Energy Storage as Peaking Capacity

With increasing interest in the use of batteries to provide peaking capacity on the grid, my NREL colleagues and I decided to take a look at potential opportunities—particularly for batteries with 4-hour duration. The question is how much actual peaking capacity could be replaced with batteries, given the concern that storage could run out of energy before the end of the peak demand period.

We analyzed the ability of 4-, 6-, and 8-hour storage in different regions of the U.S. power system using a simplified metric that assesses how storage can reduce annual peak net demand. This approach is not a substitute for a full probabilistic resource adequacy analysis, but it can provide some insights into the role of storage as peakers. 

Now published in Renewable Energy, our findings demonstrate that there is a role for 4-hour storage everywhere in the U.S., but it generally works better in places with peaks driven by hot summers. But the really interesting result was observing how much the addition of solar PV to the mix really enhances the ability of storage to meet the peak. Even when PV itself has zero capacity credit, by chopping off the early afternoon peak, PV reduces the amount of storage needed (in terms of hours of capacity) and greatly increases the potential for 4-hour storage. Solar-storage synergy at its finest.