Assessment of electrical power generation in various regions of Nepal through solar organic Rankine cycle technology

The utilization of solar organic Rankine cycle (ORC) technology in Nepal shows promise due to its ample solar radiation. This technology should be harnessed for the purpose of generating solar energy. The academic version of engineering equation solver was used to develop simulation models, which predict the potential of solar ORC power generation across the country. The study is limited to areas with solar irradiance of 5.5 kWh/m2/day and excludes certain regions. The installation of the plant requires open land with access to water, and a 10 km2 land area was considered for the solar collector. The working fluids for the solar ORC plant are R245fa, R11, and R123. The simulation results showed a maximum overall system efficiency of 6.8%. The power output for various districts was also simulated, with Jumla having the highest power output, followed by Baitadi and Surkhet. The power output for different temperatures (90–120°C) using R245fa as the working fluid was 270, 320, 350, and 380 MW. Additionally, the study determined the cost of electricity production for the system with working fluids. The cost of electricity production was found to be 164.11$/MWh, and the levelized cost of electricity ranged from 220–265$/MWh. The payback period for the investment varies from 18 to 12 years with an internal rate of return of over 10%. Furthermore, a sensitivity analysis was conducted to ascertain the feasible investment strategies for the solar ORC system. Therefore, the study concludes that a solar ORC plant is technically feasible in Nepal for electrical power generation, with promising potential for clean energy generation.

BARAL power.By using high molecular mass organic fluids with low boiling points, heat can be recovered from low temperature heat sources that would otherwise be unusable.The ORC system is gaining popularity globally due to its simplicity in design and the availability of important components.The working fluid in the ORC system is an organic substance that is better adapted than water to lower heat source temperatures.According to Market Watch News (2022), the Organic Rankine Cycle market in the US is estimated to be worth US$77.8 million in 2021, accounting for a 30.2% share in the global market.China is expected to reach an estimated market size of US$218.6 million by 2026, with a compound annual growth rate (CAGR) of 19.2% over the analysis period. 3he process of solar ORC can be described as the following: solar radiation is absorbed by evacuated tubular solar collectors, where cold water is heated and stored in a tank.The hot water is then pumped into a plate-type heat exchanger (evaporator), where it vaporizes organic working fluid, driving a magnetically coupled scroll expander to produce mechanical power.The working fluid is then condensed back into liquid form using cooling water in the condenser and returned to the refrigerant tank to complete the cycle.The mechanical power generated is used to drive an electrical generator for electricity generation.The schematic diagram for the working principle of the plant is described in the Figure 1.
5][6][7][8][9] The working fluid enables recovery of heat from lower temperature sources such as solar collector.The low temperature heat is used to drive a turbine and create electricity.However, the efficiency of solar ORC is relatively low due to the low temperature range obtained from the collectors.It is suggested that obtaining hotter water (90-120 • C) from the solar collector could improve efficiency.][19][20][21][22][23] Furthermore, the economic assessment was conducted in this study in order to help the solar ORC investors, manufacturers, energy planners, environmentalists; various aid agencies and so on so that this type of ORC system is feasible in Nepal.Economic parameters such as net present worth, payback period, and benefit cost ratio, internal rate of return and levelized cost of electricity generation (LCOE) was assessed.In addition, the CO 2 emissions from the system have also been estimated.
The study holds unique significance due to Nepal's distinctive geographical elevation, solar irradiance patterns and local conditions.The country's diverse geography, elevation and latitude demands varying solar energy availability and temperature profiles which impacts the performance of solar ORC systems.The study aims to explore how these geographical factors affect the feasibility and efficiency of implementing solar ORC technology in Nepal.Additionally, the research focuses on the influence of Nepal's diverse climatic conditions on the operational characteristics of solar ORC systems.The study also highlights the potential of solar ORC technology to address Nepal's energy access challenges in remote areas aligning with the nation's rural electrification goals.Besides, the study addresses the challenge of data availability by collecting and validating specific local data related to solar irradiance, temperature, and energy demand patterns in different Nepalese regions.By addressing these specific aspects, the present research could provide valuable insights for policy makers, energy planners, and researchers interested in advancing sustainable energy solutions tailored to Nepal's needs.This in turn helps to develop a novel approach to address the energy needs of rural areas in Nepal by creating solar energy clusters powered by ORC technology.These clusters will consist of interconnected microgrids that utilize the abundant solar radiation in Nepal to generate clean and reliable electricity for local communities.
The main objective is to develop the simulation models for potential of solar based ORC for power generation in Nepal.The specific objectives include: 1. To model the performance of the system in the Nepalese climate over an annual period.2. To model the various components of the solar ORC power system such as solar collector, thermal storage, evaporator, turbine, condenser, and working fluid feed pump.3. To map the potential for installation of solar ORC system in several regions of Nepal.4. To develop a techno-economic model for technical feasibility in Nepal. 5. To evaluate the levelized cost of electricity produced by this proposed solar ORC system along with the potential for CO 2 emissions reduction.

LITERATURE REVIEW
Numerous academic papers have investigated the utilization of ORC technology for power generation in solar applications.Both portable and large-scale solar ORC systems show promise as potential technologies.The performance of the system and its compatibility largely depend on the organic working fluid used.Additionally, the power generation of the system is determined by the solar irradiance in the particular location.Greater solar irradiance leads to higher power generation and a shorter payback period, making it more economically viable.The literature on ORC technology encompasses both theoretical and experimental studies and includes biomass, geothermal, and solar applications due to their renewable energy resources.Aryanfar et al. 24 explores a combined power generation and cooling system in rural areas, utilizing an ORC powered by a parabolic trough solar collector.Four different working fluids are investigated: R245fa, R114, R600, and R142b.The research reveals that integrating ORC with a vapor compression cycle (VCC) enhances the thermal efficiency of the power plant, with R245fa exhibiting the lowest exergy destruction rate.Freeman et al. 25 conducted a simulation of a solar combined heat and power system at a domestic scale that is suitable for the UK climate.The system comprised of a solar collector, an ORC unit, and a hot water cylinder tank, which generated an electrical power output of 89 W. The combined system had a total cost of £2700, with a LCOE of 44 p/kWh.Francesco et al. 26 presented a novel design and simulation of a small-scale solar power plant that used evacuated solar thermal collectors.The study found that the efficiency of the system reached nearly 10%, and a solar field of approximately 73.5 m 2 was required.Similarly, Heberle and Brüggemann 27 performed a thermoeconomic evaluation of binary power plants based on the ORC for geothermal power generation.The study analyzed whether the use of zeotropic mixtures as a working fluid improved the efficiency of the system, and whether this improvement compensated for additional requirements regarding the major power plant components.The results indicated that using zeotropic mixtures is a promising approach to enhancing the economics of geothermal ORC systems.Alghamdi et al. 28 analyzed the double flash geothermal cycle using zeotropic fluid in the ORC, evaluating its thermodynamics based on the first and second laws.Hexane, cyclohexane, and isohexane were identified as effective fluids for higher temperatures.Comparisons were made between pure fluids and zeotropic fluids, assessing cycle efficiency, net power output and exergy destruction due to refrigerant mass fraction variations.Baral et al. 29,30 created and tested a solar ORC system at a small scale.This system utilized a scroll expander to produce 1.4 kW of power at a heat source temperature of 120 • C and achieved a thermal efficiency of 8.1%.Through simulation analysis, Cioccolanti et al. 31 studied a novel 2 kWe ORC plant that utilizes concentrated solar power and a phase change material storage tank equipped with reversible heat pipes.They discovered that the plant can achieve high conversion efficiency when it is supplied with energy from the storage tank's discharge, which occurs approximately 800 h per year.In their research article, Costa et al. 32 outlined a design study of a latent heat thermal storage system integrated into a micro-solar ORC power plant that operates within temperature ranges of 220 to 230 • C. Their study emphasized the significance of phase change material in heat transfer and demonstrated that aluminum fins outperformed steel materials.Garcia-Saez et al. 33 conducted an economic evaluation of various scenarios and found that residential systems operating on a small scale in certain climates and locations demonstrated internal rate of return (IRR) values exceeding 15% and had payback periods as short as 3.1 years.Ashouri et al. 34 presented an exergo-economic analysis and optimization of a double pressure ORC coupled with a solar collector via a thermal storage tank.Their findings showed that the system could achieve an efficiency of 22.7% and a product cost rate of 2.66 million dollars per year.In the same vein, Baral 35 conducted a thermoeconomic analysis on a hybrid solar geothermal ORC system and found that the levelized cost of electricity generation for the system was $0.17/kWh and $0.14/kWh when using R134a and R245fa as working fluids, respectively.In a similar manner, Calli et al. 36 demonstrated the energy, exergy, and thermoeconomic aspects of combined biomass and solar ORC systems.Their findings revealed that the ORC system based on biomass had the greatest electrical efficiencies, specifically 10.61%.Additionally, when the system was equipped with four or fewer collectors, the thermoeconomic benefits of a system that combined solar collectors and a biomass burner surpassed those of a solar-based ORC system with 12 collectors.The trends in research for ORC systems were highlighted by Park et al. 37 in 2018, with R245fa being the most popular working fluid, followed by R123 and then R134a, and an average back-work ratio of 25.9% for ORC experiments.Oyekale et al. 38 evaluated siloxane mixtures and found an improvement in net power and exergetic efficiency of ORC plants.The studied mixtures also increased heat exchange area by about 20%, compared to pure fluid.Ardeh et al. investigated a solar ORC system that utilized a parabolic trough collector with a linear V-Shape cavity receiver.The system was evaluated under exergy and economic analyses, and the optimum condition resulted in a lowest LCOE of 0.0716 (€/kWh) and a lowest payback period of 8.79 (years).An analysis was presented by Spayde et al. 39 to determine the economic, energetic, and environmental benefits of combining solar-power ORC with electric energy storage (EES) to supply electricity to several units.The proposed ORC-EES system was found to be capable of satisfying 11%, 13%, and 18% of the electrical demand for the large office, small office, and restaurant, respectively.For the small office building, the ORC-EES could generate between 11% and 17% of the monthly electricity required, while for the large office building, it could generate between 8% and 13% of the monthly electricity required.Sonsaree et al. 40 analyzed three different capacities of the ORC system with R245fa in combination with a solar water heating system.They used a mathematical model to evaluate the maximum power output, CO 2 emissions, and LCOE, and found that the system could produce a power output of 113.5 MWh/year, reduce CO 2 emissions by 62.2 tons CO2 eq./year, and achieve an LCOE of 0.20 USD/kWh.Ungureşan et al. 41 conducted a mathematical investigation on the potential of solar ORC systems in multiannual climate data for Cluj-Napoca, Romania, using three different collectors: evacuated tubes, flat plate, and parabolic trough.They reported that the maximum global efficiencies ranged from 6.73% to 10.23%.Leal-Chavez et al. 42 proposed an ORC system coupled with a solar domestic hot water system for cogeneration applications in 2019.Simulation results showed that the system could generate 443 kWh of annual electrical energy with a global efficiency of 6.65% when the solar collector was 2.84 m 2 .Soulis et al. 43 investigated geospatial analysis approaches for the techno-economic analysis of a two-stage solar ORC engine.The simulation model utilized 34 years of reference period for daily meteorological data, and the resulting energy cost in Greece was found to be between 0.41 and 0.7 €/kWh.The obtained results were mapped to present various aspects of the system.

MATERIALS AND METHODS
There few steps that needs to be taken to estimate the potential of solar ORC projects in Nepal.The first step is to assess the solar radiation data to determine the feasibility of the project.This can be done through satellite imagery, ground-based measurements, or weather models.The analysis of solar radiation data helps to identify regions in Nepal with the highest solar potential.Once potential project sites have been identified, accessibility, proximity to transmission lines, and other construction and maintenance requirements should be considered.The ideal site would be easily accessible and have high solar radiation levels.The size of the solar ORC system should be based on available solar radiation data and the specific energy demand of the area.The appropriate technology for efficiently converting solar energy into electricity should be selected, taking into consideration the cost-effectiveness of the technology.An economic analysis should be conducted to determine the financial viability of the project, including costs associated with technology, installation, maintenance, and revenue from the sale of electricity.An environmental and social impact assessment should also be conducted to evaluate the potential effects of the solar ORC project on the local environment and community.Factors to be considered include impact on wildlife, water resources and land use.Lastly, a flow chart for methodology has been created and analyzed to achieve the best evaluation and performance of the solar ORC plant.This flow chart allows for the estimation of the potential of the solar ORC technology in Nepal.Figure 2 shows the flow chart for investigation of the study.

Site selection
This study relies on meteorological data gathered from several sources to assess the performance of ORC systems.Specifically, the data was obtained from a report published by Schillings et al. 44 and includes ambient temperature, solar insolation, solar irradiance, and wind speed measurements.To assess the performance parameters of ORC systems, the study used models based on the governing equations of thermodynamics.These models took into account several components required for the system, such as the evaporator, condenser, turbine, and pump.The models were developed based on the latest research in the field and were carefully calibrated to provide accurate predictions of ORC system performance. 45

F I G U R E 2
Flow chart for solar ORC potential calculation in Nepal.

Solar field
The parabolic trough solar collector with synthetic thermal oil (Therminol VP-1) was taken as reference for solar field along with thermal energy storage.For the organic working fluids R245fa, R11, and R123 were chosen for this system.Generally working fluids with higher critical temperature and pressure are preferred for solar ORC system.The main criterion for selection of these working fluids is critical temperature.Furthermore, working fluids with high critical temperature are stable for running of solar ORC system.

Solar energy resource potential
The formula for calculating the potential of renewable energy resources can be expressed as 46 : where G pot is the geographic potential (GWh), E pot is the energy potential of the renewable resource (GWh/km 2 ), and R ava is the resource availability (km 2 ).
To estimate the technical potential, the capacity factor of the plant and the electrical conversion efficiency of the renewable energy technology are applied.In this case, the technology being used is the solar ORC, which can be represented as: where T pot is the technical potential (GW, GWh), C fac is the capacity factor of the plant, and η ORC is the solar efficiency of the installed technology expressed as a percentage.
The following are the assumptions and methodologies used to assess the potential of solar organic Rankine cycle power and renewable resources in this study: 1.This study considers the use of renewable resources solely for off-grid electricity generation.2. The assessment of the resource potential excluded areas under forests, restricted areas, and water bodies.BARAL 3. A solar ORC potential capacity factor of 0.33 is assumed based on 47 study.4.Only the heat source obtained through parabolic trough technology is considered, with an approximate area of 25 m 2 /kW for solar ORC electricity production, based on 29,30 study.5.The solar to electricity efficiency is assumed to be 7%, based on the existing solar ORC installation plant efficiency, which ranges from 7% to 9%.The working fluid used for the solar ORC is R245fa/R11/R123.The solar collector efficiency is assumed to be 70%. 47

Geographic potential
The solar energy's geographic potential is determined by integrating the yearly solar irradiation over a specific geographical area that is deemed appropriate for the installation of an ORC system.The equation below, as proposed by De Vries et al., 46 can be used to compute the geographic potential: In the equation, GP ORC refers to the technology's geographic potential measured in TWh, I represents the average solar irradiance measured in kWh/m 2 /day, 365 represents the number of days in a year, and R ava represents the resource availability measured in terms of the total area suitable for the technology.

Solar ORC components: Thermodynamic modeling
The solar energy that can be utilized from the sun can be expressed as 48,49 : Generally, the efficiency of the solar collector is expressed by the relationship where ΔT is temperature difference between mean and ambient temperature is the solar collector and is given by 48,49 ΔT = Therminol VP-1 is chosen as heat transfer fluid (HTF).Heat absorbed by HTF can be calculated by Energy balance for ORC working fluid and energy storage system for solar can be shown by Pump model: To create pressure and flow within the system for the organic fluid, a working fluid feed pump is necessary.The rate of consumption and volumetric flow rate are determined by the pump's speed and pressure difference in the cycle.To model and assess the pump's performance, the governing equations are as follows 47,50 These correlations affect the pump performance during its operating conditions.

Heat exchangers models:
The primary role of heat exchangers is to facilitate the transfer of heat from a hot source to a cold sink.In an ORC plant, the heat exchangers serve as the evaporator and condenser, responsible for vaporizing and condensing the working fluid, respectively.The model utilized in this study is governed by the following equations 50 Expander model: A device that converts energy of working fluid into mechanical power through expansion is known as an expander.The model used to simulate the expander can be defined by the following equations 50 Heat losses model is calculated if expander is not properly insulated and is given by The cycle efficiency of the ORC plant and network is given by the following relationships The overall solar ORC system has an expression as follows

Economic analysis
Thermoeconomic analysis is a method used to assess the economic feasibility of thermal systems like the ORC system by evaluating its performance, efficiency, and associated costs.The analysis of ORC systems involves several steps, including determining operating parameters such as heat source temperature, evaporation temperature, and condensation temperature.Performance evaluation involves calculating the thermal and exergetic efficiency of the ORC system by considering its design and operating parameters.Cost analysis entails determining and analyzing the various costs associated with the ORC system, including investment, operating, and maintenance costs.The economic viability of the ORC system is evaluated by utilizing the results of the performance evaluation and cost analysis to calculate key economic indicators such as payback period, internal rate of return, and net present value.The thermoeconomic analysis of ORC systems is a critical tool that enables informed decision-making regarding their design and operation while identifying areas for improvement to enhance their economic viability.The economic analysis is based on economic theories proposed by Park. 51

RESULTS AND DISCUSSION
A solar ORC technology potential for an area of 10 km 2 was chosen with direct normal irradiance greater than 5.5 kWh/m 2 /day for the investigation.The EES software has been used to predict the behavior and performance of solar ORC plant.The suggested sites for installation of the plant have provided from the study.The performance, economic and environmental assessments were also analyzed for the plants in different districts of Nepal.Table 1 provides the technical parameters and assumptions defined for modeling and simulation in EES.The plant is assumed to have maximum evaporating temperature of 120 • C for all the selected working fluids.The thermal efficiencies for working fluids were obtained from the developed models.

Performance analysis of solar ORC plant
The meteorological data to evaluate the efficiencies, power generation, geographic and technical potential for each working fluid was taken to run the simulation.In these Figures 3 and 4, the change in evaporating temperature changes the overall system efficiency.Here, when temperature changes from 90 to 125 • C its efficiency changes from 6.9%-8.5%,7.2%-9%, 7.4%-9.7%for R245fa, R11, and R123, respectively.The amount of heat delivered by solar field determines the evaporating temperature.Therefore, evaporating temperature plays a major role in increasing system's and overall efficiency.
The simulation result illustrates that with change in condensing temperature, the system's efficiency changes.This can be shown in Figure 5.With increase in condensing temperature of the working fluids, the system efficiency decreases.Low condensing temperature exhibits positive effect on the ORC performance such that for R245fa, R11, and R123, the

F I G U R E 4
Effect of evaporating temperature on overall system efficiency.
F I G U R E 5 Variation of system efficiency with condensing temperature.
efficiency changes by 11%-13.9%,12.6%-14.7%,and 13.2%-15.2%,respectively.This trend can be seen by lowering the condensing temperature from 15 to 35 • C. The amount of heat received and rejected in evaporator and condenser, respectively, are also influenced by condensing temperature.The behavior of an ORC system strongly correlates with that of the expander efficiency.The choices of the expanders depend on the operating conditions, pressure ratio and on the size of the system.Figure 6, shows that with increase in expander efficiency, the overall system efficiency increases.For selected working fluids such as R245fa, R11, and R123, the increase in expander efficiency from 70% to 85% results in increment of overall system efficiency by 30.81%.Therefore, F I G U R E 6 Variation of overall efficiency with change in expander efficiency.the design of expander plays very important role in changing the efficiency.Turbine expander has the advantages of compact structure, less vulnerable parts and large enthalpy drop, which makes it very suitable for the ORC system.The design differences between various expansion devices have a significant impact on their efficiency and reliability when operating with different working fluids.There are few cases in experimental data of solar ORC system alone in the literature.In order to validate the accuracy of the proposed modeling of solar ORC system, the validation procedures are described.The validation of the overall solar ORC model is conducted by comparing the efficiency of the test results reported by Park et al. 37 The validation results are based on the design data for solar collectors, turbine, heat exchangers, and pump components used in the system and are shown in Table 2. Besides, the model is compared from reference because this is the only study where ORC layout with the working fluids of the present study has been examined in detailed.The examined parameter for the validation is overall efficiency with change in evaporating temperature of the system.In the present study, the ORC system is examined for working fluid R245fa with source temperature ranging from 90-120 • C. Therefore, the proposed model is in good agreement with the experimental results and the simulation outcomes of the mentioned literature.The deviation in the calculation can be mainly attributed to differences in the type and size of turbines of the proposed study.

TA B L E 2
The power output from the solar ORC technology for various districts with three working fluids has been presented in Figures 7-9.The variation of heat source temperature from 90-120 • C resulted in change power output.It is seen from the figures that solar irradaiance and heat source temperature play vital role in power output from the plant.The solar irradiance of 5.5 kWh/m 2 /day has been taken as working capability of the solar ORC plant.Based on that data, the power output for the various districts were simulated.Here Jumla has the highest power output followed Baitadi and Surkhet.The maximum power output obtained is 270, 320, 350, and 380 MW for 90, 100, 110, and 120 • C, respectively with working fluid R245fa.Similar trends are seen for other two working fluids (R11 and R123) with slightly higher power output.

F I G U R E 9
Power output for various districts with working fluid (R11).
The solar ORC systems can be more feasible if the government provides support by subsidizing the investment cost of the solar collectors by more than 60% in its capital cost.A renewable energy resource such as solar ORC system helps in reducing CO 2 emissions to the environment.This Figure 10, illustrates technical potential of solar ORC technology and CO 2 emission savings.It is observed that 340 MW of output power saves 460 kilotonnes of CO 2 emission for the R245fa.Similarly, for R123 and R11 it could save 660 and 675 kilotonnes emissions, respectively.The solar ORC system can be suited either peak-load power stations or intermediate-load power stations with typical capacity factor less than 30% in context to Nepal.

Economic analysis
The solar ORC system can able to produce electricity with different solar source temperatures.From the exergy and economics point of view, the cost of electricity production rate is calculated.Since the solar energy is converted into power output, the fuel cost is assumed to be zero.The complete breakdown cost of the system is presented in Figure 11.
The major financial contribution should be addressed for solar field and HTF system followed by ORC plant components costs which are 38% and 23%, respectively.
Figure 12 demonstrate the annual cash flows for the system during the life cycle of the solar ORC system.It is assumed that continuous same amount of revenue is generated through the years whereas cost of operations is also same amount during the life cycle period.
Table 3 shows the plant description with the parameters needed for economic analysis.In this model, the cost of land is not included.The cost of leasing land in hills and mountain is estimated $10-15 per 508.72 m 2 and in case of Terai $8-10 per 338.63 m 252 In order to estimate cost of electricity production economic parameters such annual equivalent, operation and maintenance (O&M) and electricity generation value must be known first.Here, the annual cost was taken as 2% for the estimation. 27The estimated of power output for 260 MW solar ORC plant cost around $ 866 millions.The cost of electricity production was found to be 164.11$/MWh.
In this present study, an interest rate of 5% is taken for the economic analysis.Higher the interest rate, the higher is the cost of produced electricity.The cost of electricity production for the study was estimated to be 164.11$/MWh.Also payback period is the number of years necessary to recover the solar ORC system cost of an investment under consideration.The payback period is calculated on the basis of the revenue generation during the period of time.It is observed that  when the LCOE from 220-265$/MWh, the payback period changes from 18 to 12 years for three working fluids (R245fa, R11, and R123).These can be demonstrated in Figures 13 and 14.
Another economic indicator used to measure the financial aspect is IRR.It is the break-even interest rate at which the net present worth of a solar ORC system is zero.This analysis allows the solar ORC developers and investors for the comparison of different financial scenarios.This is commonly used for accepting/rejecting the ORC system for investment.Since the interest rate was 5% during estimation, the IRR should be higher for economically feasible with different temperature solar source.Here, the highest IRR which is 10% for thermal storage type of solar ORC system.Fully dispatchable solar electricity from CSP ST with thermal energy storage is achievable in Australia for 8-10 c/kWh, well below every alternative.

F I G U R E 13
Change in NPV during system life period with several LCOE (R245fa).
F I G U R E 14 Change in NPV during system life period with several LCOE (R123).F I G U R E 15 Change in NPV with economic scenarios.

TA B L E 4
Table 4 shows the comparison of LCOE for various renewable energy technologies in the world.The cost of solar ORC system is relatively high as compared to these already matured technologies.
The validation process of the thermoeconomic model presented in this study involves comparing it with the work of Preißinger and Brüggemann 54 in the literature.The formulated model's primary aim is to optimize both the component configurations and system parameters of the ORC plant.According to the literature, the specific investment cost (SIC) is noted as $4838.61/kW,whereas in our current study, the SIC is reduced to $4330/kW.This adjustment in cost reflects a slight deviation of 10.51%.Consequently, the proposed model for the system not only offers more reasonable solutions but also grants greater flexibility in selecting schemes for decision makers.

Sensitivity analysis
The sensitivity analysis is performed for investigating the parameters which make solar ORC technology economically feasible and more profitable.In this study, the sensitivity analysis was carried for financial model output (NPV) against the main financial model parameters; capital cost (solar field cost, ORC cost and miscellaneous cost), benefit cost (annual electricity generation cost), interest rate and operation, and maintenance cost (annual operating cost).Table 5 illustrates change in NPV for sensitivity analysis with several economic scenarios that affect economic parameters.Furthermore, Figure 15 shows that the most important parameter in NPV evaluation is the capital cost and O&M cost.This means if these costs are reduced, then the solar ORC system can be more feasible.Other parameters that influence the NPV are interest rate and benefit cost.Though an increase or decrease of 15% in these parameters results very low impact on the NPV and suggest that it is less sensitive.

CONCLUSIONS
The study discussed the development of a simulation model and the potential of solar ORC for power generation in various districts of Nepal.The EES model was utilized to suggest the installation potential of solar ORC plant based on solar radiation intensity greater than 5.5 kWh/m 2 per day, which was chosen due to Nepal's topography.The annual performance of the plant was analyzed to estimate annual power production and overall system efficiency.Moreover, a techno-economic analysis was conducted by assessing financial key indicators like NPV, LCOE, benefit-cost ratio, IRR, and payback period.The following conclusions were drawn from the study's findings: 1.The solar ORC plant has the capacity to produce 423.84GWh annually with a net efficiency of 6.8% for R245fa.Working fluids R11 and R123 can produce slightly more than R245fa, with overall system efficiencies of 7.4% and 7.1%, respectively.2. The environmental benefit of the solar ORC plant includes saving up to 660 kilotons of CO 2 emissions.3. The cost of electricity production for the plant in Nepalese climatic conditions is found to be $164.13/MWh.4. The maximum LCOE for the plant is estimated to be $265/MWh, with a payback period of 12 years, IRR of 10%, and benefit-cost ratio of 1.3 for R123. 5. Sensitivity analysis revealed that a decrease in capital cost and O&M cost can significantly impact LCOE and NPV.
To address the study's limitations in future work, conducting in-depth analyses is recommended.There is a need to investigate emissions resulting from leakage sources, assessing their environmental impact on the solar ORC system's sustainability.Alongside this, an economic assessment that incorporates emission-related costs should be conducted.Additionally, a comprehensive life cycle assessment should be performed to evaluate environmental impacts throughout the plant's lifecycle, considering factors beyond CO 2 emissions.Moreover, performing a detailed decommissioning study to outline strategies for dismantling and disposing of system components and exploring alternative working fluids while assessing their environmental impact, efficiency and safety can also be taken as future work.

TA B L E 1 3
Technical parameters for simulation and modeling.Description ValueDesign capacity for solar ORC system (Area of collector, m 2 Effect of evaporating temperature on cycle efficiency.

F I G U R E 7
Power output for various districts with working fluid (R245fa).

F I G U R E 8
Power output for various districts with working fluid (R123).

10
Effect of expander inlet temperature on power output and CO 2 emission savings.

F
I G U R E 11 Component wise cost of solar ORC plant.F I G U R E 12Annual cash flows diagram during the life cycle.
Validation of the solar ORC model for the present work. 53

TA B L E 3
Annual economic parameters for solar ORC plant.
53mparison of LCOE for various renewable energy technologies.53Descriptionand values under several economic scenarios.