Long term energy storage with reversible solid oxide cells for microgrid applications

Abstract

Reversible solid oxide cells (rSOCs) offer the prospect of long term bulk energy storage using hydrogen or methane fuel. Whilst less mature than alkaline and PEM fuel cell/electrolysis technology, solid oxide cells offer superior efficiency: as high as 80–90%LHVat system level. Furthermore, the possibility of using the cells reversibly means that separate ‘power-to-gas’ and ‘gas-to-power’ components are not needed. Here, we consider the suitability of a hydrogen energy storage system (HESS) using rSOCs for a solar-powered residential microgrid. Battery energy storage (BESS) is considered as a competing (or complementary) energy storage technology. Since the electrification of transport is likely to be a major aspect of the transformation of domestic energy consumption, electric cars are also included in the microgrid model. The performance of the microgrid is evaluated in terms of its grid independence (self-sufficiency ratio, SSR) and economics (simple payback time and net present value). Optimisation is used to select and size the microgrid’s components under different scenarios. Optimisation results suggest that battery storage is often preferred to HESS. However, two factors in particular can cause the selection of HESS to be favoured: (i) a requirement for high SSR and (ii) a lower constraint (6 kW) on the PV capacity per household. The economics for such systems remain very challenging.

Keywords

• Energy storage
• Reversible solid oxide cell
• Microgrid
• Hybrid energy storage
• Self-sufficiency ratio
• rSOC