Hydrogen for Heating: Technologies, Challenges, and Opportunities

REVIEW Hydrogen for Heating: Technologies, Challenges, and Opportunities [version 1; peer review: 1 approved with reservations] Oleh Sokil , Nazar Podolchak, Irina Stetsiv , Mykhailo Zuiev , Bohdan Chepil Department of Financial and Administrative Management, Lviv Polytechnic National University, Lviv, 79013, Ukraine First published: 28 May 2025, 5:143 https://doi.org/10.12688/openreseurope.20432.1 Latest published: 04 Jul 2025, 5:143 https://doi.org/10.12688/openreseurope.20432.2 v1 Abstract Hydrogen is gaining prominence as a key enabler in the global shift toward low-carbon energy systems, yet its role in heating—particularly in residential, commercial, and industrial contexts—remains underdeveloped. This paper explores the potential of hydrogen-based technologies to decarbonize heating, focusing on technological innovations, economic feasibility, and regulatory frameworks. Drawing on a comprehensive review of literature, policy documents, and case studies such as the EU-supported H2Heat project, the paper examines developments in hydrogen production, storage, and distribution, with a special emphasis on green hydrogen and its integration into Combined Heat and Power (CHP) systems and heat pump technologies. The findings demonstrate the quick advancements in infrastructure prepared for hydrogen, electrolyzer efficiency, and renewable energy-based hybrid energy systems. High costs, infrastructure retrofitting, safety issues, and regulatory fragmentation are still problems, though. Hydrogen heating has a lot of potential, especially for hard-to-electrify industries and seasonal storage requirements, the study concludes, but its success hinges on concerted policy action, investment incentives, and international cooperation. By providing strategic recommendations for scaling hydrogen heating solutions and establishing them as a feasible part of sustainable energy transitions, the paper adds to the current conversation. Keywords hydrogen heating systems; green hydrogen; energy decarbonization; combined heat and power (CHP); heat pumps; hydrogen infrastructure; smart energy systems; public-private partnerships. Open Peer Review Approval Status 1 2 version 2 (revision) 04 Jul 2025 view version 1 28 May 2025 view Amandeep S Oberoi , Thapar Institute of Engineering and Technology, Patiala, India 1. Patrick Ehi Imoisili ,2. Any reports and responses or comments on the article can be found at the end of the article. Open Research Europe  Page 1 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 Corresponding author: Oleh Sokil ([email protected]) Author roles: Sokil O: Investigation, Methodology; Podolchak N: Project Administration, Supervision; Stetsiv I: Conceptualization, Visualization, Writing – Original Draft Preparation; Zuiev M: Formal Analysis, Resources; Chepil B: Methodology, Writing – Review & Editing Competing interests: No competing interests were disclosed. Grant information: This project has received funding from the European Union’s Horizon 2020 research and innovation programme - Horizon Europe call HORIZON-CL5-2022-D3-02-03 called “Innovative renewable energy carrier production for heating from renewable energies Euratom programme] under grant agreement No -101118318(Hydrogen from renewable energy for commercial building heating – a full supply chain demonstrationH2Heat). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Copyright: © 2025 Sokil O et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite this article: Sokil O, Podolchak N, Stetsiv I et al. Hydrogen for Heating: Technologies, Challenges, and Opportunities [version 1; peer review: 1 approved with reservations] Open Research Europe 2025, 5:143 https://doi.org/10.12688/openreseurope.20432.1 First published: 28 May 2025, 5:143 https://doi.org/10.12688/openreseurope.20432.1 This article is included in the Horizon Europe gateway. Open Research Europe  Page 2 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 Introduction Hydrogen is currently perceived as a critical energy carrier in moving towards a more sustainable and low-carbon economy for the world. It has been extensively studied due to its potential as a clean alternative to fossil fuels in different sectors, such as transportation, industrial processes, and power generation. However, applying it to heating applications-both residential and industrial-presents unique challenges and opportunities that are vital to the development of energy systems. Hydrogen is important for heating because it makes it possible to decarbonize energy consumption in buildings and industry, generally within industries that have traditionally had high carbon footprints. Current trends reflected by such researchers Chen et al. (2023); Benalcazar and Komorowska (2024) are toward increased deployment of hydrogen technologies for heat, encouraged by technology development, policy support, and environmental concerns. However, significant challenges remain in the development and deployment of hydrogen heating. Key challenges include infrastructure retrofitting; the economics of hydrogen production, storage, and distribution; and the technology readiness of end-use equipment. Finally, safety risks related to the high flammability of hydrogen must be taken into account and appropriately managed. Overcoming these challenges will require various approaches: research and development, policy and regulatory frameworks, and public-private partnership. This paper will attempt to review the state of the art in hydrogen technologies for heating, outline the main challenges which are still presenting significant barriers to wide-spread technology adoption, and set out opportunities that exist for overcoming these challenges to achieve a wider diffusion of hydrogen heating technologies. The paper will review these elements with the intent of contributing to the ongoing discourse on the role of hydrogen in accomplishing heating decarbonization and outlining some future research and policy directions that could quicken the deployment of hydrogen-based heating solutions. In this respect, hydrogen as a means of heating is very promising for reducing greenhouse gas emissions both in the residential and industrial sectors. Despite the promise of hydrogen for heating, there are a lot of challenges that face its adoption in scaling up and practical application. Many existing heating infrastructures, particularly those designed for conventional natural gas use, require varying degrees of retrofitting or, in some cases, complete overhauls to accommodate hydrogen, depending on the specific system configuration and hydrogen concentration. For instance, in the H2HEAT project at Chuimi SCS, partial blending of hydrogen was implemented without a full replacement of boiler systems. Nonetheless, the majority of conventional heating infrastructure is tailored to the physical characteristics of methane (CH4), not hydrogen (H2). Hydrogen’s lower molecular weight allows it to permeate seals more easily, increasing the risk of leaks; its higher diffusivity enhances the likelihood of leakage and explosion; and its broad flammability range imposes stricter safety requirements. Additionally, hydrogen can cause embrittlement in certain metals. Therefore, adaptation often requires replacing seals, valves, and burners; inspecting or substituting pipelines with H2-resistant materials; installing advanced leak detection and control systems; and retrofitting or completely replacing boilers with hydrogen-ready models. According to the UK Hydrogen Strategy, upgrading just the distribution infrastructure alone is estimated to cost several billion pounds (BEIS, 2021). Economic feasibility has become the second challenge to hydrogen heating systems at the moment, as long as their production-mostly via electrolysis with renewable feedstocks-costs a great deal. Hydrogen heating systems also require large storage and distribution facilities in order to achieve some kind of energy balance, given the low energy density compared with traditional fuels. Besides that, regulatory and safety issues are also major concerns. The highly flammable nature of hydrogen demands high standards for safety and standards that are not only uniform across various regions but also still under development for wide-spread facilitation of this fuel. The regulatory framework also lags behind technological advancement, making the gap between potential pilot projects and full-scale deployment wider. These are exacerbated by the slow market acceptance of hydrogen heating solutions due to limited consumer awareness and available alternative low-carbon heating technologies like heat pumps and biomass, which enjoy mature markets and policy support. These are problems that require, beyond technological innovations and investments, coordination at the policy and industry levels, as well as among the research community, for practical and economically viable solutions. The primary goal of this paper is to critically evaluate the state of affairs and future prospects of hydrogen as a significant energy vector for heating applications. To this end, it conducts a thorough analysis of the most recent technological advancements, a socio-economic and environmental issues analysis, and a strategic exploration of the opportunities that may present numerous opportunities for the spread of hydrogen-based heating systems. In particular, the main aims of paper are: • Review technological advancements: outline the current state of the art in hydrogen production, with a focus on green hydrogen derived from renewable resources, retrofitting existing heating systems, and new technological advancements that allow for the safe and effective use of hydrogen for heating. • Identify and analyze challenges: To look at the various technical, economic, and regulatory barriers that Page 3 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 currently impede the integration of hydrogen heating systems. Among those are infrastructure issues, cost competitiveness, market readiness, and regulatory compliance. • Explore opportunities for advancement: To point out possible pathways and innovative approaches to overcome existing challenges. This section will debate the role government policies will play, the use of financial incentives, public-private partnerships, and community engagement in promoting hydrogen heating solutions. In addition to offering strategic recommendations based on review and analysis, the paper will offer suggestions for accelerating the use of hydrogen for heating for all stakeholders, including academics, industry leaders, and policymakers. The ultimate goal of this paper is to contribute to the body of knowledge that supports the shift to a more sustainable heating sector and helps shape the practices and policies that will determine how hydrogen is used in energy systems around the world in the future. Materials and methods Technological developments in hydrogen heating have been widely studied, including adaptations of traditional heating systems such as hydrogen burners and boilers. Research by Marchenko and Smikhula (2023) demonstrated the viability of retrofitting existing natural gas boilers to operate on hydrogen, detailing modifications required and their impact on efficiency and emissions. The authors showed that condensing boilers offer superior performance due to their ability to recover a greater proportion of thermal energy—specifically, by condensing water vapor from flue gases generated during the combustion of methane (or natural gas). They also proposed specific boiler and burner designs suitable for hydrogen combustion and its mixtures with methane or natural gas. If pure hydrogen replaces natural gas in pipelines, the volumetric leak-age rate (m³/s) would increase by approximately 2.8 times. However, the associated energy loss would decrease by around 9.2%, reflecting the lower specific energy losses during hydrogen transport compared to methane. Green hydrogen integration into biorefineries facilitates local optimization, reducing both costs and the environmental footprint related to long-term storage and transport. The widespread availability of green hydrogen and biomass in rural settings presents unique possibilities for their synergistic use, as discussed by Giuliano et al. (2024). Studies like those by Matute et al. (2021) evaluate the costs of producing, storing, and distributing hydrogen in comparison to traditional fuels, making economic assessments a major area of focus. These studies frequently come to the conclusion that in order to make hydrogen competitive, substantial subsidies or technological advancements are required. Market potential analyses, such as those conducted by You et al. (2016), offer a thorough examination of the markets’ readiness for hydrogen heating technologies, highlighting important industries and geographical areas where hydrogen may be adopted early on because of advantageous regulatory and economic conditions. A breaf review of the policies regarding the use of hydrogen (H2) for heating purposes encompass national policies in Spain, as well as broader EU and international directives. Here’s an overview across these three levels: • National (Spain). Spain has increasingly focused on integrating hydrogen into its energy mix, especially in the context of its National Hydrogen Strategy and Hydrogen Roadmap: a commitment to renewable hydrogen (Green Hydrogen Organization, 2024). This strategy aims to develop green hydrogen production, primarily for industrial use, but it also explores the potential for hydrogen in heating applications within the residential and commercial sectors. Spain’s commitment to hydrogen aligns with its broader objectives for renewable energy and decarbonization by 2050. • European Union (EU). The EU's Hydrogen Strategy complements national plans like those of Spain. It promotes the adoption of green hydrogen, produced via electrolysis powered by renewable energy sources, as part of the bloc's transition to a carbon-neutral economy (EU energy policy, 2024). The strategy outlines investments and regulatory frameworks intended to scale up hydrogen production, infrastructure, and market deployment. For heating, the EU considers hydrogen as a viable option particularly in sectors and regions where electrification is less feasible. • Globally, hydrogen policies vary significantly but are gaining momentum as part of the energy transition dialogue. International bodies such as the International Energy Agency (IEA) and the International Renewable Energy Agency (IRENA) advocate for the role of hydrogen in achieving global energy and climate goals. These organizations provide guidelines and frameworks that encourage member countries to explore hydrogen as part of their energy strategies, including for heating purposes. Additionally, international collaborations and partnerships, such as the Hydrogen Council, promote policy development, market creation, and technology sharing across borders (Prysiazhniuk, 2023). Regulatory and safety considerations are also crucial, with works like Jansen and Reins (2024) and Melo et al. (2024) reviewing existing safety standards and regulatory policies that impact the deployment of hydrogen heating solutions. Detailed risk assessments, such as those by Rusin et al. (2024), offer guidelines for safe storage and handling practices in residential and industrial settings, addressing concerns related to hydrogen’s flammability. Trends also reveal a growing focus on decentralized hydrogen production as a means to reduce reliance on large-scale infrastructure and associated transportation costs. This approach aligns with policies promoting localized renewable energy use for hydrogen production, enabling tailored solutions for specific heating needs. Additionally, there is an increasing emphasis on integrating hydrogen systems with smart energy management technologies, allowing for dynamic adjustments Page 4 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 in production and distribution based on demand patterns and renewable energy availability. The evolution of hydrogen policies for heating demonstrates a clear trajectory toward achieving a low-carbon energy landscape. As these frameworks mature, continued emphasis on harmonization, innovation, and public engagement will be essential in realizing hydrogen’s full potential as a sustainable heating solution. Results The Nnabuife et al. (2023) paper provides a comprehensive analysis of various hydrogen production methods and their environmental impacts. It underscores the importance of considering environmental consequences alongside technical feasibility when assessing the effectiveness of these methods. The study clearly states that no single method emerges as superior, as each possesses distinct advantages and disadvantages concerning efficiency, scalability, cost-effectiveness, and environmental impact. Green hydrogen offers a viable solution for lowering carbon emissions in various global economic sectors. Its dual role as both an energy source and an industrial raw material, along with its capacity for emission-free production, makes it a crucial component in shifting towards a sustainable energy landscape. Green hydrogen is particularly valuable for its potential to reduce emissions in sectors that are difficult to decarbonize, including heavy industry, long-distance transportation, and applications requiring high-temperature heat, positioning it as a critical tool in broad-based climate change efforts (Banerjee & Lnu, 2024). The review reveals a dynamic field characterized by rapid advancements and a strong focus on overcoming the economic and technical barriers to hydrogen’s viability as a heating solution. While promising, the literature consistently highlights the need for supportive policies, further technological innovation, and comprehensive safety and regulatory frameworks to fully realize the potential of hydrogen in heating applications. Green hydrogen, produced through water electrolysis powered by renewable energy sources, is at the forefront of this transformation. The process involves splitting water into hydrogen and oxygen using electricity generated from renewable resources such as solar, wind, or hydroelectric power (Munyaneza, 2024). This method not only provides a carbon-neutral hydrogen source but also aligns with global sustainability goals by integrating renewable energy into the heating sector. The methodologies for integrating hydrogen into existing heating infrastructures are complex and varied. Several pilot projects across Europe and Asia have demonstrated the feasibility of converting existing natural gas networks to hydrogen. These projects typically involve a phased approach, starting with a blend of natural gas and hydrogen, which gradually transitions to 100% hydrogen. The technical considerations for such transitions include assessing the material compatibility of existing pipelines, upgrading seals and fittings to handle hydrogen’s unique properties, and implementing advanced monitoring systems to ensure safety and efficiency (Ozturk et al., 2023). Storage and delivery systems are another critical area of focus. Due to hydrogen’s low density, innovative solutions for efficient storage and transportation are crucial. Technologies such as liquid organic hydrogen carriers (LOHCs), metal hydrides, and advanced compression techniques are under development to address these challenges. Each method offers distinct advantages and limitations in terms of energy density, safety, and cost, influencing their suitability for different scales of operation and geographic conditions (Moradi & Groth, 2019; Reynolds et al., 2024). The storage and technical challenges involved in supplying hydrogen to combined heat and power (CHP) systems for heating are complex, primarily due to hydrogen’s inherent physical properties and the operational demands of CHP systems. Hydrogen has a very low density, necessitating its compression into high-pressure tanks to achieve an energy density practical for use. These tanks must be constructed from materials capable of handling high pressures while resisting hydrogen embrittlement, which can make metals brittle over time. The scalability of hydrogen storage is also critical, as CHP systems vary in size and may serve large facilities, requiring substantial hydrogen volumes. Efficient compression and decompression technologies are vital to maximize energy efficiency and minimize losses, ensuring operational cost-effectiveness. Moreover, CHP systems generally require high-purity hydrogen to maintain efficiency and prevent system damage, posing additional challenges in maintaining purity, especially after long storage periods. Safety is another significant concern, given hydrogen’s high flammability. Storage systems must be designed to prevent leaks and withstand accidents, incorporating robust safety protocols and detection systems. Innovative storage solutions, such as liquid organic hydrogen carriers (LOHCs) and metal hydrides, are under development to enhance hydrogen storage. LOHCs can store hydrogen at lower pressures and ambient temperatures, although they require complex chemical processes to release hydrogen. Metal hydrides offer high-density storage but face issues with slow kinetics and thermal management. Lastly, the cost of developing and implementing these advanced storage technologies must be considered, balancing initial setup and operational costs with the benefits of hydrogen use in CHP systems. Integrating hydrogen storage and delivery systems with existing CHP infrastructure requires careful planning and modifications, tailoring solutions to accommodate hydrogen’s unique characteristics. Addressing these multifaceted storage and technical challenges is crucial for the effective and efficient deployment of hydrogen in heating applications through CHP systems. Furthermore, the integration of hydrogen heating systems with smart energy management technologies is being explored to optimize energy use and enhance system responsiveness to Page 5 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 market and environmental conditions. These smart systems use real-time data analytics to adjust hydrogen production and distribution based on immediate energy demand, weather conditions, and electricity prices from renewable sources. To provide a comprehensive understanding of these methodologies, this section reviews several key studies and real-world applications that highlight the practical challenges and innovative solutions in the deployment of hydrogen heating systems. The discussion not only showcases current capabilities and limitations but also provides insight into future directions for research and development in hydrogen technologies. CHP and heat pump Other technologies. The exploration of technological advancements in hydrogen for heating reveals significant progress and some promising trends. Recent advancements in hydrogen production technologies, especially in electrolysis, have significantly enhanced efficiencies and reduced costs. These improvements are largely due to innovations in catalyst materials and electrolyzer designs, facilitating the broader adoption of green hydrogen production. Notably, the development of proton exchange membrane (PEM) electrolyzers has marked a considerable technological advancement. These electrolyzers operate at higher efficiencies and are capable of adjusting dynamically to the variable supply of renewable electricity, making them particularly suitable for applications such as hydrogen for heat. This technology’s relevance to our focus on hydrogen for heating applications warrants a detailed review and discussion (Nikzad et al., 2024; Zeng et al., 2024). In terms of heating technologies, the adaptation of existing heating systems to utilize hydrogen has progressed notably. Recent pilot projects in regions like Northern Netherlands Hydrogen Valley (socalled HEAVENN project) have successfully demonstrated that existing natural gas networks and boilers can be converted to use hydrogen with minimal modifications. These conversions involve replacing specific components such as burners and nozzles to accommodate hydrogen’s different combustion properties, and the results so far have shown that these systems can achieve comparable heating efficiencies and reliability (Squintani & Schouten, 2024). Storage technologies have also seen considerable advancements. The development of solid-state hydrogen storage methods, such as metal hydrides and complex hydrides, offers safer and more efficient ways to store and release hydrogen compared to traditional high-pressure tanks. These technologies reduce the risks associated with hydrogen storage and allow for more compact and scalable solutions suitable for both residential and industrial applications (Adaikalam et al., 2024; Zeng et al., 2022). Moreover, the integration of hydrogen heating systems with smart grid technologies has begun to take shape. These systems leverage IoT sensors and real-time data analytics to optimize hydrogen production, storage, and distribution, ensuring maximum efficiency and minimal wastage. This integration not only enhances the operational efficiency of hydrogen heating systems but also contributes to broader energy system stability by providing demand-response capabilities that can balance intermittent renewable energy sources (Agi et al., 2024; Loukriz et al., 2024). In summary, the technological advances in hydrogen for heating are substantial, addressing many of the limitations that have historically hindered the deployment of hydrogen as a mainstream energy carrier. However, continuous innovation and improvement are needed to overcome remaining challenges related to cost, scalability, and system integration. The assessment of technological advances in the use of hydrogen, referred to as hydroxy, for heating purposes involves a comprehensive evaluation of recent innovations and persistent challenges. Hydrogen offers a promising pathway for decarbonizing the heating sector, traditionally reliant on fossil fuels, through significant strides in production, storage, and utilization technologies (Rincon et al., 2024). In the realm of hydrogen production, the efficiency and sustainability of electrolysis, a process that splits water into hydrogen and oxygen using electricity, are pivotal. Innovations in this area, particularly in electrolyzer technology such as alkaline and proton exchange membrane (PEM) systems, have reduced energy consumption and operational costs. These advances have been driven by breakthroughs in catalyst materials and membrane technologies, making green hydrogen, produced using renewable energy sources like solar or wind, a more competitive option for heating applications (Gado et al., 2024). Storage solutions for hydrogen also represent a critical area of technological development. The challenges posed by hydrogen’s low density and high flammability have led to innovative storage methods, including metal hydrides and liquid organic hydrogen carriers (LOHCs) (Sung et al., 2025). These technologies allow for safer and more efficient hydrogen storage at higher densities than conventional high-pressure tanks, addressing safety concerns and enhancing the practicality of hydrogen for both residential and commercial heating systems. The integration of hydrogen into existing heating infrastructure has seen considerable advancement through pilot projects and the development of new technologies. Innovations such as hydrogen-ready boilers and burners, which can operate on pure hydrogen or a hydrogen-natural gas blend, facilitate the retrofitting of existing systems. This gradual integration allows for the use of hydrogen as the infrastructure and supply chains evolve, as demonstrated in projects across the Northern Netherlands, where municipal heating systems have been successfully converted to hydrogen (Broersma et al., 2024). Furthermore, alongside technological advancements, improvements in regulatory standards and safety protocols are essential to support the safe deployment of hydrogen heating systems. These enhancements address public and regulatory concerns by incorporating advanced sensor and detection systems into installations, ensuring safe operation. Page 6 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 Despite these promising developments, challenges remain that must be addressed to fully leverage hydrogen’s potential in heating. The high initial costs associated with establishing hydrogen production facilities and retrofitting infrastructure, along with the efficiency losses in energy conversion, continue to be significant barriers. These issues underscore the need for ongoing research and development to improve the efficiency, safety, and cost-effectiveness of hydrogen technologies. The dynamic field of hydrogen technology for heating is characterized by rapid innovations aimed at overcoming technical and economic barriers. As these technologies continue to evolve and become more cost-effective, hydrogen is increasingly positioned as a key component in achieving a sustainable and low-carbon heating future. This ongoing transition is supported by a blend of technological advancements, regulatory enhancements, and pilot projects that collectively demonstrate hydrogen’s viability as a transformative energy solution for heating. H2heat project. In the context of exploring the latest technologies for utilizing hydrogen (H2) for heating purposes, it’s essential to focus on developments that go beyond the production aspect, such as electrolysis, and look more into how hydrogen is applied in heating systems. Key technologies that are shaping the use of hydrogen for heating include Combined Heat and Power (CHP) systems, the integration of CHP with heat pumps, and innovations in hydrogen transport such as tube trailer modifications (Ge et al., 2023). Combined Heat and Power (CHP) Systems: CHP systems, also known as cogeneration systems, generate electricity and capture the heat that would otherwise be wasted to provide useful thermal energy. When these systems are powered by hydrogen, they offer a highly efficient use of fuel, which can significantly reduce greenhouse gas emissions compared to conventional fossil fuel systems. The efficiency of hydrogen CHP systems is particularly notable because they can achieve energy efficiency rates of over 80%, compared to traditional power plants which often have efficiencies around 50%. This makes hydrogen CHP a compelling option for district heating systems, industrial applications, and residential heating, especially in regions with high demands for both heating and power (Ge et al., 2023). CHP combined with heat Pumps – main innovation of the H2Heat project. A significant innovation in the H2Heat project is the integration of CHP systems with heat pumps. This hybrid approach leverages the strengths of both technologies: the CHP system efficiently generates electricity and provides heat, while the heat pump can use a fraction of the electricity generated to extract heat from the external environment, thereby enhancing the overall efficiency of the system. This combination allows for greater flexibility and efficiency in temperature control and energy use, making it particularly effective in climates with variable heating needs. The integration also aims to maximize the utilization of green hydrogen, aligning with sustainability goals by reducing reliance on grid electricity and lowering carbon footprints. Tube trailer modifications for hydrogen transport. The transport of hydrogen to various points of use, such as residential areas or industrial sites, is crucial for the widespread adoption of hydrogen heating technologies. Tube trailers, which are high-pressure tanks mounted on trailers, have traditionally been used to transport compressed gases. Recent modifications in these trailers include advancements in materials and engineering to safely and efficiently transport hydrogen. Innovations such as the use of lightweight composite materials help increase the payload and reduce transportation costs (Suvar et al., 2024). Moreover, advancements in tank design to handle higher pressures enable these trailers to carry larger quantities of hydrogen, improving the economics of hydrogen distribution and making it more accessible for heating applications. The use of hydrogen for heating is advancing through innovative technologies that enhance energy efficiency and sustainability. The integration of CHP systems with heat pumps represents a forward-thinking approach to leveraging hydrogen’s potential in heating, providing a model for future developments. Meanwhile, improvements in the infrastructure for hydrogen transport, like tube trailer modifications, play a crucial role in addressing logistical challenges, making hydrogen a more viable and attractive option for heating needs across various sectors. These technologies not only promise to improve the efficiency and sustainability of heating systems but also contribute to broader efforts to decarbonize energy systems globally. One of the main characteristics that differentiate H2 from CH4 it is its minimum auto-detonation temperature, which is the temperature above which the gas can be ignite without any external influence. In the following picture you can appreciate the auto-detonation temperature for each kind of gas (Figure 1): Figure 1. Autoignition temperature of selected gases: hydrogen (H2) compared to methane (CH4) and propane (C3H8). Page 7 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 Within a combustion engine, the different basic consecutive stages, through which the gas passes before it reaches the combustion chamber of an engine, are : Airgas mixer, turbocharger, throttle valve and combustion chamber. As there is an increase of temperature in those stages, the probability of having ignition, and thus misusing the energy of H2 and having material damages is high. Therefore, the conventional way to prepare the gas for the engine with a conventional CHP only allows 10% of H2 mixed with CH4. 2G has been working on special materials achieving that the Agenitor 2G engine allows until 30–40% (depending on the quality of the natural gas) of H2 through the conventional way. For 100% of H2, without any mixture, 2G designed special injectors which allow the mixture H2-air in the combustion chamber and thus uses the maximum energy from the gas. For the H2Heat project 2G proposes the Agenitor404 cogeneration unit. The unit needs 101,8m3/h H2 to produce 115Kw electric and 129KW thermal power. 2G proposes an adapted double Heat Pump system to create a high water temperature heater of up to 82°C. It is not possible to reach this temperature with a single air-to-water heat pump. The first, air-to-water heat pump, raises the water temperature from 30°C to 35°C. The second, water-to-water Heat Pump, will use this water at 35°C as a heat source to raise the water temperature to 82°C. Combined Heat and Power units (CHP) have been conceived to use all the energy of the engine, which produces electricity through the generator, and all the hotness produced during the process in the engine and in the exhaust gas, is harnessed in form of heat. Thus, almost all the energy contained in the gas is used in form of useful energy. On the other hand, the heat pump produces heat energy out of electricity, with the special feature of increasing the thermal output compared to electricity. This means that with a heat pump we obtain a thermal power output that is twice or more the electrical power input. In an application like an hospital, where heat energy is most demanded, the combination of both technologies allows the production of heat in the most efficient way. Thus with an engine of 115KW electric and 129KW thermic (total power 244KW), we will achieve 350KW heat power using hydrogen as fuel. We present a renewable high efficiency energy production, which can be feed with the surplus energy from the renewable production of a wind power plant. Identify and analyze challenges. Despite the promising technological advances, several challenges remain that impede the broader adoption of hydrogen as a heating solution. One of the primary challenges is the cost associated with the production of green hydrogen. Although technological improvements have reduced costs to some extent, the production of hydrogen through electrolysis remains expensive due to high energy requirements and the cost of electricity from renewable sources. This is compounded by the need for substantial investments in infrastructure to support large-scale hydrogen production and distribution. Regulatory barriers further complicate the deployment of hydrogen technologies. The lack of harmonized standards and regulations across different regions creates uncertainty for investors and operators. Without clear and consistent regulatory frame-works, the risk associated with large-scale deployment of hydrogen technologies remains high, discouraging investment and innovation in this area. Detealy expanding on the challenges and barriers to the deployment of hydrogen technologies for heating, there are several factors to consider that complicate its adoption compared to direct use of renewable electricity and other energy sources: • Cost and efficiency of direct heating with renewable electricity. Directly using renewable electricity for heating, such as through electric resistance heaters or heat pumps, can be cheaper and more efficient in certain contexts. Heat pumps, in particular, offer high efficiency by transferring heat rather than generating it, often resulting in lower operational costs compared to producing hydrogen through electrolysis and then using it for heating. • Hydrogen conversion and heat production efficiency. Hydrogen's role as an energy carrier involves conversion losses. Electrolysis itself is only about 60–80% efficient, and additional energy is lost when hydrogen is converted back to electricity or heat, making it less efficient compared to direct heating methods or heat pumps powered directly by renewable energy. • Safety concerns. Hydrogen poses significant safety challenges due to its high flammability and smaller molecular size, which can lead to leaks. For combined heat and power (CHP) systems that use hydrogen, these risks necessitate robust safety measures, complicating deployment and increasing costs. • Standards and regulations. The deployment of hydrogen technologies requires high safety and operational standards. The lack of harmonized standards and specific regulations for hydrogen use in different regions creates barriers for consistent deployment and increases the investment risk. • Noise issues. Both electrolysis equipment and CHP systems can generate significant noise, which may require additional mitigation measures to be acceptable in residential or commercial areas. • Regulatory and permitting hurdles. National and local regulations and the permitting process for new technologies like hydrogen installations can be cumbersome and slow, posing significant barriers to rapid deployment. Page 8 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 • Public opposition. There can be substantial public resistance to new technologies, especially those involving flammable or hazardous substances like hydrogen. Public concerns about safety, environmental impacts, or changes to local landscapes can delay or block projects. • Life cycle carbon emissions. Assessing the full life cycle carbon emissions of hydrogen production, especially if not all electricity used is sourced from renewables, is crucial. It's necessary to evaluate whether using hydrogen for heating results in a net reduction of greenhouse gases compared to other heating technologies. • Comparison with other carriers like methanol. Methanol can also be used as an energy carrier and has some advantages over hydrogen, such as being liquid at room temperature, which simplifies storage and transport. Evaluating whether hydrogen or methanol (or another carrier) is the best option for heat production requires a comprehensive analysis of efficiency, safety, infrastructure, and environmental impact. The environmental impact of hydrogen production, particularly blue hydrogen, which involves carbon capture and storage (CCS), is a subject of ongoing debate (Faber et al., 2025; Lan & Yao, 2022). While blue hydrogen is seen as a stepping stone towards a hydrogen economy (Idris-Idah et al., 2024), concerns about the efficiency of CCS technologies and the ultimate fate of captured carbon highlight the need for stringent environmental assessments and robust regulatory oversight. These challenges underscore the need for a coordinated approach that includes technological innovation, regulatory reform, and public engagement to realize the full potential of hydrogen heating systems. Addressing these issues will require collaborative efforts from government bodies, industry stakeholders, and the research community. Explore Opportunities for Advancement. The challenges identified present significant opportunities for advancement in the field of hydrogen heating. The increasing focus on decarbonization globally provides a strong impetus for the development and deployment of hydrogen technologies. Governments and international agencies can play a pivotal role by providing funding for research and development and by establishing incentives for the adoption of hydrogen technologies, such as subsidies, tax breaks, and grants. There is also an opportunity to leverage advancements in renewable energy technologies to reduce the cost of green hydrogen production. As the cost of solar and wind energy continues to decline, coupling these energy sources directly with electrolysis can make hydrogen production more economically viable. Moreover, the development of decentralized hydrogen production facilities can help reduce transportation costs and energy losses, making hydrogen more accessible for local heating applications (Cortez et al., 2024). National-international partnerships can be instrumental in accelerating the development of hydrogen infrastructure. By sharing risks and resources, these partnerships can tackle large-scale projects that might not be feasible for individual entities. Such collaborations can also foster innovation through the exchange of knowledge and expertise between the domestic and international experience (Sokil et al., 2022; Zbarsky et al., 2020). The H2HEAT project is an example, supported by the EU’s Horizon program during 2023–2028, exemplifies a strategic initiative to harness the potential of hydrogen in transforming heating solutions within the commercial sector. This project demonstrates the complete value chain of green hydrogen production from renewable energy and its utilization in commercial building heating, particularly within hospital facilities in the Canary Islands. The H2HEAT project features a robust consortium of participants, each contributing unique expertise to ensure the project’s success: • Platform Oceanic of the Canary Islands (PLOCAN) - Coordinates the project, leveraging its maritime research facilities to support hydrogen production. • Esteyco S.A (EST) - Provides engineering expertise and integrates offshore renewable energy solutions. • Neodyne Ltd - Focuses on the advanced energy management systems essential for integrating hydrogen production with renewable energy sources. • Stargate Hydrogen Solutions OÜ - Specializes in the development of innovative electrolysis technologies, crucial for efficient hydrogen production. • 2-G - Implements hydrogen-powered cogeneration systems that significantly enhance heating efficiency. • International Consortium of Research Staff Associations Ltd (ICoRSA) - Contributes to policy development and research dissemination. • Cluster Maritime Canaria (CMC) - Supports with maritime and logistical expertise, fostering regional development. • Canary Islands Health Service (SCS) - Acts as an enduser, applying hydrogen solutions to decarbonize hospital heating systems. • European Marine Energy Centre Ltd (EMEC) - Provides expertise in marine energy and its application in hydrogen production. • Government of the Canary Islands (GobCan) - Supports regulatory and policy frameworks to facilitate project implementation. • Scientific Park Lviv Polytechnic National University (SPLP) - Engages in research and development, particularly in materials and technology innovations for hydrogen applications. The H2HEAT project aims to establish a replicable model for hydrogen production and utilization that could be extended across the Canary Islands and beyond. A schematic layout of hydrogen production facilities is presented in Figure 2. Page 9 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 Open Peer Review Current Peer Review Status: Version 1 Reviewer Report12 June 2025 https://doi.org/10.21956/openreseurope.22110.r54837 © 2025 Oberoi A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Amandeep S Oberoi Thapar Institute of Engineering and Technology, Patiala, Punjab, India The presented manuscript is focused on unwinding the role of hydrogen indecarbonize heating and delve into literature pertinent to hydrogen production, storage and distribution. As such the topic is worth exploring and gives a comprehensive reporting onadvancements in infrastructure prepared for hydrogen, electrolyzer efficiency, and renewable energy-based hybrid energy systems. I found most of the paper to be well written however, it requires a revision before recommending it for indexing. I urge authors to revise the paper as per the below comments: 1) Figure-1, Label on the y-axis is missing. Is the temperature marked in degree Celsius or K or F? 2) Text in Figure-2 and 3 is not readable. Kindly increase the size and resolution of these images. 3) Energy expenditure associated with compressing the hydrogen gas or storing it in liquid state at cryogenic temperatures is not talked about. Comparatively, solid stage hydrogen adsorption require lesser or no energy expenditure. Kindly throw some light on it. 4) Cost of electricity produced from renewable sources for powering electrolyzer may vary geographically. For an instance, cost of electricity produced from solar PV in countries (like, India) experiencing more sunlight would be low compared to the countries near north or south pole (for example, Canada). So, would be the variation in price of Green Hydrogen production. Kindly comment on it and add the relevant literature in the paper. 5) Cost of different types of compressed hydrogen storage tanks also varies as per the pressure they can handle. For example, Type-I, Type-II, Type-III, Type-IV, and Type-V tanks used for compressed H2 storage. Kindly elaborate on it and include it in the paper. 6) Adding a polymer lining by thermal spray coating or similar methods could reduce the problem of hydrogen embrittlement in the existing metallic pipelines used for CNG transportation. Think on these lines and added literature on it in the paper. Open Research Europe  Page 16 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 7) Instead of combusting hydrogen in boilers, why can't electric heaters be used for heating powered by electricity produced using PEM fuel cells that required H2 and air? Comment on it please. 8) Hydrogen fuel and fuel cell technology are foreseen as future to replace conventional fossil fuels for stationary and mobile applications. In particular, fuel cell could produce electricity using H2 and air by giving out just water and absolutely no emissions. Kindly compare it with the firing of hydrogen in boilers for heating and add the supporting lietrature. References 1. Singla M, Nijhawan P, Oberoi A: Hydrogen fuel and fuel cell technology for cleaner future: a review. Environmental Science and Pollution Research. 2021; 28 (13): 15607-15626 Publisher Full Text 2. Yadav S, Oberoi A, Mittal M: Electrochemical hydrogen storage: Achievements, emerging trends, and perspectives. International Journal of Energy Research. 2022; 46 (12): 16316-16335 Publisher Full Text 3. Singla M, Nijhawan P, Oberoi A: Cost–benefit comparison of fuel cell–based and battery‐based renewable energy systems. International Journal of Energy Research. 2022; 46 (2): 1736-1755 Publisher Full Text 4. Shin H, Ha S: A Review on the Cost Analysis of Hydrogen Gas Storage Tanks for Fuel Cell Vehicles. Energies. 2023; 16 (13). Publisher Full Text 5. Magliano A, Perez Carrera C, Pappalardo C, Guida D, et al.: A Comprehensive Literature Review on Hydrogen Tanks: Storage, Safety, and Structural Integrity. Applied Sciences. 2024; 14 (20). Publisher Full Text 6. Wang Z, Wang Y, Afshan S, Hjalmarsson J: A review of metallic tanks for H2 storage with a view to application in future green shipping. International Journal of Hydrogen Energy. 2021; 46 (9): 61516179 Publisher Full Text 7. Muthukumar P, Kumar A, Afzal M, Bhogilla S, et al.: Review on large-scale hydrogen storage systems for better sustainability. International Journal of Hydrogen Energy. 2023; 48 (85): 3322333259 Publisher Full Text Is the topic of the review discussed comprehensively in the context of the current literature? Yes Are all factual statements correct and adequately supported by citations? Partly Is the review written in accessible language? Yes Are the conclusions drawn appropriate in the context of the current research literature? Partly Competing Interests: No competing interests were disclosed. Reviewer Expertise: electrochemical hydrogen adsorption in porous mediums, green hydrogen production, PEM electrolyser, PEM fuel cell, reversible fuel cell. Open Research Europe  Page 17 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025 I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Author Response 19 Jun 2025 Oleh Sokil Ось коротка відповідь рецензенту англійською мовою: Response to Reviewer We sincerely thank Dr. Amandeep S. Oberoi for the careful review and constructive comments provided on our manuscript. We highly appreciate the thoughtful suggestions, which have contributed significantly to improving the clarity and completeness of our work. All of the reviewer’s recommendations have been carefully addressed and incorporated into the final version of the manuscript. This includes textual additions, updated figures with improved resolution, and integration of relevant literature to reflect the points raised. We are grateful for the insights and believe that the revised manuscript is now much stronger as a result. Thank you once again for your valuable feedback and support. Competing Interests: No competing interests were disclosed. Open Research Europe  Page 18 of 18 Open Research Europe 2025, 5:143 Last updated: 17 DEC 2025