Achieving 50 Percent Renewable Electricity in California

Union of Concerned Scientists / by James H. Nelson and Laura M. Wisland

Key findings
• The modeling demonstrates that California can integrate 50 percent renewable energy into our electricity mix by 2024, faster than envisioned by current state proposals.
• If California makes no additional investment in grid flexibility beyond projected levels, raising the Renewables Portfolio Standard from 33 percent to 50 percent would reduce greenhouse gas emissions from electricity generation by 22 percent. This will be accomplished largely by producing energy with renewables instead of natural gas. But if California uses additional low or zero-carbon grid management methods such as storage, demand response, electricity exports, and more flexible operation of renewable generators, greenhouse gas emissions would drop by 27 percent.
• The long-term goal of reducing greenhouse gas emissions in the electricity system will require integrating more renewable energy and turning down gas power plants as much as possible. The modeling results suggest that the ramping ability of existing combustion turbine and peaker gas plants will be sufficient in 2024, and installation of additional gas capacity to meet ramping needs would not be warranted.
• If wind and solar power are allowed to play a bigger role in providing reliability services, 44 percent less renewable energy would be curtailed.
• California can also maintain adequate grid flexibility and reliability while reducing reliance on natural gas by deploying a combination of advanced demand response—which shifts energy consumption to periods when the grid needs it the most — and energy storage like batteries. These technologies can help to reduce renewable energy curtailment and carbon emissions. In some cases, these grid management solutions deliver even greater flexibility than natural gas because they can provide grid reliability services without having to be online and simultaneously generating electricity.

As we reach 50 percent renewables on the grid and strive for even higher levels of carbon-free generation, we need to think about how renewables can help to integrate themselves into the electricity grid by providing significant grid management services as well as energy. This study helps to quantify the value of moving in that direction…


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