U.S. company Sperra, which is working with German companies Fraunhofer IEE and PLEUGER Industries GmbH on a subsea energy storage system has been awarded $7.7 million in grants from the U.S. Department of Energy Water Power Technologies Office and the German Ministry for Economic Affairs and Climate Action (BMWK).
The companies are developing a Subsea Pumped Hydroelectric Storage (SPHS) system for storing energy on the sea bed that works similarly to open loop pumped hydro energy storage. In open loop pumped hydro storage, water is pumped from a lower elevation up to a reservoir at a higher elevation where it is stored during times of abundant energy. The stored water serves as a source of potential energy. When other intermittent clean energy sources such as wind and solar are low, the reservoir releases the stored water to return to the lower elevation through a tunnel with a turbine to create electricity.
The difference with SPHS is that when energy is high, water is pumped up to the surface from tanks on the sea floor, leaving a near vacuum in the containers. Then, when other energy sources are low, the pressure of the ocean pushes seawater back into this pressure chamber through a turbine, creating electricity.
The company said SPSH is a strong alternative to batteries because it does not rely on the critical materials needed for battery production. Extraction of such materials, such as lithium and cobalt, results in environmental damage and has been a source of human rights abuses.
Also, the containers can largely be manufactured with locally-sourced concrete. Sperra’s energy storage tanks are constructed of concrete, using 3D printing.
The company said the U.S. has approximately 75 terawatt-hours of unused offshore potential, which is more than twice the potential of onshore closed-loop pumped storage.
In this project, Sperra will design, fabricate, and test a 10-m diameter, 500 kW / 600 kWh energy storage unit off the coast of Southern California. The German funding will support a parallel pump and turbine development project run by Fraunhofer IEE and PLEUGER Industries GmbH.
“This project is a major step forward to realizing the full potential of energy storage to decarbonize our electric grid,” said Jason Cotrell, CEO and Founder of Sperra. “SPSH with 3D-printed concrete will accelerate the energy transition, employing local labor and using immediately available materials. We are very excited about the international collaboration on this project with Fraunhofer IEE and PLEUGER, and are grateful that the Water Power Technologies Office recognizes the tremendous potential of this work.”
Sperra’s approach will build on the work of Prof. Horst Schmidt-Böcking, Dr. Gerhard Luther, and Fraunhofer IEE on a subsea energy storage technology called “Stored Energy in the Sea” (StEnSea).
“Pumped storage power plants are particularly suitable for storing electricity for several hours to a few days. However, their expansion potential is severely limited worldwide. Therefore, we are transferring their functional principle to the seabed – the natural and ecological restrictions are far lower there. In addition, the acceptance of the citizens is likely to be significantly higher,” explains Dr. Bernhard Ernst, Senior Project Manager at Fraunhofer IEE.
