An International Review of Hydrogen Technology and Policy Developments, with a Focus on Wind- and Nuclear Power-Produced Hydrogen and Natural Hydrogen

Abstract

The potential for hydrogen to reshape energy systems has been recognized for over a century. Yet, as decarbonization priorities have sharpened in many regions, three distinct frontier areas are critical to consider: hydrogen produced from wind; hydrogen produced from nuclear power; and the development of natural hydrogen. These pathways reflect technology and policy changes, including a 54% increase in the globally installed wind capacity since 2020, plus new signs of potential emerging in nuclear energy and natural hydrogen. Broadly speaking, there is a considerable number of studies covering hydrogen production from electrolysis, yet none systematically examine wind- and nuclear-derived hydrogen, natural hydrogen, or the policies that enable their adoption in key countries. This article highlights international policy and technology developments, with a focus on prime movers: Germany, China, the US, and Russia.

1. Introduction

In his 1875 novel, The Mysterious Island, Jules Verne presciently described hydrogen as a pivotal energy source for the future [1]. In recent decades, writing about the development of a hydrogen economy and its related transition reflects ebbs and flows in societal interest as well as drivers [2,3,4,5,6]. Today, more than a century after Verne’s glimpse into the future, there are new signs of interest in, and conceptualizations of, how to harness hydrogen (Figure 1 and Figure 2, Appendix A—

Table A1. Publications on Hydrogen through 17 March 2025 [13].

Coverage	1st Year Reported	Total Publications
Any on hydrogen	1865	1,709,432
Hydrogen production	1873	211,417
Natural hydrogen	1898	77,728
Hydrogen storage	1908	84,291
Hydrogen production and nuclear energy/power	1938	4266
Hydrogen and hybrid system	1956	14,706
Hydrogen production and wind energy/power	1966	4808

) [7], reflected in the considerable increase in related research and policy initiatives (see also Figure 3) [8,9]. These developments are situated in an era now defined by clean energy and decarbonization priorities. In line with such energy priorities, hydrogen has considerable potential to be a pathway for a low-carbon transition, energy security, and for attaining deep decarbonization at scale, if derived with a low-carbon or zero-carbon method.

Importantly, there is no consensus on key definitions for clean, carbon-based, and energy transition terms, but there are reasonable, working definitions. Clean energy generally refers to energy that does not pollute, and decarbonization typically explains a process or data trend reflecting a reduction in carbon emissions and often greenhouse gases. An energy transition is a “considerable shift in the nature or pattern of how energy is used within a system, including the type, quantity, or quality of how energy is sourced, delivered, or utilized. This can be a planned or unplanned change that encompasses the emergence and decline of an energy industry, together with geopolitical, economic, social, and ecological factors that connect to all stages of energy utilization” [10]. A low-carbon transition may be understood as a process that reduces the emission of carbon in an energy system. This can include shifting away from fossil fuels, increasing energy efficiency, and/or adopting carbon-limiting technologies, such as carbon capture and storage, among other possibilities [11]. Deep decarbonization refers to a proactive and generally long-term strategy that aims to achieve near-zero greenhouse gas emissions from all sectors [12]. Low-carbon hydrogen essentially refers to hydrogen produced through processes that considerably reduce greenhouse gas (GHG) emissions relative to traditional methods. Zero-carbon hydrogen takes the distinction further, indicating hydrogen that is produced in such a way that no greenhouse emissions are generated in the process. (For a discussion of standards on low and zero-carbon hydrogen, see Section 2.3.3.)

Figure 1. Conceptualization of 19th century hydrogen electrolysis, generated by AI (DALL-E, 24 October 2024).

Figure 1. Conceptualization of 19th century hydrogen electrolysis, generated by AI (DALL-E, 24 October 2024).

Figure 2. Conceptualization of 21st century hydrogen production from wind and nuclear power, distribution, storage, and marine transport, generated by AI (DALL-E, 24 October 2024).

Figure 2. Conceptualization of 21st century hydrogen production from wind and nuclear power, distribution, storage, and marine transport, generated by AI (DALL-E, 24 October 2024).

Figure 3. Publications on hydrogen through to 17 March 2025 [13]. Note: * reflects reporting for part of a year.

Figure 3. Publications on hydrogen through to 17 March 2025 [13]. Note: * reflects reporting for part of a year.

Currently, new opportunities for low- or zero-carbon hydrogen are presented by a 54% growth in global installed wind capacity, the resurgence of the nuclear sector, technology advances, and discoveries of natural hydrogen [14,15,16,17,18,19,20,21,22]. As a high-density, combustible fuel that produces no carbon emissions at the point of use, hydrogen may serve as a technically feasible strategy to decarbonize ‘hard-to-abate’ areas, such as sectors where direct electrification is unlikely or inefficient. These sectors include heavy industries whose operations require intense heat, such as steel and cement production, as well as long-distance transportation, including maritime shipping, aviation, and heavy-duty trucking.

In addition to the benefits of decarbonization, hydrogen production with electrolysis (the splitting of water, a low-carbon hydrogen method) also directly addresses the intermittency and variability of many renewable energy sources. By utilizing surplus electricity from renewable sources such as wind and solar power during periods of peak generation, electrolysis allows for the conversion of excess power into chemical energy stored in hydrogen, in turn enhancing grid stability and enabling a more resilient and flexible energy system.

1.1. The Global Hydrogen Playing Field

Looking more broadly at hydrogen’s use today, global demand has more than tripled since 1975 [23], with demand in 2023 equaling more than 97 million tons, and estimated to be nearly 100 million tons in 2024 [8]. To date, production has been carried out largely with unabated fossil fuels, primarily via steam methane reformation of natural gas without carbon capture and storage and mostly driven by fertilizer production and refining [8]. While low-carbon hydrogen and net-zero energy feature prominently in current energy planning [8,24,25], less than 1% of the global demand for hydrogen is being met by lower-carbon approaches [8]. Despite the current supply asymmetry, low-carbon hydrogen has considerable potential to play a pivotal role.

When considering hydrogen, part of this energy carrier’s appeal lies in its high mass energy density (significant energy, but little weight), as well as its long-duration storage capabilities and diverse applications [7]. Importantly, hydrogen can be produced widely across regions through a range of low-carbon approaches that utilize renewable or nuclear energy, or fossil fuels with carbon capture, enabling lower emissions. Natural hydrogen may also be tapped from numerous regions as a form of low-carbon energy. Such low-carbon approaches allow regions to leverage local resources and capabilities, while fostering energy security and also meeting net-zero priorities. These attributes, including hydrogen’s potential for decentralized production, make it a key asset for enhancing energy system resilience [26].

The areas that are most likely to adopt hydrogen by the mid-century are the road, aviation, and maritime industries [8]. For adoption to occur at scale, infrastructure will need to be built out or repurposed, including hydrogen pipelines and refueling stations [27]. The scale-up and cost-competitive manufacturing of electrolyzers will also be necessary for increased production of low-carbon hydrogen, despite electrolysis being used for at least two centuries [28,29]. In the electricity sector, competitiveness must also improve and/or have more public support in order for hydrogen-fueled turbines or stationary fuel cells to bridge what some call ‘the last-mile decarbonization of the energy system’ relative to long-duration energy storage technologies and carbon capture, utilization, and storage [27].

Signs of momentum are evident in international summits, intergovernmental organization activity, and integrated strategies, where the role of hydrogen in a cleaner, lower-carbon energy future is often highlighted [8,30,31,32,33]. In the 28th Conference of Parties, for example, a Clean Hydrogen Declaration of Intent was signed by 39 countries, supporting collaboration and standard harmonization that could accelerate the development of an international market and foster cross-border trade [33,34]. Relatedly, national governments have also been putting forward strategies to increase hydrogen deployment through policies, regulations, and incentives [9].

1.2. Methods and Structure of the Remaining Article

The aim of this review article is to highlight key hydrogen technology and policy developments, with an emphasis on emergent and understudied areas, specifically wind- and nuclear power-produced hydrogen via electrolysis and sourcing through natural hydrogen. To achieve this, it draws on reviews of policies, projects, and bibliometric trends, along with reviews of the literature on technology, infrastructure, and market developments. Key platforms/tools were used, including Scopus, Web of Science, IEA and IRENA Policies, IEA Hydrogen Projects, and the Baker McKenzie Global Hydrogen Tracker. For countries where top-ranked adoption is evident (i.e., prime movers), policies were examined more closely.

The remainder of this article is organized as follows: Section 2 outlines current enabling conditions and discusses types of system change, detailing aspects such as storage and pipelines. Section 3 follows with a summary-level review of global hydrogen projects and policy trends. It then delves into specific technology feasibility considerations as well as developments in commissioned projects and policies, focusing on electrolysis via wind or nuclear power, and natural hydrogen in prime mover countries. Section 4 discusses notable take-aways, including a comparison of policy similarities and differences across the national hydrogen strategies of the prime mover countries—Germany, China, the US, and Russia. Section 5 presents concluding thoughts and key areas for future research.

2. Enabling Conditions and System Change

To shed light on the opportunities and challenges in scaling up emergent areas of hydrogen production, enabling conditions and elements of system change are first discussed. These conditions can create an environment that facilitates a viable and sustainable shift.

2.1. Enabling Conditions

Enabling conditions are critical factors that facilitate developments in areas such as the large-scale adoption of hydrogen by mitigating existing barriers or aligning/amplifying supportive drivers. In line with these conditions, energy decisions and investment may be shaped by a range of influences, including geopolitics, costs and market opportunities, decarbonization priorities, and technological breakthroughs [10,35,36].

Beginning with geopolitics—the intersection of geography and politics–such a factor can profoundly influence energy choices in terms of supply security, power dependencies, and pricing [35,37,38]. Regional conflicts, such as those in the Middle East and the war in Ukraine, highlight vulnerabilities and prospective areas for collaboration in the global energy system [25,39,40]. In particular, the conflict in Ukraine spurred the rapid diversification of energy sourcing by many European countries away from Russian natural gas and towards more secure options, including domestic renewable energy and liquified natural gas [25,35]. In such cases, geopolitical imperatives can drive the rapid adoption of alternative energy options, such as hydrogen [11,41].

Turning next to costs, those for hydrogen production vary considerably worldwide, based on the production method used, regional energy prices, and available resources and technologies (

Table 1. Comparison of estimated costs by hydrogen type.

Type of Hydrogen	Cost Range Reported (USD/kg)
Natural gas (SMR)	USD 0.70–1.60 [42]; USD 0.98–USD 2.93 [43]
Natural gas (SMR) w/CCS	USD 1.20–2.10 [37]; USD 1.64–1.69 [44]; USD 1.80–USD 4.70 [43]
Coal (gasification)	USD 1.90–2.50 [42]
Coal (gasification) w/CCS	USD 2.10–2.60 [42]
Renewables (Electrolysis)	USD 3.20–7.70 [42]; USD 4.33–6.05 [45]; ~USD 5.00–USD 7.00/kg–H2 [2022 USD] [46]; USD 5.00+ [44]; USD 4.50–USD 12 [43]
Nuclear (Electrolysis)	USD 3.07–4.33/kg [45]
Natural hydrogen	USD 0.50–1.00/kg [47,48]; developers targeting USD 0.50–2.40 [49]

).

Hydrogen that is produced from fossil fuels without carbon capture and storage is the most common and generally least expensive [27,38,43], with recent estimates, for instance, with natural gas indicating a levelized cost of production at USD 0.98–2.93 per kilogram [43]. If carbon capture and storage are included, the estimated range becomes USD 1.80–4.70 [43]. In contrast, the levelized production of hydrogen from renewables is estimated at USD 4.50–12 [43]. A related point of reference may be seen with the Hydrogen Earthshot, which was launched in the US in 2021. The project had a disruptive research and development goal that sought to reduce the cost of clean hydrogen by 80% to USD 1 per 1 kg in 1 decade [44]. The baseline production cost at the time for hydrogen from clean and renewable energy was over USD 5 per kilogram [44]. Interestingly, natural hydrogen extracted from underground formations presents an emerging area with considerable potential for cost reduction. Estimates point to a potential for USD 0.50–1.00/kg [47], with developers currently targeting USD 0.50–2.40 [49].

Across global markets, one can see significant investment, with regional variations not only in terms of funding, but also policy [8,24,27,40]. Current demand exists primarily in refining, ammonia production, and the chemical industry [8]. For new, large-scale adoption, more accessible and cost-competitive hydrogen will be necessary, as well as committed off-takers. To enable large-scale hydrogen in transport, storage, and delivery, infrastructure adaptations will also be necessary in many regions. Regarding cost competitiveness, hydrogen derived from renewable energy sources, such as wind and solar power, has been more expensive than fossil fuel-produced hydrogen [50]. Yet, costs have been declining for renewable-energy-derived hydrogen due to falling renewable energy costs and technology advances [50]. For nuclear power-produced hydrogen, production at scale beyond demonstration by commercial nuclear power plants is still in the nascent stages. In the US, three nuclear power plants are focused on demonstration: (1) Nine Mile Point Nuclear Station in New York is producing low-carbon hydrogen using low-temperature electrolysis; (2) Palo Verde Generating Station in Arizona is a research and development project focused on producing low-carbon hydrogen with high-temperature electrolysis; and (3) Davis–Besse Nuclear Power Station in Ohio is a project that, when operational, aims to evaluate various electrolysis technologies [51,52,53,54]. (See Section 3 for more specifics on commissioned projects.)

Despite the historical reliance on other energy strategies and complex markets, the recognized market potential of hydrogen has attracted investment and research from a diverse group of industry actors. Industrial gas and chemical companies with capabilities to manage gas, such as Linde of Germany and Air Products and Chemicals of the US, have been engaged in low-carbon hydrogen projects, including ones based on renewables [55,56,57]. Traditional oil and gas companies, including Shell and BP, have also invested in hydrogen projects [58,59,60,61]. These oil and gas producers could be pivotal to market expansion by utilizing their existing infrastructure, inherent technical capabilities, and capital resources. Hydrogen also opens new markets for renewables, particularly long-haul transport, heavy industry, and seasonal storage.

Renewable energy companies, including Orsted and Iberdrola, are investing in hydrogen production as well [59,62,63,64]. For these companies, hydrogen’s capacity to smooth the natural variability of many forms of renewable energy with storage and transport enables the valuable, synergistic deployment of renewables.

The nuclear sector also has opportunities in new markets, such as in the production of hydrogen for long-haul transport. Like their renewable counterparts, nuclear power plants can produce hydrogen with existing infrastructure, providing a new source of revenue and enhanced economic value for current actors. Companies such as EDF and Rosatom, which have long histories in nuclear power, are also engaging in electrolyzer manufacture and hydrogen production [65,66].

Looking beyond the energy sector, mining companies, such as Fortescue and Rio Tinto, are investing in hydrogen in ways that may synergistically enable natural hydrogen exploration or support mining operations [67,68,69]. Automotive companies, including GM, Honda, Toyota, and Hyundai, are also investing in hydrogen to prospectively compete with battery electric vehicles on functionalities, such as long ranges, heavy loads, and fast refueling, which support low-carbon priorities and fuel cell advances [70,71,72]. Globally, passenger vehicles powered by lithium-ion batteries substantially outpace hydrogen-powered fuel cell vehicles in terms of sales [73,74]. However, fuel cell vehicles powered by hydrogen have an admirable energy efficiency ratio, higher power-to-weight ratio, and substantial emission reduction potential. This comes alongside significant progress in the performance and durability of fuel cell technology [75,76]. Limited lifespan attributes and susceptibility to degradation, however, remain critical barriers to widespread commercialization, which translates to a higher total cost of ownership [75,76]. The potential of innovative start-ups could also be pivotal in breakthrough areas, like these, for hydrogen.

In addition to geopolitics and market dynamics, decarbonizing priorities are also a force multiplier for low-carbon hydrogen production, given that hydrogen allows hard-to-abate sectors to reduce their carbon footprint. Such priorities are widely evident with announcements of the G7 and G20–the seven- and twenty-largest economies in the world, with recent communiqués prioritizing decarbonization and clean-energy-related aims: G7—Apulia Leaders [77]; G20 communiqués—Rio Summit [78] and India Leaders [79], as well as other key international organizations. The World Economic Forum and World Energy Council, for example, are prioritizing net-zero agendas internationally by tracking progress, providing platforms for partnerships, and conducting research and analysis [30,80]. Notably, economic and political shifts in 2025, including announced tariffs and reciprocal responses, along with new governmental administrations, are expected to slow the momentum around decarbonization [81].

2.2. System Change

Large-scale hydrogen adoption may entail an energy system change or energy transition through expansion, new development, and/or repurposing [11]. Expansion involves the scaling up of existing infrastructure, resources, and/or capabilities, as exemplified by the construction of new hydrogen pipelines. Development introduces novel processes/technology or adapts what has been proven elsewhere. Repurposing modifies existing systems to accommodate new conditions. An example of the last type of system change occurred in Brazil during the oil crises of the 1970s and 1980s, as automotive and sugar industries repurposed their strategies and systems to produce flex-fuel vehicles and biofuel, respectively [11,82]. Today, Brazil is the undisputed leader in both the production and use of flex-fuel vehicles, with over 30 million flex-fuel cars and over 6 million motorcycles on the road [11,82]. It is also among the leading countries in biofuel production [11,82]. Across the system change approaches, those that leverage existing infrastructure or systems may minimize disruption, costs, and environmental impact. Given hydrogen’s unique requirements for storage, pipelines, and water, some degree of system change is inevitable.

Storage: Storing energy with hydrogen provides a distinct profile relative to other methods, including supercapacitors, batteries, flywheels, compressed air, and pumped storage hydro.

Focusing on hydrogen versus batteries, widely used batteries are advantageous for handling short-term (sub-hourly) power fluctuations, requiring a quick response. In contrast, hydrogen storage is more favorable for storing considerable amounts of energy for longer periods, since there is minimal energy loss over time in storage, and this approach can be scaled up with hydrogen tanks [83]. Hydrogen has notable advantages in long-duration, large-scale energy storage, fast refueling, and versatile applications, as well as its energy-to-weight ratio, enabling longer-range transportation and aviation use compared to batteries [84,85,86,87]. Hydrogen’s disadvantages include its higher production costs, especially those incurred from renewable-energy-powered electrolysis; complex storage; limited infrastructure; and safety considerations [45,84,85,86,87]. Moreover, specialized and costly coating is needed if tanks are used for hydrogen storage. In contrast, battery technology is more mature, is compact and modular, and has low infrastructure needs, with zero direct emissions in usage [84,85,86,87]. Disadvantages of batteries include longer charging times, capacity degradation, considerations tied to material dependence, supply security, and environmental effects [84,85,86,87].

Looking next at key options for hydrogen storage, these include leveraging salt caverns, depleted gas fields, and metal hydrides. Salt caverns, which are notable for their storage potential, are underground formations that have been traditionally used in the oil and gas sector. Such caverns have strong sealing capabilities and require minimal adaptations for hydrogen [88]. Yet, challenges may be encountered with the complexities of layered salt rock, hydrogen–rock interactions, thermodynamic coupling effects during high-frequency injection and extraction, permeability, geochemistry, gas migration control, geomechanical stability, and microbial activity [89,90]. While salt caverns have a history of varied use for storage, additional options may be necessary for distributed use.

Depleted oil and gas reservoirs reflect a more geologically distributed means of storing considerable quantities of hydrogen [88]. As with salt caverns, depleted gas fields can be repurposed for hydrogen storage [91], leveraging existing oil and gas infrastructure, including wells and surface facilities, for hydrogen injection and withdrawal. In addition, research is underway to explore the potential of metal hydrides for repurposing metal tanks and containers [92]. Although less mature, this last approach could provide a safe and compact means for managing hydrogen storage.

Pipelines: On a global scale, the majority of hydrogen pipeline infrastructure is owned by merchant hydrogen producers who supply bulk amounts of hydrogen to industrial end users [93]. For the long-distance delivery of large hydrogen volumes, pipelines are the most economic system due to their high capacity and economies of scale [94]. Required infrastructure may include new, dedicated pipelines or the adaptation of existing pipelines for natural gas, ammonia, and other gases or liquids.

Modifying existing pipelines for hydrogen transport may involve a number of key adaptations. These could include replacing or adapting compressors, valves, seals, meters, and related parts [94,95,96]. It could also entail substituting pipeline segments or reworking welds with hydrogen-compatible materials; improving leak detection; and implementing new controls for monitoring and regulating hydrogen flow [94,95,96]. An analysis of a German natural gas pipeline network for dedicated hydrogen found that the hydrogen transmission costs could be reduced by 20–60% in contrast to the cost of building new hydrogen pipelines [94,97]. Nonetheless, technical concerns exist, particularly regarding steel and weld embrittlement, hydrogen permeation and leaks, and the need for more cost-effective, reliable, and durable hydrogen compression technology [94,97].

Importantly, converting natural gas pipelines into structures that are capable of transporting a blend of up to 15% hydrogen may require only modest modifications [98]. There are operational projects in Portugal, Romania, and the US demonstrating blends at or up to 20% hydrogen [99]. Floene Seixal in Portugal and 20HyGrid in Romania are both operational at 20%, and HyGrid in Long Island is operational at 5–20% in the US [99]. Studies also indicate hydrogen blending and demonstration in active gas transmission networks from 0 to 100% [100].

Considered from a different vantage point, blends of up to 10 and 20% may be deemed less risky for transmission lines [100], where the suitability depends on various factors. More research is needed on partial pressure (fugacity), in addition to steel and plastic material characterizations in relation to fatigue, crack growth, and failure rates [100]. Additional materials research could also provide insight into the shorter- and longer-term functionality of previously installed valves, meters, and pressure regulators under a broader set of conditions [100].

Water: Additional considerations for large-scale hydrogen deployment include water availability and limitations. Regions facing water stress may be less suitable for hydrogen production, since commercially available electrolyzers currently require purified water [101]. Levelized cost assessments of electrolysis indicate that wind and solar photovoltaic (PV) energy have the lowest water footprints among renewables, at 43 and 330 L per megawatt-hour (L/MWh), respectively (

Table 2. Lifecycle assessment for water intensity of various energy technologies (L/MWh) [101,102,103,104].

Energy Technology	Wind	Solar PV	Natural Gas	Nuclear
Water Intensity	43	330	40–140	1500–2700

) [101,102]. In contrast, nuclear energy exhibits relatively high water requirements, estimated at 1500–2700 L/MWh, while natural gas falls within a low-to-mid range of 40–140 L/MWh [101,102,103,104].

Safety: As with any energy choice, hydrogen presents safety considerations related to its production and delivery. Hydrogen is 93% lighter than air and 88% lighter than methane (natural gas), so it rapidly diffuses in the atmosphere [94]. Its broad flammability range (hydrogen-to-air ratio) of 4–75% compared to 5–15% for natural gas indicates a lower level of air to ignite [94,105].

A hydrogen fire produces considerably less heat than a natural gas or gasoline fire, and, by extension, presents a lower risk of thermal damage or secondary fires from the point of combustion [94]. It is also nearly imperceptible in daylight, presenting a detection issue [94]. Addressing these safety considerations is necessary in adopting hydrogen systems.

2.3. Global Project Pipeline, Patenting, and Policies

As detailed earlier, hydrogen holds considerable technical potential, yet its large-scale integration introduces complexities. Despite such complexities, the momentum for hydrogen has increased, as demonstrated by hydrogen sector strategies being adopted by 60 governments [106]. Globally, advancing interest is also evident in the seven-fold increase in the project pipeline between December 2020 and May 2024, from 228 to 1572 announced projects reflecting projects of 1MW and larger [27]. This rise represents USD 680 billion in announced direct investments for projects through 2030, with giga-scale projects accounting for more than half of the investment [27].

The following section outlines key trends in low-carbon hydrogen projects, patenting, and associated policies. It serves as background for informing the subsequent focus on technology and policy developments, particularly for wind power-produced hydrogen (WHP), nuclear power-produced hydrogen (NHP), and natural hydrogen. Note: Data is drawn from the IEA project database which tracks “all projects commissioned worldwide since 2000 to produce hydrogen for energy or climate change-mitigation purposes”. This includes hydrogen that “is produced through water electrolysis with electricity generated from a low-emissions source (such as renewables, e.g., solar and wind turbines, and nuclear). Hydrogen produced from biomass or from fossil fuels with carbon capture, utilization and storage (CCUS) technology is also counted as low-emissions hydrogen. Production from fossil fuels with CCUS is included only if upstream emissions are sufficiently low, if capture–at high rates–is applied to all CO₂ streams associated with the production route, and if all CO₂ is permanently stored to prevent its release into the atmosphere. The same principle applies to low-emissions feedstocks and hydrogen-based fuels made using low-emissions hydrogen and a sustainable carbon source (of biogenic origin or directly captured from the atmosphere)” [106].

2.3.1. Low-Carbon Hydrogen Projects (Commissioned Since 2000)

Worldwide, the majority of hydrogen and liquid organic hydrogen carrier (LOHC) projects commissioned since 2000 have been established within the last 15 years (Figure 4). Of the total commissioned projects, 17% are operational, with an average capacity of 2999 Nm³ H₂/h. This contrasts with the significantly higher average capacity of 78,346 Nm³ H₂/h for all commissioned low-carbon hydrogen production projects (

Table 3. Commissioned low-carbon hydrogen projects reported worldwide since 2000 [106].

All Projects			Operational
Total Projects (#)	Normalized Capacity— New Additions (Nm3 H2/h)	Average Capacity— New Additions (Nm3 H2/h)	Total Projects (#)	Total Estimated, Normalized Capacity— New Additions (Nm3 H2/h)	Average Capacity— New Additions (Nm3 H2/h)
1697	132,952,762	78,346	287	860,670	2999

), indicating that larger-scale projects are predominantly in the development pipeline. In addition, projects reaching final investment decision (FID) or construction stages, representing a more mature phase, constitute approximately 16% of the total as of February 2024.

2.3.2. Patenting

Patenting trends provide additional insights into where upstream invention activity is occurring internationally in terms of specific technologies and geographies. Recent trends show that Europe and Japan led hydrogen-related patenting for the period of 2011–2020, with patenting growing faster in Japan [108]. Roughly half the international patent families focus on hydrogen production technologies, with the remaining being divided between end-use applications and storage, distribution, and transformation [108]. A major shift towards low-emission methods is evident, which might indicate a future boom for electrolyzers [107]. While planned capacity for 2025 lies in alkaline methods, international patent families reflect a much larger emphasis on polymer electrolyte membrane (PEM) and solid oxide electrolyzer cell (SOEC) methods [108], which may be early signals for the manufacturing capacity pipeline. With regard to more established hydrogen technologies, invention is dominated by the European chemical industry, with strong new patenting companies focusing on electrolysis and fuel cell technologies from the chemical and automotive sectors [108]. Top industry applicants include Toyota, Hyundai, Honda, Air Liquide, Linde, and Air Products, and the top non-industry applicant was CEA of France [108]. Variation in regional and technology patenting trends presents opportunities for policy intervention.

2.3.3. Policy Types and Policy Trends in Support of Hydrogen Adoption

Policy interventions serve as key levers for hydrogen development, especially when the timing of market readiness and public priorities differ [11]. To facilitate the readiness of infrastructure and markets, current policies largely focus on infrastructure deployment, market stimulation, and scientific advances [9,109,110]. Common policy instruments may be classified as supply-side; demand-side; regulatory; research, development, and demonstration; and international policies (

Table 4. Common policy instruments (authors’ compilation). Note: Policy instrument classifications can assume varied configurations. This breakdown simplifies categories for ease of application. Some policy instruments may align with more than one category.

Demand-Side	Supply-Side	Regulatory	Research, Development, and Demonstration	International
Govt. procurement	Production subsidies	Standards and certifications	Program development/demonstration funding	Trade agreements
Consumer incentives (rebates, tax credits)	Grants, loans, loan guarantees	Mandates/targets (blending, portfolio standards)	Public–private partnerships	Collaborative research
Carbon pricing	Tax exemptions	Guidelines/ streamlining of permitting, licensing, or siting		International standards
	Technical Resource Mapping	Direct public investment in, or policy support for, infrastructure

). Effective strategies often integrate these policy types, as is evident in country-specific strategies that are reviewed later. The selection, timing, and synergistic use of policy may be influenced by a range of aims, actors, and processes.

Reporting by the International Energy Agency (IEA) and International Renewable Energy Agency (IRENA) of global hydrogen-related policies shows that 374 out of 428 announced policies are currently in force, with the oldest active policy dating back to 1971 [9] (Note: The IEA and IRENA database tracks policies on renewables, energy efficiency, climate, and building efficiency, plus information on CCUS and methane abatement policies. This may not capture all policies that enable, for example, carbon-intensive hydrogen production). Of the 428 announced policies that are not in force, 30 ended and 24 are not yet in force for other reasons [9]. A detailed examination of the 374 active policies by type, sectoral focus, technology, and adopter indicates that the majority are incentive- or investment-based (131 policies); centered on the power sector (74 policies); focused on hydrogen electrolysis (72 policies); and implemented in Europe (178 policies) [9]. Policy specifics for prime mover countries are elaborated later in this article in connection with each technology focus.

Importantly, if hydrogen adoption and market growth are to occur internationally at scale, standard harmonization is needed. Notably, current metrics for defining low-carbon hydrogen reflect varied pathway and threshold focuses. For instance, a carbon intensity threshold is employed by the European Union. Derived from the European Union’s Renewable Energy Directives (RED II and the subsequent RED III), legislation requires low-carbon hydrogen to have a 70% GHG emission reduction relative to a fossil fuel comparator of 94 gCO₂e/MJ, which translates to a carbon intensity threshold of 3.38 kgCO₂eq/kgH₂ for hydrogen [111,112]. In contrast, the International Energy Agency utilizes a well-to-gate assessment for various pathways, reflecting differing technologies and energy sources [8]. The Hydrogen Council and McKinsey & Company, like the IEA, do not delineate one threshold, but provide methodologies and data for various pathways [24].

3. Technological Approaches, Projects, and Policies

Technology approaches to hydrogen production are discussed next, with an emphasis on electrolysis. Wind power-produced hydrogen and nuclear power-produced hydrogen approaches are detailed in terms of technology and key investment tradeoffs, project uptake, and policy strategies by countries that are demonstrating notable early activity. This structure is similarly used subsequently to discuss natural hydrogen.

3.1. Hydrogen Production

Currently, the most common hydrogen production approaches include thermal processes and electrolysis [113]. (To date, hydrogen production has been carried out primarily using fossil fuels, due to lower energy consumption and costs [114,115]. By one estimate, such processes emit 9–12 tons of carbon dioxide for every ton of hydrogen produced [116]). Among the technological approaches, steam methane reform (SMR) and low-temperature electrolysis are well established, whereas high-temperature steam electrolysis, thermochemical water splitting, and hybrid approaches are in early stages [115]. The SMR method involves the reaction of methane with heat and steam to produce hydrogen and carbon monoxide [83]. Water electrolysis, which is discussed below, is the primary process used to produce wind- and nuclear power-derived hydrogen. Another approach includes thermochemical water splitting, which requires a series of chemical reactions to split water into hydrogen and oxygen [117]. Completing this at higher temperatures enables better thermal efficiency, but it also fosters a corrosive environment [115,118]. Going further still, hybrid processes can split water with a closed series of thermochemical and electrochemical reactions [115].

The electrolysis process can be classified based on the temperature level that is used. Low-temperature electrolysis is carried out using electricity to split the water molecule with an electrolyzer into hydrogen and oxygen. High-temperature electrolysis uses heat and electricity to split water. Contrasting the two processes, low-temperature electrolysis is well-established and used commercially at scale, whereas high-temperature electrolysis is less established, but more efficient [83,119].

Variations in electrolysis can also be defined by the materials used for the electrolyte or chemical solution [120]. Three primary types of water electrolysis are classified based on the type of electrolyzer: (1) polymer electrolyte membrane (PEM) electrolyzers, (2) alkaline electrolyzers, and (3) solid oxide electrolyzer cells (SOECs) [120]. Among the commercially available, low-temperature methods, alkaline-based electrolysis can attain higher efficiency than PEM-based electrolysis (

Table 5. Comparison of various electrolysis processes [23].

Characteristic	Low Temp		High Temp
	Alkaline	PEM	SOEC
Operating temperature	60–80 °C	50–80 °C	650–1000 °C
Electrolysis efficiency (LHV)	63–70%	56–60%	74–81%
CAPEX (USD/kWe)	500–1400	1100–1800	2800–5600
Operating hours	60,000–90,000	30,000–90,000	10,000–30,000

Adapted from reference. LHV: lower heating value; PEM: proton exchange membrane; SOEC: solid oxide electrolyzer cell; KWe: kilowatt electric.

). Alkaline-based electrolysis carried out with potassium hydroxide is a mature technological option and widely used in the fertilizer and chlorine industries, albeit with certain limitations [119]. PEM electrolysis requires high-purity, distilled water, so electrolyzers need an integrated deionizer to allow for them to use low-grade potable water [119,121]. PEM electrolysis can generate hydrogen at high pressure (30–60 bar) compared to the alkaline-based process (1–30 bar) [119]. However, the PEM approach requires costly electrode catalysts (e.g., platinum, iridium) as well as membrane materials, and has a short lifespan [119]. Higher efficiency levels may be attained for less commercially established methods, such as SOECs (Table 5). In 2023, alkaline technology represented approximately 66% of the installed electrolyzer capacity, followed by PEM-based approaches at 22% [8].

Regarding hydrogen production and utilization, a significant barrier to broader adoption is inherent energy inefficiency. Multiple energy conversion steps that are distinct to hydrogen production and utilization entail cumulative energy losses, making a hydrogen-based strategy less energy-efficient than established strategies, such as direct electricity use and fossil fuel combustion. Despite these challenges, the potential for zero emissions at the point of end use, especially with hydrogen produced from wind or nuclear power, alongside advantageous energy density by weight, makes these strategies attractive for applications where low-carbon priorities are critical and efficiency may be secondary. In addition, where technological advancements may improve efficiency, the strategy becomes even more compelling.

Overall, electrolysis capacity and the manufacturing of electrolyzers have been increasing worldwide. At the end of 2023, electrolysis capacity reached 1.4 GW of installed capacity, nearly twice that at the end of 2022 [8]. Concurrently, electrolyzer manufacturing capacity increased by a factor of two to 25 GW per year [8]. In 2024, estimates for accumulated manufacturing capacity showed China as ranking first, followed by the US and Europe, at roughly 25 GW per year, 8 GW per year, and 4 GW per year, respectively [8].

3.2. Wind Power-Based Hydrogen Production or Wind-to-Hydrogen Production (WHP)

Wind power-based hydrogen production is evolving into a developing industry, attracting increasing investment and planned production. WHP offers cost-effectiveness in regions with strong wind resources, efficiently stores and utilizes surplus energy, and enables decentralized production, thereby reducing transport costs. The rapid deployment and scalability of WHP, coupled with electrolyzer and offshore wind advancements, further enhance its potential. The natural synergy between wind’s intermittency and hydrogen storage makes WHP a viable solution for enhancing the flexibility of renewable energy systems [7,122].

Technical constraints also exist with WHP. Regular cycling and variable energy inputs may degrade electrolyzer lifespans or require more frequent maintenance [123]. The intermittent power supply of renewable generation, such as wind power, may impact the efficiency and durability of low-temperature electrolyzer systems such as PEM and alkaline technology [123,124]. Such electrolyzer technology is designed for constant load conditions. Capacity factors (average power output divided by its maximum power capability) can vary for wind turbines. In 2023, the global weighted average capacity factor for wind power was approximately 36% [125]. Research highlights how dynamic operation introduces stress that may amplify degradation rates to be up to four times that of steady-state operations [124]. Yet, research also indicates that integrating rest periods into operation would help reduce irreversible electrolyzer decay [124]. Given this mixed outlook, there is a need for more research in this area. Here, the stability and strength of offshore wind relative to its onshore counterpart may address the issue.

Examining the WHP project pipeline, international efforts have gained momentum in recent years, as countries and companies recognize the potential of WHP to decarbonize heavy industries and transport [23] (Figure 5). Noticeable growth has occurred in commissioned WHP projects worldwide since 2018 (Figure 5).

Assessing a broader range of commissioned WHP projects since 2000, 209 are reported, with the first coming online in 2007 for demonstration [106] (Figure 6). Projects that became operational reflect 13% of the total commissioned WHP projects (

Table 6. All commissioned wind and wind projects that became operational [106].

All Projects			Operational
Total Projects (#)	Normalized Capacity—New Additions (Nm3 H2/h)	Average Capacity— New Additions (Nm3 H2/h)	Total Projects (#)	Total Estimated, Normalized Capacity—New Additions (Nm3 H2/h)	% of All Commissioned Wind Projects	Average Capacity— New Additions (Nm3 H2/h)
209	17,435,647	83,424	27	19,663	13	728

). Like the fuller trends for low-carbon hydrogen production (Table 3), the average capacity for new additions of operational WHP projects is substantially less than the average for the WHP total, suggesting that larger-scale projects are under developed thus far in the pipelines.

Analyzing the global WHP profiles more fully, projects can be viewed by country rank, large project characteristics, and the type of hydrogen production [106]. At the country level, China has the most WHP capacity that is operational at 56%, followed by Germany and Denmark at 33% and 4%, respectively (Figure 7). The largest two operational projects are onshore-wind, alkaline-based facilities: one in China (Shell China—Zhangjiakou Transportation Investment, phase 1 at ~4348 Nm³ H₂/h, online in 2022) and one in Germany (H2 Pilotanlage Lingen, phase 1 at ~2174 Nm³ H₂/h, online in 2024). Among all operational WHP projects, alkaline-based projects reflect 68% of the global total, with PEM and other electrolysis processes representing 17% and 15%, respectively.

Looking next at the most recently operational projects in 2024, offshore wind projects were brought online in Germany. These included the Pilotanlage Lingen, phase 1, noted above as ranking second largest globally, and its counterpart, H2 Pilotanlage Lingen, phase 2, which is PEM-based (~769 Nm³ H₂/h) [106].

• Policies

Focusing on the policies that explicitly reference both hydrogen and wind, 21 are reported as being in force globally [9]. These reflect alignment among wind and hydrogen policies, but may not translate directly as a WPH policy. Consistent with global hydrogen policy trends, the majority of these policies center on the power sector (10 policies) and are incentives or investments (also 10 policies) [9].

Recognizing that China and Germany are the countries with the largest WHP projects in terms of capacity as well as the countries with the largest share of operational WHP projects worldwide, their recently released national hydrogen plans and related policies are summarized next.

China: China rolled out a robust hydrogen strategy over the past five years that catalyzes and supports the development of a domestic market [9,110,126,127]. The strategy is based on the National Hydrogen Plan that was released in March 2022 [9,110,126,127].

Key policy priorities encompass the formal recognition of hydrogen as being vital for China’s future energy system and its low-carbon transition; the establishment of green hydrogen production targets (Box 1) alongside the promotion of policies that maximize renewable energy use, while minimizing waste; and the setting of goals for hydrogen-fueled vehicle deployment with subsidies to support their adoption. In addition, select priorities also include developing standards and guidelines for hydrogen production, storage, transport, and use, as well as promoting the development of comprehensive hydrogen ecosystems; focusing on increasing the use of low-carbon hydrogen in the industrial sector; and promoting the use of renewable energy to produce hydrogen as well as encouraging hydrogen storage [9,110,126,127].

Box 1. Hydrogen color scheme.

Color schemes for hydrogen may vary. The following details examples from a sample spectrum [128]. Green hydrogen often refers to hydrogen produced via the electrolysis of water with renewable energy. Blue hydrogen is produced primarily from natural gas through steam methane reforming, with carbon capture and storage (CCS). Turquoise hydrogen is produced from methane pyrolysis with natural gas, in which methane is split into hydrogen and solid carbon. Orange hydrogen is produced by using plastic waste as a feedstock. Pink hydrogen uses water electrolysis powered by nuclear generation, and white hydrogen, also known as natural hydrogen, is naturally generated within the Earth’s crust through interactions between water molecules and iron-rich minerals at high temperatures and pressures [128]. Another version of orange hydrogen includes that which is produced by injecting carbon-enriched solution into reactive formation, essentially accelerating the formation of natural hydrogen [129].

Looking beyond policy instruments to policy milestones highlights how China’s commitment to hydrogen has taken shape in recent years. In March 2022, the National Hydrogen Plan was released, establishing production targets for green hydrogen and the deployment of hydrogen-fueled vehicles to stimulate the domestic market [110,126]. In August 2023, China issued its first national-level guidelines for hydrogen standards with production, storage, transport, and use, creating a regulatory basis for market growth [130]. Subsequently, in November 2024, twenty-two new hydrogen policies were announced across twenty-four provinces and cities, advancing hydrogen development through legal frameworks, financial incentives, and industrial strategies [110,127]. Following that, in December 2024, a plan was announced to boost low-carbon hydrogen use in the industrial sector, expanding market applications [110].

Germany: In recent years, Germany has implemented a robust and highly coordinated hydrogen strategy that systematically drives and supports the development of domestic and export markets as well as international partnerships, with explicit financing and governance [9,110,131]. Germany’s approach centers on the National Hydrogen Strategy, which was adopted in June 2020 and updated in July 2023, along with associated policies [9,110,131].

Key policy priorities for Germany’s strategy include establishing Germany as a leader in both domestic and international hydrogen markets; the allocation of significant funding to support hydrogen projects, infrastructure development, and international partnerships; and the creation of a hydrogen core grid by repurposing existing infrastructure, and accelerating the expansion of hydrogen pipelines and import terminals [9,110,131]. In addition, policies promote electrolyzers, research initiatives such as ‘Hydrogen Technologies 2030,’ and the development of hydrogen engines. They entail active engagement in international collaborations to secure the hydrogen supply and promote German hydrogen technologies [9,110,131]. They also include establishing funding guidelines, streamlining planning processes, and addressing pricing components in the energy sector to create a favorable market environment [9,110,131]. Further, policies support hydrogen adoption in key industries such as transportation, steelmaking, and chemicals; and the establishment of the National Hydrogen Council to coordinate hydrogen policy [9,110,131]. Notably, policies prioritize green hydrogen, yet the strategy was expanded to include blue, turquoise, and orange hydrogen (see Box 1) to facilitate a market transition [9,110,131].

Looking once more beyond policy instruments to policy milestones highlights how Germany’s commitment to hydrogen has evolved in recent years. In 2019, twenty-five regions received awards from the National Innovation Program Hydrogen and Fuel Cell Technology to develop hydrogen projects [110]. This was followed in June 2020 by the adoption of the National Hydrogen Strategy, the investment of EUR 9 billion, and the launch of the National Hydrogen Council [110,132]. In May 2021, EUR eight billion in federal and state funding was announced to support sixty-two large-scale hydrogen projects [110,133]. Subsequently, in October 2021, a funding guideline was released to spur the scaling up of an international market for green hydrogen [110]. The National Hydrogen Strategy was revised in July 2023, diversifying hydrogen types and setting more ambitious targets for infrastructure and electrolyzer capacity [131,134]. Following that, in February 2024, the European Commission (EC) approved twenty-four German projects under the Important Project of Common European Interest (IPCEI) Hydrogen program, with EUR 4.6 billion in funding, and, more recently in May 2024, the German Cabinet approved a law to accelerate hydrogen production and infrastructure development [110,135].

Importantly, as a member state in the European Union (EU), Germany’s developments are influenced by EU policies. Such policies include a focus on climate neutrality with a cohesive regulatory and market framework, the Emission Trading System, direct mandates, and the European Hydrogen Bank [136]. In addition, a continued EU focus on the regulatory and market environments, as well as infrastructure development for hydrogen, means these will be crucial areas to watch.

3.3. Nuclear Power-Based Hydrogen Production or Nuclear-to-Hydrogen Production (NHP)

Similarly to WHP, nuclear power-based hydrogen production offers a primary means to deliver low- or zero-carbon hydrogen. The attractiveness of this approach for hydrogen production is that any excess heat or electricity from nuclear power plants—which are intended and modeled to run at full capacity—can be channeled into hydrogen production [137]. This may create additional benefits at a limited cost.

Among NHP processes, the three primary methods include using electricity from nuclear power for electrolysis; employing process heat for thermochemical cycles; and utilizing a hybrid system that integrates heat and electricity in, for example, high-temperature steam electrolysis [83,138]. Currently, methods using established technology for NHP include those for low-temperature electrolysis with alkaline or PEM processes in conventional nuclear power reactors (Table 7). These methods reflect a hydrogen production process efficiency of 60% for alkaline- and PEM-based processes (Table 7), so they remain costly. It is worth noting that there is emergent potential with advanced high-temperature reactors that may enhance hydrogen production efficiency with high-temperature steam electrolysis and thermochemical processes that can be carried out without electricity [15,139]. Additionally, steam generated by current commercial reactors could also be employed for high-temperature steam electrolysis [139,140]. Given that electrolysis-based hydrogen production is a primary focus of this article in terms of wind and nuclear energy, other modes are noted when relevant.

Table 7. Comparison of nuclear hybrid energy systems for hydrogen production [119,137,141].

	Alkaline	PEM	SOEC	SMR
Tech readiness 1	9	6–8	5	9
Temperature (°C)	60	60	800	870
H2 Yield Efficiency (HHV, %)	29.8	27	35.8	79.4
Heat (MJ/kg H2)	26.2	26.2	29.7	0
Water (kg/kg H2)	11.5	11.5	83.3	10.3
CO2 out (kg/kg H2)	0	0	0	4.7
Cost (USD2019)/kg H2 produced	5.92	3.56–5.46	2.24–3.73	1.54–2.30

Note: Efficiency assumes 40% heat to electricity conversion. PEM: proton exchange membrane. SOEC: solid oxide electrolyzer cell. SMR: steam methane reforming. ¹ The Technology Readiness Level scale is a nine-point spectrum for quantitatively assessing the maturity of a given technology. The above table is predicated on earlier work tied to the U.S. National Aeronautics and Space Administration framework that spans levels 1–3 (concept definition through to proof of concept), 4–6 (scale testing through to demonstration at the pilot scale), and 7–9 (prototype and subsystem demonstration through to commercial deployment) [141,142].

Table 7. Comparison of nuclear hybrid energy systems for hydrogen production [119,137,141].

	Alkaline	PEM	SOEC	SMR
Tech readiness 1	9	6–8	5	9
Temperature (°C)	60	60	800	870
H2 Yield Efficiency (HHV, %)	29.8	27	35.8	79.4
Heat (MJ/kg H2)	26.2	26.2	29.7	0
Water (kg/kg H2)	11.5	11.5	83.3	10.3
CO2 out (kg/kg H2)	0	0	0	4.7
Cost (USD2019)/kg H2 produced	5.92	3.56–5.46	2.24–3.73	1.54–2.30

Note: Efficiency assumes 40% heat to electricity conversion. PEM: proton exchange membrane. SOEC: solid oxide electrolyzer cell. SMR: steam methane reforming. ¹ The Technology Readiness Level scale is a nine-point spectrum for quantitatively assessing the maturity of a given technology. The above table is predicated on earlier work tied to the U.S. National Aeronautics and Space Administration framework that spans levels 1–3 (concept definition through to proof of concept), 4–6 (scale testing through to demonstration at the pilot scale), and 7–9 (prototype and subsystem demonstration through to commercial deployment) [141,142].

When employing hybrid NHP systems (with a Rankine cycle, a thermodynamic cycle used is in steam-based power plants to convert heat into mechanical work), high-temperature SOEC electrolysis can then be carried out, reducing the amount of electrical consumption per unit of hydrogen production [143]. Generation III reactors can cover lower temperatures, whereas advanced Generation IV reactors (e.g., a very-high-temperature reactor, gas-cooled fast reactor, lead-cooled fast reactor, and molten salt reactor) are more appropriate for high-temperature processes due to their superior thermodynamic efficiency and outlet temperature [83,144]. A higher reactor outlet temperature increases the efficiency of both the electrical generation and production of hydrogen [83]. (Note: High-temperature and low-temperature heat recovery reduces the level of heat required.) Thermal chemical water splitting cycles, such as that performed with sulfur–iodine, employ high heat (500–2000 °C) to drive reactions which decompose water [145].)

Utilizing nuclear generation for high-temperature electrolysis with the SOEC method represents a pivotal area for synergy. Because it uses not only the electricity from high-temperature reactors, but also the heat, the SOEC process has a much greater efficiency than other electrolysis methods, with a lower energy penalty. It also entails considerably higher water use (Table 7). Leveraging a high-temperature electrolysis method also enhances nuclear energy’s flexibility in hybrid systems [83], thereby providing an alternative revenue stream which can be crucial in power markets where nuclear may be less competitive than natural gas or renewables. A key tradeoff in using materials to increase the temperature resistivity is a considerable increase in the cost [83].

An area to watch is the coupling of SOECs with nuclear thermochemical cycles. Although this area is less mature than high-temperature steam electrolysis, it may offer a longer-term strategy for hydrogen production that leverages heat over electricity. To achieve this, developments will be needed in materials science, reactor technology, and systems integration, as high temperatures and corrosion can degrade materials. Scaling up will require advances in engineering and manufacturing as well as economic competitiveness.

Examining the technical and economic similarities and differences for NHP and WHP with electrolysis offers insight into their complexities and tradeoffs. Nuclear power offers a stable baseload energy source for consistent and potentially large-scale hydrogen production which can compare with offshore wind-produced hydrogen. In levelized cost terms, which compare energy projects on an ‘apples-to-apples’ basis, the costs of new nuclear plants are considerably higher than wind plants [45]. Higher upfront costs and lengthier development times associated with constructing new nuclear facilities, particularly compared to onshore wind, could be mitigated by utilizing existing nuclear power plants [45,52,146]. However, as with all nuclear reactors, concerns regarding nuclear waste disposal and safety may require public scrutiny [147].

Regarding the NHP project pipeline since 2000, international efforts are still nascent, with sixteen commissioned projects reported—the majority of which are in the concept phase (see

Table 8. All nuclear and nuclear projects commissioned since 2000 that became operational [106].

All Projects			Operational
Total Projects (#)	Normalized Capacity—New Additions (Nm3 H2/h)	Average Capacity— New Additions (Nm3 H2/h)	Total Projects (#)	Total Estimated, Normalized Capacity— New Additions (Nm3 H2/h)	% of All Commissioned Wind Projects	Average Capacity—New Additions (Nm3 H2/h)
16	317,524	19,845	2	385	13	192

) [106]. Two projects that became operational since 2000 represent 13% of the total commissioned NHP projects (Table 8). Like trends in low-carbon hydrogen generally and WHP projects, the average capacity of operational NHP additions is substantially lower than the average capacity for all commissioned NHP projects, indicating that larger-scale developments are still in the pipeline.

Examining the NHP profiles more fully, projects are considered by country rank, large project characteristics, and the type of hydrogen production [106]. At the country level, the US and Russia are tied as having the most operational capacity of NHP. These projects are Constellation’s Nine Mile Point Nuclear Plant (192 Nm³ H₂/h) and the Kola Nuclear Power Plant demonstration (192 Nm³ H₂/h). Both are PEM-based and were brought online in 2023 and 2022, respectively [106].

• Policies

In line with the more nascent nature of NHP adoption, IEA and IRENA reporting reflects a limited number of policies globally—five total in force—which include nuclear and hydrogen: two in Japan, two in the United Kingdom, and one in the US [9]. Many of these policies center on governmental spending for low-carbon electricity, as well as incentives/investment, with the power sector as the area of emphasis. Focusing on the US and Russia, where the largest NHP projects are located, the following details their national hydrogen strategies and recent policy developments.

United States: The United States has implemented a rapidly evolving hydrogen strategy, which has accelerated particularly since 2021, focusing on the research, development, demonstration, and deployment of clean hydrogen technologies [9,110,148,149,150,151,152,153,154,155,156]. The U.S. National Clean Hydrogen Strategy and Roadmap, released by the Department of Energy in 2023, served as the centerpiece [153]. As of 2025, refined priorities and/or rollbacks are now critical to watch.

Key policy priorities in recent years encompassed the National Strategy and Roadmap framework, which emphasized large-scale clean hydrogen production and utilization with cost reduction, strategic use, and regional hub deployment [110,153]. Through competitive agreements, regional clean hydrogen hubs were established to strengthen hydrogen production and consumption, while driving clean manufacturing and job creation, with federal guidance that has been redefining at least part of the economic and technology playing field [110,151]. Another priority was significant funding support for the research, development, and deployment of clean hydrogen technologies [152,157]. The Inflation Reduction Act introduced key tax credits and incentives, including the 45V Clean Hydrogen Production Tax Credit, to stimulate market growth [110,148,149,158]. Complementing these efforts, the Department of Energy (DOE) funded research to advance hydrogen technologies, lower production costs, and improve infrastructure [154]. Another critical focus was the building out of hydrogen infrastructure, such as production facilities, pipelines, and storage solutions. Initiatives such as H2 Twin Cities 2023 promoted collaboration and knowledge-sharing among cities and communities [110]. Bipartisan legislation efforts to advance hydrogen development for the aviation sector were also recently advanced. [159]. In addition, significant funding has been directed towards increasing the production of electrolyzers and improving manufacturing capabilities, as well as reducing greenhouse gas (GHG) emissions [159]. However, the priorities of the new administration and Congress in 2025 are shifting the emphasis of such policies, including some or all of those relating to the hydrogen strategy [160].

Looking beyond policy instruments to policy milestones highlights the evolution of how the US commitment to hydrogen has taken shape. In 2019, the DOE released multiple funding announcements to promote new markets and research, development, and demonstration (RD&D), targeting storage, infrastructure, and heavy-duty fueling [161,162,163]. This included the establishment of the previously mentioned H2@Scale program, focusing on advancing hydrogen technologies [162,163]. Following that, in 2021, the Hydrogen Energy Earthshot was launched, aiming to drive down the cost of clean hydrogen [110,164]. The Infrastructure Investment and Jobs Act was passed in 2021, and the already-noted Inflation Reduction Act was passed in 2022, allocating billions for hydrogen development [158,165]. Then, in June 2023, the DOE released the centerpiece instrument—the National Clean Hydrogen Strategy and Roadmap—outlining long-term goals and strategic priorities [110,153]. Later in October 2023, the administration announced USD 7 billion in funding for seven regional clean hydrogen hubs [110]. With phased funding, enabling oversight and risk mitigation, as well as key guidance defining technical and operational aspects, the program has evolved from one of notable funding to a specialized and structured program. Recently, in January 2025, the Treasury and Internal Revenue Service released final rules for the 45V Clean Hydrogen Production Tax Credit, which is key for financing and defining requirements, including for lifecycle GHG emissions, to qualify for the tax credit [149]. In tandem with the tax credit rule change, the DOE updated its Hydrogen Program Plan in December 2024. This plan outlined collaborative efforts to implement the National Clean Hydrogen Strategy and Roadmap, with the regional clean hydrogen hubs playing a key role alongside coordinated research, development, and deployment, while also highlighting goals such as the Hydrogen Shot [155]. In 2025, the new federal administration and Congress have accelerated deadlines for project development with the 45V tax credit, and are sustaining support principally for fossil fuel-based hydrogen [160,166].

Russia: Russia has put forward a comprehensive hydrogen development strategy over the past four years, aiming to establish itself as a major global exporter [9,110]. Its hydrogen development strategy is anchored primarily in the June 2020 release of the Energy Strategy until 2035 [9,110], and its creation of hydrogen hubs focused on European and Asia markets, as well as an Arctic cluster. However, with international sanctions imposed on Russia in connection with the war on Ukraine and changes in the geopolitical environment, Russia has been forced to adapt its hydrogen strategy.

Prior to the 2022 invasion: Key policy priorities encompassed establishing Russia as a major global hydrogen exporter, with a phased approach to hydrogen development, increasing export targets and technological advancements over time [9,110]. In addition, investments were planned for hydrogen production, transportation, and consumption, with a focus on utilizing Russia’s natural gas resources and developing low-carbon technologies; as well as the research and development of hydrogen technologies, including electrolysis, methane pyrolysis, and fuel cells [110]. Priorities also included pilot projects for carbon-free hydrogen production, methane–hydrogen fuel gas turbines, and hydrogen-run railway transport (action plan); the creation of regional hydrogen clusters for production and export; and international partnerships to facilitate hydrogen exports and technology transfer [110]. Being initially export-focused, the strategy included efforts to stimulate domestic demand for hydrogen fuel cells and other applications; the release of the Russian Atlas of Hydrogen and Ammonia Production Projects, which aimed to attract investors; and the diversification of production methods from natural gas, nuclear, and tidal power [110].

Policy milestones highlight the timing of developments. As noted above, the Energy Strategy until 2035 was released in June 2020, outlining Russia’s ambition to become a global hydrogen export leader [110]. In October 2020, an action plan for hydrogen development until 2024 was approved, focusing on pilot projects and technology development [110]. The following year, in August 2021, the Concept for the Development of Hydrogen Energy was approved, establishing a phased approach with increasing export targets [110]. It also outlined the establishment of three hydrogen hubs: a northwestern one to focus on Europe, an eastern one to focus on Asia, and an Arctic cluster as the centerpiece [167]. The plan was to harness Russia’s incumbent infrastructure and capabilities for fossil fuel and nuclear to generate hydrogen that could be supplied to export markets via the Northern Sea Route.

The Russian President then directed an examination of tidal-powered hydrogen production in October 2021, and the Ministry of Industry and Trade released the Russian Atlas of Hydrogen and Ammonia Production Projects [167]. The state-owned enterprises Gazprom, Rosatom, and Novatek were charged with taking the lead, respectively, on using gas fields, nuclear capabilities, and producing hydrogen and ammonia alongside liquified natural gas projects [168,169].

Post-invasion: The early strategy, which was centered on export and an Arctic cluster, was forced to change with the advent of shifting geopolitical and market conditions tied to the war with Ukraine. With the loss of the European market, sanctions, and financial isolation, hydrogen efforts appear to have slowed. Nonetheless, efforts continue with China. In May 2024, Russia and China released a joint statement to deepen cooperation on hydrogen [169]. Notably, information currently remains limited.

3.4. Hydrogen: Natural-Occurring Resources

Natural hydrogen has emerged as a potential game-changer in the global energy field, offering a theoretically available, low-emission alternative to conventional hydrogen production methods. Unlike wind power- or nuclear power-produced hydrogen (or the significant amount of hydrogen that is produced today from fossil fuels), natural hydrogen offers the possibility of a low-emission and cost-effective alternative without the need for energy-intensive production processes or much refining. Recent discoveries suggest that vast underground reservoirs of hydrogen may exist, with some estimates indicating enough supply to meet global energy demands for centuries [170]. Documented studies also detail hydrogen associated with ophiolites (ancient fragments of oceanic crust and upper mantle that have been tectonically emplaced onto continental margins) and countries, including Turkey, Philippines, Oman, New Caledonia, Brazil, the US, and Russia [171,172,173,174,175,176,177].

Natural hydrogen is primarily generated through geochemical processes such as serpentinization [172]. This process involves the reaction of water with iron-rich minerals in ultramafic rocks, leading to the production of hydrogen gas. Additionally, radiolysis, where natural radioactive decay splits water molecules, contributes to subterranean hydrogen formation. Recent studies estimate that there may be 6.2–10 trillion tons of hydrogen buried underground [178,179], with significant accumulations identified in regions such as West Africa and Eastern Europe [178]. To locate and extract this hydrogen, geologists employ techniques such as seismic surveys to map potential reservoirs, followed by drilling to access the gas.

In May 2025, a hydrogen and helium exploration company, HyTerra, made an important breakthrough, finding 96.1%-pure hydrogen in its Sue Duroche-3 well as part of the Kansas Nemaha Ridge project (US). They leveraged techniques such as subsurface imaging with its partner, Avant Energy, and hydrogen isotopic analysis to discern deep-earth hydrogen from surface-level hydrogen [180]. An estimate of costs for pure hydrogen, such as that found in the HyTerra project, indicates that extraction could be below USD 1 per kg [179]. Because natural hydrogen development is in the early stages, comparative cost studies are limited. However, a major driver of natural hydrogen exploration is the potential cost-effectiveness of harvesting natural hydrogen compared to that of other hydrogen production methods (Table 1).

Here, leveraging the overlap in existing infrastructure, transferable processes, and the expertise of the shale gas industry presents promising synergistic value. The co-development of such resources with shared infrastructure, geology, and co-location of sites could offer considerable opportunity. Furthermore, repurposing existing capabilities and assets could considerably reduce timelines and costs. In particular, geological formations that are depleted shale gas reservoirs could be attractive for large-scale hydrogen storage.

Uncertainty remains, however, including regarding the depths at which hydrogen may be found, its concentration within geological formations, and the economic feasibility of extraction [181,182]. Challenges also remain in identifying commercially viable deposits, scaling extraction technologies, and integrating natural hydrogen into existing energy markets. Yet, techniques such as those employed in the HyTerra project demonstrate real potential. If and when resources are to be tapped for commercial use, hydrogen’s high diffusivity and chemical/biological reactivity will require adapted solutions for operational integrity and wellbore safety [183]. Questions also exist in terms of permitting rules and ownership, resource classification, environmental regulation, and the risk that unleashing hydrogen into the atmosphere may amplify greenhouse gas warming [179]. If this last concern proves to be a real consideration, this risk should apply to produced hydrogen as well.

Currently, the world’s only operational, natural hydrogen project is located in the village of Bourakébougou, Mali. Since 2012, hydrogen from the project’s well has been captured at a rate of 50,000 cubic feet per day, fueling a small turbine that provides power to the village of 1500 [179,184]. Prospecting is occurring in other regions of the world, including Australia, France (Box 2), Spain, Morocco, Brazil, and the United States [179].

Box 2. Natural hydrogen in France.

Recently, France made two major discoveries of natural hydrogen resources—one in in the Lorraine region in May 2023 and another in the Moselle area in March 2025 [185]. Estimates for the Lorraine region indicate 46 million tons of natural hydrogen [185]. To put this amount into context, it would be one of the largest known reserves in Europe and represent nearly half the world’s current hydrogen production [185]. The March 2025 announcement identified an additional deposit of equal scale nearby in the Moselle area [185]. If fully tapped, these could meet global hydrogen demand for several years [185].

• Policies

Policy support for natural hydrogen sourcing is a nascent and developing area. In fact, for Mali, the one country with an operational project that supplies natural hydrogen for power, no policies are evident [106]. However, policies that broadly support low-carbon fuels, including hydrogen demand, infrastructure, and end-use technology, might apply to natural hydrogen. As natural hydrogen emerges as a fuel option, policies may require adaptations. For example, will regulations for the exploration and extraction of natural gas apply to natural hydrogen, including environmental impact assessments, permitting processes, and safety standards?

In terms of tax incentives and subsidies, such as those in the U.S. Inflation Reduction Act, provisions for clean hydrogen may require clarification for application with natural hydrogen. Moreover, safety standards will be needed for handling, transportation, and storage [186], including flammability risk and other safety considerations. Research and development, as well as exploration-based policies (resource mapping), should be considered for potential government support and/or oversight.

4. Discussion

With global hydrogen demand tripling since 1975, there appears to be growing recognition of its potential. The current market reflects regionally varied investment and policy development, attracting a diverse range of interested actors. This convergence presents a crucial window to advance hydrogen in terms of scientific knowledge, technological commercialization, and adoption scalability. Supporting this momentum, research and related scholarly writing on hydrogen have grown exponentially. Similarly, international summits and organizations are increasingly emphasizing hydrogen’s role in a low-carbon energy future.

As operational production capacity for hydrogen has scaled significantly since 2000, wind-powered hydrogen projects are currently more prevalent than nuclear-powered ones, which remain nascent but promising. Germany and China lead in wind-powered hydrogen, while the US and Russia are at the forefront of nuclear-powered hydrogen adoption, indicating diverse regional approaches to hydrogen development.

Looking across wind-, nuclear-, and natural-hydrogen-based approaches to scaling up hydrogen production in the energy sector, each approach offers disruptive potential, albeit with distinct characteristics. WHP optimizes wind energy by managing variability and storing surplus, which is particularly beneficial for distributed, remote, and offshore applications. NHP enables electrolysis, as well as alternative approaches beyond the scope of this review to enhance nuclear energy’s market competitiveness by also utilizing surplus power. Natural hydrogen, if proven abundant, accessible, and cost-effective, could revolutionize the industry. However, all three options require more convergent alignment of enabling conditions, including significant infrastructure development to connect resources with end users.

Alongside technological advances, costs are likely to continue to be a major determinant of adoption readiness and are recognized in key RD&D and deployment policies. Technology advances will be needed to reduce costs across the hydrogen value chain [108]. Moreover, the global economic pressures that were evident in April–July 2025, including new levels of protectionism and potential for a global recession [187,188], provide a mixed outlook for hydrogen development. A global recession would likely dampen investment or delay projects. Yet, heightened protectionism will also likely intensify energy security efforts in domestic markets. For countries/regions such as China, the EU, and the US, which have notable installed electrolysis capacity and manufacturing capacity for electrolyzers, WPH or NPH production efforts could very well intensify, assuming the domestic policy regimes are neutral towards or supportive of the power production technologies.

Turning to energy transitions, opportunities exist for hydrogen in the scaling up of clean energy, with grid flexibility needs, and in terms of jobs. For clean energy, such as renewables, hydrogen provides a critical means by which to smooth intermittent and variable fluctuation in power. For both nuclear and wind power, hydrogen production allows for better utilization of surplus generation. With respect to grid flexibility priorities, attainment can be strengthened with long-duration energy storage from hydrogen. In terms of jobs, the hydrogen sector can leverage a mix of capabilities, some of which are transferable, for example, from the oil and gas sector, while other jobs are more specialized. In areas such as the development of storage facilities, transport technology, and refueling stations, competencies will be needed in pipeline technicians and construction work as well as chemical, electrical, and mechanical engineering. For manufacturing/production, capabilities will be required for assembly, quality control, and welding, alongside plant operators and production engineers. As markets expand, knowledge in business development, analysis, and regulation will also be needed. More broadly, material scientists and electrochemists can play a vital role. Fuel cell and electrolyzer technology, as well as hydrogen safety, will also require specialized competencies. A recent McKinsey report estimated that the hydrogen industry in the US, for example, could generate approximately USD 750 billion in annual revenue and support 3.4 million jobs by 2050 [189]. Here, some regions and communities may welcome the opportunities to leverage local resources and capabilities more fully (social acceptance and readiness), whereas others may have concerns about technology change.

Looking more directly at the approaches of the four prime movers, or leading countries, in the adoption of wind and nuclear power hydrogen production, there are notable similarities and differences for China, Germany, the US and Russia.

In terms of similarities, all four nations have implemented significant national hydrogen strategies that encompass a wide range of market development (demand- and supply-side), plus research and development-based policies prioritizing lower-carbon hydrogen production. This may change, particularly in terms of the low-carbon priority for countries such as the US, where considerable policy shifts are moving away from decarbonization. With regard to infrastructure development, all four countries are investing in, or planning for, significant hydrogen infrastructure, including production facilities, pipelines, and storage. In their research and development, all of the countries emphasize the need for continued efforts to advance hydrogen technologies.

Shifting to key policy differences, Germany and Russia have both articulated a desire to be a global hydrogen leader, although trade and technology strengths will impact outcomes. Until the war with Ukraine, Russia appeared to be primarily export-focused, whereas Germany balances domestic market development with aims for global technology leadership and export. Looking more broadly, China is currently the global leader in terms of production, with policies centered on building a robust domestic hydrogen market. The US has focused on creating a domestic market, with some international collaboration; however, the political and policy headwinds are changing this direction of development. In terms of hydrogen production, the US, China, and Germany were ‘initially’ heavily focused on policy for low-carbon hydrogen produced from renewable sources. However, Germany and the US modified their strategies through updates, cost-sharing by hubs, or tax credit details to include other options such as nuclear, fossil fuel, and/or hydrogen from waste storage [131,158,160,190,191,192]. Germany continues to prioritize green hydrogen with its funding; yet, it has widened the types of hydrogen that are broadly accepted to ensure rapid development of the hydrogen market and meet the expected demand [131]. For the US, new priorities are redefining the playing field, as the new administration and a majority of Congress are strong proponents of fossil fuel production and use [81,160]. Russia emphasizes utilizing its natural gas resources but is also exploring nuclear and tidal power [110].

Looking next at policy implementation, there is notable variation across the four countries of focus. China has rapidly deployed policies at national, regional, and local levels, with a strong concentration on industrial integration. Germany has implemented a highly coordinated, national-level approach with significant financial commitment and EU collaboration. The US policy implementation is characterized by legislative acts, funding initiatives, and a strategic roadmap, with considerable uncertainty tied to future political support. Russia presented a phased, long-term strategy with a strong emphasis on government-led initiatives. However, its status post-invasion of Ukraine is now less clear.

Among the four countries studied here, additional distinctions are evident when considering political considerations and collaboration. The US, for example, could continue to see considerable policy reversals. Regarding international collaboration, Germany has a strong, evident priority in its policies. The US and Russia both mention international collaboration, but to a lesser extent, and China appears to be focused on domestic development. In short, all four countries articulate hydrogen as a key element of their energy futures. Their approaches differ significantly in terms of market focus, production sources, and implementation styles, reflecting their unique national circumstances and priorities.

Regarding the limitations of this work, this article is primarily a review. As such, it synthesizes existing research and data, incorporating translated materials, where applicable. Tracking international policies and projects, as exemplified by the IEA, IRENA, and Baker McKenzie, is recognized as a major undertaking that requires people and resources. Maintaining this consistently tests access to project information and translation. The extremely rapidly changing nature of this subject is also a consideration. Despite these inherent limitations, this work serves a purpose in capturing and assessing the many dynamic aspects of understudied areas relating to hydrogen and energy system change.

5. Conclusions and Future Directions

Today’s hydrogen playing field relies heavily on fossil fuels, yet it is well-positioned for disruptive change in connection with evolving decarbonization, energy security, and geopolitical forces. This confluence of influences presents a unique opportunity for the scaled development of low-carbon hydrogen from frontier sources, namely wind, nuclear, and natural geological reservoirs. Hydrogen’s appeal is further advanced by its versatility and potential for development in countless regions from diverse sources. However, its widespread adoption depends on addressing challenges, such as higher costs, energy inefficiency, and infrastructure adaptations.

Adopting hydrogen at scale requires more than progress in purely the technology itself. Such change must account for the interplay of technology and infrastructure, appropriate policies, economic competitiveness, and feasibility, as well as widespread social acceptance. Currently, a gap is evident between low-carbon targets and supply, highlighting key areas where research could contribute. Cross-cutting research is needed for standardized safety codes and carbon/GHG emission accounting methodologies that factor for verifiable lifecycle assessments. Other key research priorities are tied to energy–water management considerations and infrastructural priorities, reducing costs, and understanding broader impacts. Moreover, research identifying mechanisms to overcome institutional barriers, while investigating how stakeholder incentives, institutional inertia, and governance structures shape hydrogen policy adoption, would be valuable.

This review finds that wind-derived hydrogen is commercially more advanced than nuclear-powered hydrogen, yet the distinct technological profiles of both options may allow them to mature at scale. Somewhat distinctly, natural hydrogen may prove to be more disruptive, as recent discoveries are more fully assessed. In the near term, developing analyses which apply a learning curve model for the prediction of critical points between the technology and regional approaches, along with a targeted SWOT analysis of such options, could be quite beneficial.

Looking ahead, promising avenues for further study are evident. Specific to policy, there are opportunities to expand the scope of country coverage beyond the prime movers that were evaluated to a broader and more diverse mix of countries, which could include Japan and South Korea, for example, considering their recent hydrogen developments. Expanding on the basis of this review article, a full case analysis of countries’ policy and technology developments could be conducted. In addition, evaluating risks tied to geopolitics, policy, and political change could shed important light in these dynamic times.

5.1. Natural Hydrogen

Advances with natural hydrogen as a technological strategy merit ongoing scrutiny, given their disruptive potential for cost-effective, large-scale production.

Near term (up to and including 5 years): Critical research and implementation may focus on appropriate regulatory frameworks and resource evaluation standards that would clarify resource rights and support licensing procedures. In the science and engineering fields, there is a need for fundamental knowledge of how hydrogen moves, is limited, and is contained, in addition to an understanding of the related role of microbes. Geoscience investigation could focus on seeps and areas with high resource potential. With respect to exploration technologies, priorities are to test and adapt technologies from the oil, gas, and geothermal sectors.

Longer term (5+ years): Studies in support of standardized reporting on reserves and national supplies would likely be readily utilized. Applied science could also more systematically map natural hydrogen systems. In terms of technology development, advances in hydrogen-specific exploration tools and predictive geological models could serve key roles.

5.2. Nuclear

Near term (up to and including 5 years): Utilizing simulations and actual pilot data from contemporary demonstration projects, research could expand the fundamental knowledge associated with the safe control of nuclear–hydrogen systems, including conditions for shutdowns, load changing, and emergency conditions. Policy-specific studies could support the development and harmonization of safety standards and regulatory frameworks, market mechanisms, and specifics for co-locating hydrogen production with nuclear facilities. Techno-economic and socio-technical feasibility studies will be necessary for varied reactor types in the evolving technology playing field. For high-temperature steam electrolysis, testing will be necessary to develop safety standards for the specific interfacing and handling of hydrogen. For thermochemical cycles, there is a need to evaluate corrosion-resistant materials and to develop models for process optimization, such as with sulfur–iodine.

Longer term (5+ years): Continued techno-economic and socio-technical feasibility studies will be essential for optimization and cost-effective balancing. This includes Gen IV reactors and their synergies with high-temperature electrolysis and thermochemical cycles. Across nuclear-based technology pathways, timeline analysis for a technology roadmap would also be beneficial.

5.3. Wind

Near term (up to and including 5 years): There is an immediate need for standardization and certification measures, alongside the development of robust methodologies. In addition, there is an opportunity to pilot and assess different policy mechanisms for WHP adoption. Regarding grid integration, there is a need for analysis of regulatory models that account for grid services. Technology-related priorities include demonstrating optimized electrolyzer operation with actual wind profiles and load following to advance dynamic response.

Longer term (5+ years): Research that maximizes capacity factors and reduces curtailment could improve integration. Regarding offshore hydrogen production, studies should evaluate direct seawater electrolysis, materials, and integration.

• Additional research domains include the following:

5.4. Maritime Sector

Near term (up to and including 5 years): Focal areas should include direct seawater electrolysis and offshore generation, as well as onboard storage, safety protocols, and ship design. Comprehensive well-to-wake lifecycle and global emission mechanism assessments will be valuable, in addition to studies of interactions between International Maritime Organization regulations and existing regional policies.

Longer term (5+ years): The synergy potential between hydrogen-powered ships and zero-carbon ports presents a key research opportunity. International standard harmonization, optimal policy mix design for regional pathways, and economic feasibilities will also be critical areas of study.

5.5. Storage

Near term (up to and including 5 years): Important areas for in-depth research include high-density storage materials, onboard storage solutions for maritime shipping, standardized bunker infrastructure, and safety protocols. More broadly, regarding storage, there is a need for comparative analyses of storage methods (compressed gas, liquefied hydrogen, metal hydrides, ammonia) to evaluate their efficiency, safety, costs, and suitability.