Suitability of 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. Solid oxide technology, whilst less mature than alkaline and PEM technology, offers superior conversion efficiency -especially for electrolysis.Furthermore, the possibility of using the cells reversibly means that separate 'power-to-gas' and 'gas-to-power' components are not needed, potentially reducing costs. In this work, we consider the suitability of energy storage using rSOCs and/or battery storage for a microgrid consisting of houses equipped with solar PV generation. An agent-based simulation model is developed to assess the performance of such a microgrid. The model enables the microgrid's self-sufficiency to be quantified, and hence the possible cost savings through avoided imports of grid power. Sizing of microgrid components is optimised to determine the most cost-effective design capable of achieving given selfsufficiency ratio. Case studies are considered for England and Texas. Initially, designs are considered with hydrogen energy storage only; subsequently, hybrid energy storage is considered, with a community scale battery working alongside the rSOC. Results suggest that payback periods for pure rSOC systems tend to be unfavourable. However, if prices fall to levels foreseen in the literature, a system designed to achieve 50% grid-independence could pay back its investment costs within 20 years. Systems designed for Texas need relatively less storage, owing to the good year-round solar resource; as such, payback time in Texas is superior to the UK. Hybrid storage with battery + rSOC is found to be preferable to battery only systems when (i) high SSR is required and (ii) large over-capacity of PV generation is not possible.

Advancing the multiscale understanding on solid oxide electrolysis cells via modelling approaches: A review

“…Their work obtained a robust operation schedule for the energy hub. Hutty et al [109] introduced a system model to simulate the operation of a microgrid composing of houses coupling with the solar photovoltaic unit and SOEC/battery. The model was used to optimize the size of units of the microgrid and quantify the self-sufficiency ratio.…”

Experimental validation of a dynamic modelling of a Reversible Solid Oxide Cells (rSOCs)

“…The reversible behaviour between electrolyzer (SOE) and fuel cell (SOFC) has been implemented in the elementary cell sub-model using experimental data. This would allow to simulate the storage of a surplus of energy produced by renewable sources [21] in the form of hydrogen and vice versa the conversion of hydrogen into electrical energy The use of SOCs systems at high operating temperatures shows a low impact of activation overvoltages compared to low temperature systems [9] and these systems show negligible mass transport effects at high currents and low fuel utilization (steam or natural gas). Moreover, the experimental data used for the validation of the model did not cover this type of case and for these reasons, the use of a simple ohmic model does not introduce significant errors.…”

Uncertainty and simulation‐based cost analyses for energy storage systems used in green buildings

“…Hutty et al estimated that the efficiency of fuel cells would optimistically increase by 45%. 33 Again, a pessimistic approach was taken, and only a 30% increase was considered. Regarding batteries, a maximum efficiency of 93.7% was considered according to IRENA.…”