Keep it short: Exploring the impacts of configuration choices on the recent economics of solar-plus-battery and wind-plus-battery hybrid energy plants

Commercial interest in renewable-battery hybrid power plants connected to the bulk power system (“hybrids”) is rapidly growing in the United States and globally. Since hybrid power plant operational behavior depends on underlying design choices, understanding what configurations of hybrids are likely to be deployed in the near-future is important for bulk power system planners responsible for ensuring overall system reliability and planning the transmission network.  We use historical wholesale market power prices in the seven U.S. organized wholesale power markets from 2012–2019 to calculate hybrid net values, subtracting costs from revenues, across a wide range of wind and solar hybrid configuration choices to evaluate trends in the commercial development of hybrids and identify factors that may alter those trends.  Configuration choices considered here include battery duration, battery power capacity, size of the grid interconnection capacity relative to the generator power capacity, the size of PV panels relative to the inverter capacity, and the way that batteries and generators are coupled. We find that the battery duration and battery capacity have the largest impact on the net value of solar and wind hybrids, with the most attractive hybrids having a two-hour battery duration. We find that it is more attractive to set the interconnection capacity to accommodate simultaneous discharge of the generator and the battery, as opposed to limiting the interconnection capacity to the generator power rating, particularly for solar hybrids in the ERCOT and SPP markets. The choice between AC and DC coupling and the sizing of the PV panels relative to the inverter in solar hybrids are secondary to other configuration decisions. Our analytical results align with current commercial trends of online and proposed hybrid projects, thereby suggesting that the net value framework we employ can be used to understand recent commercial hybrid development activity.