Researchers at ETH Zurich, led by Professor Wendelin Stark, have developed a technology for the seasonal storage of hydrogen using iron. This innovative solution promises to be safer, cheaper, and more efficient than existing hydrogen storage methods. It has the potential to revolutionize the way we store and use renewable energy.
The Challenge of Seasonal Energy Storage
Photovoltaics will meet over 40% of Switzerland’s electricity needs by 2050, posing a significant challenge. The country must balance the supply and demand of renewable energy. Solar power is abundant in summer but scarce in winter when energy demand peaks. Switzerland plans to rely on imports, wind, hydropower, alpine solar plants, and gas-fired power plants to close this winter electricity gap.
Producing hydrogen from excess solar power in summer and converting it back to electricity in winter could minimize the need for imports and gas-fired power plants. Safety concerns and high costs associated with traditional hydrogen storage methods are the main hurdles in implementing this solution.
The Steam-Iron Process
Professor Stark and his team have turned to the well-known steam-iron process to overcome the challenges of hydrogen storage. They have developed a safe and cost-effective storage system using natural iron ore, a widely available and inexpensive material.
The process feeds hydrogen, produced from excess solar power, into a stainless steel reactor. The reactor contains iron ore at 400 degrees Celsius. The hydrogen extracts oxygen from the iron ore, creating elemental iron and water. This process resembles charging a battery, allowing the energy in the hydrogen to be stored as iron and water with minimal losses.
When energy is needed in winter, the process is reversed. Hot steam enters the reactor, turning the iron and water back into iron oxide and hydrogen. A gas turbine or fuel cell then converts the hydrogen into electricity or heat.
Key Advantages of Iron-Based Hydrogen Storage
- Cost-effectiveness: The raw material, iron ore, is abundant and inexpensive, making this storage technology an estimated ten times cheaper than existing methods.
- Safety: The reactor does not require special safety measures, as it consists of stainless steel walls just 6 millimeters thick and operates at normal pressure.
- Scalability: Storage capacity can be easily expanded by building larger reactors and filling them with more iron ore.
- Reusability: Once filled with iron oxide, the reactor can be used for multiple storage cycles without replacing its contents.
Pilot Plant Demonstration and Future Plans
The researchers have demonstrated the feasibility of their storage technology using a pilot plant on the ETH Hönggerberg campus. The pilot plant can store around 10 megawatt hours of hydrogen, equivalent to the electricity demand of three to five Swiss single-family homes in winter.
By 2026, the researchers aim to expand the system to meet one-fifth of the ETH Hönggerberg campus’s winter electricity requirements using its own solar power from the summer. This would require reactors with a volume of 2,000 cubic meters, capable of storing around 4 gigawatt hours (GWh) of green hydrogen.
Scalability for Switzerland’s Energy Needs
Initial calculations suggest that providing Switzerland with around 10 terawatt hours (TWh) of electricity from seasonal hydrogen storage systems every year would require 15–20 TWh of green hydrogen and roughly 10,000,000 cubic meters of iron ore. This equates to about 2% of Australia’s annual iron ore production.
To store 1 GWh of electricity, reactors with a volume of roughly 1,000 cubic meters would be needed, each requiring around 100 square meters of building land. Switzerland would need to build some 10,000 of these storage systems to obtain 10 TWh of electricity in winter, corresponding to an area of around 1 square meter per inhabitant.
The Bottom Line
Iron-based hydrogen storage offers a promising solution for seasonal energy storage, addressing the challenges of safety, cost, and scalability associated with traditional hydrogen storage methods. As researchers at ETH Zurich continue to refine and expand their pilot plant, this innovative technology could play a significant role in Switzerland’s transition to a more sustainable and self-sufficient energy future.
Read more: Swiss Iron Reactors Store Hydrogen 10x Cheaper, Safer, Longer
