Chapter 9. Unitised Regenerative Fuel Cells

A unitised regenerative fuel cell (URFC) is a single cell or stack of cells that can operate as a fuel cell (FC) or an electrolyser (E). In the E-mode, by supplying the required power, water splits into oxygen and hydrogen that is stored and can be used to generate power in the FC-mode. This technology has great potential to become part of a viable sustainable energy storage solution to support renewable energy systems. However, the technology is yet to achieve maturity for commercialisation as the remaining challenges associated with performance, durability and cost need to be adequately addressed. In this chapter, the different types of URFCs are introduced with particular emphasis on proton exchange membrane (PEM) URFCs. The design considerations at components level (i.e. MEA, catalyst layer, gas diffusion layer, and bipolar plates) as well as stack and system levels are discussed. This chapter also discusses the main challenges to be addressed and future prospects for further improvement of this technology.