Evaluating the application of energy storage and day-ahead solar forecasting to firm the output of a photovoltaic plant

The cost of photovoltaic (PV) electricity is competitive with some high cost forms of natural gas electricity in some areas. However, the variability of PV energy increases the cost to utilize it. This increased cost is partially shouldered by imbalance penalties assigned to the plant owner. Energy storage and forecasting services are two techniques that have been proposed to reduce the penalties. This paper quantifies the level of energy storage and forecasting necessary to reduce, or firm, the intra-hour variability of a PV plant. It also assesses the economics of using a battery energy storage system (BESS) to firm output, finding that more than a 90% cost reduction is required to justify deployment of a BESS. Finally, the viability of a BESS providing multiple services to the power system is assessed.