1. Introduction
Hydrogen appears to be an energy carrier of the future. According to Hunt et al. [
1], oil and gas companies are beginning since the COVID crisis to invest heavily in sustainable hydrogen-based energy production technologies. A large part of the activities of these industries are in the transport, mobility and building sectors. Hydrogen production for the construction of a H
2 economy appears as a model of future development for these industries. As suggested by Salehi et al. [
2] and Scheller et al. [
3], companies whose activities or products are related to high-level greenhouse gas emissions will be affected by the need for significant restrictions on their CO
2 production. Several interesting works exist in the literature to assess the impact of carbon taxes on energy demand, CO
2 emissions or on the economy [
4,
5].
Green Hydrogen, produced by electrolysis from renewable energies, can also play a major role in reducing CO
2 emissions. According to Lagioia et al. [
6], hydrogen energy can contribute to the decarbonization of the energy system in Europe for the actual century, for example, reducing emissions by 55% in 2030 compared to 1990 [
7]. The notion of environmental cost is linked to environmental damage or degradation representing any action that deteriorates, damages or durably alters the quality or functioning of the environment, health and ecosystems, and/or the quantities of available natural resources. Thus, with an environmental cost that is too high for oil, coal and natural gas, and a climate change and global warming context, hydrogen produced by renewable energy sources can contribute to reduce the air pollution [
8,
9] and thus limit human health damages [
10]. Moreover, hydrogen can help the world to obtain a carbon-neutral future [
11].
The war situation in Ukraine since February 2022 complicates the energy supply of many countries with a significant increase in costs and fears of blackout for the winter of 2023 (especially in France). In this respect, we can see that some countries are highly dependent on electricity and gas imports. The future development of a mix of energy sources and vectors will contribute to a better response capacity to uncertain geopolitical contexts and will give countries greater sovereignty in terms of energy.
However, it is now established that the uses of hydrogen are currently limited by two main criteria: the lack of infrastructure and the high production costs [
12]. Additionally, with a world population expected to reach nearly 10 billion in 2050 [
13], energy consumption for transport and buildings will continue to grow up to the end of the century.
The high costs of deploying hydrogen technologies are due to both technical and economic parameters. Technically, the resource itself is rare in its pure state. Atomic hydrogen is everywhere—92% of the atoms in the universe are hydrogen atoms. However, H
2 is naturally very rare. It is necessary to produce it as an energy carrier. Even if it can be easily stored, hydrogen remains expensive to produce because of the energy cost of its production and its restitution, presenting a maximum efficiency of 30% (electrolysis-storage-fuel cell). In addition, platinum, an essential element used in fuel cells, remains a rare and therefore expensive raw material to move quickly to a generalization of this solution on a large scale. Economically, the cost of green hydrogen is above all that of electricity. With electrolysers installed at USD 1000/kW and a 50% load factor, electricity at USD 70/MWh represents 85% of the cost of hydrogen. Thus, the determining cost factor is the price of the electricity consumed since it makes up 60 to 80% of the complete costs of hydrogen production by electrolysis depending on the operating time [
14].
The main energetic interest for hydrogen is its high energy density of 121 MJ·kg
−1 in comparison with gasoline or diesel fuels, respectively 47 and 44 MJ·kg
−1 [
15]. Hydrogen can release about 4 to 5 times more energy in its combustion than biofuels currently used in France (only 25 MJ·kg
−1 [
16]). Another interest of this gas lies in its capacity to be compressed for storage over long periods. Thus, for clean mobility, the main challenge is to manufacture tanks that can maintain high-pressure hydrogen (350 to 700 bars) without the hydrogen escaping.
Today, hydrogen is used in numerous applications for electrical and thermal energy production. Several papers reviewed the different hydrogen applications for massive or local energy production. Yue et al. [
17] presented hydrogen applications in energy storage, power-to-gas systems, and fuel cell co- and tri-generation or mobility applications. Hydrogen makes it possible to increase medium- and long-term storage capacities and can also be used to shift the renewable resources across the seasons due to the seasonal difference in energy production. Moreover, hydrogen can be introduced in an existing natural gas network using a photovoltaic or wind power plant [
18]. Using a Matlab software called ORIENTE (Optimization of Renewable Intermittent Energies with HydrogeN for auTonomous Electrification), the MYRTE (Mission hYdrogène Renouvelable pour l’inTégration au réseau Electrique) platform in France (Corsica island) has demonstrated the use of hydrogen to smooth the photovoltaic intermittent production [
19,
20] or to supply the grid during power peaks in the electricity consumption [
21]. Today, hydrogen (liquid or gas) is considered for numerous applications [
22], as a fuel for the future mobility [
23], under water situations [
24] or for power-to-gas strategies [
25].
Taking into account that 770 million of people do not have access to electricity in 2019 vs. 860 million in 2018 [
26], it is therefore logical to ask the question of how hydrogen could provide energy solutions to people considered in remote sites (single or grouped houses).
There are few articles in the literature on Europe-wide mapping of green hydrogen potential via photovoltaic electrolysis as an energy carrier for heat and power generation. A very recent review explores the production of green hydrogen at the scale of several regions of the world to show that this energy carrier can contribute to a transition towards a more environmentally friendly future energy but also improve energy independence in some countries [
27]. Moreover, a few localized studies exist at the country level. Mouli-Castillo et al. [
28] presented a recent paper on geological storage of hydrogen to meet regional heat production needs in the UK. In Niger (Africa), Bhandari [
29] is working on the potential of green hydrogen obtained from solar energy and concludes that it would be easy to produce this energy carrier for the needs of the transportation and electricity sectors. Other studies concern Vietnam and Ecuador [
30,
31]. They all point to a growing interest in this energy vector in the needs of a country. However, these studies do not present perspectives of this potential by the end of the current century under the influence of global warming.
More researchconcerns hydrogen use on remote sites, i.e., not connected to an electrical network due to the distance from the power grid or the non-possible installation of renewable energy systems on protected ecological areas. In Africa, based on a multi-criteria analysis, a hybrid off-grid Wind/PV (photovoltaic)/FC (Fuel Cells)/electrochemical batteries system is preferred to produce energy in a small household in Nigeria [
32]. Hydrogen coupled with wind turbine has demonstrated its interest to ensure uninterrupted power supply to an isolated zero-energy-house located at Catalca/Turkey [
33]. Projects such as PEPITE in France (Projet d’Etudes et d’expérimentation de Puissance pour la gestion des énergies Intermittentes par les Technologies électrochimiques [
34]) with H
2 under gas-state or for mobile network operators in Sub-Saharan Africa with H
2 under solid-state [
35], supply off-grid telecom towers for mobile or TV telecommunications. Using temporal simulations, several papers have investigated the hybridization PV/Electrolyser with or without fuel cells. As an example, for the electricity and thermal supplies of a passive house, Motalleb et al. [
36] simulated the behavior of the hybrid system for a yearly total heating load of 4395.7 kWh·yr
−1 and a daily maximum electrical DC peak of 300 W in the evening (21 h). Pal and Mukherjee [
37] proposed an investigation based on the techno-economic feasibility assessment to choose the best configuration corresponding to off-grid PV/hydrogen fuel cell system applications in northeast India. Using HOMER-based optimization software, Mohammed et al. [
38] determined the optimal design of a PV/FC hybrid system for the city of Brest in France. Typically, with a PV plant and FC of respectively 4200 kW and 2000 kW, corresponding to an electrolyser power of 3400 kW with 955 tons of hydrogen tank, a competitive COE (Cost Of Energy) is estimated at USD 0.120/ kWh
−1.
Taking into account this state of the art, our paper proposes a first mapping of H2(g) gas potential produced by a PV (100 kWp)/Electrolyser/H2-H2O storage tanks for Europe’s scale (12.5 12.5 km2 grid) using climate change data by the end of the century. The equivalent H2 energy will be considered for supplying electricity or heat energy for one or a few houses isolated from the grid or integrated into a smart grid.
Working from the latitude/longitude coordinates, the surface solar radiation downwards and the ambient temperature at 2 m extracted from the Coordinated Regional Climate Downscaling Experiment (CORDEX) database, this paper aims to simulate the behavior of the hybrid system leading to map the yearly electrolyzed H2(g) mass (kg·yr−1) and its equivalent energy (MWh·yr−1) on the domain. Thus, mappings of hydrogen capabilities in the past and actual conditions at two spatial scales (Europe and France) are proposed. Using two extreme RCPs (Representative Concentration Pathways) scenarios (2.6, favorable and 8.5, unfavorable), climate change impact on solar irradiation and ambient temperature are investigated to determine the evolution of gaseous H2(g) production and equivalent energy until the end of the 21st century.
The paper is organized as follows. After having reported on measurements and methods in
Section 2, mainly concerning physical models used to characterize the behavior of each energy subsystem,
Section 3 is devoted to the main results with (i) hydrogen and equivalent energy potential for a reference year 2005 and their evolution up to 2020, (ii) the determination of simple regressions to estimate yearly H
2(g) and energy potential in relation to latitude, (iii) the future tendencies of H
2(g) mass and equivalent energy for future decades up to 2100.
4. Conclusions
Hydrogen appears to be an energy carrier of the future to limit greenhouse gas emissions and thus contain the impact of climate change. With its ecological and economic advantages, green hydrogen produced by water electrolysis using renewable energy sources will contribute to the deployment of gaseous hydrogen throughout Europe.
The current conflict in Ukraine creates a complex energy situation in Europe. It sheds light on the lack of energy sovereignty of certain countries and demonstrates the fragility of several European electricity production systems. However, this geopolitical context did not influence the research conducted in our article because of the easy access to online European climate databases such as ECMWF.
By using historical meteorological data from the ECMWF Copernicus/Cordex database (reference year 2005), we have obtained a reference mapping of the H2 gas potential at the European scale by considering its production from a 100 kWp PV array hybridized with a PEM electrolyser/storage tank (35 bars). Yearly H2(g) production profiles have been established for 10 European cities thought Europe using two spatial scales (Europe and France). In these conditions, simulations have exhibited that the yearly electrolyser operating time can reach 74% (mean/min values: 68.1%/63.9%) when calculated in relation to the site’s sunlight hours. Brought back to the real time of the simulation, the ratios collapse to reach at best 15.5% (mean/min values: 14.2%/13.3%).
Under European latitudes between 31° N and 56° N, linear regressions were established to easily estimate the actual yearly H2 gas mass production (kg·yr−1) and its equivalent energy (MWh·yr−1) relative to latitude coordinates (°) with the objective of valorization into electricity or domestic heat for remote areas or renewable energy smartgrids.
The 2005 reference mapping was used to experiment with the impacts of climate change on the H2(g) mass production and equivalent energy over the period 2005–2100 according to two extreme scenarios, RCPs 2.6 and 8.5. For the least likely scenario (2.6), 2/3 of Europe’s surface will see its hydrogen production capacity increase up to 24.7% (mean/min values: 1.8%/−13.2%). However, for the most probable scenario (8.5), almost 3/4 of the European surface will experience a decrease in H2(g) production averaging −2.7% +/− 26% and up to −28.5% at the end of the century. The western countries in Europe will be the most strongly impacted (Norway, northern UK, western France, Spain, Portugal, western Mediterranean and the whole of northern Africa). The regions located in East Europe such as Germany, Romania, Bulgaria, Croatia, Greece will know an increase in H2(g) capacities than can reach 27.4% (RCP8.5). Considering that the observed mean values will be lower than the DSD, we can conclude that this would represent 95% of the statistically possible results. Thus, in the majority of cases, small changes will be expected in the coming decades. This also indicates a form of inertia of the climate system where it is known that the current trend will continue until the middle of the century (up to 2050/2060) and will experience changes in the distant future.
For decentralized applications (smartgrids, remote houses), power-to-gas technologies based on hydrogen (or synthetic methane) remain competitive in certain aspects compared to electrochemical batteries. Indeed, hydrogen offers storage capacities over several months up to 10 GWh, with a low electrical efficiency (30%) but a competitive global efficiency (heat/electricity, 80%). Electrochemical batteries offer daily or even weekly storage capacities of up to several tens of MWh. For identical storage capacities, hydrogen offers response times of about 100 ms compared to 1 min with compressed air. Thus, through innovative projects, the decentralized approach to energy production will aim to test the hydrogen injection at progressive rates (less than 20% in volume to start with) into a distribution network to supply a new district, or to develop clean mobility. This is the challenge to develop this technology for the future.