Storage is everywhere. Your gas tank stores fuel for your car. Your fridge and the supermarket store food. Your bank and wallet store money. Dams and water towers store water. Your computer stores photos, documents, and other data. Grocery stores, and other retail stores, store merchandise waiting for consumers.
Imagine a world without storage. You’d have to glean food directly from the fields. You’d drink from the stream. Your car would need a hose running all the way to an oil field. We depend on storage for daily life in the modern world.
And yet, the electric power grid has no storage. For over 100 years, the grid generates power for immediate consumption. Any excess is lost, and any shortage results in a brownout. The electric utility industry devotes great resources to forecasting how much power to generate, on an hourly basis, to match expected demand, and to adjust quickly when the actual demand doesn’t match the forecast. Electric power is one of the most perishable commodities in the world.
Gas, oil, and coal are all easily transported and stored. They can be burned to generate heat or electricity. The current power grid depends on burning these fossil fuels to meet demand when the sun isn’t shining and the wind isn’t blowing.
You hear cities and companies commit to using 100% renewable power. These consumers feel great about going green, but it’s the wrong kind of green. These 100% figures are about dollars, not electrons. 100% of the money they spend for power goes to renewable power providers. Yet when they need to turn on a light at 4 AM, the electricity going through that lamp comes from the nearest source on the grid: the local fossil fuel plant. Money from somewhere else pays for that power. It’s all a shell game, shuffling power contracts around to make the numbers look good. The hope is that the more money goes to renewable power providers, the more will be built. But it can never reach 100% without a way to store the power to get through the night or a rainy day.
Some electric storage exists today. Hydroelectric power generation stores water behind a huge dam, releasing the water as needed to generate perishable power. Some parts of the country, notably Washington and Tennessee, have a network of dams used to power their portions of the grid. This depends on an ample supply of water and investment in dam building. It will never scale up in areas where water is scarce, like the southwest.
Research into electric storage is a hot area today. Batteries can store power on a small scale. A Tesla Power Wall, storing 13.5 KiloWatt Hours (KWh) of power, would provide about half the 29KWh average power need of an American home. That might be enough to get through the night on a sunny day, but it could not handle a rainy week.
Scaling up batteries to utility scale is not easy. SDG&E’s system load ranges from 2000 MegaWatt (that’s 2 million KW) in the wee hours of the night to 4500 MW on a hot summer day. A 15 hour winter night with no solar or wind generation would require 30 to 50 million KWh, or 3 million Power Walls.
In 2017, SDG&E opened what was at the time the world’s largest battery storage facility. Made up of 20,000 battery cells, of the same type used in BMW electric vehicles, this giant battery fills 24 truck-trailer sized shipping containers covering about an acre of land. This giant battery can store 120,000 KWh. This is enough to provide 30 MW of power for 4 hours. We would need about 400 of these sites to get San Diego’s through one winter night between two sunny days.
And this does not take into account gas and oil used to heat our homes, our water heaters, and cook our dinners. Electric heat is far less efficient than gas. In a snowy climate, you need a lot of gas to run the furnaces. If all that is converted to electric heat, the power storage need will skyrocket.
We have a lot of R&D to do to get the power grid to a true 100% renewable condition. We need to fund that R&D to get us to a point where business interests will support 100% renewable energy.