Techno‐economic analysis of PV–wind–diesel–battery hybrid power systems for industrial towns under different climates in Spain

This study aimed to provide a techno‐economic analysis of hybrid energy systems, including wind turbines, photovoltaic systems (PV) panels, diesel generators, and batteries, for selected cities in five different climate zones in Spain to meet the load requirements of industrial towns. Homer software was used to determine the most efficient configuration for supplying the average load of the industrial sector, with a value of 1500 kWh/day and a peak load of 114.58 kW, and the residential sector, with a value of 150 kWh/day and a peak load of 27.85 kW. Optimization is carried out to minimize the evaluation parameters of net present cost (NPC) and cost of energy (COE). According to the software outputs, it appears that the system utilizes a variety of renewable energies. The priority is to use all hybrid system components, and the wind–PV–diesel–battery configuration has performed best in all cities. The cities of A Coruña, Bilbao, Ponferrada, Almería, Barcelona, Salamanca, Seville, Zaragoza, and Madrid, respectively, with NPC values of 1.39, 1.67, 1.76, 1.92, 2.23, 2.29, 2.39, 2.55, 2.61 M$ and COE values of 0.199, 0.24, 0.252, 0.276, 0.32, 0.329, 0.343, 0.366, 0.374 $/kWh have economic efficiency from the highest to the lowest. Reducing pollution production is one of the key reasons for approaching hybrid technologies. In this regard, A Coruña has the lowest carbon emissions among the selected cities, with 25,190, and 95.5% of its energy production is renewable. On the other hand, Madrid, which uses 89% renewable energy, has the highest carbon dioxide production with a value of 59,242. The system analysis in different cities of Spain provides insight into the conditions necessary for establishing such systems in different climate zones, which can serve as a road map for other places in the country.


| INTRODUCTION
Recently, natural disasters have occurred more frequently due to global warming and are expected to occur more often. Heat waves have been linked to the initiation of wildfires. Governments must act more responsibly to safeguard houses from flooding and fire and educate the public about these inevitable disasters. Nations must protect their crops and forests against drought and fortify their coastlines against overflows. 1 In accordance with the Paris Climate Accords, if global warming exceeds 2°C, water scarcity will double compared with the 1.5°C scenario. Additionally, 1.5 billion people will face deadly overheating conditions, and millions will be exposed to deadly infectious diseases such as malaria. 1-3 IPCC report indicates that global warming has accelerated, making it imperative to halt it at 1.5°C above preindustrial levels. 4 The surveys indicate that 99% of scientists believe human activity is the primary cause of global warming. 5 A significant contributing factor to global warming is the release of greenhouse gases caused by burning fossil fuels and gases produced by humans. [6][7][8][9] Based on the most recent reports by REN21 and Our World in Data, fossil fuels provide 80% of the required energy. 10, 11 The IEA Net Zero Emissions by 2050 Scenario proposes renewable energies as a solution to this crisis and reducing CO 2 emission, producing 90% of the required electricity from renewable sources such as solar and wind energy. 12 The highest rate of GHG production in Spain, like most countries, is in the energy production section. In 2018, it produced more than 76% of pollution equal to 325Mt. Electricity production alone is responsible for massive pollution in the energy industry. 13,14 Spain, a member of the IEA, is committed to generating 100% of its electricity from renewable sources and obtaining 97% of its energy mix from renewable sources. Accordingly, the Spanish government reduced its coal production to almost zero in 2019, an energy source upon which Spain heavily relied in 2010. In 2019, this country produced 37% of its electricity from renewable sources, including 21% from wind and 6% from solar energy. In 2025, the government is planning to impose companies a minimum cumulative power limit of 8500 MW for wind-generated power and 10,000 MW for solar-generated power. For both sources, the current target is 1000 mW. 13,15 Combining renewable energy sources, such as wind and solar energy, with hybrid systems allows for producing energy that is financially efficient, highly reliable, and capable of meeting any load requirements. These qualities cannot be achieved by any single renewable energy source. [16][17][18][19][20] This paper seeks to analyze the installation and techno-economic optimization of hybrid energy systems producing off-grid electricity in different regions for industrial areas, considering Spain's participation in pollution reduction programs. 21,22 2 | LITERATURE REVIEW The National Renewable Energy Laboratory (NREL) in the United States developed HOMER software to achieve the best technical form, lower investment capital, and produce less pollution for hybrid power plant installations. 18 Homer has been used by researchers to examine the feasibility of constructing hybrid plants in different regions characterized by varying weather conditions. For instance, several combinations of renewable hybrid systems were examined in Punjab, India, to produce electricity. HOMER results revealed that photovoltaic systems (PV)-Wind-Diesel-Battery provided greater power and reduced COE than other systems such as PV-Diesel-Battery, PV-Wind-Diesel, Wind-Diesel-Battery, Wind-Diesel, and PV-Diesel. 23 HOMER has been used in some studies in Morocco to produce 4874 kWh/month under various weather conditions to cover the electrical needs of public facilities. Therefore, the use of PV-Wind has been recommended for a 25-year project in the western regions of the country. 24 This procedure has also been adopted in six geographical regions of Nigeria to assess the feasibility of providing electricity for the outlands. The results have indicated that PV-diesel-battery systems produce less CO 2 and are technically and economically efficient. 25 After analyzing PV-wind-diesel batteries, HOMER's results in Southern Algeria suggest that fossil fuel usage should be reduced to 69% by leveraging wind and solar power to produce 70% of the required electricity. 26 Studies have been conducted continuously to determine the potential use of renewable resources in different climatic conditions. An educational facility in northeast Tripura, India, has incorporated wind topography alongside PV, the primary electricity source. A 90% fraction of the results indicated that wind was the backup source. 27 Wind systems, PVs, and diesel generators have been combined in industrial parks located in three different regions of Ethiopia. This is due to frequent power outages and the use of diesel generators as a primary source of critical loads for Ethiopian industries. Considering scheduled outages, the results suggested that diesel generators, PVs, and batteries are suitable for three distinct regions. 28 Electricity demand exists in all sectors, especially those with higher consumption, pollution production, and fuel shortages. There is a greater need for hybrid renewable energies in these sectors. In this regard, several studies have been conducted using HOMER software. A techno-economic analysis of providing industrial and residential power has been conducted in New Borg El-Arab City in Egypt in light of frequent power outages, particularly during peak consumption hours. The results suggested that combining solar-wind-diesel generators and batteries would significantly reduce CO 2 emissions. Moreover, compared with a single diesel generator, this combination was more environmentally friendly. 29 The pollution generated by diesel generators also causes discomfort in tourist areas. For instance, the South China Sea has been analyzed by HOMER regarding electricity provision, and it was found that a PV-Wind-Diesel-Battery system can generate an average of 1185 kW of electricity for a resort with a peak load of 13,048 kW. Compared with a single diesel generator, this system had a renewable fraction of 41.6%, which reduced CO 2 and COE by 0.343 to 0.279. 30 A PV-Wind and PV-Wind-Diesel system was analyzed for apartments with one, two, and three bedrooms in Jubail Industrial City, Saudi Arabia, with results demonstrating their economic efficiency. Utilizing these systems also reduced the amount of carbon dioxide produced annually. 31 Homer software was used to conduct a techno-economic analysis of Kish Island in the Persian Gulf, with an annual electric energy consumption of 2,628,000 kWh and a peak demand of about 620 kW. A combination of wind turbines and diesel generators yielded the most effective results. 32 An ORC cycle-based combinational energy system was analyzed to provide electricity for a residential area in Rayen, Iran. Nevertheless, due to high expenditures, HOMER analyzed seven combinations of renewable energies. 33 HOMER software has also been used numerous times to analyze nonresidential uses. The HOMER software considered the financial situation, the annual impacts of load, low-interest loans for renewable energy sources, carbon tax, and fluctuations in grid electricity costs. Results suggested that compared with the on-grid system with a COE of 53% and above, the off-grid system with an average renewable fraction of 0-43.9% showed a lower rate. 34 Desalination of seawater to produce drinking water is quite efficient in the outlands. The high demand for energy affects the consistency of desalination plants. Accordingly, two scenarios of hybrid PV-wind-diesel plants, one with and one without batteries, demonstrated that the PV-wind-diesel-battery system is the most efficient. 35 In selected Nigerian villages, the feasibility of using hybrid systems was analyzed to provide electricity for rural healthcare facilities without continuous access to electricity. HOMER prioritized PV-wind-diesel-battery hybrid systems for village healthcare facilities in Iseyin, Sokoto, Maiduguri, Jos, and Enugu. On the other hand, the PV-diesel-battery hybrid systems for Port Harcourt performed better. 36 In Dongola, Sudan, a combination of renewable energies was analyzed to provide electricity to agricultural areas. The results indicated that PV-wind-diesel-battery was the most appropriate combination of renewable energies. The financial results also demonstrated a 39.94% return on investment and a 95% reduction in fuel consumption. 37 Inaccessibility to electricity in rural areas has always been controversial in scientific congregations. Recently, off-grid renewable hybrid systems have been proposed as a feasible solution. In this light, numerous analyses have been conducted on this topic. PV-wind-diesel-battery systems have been installed in the outlying areas of KLIA Sepang Station, Selangor, Malaysia, to reduce the use of fossil fuels for electricity generation. HOMER analyses demonstrated a significant reduction in net present cost (NPC) and CO 2 emissions. 38 In Muhavoor, India, hybrid systems of various configurations were considered, including diesel, PVdiesel-battery, wind/diesel, and PV-wind-diesel-battery. Based on HOMER software, the system consists of a PV-diesel-batteries system with 53 MW of PV capacity, 16.55 MW of diesel generator capacity, 3520 MWh of battery backup, and 15.5 MW of converter capacity. An annual energy yield of 92,549 MWh was predicted with excess energy of 7262 MWh. 39 Several studies have been conducted around the world, recommending the use of these systems. Regarding recent concerns about climate change and Columbia's development plans, three villages were assessed and proposed with hybrid systems. These systems included combinations of wind turbines, solar panels, and diesel generators. 40 The essential resource after energy is water. Dhahran, Riyadh, Jeddah, Guriat, and Nejran have been analyzed as potential places to supply 100% renewable energy for water pumping in Saudi Arabia's off-grid regions. Homer software data demonstrated the efficiency of the PV-wind system. 41 Two main configurations were optimized in Sabah power stations in Malaysia, including PV-diesel-battery and PV-battery, by changing the main parameters, such as fuel, PV, battery price, and load demand. HOMER software indicated that the system used more renewable energy. PV-diesel batteries offered the highest performance, while PV-battery configurations provided the best environmental characteristics at a higher cost. 42 A study was conducted in Johor Bahru (the southern city of Malaysia) to analyze seven configurations combining wind turbines, PV panels, and diesel generators. The data was used to examine current expenditures, energy costs, additional electricity produced, and the reduction in energy consumption. Finally, both PV-diesel-battery and PV-wind-diesel-battery systems were compared with the high-cost diesel system. 43 Furthermore, a techno-economic analysis was conducted in Indonesia to determine the appropriate size and cost of hybrid solar-wind systems on outlying shorelines. The study indicated that a 1kw wind turbine would produce 496 kW of electricity annually, whereas a PV panel of the same size would produce 2079 kW annually. Since nighttime power demands are high, wind turbines and batteries were suggested as essential components. 44 Using several HRES to supply electricity to the outlands is an efficient approach. An in-depth analysis of this system was conducted in Chaghi-Baluchestan, which led to valid conclusions. 45 Homer software was used to conduct a feasibility study in North America and Canada considering seven hybrid system scenarios, including PV-wind-batterydiesel supplying 21%, 35%, 50%, 65%, 80%, and 100% of electricity from renewable sources as well as diesel and batteries. According to the report, electricity costs per kW were 0.36, 0.37, 0.39, 0.42, 0.54, 0.62, and 1.148, respectively. 46 A variety of renewable energy sources are utilized to generate power for outlands, taking into account the region's potential. HOMER software and GA algorithms were used to analyze an off-grid system. According to the results, the most efficient fuel combination was the combination of biogas and biomass-solar-wind-battery cells. Moreover, the cost of electricity generation in three different villages in Kollegal block of Chamarajanagar district, Karnataka State in India, was only 0.163 dollars/kW. 47 Various scenarios were assessed to deliver domestic, industrial, and agricultural BTS loads in Kadayam, a remote village in Tamil Nadu, South India, and PV-windhydro-battery proved the most efficient combination. 48 Furthermore, a PV-biomass-hybrid system was used to provide electricity to Kallar Kahar's residents near Chakwal, Punjab province of Pakistan. HOMER software was used for optimizations, financial efficiency, and stability recommendations. 49 3 | METHODOLOGY Figure 1 depicts hybrid systems optimization methods, designed using HOMER software. In the flowchart, entries are described to achieve desired results.

| Technical analysis
The HOMER software uses equations to calculate the technical calculations necessary for each component.

| Wind turbine
HOMER uses Equation (1) to determine the wind speed at the hub height 50 : where U hub is the wind speed at wind turbine hub height (m/s), U anem refers to the wind speed at the height of the anemometer (m/s), Z hub is also the wind turbine hub height (m), Z anem is the height of the anemometer (m) (the height of the anemometer is the height above the ground where the wind speed information is measured), and Z 0 is the roughness length of the surface (m). First, the software determines the wind speed at the hub height to calculate a wind turbine's power at the standard density of air. Then, it is adjusted to the wind turbine power curve to determine power compared with velocity. No power is generated when the velocity is outside the range of the power curve. This phenomenon may occur at velocities that fall outside the range of the turbine. The power curve is typically used to determine the power output at standard pressure and temperature. This is calculated by HOMER software by multiplying the predicted power estimated by the power curve by air density, according to the following equation: where P WTG is the power output of the wind turbine (kW), P WTG,STP is equal to the power output of the wind turbine at standard pressure and temperature (kW), ρ indicates the density of air (kg/m 3 ), and ρ 0 represents the density of air at standard conditions (1.225kg/m ) 3 .

| Photovoltaics
HOMER uses Equation (3) to calculate the power output of the PV array 50,51 : Accordingly, Y PV is equal to PV array-rated capacity, indicating a power output kW under standard test conditions. f PV stands for the PV derating factor (%), Ḡ T is the solar radiation incident on the PV array in the current time step (kW/m 2 ). Ḡ T,STC shows the incident radiation at standard test conditions (kW/m 2 ), α P is equal to the power temperature coefficient (%/°C). T c,STC is also the PV cell temperature under standard test conditions (25°C), and the temperature of the PV cell at the current time step is denoted by T c (°C).

| Inverter
A power inverter is used in systems to convert DC power to AC power, and Equation (4) was used to calculate efficiency: where η inv is the inverter efficiency, and P inv,out is the power output of the inverter (kW).

| Battery (charge and discharge)
Equation (5) is used to calculate the capacity of the battery B .
where D ele is the daily electricity demand in (kWh/day), D d is the battery's depth of discharge (DoD), N a is the daily autonomy, and η b and η inv are the efficiencies of the battery and converter, respectively.

| Generator
Generators' technical calculations consider fuel type and the associated power curve, outages, and emission penalties. HOMER determines the electricity efficiency average of the generator using the following equation 50 : ·LHV , gen gen fuel fuel (6) where E gen is the total annual electricity output of the generator (kWh/year), m fuel refers to the total annual fuel usage of the generator (kg/year) and LHV fuel represents the lower heating value of fuel (MJ/kg). The number 3.6 in the equation above comes from the fact that one kWh equals 3.6 MJ.
Equation (7) is suggested to determine the CO 2 emission 38 : where tCO 2 is the number of CO 2 emissions, m f the fuel quantity (L), HV f represents the heating value of the fuel (MJ/L), CEF f is the carbon emission factor (Tonecarbon/ TJ), and X c is the fraction of carbon oxidized (FCO). It is F I G U R E 2 Six different climate zones in Spain.
F I G U R E 3 Monthly average of wind speed in different cities of Spain.
also important to note that 3.667 g of CO 2 contains 1 g of carbon.

| Renewable fraction
The delivered energy ratio generated by renewable energies is called the renewable fraction, and it is calculated by HOMER software according to the following equation: ren nonren nonren served served (8) where E nonren is the nonrenewable electricity production (kWh/year), H nonren the nonrenewable thermal | 2837 production (kWh/year), and E served is the total electrical load served (kWh/year). E grid,sales is the energy sold to the grid (kWh/year) (included in E served ), which is zero in off-grid systems. H served is the total thermal load served (kWh/year).

| Economic analysis
The following methods are used by HOMER to analyze financial values. 43,50 3.9 | Real discount rate The real discount rate is applied to convert between one-time and annualized costs. To determine the annual real discount rate (also known as the real interest rate or simply interest rate), HOMER uses the following equation : where i represents the real discount rate, i′ is the nominal discount rate, and f is the expected inflation rate.

| NPC
NPC represents the cost of installation and system booting throughout the lifetime of the project. It is also known as life-cycle costing. This parameter determines the priority and classification of optimization and HOMER responses. It can be calculated using the following equations: where C ann,tot is the total annualized cost ($/year), which is the sum of capital, replacement, operation and maintenance costs. The capital recovery factor (CRF) is a formula used to determine the current value of a sequence of equal annual cash flows. The real interest rate (%) is i, and the project lifetime (%) is N .

| Levelized cost of energy (LCOE)
LCOE indicates the average cost of electricity generated by the system per kilowatt ($/kWh), which can be calculated by the following equation: ann,tot prim,AC prim,DC where C ann,tot is the total annualized cost ($/year), E prim,AC is the AC primary load served, and E prim,DC is the DC primary load served (kWh/year).

| Different climatic zones
It is interesting to conduct feasibility studies for installing renewable energy hybrid systems in Spain because of its diverse weather conditions. Figure 2 illustrates the weather map of Spain. 52 A study is conducted in six different climatic zones, providing an in-depth look at the industrial sectors of cities and the establishment of hybrid power generation systems. Moreover, their exact geographical locations are as follows: Almería (36°50. 1′N

| Wind and solar energy data resources
Data on the climate of different areas were extracted from NASA's surface meteorology and solar energy database. Figures 3 and 4 show the daily radiation and average wind speed for the cities mentioned above. 53,54 Figure 3 illustrates the average wind speed of selected cities in Spain at different months of the year. For example, the city of A Coruña has the highest average wind speed, so it can be assumed that it has more potential to utilize wind energy to supply the requested load. There can be no generalization about the superiority of other cities. The highest average wind speed in the country can also be seen in December and January. Figure 4 also shows the average global horizontal irradiance (GHI) in different months of the year. Radiation is at its peak during June and July. The figure also illustrates which cities have the greatest potential for utilizing solar energy.

| Loads profile
The demand for electricity in industrial townships has been examined in two sections. The majority of industrial loads are required in factories and industrial towns. 1500 kW of constant load per hour has been specified. A daily average load of 1500 kWh is anticipated, with a peak demand of 114.58 kW for the system. Figure 5 depicts the required load profiles for daily, seasonal, and yearly demands. It should be noted that industrial complexes may include residential and administrative buildings whose load requirements are considered residential with the relevant use ratios, such as peak demand. In Figure 6, daily, seasonal, and yearly bar profiles show an average load of 150 kwh/d and a peak demand of 27.85 kW. The selected annual averages for industrial and residential loads are 1500 kWh/d and 150 kWh/d, respectively. This indicates that HOMER divides the selected annual average by the baseline average. 55 Depending on the conditions in Spain, hybrid systems are selected and priced accordingly. Analyses of financial situations and related quantities also play a crucial role.

| Economic input
For Spain, the average inflation rate after the year 2000 was calculated. The rate was estimated to be 1.98%, but we considered 2% with a higher degree of confidence. 56 A safe discount rate is essential for ensuring a return on investment. Accordingly, 8% seems an appropriate rate, as indicated by statistical data and empirical evidence from projects in Spain and Europe using hybrid renewable energy systems, such as wind turbines and PV. These parameters are relatively sensitive and have a significant impact on the final financial results. 57-59

| Equipment input and hybrid configuration
The main equipment of renewable hybrid systems is as follows: The EO10 Class III model of wind turbines and generic flat-plate photovoltaic panels are used in a hybrid system to produce clean electricity. A diesel generator serves as a backup source of electricity generation. In addition, the F I G U R E 12 Renewable fraction of different system combinations in different Spain cities. system incorporates a Rolls-Surrette 6 CS 25 P battery and inverter. Tables 1 and 2 present the techno-economic components, and Figure 7 illustrates the power curve for wind turbines and diesel generator efficiency. Figure 8 illustrates the schematics of the hybrid system combination based on the selected equipment. Table 3 shows the optimized status of the system in different cities based on all conditions analyzed by HOMER. In addition, it provides a list of the necessary components for installing the system in each city.

| RESULT AND DISCUSSION
Each component has its work hours and electricity generation. Figures 9 and 10 illustrate the share of electricity produced by each section. It is evident that the hybrid system prioritizes the use of all components.
The share of renewable energies in each city's electricity production is directly related to the resources available in that city. As an example, the wind speed in A Coruña is high on average. Accordingly, the share of electricity generated by wind turbines increased due to this predominance of renewable sources. This can be observed in almost all cities. The results indicate that Almeria generates most (63.5%) of its electricity using wind power. While Barcelona relies primarily on wind and solar energies to F I G U R E 14 Net present cost (NPC), initial capital, and operating costs for different cities in Spain.
F I G U R E 15 Cost of energy (COE) in different system combinations in different cities in Spain. ABBASPOUR ET AL. produce its electricity (47.5% and 48.2%, respectively), Seville mainly uses solar energy (58.7%). In addition, Madrid produces 60% of its electrical load from solar power. Most of Zaragoza's electricity needs are met by solar energy (58.4%). In Salamanca, wind power is used more than solar power (49.1% wind power and 45.3% solar power). By converting wind energy into electricity, Ponferrada has managed to generate considerable amounts of electricity (82.2%). Additionally, Bilbao generates 86.2% of its electricity needs through wind energy, which is right behind Acoruna, where wind energy is the predominant source of electricity (96.9%). Considering the share of renewable electricity generators compared with diesel generators, the renewable fraction parameters or shares of renewable energies from the total generated electricity for Almeria, Barcelona, Seville, Madrid, Zaragoza, Salamanca, Ponferrada, Bilbao, and A Coruna are 94.3%, 94%, 92%, 89%, 91.4%, 92.1%, 94.9%, 95%, and 95.2%, respectively ( Figure 11).
HOMER has analyzed different combinations of hybrid and standalone systems considering various components. To facilitate the selection of the most suitable combination, Figure 12 illustrates renewable fractions in different cities.
Compared with non-diesel systems, hybrid systems that utilize all renewable energy sources have the highest rate of renewable energy use. It is also noteworthy that this system is financially efficient. Table 4 illustrates the financial optimization status of the system installed in various cities. Figures 13 and 14 show various economic values in different regions. Also, the cost to produce each kilobyte of electricity, the NPC, initial capital, and the system's operating costs are displayed. Moreover, Figure 15 shows the COE of various combinations in different cities to provide a comparative economic analysis and demonstrate the benefits of hybrid systems that utilize all components simultaneously.
The lowest cost of electricity production is associated with hybrid systems that employ all components. Based on the HOMER priority determined by NPC optimization, Figure 16 illustrates the amount of this parameter for different combinations of systems in different cities. This analysis can be beneficial in selecting the most appropriate system. Table 5 shows that the PV-wind-diesel-battery system is the most optimal system configuration in all investigated sites except A Coruña, which is the most optimal hybrid renewable system due to its high wind potential. On the other hand, all hybrid renewable systems are more optimal than diesel-only systems in terms of COE. Based on COE and NPC, the wind-dieselbattery and the PV-wind-diesel-battery configurations are the most efficient hybrid renewable configurations for A Coruña and Bilbao, respectively. However, Madrid has the least optimal hybrid renewable configuration. The diesel-only system with the highest COE and NPC (more than three times the optimal configuration) is the most nonoptimal system in energy supply. The implications of this finding are not only limited to NPC, COE, energy production, and fuel savings but also include emissions of polluting gases and the health risks associated with them.
Being environmentally friendly is a major reason for installing hybrid plants with a high share of renewable energy. A calculation of the annual pollution generated by the system in each city has been conducted, with CO 2 F I G U R E 16 Net present cost (NPC) in different system combinations in different cities in Spain.
T A B L E 5 Comparison of various system configurations in the selected sites. holding the highest share of the optimized software response ( Figure 17). The results shown in Table 6 illustrate the annual pollutant emissions from the most optimal configurations at all sites. These pollutant emissions include carbon dioxide (CO 2 ), carbon monoxide (CO), unburned hydrocarbon (UHC), particulate matter (PM), sulfur dioxide (SO 2 ), and nitrogen oxide (NO x ). In diesel-only systems, annual CO 2 emissions are 526,166 kg/year. Therefore, the reduction in CO 2 production at the investigated sites ( According to the configuration of the hybrid energy system and optimization results, the proposed hybrid energy system includes limitations. Due to the space and land area limitations, the maximum number of equipment such as wind turbines and photovoltaic panels should be considered, for example, equipment with a higher capacity can be used to occupy less space.
The complicated controlling process is another limitation. Because different sources of energy are used, the operation of different energy sources and the interaction between them can become complicated. Also, because the proposed energy system is off-grid, the number of components has increased and components such as batteries that work continuously will have a shorter operational life. 16

| CONCLUSION
Spain's climate varies greatly from region to region, and it is currently reliant on renewable energy sources for generating its electricity needs. As a result, it has become a target for investment in this field. It has also been known as the fifth country to harness wind energy. 60 This study examined the techno-economic and environmental feasibility of installing hybrid power plants including wind turbines, photovoltaic panels, diesel generators, and batteries to provide electricity for offgrid industrial and residential areas in various climate regions. Following is a summary of the main findings of the study:  the other hand, a hybrid system involving wind-dieselbattery is considered ideal in A Coruña, due to the high wind resources availability compared with other locations. Its NPC and COE values are, respectively, 1.39 M$ and 0.199 $/kWh. In all cities, simulation results indicate that the hybrid system configuration is the most efficient compared with diesel-only systems. Therefore, the results of the article for three cities such as A Coruña, Bilbao, and Madrid, are of considerable relevance. In terms of COE and NPC rates, A Coruña has the most optimal rates for Wind-Diesel-Battery hybrid systems. As far as PV-wind-diesel-battery hybrid systems are concerned, Bilbao has the highest rates for such systems, and Madrid is the least efficient for such projects, with the highest COE and NPC rates. 2. In most cities, hybrid systems are proposed for most components. Resources, weather data, equipment input, project conditions, and economic parameters indicate that Madrid supplies most of its load (60.5%) through solar power due to its high solar potential. Bilbao provides the majority of its electricity using wind turbines (82.2%), as it has a high wind potential among the cities that use hybrid renewable energy systems. Almería supplies most of its electricity from wind energy (63.5%), Barcelona generates its electricity almost equally from wind and solar power (47.5% wind and 48.2% solar), and Seville relies heavily on solar power (58.7%). Salamanca relies more on wind energy than solar energy (49.1% wind and 45.3% solarPonferrada and A Coruña receive the majority of their electricity from wind power (82.2% and 96.9%, respectively). Cities with an oceanic climate, which cover the northern part of Spain and are very close to the sea, are excellent candidates for wind turbine installation. In contrast, the mountain climate is suitable for wind power generation. On the other hand, most Mediterranean climate cities that make up the south and east of Spain can provide a high share of their electricity production from solar energy and panels. In coastal cities such as Barcelona, the share of electricity generated by wind turbines can be very comparable to that generated by solar panels. In cities with a continental climate, which covers most of central Spain, optimization is preferred over additional PV panels because the average wind speed is lower in the central regions. Nevertheless, it is important to note that wind energy is more prevalent near the borders of the country, such as in North and F I G U R E 17 The amount of CO 2 produced by the optimal hybrid system in different cities in Spain.
T A B L E 6 Comparison of emission in optimal system configuration and diesel-only system in the selected sites.