Energy storage systems are already being sold around the world to utilities and to homeowners with rooftop solar. However, studies suggest that long-duration energy storage on the scale of days or even weeks, will be necessary to address the seasonal variation of expanded renewable generation. On February 24, OurEnergyPolicy held a webinar examining this issue and featured a panel of experts discussing the potential industry impact of various energy storage technologies, as well as relevant policies. 

While “resource adequacy” is currently defined as four hours of storage by some, panelists suggested that the industry is moving towards eight-hour, multi-day, or even seasonal storage. Though California defines “long duration” as ten hours, panelists noted that roughly two-thirds of outages last longer than this. While storage needs are a function of generation mix and the specific climate of a location, panelists were generally of the opinion that week-long or multi-day storage is where the industry is headed. As panelists discussed, a capacity of roughly 200 hours would have been required to meet the needs of ERCOT during the recent extreme weather events in Texas. 

The conversation ended with a discussion of necessary policy elements to support greater deployment of long-duration energy storage. “Policies must be technology agnostic” was a leading suggestion. Requests for Offers (RFOs), such as the one initiated by community choice aggregations in California, must specify parameters and allow the market to decide and develop what is needed. To this end, panelists also expressed a desire for more precise definitions of terms such as “Reliability.” The final suggestion was for regulatory certainty, which would encourage companies to more readily invest in new approaches.