ETOGAS: A German Innovated Solution for Storing Excess Solar and Wind Power
As the world shifts towards renewable energy sources, the intermittent nature of solar and wind energy poses a significant challenge to balancing the grid. Solutions to store excess energy from these sources are becoming increasingly critical. ETOGAS, a German-developed technology, presents a promising approach to address this issue. In this article, we delve into the fundamentals of this technology, its implementation, and its potential as a robust solution to the problem of energy storage.
Overview of the Problem
Recent grid simulations on the Texas electricity grid from 2030-2040 have shown that, despite ambitious forecasts of 100% renewable energy, a single storage solution would be insufficient. The grid might see an excess of 28 average solar and wind power units, leading to an 18-unit supply deficit without storage. To eliminate this deficit, a massive 14,000 GWh of electricity storage would be necessary.
Current Storage Technologies
Batteries offer a round trip efficiency ranging from 75-85%, making them a viable but expensive option. While they are a cost-effective solution, they are not feasible for the scale required. On the other hand, power-to-gas and back to power systems are more cost-effective but less efficient, with a round trip efficiency of approximately 43%. This efficiency comes from the process of electrolysing water to produce hydrogen and then using the hydrogen to run modified gas turbines, though the widespread availability of gas turbine generators that can run on hydrogen is still limited.
The Promise of ETOGAS
ETOGAS is a project that uses power-to-gas technology, converting excess renewable energy into methane which can be stored and later converted back into electricity. This technology is particularly promising due to its scalability and efficiency. The project involves a 6 MW electrolyser, making it the largest ‘spare electricity to methane’ project to date. Despite not including the return process to electricity, the concept has proven viable at a significant scale.
Technological Advantages of ETOGAS
The process of converting hydrogen to methane using carbon dioxide and utilizing standard gas turbine generation equipment for output has brought about several key advantages. The round trip efficiency is reduced to around 34%, but the use of natural gas grids and storage facilities makes it exceptionally cheap. Every country except Hong Kong runs natural gas grids, and salt caverns or depleted gas fields can be used for storage. Storing methane at 200 atmospheres provides the same stored energy density as lithium-ion batteries, making it an extremely attractive option.
Future Prospects
Looking ahead, a third power-to-gas technique might emerge, offering a long-term efficiency around 70%. This potential solution could theoretically replace batteries, allowing for a one-tier storage system. The solid oxide fuel cell technology, which electrolyzes a mixture of water and carbon dioxide, is expected to increase efficiency and reduce the need for additional renewable energy sources.
Conclusion
ETOGAS represents a significant step forward in renewable energy storage technology. While not a final answer, its success in demonstrating the concept at scale makes it a robust solution to the problem of storing excess solar and wind power. As research and development continue, this technology could play a central role in transitioning to a more sustainable and reliable energy future.