Report from KOVR CBS 13, Sacramento.
Mark Jacobson of Stanford interviewed on the remarkable run of more-than-100 percent renewable energy in California. Sure, it’s spring, demand is not as high as it will be in August, but this is exactly where you would expect to see the earliest big results.
But now, the state and its grid operator are grappling with a strange reality: There is so much solar on the grid that, on sunny spring days when there’s not as much demand, electricity prices go negative. Gigawatts of solar are “curtailed” — essentially, thrown away.
In response, California has cut back incentives for rooftop solar and slowed the pace of installing panels. But the diminishing economic returns may slow the development of solar in a state that has tried to move to renewable energy. And as other states build more and more solar plants of their own, they may soon face the same problems.
“These are not insurmountable challenges,” said Michelle Davis, head of global solar at the energy research and consulting firm Wood Mackenzie Power and Renewables. “But they are challenges that a lot of grid operators have never had to deal with.”
Solar power has many wonderful properties — once built, it costs almost nothing to run; it produces no air pollution and generates energy without burning fossil fuels. But it also has one major, obvious drawback: The sun doesn’t shine all the time.
Over 15 years ago, researchers at the National Renewable Energy Laboratory were in the midst of modeling a future with widespread solar power when they noticed something strange. With lots of solar power on a given electricity grid, the net load — or the demand for electricity minus the renewable energy — would take on a “U” shape. Sky-high demand in the morning would be replaced by almost zero demand in the middle of the day, when solar power could generate virtually all electricity people needed. Then as the sun set, demand surged up again.
California’s grid operator, known as CAISO, later dubbed this effect the “duck curve.” (If you squint, you can imagine the curve as the belly of a duck.) It’s most prominent in the spring months, when solar panels get plenty of sunshine but there is less demand for heating and cooling.
In recent years in California, the duck curve has become a massive, deep canyon — and solar power is going unused. In 2022, the state wasted 2.4 million megawatt-hours of electricity, 95 percent of which was solar. (That’s roughly 1 percent of the state’s overall power generation in a year, or 5 percent of its solar generation.) Last year, the state did that in just the first eight months.
Clyde Loutan, principal for renewable energy integration at CAISO, says that the state has long been prepared for more solar on the grid. But, he added, “We drastically underestimated the speed at which residential solar was going to come in.”
Curtailing solar isn’t technically difficult — according to Paul Denholm, senior research fellow at the National Renewable Energy Laboratory, it’s equivalent to flipping a switch for grid operators. But throwing away free power raises electricity prices.
It has also undercut the benefits of installing rooftop solar. Since the 1990s, California has been paying owners of rooftop solar panels when they export their energy to the grid. That meant that rooftop solar owners got $0.20 to $0.30 for each kilowatt-hour of electricity that they dispatched.
But a year ago, the state changed this system, known as “net-metering,” and now only compensates solar panel owners for how much their power is worth to the grid. In the spring, when the duck curve is deepest, that number can dip close to zero. Customers can get more money back if they install batteries and provide power to the grid in the early evening or morning.
–
Other states, which have been slower to adopt solar, are starting to experience the same thing. Nevada, which generates 23 percent of its power from solar, has also seen deepening duck curves. Hawaii, which has thousands of homes with rooftop solar, has cut down on the payments those households get from the grid.
Beyond the sunny West, many states are still trying to ramp up rooftop solar power and extend its reach beyond affluent households. The Biden administration announced $7 billion in grants this week to provide rooftop solar to 900,000 low-income households.
California grid operators hope that their experience will teach other states what to expect as renewables grow. “The problem we’re seeing out West — nobody else has seen this,” Loutan said.
Storage & transmission are the answers, time-shifting & space-shifting energy (which because of time zones turns out to be time-shifting too). Zero curtailment.
It was nuclear power plants’ straight-line supply, day and night, that was a problem before, because NPPs couldn’t just be shut down every night, and it was more cost-effective to have it running all of the time to pay for its capital investment. That was the impetus for pumped-hydro storage, to time-shift the energy supply to when it was needed.
Fortunately, we have more “dry” storage coming online in the form of longer-term battery chemistries, for those many areas that don’t have a reliable water supply, to time-shift the solar energy supply to when it is in demand.
Over the last month, a whopping 0.5% of California’s power was stored in grid-scale batteries. Enough to help for a few hours in the evening, but not anything like the seasonal storage a 100% Wind Water Solar, all energy system would need. Professor Jacobson is given to claiming that seven countries have ‘100% WWS electricity’ – but all of them get the vast majority of their power from dams, power sources which NGOs like the Sierra Club, the National Resources Defense Council, and Riverkeeper used to fight against tooth and nail, when they were being built. Also, those countries are all either poor, with very low electricity usage, or underpopulated, like Iceland.
The same NGOs also had a hand in the closure of reactors like Indian Point, in New York, San Onofre, in California, and very nearly Diablo Canyon, now California’s largest single power source.
If you want a good example for emissions in North America, Ontario’s carbon intensity per watt was less than a third of California’s over the last year, and its worst month was still much better than California’s best month. That despite the share of nuclear in the Province’s power dropping from 60% to only 52% over the last few years, and emissions going up as a result, from 43 to 76 grams CO2 per kWh. (California’s figure for 2023 was 262 g/kWh, nearly the same as for the last five years.) The good news from Ontario is that the government there has committed to refurbishing some of its older reactors, and building new ones. @ElectricityMaps.com
Nuclear plants would be much better for charging all these new fangled grid batteries. You don’t have to worry about calm nights and cloudy days plus with all that generation concentrated on one compact sight(s), transmission infrastructure is simpler and more optimally utilized.