California set two renewable energy records around the beginning of this month: the most solar power ever flowing on the state’s main electric grid and the most solar power ever taken offline because it wasn’t needed.
There’s no contradiction: As California utilities buy more and more solar power as part of the state’s quest to confront climate change, supply and demand are increasingly out of sync. The state’s fleet of solar farms and rooftop panels frequently generate more electricity than Californians use during the middle of the day — a phenomenon that has sent lawmakers and some climate advocates scrambling to find ways to save the extra sunlight rather than let it go to waste.
But for ratepayers, an oversupply of solar power might actually be a good thing.
New research published in the peer-reviewed journal Solar Energy suggests California should embrace the idea of building more solar panels than it can consistently use, rather than treating oversupply as a problem to be solved. It sounds counterintuitive, but intentionally overbuilding solar facilities — and accepting they’ll often need to be dialed down in the absence of sufficient demand — may be the best way to keep electricity prices low on a power grid dominated by renewable energy, the research found.
In a study published in March, New York-based researchers Richard Perez and Karl Rábago argue that solar power has gotten so inexpensive that overbuilding it will probably be the cheapest way to keep the lights on during cloudy or overcast days — cheaper than relying entirely on batteries. Solar power can meet high levels of daytime electricity demand without energy storage, the researchers say, as long as there are enough solar panels on the grid during times when none of them are producing at full capacity.
“It’s not like solar is going to be available all the time,” said Perez, a solar energy expert at the State University of New York at Albany. “At night you will need storage, and on cloudy days you will need storage. But you will need much less of it.”
California has set a target of 60% renewable energy on the power grid by 2030, as well as a longer-term goal of 100% climate-friendly energy, a broader definition that could include hydroelectricity or nuclear power. A dozen other states and U.S. territories have adopted or are considering similar 100% clean energy goals, and they’ll be watching California’s progress as they try to figure out how to make those goals a reality.
The Golden State’s success depends in part on achieving its goals without sending energy prices soaring. California already has some of the country’s highest electricity rates, although low levels of energy use mean monthly bills are relatively low.
Perez and Rábago coauthored their study with analysts at Clean Power Research, a company with offices in California and Washington state. The study built on an earlier Clean Power Research report, which showed that in Minnesota — a state not known for abundant sunlight — the cheapest way to run the power grid with solar panels, wind turbines and batteries involved building so many solar panels that their output would have to be “curtailed,” or reduced below what they’d otherwise be capable of producing, by around 30%.
Under a range of high-curtailment scenarios, the report found, electricity would be slightly cheaper than it is today in Minnesota — a conclusion that Perez and Rábago found to hold true for many power grids.