NREL says added storage in California grid needed to aid renewable integration

Achieving California’s low-carbon energy rules with limited curtailment of generation resources is possible by 2030, but enhanced flexibility, with a lot more storage capacity and enhanced ability to export power out of state, will be needed to aid integration of renewable resources, the National Renewable Energy Laboratory (NREL) said in a report.

The report is one of several efforts by NREL to show that there are multiple roads to getting more renewable resources in California without causing too much stress on the power grid, an official with NREL said in a March 17 email statement to TransmissionHub.

“Successful integration of these variable generation resources will require increased grid flexibility and greater consideration of the optimal mix of both renewable resources and flexibility options,” said Aaron Bloom, project manager and member of the Energy Forecasting and Modeling Group at NREL.

Energy storage technologies can assist in this regard, “but these technologies need to be compared to alternative sources of grid flexibility to ensure least-cost deployment of renewables,” Bloom said.

NREL will host a webinar on April 14 on exploring renewable energy integration in California, Bloom noted, adding that a couple recent report likely will be discussed.

One of those reports, an analysis of how California can achieve a 50% reduction from 2012 carbon dioxide emission levels by 2030, examines different scenarios and assumptions to reach that goal. The report, published by NREL in January, concludes that unless grid flexibility improves, curtailment of generation could climb by 10%, operational costs could rise by $800m and carbon emissions could increase by 14%.

The added flexibility provisions include 1 GW of new pumped hydropower storage resources, 1.2 GW of new out-of-state compressed air energy storage and the 1.5 GW of battery storage that is currently called for in state regulations, NREL said.

Traditional hydropower and pumped hydropower storage resources are currently limited in providing ancillary services in California, but the added flexibility scenario lifts some of those restrictions.

The enhanced flexibility also involves being able to shut down natural gas-fired generation to make room for renewables and increasing California’s ability to export what NREL termed California-entitled energy, which refers to generation that is owned by or contracted to California utilities but located outside the state.

“Achieving enhanced levels of flexibility may be more difficult if neighboring states will not purchase California-entitled generation even when that is the lowest-cost option,” NREL said.

Current provisions limit imports and exports of generation from renewable, nuclear and hydropower facilities at specific levels, and under the enhanced flexibility provisions there are only physical grid limitations on imports and exports, NREL said.

For the transmission sector, the current provisions call for adding transmission needed to bring renewable resources to load centers, while the added flexibility scenario includes a new transmission line from Idaho to southern Nevada to relieve grid congestion and improve resource diversity throughout the West, the report said.

The addition of electric vehicles can aid integration of renewables if they are charged at optimal times that would represent up to 3,000 MW of load to avoid curtailment of renewable resources, NREL said.