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Review

Hydrogen Materials and Technologies in the Aspect of Utilization in the Polish Energy Sector

by
Krystyna Giza
1,
Edyta Owczarek
1,*,
Joanna Piotrowska-Woroniak
2 and
Grzegorz Woroniak
2
1
Faculty of Production Engineering and Materials Technology, Czestochowa University of Technology, Armii Krajowej 19, 42-200 Czestochowa, Poland
2
HVAC Department, Bialystok University of Technology, Wiejska 45E, 15-351 Bialystok, Poland
*
Author to whom correspondence should be addressed.
Appl. Sci. 2024, 14(21), 10024; https://doi.org/10.3390/app142110024
Submission received: 27 September 2024 / Revised: 25 October 2024 / Accepted: 31 October 2024 / Published: 2 November 2024
(This article belongs to the Special Issue Production, Storage and Utilization of Hydrogen Energy)
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Abstract

:
Currently, modern hydrogen technologies, due to their low or zero emissions, constitute one of the key elements of energy transformation and sustainable development. The growing interest in hydrogen is driven by the European climate policy aimed at limiting the use of fossil fuels for energy purposes. Although not all opinions regarding the technical and economic potential of hydrogen energy are positive, many prepared forecasts and analyses show its prospective importance in several areas of the economy. The aim of this article is to provide a comprehensive review of modern materials, current hydrogen technologies and strategies, and show the opportunities, problems, and challenges Poland faces in the context of necessary energy transformation. The work describes the latest trends in the production, transportation, storage, and use of hydrogen. The environmental, social, and economic aspects of the use of green hydrogen were discussed in addition to the challenges and expectations for the future in the field of hydrogen technologies. The main goals of the development of the hydrogen economy in Poland and the directions of actions necessary to achieve them were also presented. It was found that the existence of the EU CO2 emissions allowance trading system has a significant impact on the costs of hydrogen production. Furthermore, the production of green hydrogen will become economically justified as the costs of energy obtained from renewable sources decrease and the costs of electrolysers decline. However, the realisation of this vision depends on the progress of scientific research and technical innovations that will reduce the costs of hydrogen production. Government support mechanisms for the development of hydrogen infrastructure and technologies will also be of key importance.

1. Introduction

Hydrogen is the most abundant element in the universe (it makes up about 74% of the matter of the universe). It is only ninth on Earth in terms of its prevalence (0.9% of the mass of the Earth’s crust and hydrosphere) and occurs mainly in the form of water and numerous organic substances (natural gas, crude oil, biomass). Hydrogen fuel is considered emission-free because during its combustion with pure oxygen, as well as during electrochemical oxidation in fuel cells, the only by-product is water or water vapour. Since the use of the above-mentioned energy carrier is technically complicated and expensive, for a long time, virtually the only area where hydrogen fuel was used was rocket propulsion.
The current need to reduce greenhouse gas emissions makes it necessary to develop fuels other than hydrocarbons to minimise the effects of global warming. Widespread awareness of the described problem, both among politicians and societies, favours the announcement of further programmes for the development of emission-free energy sources. In July 2020, the European Commission published a document entitled “A hydrogen strategy for a climate neutral Europe” [1]. It indicates that “hydrogen is a key element in achieving the European Green Deal and a clean energy transformation in Europe”, and also indicates the directions in which the use of hydrogen in the economy and industry should be developed. The priority in the strategy adopted by the European Commission is the production of emission-free hydrogen based on energy from renewable sources. Ambitious plans for the development of the hydrogen economy were also adopted by Poland in the “Polish Hydrogen Strategy until 2030 with a perspective until 2040” (PHS), published in December 2021, developed by the Ministry of Climate and Environment [2]. It formulates six goals relating to the priority areas of hydrogen use, which are industry, transport, and energy, as well as its production and distribution.
To date, Poland is a leading hydrogen producer (approximately 1.3 million tons of H2 per year) in the EU [3]. Hydrogen produced conventionally (mainly from natural gas), which is accompanied by greenhouse gas emissions, is used by industries. Therefore, in the light of PHS and other applicable regulations, it is crucial to implement new hydrogen technologies producing clean hydrogen that could be utilised in other sectors of the economy. Taking into account the current political situation and the need to diversify energy supply sources, as well as reduce dependence on the import of fossil fuels, the development of the hydrogen economy in Poland is of particular importance.
This work discusses the physicochemical properties of hydrogen fuel compared to other energy carriers, its production technologies, including costs in addition to its environmental impact, and storage methods. The following part of the work presents the current state of the hydrogen economy in Poland in addition to examples of practical implementations of Polish hydrogen technologies important for its development. The motivation for writing this comprehensive review was to provide researchers and decision-makers with up-to-date knowledge about the possibilities and limitations regarding the transition to hydrogen energy with the example of Poland and to indicate a direction for further actions. The strengths and weaknesses of obtaining, storing, transporting, and using hydrogen were analysed. The goals of Poland’s current energy policy in the context of implementing hydrogen energy were also presented.

2. Physicochemical Properties of Hydrogen

Of all the elements, hydrogen is the lightest in any state of matter. The density of gaseous hydrogen (273 K, 1.0 atm) is 0.09 g/dm3, liquid hydrogen 71 g/dm3, and crystalline hydrogen 88 g/dm3. Under standard conditions, it occurs in the form of diatomic H2 molecules; it is a colourless and odourless gas with a boiling point of 20 K and a freezing point of 14 K. Due to its properties, it is difficult to detect with the human senses, and its small size contributes to high diffusivity in addition to its tendency to penetrate many solid materials.
Hydrogen is a flammable gas and should be stored away from heat sources or open flames. The reaction of hydrogen with oxygen is highly exothermic (Equation (1)). However, it should be remembered that it takes place very slowly at room temperature. This reaction occurs at a noticeable rate only at the temperature of 180 °C, and at 450 °C, it is explosive. The process is particularly vigorous when the volume ratio of hydrogen to oxygen in the mixture is 2:1 (the so-called fulminant mixture).
2H2 (g) + O2 (g) → 2H2O (g)    ΔH = −483.6 kJ
As can be seen from Figure 1, hydrogen is an extremely attractive fuel, owing to its high gravimetric energy density (143 MJ/kg) being approximately three times greater than the energy density of conventional fuels such as liquefied natural gas (LNG) (55.5 MJ/kg), compressed natural gas (CNG) (55.5 MJ/kg, petrol (46.4 MJ/kg), or diesel oil (45.6 MJ/kg) [4,5,6,7]. On the other hand, the value of hydrogen combustion heat related to a unit of volume is small. Hydrogen gas compressed to a pressure of 700 atm at room temperature has an energy density of 5.6 MJ/L, which is approximately six times less than gasoline or diesel oil. During the process of liquefaction, its volume decreases, raising the energy density of liquid hydrogen to 10 MJ/L. Nonetheless, compressing hydrogen is a costly process, and converting it into a liquid form requires the temperature of hydrogen to be reduced below 33 K (the critical temperature of hydrogen). It has been estimated that the hydrogen liquefaction process requires the equivalent of approximately 36% of the energy stored in it [8]. The very low volumetric energy density of gaseous hydrogen makes its transport and storage inefficient and therefore significantly more expensive than currently used liquid fuels. Hence, the vigorous development of efficient storage and transport technologies is crucial in order to promote sustainable development. It is expected that multiphase composites can extend the temperature/pressure range of hydrogen storage materials.
Attention should also be paid to other parameters describing the physicochemical properties of hydrogen for use as fuel.
As can be seen from Table 1, the only negative feature of hydrogen fuel is its wide range of flammability in comparison to methane, diesel, or petrol fuel. If the volume concentration of hydrogen is from 4 to 75% at a temperature of 293 K, the probability of the spontaneous combustion of such a mixture is very high. The upper flammability limit of hydrogen-enriched methane mixtures increases with the hydrogen content in the fuel. The share of hydrogen does not significantly affect the value of the lower flammability limit of methane. Replacing a certain amount of natural gas with hydrogen is also a method of reducing CO2 emissions. In this way, it is possible to effectively use the excess electricity generated by renewable energy sources and reduce the consumption of natural gas. Although mixing hydrogen with natural gas offers potential benefits, levels above 15% (v/v) of hydrogen pose many challenges in terms of the pipeline materials, safety, and modification of the final receiving equipment [9]. Computational models can provide support in research without worrying about safety issues that may arise during the experiment [10].
Both the self-ignition temperature of hydrogen and the octane number are relatively high compared to other fuels. Therefore, the hydrogen–air mixture is resistant to self-ignition and detonation combustion and is additionally suitable for use in spark-ignition combustion engines. Initiating hydrogen combustion requires little energy. The ignition energy of hydrogen is an order of magnitude less than that of natural gas, amounting to 0.02 mJ [11]. The dynamics of the hydrogen combustion process are also much higher compared to that of other fuels, as illustrated in Table 1. Hydrogen is neither more nor less dangerous than other currently used flammable fuels, such as petrol or natural gas. The safety issues associated with hydrogen combustion are due to its wider flammability range and higher flame speed. As can be seen from Table 1, hydrogen ignition is possible at a concentration of 4% in a mixture with air; thus, the lower flammability limit of hydrogen should be the limiting concentration when developing guidelines for safe work with hydrogen.
In public opinion, hydrogen is still perceived as one of the most dangerous energy carriers. Since hydrogen gas is the lightest of all gases, 14 times lighter than air, this means that when released from an installation in an open environment, it will quickly rise and dissipate. Using hydrogen is especially dangerous in closed spaces, such as underground parking lots or tunnels. As with any other fuel, hydrogen also faces threats in situations of improper transport or storage. Nevertheless, these risks can be minimised by implementing appropriate control systems [14,15,16,17].

3. Hydrogen Production Methods

On our planet, hydrogen occurs mainly in the bound state. The sources of hydrogen are water, hydrocarbons, and biomass. In the free state, hydrogen occurs in small amounts in volcanic gases and natural gas. Therefore, it cannot be extracted like conventional fuels are but must be produced by using energy.
From the climate policy and environmental protection point of view, the method of hydrogen production and the associated CO2 emissions are important. Table 2 compares the hydrogen production methods with respect to their efficiency, costs, environmental impact, advantages, and disadvantages. Therefore, as can be seen from Table 2, hydrogen is designated with the colours, black, grey, blue, pink, and green, among others.
For over half a century, hydrogen has been produced and used for industrial purposes. At present, 48% of produced hydrogen is made in the methane reforming process using steam, 30% is produced from crude oil, mainly in refineries, 18% is made from coal, and the remaining 4% is produced by means of water electrolysis [11].
Reforming methane with steam is currently the most common industrial method of obtaining so-called grey hydrogen. Hydrogen produced by the steam reforming of methane is obtained with an energy efficiency of 74–85% (Table 2). During this process, the following reactions mainly occur:
CH4 + H2O → CO + 3H2     ∆H⁰298 = 206 kJ/mol
CO + H2O → CO2 + H2     ∆H⁰298 = −41 kJ/mol
The higher hydrocarbons found in natural gas also react with water vapour and are an additional source of hydrogen and carbon monoxide.
CnHm + nH2O → nCO + (n + m/2)H2
This process is carried out on nickel catalysts at temperatures above 500 °C. The initial purity of hydrogen obtained in this process is 95–98%.
The methane reforming process is more beneficial than its simple combustion, owing to the ability to control CO2 emissions and sequester them. Hydrogen produced from fossil fuels combined with CO2 capture processes is designated with the colour blue.
Analogous to the reforming process, by means of the Bosch reaction (Equation (5)), synthetic gas can be produced by reacting coke with steam. Additional hydrogen can be obtained in further processing by reacting the resulting syngas with water vapour (Equation (3)), or it can be utilised as a reagent in organic synthesis or an energetic material.
C + H2O → H2 + CO     ∆H⁰298 = 131.0 kJ/mol
It is worth noting that the total production efficiency of so-called black hydrogen is twice as low as in the methane steam reforming process, because coke, unlike hydrocarbons, does not contain hydrogen. The energetic efficiency of the coal-to-hydrogen conversion system is about 30–40% (Table 2).
Power-to-gas (PtG) technology envisages the making of hydrogen on an industrial scale through water electrolysis using electricity. Water electrolysis is a process with unfavourable thermodynamics that requires external energy. The four most commonly used methods of water electrolysis for hydrogen production are proton exchange membrane water electrolysis (PEM), solid oxide water electrolysis (SOE), alkaline anion exchange membrane water electrolysis (AEM), and alkaline water electrolysis (AEL) [19,20,21,22,23,24,25,26]. It involves reducing protons at the cathode (negative electrode) to hydrogen gas and simultaneously oxidising water at the anode (positive electrode) to oxygen gas.
Cathode: 4H+ + 4e → 2H2     E° = 0 V
Anode: 2H2O → O2 + 4H+ + 4e      E° = +1.23 V
The efficiency of water electrolysis is approximately 70–80% [22,23], and the goal is to achieve an efficiency of up to 82–86% by 2030 using proton exchange membrane (PEM) electrolysers [24]. These electrolysers are characterised by high efficiency but also a high equipment cost. Therefore, they should be used for small-scale green hydrogen production. Hydrogen produced by means of water electrolysis is much more costly (3.6–12.1 USD/kg H2, which is dependent on the price of, among others, electricity and electrolysers) [25] than hydrogen made by the classic methane reforming method (1.2–2.7 USD/kg H2) because of the high energy input needed for the water electrolysis process [25]. However, hydrogen obtained in the synthesis process by processing gas or coke cannot be considered a clean energy carrier. In order to ensure the production process of hydrogen is climate neutral, it is essential to use water as a source of hydrogen in addition to electricity from renewable energy sources (RES)—we assign such hydrogen the colour green.
To avoid transmission losses, it is best to locate PtG electrolysers near renewable energy sources.
If we use nuclear energy as a source of electricity to produce hydrogen, then as a result of the electrolysis process, we will obtain hydrogen assigned a purple colour.
It is also possible to obtain hydrogen using the photocatalytic and photoelectrocatalytic decomposition of water. To this end, semiconductor materials and catalysts are used, capable of absorbing solar radiation, whose energy is utilised to reduce water [14,15,16,17,22]. Nevertheless, systems of this type are not yet used on an industrial scale.
The decision whether hydrogen is cleaner than other alternative energy sources should be assessed based on its entire life cycle and not just on selective stages, e.g., compared to zero emissions during electrochemical oxidation in a PEM fuel cell. It should be remembered that hydrogen fuel is not emission-free. As shown by the authors of [27], the hydrogen technologies with the lowest carbon footprint are the steam reforming of waste alcohol (586.7–768.1 kg CO2 equivalent/t H2) and water electrolysis using renewable energy sources (2329.8 kg CO2 equivalent/t H2). In addition, the use of green hydrogen in the most efficient fuel cells results in obtaining electrical power two times lower than the energy used for electrolysis [27]. Therefore, a reasonable solution would be to accumulate the generated energy, e.g., during periods of the highest solar activity or periods of a reduced demand for electricity.

4. Hydrogen Storage

The storage technologies for hydrogen presented schematically in Figure 2 can be categorised into the following three main types:
−
Physical methods that involve storing compressed or liquefied molecular hydrogen;
−
Methods on the basis of the adsorption processes of molecular hydrogen on materials having a well-developed surface using weak intermolecular van der Waals interactions;
−
Chemisorption methods, which involve the chemical binding (absorption) of atomic hydrogen.
Currently, hydrogen storage in the gaseous or liquid phase is used on a large scale [28,29,30]. Hydrogen storage tanks have appropriate process safeguards, including pressure relief devices (PRDs).
Commercially available fuel cell electric vehicles use high-pressure tanks that enable the storage of hydrogen at pressures of 350 and 700 atm. Nonetheless, these types of tanks are not cost-effective for stationary applications to store large volumes of hydrogen, which are typically stored at a pressure no greater than 100 bar in aboveground tanks and 200 bar in storage tanks located underground [31,32].
The investment costs are much higher in the case of terrestrial options and therefore the latter solution is preferred, especially in areas where salt caverns [33,34], depleted gas/oil deposits, or aquifers can be utilised [35].
Assuming that the use of hydrogen will significantly grow in the future, there will be a need for appropriate gas transport. The most economical means to transport large quantities of hydrogen over great distances is through pipeline networks [36,37,38,39]. There are not many technical obstacles to building hydrogen storage pipelines. On the other hand, hydrogen pipelines are more expensive to build than natural gas pipelines, mainly because of the properties of hydrogen.
The tendency of hydrogen to penetrate the walls of metallic materials increases their brittleness and deteriorates their mechanical properties. The modification of a natural gas pipeline to transport clean hydrogen necessitates solving issues related to the embrittlement of some steels due to the action of hydrogen and problems with sealing fittings, flanges, and threads to prevent uncontrolled hydrogen escape [40].
Hydrogen fuel is converted into a liquid state so as to increase its storage density. The volume ratio of hydrogen in the liquid state (LH2) to hydrogen in the gaseous state (GH2) is 1:848. Heating LH2 to ambient temperature in closed spaces leads to the creation of very high pressures. For safety reasons, it is important to provide buffer space in cryogenic tanks to accommodate the expansion of the gas volume increase as the temperature rises. A lack of buffer space may lead to overpressure in the tank.
To reduce the rate of evaporation of liquid hydrogen, the surface-to-volume ratio of the storage tanks is minimised by giving them a spherical shape and through insulation that minimises heat transfer through the walls of the tank. Storage tanks for liquid hydrogen most often have double walls, with high vacuum between them, which reduces heat transfer through convection and conduction to a minimum [41].
Additional materials, such as particles of aluminium, silica or perlite, or alternating layers of aluminium foil and fibreglass, are put in the space between the tank walls to protect against heat transfer via radiation [42].
It worth noting that evaporation is less of a problem in situations where the facilities for hydrogen liquefaction and the storage of its product are located near each other [43] and the hydrogen is utilised in hydrogen fuel cells or gas turbines to generate electricity when necessary.
Currently, the largest tanks for storing liquid hydrogen are operated by NASA. The amount of hydrogen stored in these tanks is 230–270 tons. There is evidence that tanks for storing liquid hydrogen, despite the complexity of their structure, are less expensive per mass of stored hydrogen in comparison to tanks for pressurised gaseous hydrogen. However, it is essential to bear in mind the high costs related to the energy demand for hydrogen liquefaction and the capital required to build a liquefaction plant, which constitute a significant portion of the total costs of liquefaction, even for larger plants [44].
Unlike storing hydrogen in a gaseous or liquid form, most tanks based on hydrogen adsorption have to date only been used on a laboratory scale. As a consequence of the weakness of the van der Waals bond between the adsorbent and molecular hydrogen, low temperatures (liquid nitrogen) and elevated pressures (10–100 atm) must be used to obtain a significant hydrogen storage density by adsorption. Many porous materials based on carbon [45] have been proposed for storing hydrogen, porous materials composed of metal ions connected with organic ligands, so-called organometallic structures [46], porous polymer materials [47], and zeolites [48]. Some activated carbons and organometallic structures adsorb hydrogen in an amount of 8–10% m/m at a temperature of −196 °C [49,50]. Nevertheless, owing to the fact that the employed adsorbents have a low density, the volumetric hydrogen storage density is low. Moreover, to ensure that the appropriate degree of adsorption is achieved, the generated heat must be effectively removed. In order to remove the heat of adsorption of 1 kg of hydrogen using an adsorbent that has a hydrogen adsorption enthalpy of 4 kJ/mol, at least 10 kg of liquid nitrogen must be evaporated [28].
In metal hydrides, hydrogen can be directly bonded to a metal atom (elemental metal hydrides and intermetallic hydrides) or may be part of a complex ion which is bonded to a metal atom (complex metal hydrides). Chemical hydrides, on the other hand, consist exclusively of non-metallic elements.
Most elemental metal hydrides are unsuitable for hydrogen storage, resulting from their ability to store small amounts of hydrogen, their high temperature, and slow kinetics of the hydrogen absorption/desorption reaction. The most promising and widely researched metal hydrides for large-scale hydrogen storage are, among others, MgH2 and AlH3 [51,52].
MgH2 is an appealing hydrogen storage material due to its high theoretical hydrogen storage capacity of 7.6% m/m in addition to the fact that magnesium is non-toxic, inexpensive, and widely available. On the other hand, magnesium and hydrogen form a strong bond and the kinetics of the hydrogenation/dehydrogenation reaction are slow. Because of these kinetic and thermodynamic limitations, in order to achieve a reasonable rate of MgH2 dehydrogenation, temperatures over 300 °C must be applied [53].
The hydrogen storage properties of AlH3 are different. The dehydrogenation enthalpy for aluminium hydride is about 11 times lower than for magnesium hydride and is only 7 kJ/mol. Hydrogen binds relatively weakly with aluminium, and the dehydrogenation reaction, in which theoretically 10.1% m/m hydrogen is released, proceeds quickly already at a temperature of 100 °C. However, this is an irreversible reaction, and extremely high pressures are required to rehydrogenate Al from the gas phase [54]. The methods of obtaining aluminium hydride based on electrochemical regeneration [55] have proven promising but have not to date been implemented on an industrial scale.
In practise, the number of intermetallic structures used to store hydrogen is relatively limited. Most often they are AB5, AB2, and AB alloys capable of absorbing a maximum of 2% by weight hydrogen.
Owing to the constantly developing techniques and the huge number of ideas for storing H2, the United States Department of Energy has prepared specific guidelines for hydrogen tanks that will be used in so-called light vehicles—mainly passenger cars—but also bicycles and scooters. These requirements include, among others, the tank charging time, its efficiency, cost, and mass capacity, which should ultimately be 65 g of H2/kg of the compound, i.e., 6.5% by mass [56]. According to these requirements, the gravimetric densities of hydrogen storage by intermetallic compounds are too low to be used in passenger cars, but they are used as stationary hydrogen storage facilities. Assuming that the intermetallic compound reversibly absorbs only 2 wt% hydrogen, a material weighing 300 kg can store 6 kg of hydrogen fuel, which should cover a distance of approximately 500 km. For comparison, the total weight of the Tesla Model 3 battery pack with a capacity of 75 kWh is as much as 480 kg [57].
A significant problem related to the use of intermetallic hydrides is their price [58]. Nonetheless, despite their high costs, intermetallic hydrides are successfully utilised for hydrogen storage, as anode materials in Ni-MH cells, and in hybrid energy systems [59].
Complex metal hydrides, unlike intermetallic hydrides, consist chiefly of light elements. Thanks to this, they have the ability to gravimetrically store large amounts of hydrogen. The main complex hydrides utilised for hydrogen storage include alanates, borohydrides, and nitrates, which are extensively covered in the literature [60,61].
Lithium borohydride (LiBH4), with its theoretical gravimetric hydrogen storage capacity of 18.5% by weight, is the highest among complex hydrides [62]. Nevertheless, during its dehydrogenation, very stable LiH is formed, reducing the useful hydrogen capacity [61]. Furthermore, quite high temperatures are required for the dehydrogenation of most complex hydrides by thermolysis, whereas only a few can be dehydrogenated reversibly, generally only in the presence of appropriate catalysts [28,35,63,64,65]. As a consequence, the direct use of borohydrides is not profitable for hydrogen storage.
Chemical hydrides, like complex hydrides, consist of lighter elements. Under standard conditions, they are generally liquids, which makes them easier to store and transport. Currently, ammonia and methanol, with high gravimetric and volumetric hydrogen storage capacities, are considered as hydrogen storage facilities [35]. The usefulness of these compounds commonly synthesised from natural gas is not the best for hydrogen storage. A significant quantity of energy in the form of heat typically needs to be introduced to release hydrogen when it is chemically bonded to a storage material. Additionally, it must be cleaned, which usually requires additional energy input [64,65,66,67,68].
Finding a hydrogen storage material with high capacity and suitable hydrogen sorption/desorption kinetics while maintaining cyclic stability and economic viability faces significant obstacles. An alternative to compressing hydrogen, apart from its liquefaction, may be metal hydrides.
Their greatest advantage is the higher volumetric density of hydrogen compared to free hydrogen in the gas or liquid phase. Storing hydrogen in metal hydrides is an expensive technology that has not been fully commercialised, with the exception of hydrogen storage alloys used in NiMH cells. In order to reduce the cost of producing metal hydrides, new low-temperature synthesis methods are being developed, described in [69]. It is expected that solid-state hydrogen storage will become widespread in the next 10–15 years. Currently, China has launched several demonstration projects of solid-state hydrogen storage power plants using AB2-MOF composite materials and an MgH2-LiBH4 system with a capacity to store 100 tons of hydrogen [69]. In Poland, hydrogen storage is carried out using high-pressure metal tanks of large volume. At the current stage of development of hydrogen technology, the use of the gas network as a hydrogen storage and distribution system for various industries seems to be the most justified for economic and operational reasons.

5. Polish Hydrogen Valleys

In October 2021, Poland was the first European Union country to conclude a “Sectoral Agreement for the Development of the Hydrogen Economy”, creating space for cooperation between various stakeholders, including representatives of entrepreneurs, science, public administration, business, and non-governmental organisations. It is the basis for creating hydrogen valleys to support the implementation of PHS [2] and contribute to the development of the hydrogen economy. The draft Polish Hydrogen Strategy envisages the creation of at least five hydrogen valleys—eight of them have been established to date (Central Hydrogen Valley, Masovian Hydrogen Valley, Pomeranian Hydrogen Valley, West Pomeranian Hydrogen Valley, Grater Poland Hydrogen Valley, Lower Silesia Hydrogen Valley, Silesia and Lesser Poland Hydrogen Valley, and Subcarpathian Hydrogen Valley). The locations of the hydrogen valleys in Poland are shown in Figure 3.
Hydrogen valleys are local hydrogen ecosystems operating within the entire hydrogen economy chain, including generation using renewable energy sources, transport, storage, and end uses, which connect various stakeholders. The creation of hydrogen valleys is intended to facilitate the use of national research and scientific potential, enable the integration of various sectors, create opportunities to find business partners, and optimise processes and costs in the field of hydrogen technologies. Moreover, their functioning may provide a number of practical tips for legislators and regulators on issues of safety, standards, norms, etc. The development of the technology and infrastructure in local communities and industrial plants will support the use of local renewable energy sources or municipal waste for the production of green hydrogen, which will guarantee stable supplies of electricity and heat, as well as transport fuel. As part of the EU partnership, the Polish valleys are to be included in the European Hydrogen Ecosystem. Hydrogen valleys are financed from EU, national, and regional funds, which are intended to encourage Polish entrepreneurs to invest private funds in the development of the hydrogen economy. Table 3 presents the scope of activities of the Polish hydrogen valleys along with their special achievements.
As part of the Masovian Valley, the first educational programme in Poland, “Hydrogen Academy”, was launched for students and graduates of universities regarding hydrogen [72]. Its participants will have theoretical and practical knowledge in the field of hydrogen technologies.

6. The Future of Hydrogen in Poland

Poland has a great potential to use hydrogen, as it is currently the third producer of this gas in the European Union and fifth in the world. This hydrogen is almost exclusively (95%) non-renewable hydrogen, so-called grey hydrogen, produced by the most common and most inexpensive method, mainly from natural gas in the process of steam methane reforming by refineries and chemical plants. The largest hydrogen producers in Poland are Grupa Orlen (Płock, Poland), Grupa Azoty S.A. (Tarnów, Poland), and Jastrzębska Spółka Węglowa (Jastrzębie-Zdrój, Poland). The produced hydrogen is practically entirely used for industry (chemical, petrochemical, metallurgical) and the food sector (Figure 4), and only a small part is traded on the market.
One of the alternatives to ensure Poland’s energy security may be the gasification of coal. The implementation of gasification technology for this raw material has not been used as an important element of the state strategy. Recently, political factors have played an important role in defining energy security standards, and their importance seems to be growing. There are known technological solutions that improve the efficiency of both coal gasification [73] and carbon dioxide capture and storage (CCS) systems [74]. However, the syngas obtained from coal gasification contains a number of toxic substances (sulphur, hydrogen chloride, ammonia, hydrogen cyanide, mercury, arsenic, selenium), the removal of which requires the use of large amounts of water. Furthermore, given the current prices of carbon raw materials and CO2 emission allowances in addition to the investment outlays, as well as the costs related to carbon dioxide capture and storage systems, the authors of [75] show this technology is not an attractive way of producing hydrogen for financial and environmental reasons.
Based on the cost analyses presented in report [76], in the period after 2030, the costs of hydrogen production using steam reforming technology will rise by approximately 40%, and by 2050, they will be 187% of the current level. With these assumptions, there is a need to develop technologies for capturing and storing carbon dioxide, also owing to the production of hydrogen from biomethane as a result of the anaerobic fermentation of biogenic waste. There is no functioning CCS system in Poland; we are at the stage of implementing pilot installations [77]. An attempt to implement the first CCS installation at the Bełchatów Power Plant over a decade ago was not successful. Two barriers, economic and social, posed as obstacles to its realisation. Nonetheless, we must be aware that with the drastically increasing costs of CO2 emissions, the use of CCS technology is necessary to carry out energy transformation in Poland. An emission-free hydrogen industry, including hydrogen production, storage, transport, and conversion to the desired forms of energy (mainly electricity, heat, and mechanical energy, as well as new fuels), as shown in Figure 5, is highly energy-intensive and requires access to low-cost electricity to achieve profitability and market competitiveness.
The latest report commissioned by the European Commission [78] presents the costs of energy production from coal, nuclear, gas, and renewable energy sources. Taking into account the environmental and health costs, it occurs that energy production from onshore wind farms is the least expensive. Zaik and Werle [79], using data presented in the work of Mc Kenn et al. [80], show that for European countries, the highest potential and the lowest costs of generating energy from wind are in Great Britain, Sweden, and Poland. Meanwhile, the limited development of wind energy on land caused by the so-called distance act and the blocking of EU funds from the National Reconstruction Plan until the first quarter of 2024 have delayed the modernization of the Polish energy sector.
It is worth noting that the forecast costs of hydrogen production from water electrolysis using electricity from renewable energy sources will decrease over the next 20 years [78], assuming a constant increase in the prices of CO2 emission allowances and decreasing infrastructure prices.
Even though the share of energy from renewable sources in the Polish energy mix increased to 30% in July 2023, the surplus energy generated from them, generated in periods of low electricity demand, cannot be fully utilised, owing to the lack of energy storage facilities in the energy system. Hydrogen production would stabilise the operation of renewable energy sources, enabling their maximum use when energy consumption is limited. Therefore, the further development of a new renewable energy generation capacity is closely related to the development of the hydrogen economy.
PHS assumes that by using P2G and G2P (power-to-gas and gas-to-power) installations [67], enabling the conversion and storage of electricity, it will be possible to utilise surplus energy from renewable sources to produce green hydrogen. The stored hydrogen can be used on site or transported to a collective hub and distributed further. When power is needed again, hydrogen can be used to produce energy. The development of the hydrogen market will be supported by the appearance of nuclear power plants in the Polish energy system, which are not very flexible either and generate significant energy surpluses that could be utilised to produce hydrogen. However, in the present Polish conditions, the date of construction of the first nuclear power plant remains an open question. Experience from recent years indicates a significant extension of its construction period. Moreover, the high capital costs of building a nuclear power plant will translate into higher costs of electricity production, which will affect the price of the obtained hydrogen. The costs of receiving, storing, and regenerating nuclear fuel must also be taken into account.
One of the goals of PHS concerns the production of hydrogen in new installations. Its implementation will be supported by research and development projects for low- and zero-emission hydrogen production technologies. The strategy also envisages the launch of installations using electrolysis, gasification, and pyrolysis, as well as steam reforming to produce hydrogen from water, biomass, biogas, and biomethane. The installed capacity of installations for the production of low-emission hydrogen in Poland is expected to be 50 MW by 2025, and at the end of the decade, by 2030, it is expected to be 2 GW. It is worth emphasising that this power is currently 0 MW, and Poland only has prototype installations created as part of ongoing research and development projects (the largest installed electrolysers have a power of 5 MW). An electrolyser with a capacity of 100 MW producing 13.6 thousand tonnes/year of green hydrogen is to be launched only in 2027 at the refinery in Gdańsk [81]. For the development of the hydrogen economy, it is therefore necessary to increase the pace of investment in new installations for the production of green hydrogen and to identify geographical locations where the deployment of large-scale installations will be the most profitable [82]. Currently, the transport sector is one of the most dependent on fossil fuels—it is estimated that 75% of CO2 emissions come from road transport. Therefore, hydrogen can play a key role in this area, since it can be used directly as a fuel in cars, trucks, buses, trains, and ships powered by fuel cells. The advantage of fuel cell electric vehicles (FCEVs) using hydrogen as a fuel is a longer range because of their higher energy storage density compared to battery electric vehicles (BEVs) [66].
The use of hydrogen as an alternative fuel in transport is the second goal of the Polish Hydrogen Strategy and an undoubted opportunity to replace fossil fuels in urban, road, and rail transport. By 2025, support will be provided to projects involving the operation of 100–250 zero-emission hydrogen-powered buses, which requires the construction of approximately 30 hydrogen refuelling and bunkering stations [2]. Presently, there are two publicly accessible hydrogen stations in Poland, in Warsaw and Rybnik, built by the Polsat Plus Group and the ZE PAK Group under the NESO brand [83]. In turn, another hydrogen station of the Orlen Group is being tested in Poznan. Another Orlen hydrogen station will be built in Katowice this year, and others will be put into operation by mid-2025 [84]. At present, there are 20 NesoBus hydrogen buses in the city of Rybnik. Two Solaris Urbino hydrogen 12 buses are currently being tested in Krakow, powered by fuel from a pilot installation supplied from the first HUB automotive-grade quality hydrogen production in Poland, launched by Orlen in 2021. In addition, activities leading to the gradual replacement of diesel trains and locomotives by their hydrogen-powered equivalents in places where traction electrification is not planned will also be supported. PESA Bydgoszcz created the first approved hydrogen locomotive in Poland. The vehicle can be used to its full extent and will ultimately operate on a siding of the production plant in Płock. The launch of pilot programmes aimed at implementing the use of hydrogen in heavy road, rail, sea, and river transport, as well as their further development until 2030, is also planned. Moreover, in the 2030 perspective, the hydrogen strategy provides for further development of the network of hydrogen refuelling stations and the implementation of 800 to 1000 more hydrogen-powered buses in addition to the production of synthetic fuels based on hydrogen [2].
The ecological effect of implementing the hydrogen strategy will be a reduction in the emissions of certain greenhouse gases and air pollutants. Reducing air pollution emissions should improve air quality, reduce the risk to human health, and improve living conditions. In order to determine the impact of the implementation of the hydrogen economy in Poland on the reduction in pollutant emissions, a detailed analysis [83] was carried out, which shows that at the national level, the implementation of the Polish hydrogen strategy will not produce significant ecological effects in the years 2030–2040 in terms of reducing greenhouse gases, nor will it have a measurable impact on reducing the costs of health and social care. In the Silesian Voivodeship and areas of Poland where PM2.5 dust emission standards are exceeded, it will be justified to increase the use of hydrogen in the heating sector in order to improve the health and quality of life of residents and reduce the external costs of energy production [83].
The penultimate group of activities supported in PHS concerns the efficient and safe transmission, distribution, and storage of hydrogen. Especially in the initial phase of development of the hydrogen market, its transport will take place primarily using road and rail transport (tank trucks, cylinder trucks). As the consumer demand for hydrogen grows, its transport in gaseous form can be carried out via new or existing gas infrastructure pipelines after appropriate modifications [85]. Suitable metallic materials for hydrogen pipelines are austenitic stainless steels resistant to hydrogen embrittlement. Lightweight composite materials based on carbon fibre-reinforced polymers, which are characterised by adequate resistance to hydrogen operating pressures, can also be used for hydrogen transport [86].
According to Poland’s national energy policy until 2040 [87], by 2030, Poland is to achieve the ability to transport through gas networks a mixture containing approximately 10% gases other than natural gas, e.g., hydrogen. Poland’s participation in the European Hydrogen Backbone Initiative, in which European companies cooperate to plan a pan-European dedicated hydrogen transport infrastructure, certainly has a very positive impact on the development of the hydrogen economy. In turn, both aboveground and underground tanks can be used for storage. The former includes depleted oil and gas fields, caverns (empty spaces in rock), and abandoned mines [88].
It should be emphasised that in the world, only storage facilities in salt caverns are currently used to store large amounts of hydrogen [89]. At present, there are no underground hydrogen storage facilities in Poland. The research results presented in [90,91] confirm that there are real possibilities of hydrogen storage in underground geological structures in Poland. As part of a research and development project, a cavern in Białogard was selected as a place to store hydrogen for electricity production. The maximum capacity of the cavern used in the project assumptions may range from 190,000 to 350,000 m3, which allows from 2000 to 3000 tons of hydrogen to be stored.
In the future, when implementing hydrogen technologies on a large scale, it will also be necessary to include aboveground reservoirs such as pressure vessels, which involve high-investment outlays. A future alternative is the further development of research on methods of storing hydrogen bound in solid materials, e.g., in metal hydrides or carbon nanostructures. It is worth adding that an interesting technological solution for hydrogen storage developed at the High Pressure Institute of the Polish Academy of Sciences is a safe hybrid (double-jacketed) hydrogen storage tank with a high density of stored energy with continuous monitoring of tightness. The innovative tank allows hydrogen to be stored and held at a pressure twice as high as in tanks currently available on the market and is intended for passenger cars [92].
The development of the hydrogen economy is strictly dependent on an appropriate legal framework; therefore, the development of a stable legislative environment regulating and supporting the functioning of the hydrogen market in Poland is called the “constitution for hydrogen” [93]. It will consist of draft amendments to applicable provisions, e.g., the Energy Law, and a number of new regulations, e.g., an act on supporting the production of hydrogen from renewable sources. The included legal provisions are intended to meet market needs, implement European Union regulations, and encourage investors to produce low-emission raw materials. The national law currently in force does not meet the needs related to an effective implementation of the hydrogen strategy, and even more so, does not fit the plans for the dynamic development of this innovative economic sector in Poland. Unfortunately, despite previous announcements that the “constitution for hydrogen” would be adopted in 2022, it has not been approved yet. This undoubtedly constitutes a huge barrier blocking the development of the hydrogen economy in Poland.

7. Polish Prototype Installations for Production and Storage of Hydrogen

As part of ongoing research and development projects, many prototype installations are being created. One of the most important is the world’s first small-scale and bidirectional green hydrogen production installation based on solid oxide cells with a power of 10 kW, operating in Elbląg at the Energa Kogeneracja heat and power plant, cooperating with the BB20 biomass unit of the heat and power plant. It is the result of a project called RSOC [94], conducted by the Faraday Research and Development Centre of the Energa Group and the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences in cooperation with the Institute of Energy. The employed solid oxide electrochemical cells can operate alternately in the electrolyser mode, producing hydrogen, or in the fuel cell mode, converting hydrogen into electricity. The pilot installation is based entirely on Polish patents, technology, and know-how that can be used in hydrogen production in addition to high-power energy storage installations. There is no doubt that the RSOC project is one of the Polish technological achievements for the development of the hydrogen economy.
In turn, a research team from the Faculty of Technical Physics and Applied Mathematics of the Gdańsk University of Technology developed a reactor for the pyrolysis of unsorted municipal and industrial waste W2H2 [95]. In one device, waste is pyrolysised and then the resulting reaction products are purified. The final product is char with a carbon content of approximately 60% and energy recovered in the form of gas with a high hydrogen content.
An important pilot project on a national scale is the green hydrogen production installation based on electrolysis implemented by the Pątnów–Adamów–Konin power plant complex (ZE PAK SA, Konin, Poland), co-financed from European funds [68]. The system will consist of two proton exchange membrane (PEM) electrolysers powered by renewable energy, both from a local photovoltaic power plant (60%) and from external suppliers (40%). The initial power of this unit is 2.5 megawatts, with the possibility of expansion to five megawatts. The hydrogen produced in the installation is already supplied to refuelling stations for passenger cars and buses throughout Poland.
In turn, the aim of the VETNI project implemented by Grupa Lotos together with the Institute of Energy and AGH University of Science and Technology in Krakow is to construct a pilot installation for the production of high-purity hydrogen based on solid oxide electrolysers (SOEs) powered by energy from renewable sources, integrated with refinery processes. The use of a new group of materials with a reduced Co content in the construction determines high efficiency (16 kg/day) in addition to operational stability of the electrolyser [96].

8. Conclusions and Prospects

−
The technologies and materials used in green hydrogen energy are more environmentally friendly but require large investment outlays, supplies of critical raw materials for electrolysers and fuel cells, and the consumption of large amounts of water.
−
The steam reforming of methane will be a bridge method of hydrogen production in the pursuit of zero emissions. With the drastically increasing costs of CO2 emissions, the use of CCS/CCUS technology will become economically profitable and will be an essential activity to carry out the energy transformation in Poland.
−
Gasification as a technology for the thermal processing of biogenic waste and one of the closed loop technologies has great potential for hydrogen production and can play an important role in achieving the sustainable development goals in Poland. This technology is currently at the level of research and development projects and implementations.
−
The Polish hydrogen economy is in the initial stage of development. Currently, the main barriers to the development of hydrogen energy in Poland are the lack of appropriate legal regulations enabling and supporting the development of an ecological hydrogen industry, high investment and operating costs of a hydrogen infrastructure, and the limited availability of electrolysers.
−
The condition for the development of the hydrogen economy in Poland is the simultaneous development of new capacities of renewable energy sources, primarily offshore and onshore wind farms. Nuclear power plants will provide significant support for the development of hydrogen energy.
−
In the long-term perspective of the development of the hydrogen market in Poland, the construction of a hydrogen terminal (similar to the LNG terminal), as well as the expansion of hydrogen pipelines, will be necessary to handle export/import trade.
−
Although there is currently no underground hydrogen storage facility in Poland, its construction should not pose any problems, taking into account the experience in the construction and operation of underground natural gas storage facilities.
−
Creating hydrogen valleys in Poland will support the use of research and development potential and should contribute to significant economic growth and the creation of new jobs.
−
Taking into account the growing demand for energy storage, it can be concluded that there is still a need to look for new technological solutions that are more economically beneficial and environmentally friendly.
−
To accelerate the development of hydrogen storage systems, it is recommended to use machine learning techniques, which will reduce the time and costs associated with conducting experiments on a large number of potential materials.
−
Hydrogen storage is recommended for use in the transport sector, seasonal energy storage, the flexibility of network operations, and for the integration of the electricity grid with the gas network.
−
The use of waste biomass or seawater for hydrogen production will certainly bring significant social and environmental benefits.
−
The development of hydrogen energy requires the drafting of international standards and regulations that are currently not available, as well as cooperation integrating the scientific community, industries, and the government.

Author Contributions

Conceptualization, K.G. and E.O.; methodology, K.G. and E.O.; formal analysis, K.G. and E.O.; data curation, K.G. and E.O.; writing—original draft preparation, K.G. and E.O.; writing—review and editing, K.G., E.O., G.W. and J.P.-W. All authors have read and agreed to the published version of the manuscript.

Funding

The work was supported by the Ministry of Science and Higher Education of Poland (Statutory Research BS/PB-200-301/2024). The work was carried out as part of project no. WZ/WBiIS/6/2023 and WZ/WBiIS/7/2023 at the Bialystok University of Technology.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Figure 1. Comparison of hydrogen with traditional fuels in terms of energy density [4,5,6,7].
Figure 1. Comparison of hydrogen with traditional fuels in terms of energy density [4,5,6,7].
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Figure 2. Hydrogen storage methods.
Figure 2. Hydrogen storage methods.
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Figure 3. Location of hydrogen valleys in Poland.
Figure 3. Location of hydrogen valleys in Poland.
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Figure 4. Industrial applications of hydrogen in Poland.
Figure 4. Industrial applications of hydrogen in Poland.
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Figure 5. Green hydrogen storage and conversion methods.
Figure 5. Green hydrogen storage and conversion methods.
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Table 1. Comparison of physicochemical properties of various fuels [11,12,13].
Table 1. Comparison of physicochemical properties of various fuels [11,12,13].
FuelFlammability Limits [vol. %]Octane NumberTemperature of Self- Ignition [°C]Combustion Speed [m s−1]
Hydrogen4–751305852.65–3.25
Methane5–161255400.37–0.45
Methane + 20% hydrogen fraction4.6–19.9
Methane + 60% hydrogen fraction4.4–26
Methane + 80% hydrogen fraction4.6–47.6
Propane2.2–9.6105490
Petrol1–7.687–98230–4800.37–0.43
Diesel fuel0.6–5.530254–285
Table 2. Hydrogen production technologies and their characteristics. Source: own study based on [3,18].
Table 2. Hydrogen production technologies and their characteristics. Source: own study based on [3,18].
Hydrogen Production TechnologyEstimated Proces
Efficiency [%]		Emission of CO2[kgCO2/
kg H2]		Hydrogen ColourAdvantagesDisadvantagesEstimated Hydrogen Production Cost [EUR/kg H2]
Hard coal gasification process30–4015–20blackwell-known and available technology, low efficiency high-emission technology, impurities in the raw material, low efficiency, fluctuations in the raw material prices, costs depending on the price of CO2 emission allowances1.3–2.8
Methane steam reforming (SMR)74–858–12.9 greyproven technology/infrastructure,
high efficiency, low cost		high-emission technology, variable natural gas prices, costs dependent on the price of CO2 emission allowances1.3–2.2
Hydrogen produced from fossil fuels combined with CO2 capture process (CCS) 2–4 bluelow-emission technologyhigh cost of CCS installation, dependence on fossil fuels1.2–3.6
Water electrolysis using nuclear energy 60–800–0.2pinkemission-free technologyhigh energy and water consumption, high prices and poor availability of electrolyzers, high cost of installing a nuclear power plant3.5 do 8.5
Water electrolysis using renewable energy sources60–800greenemission-free technologyhigh energy and water consumption, high prices and poor availability of electrolyzers, dependence on weather conditions3.5 do 8.5
Table 3. The scope of activities of the Polish hydrogen valleys. Own study based on [70,71].
Table 3. The scope of activities of the Polish hydrogen valleys. Own study based on [70,71].
Polish Hydrogen Valley (Year of Establishment)Scope of Activity/Achievements
Pomeranian (2019)the application of zero-emission hydrogen in public transport, production of green hydrogen from offshore areas, and production of electrolysers; Lotos Group implemented the Pure H2 project until 2023
Subcarpathian (2021) hydrogen buses, hydrogen in aviation, hydrogen in energy, green heat, and water pipelines; Polenergia is implementing the H2HUB Nowa Sarzyna project “Green Hydrogen Storage” with an application for project development assistance
Silesian–Lesser (2022)the production of 350 tH2/y low-emission hydrogen, green steel, and the decarbonisation of public transport; Orlen Południe launched a green glycol production plant; the creation of the hydrogen portal H2Poland.eu, supporting the development of the hydrogen economy in Poland and the Silesian–Lesser Poland Hydrogen Valley
Lower Silesian (2022) the production of green ammonia, green heat, and the use of green hydrogen in metallurgical processes, namely the production of green copper, hydrogen in river transport (hydrogen barges), hydrogen in public transport, and hydrogen storage; in 2022, two applications were submitted to an international consortium for the Horizon Europe programme for the development of a regional hydrogen economy; in 2023, the first commercial installation for the production of green hydrogen in Poland (electrolyser with a capacity of 5 MW, 720 tH2/y) powered by renewable energy (wind, PV) was launched; the produced hydrogen will be converted in a trigeneration installation (into heat, cold, electricity) and used as a green fuel
Mazovian (2022) the production of green hydrogen, synthetic fuels, biogas, the petrochemical industry, hydrogen in river transport, and public transport, namely the production of hydrogen buses and hydrogen refuelling stations; PKN Orlen is implementing the Hydrogen Eagle project and IPCEI called Hy2USE; the Hydrogen Academy project was also launched
Central (2023)hydrogen production from renewable energy, hydrogen haulers, hydrogen storage, renewable energy, green public transport, and hydrogen production from nuclear energy
West Pomeranian (2022) green ammonia production, low-emission maritime transport, low-emission river transport, ammonia collection infrastructure, integration around a large chemical company, and the Shore H2 Valley concept
Greater (2021)the production of clean hydrogen and hydrogen in housing, which is a project of the first housing estate in Poland heated with a zero-emission hydrogen boiler; hydrogen refuelling stations, the production of hydrogen buses, hydrogen in air transport; the “Economical 20250-H2 Greater Poland” project is being implemented
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Giza, K.; Owczarek, E.; Piotrowska-Woroniak, J.; Woroniak, G. Hydrogen Materials and Technologies in the Aspect of Utilization in the Polish Energy Sector. Appl. Sci. 2024, 14, 10024. https://doi.org/10.3390/app142110024

AMA Style

Giza K, Owczarek E, Piotrowska-Woroniak J, Woroniak G. Hydrogen Materials and Technologies in the Aspect of Utilization in the Polish Energy Sector. Applied Sciences. 2024; 14(21):10024. https://doi.org/10.3390/app142110024

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Giza, Krystyna, Edyta Owczarek, Joanna Piotrowska-Woroniak, and Grzegorz Woroniak. 2024. "Hydrogen Materials and Technologies in the Aspect of Utilization in the Polish Energy Sector" Applied Sciences 14, no. 21: 10024. https://doi.org/10.3390/app142110024

APA Style

Giza, K., Owczarek, E., Piotrowska-Woroniak, J., & Woroniak, G. (2024). Hydrogen Materials and Technologies in the Aspect of Utilization in the Polish Energy Sector. Applied Sciences, 14(21), 10024. https://doi.org/10.3390/app142110024

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