From green hydrogen to solar chemicals and fuels: Assessing strategic policy drivers for technology innovation
Miranda Machado, Júlia Terra
Miranda Machado, Júlia Terra
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Publication Date
2025-10-06
Type
doctoral thesis
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Abstract
This thesis investigates the nexus between hydrogen and a newer, still emerging group of technologies called Solar Chemicals and Fuels (SCF), exploring how targeted policy strategies shape the development, diffusion, and adoption of emerging technologies. It investigates whether, and in what ways, support for hydrogen technologies can also contribute to the development of the less mature SCF technologies. More specifically, it asks Where, When, Why and How current clean hydrogen strategies and policies will also promote the successful development of a solar fuels and chemicals industry – or not. The study examines potential spillover effects between today’s clean hydrogen market and the emerging SCF sector that are derived from this nexus, asking whether these two technological fields are likely to evolve in a more cooperative or competitive direction. The research was conducted within the framework of the Solar2Chem project and received funding from it (MSCA Marie Skłodowska-Curie grant agreement No. 861151).
Recognised by institutions like the IPCC, IEA, and the Joint Research Centre of the European Commission, hydrogen is expected to play a crucial role in reducing industrial emissions and supporting the European Green Deal and has recently, again, attracted strong political attention and investment. Hydrogen can be produced through various methods, each with different carbon footprints and levels of technological maturity, forming what is often referred to as the ‘hydrogen rainbow’. Within this spectrum, hydrogen production includes renewable pathways for green hydrogen production and solar-based subcategories (Solar-to-X and Artificial Photosynthesis) that produce hydrogen. SCF-related processes, also highly diverse and technically complex are still mostly at an early stage and often remaining in laboratory or experimental settings producing, for example golden hydrogen, which relies on photoelectrochemical processes. Therein lies the nexus explored in this PhD. These solar-driven pathways for hydrogen production are gaining prominence for their potential in supporting the versatility of energy systems. Yet, the fragmented and insufficient support for research, development, and innovation across EU member states continues to hinder the advancement of emerging technologies at lower technology readiness levels. Analysing the interaction between hydrogen and SCF is not straightforward, particularly as when it involves future projections. Thus, to address these questions, this thesis uses Energy and Sustainability Transitions theory and Science, Technology, and Innovation (STI) studies. More specifically, the Multi-Level Perspective (MLP) is employed as the main theoretical framework to guide the analysis and identify observable patterns.
This article-based PhD is composed of four academic articles. The first article analyses national hydrogen strategies in Germany, the United Kingdom, and Portugal, with attention to their alignment with EU-level policy, the balance between cooperation and competition. The second article explores how hydrogen can support renewable electricity systems in island regions, particularly through energy storage and solar hydrogen production. The third article presents a SWOT analysis based on both academic and grey literature, to identify strengths, weaknesses, opportunities, and threats in the emerging SCF sector. The fourth article reviews SCF roadmapping efforts from both academic and governmental actors. Together, these articles provide a broad and integrated understanding of how hydrogen and SCF are already interacting and how they might be developed and governed more strategically to support the energy transition in Europe. Across all four articles, one central conclusion appears: the hydrogen market development plays an important role in shaping the progress of SCF.
At present, the nexus between the two sectors can be described as mainly cooperative. In other words, the fourth article finds investment in hydrogen today increases the likelihood that SCF will successfully emerge by the 2040s, but only some SCF technologies are likely to benefit directly from hydrogen policies. The third article confirms the existence of multiple positive and negative drivers, collaboration issues, and that current government policies are not well aligned to support SCF growth. The second article highlights the importance of actors at the regime level, including national grid operators and suggests that SCF could emerge from niche actors, for example on decentralised systems and the military. The first article shows that national hydrogen strategies greatly vary in their ambitions and investment. Countries investing in green or golden hydrogen tend to adopt more cooperative strategies, while those focusing on blue or grey hydrogen offer weaker or more selective support to innovative pathways. Also, in addition to the empirical findings, the thesis contributes to both methodology and theory. Regarding methods, it reflects critically on roadmapping practices and supports the value of SWOT analysis and participatory workshop tools. From a theoretical perspective, the thesis finds the Multi-Level Perspective useful but suggests that it can be strengthened by including insights gained from tools like these to better understand how the different levels interact and reinforce one another.
Finally, the thesis offers several practical recommendations based on its findings. These include the importance of hydrogen fuel certification and the benefits of maintaining a technology-neutral approach rather than attempting to identify and promote specific SCF technologies too early. The study concludes that divergent national hydrogen strategies across Europe raise significant concerns about regulatory coherence, infrastructure readiness, and alignment of sustainable fuels with renewable energy systems and climate goals. It highlights solar chemicals and fuels (SCF) development as highly contingent on stronger policy support and clearer regulatory frameworks for innovation in the area of sustainable fuels and chemicals. Overall, the findings call for coordinated strategies, inclusive roadmaps, and multi-level governance to unlock the transformative potential of hydrogen and SCF technologies. In summary, this research offers an original and detailed analysis of how two interrelated technological areas are evolving as part of the global energy transition. It also provides guidance on how their interaction could be better managed in order to realise the potential of SCF in the near future.
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University of Galway
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CC BY-NC-ND