## 1 Introduction  
Climate change is causing increasingly severe impacts globally, requiring immediate and effective responses. The European Union (EU) has proactively addressed these challenges through several strategic initiatives. The European Green Deal, launched in 2019, aims to achieve climate neutrality by 2050 and foster sustainable economic growth, resource efficiency, innovation, and social inclusivity [1]. Key policies such as the \"Fit for 55\" legislation support this vision, targeting a fair and economically viable reduction in greenhouse gas emissions by at least 55% by 2030, relative to 1990 levels [2]. All 27 EU Member States have committed to these ambitious climate goals, making Europe the first continent aiming for climate neutrality. In 2021, the EU Commission launched \"Next Generation EU\", a major funding program to support economic recovery and accelerate Europe's green and digital transition [3]. Subsequently, the REPowerEU plan was introduced to boost renewable energy deployment, increase energy efficiency, diversity energy sources, and reduce dependence on fossil fuels [4]. In March 2023, the EU strengthened its commitment by raising the binding target for renewable energy to at least 42.5% by 2030, with an aspirational goal of 45%. To further advance its strategy, the EU Commission adopted a dedicated solar energy plan in May 2022, aiming for more than 320 GW of solar capacity by 2025 and nearly 600 GW by 2030. This was supported by revised regulations, including the updated Renewable Energy Directive, to streamline permitting and accelerate the deployment of renewable energy projects [5]. Advanced solar technologies, such as Concentrated Solar Power (CSP), are central to the EU's renewable energy strategy. By integrating thermal energy storage (TES), these systems enable on-demand electricity generation and help address the intermittency of solar resources. However, for CSP to play a significant role in the EU energy mix, further progress is needed to improve cost competitiveness through both technological innovation and economies of scale. Meanwhile, energy storage is becoming increasingly essential for stabilizing fluctuations in electricity supply and demand. As energy systems increasingly rely on renewable energy sources (RESs), energy storage has become ever more crucial in achieving a carbon-neutral economy. Hydrogen, in particular, is emerging as a key element in this transition and features prominently in several EU policies. Both the European Green Deal and REPowerEU emphasize the instrumental role of renewable hydrogen in supporting secure, affordable, and sustainable energy solutions, including the development of hydrogen valleys. Furthermore, under the Net-Zero Industry Act of the Green Deal, hydrogen fuel cells are identified as critical technologies. The Green Deal's Act also ensures the availability of important materials for electrolyzers and RES, supporting the secure and clean production of renewable hydrogen. At the international level, the Clean Hydrogen Mission of Mission Innovation aims to reduce the cost of renewable hydrogen and promote the development of hydrogen valleys worldwide. These coordinated efforts are strengthening the integration of hydrogen in Europe, enabling the supply of renewable energy to households, industries, and the transport sector. Acting as an energy carrier, hydrogen has the capability to transport and store vast amounts of energy derived from renewable sources over extended periods, or directly serve as a fuel, particularly within industrial and transport applications [6]. This positions it as a key component in the clean energy transition. The increasing importance of renewable, often termed \"green\" or \"clean\", hydrogen is critical for Europe to meet its climate change objectives, reduce greenhouse gas emissions, and achieve strategic energy independence through domestic production [7].