Abstract: California's renewable portfolio standard requires a rapid de-carbonization of the state's electricity supply by 2045. Despite renewables' rapidly decreasing fixed costs, increased reliance on intermittent, primarily solar, generation creates two challenges for California's grid operator — first, maximum solar generation does not coincide with peak demand during the day. Second, locations with the greatest generation potential are distant from the state's demand centers. The spatial mismatch between supply and demand sites increases the frequency of line congestion, causing localized curtailment and negative prices despite the willingness to pay elsewhere. Utility-scale storage promises to mitigate the inefficiencies of intermittent generation by allowing owners to arbitrage electricity across time and space. My research investigates whether batteries operating in California's wholesale electricity market have increased the productivity of renewables, indicated by reductions in curtailment, and whether these impacts varied with the batteries' location.

With co-author, Kevin Novan, we examine the changes in the generation sources and imports from neighboring balancing authorities during battery charging hours to estimate the carbon content of stored electricity. We argue that lithium-ion battery storage facilities should not be treated as zero-carbon generation sources in California's Cap-and-Trade market when there is evidence that they draw imports from regions generating electricity with fossil fuels.