In recent years, green hydrogen has emerged as a cornerstone in the transition towards a more sustainable and renewable energy future. It’s an innovative energy carrier that holds the potential to revolutionise how we produce, store, and use energy, marking a significant step forward in efforts to combat climate change and reduce global reliance on fossil fuels. Green hydrogen refers to hydrogen gas that is produced through the electrolysis of water, a process that splits water into hydrogen and oxygen using electricity. What distinguishes green hydrogen from other forms of hydrogen production, such as grey or blue hydrogen, is the source of electricity used in this process. For hydrogen to be considered “green,” the electricity must come from renewable energy sources, such as wind, solar, or hydroelectric power. This ensures that the production process emits no carbon dioxide or other harmful greenhouse gases, making green hydrogen a clean and sustainable energy carrier. The technical process of producing green hydrogen is rooted in electrolysis, an established technology that has been around for decades but has recently seen advancements in efficiency and cost-effectiveness. Modern electrolyses operate using one of three main technologies: alkaline electrolysis, proton exchange membrane (PEM) electrolysis, and solid oxide electrolysis. Each technology has its unique advantages and is suitable for different applications and scales of production. Alkaline electrolysis, the most mature and widely used technology, involves the use of an alkaline solution as an electrolyte. In contrast, PEM electrolysis uses a solid polymer electrolyte and can operate at higher efficiencies and dynamic load ranges, making it well-suited for coupling with intermittent renewable energy sources. Solid oxide electrolysis, though less commercially developed, operates at high temperatures and promises even higher efficiencies by utilising heat as well as electricity. But how useful can this form of energy be? The applications of green hydrogen are diverse and span across various sectors, including transportation, industry, and power generation. In the transportation sector, green hydrogen can be used as a fuel for fuel cell electric vehicles (FCEVs), offering a clean alternative to fossil fuels for cars, buses, trucks, and even ships and airplanes. The advantage of using hydrogen in this context lies in its high energy density and the fact that water vapour is the only emission from its use in fuel cells. In the industrial sector, green hydrogen presents an opportunity to decarbonise processes that are currently reliant on fossil fuels. For example, it can be used as a feedstock in the production of ammonia and methanol, as well as in steel manufacturing, replacing coal in the reduction of iron ore. These applications are particularly significant because they address emissions from hard-to-abate sectors, where direct electrification is not feasible or economically viable. Additionally, green hydrogen can play a critical role in the energy sector by offering a solution for energy storage and grid balancing. Renewable energy sources like wind and solar are intermittent by nature, producing electricity that does not always match the demand patterns. Green hydrogen can be produced during periods of excess electricity generation, stored efficiently, and then converted back to electricity or used directly when demand is higher, or renewable energy generation is low. This capability not only helps in stabilising the grid but also in increasing the penetration of renewables in the energy mix. But despite its potential, the widespread adoption of green hydrogen faces challenges, primarily related to cost and infrastructure. The production of green hydrogen is currently more expensive than traditional hydrogen production methods that use fossil fuels, mainly due to the high costs of electrolyses and renewable energy. However, these costs are expected to decrease with technological advancements, economies of scale, and increased investment in renewable energy infrastructure. Moreover, the development of transportation and storage infrastructure for hydrogen is crucial for its deployment across different sectors and regions. This includes pipelines, tankers, and storage facilities that can handle hydrogen’s unique properties, such as its low density and reactivity. The future of renewable energy is inherently linked to the advancement and integration of technologies like green hydrogen. As the world seeks to reduce greenhouse gas emissions and transition away from fossil fuels, green hydrogen offers a versatile and sustainable solution that can complement other renewable energy sources. Its ability to store energy, decarbonize various sectors, and provide clean fuel options positions green hydrogen as a key player in the global effort to combat climate change and move towards a more sustainable energy future. While challenges remain, the ongoing research, policy support, and investment in green hydrogen are indicative of its potential to contribute significantly to the renewable energy landscape. The integration of green hydrogen into the global energy system also needs international cooperation and policy frameworks that encourage its development and use. Governments and international bodies are increasingly recognising the importance of green hydrogen in achieving climate goals, leading to the formulation of strategies and incentives aimed at accelerating its production and adoption. This includes funding for research and development, subsidies for green hydrogen projects, and regulations that favour low-carbon technologies. Furthermore, the establishment of standards and certifications for green hydrogen can ensure that its production meets environmental and sustainability criteria, thereby increasing consumer and investor confidence. As such, the collaboration between countries, industries, and research institutions is critical in overcoming the technical and economic barriers to green hydrogen, paving the way for a future where renewable energy systems are interconnected and resilient, powered by green hydrogen as a key enabler of decarbonisation and energy security.