Technology Assessment for the Transition to a Renewable Electric Grid

To reduce carbon emissions, generation of electricity from combustion systems is being replaced by renewable resources. However, the most abundant renewable sources – solar and wind – are not dispatchable, vary diurnally and are subject to intermittency, and produce electricity at times in excess of demand (excess production). To manage this variability and capture the excess renewable energy, energy storage technologies are being developed and deployed such as battery energy storage (BES), hydrogen production with electrolyzers (ELY) paired with hydrogen energy storage (HES) and fuel cells (FCs), and renewable natural gas (RNG) production. While BES may be better suited for short duration storage, hydrogen is suited for long duration storage and RNG can decarbonize the natural gas system. California Senate Bill 100 (SB100) sets a goal that all retail electricity sold in the State must be sourced from renewable and zero-carbon resources by 2045, raising the questions of which set of technologies and in what proportion are required to meet the 2045 target in the required timeframe as well as the role of the natural gas infrastructure, if any. To address these questions, this study combines electric grid dispatch modeling and optimization to identify the energy storage and dispatchable technologies in 5-year increments from 2030 to 2045 required to transition from a 60% renewable electric grid in 2035 to a 100% renewable electric grid in 2045. The results show that, by utilizing the established natural gas system to store and transmit hydrogen and RNG, the deployment of battery energy storage is dramatically reduced. The required capacity for BES in 2045, for example, is 40 times lower by leveraging the natural gas infrastructure with a concomitant reduction in cost and associated challenges to transform the electric grid.