A new study conducted by NETL researchers investigated long duration energy storage options that can better accommodate deficits of variable renewable energy (VRE) sources over multi-day and seasonal timescales. The work calls for additional long-term research and development investments to reduce costs and help enable an improved electrical grid that features increasing amounts of VRE.

The study was published in the inaugural issue of Cell Reports Sustainability, a multidisciplinary open access journal that publishes cutting-edge research across natural, applied, and social sciences that seeks to address the world’s grand challenges.

“The intermittency of renewable energy resources is one of the main challenges associated with achieving a sustainable energy system,” NETL’s Rigel Woodside and Lee Aspitarte wrote in the study. “Transitioning the grid to rely primarily on variable renewable energy (VRE) sources while achieving the same degree of reliability currently afforded by fossil fuels will require dramatic changes.

The study first analyzed existing grid energy storage capacity and compared it to projected needs for a U.S. grid with high percentages of VRE. They found that an increase in storage capacity of at least two orders of magnitude will be needed to enable an electricity grid with high amounts of VRE, which will require a significant increase as VRE sources increase.

Implementing the final 20% of VRE will require a much larger storage capacity than the first 80%, because that final need corresponds to multi-day and seasonal variations according to the study. These long duration energy storage (LDES) applications were the focus of the study.

The study shows that the energy storage media cost is the most significant indicator of system viability in LDES applications and energy capital cost targets were determined for the LDES applications.

The study’s authors used a ‘first-principles’ approach to broadly survey candidates for energy storage media that can target LDES applications associated with these cost targets. The study formed a novel dataset of material prices and energy densities to determine a cost floor for the energy capital cost for 376 different storage options.

According to the study, energy storage technologies that demonstrate promise for multi-day and seasonal LDES application are select sensible thermal, latent thermal, thermochemical, synthetic fuel, coupled batteries, and flow battery systems. In contrast, currently deployed energy storage technologies such as Lithium-ion batteries, pumped hydroelectric, and flywheels do not appear to be economically viable for LDES applications. This emphasizes the need for R&D into new LDES focused technologies.

Overall, the results of the study are expected to enable effective new research by providing a map of promising technologies for LDES applications in the overall energy storage technology landscape.

NETL is a U.S. Department of Energy national laboratory that drives innovation and delivers technological solutions for an environmentally sustainable and prosperous energy future. By using its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.