Analyzing the Emissions Impact of Long Duration Energy Storage in California

Just as energy storage can perform arbitrage on energy prices, it can also perform arbitrage on emissions. This paper discusses the co-benefit of using long duration energy storage to reduce the net emissions of power systems by charging when the local emissions rate is low and discharging when the local emissions rate is high. To quantify the total impact, the analysis optimizes the dispatch of solar and battery energy storage to minimize electricity costs and weighed emissions. The paper uses public data sources for solar resource availability, the marginal operating emissions rate, and utility rate data. The Viejas microgrid project, in the San Diego area, is used as a casestudy to demonstrate a newly developed software tool that enables this analysis to be performed on long duration energy storage projects across California. The results of this study show that the addition of storage greatly reduces both cost and emissions, even when the controller ignores the emissions rate. Further, accounting for grid emissions in the storage controller is an extremely cost-effective way of offsetting emissions, costing as little as ${\$}$ 2.17 per ton on the marginal offset of 47.4 kTCO 2 e. Over a 20 year period, depending on the weight the storage controller applies to grid emissions, the project is estimated to reduce electricity bills by ${\$}$ 88.3 M-${\$}$ 88.5 M and reduce emissions by 84.2-131.6 kTCO2e.