A University of Texas at Arlington materials science and engineering team has developed a new “photoelectrochemical” energy cell that can efficiently store solar energy and deliver electrical power 24 hours a day. It can also be scaled up to provide large amounts of energy, limited only by the size of its chemical storage tanks, according to Fuqiang Liu, an assistant professor in the Materials Science and Engineering Department who led the research team.

The innovation is based on an all-vanadium photoelectrochemical flow cell that allows for storage of electrons in the cell — an advance over the most common solar energy systems, which are restricted to using sunlight immediately as a power source. The team is now working on a larger prototype.

“The ability to store solar energy and use it as a renewable alternative provides a sustainable solution to the problem of energy shortage as renewable energy becomes more prevalent,” Liu said.

The research is detailed in the journal ACS Catalysis. The work was funded by a 2013 National Science Foundation $400,000 Faculty Early Career Development grant awarded to Liu.

UPDATE July 6, 2015: Follow-up Q&A with Prof. Liu

KurzweilAI: Regarding your statement, “Compared to battery, this cell is more efficient and offers much higher capacity.” Could you quantify the efficiency and capacity comparison?

Liu: Our system is different to existing solar energy storage systems; therefore, a precise comparison is difficult to make. However, our system has already demonstrated ~95% Faradaic efficiency and more than 10x higher in peak IPCE (Incident photon-to-current efficiency) compared to conventional photo-generation of hydrogen, a widely accepted approach for solar energy storage.

KurzweilAI: How does your system compare to conventional lithium ion batteries?

Liu: We do not have solid data to compare our system to conventional lithium ion batteries.

KurzweilAI: One of our readers asked how the CellCube energy storage system relates to your technology.

Liu: Our approach mimics a redox flow battery (the CellCube energy storage system)in the discharge direction. Besides, our monolithic approach, with an internally integrated photoelectrochemical system and a redox flow battery, obviates the need for externally hooking up a (solid-state) PV system with a battery. In this regard, and it shares much of the same logic behind a photoelectrochemical water splitting device as opposed to a hybrid PV-water electrolyzer combination.

Abstract of Reversible Electron Storage in an All-Vanadium Photoelectrochemical Storage Cell: Synergy between Vanadium Redox and Hybrid Photocatalyst