Green hydrogen is emerging as a vital component in the global transition away from fossil fuels. It offers a clean, potent, and versatile energy carrier with the capacity to decarbonise heavy industry and transport, while also providing a means for energy storage. Unlike other hydrogen production methods, green hydrogen production generates virtually no greenhouse gas emissions, making it essential for achieving a net-zero future.
Production Process: Electrolysis Powered by Renewables
The core method for producing green hydrogen is water electrolysis. This process uses an electrical current to separate water (H2​O) into hydrogen (H2​) and oxygen (O2​). The device where this reaction occurs is known as an electrolyser.
The defining characteristic of “green” hydrogen is the source of its electricity. The electricity must originate from renewable sources such as solar, wind, or hydropower. When powered by these renewables, the entire process, from production to combustion, is carbon emission-free. Furthermore, when hydrogen is used in a fuel cell, the sole by-product is water, establishing a perfectly sustainable cycle.
Electrolyser Technologies
The efficiency and cost-effectiveness of green hydrogen production are heavily influenced by the electrolyser technology employed. Several companies specialise in manufacturing this crucial equipment:
- Alkaline Electrolysers: This is the most established and commercially viable technology, utilising a liquid alkaline solution as the electrolyte. Companies like Norway’s Nel ASA have extensive experience with this robust and relatively inexpensive technology.
- Proton Exchange Membrane (PEM) Electrolysers: This technology employs a solid polymer membrane, enabling rapid responses to the fluctuating power output from wind and solar sources. Its primary disadvantage is its reliance on expensive precious metals. Germany’s Siemens Energy and the UK’s ITM Power are prominent leaders in developing and manufacturing these advanced PEM systems globally.
- Solid Oxide Electrolysers (SOECs): These electrolysers operate at very high temperatures, making them the most efficient type. Although still an emerging technology, SOECs show significant promise for industrial applications where waste heat is readily available.
Real-World Applications
These technologies are now transitioning from manufacturing facilities to large-scale real-world projects. A notable example is the NEOM Green Hydrogen Project in Saudi Arabia, where industrial gas giants such as Air Products are constructing a facility powered by gigawatts of renewable energy. This project aims to produce substantial quantities of green hydrogen for export. In Sweden, the H2 Green Steel project is pioneering the use of green hydrogen to replace coal in steelmaking, an initiative designed to decarbonise one of the world’s most carbon-intensive industries.
The Future: Direct Solar Production
While electrolysis remains the dominant method, researchers are actively investigating a more direct approach called photoelectrocatalysis (PEC), also referred to as “artificial photosynthesis.” This forward-looking technology seeks to use semiconductor materials to directly harness sunlight for splitting water molecules. While still in its early research stages, it holds the potential for a simpler long-term method of producing green hydrogen.
Challenges and Future Prospects
Despite its immense potential, scaling up the green hydrogen economy faces several significant challenges:
- Cost: Currently, green hydrogen production is more expensive than “grey” hydrogen, which is derived from natural gas. However, costs are rapidly decreasing as renewable energy becomes more affordable, though further reductions are necessary for widespread adoption.
- Infrastructure: A substantial expansion of renewable energy infrastructure is required to power the electrolysers. Additionally, new infrastructure for hydrogen storage and transportation is essential.
- Water Usage: Large-scale hydrogen production necessitates a significant and consistent supply of purified water, which could be a concern in water-scarce regions.
With increasing investment and ongoing innovation from companies like those mentioned, the trajectory for green hydrogen is becoming clearer. It represents a powerful instrument in the global effort to decarbonise our planet and transition to a more sustainable energy system.
