Gas turbine peakers vs batteries: The equation today

A key application of gas turbines is as peakers especially in grids with high renewable penetration. But batteries have been gnawing away at this market segment. Today, battery sizes of 10 MW are common and installations are expected to grow to 10 GW by 2025. Cost is declining towards $250/KWHr, too. A presentation by Ihaab Chaban, GE Aero commercial development director, at PowerGen International fleshed out the pros and cons of this.

On the plus side for batteries, Chaban said costs are declining faster than expected and production volumes are accelerating. Behind the meter economics is improving and there is potential for a greater-than 50% cost reduction by mid-20s. Batteries have instantaneous response; have no emissions; need no water nor fuel infrastructure; are modular and transportable. They can be installed in a few months and they soak up excess renewable generation to dispatch it when the system needs.

While these are clear advantages and promise a rosy future, Chaban detailed the advantages that gas turbines have that continue to be attractive. The state-of-the-art that has made batteries attractive are the four-hour devices. But four-hour batteries can't provide all the services provided by the gas turbines, he said. Further, 90% of US combustion turbines run more than four hours at least once  a year. Longer duration is needed to maintain reliability. Statistical studies show 4 hour batteries are not equivalent to gas peakers. EFC (Stochastic studies) indicate a 60-90% de-rate is more appropriate. GE Energy Consulting study for NYISO shows a 4 hour battery should be assigned ~50% capacity value in New York, he said.

Capacity values for 4-hour batteries rise nearly 10% (pts) with higher renewables. Also, for longer durations of storage, the BESS needs to charge a previous day requiring much longer duration storage and the ability to forecast net demand over extended periods.