Keeping the Lights On, 24×7

As EBCE relies more on solar and wind energy, how do we still provide round-the-clock power?

Photo by _Eazie_, Flickr CC

With a steady stream of new contracts, EBCE’s share of power from new renewable power projects is rising. Many of these are from wind and solar power plants, cutting our carbon footprint and helping California achieve climate goals.

But as the share from wind and solar go up, the question often comes up — how does EBCE keep the lights on when the sun doesn’t shine and the wind doesn’t blow?

The main course: solar and wind

EBCE’s power generation portfolio is a mix of resources. As of 2021, solar, wind, and hydroelectric accounted for 64 percent of our mix. EBCE has so far signed 12 contracts for 740 megawatts (MW) of renewables and 274 MW of battery storage, with five operating so far.

Wind and solar have the benefit of being zero emission, low cost, and relatively quick to deploy. This has made them the most rapidly growing generation resource in countries around the world. In 2021, they accounted for 77 percent of new capacity in the United States.

Expert models predict that solar and wind will dominate future growth, especially as states and countries get increasingly serious about fighting climate change. The US Energy Information Administration, the data and forecasting arm of the Department of Energy, sees wind and solar tripling to 36 percent of total supply by 2050 in a “business as usual” scenario, which includes only current policies.

With the right policies we can see much higher levels. A study by the Goldman School at UC Berkeley found that a scenario of 90 percent clean power by 2035, including about 40 percent solar and 30 percent wind, could be achieved at a cost comparable to today’s electricity prices, while cutting US carbon emissions by 1200 million tons per year.

EBCE has already committed to a zero-carbon power supply by 2030, a full 15 years faster than state law requires. Other community choice energy providers in California are making similar pledges, as are many corporations. It’s clear that much more solar and wind will be built in and near California in the coming decade.

The Portfolio

But wind and solar power are, of course, variable. They rise and fall with the sun and the wind, which may or may not align with power demand on any given day. And EBCE, of course, keeps the power on around the clock to make sure it is available when needed.

So how does EBCE provide 24×7 power now, and how will it in an increasingly low carbon future?

EBCE uses a mix of resources and procurement mechanisms intended to meet demand, manage risk, keep costs low, and achieve emissions goals.

EBCE has a variety of strategies for buying power. Long term contracts lock in a certain quantity of energy at certain times of day and year, based on a forecast of when power will be needed. EBCE analysts have been improving the accuracy of near-term forecasting, using better weather data and machine learning techniques.

Still, even good forecasts are usually only accurate within about three percent of actual demand. Short term transactions are used to fill in the gaps in long term contracts or make up the difference between forecasts and what actually happens in real time.

California runs short term markets for day-ahead and real-time transactions, with balancing happening every five to fifteen minutes. These last minute prices can be quite volatile and much higher.

Long term contracts provide predictability and a lower price, while short term deals meet last minute needs. Think of it as buying bulk groceries on the monthly trip to Costco, but running down to the corner store if the milk runs out.

EBCE has long-term contracts for specific renewable generators to bring new resources online and ensure that environmental goals are being met. But since the resources are variable, they may or may not be able to deliver at a certain time in the future.

“Let’s say EBCE buys output from a wind farm,” says Jim Dorrance, EBCE’s Power Resources Manager. “We don’t know when the exact output will happen. It’s not guaranteed on a daily or even monthly level, but is over a year or two-year period.”

The wind generator sells their output into the short term market run by CAISO and gets paid the current price. They earn renewable energy certificates from the state verifying their generation, which they deliver to EBCE.

EBCE also has contracts for energy delivered at a certain time and price, one to five years in the future. Rather than contracting with a specific power plant, these contracts are with power marketers who use sophisticated methods to predict future prices. These contracts ensure precise delivery, but insulate EBCE from the volatility of daily power markets, putting the risk on the power marketer.

“The actual energy source depends on grid mix at the time of demand,” says Dorrance. “It could be solar in the day, and hydro or something else at night. It isn’t really possible to track it by time and location, so it gets called ‘unspecified’ power.”

EBCE’s Power Content Label is an annual “mathematical exercise” that accounts for long term contracts, specific power purchases, and the mix of unspecified power, says Dorrance. “What happens on a daily basis is up to the CAISO market and the wind and the sun.”

Clean firm

EBCE is not alone in managing variable generation. The state utility commission recently ordered power suppliers to start developing 11,500 MW of “clean firm” power, that is, generation sources that are zero emission but also can deliver power when called upon, any time of day.

In response, EBCE signed an agreement with Fervo Energy for 40 MW of capacity from a new geothermal plant in Nevada, to come online in 2026.

More clean firm resources are out there, and the use of energy storage will continue to grow. Energy demand itself is a growing source of flexibility, as “smart” appliances and thermostats are increasingly able to respond to market prices and signals from grid operators. As vehicles and buildings go electric, there will be even more demand available to provide flexibility. Electric cars, especially, can both charge and discharge as needed to help the grid.

So while wind and solar are the stars of the clean energy transition, there will be many other supporting roles for generation, storage, and flexible demand. It will take a team effort to keep the lights on 24×7 — just as it does now.