Microgrid Model for Evaluating the Operational Dynamics of Solar-Powered Hydrogen Production

1. Introduction

Energy is a fundamental aspect of human life and the progress of civilization. Consequently, in discussions and gatherings worldwide focusing on sustainable energy development, energy takes center stage. These discussions often encompass various green energy sources, such as solar electricity, wind power, wave power, and tidal power[1]. Over the coming decades, there is a projected increase in the demand for hydrogen fuel[2], which has garnered attention both as a potential energy source and as a means of energy storage[3].

Hydrogen fuel offers several advantages over traditional fossil fuels, serving as a cleaner alternative while mitigating the depletion of finite fossil fuel resources. Fossil fuels, due to their combustion byproducts like carbon dioxide, nitrogen, sulfur, and others contributing significantly to global warming, have detrimental effects on the environment [4]. Hydrogen fuel, on the other hand, presents a low-carbon alternative derived from renewable resources. Despite most hydrogen currently being sourced from fossil fuels; recent studies indicate a growing potential for hydrogen production through water electrolysis using renewable energy sources. This positions hydrogen fuel as a long-term alternative to hydrocarbon fuels, offering benefits and versatility [5]. Notably, hydrogen's combustion byproduct is water, making it one of the most efficient and cleanest energy forms [6].

Numerous studies have explored the challenges associated with transitioning to a hydrogen-based economy [7]. They have examined the essential steps required for the implementation of a hydrogen economy and outlined perspectives on hydrogen energy to address climate change concerns. These studies have also scrutinized the rationale behind hydrogen energy systems and technologies, comparing them to existing energy systems and their environmental impact [8]. Hydrogen, being the cleanest form of energy, holds the potential for diverse applications, including power generation and transportation. The future energy landscape is expected to be dominated by hydrogen fuel, offering advantages like minimal environmental impact, long-term storage capabilities, and enhanced mobility options [9].

This comprehensive study has a multifaceted approach. It first investigates the pivotal role of solar energy technology in the generation of hydrogen, specifically for the purpose of sustainable energy systems. Simultaneously, it embarks on the exploration and development of environmentally friendly techniques designed to enhance hydrogen production. The primary objective of this research is to actively promote the advancement of affordable and low-carbon technologies, with a specific focus on the production of green hydrogen. To provide practical insights into sustainable hydrogen production, this study endeavors to showcase a self-contained microgrid model. Within this model, the operational dynamics integral to the production of green hydrogen are thoroughly evaluated. Additionally, the study aims to assess the unique characteristics of hydrogen generation, particularly in terms of its utilization of solar energy and energy storage systems.

Recognizing the complexity of green hydrogen production, the study aspires to implement a comprehensive multi-domain framework. This framework encompasses various aspects, including electrical, thermal liquid, and thermal gas components, facilitating an in-depth exploration of the intricate processes underlying the green hydrogen production system. To further enhance the practical applicability of the research, the study endeavors to simulate and optimize the feasibility and efficiency of renewable energy sources. This optimization specifically addresses off-grid hydrogen production scenarios, contributing valuable insights to the field of sustainable energy solutions. Ultimately, the overarching goal of this study is to make significant contributions to the advancement of sustainable energy solutions. Through rigorous research and a focus on green hydrogen, the study aims to support and drive the transition towards cleaner and more environmentally responsible energy systems.

Figure 1 illustrates how various energy carriers, including coal, oil, natural gas, and hydrogen, differ in their Greening Factors (GF), Environmental Impact Factors (EIF), and Hydrogen Content Factors (HCF) [10]. The focus on the hydrogen economy underscores its significance in hydrogen production to harness the benefits of hydrogen fuel. Therefore, cost-effective hydrogen production must rely on renewable energy sources [11]. A methodology for assessing the environmental impact of hydrogen production processes has been implemented [12]. Hydrogen fuel has been identified as the cleanest and most renewable energy source for the future. A comparative study was conducted to reduce overall environmental emissions from shipping by utilizing hydrogen as a fuel [13].

To emphasize the unique value of hydrogen as a distinct choice, the following formulas are utilized to make comparisons between hydrogen and conventional fuels in terms of Environmental Impact Factor (EIF), Greenization Factor (GF), and Hydrogen Content Factor (HCF).):

$$EIF=\frac{kgC{O}_2\mathrm{p}\mathrm{r}\mathrm{o}\mathrm{d}\mathrm{u}\mathrm{c}\mathrm{t} \mathrm{o}\mathrm{f} \mathrm{c}\mathrm{o}\mathrm{m}\mathrm{b}\mathrm{u}\mathrm{s}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n} \mathrm{r}\mathrm{e}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}{\mathrm{k}\mathrm{g} \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}}$$

(1)

$$GF=\frac{{EIF}_{max}-EIF}{{EIF}_{max}}$$

(2)

$$HCF=\frac{kg of{H}_2\mathrm{i}\mathrm{n} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}}{\mathrm{k}\mathrm{g} \mathrm{f}\mathrm{u}\mathrm{e}\mathrm{l}}$$

(3)

where ${EIF}_{max}$ is max is the highest value of EIF among the choices that were analyzed. Coal is chosen as the ${EIF}_{max}$ in this specific instance with a 3.6. When shown in Figure 1 the energy sources grow greener (increasing GF) and have less of an influence on the environment (EIF) as the hydrogen content (HCF) increases [14].

This is an obvious benefit of hydrogen in terms of lowering emissions related to carbon. The hydrogen economy must be produced from abundant or renewable sources at cheap costs to fully benefit from it. In the literature, there are several studies emphasizing how hydrogen can be one of the most efficient options, significantly contributing to greater sustainability and the environment. Natural gas steam reforming is the most widely utilized process of the potential hydrogen production techniques examined in the literature, and it produces significant GHG emissions [15].

Natural gas steam reforming provides over 50% of the world's hydrogen needs, followed by oil reforming at 30%, coal gasification at 18%, water electrolysis at 3.9%, and other sources at 0.1%. Hydrogen should be produced from clean and abundant sources using ecologically friendly processes to mitigate the negative impacts of fossil fuel use on the environment, human health, and the climate. The phrase "green hydrogen production" refers to this idea [16].

2. Green hydrogen

The production of hydrogen from renewable sources is a critical step towards achieving zero-carbon hydrogen, often referred to as "green hydrogen." Utilizing renewable enreduceurces not only reduces dependence on oil and gas, thereby easing geopolitical tensions in the short term, but also opens new possibilities for hydrogen production. This is particularly relevant given the increasing generation of electricity from renewable sources and the temporary affordability of excess capacity resulting from the variability of solar and wind energy. To address the challenge of long-term electricity storage, finding sustainable solutions is becoming increasingly important [17].

Yadav and Banerjee emphasize the necessity of leveraging renewable energy for hydrogen production to establish a sustainable hydrogen economy. Currently, two relatively established methods for renewable energy-based hydrogen production are water electrolysis and biogas steam reforming.

Renewable electricity sources, such as solar, hydro, and wind power, or biofuels like biogas, can be used to generate green hydrogen. Among these methods, electrolysis powered by hydro or wind sources stands out as one of the most promising hydrogen production processes, particularly in terms of a Life Cycle Assessment [18].

While water electrolysis offers a cost-effective means of producing hydrogen compared to synthetic natural gas production, it still requires a significant amount of energy. However, projections suggest that by 2030, the cost of production may become competitive with existing methods. There are three types of electrolysis cells: solid oxide electrolysis cells (SOEC), proton exchange membrane electrolysis cells (PEMEC), and alkaline electrolysis cells (AEC). SOEC is particularly effective for hydrogen production and co-electrolysis of carbon dioxide, thanks to its superior energy conversion efficiency.

Various reforming techniques, such as steam reforming (SR), dry reforming (DR), dry oxidation reforming (DOR), partial oxidation reforming (POR), and autothermal reforming (ATR), can be employed to produce low-carbon hydrogen from biogas. Technologies for hydrogen production from renewable sources that are still in the maturation phase include biomass gasification, pyrolysis, thermochemical water decomposition, and biomass supercritical water gasification. Solar-powered hydrogen production is an environmentally friendly approach, and thermochemical cycles offer another avenue for green hydrogen production. Thermochemical pyrolysis and gasification processes are the most likely candidates for large-scale applications soon, as they are commercially viable. While biological approaches hold promise, further research is needed to enhance their output [19].

3. Hydrogen's chemical and physical properties

Since the early 1800s, hydrogen has been used as a form of energy. In the 1970s, when it started to become significant as the driving force behind the Space Race, the potential for it to become the primary energy carrier in contemporary energy systems emerged [20].

The most abundant element on the planet, hydrogen, is extremely important. It is found mostly in demineralized form and only as part of a molecule in nature, primarily in hydrocarbons and water. Under normal temperatures and pressures, it exists as a gas (293.15 K and 1 atm). At ambient pressure, it has a very low boiling point of -252.76 °C (20.3 K). Hydrogen is also colorless, odorless, and non-toxic under normal conditions, making it environmentally friendly. Hydrogen changes states over a tight temperature and pressure range. Liquefaction is thus primarily accomplished through cooling rather than compression, creating opportunities for heat recovery schemes [21]. Liquefaction increases the density of hydrogen by an order of magnitude. Natural gas has a factor of 600, while LPG has a factor of 250. This makes hydrogen liquefaction an appealing mode of long-distance transportation. During transport, the temperature is extremely low (-253°C) [22].To keep hydrogen from evaporating, you must use a highly efficient insulation system [23].

Under moderate or high pressure, hydrogen can also be transported in gaseous form. A promising method of hydrogen storage referred to as adsorption on solids and liquids, is currently being researched. Even at atmospheric pressures, this intriguing storage method can hold significant amounts of H2 [24].

The lowest molecular weight of any substance is hydrogen (2.0016 g/mol). It is combustible over a very wide concentration range, which results in a wide variety of ignition conditions, as indicated by the lower and upper explosive limits [25]. Extremely lean air/gas combinations are made possible by this wide ignition range, which reduces fuel use and promotes more effective combustion [26].

Overall, as shown in Figure 2, hydrogen has a high mass-based or gravimetric energy density of 120 MJ/kg or 33 kWh/kg, which is nearly three times greater than the energy density of today's conventional fuels. The calorific value or lower heating value of a fuel determines its mass-based energy density [22].

4. Demand for hydrogen

Energy and hydrogen have a long history together; more than 200 years ago, hydrogen powered the first internal combustion engines and is now a crucial component of the modern refining sector [27]. It emits no greenhouse gases or pollutants directly and is light, storable, and energy dense. But the adoption of hydrogen in areas where it is virtually nonexistent, like transportation, buildings, and power generation, is necessary for it to significantly contribute to clean energy transitions [28].

In Figure 3 of Hydrogen is a thorough, unbiased examination of hydrogen that outlines the current situation, how hydrogen might contribute to the development of a clean, secure, and economical energy future, and how to go about realizing its potential [29].

The supply of hydrogen to industrial customers has grown significantly in recent years [30]. Since 1975, the demand for hydrogen has more than tripled and is still growing [31]. The manufacture of hydrogen uses 6% of the natural gas and 2% of the coal in the globe [32].

As a result, the creation of hydrogen generates about 830 million tons of CO2, which is comparable to the emissions of Indonesia and the United Kingdom put together [33].

5. Technology for Hydrogen Production

The following happens when water is divided into O2 and H2 gases by electricity produced by renewable energy sources (RSE) in Figure 4 such as biomass, geothermal, wind, and solar energy [34].

$$H_{2}O+2F\to H_2+1/{2O}_2$$

(4)

F is the constant of Faraday, which is equal to 96485 °C for 1 mol of electricity [35]. The opposites of reaction (1) can be used to create electricity from hydrogen using HFC or combustion processes [36].

$$H_2+1/{2O}_2\to H_{2}O+2F$$

(5)

Because the cost of water in reaction (1) is negligible, the price of hydrogen production from the electrolysis process is heavily influenced by the cost of electricity. from the electrolysis of water [37]. At 80°C, commercial electrolytes use 30% KOH (alkaline electrolysis) that can be recovered and reused [38]. When using an alkaline electrolysis system (AES), the efficiency is approximately 55-75%. The electrodes are nickel, and the cathode and anode are platinum or manganese oxide coated. Pure hydrogen is typically produced [39]. Commercial AES with a power consumption of 4.49 kWh/m3.

Although the electrolysis of water has shown promise in the production of hydrogen, this technology still faces challenges [40]. The electrodes used in today's water electrolysis technology are generally coated with expensive platinum, making the process uneconomical [42]. As a result, the use of nanomaterials to remove such noble metals in the water electrolysis process has attracted attention [41], and a cobalt phosphate catalyst has been proposed as a promising method to split water molecules into their pressurized atmosphere by doubling photosynthesis. A conventional indium tin oxide anode is used in this system for water splitting needed. The use of abundant cobalt phosphate, which is much cheaper than expensive platinum, makes electrolysis technology less expensive.

6. Green H₂ Production from Renewable Sources

Currently, hydrocarbons are the primary source of H2 production, but the integration of renewable options is becoming crucial as fossil fuels deplete and concern grows about the greenhouse effect [42]. Over time, renewable technology is predicted to surpass traditional methods, particularly as the demand for more sustainable solutions grows [43]. There are numerous methods for obtaining hydrogen from renewable resources, and this section gives a quick rundown of some of the ways and technologies used for biomass-based water splitting [44].

7. Simulation and results

This microgrid requires 460 kWh/day and has a peak of 63 kW. In the proposed system, the following generation sources serve the electrical load as in Figure 9.

The system architecture includes a 20.0 kW fuel cell generator, 120 kW PV, 50.0 kW electrolyzer, and a hydrogen tank with a capacity of 120 kg, all managed by the HOMER Load Following dispatch strategy as shown in Table 3.

i 

Cost Summary

The Cost Summary for various components related to a system. Each component has different cost elements such as Capital, Operating, Replacement, Salvage, and Resource costs. Here's a breakdown of the information in the Figure 10.

The Net Present Costs for various components related to a system. Each component has different cost elements such as Capital, Operating, Replacement, Salvage, and Resource costs. Here's a breakdown of the information in the Table 4.

The Annualized Costs for various components related to a system. Each component has different Annualized Costs such as Capital, Operating, Replacement, Salvage, and Resource costs. Here's a breakdown of the information in the Table 5

The Cash Flow for various components related to a system. Each component has different Cash Flow such as Capital, Operating, Replacement, Salvage, and Resource costs. Here's a breakdown of the information in the Figure 11

ii 

Electrical Summary

Table 6 summarizing information related to excess and unmet quantities of the system.

Table 7 provided a production summary table for different components, specifying the production quantities in kilowatt-hours per year (kWh/Year) and the corresponding percentage contribution.

Table 8 provided a consumption summary table for different components, specifying the consumption quantities in kilowatt-hours per year (kWh/Year) and the corresponding percentage contribution.

Table 9 provides a comprehensive summary of various metrics related to the electrical performance of a Fuel Cell

Figure 12 provide the fuel cell output.

Table 10 provides a summary of various metrics related to the electrical performance of a Photovoltaic (PV) system.

Figure 14 shows the photovoltaic output in kW.

Table 11 presents a summary of various metrics related to the performance of an electrolyzer.

Figure 14 represent of Electrolyzer Input Power

Figure 14. Electrolyzer Input Power (kW).

Figure 14. Electrolyzer Input Power (kW).

Table 12 provides information on the properties and statistics of a hydrogen tank, including its storage capacities, autonomy, and hydrogen content at the beginning and end of the year.

Figure 15 shows the level of hydrogen fuel tank over year.

Table 13 provides statistics on the consumption of stored hydrogen, including the total amount consumed, average daily consumption, and average hourly consumption.

Figure 16 provide the state of Stored hydrogen Consumption.

Table 14 provides information on the emissions of various pollutants, including carbon dioxide, carbon monoxide, unburned hydrocarbons, particulate matter, sulfur dioxide, and nitrogen oxides.

Renewable Summary

Table 15 provides various metrics related to renewable energy, including capacity-based metrics, energy-based metrics, and peak values.

Figure 17 provide the Instantaneous Renewable Output Percentage of Total Generation

Figure 18 shows the 100% Minus Instantaneous Nonrenewable Output as Percentage of Total Load in one year.

Figure 19 represent the time series of electrolyzer output.

8. Conclusion

This study underscores the critical role of solar energy technology in the sustainable production of hydrogen. Traditional methods relying on fossil fuels for hydrogen production are environmentally detrimental, making it imperative to explore greener alternatives. Green hydrogen, while initially more expensive, holds the promise of affordable and low-carbon technologies, driving innovation in the field. The development of a self-contained microgrid model, integrating solar energy and energy storage, provides a versatile platform for evaluating the intricacies of green hydrogen production. This multi-domain framework allows for a holistic exploration of the processes involved, paving the way for optimized off-grid hydrogen production using renewable sources. The microgrid system presents a robust solution to the energy requirements, requiring 460 kWh/day with a peak demand of 63 kW. The system integrates a 20.0 kW fuel cell generator, 120 kW PV system, 50.0 kW electrolyzer, and a 120 kg hydrogen tank, all managed by the HOMER Load

The analysis of solar hydrogen production methods, with an emphasis on electrochemical production using photovoltaic technology, reveals its high efficiency and potential. However, cost limitations may restrict its broader adoption, necessitating further advancements in technology to enhance affordability and reliability. With the global push for carbon reduction and the urgency to combat climate change, hydrogen emerges as a clean and dependable energy carrier capable of replacing fossil fuels. However, the environmental friendliness of hydrogen production greatly depends on the primary energy source employed, highlighting the significance of transitioning to low-carbon hydrogen production methods.

As we look ahead, the maturity of low-carbon hydrogen production technologies becomes paramount. Investing in research and development, expanding production infrastructure, and providing long-term policies to reduce uncertainties are crucial steps in realizing the potential of low-carbon hydrogen as a key player in decarbonizing our future energy systems. The transition to sustainable hydrogen production is not only desirable but also necessary to achieve a cleaner and more sustainable energy future.