity is used to produce liquid nitrogen and oxygen in an air separation and liquefaction unit. At peak hours, natural gas (or alternative gases, e.g. from gasification of coal) is burned by oxygen from the air separation unit (oxy-fuel combustion) to generate electricity. CO₂ produced is captured in the form of dry ice. Liquid nitrogen produced in the air separation plant not only serves as an energy storage medium but also supplies the low-grade cold energy for CO₂ separation. In addition, waste heat from the tail gas can be used to superheat nitrogen in the expansion process to further increase the system efficiency. This article reports a systematic approach, with an aim to provide technical information for the system design. Three potential blending gases (helium, oxygen and CO₂) are considered not only for assessing thermodynamic performance but also for techno-economic analysis. The peak-shaving systems are also compared with natural gas combined cycle and an oxy–natural gas combined cycle in terms of capital cost and peak electricity production cost. Copyright © 2011 John Wiley & Sons, Ltd.

In this article, an integrated solid oxide fuel cell (SOFC) and micro gas turbine (MGT) with a multi-effect desalination (MED) system is proposed, and its comprehensive thermodynamic modelling, through energy and exergy analyses, is conducted. In addition, the effects of some design parameters on the hybrid system are investigated. The results show that fuel cell stack pressure has a significant effect on the combined system power and distilled water capacity. It also increases the SOFC-MGT energy efficiency. Moreover, the pressure of the inlet heating steam to the multieffect desalination system affects the pure water production in a positive way. An increase in the steam pressure results in a lower steam mass flow rate generated in the heat recovery steam generator. However, it increases desalination product capacity. Copyright © 2011 John Wiley & Sons, Ltd.

Structural and electrical properties of 8 yttria stabilized zirconia (YSZ) ceramics doped with varying concentrations (0.5–2.0 wt%) of Mg²⁺ ions were investigated. The result from X-ray diffraction indicates the formation of fully stabilized cubic phase. Scanning electron microscopy observation confirms the marginal decrease in grain size with addition and increase of MgO content. However, a concentration beyond x = 0.5 wt% results in segregation along the grain boundaries. Complex impedance diagrams showed an enhancement in the grain and grain boundary conductivities with doping of magnesium and are strongly dependent on its concentration. It is observed that among the compositions investigated, 8YSZMg0.5 exhibited higher conductivity at all temperatures (600–800 °C) with a maximum conductivity of 0.0345 S/cm at 800 °C. This is further confirmed by the lowest activation energy of Ea = 0.92 eV, estimated for 8YSZMg0.5 in comparison to 1–1.01 eV observed for other compositions. Comparative evaluation of these results with standard 8YSZ electrolytes reveals the possibility of the effective use of 8YSZMg0.5 as a new electrolyte material for intermediate temperature solid oxide fuel cell applications. Copyright © 2011 John Wiley & Sons, Ltd.

The injection and spray characteristics of a diesel engine with 7.4-kW rated power output for use of different karanja biodiesel blends (B10 and B20) are studied for identifications of further scope of performance improvement and emission reduction. The dynamic injection timing advanced for the biodiesel blends resulting in higher NOx emission, which increased from 2.94 g/kW-hour with base diesel to 3.40 g/kW-hour with B20. At the rated load, the dynamic injection timing advanced from 9.2 deg. crank angle before top dead centre (CA BTDC) with base diesel to 9.3 and 9.4 deg. CA BTDC for B10 and B20, respectively. The in-line injection pressure increased from 460 bar with base diesel to 480 bar with B20, and in-cylinder injection duration also increased from 9.5 deg. CA with base diesel to 10.2 deg. CA with B20. The penetration distance increased from 33.37 mm with base diesel to 34.80 mm and 34.25 mm with B10 and B20, respectively. Sauter mean diameter (SMD) increased from 11.39 µm with base diesel to 12.71 and 17.09 µm for B10 and B20, respectively, at the rated load. Air entrainment increases for the biodiesel blends, and it enhances the mixing rate of injected fuel with surrounding hot air. Vaporization time of biodiesel droplets increases because of larger SMD. However, increase in over penetration distance, large SMD and high vaporization time for the biodiesel blends would lead to deteriorated performance and emission characteristics of diesel engines. The remedial measures of spray characteristics for further performance improvement and emission reduction also are highlighted in the paper. Copyright © 2011 John Wiley & Sons, Ltd.

Cavern storage is a proven energy storage technology, capable of storing energy in the form of compressed air inside a cavern. The Huntorf plant and the Alabama plants use this technology to store electrical energy during the off-peak load hours by compressing the air inside a cavern and then using this compressed air during gas turbine operation to generate electricity during peak load demand hours. The advantage of doing this is that it increases the efficiency of gas turbine operation while meeting the grid generation and the load balance. The operation of a typical compressed air energy storage (CAES)–based gas turbine plant involves the operation of several components, including the compressor, the cavern storage, the combustor, the turbine, and so on. The dynamics of the plant as a whole depends on the performance of the individual components. The focus of this article is to develop a Simulink-based models for each of the individual components, which can then be assembled appropriately to design an entire CAES plant. As an illustration, a case study for the Huntorf CAES plant is presented with the developed models. A typical daily operation of the Huntorf plant is simulated and compared with the reported Huntorf plant data. The model accurately captures the reported dynamics of the cavern storage. In addition, the reported quantities like the compressor power consumption, the turbine power generation, and the temperature at different junctions of the CAES plant match well with the simulated results. Copyright © 2011 John Wiley & Sons, Ltd.

A thermodynamic analysis of a 500-MWe subcritical power plant using high-ash Indian coal (base plant) is carried out to determine the effects of carbon dioxide (CO₂) capture on plant energy and exergy efficiencies. An imported (South African) low-ash coal is also considered to compare the performance of the integrated plant (base plant with CO₂ capture plant). Chemical absorption technique using monoethanolamine as an absorbent is adopted in the CO₂ capture plant. The flow sheet computer program “Aspen Plus” is used for the parametric study of the CO₂ capture plant to determine the minimum energy requirement for absorbent regeneration at optimum absorber–stripper configuration. Energy and exergy analysis for the integrated plant is carried out using the power plant simulation software “Cycle-Tempo”. The study also involves determining the effects of various steam extraction techniques from the turbine cycle (intermediate-pressure–low-pressure crossover pipe) for monoethanolamine regeneration. It is found that the minimum reboiler heat duty is 373 MW_th (equivalent to 3.77 MJ of heat energy per kg of CO₂ captured), resulting in a drop of plant energy efficiency by approximately 8.3% to 11.2% points. The study reveals that the maximum energy and exergy losses occur in the reboiler and the combustor, respectively, accounting for 29% and 33% of the fuel energy and exergy. Among the various options for preprocessing steam that is extracted from turbine cycle for reboiler use, “addition of new auxiliary turbine” is found to be the best option. Copyright © 2011 John Wiley & Sons, Ltd.

Fuel cell is an energy conversion device that transforms the chemical energy of a fuel gas directly into electrical energy without direct combustion as an intermediate step. One type of fuel cell is the solid oxide fuel cell (SOFC) with the operation temperature of around 1273°K. The high operating temperature of the SOFC also provides excellent possibilities for feeding into a gas turbine (GT) to generate additional electricity. In this paper, an atmospheric SOFC and GT hybrid system have been simulated by application of Aspen Plus existing functions and unit operation modules. The study has shown that the system efficiency and voltage reduce continuously as the current density increases due to increase of Ohmic and concentration losses. However, the output power increases due to enhancement of the current density. Therefore, the system should operate at low current density if the goal is to generate power at higher efficiency. Moreover, if the goal is to produce more power, the system should operate at high current density. The simulation results indicate that the cycle can achieve high electrical generation efficiency (68.2%), which is very attractive compared to the ideal efficiency of combined cycle power plants around 50%. Moreover, a parametric analysis has been performed to assess the effects of the several operating condition variation on the system performance. Copyright © 2011 John Wiley & Sons, Ltd.

Liquefied natural gas (LNG) vaporization facilities offer an excellent opportunity of primary energy saving by means of integration with power conversion units that is still weakly exploited in actual installations. This work focuses on the evaluation of primary energy saving achievable by the integration of an LNG vaporization facility with a gas turbine and with a cogenerative combined gas-steam power plant. The fuel energy saving ratio is used as the main performance parameter to evaluate the primary energy saving derived by system integration, with respect to conventional submerged combustion vaporization. Twelve possible configurations are analyzed with steady-state calculations. Results show that a primary energy saving greater than 15% with peak values up to 27%, corresponding to 2.98 TJ/year, is achievable. The paper shows that the fuel energy saving ratio can be used as a synthetic and effective parameter to estimate the energy-saving potential of different plant configurations. Copyright © 2011 John Wiley & Sons, Ltd.

This paper presents a computational investigation of the effect of time-varying modulating conditions on a polymer electrolyte membrane fuel cell. The focus is on developing a better understanding of the fuel cell's water balance under transient conditions, which is critical in improving the fuel cell design. The study employs a macroscopic single-fuel cell-based, one-dimensional, isothermal model. The model does not rely on the non-physical assumption of the uptake curve equilibrium between the pore vapor and ionomer water in the catalyst layers. Instead, the transition between the two phases is modeled as a finite-rate equilibration process. The modulating conditions are simulated by forcing the temporal variations in fuel cell voltage. The results show that cell voltage modulations cause a departure in the cell behavior from its steady behavior, and the finite-rate equilibration between the catalyst vapor and liquid water can be a factor in determining the cell response. The cell response is also affected by the modulating frequency and amplitude. The peak cell response is observed at low frequencies. Copyright © 2011 John Wiley & Sons, Ltd.

A brief summary of the main challenges of rotor design in wind energy conversion (WEC) systems, most notably the horizontal axis wind turbine (HAWT), are presented. One of the limiting factors in HAWT design is choosing the rated capacity to maximize power output and turbine longevity. One such strategy to accomplish this goal is to widen the operational range of the WEC system by using pitch or torque control, which can be costly and subject to mechanical failure. We present a morphing airfoil concept, which passively controls airfoil pitch through elastic deformation. As a justification of the concept, a two-dimensional fluid-structure interaction routine is used to simulate the aeroelastic response of a symmetric NACA 0012 blade subjected to variable loading. The results suggest that the morphing blade can be designed to offer superior average lift to drag ratios over a specified range of attack angles by up to 4.2%, and possibly even higher. This infers that the morphing blade design can increase the power production of WEC systems while conceivably reducing cost because the passive deformation of the morphing turbine does not require active control systems that come at an added upfront and maintenance cost. Copyright © 2011 John Wiley & Sons, Ltd.

Owing to the energy scattered or absorbed by the constituents of earth's atmosphere and self-absorption in the outer layers of the sun, the spectrum of solar flux at earth's surface is different from that of a blackbody. Consequently, the second law of thermodynamics for heat engine cycles operating between thermal reservoirs needs to be revised to determine the maximum conversion efficiency. A thermodynamic model similar to those for multi-temperature plasmas and non-isothermal particle-exchange heat engines is proposed to estimate the maximum conversion efficiency of a mechanical or solid-state heat engine subject to a radiation flux not having a blackbody spectrum. An example is given to illustrate the calculation of the maximum power that can be converted from a solar flux with considerable gas absorption. Copyright © 2011 John Wiley & Sons, Ltd.

Net-zero buildings have a variety of definitions according to their boundary selection. Because these definitions are based only on the quantity of the electrical power exchange with the grid in a given period of time, those boundaries do not make much difference, because exergy and energy of electricity are close to each other. When thermal energy is exchanged between buildings and the district, the second law of thermodynamics becomes a key issue. This study discusses the importance of exergy in evaluating and rating district energy (DE) systems towards a greener status and proposes a circular exergy model that may carry the net-zero concept to net-zero energy and net-zero exergy cities. This paper presents an optimum DE system design tool based on compound CO₂ emissions metrication algorithm. Sample results indicate that net-zero energy building concepts may indeed be elevated to a city level if both energy and exergy are simultaneously taken into account in a circular exergy format. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, an optimization model was developed for identifying optimal strategies in adjusting the existing fossil fuel-based energy structure in Taiwan. In this model, minimization of the total system cost was adopted as the objective function, which was subject to a series of constraints related to energy demand, greenhouse gas (GHG) emission restriction, and energy balance. Feasibility of several potential energy structures was also evaluated through tradeoff analysis between energy system costs and GHG emission targets. Three scenarios were established under several GHG emission restriction targets and potential nuclear power expansion options. Under the three scenarios, optimal energy allocation patterns were generated. In terms of the total energy system cost, the scenario that restricted GHG emissions and nuclear power growth would result in the highest one, with an average annual increase of 4.2% over the planning horizon. Also, the results indicated that the energy supply structure would be directly influenced by energy cost and GHG emission reduction targets. Scenario 2 would lead to the greatest dependence on clean energy, which would take up 41.8% in 2025. In comparison, with no restriction on nuclear energy, it would replace several energy sources and contribute to 34.0% of the total energy consumption. Significant reduction in GHG emission could be identified under scenario 2 due to the replacement of conventional fossil fuels with clean energies. Under scenario 3, GHG emission would be significantly reduced due to the adoption of nuclear power. After 2015, energy structure in Taiwan would be slightly adjusted due to synthetic impacts of energy demand growth and GHG emission restriction. The results also indicated that further studies would be necessarily needed for evaluating impacts and feasibilities of clean energy and nuclear power utilization in Taiwan. Copyright © 2011 John Wiley & Sons, Ltd.

In the APEX (Advanced Power Extraction) studies, the conventional first solid wall facing the plasma is replaced with a fast flowing layer of a thin liquid wall. The concept of a free-surface first liquid wall concept is a revolutionary concept. The first liquid wall flows very fast and detains charged particles, and is followed by the thick liquid wall (blanket) which flows slowly and absorbs generated energy and converts it to heat. In the study, the flowing molten salt (i.e., first wall and blanket) is composed of Flibe (Li₂BeF₄) and is considered the main constituent mixed with different mole fractions (0–12%) of heavy metal salt (ThF₄ or UF₄) to increase the energy multiplication. Self-sufficient tritium breeding ratio (TBR > 1.05) was taken into account to determine the upper limit of the fraction of heavy metal salt in the mixture. Design and calculations of APEX were carried out as 3-D torus by using MCNP-4B computer code. Copyright © 2011 John Wiley & Sons, Ltd.

The efforts have been made to convert solar energy into electrical energy by eosin as photosensitizer with different sugars fructose, arabinose, D-xylose, and mannose systems in photogalvanic cell along with providing them commercial viability using lower concentrations of the solutions. The generated photopotential and photocurrent are 848.0, 679.0, 825.0, and 758.0 mV and 240.0, 240.0, 250.0, and 170.0 μA, respectively. The maximum powers are 203.52, 162.96, 206.25, and 128.86 μW, respectively. The observed conversion efficiency is 0.8415, 0.6461 0.7026, and 0.6812% and the determined fill factors are 0.34, 0.37, 0.28, and 0.27 against the absolute value 1. The developed photogalvanic cell can work for 55.0, 75.0, 85.0, and 90.0 minutes in the dark. The photogeneration electricity is proved by a proposed mechanism. Conclusively, the photogalvanic cell so developed has shown appreciable conversion and storage of solar energy. Copyright © 2011 John Wiley & Sons, Ltd.

Gas turbine cycle technologies will play a major role in future power generation, and several well-justified concepts have been developed or are the subject of major feasibility studies. In the present work, gas turbine cycles are modified with steam injection between the combustion chamber exit and the gas turbine inlet. Heat recovery steam generators, utilizing the exhaust gases, provide these cycles with the injected steam at saturated vapor. The thermodynamic characteristics of the various cycles are considered in order to establish their relative importance to future power generation markets. The irreversibility of the different composing units of the cycles and the variation of gas properties due to steam injection as well as changes in the interrelation of component performance parameters are taken into account. The isentropic temperature ratio and maximum to minimum cycle temperature ratio are varied over some ranges that slightly exceed their practically acceptable bounds in order to comprehensively investigate their effects on cycle characteristics. The performance characteristics for various modified and regeneration cycles are presented at the same values of the operating parameters.

The present modified cycles with steam injected cycles achieve an additional power output and higher efficiencies, resulting in a lower specific cost. At the chosen values of the operating parameters, the enhancement achieved in the overall efficiency for the simple, reheat (with steam injection at high and low pressures) and partial oxidation (with steam injection at high and low pressures) gas turbine cycles are of about 20–30%, 120–200%, 10–12%, 120–260% and 20%, respectively. The present modified cycles technique can be considered among the possible ways to improve the performance of gas turbine cycles-based power plants at feasible costs. This concept can be used for similar core engines. Copyright © 2011 John Wiley & Sons, Ltd.

For a solid oxide fuel cell (SOFC) and micro gas turbine (MGT) hybrid system, optimal control of load changes requires optimal dynamic scheduling of set points for the system's controllers. Thus, this paper proposes an improved iterative particle swarm optimization (PSO) algorithm to optimize the operating parameters under various loads. This method combines the iteration method and the PSO algorithm together, which can execute the discrete PSO iteratively until the control profile would converge to an optimal one. In MATLAB environment, the simulation results show that the SOFC/MGT hybrid model with the optimized parameters can effectively track the output power with high efficiency. Hence, the improved iterative PSO algorithm can be helpful for system analysis, optimization design, and real-time control of the SOFC/MGT hybrid system. Copyright © 2011 John Wiley & Sons, Ltd.

Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) is the flexible experimental accelerator-driven system in development at SCK•CEN. The MYRRHA facility, currently developed with the aid of the FP7-project ‘Central Design Team’ is conceived as a flexible irradiation facility. MYRRHA will allow fuel developments for innovative reactor systems, material developments for GEN IV systems, material developments for fusion reactors, radioisotope production for medical and industrial applications, and Si-doping. MYRRHA will also demonstrate the accelerator-driven system full concept by coupling the three components (accelerator, spallation target and subcritical reactor) at reasonable power level to allow operation feedback, scalable to an industrial demonstrator and allow the study of efficient transmutation of high-level nuclear waste. Because MYRRHA is based on the heavy liquid metal technology, lead–bismuth eutectic, it will be able to significantly contribute to the development of Lead Fast Reactor (LFR) Technology, and in critical mode, MYRRHA will play the role of the European Technology Pilot Plant in the roadmap for LFR. Copyright © 2011 John Wiley & Sons, Ltd.

Hydrogen production via thermochemical water decomposition is a potential process for direct utilization of nuclear thermal energy to increase efficiency and thereby facilitate energy savings. Thermochemical water splitting with a copper–chlorine (Cu–Cl) cycle could be linked with nuclear and renewable energy sources to decompose water into its constituents, oxygen and hydrogen, through intermediate Cu and Cl compounds. In this study, we analyze a coupling of nuclear and renewable energy sources for hydrogen production by the Cu–Cl thermochemical cycle. Nuclear and renewable energy sources are reviewed to determine the most appropriate option for the Cu–Cl cycle. An environmental impact assessment is conducted and compared with conventional methods using fossil fuels and other options. The CO₂ emissions for hydrogen production are negligibly small from renewables, 38 kg/kg H₂ from coal, 27 kg/kg H₂ from oil, and 18 kg/kg H₂ from natural gas. Cost assessment studies of hydrogen production are presented for this integrated system and suggest that the cost of hydrogen production will decrease to $2.8/kg. Copyright © 2011 John Wiley & Sons, Ltd.

Presented study discusses the development of a finite differencing (FD) thermal model for a power-split hybrid configuration employing a nickel-metal hydride battery pack. A resistance–capacitance electro-thermal model is used to couple the experimental boundary conditions (current, voltage, state of charge, and temperature) with the modeled battery resistance to capture its electro-chemical behavior and the cell exothermic reactions. Battery current, voltage, and temperature (discrete and full field) for a vehicle with a power-split hybrid configuration were collected under different standard (Federal Highway Driving Schedule and Federal Urban Dynamometer Driving Schedule (FUDS)) and artificially generated driving cycles. This manuscript analyzes the battery current and voltage in relation to vehicle speed and shows how the proposed FD model predicts the spatial and temporal temperature profiles of the power train in good agreement with the vehicle data as reported by the on-board diagnostics module. Copyright © 2011 John Wiley & Sons, Ltd.

Proton exchange membrane (PEM) fuel cells operated with hydrogen and air offer promising alternative to conventional fossil fuel sources for transport and stationary applications because of its high efficiency, low-temperature operation, high power density, fast start-up and potable power for mobile application. Power levels derivable from this class of fuel cell depend on the operating parameters. In this study, a three-dimensional numerical optimisation of the effect of operating and design parameters of PEM fuel cell performance was developed. The model computational domain includes an anode flow channel, membrane electrode assembly and a cathode flow channel. The continuity, momentum, energy and species conservation equations describing the flow and species transport of the gas mixture in the coupled gas channels and the electrodes were numerically solved using a computational fluid dynamics code. The effects of several key parameters, including channel geometries (width and depth), flow orientation and gas diffusion layer (GDL) porosity on performance and species distribution in a typical fuel cell system have been studied. Numerical results of the effect of flow rate and GDL porosity on the flow channel optimal configurations for PEM fuel cell are reported. Simulations were carried out ranging from 0.6 to 1.6 mm for channel width, 0.5 to 3.0 mm for channel depth and 0.1 to 0.7 for the GDL porosity. Results were evaluated at 0.3 V operating cell voltage of the PEM fuel cell. The optimisation results show that the optimum dimension values for channel depth and channel width are 2.0 and 1.2 mm, respectively. In addition, the results indicate that effective design of fuel gas channel in combination with the reactant species flow rate and GDL porosity enhances the performance of the fuel cell. The numerical results computed agree well with experimental data in the literature. Consequently, the results obtained provide useful information for improving the design of fuel cells. Copyright © 2011 John Wiley & Sons, Ltd.

Chromium-based metal-organic framework (MOF), MIL-101(Cr), has emerged as a potential hydrogen storage material because of its high specific surface area, tuneable pore size, and unique structure. A large portion of voids generated in MOFs remain unutilized for hydrogen storage owing to weak interactions between the walls of MOFs and H₂ molecules. The present study was aimed to reduce the unutilized voids in MIL-101 by incorporating microporous activated carbon (AC) into MIL-101 pores and thereby enhancing its volumetric hydrogen storage capacity. MIL-101 and its AC composites were synthesized under hydrothermal conditions by adding AC in different proportions in situ during the synthesis of MIL-101. The synthesized materials were characterized by various physico-chemical methods such as powder X-ray diffraction, thermogravimetric analysis (TGA), N₂-adsorption/desorption isotherms measured at 77.4 K, and transmission electron microscopy (TEM). AC@MIL-101/A prepared by the incorporation of 0.63 wt% of AC into MIL-101 shows the highest hydrogen uptake of 10.1 wt% at 77.4 K and up to 6000 kPa hydrogen pressure. Copyright © 2011 John Wiley & Sons, Ltd.

Lithium iron phosphate-carbon (LiFePO₄/multiwalled carbon nanotubes (MWCNTs)) composite cathode materials were prepared by a hydrothermal method. In this study, we used MWCNTs as conductive additive. Poly (vinylidene fluoride-co-hexafluoropropylene)-based solid polymer electrolyte (SPE) was applied. The structural and morphological performance of LiFePO₄/MWCNTs cathode materials was investigated by X-ray diffraction and scanning electron microscopy/mapping. The electrochemical properties of Li/SPE/LiFePO₄-MWCNTs coin-type polymer batteries were analyzed by cyclic voltammetry, ac impedance and galvanostatic charge/discharge tests. Li/SPE/LiFePO₄-MWCNTs polymer battery with 5 wt % MWCNTs demonstrates the highest discharge capacity and stable cyclability at room temperature. It is indicated that LiFePO₄-MWCNTs can be used as the cathode materials for lithium polymer batteries. Copyright © 2011 John Wiley & Sons, Ltd.

The effect of a cooling plate on a PEM fuel cell was studied by three-dimensional CFD modeling. The cyclic cell and the single cell were compared for the evaluation of the influence of cooling plate. The cyclic cell consisted of a single cell and a two-channel serpentine flow-field coolant, which then repeats by using a cyclic boundary on both ends. The single cell was composed of an active area of 200 cm² and a 10-channel serpentine flow field. The following sets of equations were used in the model: the conservation of electrical current, the mass conservation of gases species, the Navier–Stokes equation, the energy balance, and the water phase change model. Comparison of cyclic cell and single cell shows that the voltage of cyclic cell was reduced at high current densities because of the increased ohmic losses. This was caused by the combined effect of membrane dehydration and higher local temperature. However, the cyclic cell showed more uniform current density distribution than the single cell, and this is attributed to the use of cooling plate. Increasing the coolant flux enhanced the cell performance by reducing the ohmic loss. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, a proton exchange membrane fuel cell (PEMFC) is modeled by multilayer perceptron neural network (MLPNN), RBF neural network (RBFNN), and adaptive neuro-fuzzy inference system (ANFIS). Experimental data are obtained on the basis of the fabricated membrane-electrode assembly (MEA) responses using prepared nanocomposite and recast Nafion membranes in the PEMFC. Four parameters including cell temperature, inlet gas temperature, current density, and inorganic additive percent are used as inputs, and the cell voltage is considered as the output. The results show that there is no considerable discrepancy between the RBFNN accuracy (R = 0.99554) and the MLPNN accuracy (R = 0.99609) for the performance prediction. The required time for developing the RBFNN model is significantly lower than the MLPNN model. A variety of ANFIS structure is explored to approximate the behavior of the system. The effect of cell and inlet gas temperatures on the PEMFC performance is investigated by the ANFIS developed model. Predicted polarization and power–current behavior by the ANFIS for the MEA prepared by the recast Nafion and the nanocomposite membranes at the cell temperatures 50 °C to110°C are in high agreement with the experimental data. Predicted data by the ANFIS show that because of the property of Cs_2.5H_0.5PW₁₂O₄₀ additive for retaining water, much higher current density and power density at the same voltage are achieved for the nanocomposite membrane compared with the recast Nafion membrane in the PEMFC. Copyright © 2011 John Wiley & Sons, Ltd.

In this work are present the results obtained from the electrochemical characterization of a metal hydride type MmNi_5−XM_X impregnated with palladium, palladium–nickel and nickel nanoparticles as catalytic precursors for hydrogen absorption. The hydrogen absorption was investigated in the charge/discharge mechanism of a metal hydride via electrochemical process. The complete study involved the analysis of linear and anodic polarization, charge/discharge cycles, the application of an electrochemical model and electrochemical impedance spectroscopy to investigate the amount of hydrogen absorbed as a function of the catalytic precursors. The use of Pd nanoparticles showed the best results as catalytic precursor to absorb more hydrogen than other precursor systems. Copyright © 2011 John Wiley & Sons, Ltd.

A series of novel composite photocatalysts, NiO/Ta₂O₅, were synthesized by the solid-state reaction and successfully characterized by X-ray diffraction, Transmission electron microscopy, diffused reflectance ultraviolet and visible (DRUV-vis) spectroscopy, Photoluminescence and X-ray photoelectron spectroscopy. Powder X-ray diffraction (PXRD) pattern indicated the formation of composite material. The red shift in the absorption edges of the newly prepared composite photocatalysts were well observed from the DRUV-vis spectra. The composite photocatalyst prepared at metal ratio (1:3) showed highest result toward hydrogen production under ultraviolet and visible light irradiation in the presence of methanol as a sacrificial agent. Copyright © 2011 John Wiley & Sons, Ltd.

A 6-cell silicon-based micro direct methanol fuel cell (μDMFC) stack utilized the serial flow path design was developed. The effect of the structure of flow path on the performance of the stack was investigated using polarization characterization and electrochemical impedance analysis. Further, the voltage distribution for individual cells under different current density was discussed. The results indicated that the μDMFC stack with the serial flow path design exhibited better performance than that utilized the parallel flow path due to uniform mass transfer of methanol as a result of the use of the serial flow path. Such a μDMFC stack generates a peak output power of ca. 187 mW, corresponding to an average power density of ca. 21.7 mWcm^-2, and exhibits a steady-state power output for more than 100 h. Copyright © 2011 John Wiley & Sons, Ltd.

A large number of researchers have paid great attention to solar chimney (SC) power generating technology, but only a few have studied the chimney configuration. Taking a 10 MW SC system as an example, the physical and mathematical models illustrating the fluid flow, heat transfer and output power features of the system are established. Based on constraints such as equal chimney bottom section area or equal chimney surface area, the impact of several sizes of three different chimney configurations upon the chimney outlet air temperature and velocity, system output power and efficiency is analyzed and the influence of the height-to-diameter ratio (H/D) of the cylindrical chimney on system performance is studied as well. After a comprehensive analysis of system output power and efficiency, it is proved by the numerical simulation that the cylindrical chimney would be the best choice among the three basic configurations, whose optimum H/D value ranges from 6 to 8. Copyright © 2011 John Wiley & Sons, Ltd.

An analysis is reported of a design for a local exhaust ventilation system for the molten cuprous chloride pouring station in an industrial plant. Heat recovery from molten cuprous chloride is a key process within the copper–chlorine (Cu–Cl) cycle of thermochemical water splitting for hydrogen production. Because of particulate matter, dust, and vapors emitted by the molten salt, an effective and safe design is crucial. The design process involves calculating duct diameters to provide the desired duct air velocity through the system. The static pressure is evaluated so that the fan size can be determined. An adequate supply of makeup air must be provided to replace the air exhausted through the ventilation system. The economics of the ventilation system and ways to protect employee health, as well as minimize the costs associated with exhaust ventilation, are also described. Copyright © 2011 John Wiley & Sons, Ltd.

A high performance five-layered anode supported solid oxide fuel cell (SOFC) is developed by low-cost tape casting, co-sintering, and screen printing techniques. The cell is composed of NiO/scandium stabilized zirconia (ScSZ) anode support, NiO/ScSZ anode functional layer (AFL), ScSZ electrolyte, lanthanum strontium ferrite (LSF)/ScSZ cathode functional layer, and LSF cathode current collecting layer. The effects of fabrication parameters on the cell performance are investigated and optimized, including co-sintering temperature, thickness of the anode support, and AFL. The effects of GDC ion conducting phase impregnated into both electrodes also are investigated. The microstructure of the cell is observed using a scanning electron microscope, and the cell performances at various operation temperatures are evaluated by a fuel cell test station. The final cell produces 1.34 W·cm^-2 maximum power density at an operation temperature of 700 °C. The high performance is attributed to optimized cell structure as well as increase in the oxide ion conductivity and three-phase boundaries of both anode and cathode layers by nano ion conductor infiltration. Copyright © 2011 John Wiley & Sons, Ltd.

Ball-milled hydrogenated graphite-iron materials have attracted interest as possible hydrogen storage media because of theoretically estimated hydrogen capacities of about 10 wt%. However, such a value needs to be experimentally verified. In this work, graphite-0.5 wt% Fe was milled under 3 bar hydrogen in a tungsten carbide milling pot. The effect of iron on the microstructure and hydrogen storage properties of milled graphite was investigated by thermal gravimetric analysis–mass spectrometry, X-ray diffraction, and transmission electron microscopy. When a 10-hour milled graphite with 0.5 wt% Fe sample was heated under argon to 990 °C, 9.6 wt% of hydrogen was released, which is almost double than that for a graphite sample with no iron (5.5 wt% hydrogen). The addition of iron also was found to reduce the onset temperature of hydrogen desorption by 50 to 350 °C. However, for a longer milling time of 40 hours, the amount of hydrogen desorbed for graphite-0.5 wt% Fe decreased, and methane also was detected. The results suggest that iron carbide produced during milling plays a catalytic role, increasing the hydrogen storage capacity and lowering the onset temperature of hydrogen desorption. Copyright © 2011 John Wiley & Sons, Ltd.

A three-effect heat pipe (heat pipe heating, heat pipe cooling and heat pipe heat recovery) adsorption refrigeration system using compound adsorbent (calcium chloride and activated carbon) was designed. The dynamic characteristics of mass and heat pipe heat recovery were studied. The results show that mass recovery and heat pipe heat recovery can improve (specific cooling power) SCP and (coefficient of performance) COP greatly. The averaged SCP of the cycle with mass recovery and the cycle without mass recovery is 502.9 W/kg and 436.7 W/kg at about 30 °C of cooling water temperature and −15 °C of evaporating temperature. The corresponding COP is 0.27 and 0.24 respectively. Copyright © 2011 John Wiley & Sons, Ltd.

Artificial neural networks (ANN) were proposed as a multivariate experimental design tool for monitoring a photo-Fenton treatment of wastewaters containing a synthetic mixture of pesticides. ANN and Nelder-Mead simplex methods were used to find out the optimum operating parameters of a photo-Fenton pilot plant. ANN was developed to predict the most important operating parameters (e.g., the total organic carbon and the initial mineralization kinetic rate constants of the reactions), which determine the photo-catalytic degradation efficiency in photo-Fenton processes. Experimental measurements of temperature, pH, hydrogen peroxide (H₂O₂) consumption, initial concentration of Fe²⁺, and the AE were used as input data for the ANN learning. A feed-forward with one hidden layer, a Levenberg–Marquardt learning algorithm, a hyperbolic tangent sigmoidal transfer function and a linear transfer function were used to develop the ANN model. The best fitting of the training database was obtained with an ANN architecture constituted by seven neurons in the hidden layer. The simulated results were validated with experimental measurements, showing an acceptable agreement (R² > 0.99). The ANN was subsequently coupled with a Nelder–Mead simplex method to obtain the optimum operating parameters of the photo-Fenton pilot plant. The H₂O₂ consumption was used as key variable for evaluating the optimization procedure. Errors less than 1% between simulated and experimental data were found. The obtained results showed that the use of ANN provides an excellent predictive performance tool with the additional capability to assess the influence of each operating parameter on the removal process of water pollutants. Copyright © 2011 John Wiley & Sons, Ltd.

Homogeneous charge compression ignition (HCCI) combustion in diesel engines offers the potential of simultaneous low NOx and soot emissions. However, this is normally accompanied by high hydrocarbon (HC) levels in the exhaust and an early combustion phasing before the top-dead-center (TDC) that may drain out substantial amounts of fuel energy from the engine cycle. Exhaust gas recirculation is usually applied to delay the onset of combustion, thereby shifting the phasing of the heat release close to the TDC. Although the retarded phasing improves the engine energy efficiency, a significant increase in HC and carbon monoxide emissions will deteriorate the combustion efficiency. Therefore, an inherent trade-off exists between the combustion phasing and the combustion efficiency that needs to be minimized for improved energy efficiency.

In this work, both theoretical and experimental studies have been carried out to evaluate the combustion efficiency-phasing (CEP) trade-off. Engine tests have been conducted to analyze the losses in combustion (burning) and phasing efficiencies, and along with theoretical analyses, the CEP trade-off has been evaluated in terms of a ‘coefficient of combustion inefficiency’ (CCI). The CCI quantitatively correlates the losses in combustion and phasing efficiencies and provides a reference for improving the combustion phasing of the HCCI operation vis-à-vis the combustibles in the exhaust. The focus of this research is to carry out a quantitative analysis of the energy efficiency of HCCI cycles. Copyright © 2011 John Wiley & Sons, Ltd.

Here, we show how to distribute multiple layers of insulation along a nonisothermal enclosure so that the total heat loss is minimal. The types and total amounts of insulation materials are fixed. Variables are the thicknesses of the insulation layers, their relative amounts, the temperature of the insulated surface, and the cross-sectional area of the enclosure. We show that, first, the structure of the multi-layer insulation must be such that the thicknesses of all the layers vary in the same way in the longitudinal direction x. Second, the x dependence of the enclosure cross-sectional area has a significant effect on the heat loss reduction associated with using the distributed insulation design. Greater reductions in heat loss are obtained when the enclosure is tapered such that it is narrower in the direction of the warm end. Third, the x dependence of the temperature distribution along the insulated wall has a significant effect on the reduction in heat loss through reduction in heat loss through the multi-layer insulation. Greater reductions are obtained when the wall temperature distribution is more convex. Even greater reductions in heat loss are possible when the three design features summarized previously are implemented simultaneously. Copyright © 2011 John Wiley & Sons, Ltd.

The objective of this study is to demonstrate the significant improvement in the photoelectrochemical (PEC) hydrogen generation by a photoanode owing to the increased surface area of the substrate. In this work, multilayered tungsten oxide (WO₃) films have been successfully synthesized onto the large-area sheet (9 × 9cm²) and mesh (1 × 20cm²) -type stainless steel (SS) substrates using screen printing and brush painting methods, respectively. All the WO₃ films are porous and nanocrystalline (30–80 nm) in nature with a monoclinic crystal structure as revealed from X-ray diffraction and scanning electron microscopy studies. The PEC water splitting study is performed under simulated 1 SUN illumination (AM1.5 G) in a typical two-electrode cell configuration with WO₃ photoanode and Pt wire immersed in 0.5 M H₂SO₄ electrolyte. The photocurrent as well as hydrogen generation rate for WO₃ photoanodes coated on the plane SS sheet substrate is relatively low and showed minimal change with increasing film thickness. On the other hand, the photocurrent as well as the hydrogen generation is enhanced by a 3–4 fold degree for the WO₃ photoanodes coated on SS mesh. We attribute such efficient water splitting to the increment in the filling factor of the WO₃ material due to the large effective surface area of the SS mesh as compared to the SS sheet substrate. Copyright © 2011 John Wiley & Sons, Ltd.

The plasma focus is a promising small-scale alternative to the huge Tokamak project in the development of nuclear fusion energy. Its strength lies in the characteristic that the plasma condition is the same whether the plasma focus is a small sub-kilojoule machine or a large one with thousands of kilojoules of stored energy and the related constancy of the dynamic resistance. Yet, this strength turns out to result in a weakness. The observed neutron ‘saturation’ is more correctly stated as a ‘scaling deterioration’ effect. This critical weakness is due to the same constancy of the plasma condition intimately related to a constancy of the dynamic resistance. The understanding of this situation points to a new class of plasma focus devices to overcome the ‘saturation’ of the electric current. Plasma focus technology has to move to ultra high voltage technology and take advantage of circuit manipulation techniques in order to move into a new era of high performance. This paper examines fundamental scaling properties of the plasma focus including speeds, temperatures, dimensions and times. It links up these basic scaling characteristics with the crucial ideas of the inherent yield scaling deterioration, thus providing a clear understanding of its overall performance characteristics, paving the way for future exploitation. Copyright © 2011 John Wiley & Sons, Ltd.

This paper analyses the transportation and delivery features of hydrogen as energy market evolves and approaches a fully functional Hydrogen economy. Initially physical aspects have been assessed that affect the flow of hydrogen through the existing pipeline infrastructure. Line pack and compressors are the only identified problems that need to be addressed. This is followed by an investigation into the mixing of hydrogen with natural gas gradually. It was revealed that a mix of up to 17% by volume does not have any significant effect, however higher concentration of hydrogen leads to a changeover of high-pressure grid pipelines as well as the end-user applications. It is suggested that initially hydrogen can be introduced in the distribution system, while emphasizing towards developing means for high-pressure transportation of hydrogen fuel gas. Government policies towards encouraging use of hydrogen in an evolving market is important for widespread and early assimilation in energy mix. Renewable sources of energy are recommended for distributed generation of hydrogen along the pipeline network. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, novel approaches for wind speed data generation using Mycielski algorithm are developed and presented. To show the accuracy of developed approaches, we used three-year collected wind speed data belonging to deliberately selected two different regions of Turkey (Izmir and Kayseri) to generate artificial wind speed data. The data belonging to the first two years are used for training, whereas the remaining one-year data are used for testing and accuracy comparison purposes. The concept of distinct synthetic data production with correlation-wise and distribution-wise similar statistical properties constitutes the main idea of the proposed methods for a successful artificial wind speed generation. Generated data are compared with test data for both regions in the sense of basic statistics, Weibull distribution parameters, transition probabilities, spectral densities, and autocorrelation functions; and are also compared with the data generated by the classical first-order Markov chains method. Results indicate that the accuracy and realistic behavior of the proposed method is superior to the classical method in the literature. Comparisons and results are discussed in detail. Copyright © 2011 John Wiley & Sons, Ltd.

TiCl₃ has been considered as the best catalyst for the hydrogen desorption/re-absorption of NaAlH₄ in terms of kinetic enhancement. However, the formation of NaCl as a by-product leads to the decrease in the reversible hydrogen capacity of NaAlH₄. In this work, TiO₂ and metallic Ti were selected as catalysts for the reaction to avoid the formation of the by-product. The comparison of the catalytic activity of Ti, TiCl₃, TiO₂ and Ti(OBu)₄ on the hydrogen desorption/absorption NaAlH₄ were carried out. It was found that TiO₂ doped NaAlH₄ exhibits similar behavior as TiCl₃ doped NaAlH₄ with the reversible hydrogen capacity about 3.8 wt% (H/M). In addition, TiO₂ doped NaAlH₄ exhibits the superior hydrogen re-absorption rate to the one doped with TiCl₃. That may be due to the Ti³⁺ defect sites on the surface of TiO₂ would facilitate the hydrogen dissociation. Moreover, high surface area of TiO₂ prevents the segregation and the morphological change of the desorbed substances (NaH and Al). This benefits to the mass transfer into the hydride system. However, doping with TiO₂ also produces sodium oxide and hydroxide as by-products. Unexpectedly, metallic Ti doped NaAlH₄ shows the lowest hydrogen desorption/re-absorption among the tested samples. Its hydrogen reversible capacity is around 1 wt% (H/M). The formation of TiH_x (1 < x < 2) was detected in the sample after the hydrogen desorption/reabsorption. Copyright © 2011 John Wiley & Sons, Ltd.

The system performance of a ground source heat pump (HP) system is determined by the HP characteristics itself and by the thermal interaction between the ground and its borehole heat exchanger (BHE). BHE performance is strongly influenced by the thermal properties of the ground formation, grouting material, and BHE type. Experimental investigations on different BHE types and grouting materials were carried out in Belgium. Its performances were investigated with in situ thermal response tests to determine the thermal conductivity (λ) and borehole resistance (R_b). The line-source method was used to analyze the results, and the tests showed the viability of the method. The main goal was to determine the thermal borehole resistance of BHEs, including the effect of the grouting material. The ground thermal conductivity was measured as 2.21 W m⁻¹ K⁻¹, a high value for the low fraction of water-saturated sand and the high clay content at the test field. The borehole resistance for a standard coaxial tube with cement–bentonite grouting varied from 0.344 to 0.162 K W⁻¹ m for the double U-tube with cement–bentonite mixture (52% reduction). Grouting material based on purely a cement–bentonite mixture results in a high thermal borehole resistance. Addition of sand to the mixture leads to a better performance. The use of thermally enhanced grouts did not improve the performance significantly in comparison with only a low-cost grouting material as sand. Potential future applications are possible in our country using a mobile testing device, such as characteristics, standardization, quality control, and certification for drilling companies and ground source HP applications, and in situ research for larger systems. Copyright © 2011 John Wiley & Sons, Ltd.

Thermodynamic equilibrium of ethanol steam reforming is studied using the Gibbs free energy minimization method. The reaction paths of ethanol steam reforming are simulated using Chem-CAD software. Appropriate optimization of reactants ratio and reaction conditions is performed, to achieve the composition of ethanol steam reforming products, which will be favorable as an internal combustion engine (ICE) fuel. The effects of process variables, such as temperature and water : ethanol molar ratio are discussed. Numerical investigations are conducted to analyze energy performance of steam reforming of ethanol for ICE. Realization of ethanol steam reforming at high temperature leads to an increase in efficiency of the process. The optimal conditions are obtained as follows: 1100 K, water : ethanol molar ratio of 1.2. Copyright © 2011 John Wiley & Sons, Ltd.

Numerous processes exist or are proposed for the energetic conversion of biomass. The use of thermal plasma is proposed in the frame of the GALACSY project for the conversion of bio-oil to hydrogen and carbon monoxide. For this purpose, an experimental apparatus has been built. The feasibility of this conversion at very high temperature, as encountered in thermal plasma, is examined both experimentally and numerically. This zero dimensional study tends to show that a high temperature (around 2500 K or above) is needed to ensure a high yield of hydrogen (about 50 mol%) and about 95 mol% of CO + H₂. Predicted CO + H₂ yield and CO/H₂ ratio are consistent with measurements. It is also expected that the formation of particles and tars is hampered. Thermodynamic data of selected bio-oil components are provided in the CHEMKIN–NASA format. Copyright © 2011 John Wiley & Sons, Ltd.

This paper provides a theoretical study of the effects of ambient conditions on the thermodynamic performance of a hybrid combined-nuclear cycle power plant. The operational parameters investigated are based on the first and second laws of thermodynamics, which include the ambient air temperature and ambient relative humidity (Φ). The results obtained for the gas turbine model are shown to agree very well with operational data from the Al-Zour Emergency power plant in Kuwait. The ambient temperature was studied within the range of 0–55 °C. The analysis shows that the ambient air temperature has strong effects on plant performance and that operating the system at a high temperature will degrade the performance. Power output is reduced when the temperature is above the standard ambient temperature of 15 °C, and this loss rate is about 17% at 55 °C. The effect of ambient relative humidity (Φ) becomes significant only at higher temperatures. The ambient temperature has a large effect on the exergy destruction of the heat recovery steam generator exhaust, but it has little effect on other components of the plant. The analysis also indicates that reducing the temperature from 55 to 15 °C could help decrease the total exergy destruction of the plant by only 2%. Copyright © 2011 John Wiley & Sons, Ltd.

The objective of this paper is to demonstrate the advantages of using a combined heating and power (CHP) system operating at full load to satisfy a fraction of the facility electric load, that is, a base load. In addition, the effect of using thermal storage during the CHP system operation (CHP-TS) is evaluated. A small office building and a restaurant with the same floor area, in Chicago, IL, and Hartford, CT, were used to evaluate the base-loaded CHP and CHP-TS operation based on operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDEs). Results indicate that, in general, the use of thermal storage is beneficial for the CHP system operation because it reduces cost, PEC, and CDEs compared with a CHP with no thermal storage. The CHP and CHP-TS operation is more beneficial for a restaurant than for a small office building for the evaluated cities, which clearly indicates the effect of the thermal load on the CHP system performance. Copyright © 2011 John Wiley & Sons, Ltd.

A new and very promising application of auto-thermal reactors is the coupling of endothermic and exothermic reactions where the product of the endothermic reaction is the desired one. Therefore, in this work, a reactor in which oxidative coupling of methane (OCM) and steam re-forming of methane (SRM) reactions take place simultaneously was modeled. The results were obtained in a wide range of different conditions such as inlet feed, inlet temperature, portions of OCM and SRM catalysts, and inlet velocity. In selection of the catalysts, more attention was drawn to prevent re-forming of OCM products. The main parameters of each reaction under different conditions such as conversion of the feed components, products selectivity and yield, temperature in the length of reactor, and component's concentration in the reactor were considered in course of this study. The results revealed that simultaneous OCM and SRM reactions in one reactor will tend to be auto-thermal, and the waste of energy will be reduced. The results also show that complete conversion of water and majority of methane and oxygen will decrease the amount of unwanted products at the reactor's discharge–a constraint that exists in single reactors of each reaction specially OCM. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, CFD modelling of confined and unconfined turbulent jet flames were carried out. Investigations were performed for different air : fuel ratios including stoichiometric conditions. Confined and unconfined combustions of hydrogen were investigated for different power inputs. As the combustion chamber is cylindrical and axisymmetrical, CFD modelling was made two dimensional and axisymmetrical.

As a result of the modelling, temperature distributions, velocity distributions and gas concentrations including NO_x emissions were obtained. It is shown that maximum temperature and maximum NO_x emissions occur at the confined condition of hydrogen combustion. It is also shown that the value of NO_x emissions in low-temperature zones are less than the value of NO_x emissions in high-temperature zones in all combustion conditions. Copyright © 2011 John Wiley & Sons, Ltd.

Use of thermoelectric subcooler is one of the techniques to improve the performance of transcritical CO₂ cycle. Thermodynamic analyses and optimizations of transcritical CO₂ refrigeration cycle with thermoelectric subcooler are presented in this paper. Further, the effects of various operating parameters on cycle performances are studied. It is possible to optimize current supply, discharge pressure, and CO₂ subcooling simultaneously based on maximum cooling COP for thermoelectrically enhanced transcritical CO₂ refrigeration cycle to get best performance. Results show that thermoelectric current supply, COP improvement, and discharge pressure reduction increase with increase in cycle temperature lift, with maximum values of 11 A, 25.6%, and 15.4%, respectively, for studied ranges. Use of thermoelectric subcooler in CO₂ refrigeration system not only improves the cooling COP, also reduces the system high-side pressure, compressor pressure ratio, and compressor discharge temperature, and enhances the volumetric cooling capacity. Component-wise irreversibility distribution shows similar trend with basic CO₂ cycle, although values are lower leading to higher second law efficiency. Cooling capacity may be enhanced by increasing the current supply for the same thermoelectric configuration with penalty of COP. Study reveals that thermoelectrically enhanced CO₂ refrigeration cycle yields significant performance improvement especially for higher-cycle temperature lift. Copyright © 2011 John Wiley & Sons, Ltd.

Three porous organic polymers (POPs) containing carborane were successfully synthesized as adsorbents for gas storage applications, particularly for hydrogen storage. The current physisorption-based materials generally suffer from low isosteric heat of adsorption toward hydrogen molecules. To enhance the interaction between the adsorbent hydrogen, we prepared a series of POPs containing highly electron-deficient carborane components. These polymers have narrow pore size distribution with majority of the dimensions falling in the 0.7- to 1.0-nm range. High Brunauer-Emmett-Teller (BET)-specific surface areas up to 1023 m²/g were obtained. Hydrogen adsorption capacities at 77, 195, and 298 K were measured using a Sievert isotherm apparatus. The initial heat of adsorption for the carborane -containing polymers was calculated to be 8–10 kJ/mol. Copyright © 2011 John Wiley & Sons, Ltd.

Absorption refrigeration cycles are alternatives to conventional vapor-compression cycles in which the energy required for refrigeration is provided by heat instead of mechanical work. In this paper, a novel refrigeration cycle utilizing the immiscible liquid-phase separation behavior is simulated and analyzed using Aspen simulator. The two conjugate liquids adopted in this work are triethylamine (solute) and water (solvent). This binary system has a low critical solution temperature of 18 °C. The thermophysical properties of the binary mixture are generated using the universal functional activity coefficient (UNIFAC) and the nonrandom two-liquid (NRTL) models. The phase splitting phenomenon at the generator temperature is predicted by both models. However, in comparison with the available experimental data for the same binary mixture, NRTL model gives better predictions for the flow rates and compositions of the material streams. Heat duties of the evaporator, absorber, and generator and the power consumption of the solution pump have been calculated using UNIFAC and NRTL models. The cycle COP that plays a major role in determining the cycle economical viability has been predicted for different operating conditions using the two models. Simulation results show that, for a waste heat reservoir at 60 °C and using NRTL model, the COP is about 2.0. Second law analysis conducted for all cycle components of the cycle shows that about 42% of the total exergy destructed occurs in the generator. Finally, the liquid-phase separation refrigeration cycle is predicted to be a promising cycle in the near future because of hardware and energy savings. Copyright © 2011 John Wiley & Sons, Ltd.

The fabrication of electrodes use in proton exchange membrane fuel cells (PEMFCs) by Pt sputter deposition has great potential to increase Pt utilization and reduce Pt loading without loss of cell performance. A radio frequency (RF) magnetron sputter deposition process (RF power = 100 W and argon pressure = 10⁻³ Torr) was adopted to prepare Pt catalyst layers of PEMFC electrodes. The effects of cathode Pt and Nafion loadings on membrane electrode assembly (MEA)/cell performance were investigated using cell polarization, cyclic voltammetry, AC impedance, and microstructure analysis. Among the tested MEAs with various cathode Pt loadings (0.02–0.4 mg cm⁻²), the one with 0.1 mg-Pt cm⁻² (grain size = 3.90 nm, mainly Pt(111)) exhibited the best cell performance (320 and 285 mW cm⁻² at 0.44 and 0.60 V, respectively), which was similar to or better than those of some commercial nonsputtered/sputtered electrodes with the same or higher Pt loadings. The electrode Pt utilization efficiency increased as the Pt loading decreased. A Pt loading of greater than or lower than 0.1 mg cm⁻² yielded a lower electrode electrochemical active surface (EAS) area but a higher charge transfer and diffusion resistance. Nafion impregnation (0.1 to 0.3 mg cm⁻²) into the sputtered Pt layer (Pt = 0.1 mg cm⁻²) noticeably increased the EAS area, consistent with the decrease of the capacitance of the electrode double layer, but did not improve MEA/cell performance, mainly because of the increase in the kinetic and mass transfer resistances associated with oxygen reduction on the cathode. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, simultaneous production of ultrapure hydrogen and gasoline via a novel catalytic fixed-bed double-membrane reactor with co-current flow was investigated, mathematically. The thermally coupled double-membrane reactor (TCDMR) consists of two Pd/Ag membranes, one for separation of pure hydrogen from endothermic side and another one for permeation of hydrogen from endothermic into exothermic side. Ammonia decomposition reaction is coupled with the Fischer–Tropsch Synthesis (FTS) reaction to improve the heat transfer between endothermic and exothermic sides. Some of the produced hydrogen via ammonia decomposition reaction is utilized in FTS reaction, and the other is extracted and stored. A steady-state heterogeneous model of the two fixed beds predicts the performance of this novel configuration. The achieved results of this simulation have been compared with the results of the conventional fixed-bed reactor (CR) at identical process conditions. The simulation results show 67.34% hydrogen production in the permeation side and 32.66% hydrogen utilization in the exothermic side for compensates of hydrogen lack in the FTS reaction through the TCDMR configuration. Moreover, the gasoline yield in TCDMR increases about 18.42% because of a favorable profile of temperature along the TCDMR in comparison with the one in CR. Therefore, this approach utilizes and produces large amounts of pure hydrogen and decreases environmental impacts owing to ammonia emission. Copyright © 2011 John Wiley & Sons, Ltd.

The present study demonstrates a possible configuration of a 200 MW chemical looping combustion (CLC) system with methane (CH₄) as fuel. Iron oxide-based oxygen carriers were used because of its non-toxic nature, low-cost, and wide availability. We analyzed the effects of different variables on the design of the system. For the air reactor (oxidizer), bed mass is independent, and for the fuel reactor (reducer), it decreases with increase in the conversion difference between the air and fuel reactors. On the other hand, the pressure drop in the air reactor is unchanged, whereas for the fuel reactor, it decreases with the same increase of conversion difference between air and fuel reactors. Also, entrained solid mass flow rate from the air to fuel reactor shows a decreasing trend. Bed mass, bed height, pressure drop, and residence time of the bed materials decrease with increase in the conversion rates in the air and fuel reactors. Residence time of bed material in the air and fuel reactor reduces with increase in the temperature of the air reactor. Copyright © 2011 John Wiley & Sons, Ltd.

The iron hexagonal mesoporous silica (Fe-HMS)-n photocatalyst, where n is the molar ratio Si/Fe in the precursor gel (=50), has been successfully synthesized at an ambient temperature using hexadecylamine as template agent. The material was characterized by X-ray diffraction, N₂ adsorption measurement Brunauer, Emmet, Taller (BET) and Barrett–Joyner–Halenda theory, UV–Vis spectroscopy, high-resolution transmission electron microscopy and electron spin resonance. The electrical conductivity follows an Arrhenius-type law with activation energy of 0.04 eV. Fe₂O₃ is uniformly dispersed on the HMS surface; it works synergistically to make Fe-HMS photoelectrochemically active. The flat band potential (−0.75 V_SCE) is higher than the potential of hydrogen generation (−0.50 V_SCE at pH~7), and the material shows high efficiency for hydrogen evolution upon visible light. The photoactivity in Na₂SO₄ and Na₂SO₃ (0.1 M) solution was found to be 136 and 175 µmol g^-1 min^-1, respectively under full light (29 mW cm^-2). The tendency to saturation, observed only in SO₃^2- electrolyte, is ascribed to the competitive reduction of the end product, namely S₂O₆^2- with the water reduction. Copyright © 2011 John Wiley & Sons, Ltd.

Nanocrystalline Ni ferrite thin film was prepared by electrospray deposition technique and characterized by different analytical techniques at different annealing temperatures. All these films were studied by photovoltaic-assisted water electrolysis system for solar to hydrogen production efficiency measurement. Highly dense and uniform surface morphology was observed in as-deposited film, which changed into agglomerated nanocrystalline grains of irregular size and shape with change in annealing temperature. The X-ray photoelectron spectroscopy study showed that the as-deposited film was a mixture of an oxyhydroxide form of iron and an Ni₂O₃ form of nickel, whereas it changed into ferrite phase with change in annealing temperature. The as-deposited film was observed to be of amorphous phase, which changed to crystalline cubic spinel structure with change in annealing temperature. The solar to hydrogen production efficiency was found to increase in a film with an increase in annealing temperature. The film annealed at 500°C showed a high solar to hydrogen production efficiency (8.29%) with constant performance of up to initial 500 h. Thereafter, the performance slowly declined by 11% when up to 1000 h. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, a new design for the flow channels is presented, and a parametric study of the proton exchange membrane (PEM) fuel cell is conducted in order to investigate the effect of the new flow channels, as well as different operating parameters, on the efficiency and energy output of the cell. Design parameters are selected based on studies presented in the literature to build a physical and practical model. With the new design of the flow channels, it is noticed that the cell efficiency increases from 33.8% to 47.7% if the temperature of the cell is increased. The power output of the cell increases from 2.6 to 282.5 W when the cell temperature and the current density are increased. Moreover, decrease in the efficiency of the cell ranges from 45.5% to 28.4% with the increase in the current density and membrane thickness. Based on the analytical model, design parameters were selected to manufacture a fuel cell that has a power output of 175 W and an efficiency of 35% running at 353 K and 3 bar, with an effective membrane area of 450 cm². Experiments are conducted to investigate the effect of newly designed flow channels on pressure distribution. It is found that when hydrogen is supplied from both inlets, pressure across the channels become symmetric and, therefore increasing the power output. This study reveals that, with the proper choice of design parameters, a PEM fuel cell is an attractive economical, efficient, and environmental solution when compared with conventional systems of power generation such as gas turbines. Copyright © 2011 John Wiley & Sons, Ltd.

Composite membranes based on polytetrafluoroethylene (PTFE) and silicon dioxide (PTFE/SiO₂ × HPO₃) are fabricated to act as a fuel cell membrane for operation at temperatures from 120 to 200°C. A porous PTFE membrane is used as the membrane supporting structure and SiO₂ × HPO₃ sol as the proton conductor. SEM and EDX show that the sol clusters are connected together and adhered to the PTFE polymer. This structure completely fills the pores of the PTFE and minimises the gas cross-over. The PTFE/SiO₂ × HPO₃ membrane has a high proton conductivity, up to 0.14 S cm⁻¹ at a relative humidity lower than 0.5%. The PTFE/SiO₂ × HPO₃ composite membrane gives the modest performance when it is tested in a hydrogen fuel cell although it is a potential material for the intermediate-temperature proton-conducting membrane fuel cell. Copyright © 2011 John Wiley & Sons, Ltd.

Maintaining a constant voltage in polymer electrolyte membrane fuel cells (PEMFCs) has always attracted the attention of many researchers, and many articles have been published on this issue. Furthermore, water management in PEMFC has become an important challenge because it can improve cell efficiency and lifetime. This paper will develop a one-dimensional dynamic model for a single PEMFC, which correlates changes in the cell voltage to changes in the cell current density and humidification rate. Subsequently, a recurrent neural network controller based on the approximation of nonlinear autoregressive moving average model is proposed. The controller manipulates the anode and the cathode water mole fractions in order to fix cell voltage and preserve cell water content within a satisfactory interval regardless of the varying cell current. The model and the controller are simulated in matlab/Simulink (Mathworks Inc., Natick, MA) software, and the results are compared with a PID controller from different viewpoints such as current disturbance and plant parameter variation. Copyright © 2011 John Wiley & Sons, Ltd.

The present work deals with the measurement and performance of a gamma Stirling engine of 500 W of mechanical shaft power and 600 rpm of maximal revolutions per minute. Series of measurements concerning the pressure distribution, temperature evolution, and brake power were performed. The study of the different functioning parameters such as initial charge pressure, engine velocity, cooling water flowrate, and temperature gradient (between the sources of heat) has been analyzed. The engine brake power increases with the initial charge pressure, with the cooling water flow, and with the engine revolutions per minute. The working fluid temperature measurements have been recorded in different locations symmetrically along both regenerator sides. The recorded temperature in regenerator side one is about 252 °C and about 174 °C in the opposite side (side two). It shows an asymmetric temperature distribution in the Stirling engine regenerator; consequently, heat transfer inside this porous medium is deteriorated. Copyright © 2011 John Wiley & Sons, Ltd.

A regional energy system consists of diverse forms of energy. Energy-related issues such as utilization of renewable energy and reduction of greenhouse gas (GHG) emission are confronting decision makers. Meanwhile, various uncertainties and dynamics of the energy system are posing difficulties for the energy system planning, especially for those under multiple stages. In this study, an interval multi-stage stochastic programming regional energy systems planning model (IMSP-REM) was developed to support regional energy systems management and GHG control under uncertainty. The IMSP-REM is a hybrid methodology of inexact optimization and multi-stage stochastic programming. Not only can it handle uncertainties presented as intervals and probability density functions but also reflect dynamics of system conditions over multiple planning stages. The developed IMSP-REM was applied to a hypothetical regional energy system. The results indicate that the IMSP-REM can effectively reflect issues of GHG reduction and renewable energy utilization within an energy system planning framework. In addition, the model has advantages in incorporating multiple uncertainties and dynamics within energy management systems. Copyright © 2011 John Wiley & Sons, Ltd.

Investigations on using artificial neural networks to predict the performance of single proton exchange membrane fuel cell has been carried out. Two sets of polarization data obtained at different temperatures and flow rates are used to create and simulate the network. Cell temperature, humidification temperatures, H₂/air flow rates and current density have been used as inputs, and voltage is used as observed (output) value to train and simulate the network. This nonlinear data are batch trained, and artificial neural network has been constructed using feed forward backpropagation algorithm. Performance of the training has been improved by increasing the number of neurons to reduce the error. Simulation results are in agreement with experimental data, and the corresponding networks are used to predict the polarization behavior for unknown inputs. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, we have studied different strategies for managing voltage fluctuations in distribution networks originating from decentralized electricity generation systems (DEGS) or increased loads, which are highly important issues in the smart grid context. A starting point for system design when increasing load or local power production could be to limit the voltage fluctuations to ±5% from nominal voltage. Strategies to regulate voltage include cable improvement, transformer management, Demand side management, storage, and line interconnection. We present a mathematical model applicable for both a static and dynamic analysis to quantify effects from these measures, though the best solution will depend on local conditions and needs to be determined case by case. Combining several voltage control options simultaneously may lead to further positive effects. Strategies when doubling the load and increasing DEGS production to twice the electricity demand were analyzed here in detail. It also needs to be pointed out that other factors related to power quality besides voltage may need consideration when large amounts of DEGS are integrated to distribution networks. Copyright © 2011 John Wiley & Sons, Ltd.

The numerical simulation and experimental validation of a compound parabolic concentrator (CPC) are presented. The solar device had an aperture area of 1.33 m², a real concentration ratio of 3.5, an acceptance half angle of 15°, and a carbon steel (or aluminum) tubular receiver with an outer diameter of 0.0603 m and coated with a commercial selective surface. Experimental tests were performed using water as working fluid at solar noon; the inlet temperatures used varied from 30 °C to 70 °C and the mass flow rates from 0.05 kg/s to 0.25 kg/s. A comparison of the experimental results with the numerical model developed was carried out. The results of the thermal efficiency, outlet temperature, and pressure drop were compared and found to be in close agreement with the experimental data. Therefore, the model is a reliable tool for the design and optimization of compound parabolic concentrators. Because the numerical model is based on the application of physical laws, it is possible to extrapolate its use with confidence to other fluids, mixtures, and operating conditions. Copyright © 2011 John Wiley & Sons, Ltd.

Honne oil methyl ester (HOME) is produced from a nonedible vegetable oil, namely, honne oil, available abundantly in India. It has remained as an untapped new possible source of alternative fuel that can be used for diesel engines. The present research is aimed at investigating experimentally the performance, exhaust emission, and combustion characteristics of a direct injection diesel engine (single cylinder, water cooled) typically used in agricultural sector over the entire load range when fuelled with HOME and diesel fuel blends, HM20 (20% HOME + 80% diesel fuel)–HM100. The properties of these blends are found to be comparable with diesel fuel conforming to the American and European standards.

The combustion parameters of HM20 are found to be slightly better than neat diesel (ND). For other blend ratios, these combustion parameters deviated compared with ND. The performance (brake thermal efficiency (BTE), brake-specific fuel consumption, and exhaust gas temperature) of HM20 is better than ND. For other blend ratios, BTE is inferior compared with ND. The emissions (CO and SO) of HM20–HM100, throughout the entire load range, are dropped significantly compared with ND. Unburned hydrocarbon emissions of HM20–HM40, throughout the entire load range, is slightly decreased, whereas for other blend ratios, it is increased compared with ND. NO_x emissions of HM20, throughout the entire load range, is slightly increased, whereas for other blend ratios, it is slightly decreased.

The reductions in exhaust emissions together with increase in BTE made the blend HM20 a suitable alternative fuel for diesel fuel and thus could help in controlling air pollution. Copyright © 2011 John Wiley & Sons, Ltd.

Spacecraft venturing to the outer planets and beyond—or onto the planetary surface where available solar energy is reduced—benefit from the longevity and consistency of electrical and thermal energy derived from radioisotope energy sources. A review of likely mission requirements and concept studies of small electrical generating units (<10 W_e) reveals a potential opportunity for a unit with an electrical output of around 1 W_e that can also supply some heat to the spacecraft to aid thermal control: a radioisotope thermoelectric and heating unit. This power requirement cannot be achieved with current US space-qualified modular radioisotope fuel assemblies. Additionally, new European programmes consider ²⁴¹Am fuel to be much more cost effective than ²³⁸Pu. Taken together, these factors provide the rationale for taking a relatively ‘clean-sheet’ approach to design of a radioisotope thermoelectric and heating unit fuelled with ²⁴¹Am. In this paper, initial requirements and performance targets for such a unit are developed, a simple concept design and thermal model is presented and the performance and mass are estimated. The results suggest that units generating 1–2 W_e may achieve a specific power of around 0.7–0.9 W_e kg⁻¹ without the thermal inputs to spacecraft becoming impractically large. Such units can use a bismuth telluride thermoelectric material, which is commercially applied in terrestrial applications and is therefore likely to incur lower cost and development risk than more specialised compounds. This study may form the basis of a more detailed design effort. Copyright © 2011 John Wiley & Sons, Ltd.

Greenhouse gas emission reduction is the pillar of the Kyoto Protocol and one of the main goals of the European Union (UE) energy policy. National reduction targets for EU member states and an overall target for the EU-15 (8%) were set by the Kyoto Protocol. This reduction target is based on emissions in the reference year (1990) and must be reached by 2012. EU energy policy does not set any national targets, only an overall reduction target of 20% by 2020. This paper transfers global greenhouse gas emission reduction targets in both these documents to the transport sector and specifically to CO₂ emissions. It proposes a nonlinear distribution method with objective, dynamic targets for reducing CO₂ emissions in the transport sector, according to the context and characteristics of each geographical area. First, we analyse CO₂ emissions from transport in the reference year (1990) and their evolution from 1990 to 2007. We then propose a nonlinear methodology for distributing dynamic CO₂ emission reduction targets. We have applied the proposed distribution function for 2012 and 2020 at two territorial levels (EU member states and Spanish autonomous regions). The weighted distribution is based on per capita CO₂ emissions and CO₂ emissions per gross domestic product. Finally, we show the weighted targets found for each EU member state and each Spanish autonomous region, compare them with the real achievements to date, and forecast the situation for the years the Kyoto and EU goals are to be met. The results underline the need for ‘weighted’ decentralised decisions to be made at different territorial levels with a view to achieving a common goal, so relative convergence of all the geographical areas is reached over time. Copyright © 2011 John Wiley & Sons, Ltd.

The Brayton cycle's heat source does not need to be from combustion but can be extracted from solar energy. When a black cavity receiver is mounted at the focus of a parabolic dish concentrator, the reflected light is absorbed and converted into a heat source. The second law of thermodynamics and entropy generation minimisation are applied to optimise the geometries of the recuperator and receiver. The irreversibilities in the recuperative solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In a small-scale open and direct solar thermal Brayton cycle with a micro-turbine operating at its highest compressor efficiency, the geometries of a cavity receiver and counterflow-plated recuperator can be optimised in such a way that the system produces maximum net power output. A modified cavity receiver is used in the analysis, and parabolic dish concentrator diameters of 6 to 18 m are considered. Two cavity construction methods are compared. Results show that the maximum thermal efficiency of the system is a function of the solar concentrator diameter and choice of micro-turbine. The optimum receiver tube diameter is relatively large when compared with the receiver size. The optimum recuperator channel aspect ratio for the highest maximum net power output of a micro-turbine is a linear function of the system mass flow rate for a constant recuperator height. For a system operating at a relatively small mass flow rate, with a specific concentrator size, the optimum recuperator length is small. For the systems with the highest maximum net power output, the irreversibilities are spread throughout the system in such a way that the internal irreversibility rate is almost three times the external irreversibility rate. Copyright © 2011 John Wiley & Sons, Ltd.

The commercial development and current economic incentives associated with energy storage using redox flow batteries (RFBs) are summarised. The analysis is focused on the all-vanadium system, which is the most studied and widely commercialised RFB. The recent expiry of key patents relating to the electrochemistry of this battery has contributed to significant levels of commercialisation in, for example, Austria, China and Thailand, as well as pilot-scale developments in many countries. The potential benefits of increasing battery-based energy storage for electricity grid load levelling and MW-scale wind/solar photovoltaic-based power generation are now being realised at an increasing level. Commercial systems are being applied to distributed systems utilising kW-scale renewable energy flows. Factors limiting the uptake of all-vanadium (and other) redox flow batteries include a comparatively high overall internal costs of $217 kW⁻¹ h⁻¹ and the high cost of stored electricity of ≈ $0.10 kW⁻¹ h⁻¹. There is also a low-level utility scale acceptance of energy storage solutions and a general lack of battery-specific policy-led incentives, even though the environmental impact of RFBs coupled to renewable energy sources is favourable, especially in comparison to natural gas- and diesel-fuelled spinning reserves. Together with the technological and policy aspects associated with flow batteries, recent attempts to model redox flow batteries are considered. The issues that have been addressed using modelling together with the current and future requirements of modelling are outlined. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, a gamma-type low temperature differential Stirling engine was designed and manufactured. The displacer and piston of the engine were concentrically situated to each other. The engine was tested by using a liquefied petroleum gas burner at laboratory conditions. The working fluid was ambient air at atmospheric pressure. Test procedure intended to investigate the speed-torque and speed-power characteristics of the engine depending on the hot-end temperature. Two different displacers made of aluminum alloy and medium density fiberboard were used. The maximum torque and power obtained were 0.166 Nm at 125 rpm speed and 3.06 W at 215 rpm speed, respectively, at 160 °C hot-end temperature with medium density fiberboard displacer. Copyright © 2011 John Wiley & Sons, Ltd.

Previous studies by the authors have shown that energy savings in pulp and paper mills offer opportunities for increased electricity production on-site or wood fuel export. The energy export implies reductions in CO₂ emissions off-site, where fossil fuel or fossil-fuel-based electricity is replaced. To assess this potential and the related profitability for a future situation, four energy market scenarios were used. For a typical Scandinavian mill, the potential for CO₂-emission reductions was 15–140 kton year⁻¹ depending on the scenario and the form of energy export. Extrapolated to all relevant mills in Sweden, the potential was 0.4–3.1 Mton year⁻¹, which is in the order of percent of the Swedish CO₂ emissions. Wood fuel export implies larger reduction in CO₂ emissions in most scenarios. In contrast, electricity export showed better economy in most of the cases studied; with annual earnings of 5–6 M€, this is an economically robust option. In the market pulp mill investigated, the wood fuel export was in the form of lignin. Lignin could possibly be valued as oil, regarding both price and potential for CO₂-emission reduction, making lignin separation an option with good profitability and large reductions of CO₂ emissions. Copyright © 2011 John Wiley & Sons, Ltd.

Comparative analysis of resource input for ethanol produced from corn and sugarcane in temperate, dry, and tropical climate zones was conducted. Parameters such as the Net Energy Value (NEV), water requirement, land requirement, carbon dioxide emission with and without impact of changes in land use, and fertilizer released to the environment—as surface runoff for nitrogen and phosphate, were compared for corn and sugarcane ethanol production. The estimates of NEV for corn ethanol varied from −462 to 1757 kJ l⁻¹, while those of sugarcane ethanol were between 16 057 and 17 092 kJ l⁻¹ for the three climatic zones considered in this study. The results of the study also indicate that ethanol produced from sugarcane uses less or comparable amount of resources in contrast to ethanol produced from corn. Copyright © 2011 John Wiley & Sons, Ltd.

The analysis of heat pump cycles with and without an internal heat exchanger (IHE) is carried out in the paper, in which HFC125/HCs binary mixtures are used as the alternative refrigerants. And the cycle performance under different operation conditions is also compared. The results show that when the mass fraction of HFC125 ranges from 10 to 20%, the coefficient of performance (COP) for HFC125/HC290 (M1) mixtures is 0.92 and 1.01% lower than that of HCFC22 and HFC134a, respectively. For HFC125/HC600 (M2) and HFC125/HC600a (M3) mixtures, the COPs are higher than those of HCFC22 at the mass fraction of HFC125 between 0 and 74.1%, 0 and 66.5% in the mixtures, respectively, and compared with HFC134a, the COPs and volumetric heating capacities are higher when the mass fraction of HFC125 is between 38.6 and 73.3%, and 30.8 and 66%, respectively. For HFC125/HC1270 (M4) mixtures, the COPs are always lower than those of HCFC22 and HFC134a. It is also found that the IHE has a slight effect on the COPs with varying the mass fraction of HFC125 in the binary mixtures. The results obtained can provide some useful guidelines for the choice of alternative refrigerants. Copyright © 2011 John Wiley & Sons, Ltd.

Hydrogen is a promising energy source for the future economy due to its environmental friendliness. One of the important obstacles for the utilization of hydrogen as a fuel source for applications such as fuel cells is the storage of hydrogen. Hydrogen has high gravimetric energy content but low volumetric energy density. It is desired to increase the volumetric energy density of hydrogen in a system to satisfy various applications. Adsorption of hydrogen on sorbents has been investigated. However, the weak interaction force between hydrogen molecules and the sorbents has resulted in low adsorption capacity. In this study, charge was introduced into the system. Several sorbents were investigated. The effects of charge on adsorption enhancement were determined. When NiO was embedded in a PMN-PT piezoelectric material, hydrogen adsorption increased from 0.08 to 0.11 wt% at 135 bar. For the activated carbon sorbent, hydrogen adsorption increased with both the increase in the applied voltage and the increase in the pressure. At 83 bar, the adsorption capacity increases from 0.45 wt% at 0 V to 0.46, 0.49, 0.53, and 0.55 wt% at 500, 1000, 2000 and 3000 V, respectively. Preliminary modeling was carried out to explain the enhancement of adsorption. Modeling was conducted using the B3LYP/6-31G(d) method in the GAUSSIAN 03 software program. The results show that when the electrical field is applied, the hydrogen molecules are more perturbed and attracted closer to the nickel atom, indicating a stronger interaction. The effects increase consistently with the increasing electrical field strength. NiO is a dielectric material. The adsorption enhancement is through the polarization of the compound, which is represented by the Mulliken charge. Carbon is a conductive material. It receives charges on its surface. Although the charges on the sorbents are obtained through different mechanisms, enhancements are found for both materials. Copyright © 2011 John Wiley & Sons, Ltd.

Quality control of the complete energy system is necessary if energy-efficient solutions are to be met. To perform good building operation and quality control of a given system, it is necessary to have information about building systems and assessment tools. The paper presents Norwegian lifetime commissioning (LTC) procedures that are enabling follow-up of the building performance during the building lifetime by establishing a generic framework on building performance data. Further, three developed assessment tools are presented: inspection algorithm for ventilation system, mass balance inspection algorithm for consumer substation, and advanced method for improved measurement of heat pump performance based on data fusion technique. The LTC procedures were tested on two case buildings. The results showed that 20% of all the defined building performance data can be monitored by BEMS. Using the mass balance inspection algorithm, it was found that fault in mass balance prevented implantation of desired temperature control for floor heating system. For heat pump performance, measurement of differential water temperature can be very erroneous. Hence, use of compressor electrical signal can give more precise data on heat pump performance. Comparative analysis showed that detailed monitoring system helps tracking energy use and fault detection in operation. Yearly and hourly profiles of energy consumption with separated use and energy carriers are given in the paper. Copyright © 2011 John Wiley & Sons, Ltd.

The effects of the parameters of the anode gas diffusion layer (GDL), including the PTFE content in the backing layer (BL), the PTFE content in the microporous layer (MPL), and the carbon black loading on the performance of a liquid-feed direct dimethyl ether fuel cell (DDFC), were experimentally investigated. The results indicated that increase in the PTFE content can produce more cracks across the whole surface of the MPL. These cracks were benefit to the anode two-phase mass transport. The optimal PTFE content in anode BL and MPL was 18 and 40 wt%, respectively. The performances of the DDFCs tended to decline with the increase in the carbon black loading in the anode GDLs due to the difficult long path of mass transport. The maximum power density was obtained with 18 wt% PTFE in BL and 0 mg cm⁻² carbon black loading, the optimal result, was 76.6 mW cm⁻² at ambient pressure. Copyright © 2011 John Wiley & Sons, Ltd.

This paper investigates the effects of relative humidity (RH) and stoichiometry of reactants on the water saturation and local transport process in proton exchange membrane fuel cells. A two-dimensional model was developed, taking into account the effect of the formation of liquid water on the reactant transport. The results indicate that the reactant RH and stoichiometry significantly affect cell performance. At a constant anode RH = 100%, a lower cathode RH maintains membrane hydration to give better cell performance. At a constant cathode RH = 100%, a lower anode RH not only provides more hydrogen to the catalyst layer to participate in the electrochemical reaction but also increases the difference in the water concentrations between the anode and cathode. This enhances the back-diffusion of water from the cathode to the anode, reducing possible flooding for better cell performance. Higher anodic stoichiometry results in the reduction of cathodic water saturation by increasing water back-diffusion, thereby enhancing fuel cell performance. Higher cathodic stoichiometry also reduces water saturation by drying more liquid water to increase cathode local current density. Copyright © 2011 John Wiley & Sons, Ltd.

An adsorption heat pump with a direct contact system for steam generation has been developed and the feasibility of the proposed system was confirmed both theoretically and experimentally. The basic cycle for the system has been proposed to use zeolite–water working pairs in the p-T-x equilibrium curve. To generate steam above 150°C from low-energy level water at 80°C, a direct contact adsorption heat pump prototype was constructed. The experimental results show that steam could be generated by the direct contact system and the relationship between the amount of water adsorbed and the change in temperature with time is discussed. This study is expected to serve as a foundation for developing continuous adsorption heat pump systems for steam generation. Copyright © 2011 John Wiley & Sons, Ltd.

The steam–methane-reformation (SMR) reaction has been modified by including sodium hydroxide in the reaction. It is found that the reaction: 2NaOH+CH₄+H₂O = Na₂CO₃+4H₂ takes place at much lower temperatures (300–600°C) than the SMR reaction (800–1200°C). The reaction rate is enhanced with a nickel catalyst. We have studied the effect of variously ball-milled nickel on the reaction rate and determined the optimum particle size of the catalyst. Best results were achieved by grinding the catalyst for 2 h. Prolonged ball milling caused the nickel platelets to coalesce and grow in size decreasing the reaction rate. Copyright © 2011 John Wiley & Sons, Ltd.

A basic concept for a receiver–reactor for solar sulfuric acid decomposition as the key step of the Hybrid Sulfur Cycle for hydrogen production has been developed and realized. A prototype reactor has been built and is specialized for the second part of the reaction, the decomposition of sulfur trioxide. For a detailed understanding of the operational behavior of the developed reactor type a mathematical model was developed. The reactor model was validated using experimental data from the test operation with a prototype reactor. The present work deals with the optimization of process and design parameters and the evaluation of the achievable performance of the reactor type. Furthermore the reactor model is used for numerical simulations to predict specific operational points of the prototype reactor and the performance of a large-scale reactor on a solar tower.

Influences of operational parameters like absorber temperature, feed mass flow, residence time and initial concentration of the acid are analyzed. In many cases those analyses reveal the existence of an optimum of reactor efficiency. When varying the absorber temperature an optimum of reactor efficiency emerges due to two compensating effects: chemical conversion increases with temperature, whereas re-radiation losses increase disproportionately at the same time. This matches the experimental findings very well.

A large-scale tower receiver–reactor consisting of several individual modules is modeled and simulated. The main differences to the prototype system are the reduced gradients of solar flux distribution on the receiver front face and the reduced thermal conduction losses due to the presence of several neighbor modules at a comparable temperature level. This leads to higher chemical conversions and better efficiencies. Reactor efficiencies up to 75% are predicted. Copyright © 2011 John Wiley & Sons, Ltd.

In zinc–hydrogen peroxide batteries, an active metal − zinc piece is used as the anode and ammonium chloride is used as the electrolyte in the anode zone. A soluble oxidant, hydrogen peroxide, is used as the active cathode substance, and sulfuric acid as an electrolyte in the cathode zone. Carbon felt, the sum of two apparent areas of which is 24 cm², is used as an inert cathode with a PE-01 homogeneous membrane between the anode and cathode zones and 50 mL of solution in both the anode and cathode zones. The discharge characteristics of the batteries at 5 Ω were investigated for various concentrations of hydrogen peroxide, sulfuric acid and ammonium chloride solutions. When a 5-M ammonium chloride solution was used in the anode zone with a 3.2-M sulfuric acid and 3.52-M hydrogen peroxide mixed solution in the cathode zone, an average discharge current of 190 mA, an average output voltage of approximately 0.95 V and an actual gravimetric energy density of 42.73 W h kg⁻¹ were obtained, and the discharge time of the batteries was more than 30 h. Copyright © 2011 John Wiley & Sons, Ltd.

The main objective of this study is to present an integrated thermoelectric–photovoltaic renewable system to dehumidify air and produce fresh water. The system is combined with a solar distiller humidifying ambient air to enhance distillate output to meet the specified fresh water needs for a residential application.

A model is developed to simulate the air dehumidification process using thermoelectrically cooled TEC channels. Experiments were performed to validate the developed model results. It is found that the model predicted well the variation in the air temperature along the channel with a maximum relative error in air temperature less than 2.4%. In addition, the simulation model predicted well the amount of water condensate produced by the integrated system with a maximum relative error of 8.3%.

An optimization problem is formulated to design and set the integrated system optimal operation to produce 10 L of fresh water per day meeting the fresh water needs of a typical residential. Using five TEC channels of a length of 1.2 m and an area of 0.07 × .05 m² integrated with 1.2-m² solar distiller that recirculates a constant air mass flow rate of 0.15 kg s⁻¹ is capable of meeting water demand when air mass flow rate through each TEC channel is optimally set at 0.0155 kg s⁻¹. The associated optimal electrical current input to the TEC modules varied depending on the month and is set at 2.2 A in June, 2.1 A in July and 2.0 A in August, September and October. Copyright © 2011 John Wiley & Sons, Ltd.

This paper compares some important parameters obtained in the hydrogen production between the photosynthetic microorganisms Spirulina maxima 2342 and Scenedesmus obliquus 39. It is also reported the employment of hydrogen produced in this study (m³ s⁻¹) in a proton exchange membrane fuel cell (PEMFC) for electricity production. A comparison is also made between the electric current generated and the final dry biomass (mA mg⁻¹) under specific experimental conditions. In this study, the electric current generated in the PEMFC for a period of 200 min under the light intensity of 150 µE m⁻² s⁻¹ and agitation was monitored. With the average current generated by the fuel cell the hydrogen produced by each microorganism is determined. The chromatography method was used to confirm the presence of hydrogen produced by each microorganism which was fed to the PEMFC. Copyright © 2011 John Wiley & Sons, Ltd.

Liquid fuels from coal and biomass have the potential to reduce petroleum fuel consumption and CO₂ emissions. A multi-equation model was developed to assess the economics of a potential coal/biomass-to-liquids (CBTL) fuel plant in the central Appalachian hardwood region, USA. The model minimizes the total annual production cost subject to a series of regional supply, demand, and other constraints. Model inputs include coal and biomass availability, biomass handling system, plant investment, production capacity, transportation logistics, and project financing. The outputs include the required selling price (RSP) and the optimal logistical decision-making associated with feedstock requirement, collection, delivery, and liquid fuel production. Results showed that the RSP of Fischer–Tropsch (FT) diesel for a 40 000 barrel-per-day CBTL plant with coal/biomass ratio (by weight) of 85/15 was $86.45–87.25 bbl⁻¹ using different biomass handling systems. The RSP would vary between $86.45 and $89.81 per barrel according to different coal/biomass mix ratios. In consideration of the carbon offset credits due to the addition of biomass, the RSP was adjusted to $84.19–86.74 with respect to four levels of carbon prices. Sensitivity analyses indicated that the RSP of FT diesel was mostly affected by plant capacity, capital cost, coal price, and liquid fuel yield. The crude-oil-equivalent price of FT fuels must be above $66 bbl⁻¹ for a CBTL plant to be profitable in central Appalachia for the long run. These results can help investors/decision-makers evaluate future CBTL developments in the region. Copyright © 2011 John Wiley & Sons, Ltd.

The design and cost estimates compared with other systems of an energy-producing reactor system are presented. Heat from hydrino reactions within individual cells provides both the reactor power and the heat for regeneration of the reactants. These processes occur continuously over a plurality of cells in different phases of the processes. The hydrino reactions are maintained and regenerated in a batch mode using thermally coupled multi-cells arranged in bundles wherein cells in the power-production phase of the cycle heat cells in the regeneration phase. In this intermittent cell power design, the thermal power is statistically constant as the cell number becomes large, or the cell cycle is controlled to achieve steady power. The conversion of thermal power to electrical power requires the use of a heat engine exploiting a cycle such as a Rankine, Brayton, Stirling, or steam-engine cycle (Int. J. Energy Res. 1997; 21:113–127; Int. J. Energy Res. 1998; 22:237–248; Int. J. Energy Res. 1998; 22:991–1000; Int. J. Energy Res. 2010; 34:1071–1087; Int. J. Energy Res. 2009; 33:1203–1232). Owing to the temperatures, economy goal, and efficiency, the Rankine cycle is the most practical and can produce electricity from a steam source at 30–40% efficiency with a component capital cost of about $300 per kW electric. Conservatively, assuming a conversion efficiency of 25%, the total cost with the addition of the boiler and chemical components is estimated at $1380 per kW electric. The system applications for distributed power (1–10 MW electric) and central generation retrofit and green-field projects are projected to be very competitive relative to existing power sources and systems. Copyright © 2011 John Wiley & Sons, Ltd.

This paper presents an experimental analysis of an absorption refrigeration system, comparing two different energy sources. The exhaust gas from an internal combustion engine was evaluated against the original energy source, liquefied petroleum gas (LPG). The experiments were performed in a domestic refrigerator, monitoring the air temperature and humidity inside the equipment. A production engine was tested with 25% and wide-open throttle valve (WOT), mounted on a bench dynamometer. The energy demand, cooling capacity and coefficient of performance (COP) were determined for both energy sources. The results showed that engine exhaust gas is a potential source for absorption refrigeration systems. When the engine exhaust gas was used as energy source, the energy available for the refrigerator was higher with 25% throttle valve opening. Copyright © 2011 John Wiley & Sons, Ltd.

New weighted-sum-of-gray-gases model (WSGGM) parameters for H₂O vapor are derived from emissivity correlations in the open literature and presented for use in hydrogen combustion simulations. Predictions employing the new WSGGM are seen to compare favorably against the spectral-line-based WSGGM on benchmark problems as well as in media conditions representative of turbulent hydrogen diffusion flames (Sandia Flame A and a model hydrogen gas-turbine combustor). The Sandia Flame A calculations were performed in a decoupled manner employing experimental measurements of temperature and gas compositions as inputs. The measured temperature variance data were employed to model the turbulence–radiation interactions. A coupled computational fluid dynamic (CFD) calculation was performed to obtain the conditions within the gas-turbine combustor geometry. The observed accuracies of the proposed set of WSGGM parameters in conditions encompassing a wide range of H₂O vapor concentrations and temperature non-homogeneities encountered in combustion media make them amenable to implementation in CFD codes. Copyright © 2011 John Wiley & Sons, Ltd.

The analysis of a subcritical Rankine cycle with superheating, operating between a constant flowrate low-temperature heat source and a fixed temperature sink, according to the principles of classical and finite size thermodynamics, is presented. The results show the existence of two optimum evaporation pressures: one minimizes the total thermal conductance of the two heat exchangers, whereas the other maximizes the net power output. A comparison of such results for five working fluids leads to the selection of R141b for a system generating 10% of a reference power which depends on the specified source and sink characteristics; for the conditions under consideration this reference power is 6861 kW. The results for this particular system show that the minimum total thermal conductance of the two heat exchangers is 1581 kW K⁻¹; the corresponding thermal efficiency is 12.6% and the total exergy losses are 13.8% of the source's exergy. Slightly more than 50% of the exergy destruction occurs in the vapor generator. Copyright © 2011 John Wiley & Sons, Ltd.

Combined-cycle power plants are currently preferred for new power generation plants worldwide. The performance of gas-turbine engines can be enhanced at constant turbine inlet temperatures with the addition of a bottoming waste-heat recovery cycle. This paper presents a study on the energy and exergy analysis of a novel hybrid Combined-Nuclear Power Plant (HCNPP). It is thus interesting to evaluate the possibility of integrating the gas turbine with nuclear power plant of such a system, utilizing virtually free heat. The integration arrangement of the AP600 NPP steam cycle with gas turbines from basic thermodynamic considerations will be described. The AP600 steam cycle modifications to combine with the gas turbines can be applied to other types of NPP. A simple modeling of Alstom gas turbines cycle, one of the major combined-cycle steam turbines manufacturers, hybridized with a nuclear power plant from energetic and exergetic viewpoint is provided. The Heat Recovery Steam Generator (HRSG) has single steam pressure without reheat, one superheater and one economizer. The thermodynamic parameters of the working fluids of both the gas and the steam turbines cycles are analyzed by modeling the thermodynamic cycle using the Engineering Equation Solver (EES) software. In case of hybridizing, the existing Alstom gas turbine with a pressurized water nuclear power plants using the newly proposed novel solution, we can increase the electricity output and efficiency significantly. If we convert a traditional combined cycle to HCNPP unit, we can achieve about 20% increase in electricity output. This figure emphasizes the significance of restructuring our power plant technology and exploring a wider variety of HCNPP solutions. Copyright © 2011 John Wiley & Sons, Ltd.

The importance of gravity effect on the performance of proton exchange membrane fuel cell (PEMFC) has recently been recognized. In this paper, the effect of gravity on the performance of PEMFC has been investigated associating with different gas intake modes. The polarization curves of the stack with different positions of reaction gas inlet and outlet at varied gravitational angles are addressed in detail. The results indicate that the output power of PEMFC stack can be greatly enhanced at the optimized gravitational angle. Gas intake modes that were realized by varying the gas inlet and outlet positions strongly affect the stack performance as well. The optimized performance can be reached at the tilted angle of 90° when both air and hydrogen inlets are placed at the upper side of the stack, whereas the worst performance occurs at the tilted angle of 90° when air and hydrogen flow into the channel from the bottom side of the stack. These results have important implications for PEM fuel cell design and operational strategies. In order to improve the performance, fuel cells should be designed and operated at the optimized gravitational angle and gas inlet/outlet position. Copyright © 2011 John Wiley & Sons, Ltd.

In this study, an integrated community-scale energy model (ICEM) was developed for supporting renewable energy management (REM) systems planning with the consideration of changing climatic conditions. Through quantitatively reflecting interactive relationships among various renewable energy resources under climate change, not only the impacts of climate change on each individual renewable energy but also the combined effects on power-generation sector from renewable energy resources could be incorporated within a general modeling framework. Also, discrete probability levels associated with various climate change impacts on the REM system could be generated. Moreover, the ICEM could facilitate capacity–expansion planning for energy-production facilities within a multi-period and multi-option context in order to reduce energy-shortage risks under a number of climate change scenarios. The generated solutions can be used for examining various decision options that are associated with different probability levels when availabilities of renewable energy resources are affected by the changing climatic conditions. A series of probability levels of hydropower-, wind- and solar-energy availabilities can be integrated into the optimization process. The developed method has been applied to a case of long-term REM planning for three communities. The generated solutions can provide desired energy resource/service allocation and capacity–expansion plans with a minimized system cost, a maximized system reliability and a maximized energy security. Tradeoffs between system costs, renewable energy availabilities and energy-shortage risks can also be tackled with the consideration of climate change, which would have both positive and negative impacts on the system cost, energy supply and greenhouse-gas emission. Copyright © 2011 John Wiley & Sons, Ltd.

The new generation of steam power plants operates at pressures higher than the critical pressure and at very high temperatures. They are called supercritical power plants and their thermal efficiency is improved by increasing their operating pressure and temperature. Such a demanding working environment causes high stresses in the construction, especially during the heating and cooling operations. Additionally, the cyclic character of loading during operations causes material fatigue, known as low-cyclic fatigue. This phenomenon may lead to the formation of fractures. Steam boiler manufacturers make efforts to design pressure elements to meet these high requirements. They make recommendations for conducting start up and shut down operations in order to keep the stresses in the construction elements within acceptable limits and obey the safety regulations. Thus, it is important to find optimum parameters that can ensure proper heating and cooling processes (Struct. Multidiscip. Optim. 2010; 40:529–535, Proceedings of the Congress on Thermal Stresses, 2007; 437–440).

Paper (Proceedings of the Congress on Thermal Stresses, 2007; 437–440) presents the method for determining the optimum medium temperature, which ensures that the sum of the thermal stresses and stresses caused by pressure at selected points do not exceed the allowable stresses. The presented optimum medium temperature consists of the initial medium temperature step and later increases in the optimum rate of temperature change. The extended version of the paper (Proceedings of the Congress on Thermal Stresses, 2007; 437–440) was published in 2010 (Int. J. Energy Res. 2010; 34:20–35). Another paper (Proceedings of the 8th International Congress on Thermal Stresses, 2009; 2:399–402) presents the numerical optimization procedure, based on the Levenberg–Marquardt algorithm that allows the optimum medium temperature to be established. This procedure is based on the assumption that the thermal stresses in the entire construction elements do not exceed the allowable stresses.

The aim of this paper is to present the method, which makes it possible to find the optimum parameters, so that the total stresses during the start-up processes are kept at an acceptable level. The maximum absolute stresses, caused by non-uniform temperature distribution and by pressure, are monitored not only at selected points but also in the whole construction element.

The described method is of great practical significance and can be applied directly in the industry. It can be utilized in supercritical as well as subcritical power plants. The method proposed can greatly enhance the performance of the power units by reducing the duration of all the transient operations and extending their longevity. The presented heating operation based on the optimum parameters is compared with the German boiler regulation-Technische Regeln für Dampfkessel 301 (TRD) (Technische Regeln für Dampfkessel, 1986; 98–138). Copyright © 2011 John Wiley & Sons, Ltd.

In