Motivations and options for deploying hybrid generator-plus-battery projects within the bulk power system

Project developers have increasing interest in hybrid projects that co-locate variable renewable energy plants with batteries at the point of interconnection. This article explores the advantages, disadvantages, development trends, value proposition, and market participation options for U.S. utility-scale hybrid battery projects. Today, power plants with a generating capacity of 4.6 GW are co-located with batteries, with 14.7 GW in the immediate development pipeline and 69 GW in the seven main U.S. market interconnection queues. Current power-purchase agreements suggest that the cost for adding 4-hour battery storage to a solar photovoltaic (PV) project is $4–$14/MWh-delivered, depending on the battery-to-PV ratio. Analysis using recent wholesale market prices finds that, compared to standalone PV and wind generators, 4-hour battery hybrids sized to 50% of the wind/solar nameplate capacity add $13–$31/MWh in combined energy and capacity value in California, while only adding $1–$9/MWh in energy value in Texas. Compared to standalone wind/solar and battery plants, hybridization that restricts grid charging and decreases the hybrid plant’s combined interconnection limits results in a 2–11% loss in wholesale market value. Realizing the value of hybrids depends on nascent participation models and strategies for these resources in wholesale markets. More research is needed to evaluate resource participation in the context of evolving market designs.