Energy supply for water electrolysis systems using wind and solar energy to produce hydrogen: a case study of Iran

Abstract

Due to acute problems caused by fossil fuels that threaten the environment, conducting research on other types of energy carriers that are clean and renewable is of great importance. Since in the past few years hydrogen has been introduced as the future fuel, the aim of this study is to evaluate wind and solar energy potentials in prone areas of Iran by the Weibull distribution function (WDF) and the Angstrom-Prescott (AP) equation for hydrogen production. To this end, the meteorological data of solar radiation and wind speed recorded at 10 m height in the time interval of 3 h in a five-year period have been used. The findings indicate that Manjil and Zahedan with yearly wind and solar energy densities of 6004 (kWh/m²) and 2247 (kWh/m²), respectively, have the greatest amount of energy among the other cities. After examining three different types of commercial wind turbines and photovoltaic (PV) systems, it becomes clear that by utilizing one set of Gamesa G47 turbine, 91 kg/d of hydrogen, which provides energy for 91 car/week, can be produced in Manjil and will save about 1347 L of gasoline in the week. Besides, by installing one thousand sets of X21-345 PV systems in Zahedan, 20 kg/d of hydrogen, enough for 20 cars per week, can be generated and 296 L of gasoline can be saved. Finally, the RETScreen software is used to calculate the annual CO₂ emission reduction after replacing gasoline with the produced hydrogen.

Keywords

wind energy / solar energy / water electrolysis / hydrogen production / Weibull distribution function (WDF) / Angstrom-Prescott (AP) equation

Introduction

In recent years, hydrogen has become one of the most popular means of providing energy for different purposes like transportation, while it has a few drawbacks including being much less dense than other fuels, and difficult to store and transport. On the other hand, hydrogen benefits from the high energy density which is between 120 and 142 MJ/kg (almost three times higher than that of oil) and practically produces no greenhouse gas (GHG) emissions [¹,²]. In general, its shortcomings can be considered almost negligible in comparison with its merits which have encouraged many countries to view hydrogen as an alternative fuel for vehicles [³]. To reduce GHG emissions and mitigate their consequences, such as global warming and environmental pollution, it is required to stop using fossil fuels and embark on utilizing clean energy sources to address the demand for energy. Hence, hydrogen generation is of significant importance.

There are several methods for producing hydrogen including fermentation [⁴], natural gas reforming/gasification [⁵], high-temperature water splitting [⁶], ethanol reforming [⁷], and water electrolysis, of which the chief one is the latter [⁸,⁹]. To keep the process of hydrogen generation clean, renewable resources of energy can be used as electricity supply. Therefore, in this research to supply the electric energy needed for the water electrolysis process, it is suggested to use wind and solar energies which neither cause air pollution nor have the problem of depleting [¹⁰].

Given significant importance of energy and its impact on the world, extensive studies have been conducted to scrutinize different aspects of this controversial subject. In this regard, clean means of generating hydrogen as an alternative fuel using wind and solar energy have been studied. In terms of using solar energy to produce hydrogen, Badea et al. [¹¹] examined three different scenarios pertaining to the sub-systems of the hydrogen production and storage system efficiency. The results showed that to maximize solar/hydrogen conversion, it was necessary to use both electrical energy and thermal energy in the form of steam. Likkasit et al. [¹²] investigated the different methods for solar-based hydrogen production and concluded that solar steam methane reforming using a volumetric receiver reactor had the lowest cost of hydrogen production. Other studies done in Algeria [¹³], Jordan [¹⁴], Lebanon [¹⁵] and Australia [¹⁶] showed the importance of utilizing solar energy for hydrogen production.

As regards hydrogen generation using wind energy, GarcíaClúa et al. [¹⁷] investigated a wind-powered system to produce hydrogen through water electrolysis and the effect of the size of electrolyzer on minimizing carbon emissions. In another research done by Sarrias-Mena et al. [¹⁸], four electrolyzer models for hydrogen production using wind energy were analyzed and compared under variable wind velocity. Douak and Settou [¹⁹] examined economic feasibility of 4 wind turbines as input of a water electrolysis system to produce hydrogen in Algeria. The results indicated that the turbine with the rated power of 1500 kW was the most economic one to be used.

Since hybrid systems benefit from significant advantages including improvement in the reliability of the whole system, decrease in cost of implementation and maintenance, and reduction in GHG emissions [²], utilizing at least two types of renewable energies as the input of a hydrogen production system is advantageous. In this regard, Kalinci et al. [²⁰] assessed the techno-economic feasibility of a hybrid wind/solar to hydrogen conversion systems. The results showed that being hybrid could result in a dramatic reduction in current net costs. Blal et al. [²¹] also scrutinized a system for generating hydrogen in Algeria using wind and solar energy as a hybrid system. In another research, Marchenko and Solomin [²²] investigated a system for producing electricity as well as hydrogen by applying PV systems along with wind turbines and found that generating electricity storage is most efficient for short-term time intervals while an increase in the duration of continuous energy “standstills” up to several days makes the storage of hydrogen more cost-effective. In a study done in Saudi Arabia, Al-Sharafi et al. [²³] examined different combinations of wind turbines, PV array, batteries and fuel cells in order to find the most cost effective one for power generation and hydrogen production and finally proposed a system with 2 kW PV array, 3 wind turbines, 2 kW converter, and 7 batteries as the best configuration leading to the minimum levelized cost of energy.

Several studies have been conducted in Iran in terms of producing hydrogen using renewable energies such as prioritization of cities of Kerman province for exploiting solar energy to generate hydrogen [²⁴], ranking different cities of Fars province to produce hydrogen using wind energy [²⁵], evaluating wind energy potential for generating hydrogen [²⁶] and socio-economic assessment of hydrogen production using wind energy [²], but these studies are lacking in investigating hydrogen as a fuel for the transportation sector in Iran. Hence, in this study, a renewable-powered system which generates hydrogen via water electrolysis using wind and solar energy is proposed in order to achieve sustainable development in the transportation sector in Iran. What makes this research essential for Iran as well as other developing countries is that no research on using hydrogen cars has been conducted in order to reduce environmental pollution. Therefore, an attempt should be made to close this research gap. Finally, the most important novelties of this work are using electricity generated via wind and solar energy to produce hydrogen in Iran, proposing a green and renewable process to produce hydrogen for transportation purposes, calculating the amount of hydrogen that can be gained in different cities of Iran using wind and solar energy, and estimating CO₂ emission reduction due to using hydrogen for cars instead of gasoline.

Renewable energy sources in Iran

Wind energy in Iran

Due to the special geographic situation of Iran and its location which is situated in low-pressure area with flowing strong air in summer and winter in some locations, this country has very good wind energy potential in many zones. In winter, the country is influenced by the winds from the Atlantic Ocean, the Mediterranean Sea, and central Asia while in summer it is influenced by the winds from the Indian Ocean and the Atlantic Ocean [²⁷,²⁸].

In a study done by the Renewable Energy Organization of Iran, locally called SUNA, it is mentioned that in 26 zones of the country including 45 sites, the wind energy potential is estimated to be about 6500 MW [²⁸].

Considering the wind atlas and long-term wind speed data pertaining to 15 years from 2000 to 2014 provided by SUNA, it was specified that the cities given in Table 1 had the highest mean wind speed during this period. As a result, in this study these cities are investigated in terms of harnessing wind energy for hydrogen production through water electrolysis.

Solar energy in Iran

Some regions of Iran are the most suitable areas in the world in terms of receiving solar radiation and enjoying a long sunshine of almost over 2900 h/a. Thus, solar energy could be utilized to meet a significant share of energy demand in the near future. According to the findings of solar energy experts, more than two-thirds of Iran has 300 sunny days in a year, receiving solar energy of between 4.5 and 5.4 kWh/(m²∙d) [²⁸].

According to the solar radiation map, the central and southern parts of Iran have a high potential for harnessing solar radiation. In this study, top 10 of the most appropriate cities in terms of solar radiation, mentioned in Table 2, were chosen for further investigation because these cities are located in the areas with relatively higher solar radiation.

Methodology

In this section, wind energy is calculated using WDF, solar energy is estimated using the AP equation, and hydrogen generation through water electrolysis by applying the proposed system is discussed.

Wind energy

It is essential to calculate the wind power density at the height of wind turbine blades, because wind velocity varies by different heights and this variation in wind speed will definitely change the results of estimating wind energy [²⁵]. Since the turbines used commercially in Iran have a height of 40 m, this height is considered for calculations in this study. As the three-hourly data collected from Iranian Meteorological Organization (IMO) pertains to the height of 10 m, the wind velocity at the turbine tower (height of 40 m) must be computed by extrapolation using Eq. (1). Among variables including wind speed, air temperature and air pressure necessary to estimate wind power density, two last ones do not change for the heights less than 100 m from the ground surface [²⁵].

(1)V=V_{\mathrm{0}}{\left({\displaystyle \frac{h_{\mathrm{1}}}{h_{\mathrm{0}}}}\right)}^{\alpha },

where V is the wind speed at the height of h₁, V₀ is the wind speed at the height of h₀, which is 10 min this study. The coefficient α is calculated by Eq. (2) [²⁵].

(2)\alpha ={\displaystyle \frac{[\mathrm{0.37}-\mathrm{0.088}\ln (V_{\mathrm{1}}\left)\right]}{[\mathrm{1}-\mathrm{0.088}\ln ({\displaystyle \frac{h_{\mathrm{1}}}{h_{\mathrm{0}}}}\left)\right]}}.

Then, WDF which is the most common method is used to calculate wind power density. This distribution is shown in Eq. (3) [²⁵].

(3)f\left(v\right)=\left({\displaystyle \frac{k}{c}}\right){\left({\displaystyle \frac{V}{c}}\right)}^{k-\mathrm{1}}{\mathrm{e}}^{-{\left(\frac{v}{c}\right)}^k},

where the two fixed parameters c and k are the scale parameter and shape parameter, which must first be obtained from Eqs. (4) and (5) [²⁹].

(4)k={\left({\displaystyle \frac{{\sigma }_v}{\overline{v}}}\right)}^{-\mathrm{1.086}},

(5)c={\displaystyle \frac{\overline{v}}{\mathrm{\Gamma }\times (\mathrm{1}+{\displaystyle \frac{\mathrm{1}}{k}})}},

where \overline{v} and σ_v are the mean and standard deviation of wind speed, and Г is the gamma function whose general relationship is expressed in Eq. (6) [²⁹].

(6)\mathrm{\Gamma }\left(x\right)={\displaystyle {\int }_{\mathrm{0}}^{\infty }}{\mathrm{e}}^{-u}{u}^{x-\mathrm{1}}\mathrm{d}u.

Finally, the general equation of wind power is given in Eq. (7), in which \rho is the density of air, which is calculated by Eq. (8) [²⁵].

(7)P\left(v\right)={\displaystyle \frac{\mathrm{1}}{\mathrm{2}}}\rho A{v}^{\mathrm{3}},

(8)\rho ={\displaystyle \frac{\overline{P}}{R_{\mathrm{d}}\overline{T}}},

where \overline{P} is the average air pressure in Pascal (Pa), \overline{T} is the average air temperature in Kelvin (K), and R_d denotes the gas constant for dry air which equals 287 J/(kg∙K) [³⁰]. After these preliminary calculations, the wind power density for the area swept by turbine blades, shown by A, can be gained by Eq. (9) [³¹].

(9){\displaystyle \frac{P}{A}}={\displaystyle {\int }_{\mathrm{0}}^{\infty }}{\displaystyle \frac{\mathrm{1}}{\mathrm{2}}}\rho v^{\mathrm{3}}f\left(v\right)\mathrm{d}v={\displaystyle \frac{\mathrm{1}}{\mathrm{2}}}\mathrm{\Gamma }\rho c^{\mathrm{3}}(\mathrm{1}+{\displaystyle \frac{\mathrm{3}}{k}}).

Then, the wind energy density available in each region is computed by Eq. (10) [²⁵].

(10){\displaystyle \frac{E}{A}}=\left({\displaystyle \frac{P}{A}}\right)\times n\times \mathrm{\Delta }t={\displaystyle \frac{\mathrm{1}}{\mathrm{2}}}\mathrm{\Gamma }\rho c^{\mathrm{3}}(\mathrm{1}+{\displaystyle \frac{\mathrm{3}}{k}})\times n\times \mathrm{\Delta }t,

where n is the number of observations, and \mathrm{\Delta }t is the difference of time intervals in which the data were measured.

The amount of electricity produced by utilizing wind turbines is obtained from Eq. (11) [²⁶].

(11)E_{\mathrm{out}}=N_{\mathrm{tb}}\times C_{\mathrm{tb}}\times C_{\mathrm{f}},

where N_tb is the number of turbines installed (In this paper, the amount of energy obtained from one turbine is evaluated.), C_tb is the nominal capacity of the turbine, and C_f is the capacity factor of the turbine, which is calculated by Eq. (12) [²⁶].

(12)C_{\mathrm{f}}={\displaystyle \frac{P_{\mathrm{out}}}{P_{\mathrm{r}}}}={\displaystyle \frac{{\mathrm{e}}^{-{(v_{\mathrm{i}}/c)}^k}-{\mathrm{e}}^{-{(v_{\mathrm{r}}/c)}^k}}{{(v_{\mathrm{r}}/c)}^k-{(v_{\mathrm{i}}/c)}^k}}-{\mathrm{e}}^{-{\left(\frac{v_{\mathrm{o}}}{k}\right)}^k},

where v_i, v_r, and v_o are the cut-in speed, rated speed, and cut-out speed, respectively.

Solar energy

One of the common methods for estimating the solar energy available in an area is the AP equation. Parameters n and N are needed for this purpose, which denote the actual sunny hours and the maximum possible hours of sunshine per day, respectively. N is a function of latitude and is obtained by Eq. (13) [³²].

(13)N={\displaystyle \frac{\mathrm{2}\omega }{\mathrm{15}}},

where \omega is the monthly mean sunrise hour angle. Another parameter that must be calculated is the average daily extraterrestrial irradiance (\overline{H_{\mathrm{0}}}) computed by Eq. (14) [²⁸].

(14)\overline{H_{\mathrm{0}}}={\displaystyle \frac{\mathrm{24}\times I_{\mathrm{s}\mathrm{o}}}{\mathrm{\pi }}}\times [\mathrm{1}+\mathrm{0.033}\cos ({\displaystyle \frac{\mathrm{360}d}{\mathrm{365}}}\left)\right]\times [\cos \varphi \cos \delta \sin \omega +{\displaystyle \frac{\mathrm{\pi }\omega }{\mathrm{180}}}\sin \varphi \sin \phi ].

In this equation, I_so is the solar constant which equals 1367 W/m², d denotes the average day of each month, \varphi is the latitude of the location [²⁸,³²], \delta is the declination of the sun’s orbit which moves between the orbits of 23.5 North and South degrees during the year and is calculated by Eq. (15) [³³].

(15)\delta =\mathrm{23.45}\times \sin \left[{\displaystyle \frac{\mathrm{360}(\mathrm{284}+d)}{\mathrm{365}}}\right],

where \omega is the sunrise hour angle which shows the sun’s position in the sky of each location relative to the meridian of the same place [³⁴], the amount of which is 15 degrees for each hour difference to the solar noon (12 solar hour), and it is assumed to be negative in a.m. hours and positive in p.m., and is calculated by Eq. (16) [²⁸].

(16)\cos \omega =-\tan \varphi \times \tan \delta .

The amount of solar energy reaching the surface of the ground can be obtained by Eq. (17), the unit of which is MJ/m² [³³].

(17)\overline{H}=\overline{H_{\mathrm{0}}}\times (a+b\times (\frac{n}{N}\left)\right).

where a and b are fixed regression coefficients which are dependent on geographic and climatic parameters. a can be defined as the fraction of the monthly average solar radiation ({\displaystyle \frac{\overline{H}}{\overline{H_{\mathrm{0}}}}}) entered to the atmosphere when the cloud cover is complete and b can be defined as the changes in {\displaystyle \frac{\overline{H}}{\overline{H_{\mathrm{0}}}}} according to {\displaystyle \frac{n}{N}} and the latitude difference index [²⁸]. Before evaluating \overline{H}, the average daily extraterrestrial irradiance (\overline{H_{\mathrm{0}}}) should be calculated. Thus, d and \delta are extracted from Table 3 [³⁵] and used in related equations.

Equation (18) is used for calculating the amount of electricity (kWh/a) produced by installing PV systems [³⁶,³⁷].

(18)E_{\mathrm{out}}=A\times r\times \overline{H}\times \mathrm{PR}.

In this equation, A is the total area of solar panels, r is the efficiency of the solar modules (depending on the type of PV system), \overline{H} denotes the average annual radiation on solar panels (shadings not included), PR is the performance rate obtained from all wastes in PV systems (PR= 1–sum of losses shown in Table 4). The performance rate of PV systems depends on the solar site location, the technology used, and the size of the system installed [³⁸]. Thus, in this study, two scenarios, including the worst-case scenario (with the largest losses of 85%) and the best conditions (with minimal losses of 45%) are evaluated.

Hydrogen production system

Water electrolysis was first introduced by Michael Faraday in 1820. In this process electricity is passed through a solution containing water and electrodes. Then, hydrogen and oxygen molecules (H₂ and O₂) are produced from water [³⁹]. In other words, the negative and positive poles are connected to cathode (negative electrode) and anode (positive electrode), respectively. In the anode, the tendency is to pull electrons, and therefore the cathode tends to attract protons [⁴⁰]. Since water has a poor electrical conductivity, the electrolyte is added in the process [³⁹].

Electricity makes water molecules which are around the cathode electrode, separates and produces OH^– and H⁺ ions. This makes the external surface of cathode become totally covered by hydroxide ions (OH^–). Naturally hydroxide ions move toward the anode in order to reach its surface. The anode retakes excessive electrons which hydroxide ions have taken from hydrogen, and the hydroxide ion forms an oxygen gas molecule (O₂) again with three other hydroxide molecules, and gives two water molecules (H₂O). Oxygen molecules are stable and come to the water surface as bubbles. On the other hand, the H⁺ ion lacking electron and moving toward the cathode collides with extra e^– and forms H, then a hydrogen gas molecule is generated and finally comes out of the water surface as a bubble [⁴¹,⁴²]. This process is shown in Eq. (19) [⁴¹].

(19){\mathrm{H}}_2\mathrm{O}\stackrel{\mathrm{Electricity}}{\to }{\mathrm{H}}^{+}{\mathrm{+OH}}^{-}

{\mathrm{4OH}}^{-}\to {\mathrm{O}}_2+{\mathrm{2H}}_2\mathrm{O}+{\mathrm{4e}}^{-}

{\mathrm{H}}^{+}+{\mathrm{e}}^{-}\to \mathrm{H}

\mathrm{H}+\mathrm{H}\to {\mathrm{H}}_2

In this research, in order to produce hydrogen, a stand-alone wind-solar/hydrogen energy conversion system is proposed (Fig. 1). The system consists of a wind turbine (with AC voltage at its output), a PV panel (with DC voltage at its output), two converters, a water electrolyzer, and a control system. After reducing the output voltage of the wind turbine to a lower value, it can be used to supply the considered electrolyzer. Finally, the electrolysis of water occurs using the low voltage/high current, and hydrogen is produced. The final step is to store the produced hydrogen in the storage [²⁵].

The amount of hydrogen produced is calculated by Eq. (20) in N∙m³ [²⁵].

(20){\mathrm{H}}_{\mathrm{2}}=\left({\displaystyle \frac{E_{\mathrm{out}}}{E_{\mathrm{con}}}}\right)\times ef{f}_{\mathrm{con}},

where E_out is the amount of energy generated after applying wind turbines or PV systems, eff_con is the rectifier efficiency, and E_con is the amount of energy consumed by the electrolyzer. In this study, a rectifier with the efficiency of 95% and an electrolyzer with the energy consumption of 5 kWh/(N∙m³) were considered. Equation (21) is used to convert N∙m³ to kg [³⁹].

(21){\mathrm{kg=N\times m}}^3\mathrm{\times (}{\displaystyle \frac{1\hspace{0.17em}\mathrm{mol}}{0\mathrm{.022414}\hspace{0.17em}\mathrm{N}\cdot {\mathrm{m}}^3}}\mathrm{)\times (}{\displaystyle \frac{0\mathrm{.002016}\hspace{0.17em}\mathrm{kg}}{1\hspace{0.17em}\mathrm{mol}}}).

Calculation

Hydrogen production using wind energy

Since in this study, all data including wind speed, air temperature, and air pressure needed for calculating the wind energy density for five years (from 2012 to 2016) were measured by IMO in the time interval of 3 h, \Delta t is 3 and n equals 365 × 8 × 5. The calculated values for the cities under study are given in Table 5. The results show that Manjil and Ardebil with average wind energy densities of 6004.9 and 3002.6 (kWh/m²) are the first and second best cities in terms of wind energy, respectively. It is evident that Manjil enjoys by far the highest amount of wind energy, followed by Ardebil and Zabol.

To estimate the amount of hydrogen that can be produced via the proposed system using wind energy as a power source, three different types of wind turbines are scrutinized, whose specifications are given in Table 6.

The C_f values, the amount of energy produced by the turbines, the annual CO₂ emission reduction, and hydrogen production are shown in Table 7.

Figure 2 compares the amount of hydrogen (t) produced per year by utilizing the turbines in the cities. It is obvious that as the rated power of a turbine increases, more hydrogen is produced.

One of the main advantages of hydrogen energy utilization such as fuel for vehicles is lack of environmental pollution. Thus, the gasoline consumption and CO₂ emission in the regions under study after using the electricity generated by the turbines at the input of the proposed system is investigated.

According to 2016 Census, every Iranian family contains 4 members and has a car on average. Moreover, based on Refs. [²⁸,⁴³], one kilogram of hydrogen suffices for supplying energy to drive a car for a week. According to Iranian Oil Organization, each personal car in this country consumes approximately 772 L of gasoline per year on average, which equals 14.8 L a week. As it is shown in Table 7, in the case of using one set of Gamesa G47 wind turbine in Manjil, 91.22 kg/d of hydrogen can be generated which is sufficient as fuel for about 91 cars per week (In this study, it is assumed that 1 kg of hydrogen can run a car for a week.). Since each car consumes 14.8 L of gasoline each week, after fueling cars with hydrogen instead of gasoline, 1347 L (91 × 14.8) of gasoline per week or 70222.15 (91 × 14.8 × 52.14) liters of gasoline per year will be preserved. After preventing this amount of gasoline from burning each year, 163.9 tons of CO₂ emission is expected to be reduced in Manjil, calculated by using the RETScreen software. In Table 8, the population, the number of cars, and the average gasoline consumption in the cities are given. Moreover, the amount of hydrogen produced by applying the Gamesa G47 turbine as the input of the proposed system, the gasoline saved per year, and the annual CO₂ emission reduced are computed and shown.

Hydrogen production using solar energy

The calculated values of parameters a and b for the cities were used in this study. Table 9 provides these values and the average annual solar radiation energy. Equation (22) is used to convert J into kWh. As presented in Table 9, Zahedan with the average annual radiation of 2247.074 (kWh/(m²∙a)) has the highest amount of solar energy available compared to the other areas under study.

(22)\mathrm{1J}=\mathrm{2}.\mathrm{78}\times 1{\mathrm{0}}^{-\mathrm{7}}\mathrm{kWh}.

To estimate the amount of electricity produced by solar energy, 3 types of PV systems with different efficiency and materials were evaluated, whose characteristics are listed in Table 10. Table 11 presents the amount of electricity (kWh/a) produced by installing PV systems considering 2 scenarios, minimal and largest losses.

Since it is assumed that the rectifier in the hydrogen production system has a high performance with an efficiency of 95%, it is also presumed that the PV systems have the best performance, that is, 85%, for calculation of hydrogen generation, which means they have the lowest amount of losses (15%), the amount of hydrogen produced (t/a) by installation of 1000 PV systems in the cities under study was calculated, considering the fact that significant amount of hydrogen is not produced by utilizing just one set of the PV system (Fig. 3). The results indicate that 7.28 t/a of hydrogen are generated via the installation and utilization of 1000 sets of X21-345 PV system models in Zahedan. To this end, this city has the highest capacity of hydrogen production using the system proposed in this work compared to other cities.

Since hydrogen will be used as fuel for cars instead of gasoline, the hydrogen production which finally leads to saving gasoline after utilizing the PV systems to supply electricity for the proposed system is investigated. The RETScreen software is used for calculating the reduction in CO₂ emission. Table 12 provides the information about hydrogen production, the amount of gasoline saved after using hydrogen as fuel, and the reduction in CO₂ emission by utilizing 1000 sets of X21-345 PV systems as the input of the proposed system in the scenario with the lowest losses.

According to Table 9, Zahedan in Sistan and Baluchestan province situated in the south-east of Iran receives the highest amount of solar energy on average, that is, about 2247 (kWh/(m²∙a)). After developing a site with 1000 sets of X21-345 PV systems and the hydrogen production system proposed in this study, approximately 20 kg of hydrogen is produced in this city each day, which supplies fuel for 20 cars per week.

Conclusions

In this work, a renewable-powered system was proposed to produce hydrogen through water electrolysis process in different cities of Iran. Due to the abundance of wind and solar energy in some regions of the country, the amount of these energies available was computed by using the WDF and AP equation, respectively. Moreover, three different types of wind turbines as well as PV systems were investigated to estimate the amount of electricity produced by them. The results indicate that of all cities under study, Manjil has the largest amount of wind energy density of about 6004 (kWh/(m²∙a)). As regards solar radiation energy, Zahedan receives approximately 2247 (kWh/m²) solar energy per year.

An investigation of the wind turbines demonstrates that the largest amount of electricity can be generated via the Gasema G47 turbine, which is about 1948 MWh/a for Manil. If one set of this turbine is used for supplying energy for the system proposed, almost 91 kg of hydrogen would be produced per day. This amount of hydrogen provides 91 cars with enough energy to run during a week, saving about 70222 L of gasoline as well as reducing 163.9 tons of CO₂ emission per year.

Additionally, three types of commercial PV systems were evaluated in two scenarios, the highest and lowest losses. It is specified that about 20 kg of hydrogen can be produced per day after utilizing 1000 sets of X21-345 PV systems in Zahedan, which provides energy for 20 cars per week. This means that 15414 L of gasoline will not be burnt per year and approximately 35.9 tons of CO₂ will not be emitted to the atmosphere per year.

The technical analysis indicates that there are significant potentials for hydrogen production via wind and solar energies in the cities under study, leading to a huge carbon emission reduction by utilizing the hydrogen generated instead of gasoline. It is also required to assess the economic aspects of the hydrogen production system using wind turbines and PV systems. As a result, it is suggested that further research should be conducted on hydrogen generation in Iran to evaluate the economic feasibility of a wind/solar to hydrogen energy conversion system.

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