These days we may be distracted by the COVID-19 virus, but climate issues move on. Recently, Wired magazine published an article about big batteries, or more precisely linked battery packs located in enormous battery farms. They will be needed if we want to generate energy from sources that emit no carbon dioxide.
Batteries store energy. They can be small—like the one inside your cell phone. But when it comes to storing solar or wind energy—sources that produce electricity intermittently—they must be huge. The batteries store the energy that these somewhat unreliable sources of energy produce so it can be used when needed.
Wired cites the example of San Diego Gas & Electric, the state’s third-largest private utility, which installed a pair of batteries that can store enough energy to power just 1,000 homes for four hours. Think about it. To power just 1,000 homes for four hours, each battery “consists of five shipping containers’ worth of equipment, eight 10,000-gallon tanks of electrolyte solution (the stuff that holds the charge), and a maze of wires, pumps, switches, and PVC piping. They sit in corrosion-resistant concrete safety pits that are large enough, in case of a leak, to hold all 80,000 gallons of electrolyte plus all the water from the county’s worst day of rain in the past 100 years. Rain! Being in California, I want to know if they are safe from cracking during earthquakes, or how they might be affected by wildfires or mudslides?
Since that is what it takes to provide back-up to just 1000 homes for four hours, what size battery would be required to ensure power during days-long or even weeks-long periods of limited or no sun or wind, and during 12 hours of nightly darkness for the city’s millions of people? Now multiply that by the needs of 328 million Americans, or more than 7 billion people on earth, we’re talking continent-sized battery facilities.
It’s a Matter of Physics
In truth, as explained by Mark Mills in a recent study, “The ‘New Energy Economy’: An Exercise in Magical Thinking,” physics itself indicates entire arrays of “very big batteries” (as Wired puts it) can’t provide the reliable energy needed for reliable electric power for more than exceedingly short periods of time.
Mills points out:
- For security and reliability, an average of two months of national demand for hydrocarbons are in storage at any time. Today, barely two hours of national electricity demand can be stored in all utility-scale batteries plus all batteries in one million electric cars in America.
- Batteries produced annually by the Tesla Gigafactory (the world’s biggest battery factory) can store three minutes’ worth of annual U.S. electric demand.
- To make enough batteries to store two days’ worth of U.S. electricity demand would require 1,000 years of production by the Gigafactory.
So, the physics behind Wired’s suggestion of very big batteries doesn’t work.
Batteries, Economics and the Environment
Physics aside, even if it were possible to bring enough battery storage online to reach zero carbon dioxide emissions from the electric power sector by 2050, it would be a disaster from the perspective of the economy and the environment. Battery storage is by far the most expensive form of electric power.
- It costs less than 50 cents to store a barrel of oil, or its equivalent in natural gas, but it costs $200 to store the equivalent energy of a barrel of oil in batteries.
- About 60 pounds of batteries are needed to store the energy equivalent of one pound of hydrocarbons. At least 100 pounds of materials are mined, moved and processed for every pound of battery fabricated.
- Carrying the energy equivalent of the aviation fuel used by an aircraft flying to Asia would require $60 million worth of Tesla-type batteries weighing five times more than that aircraft.
- It takes the energy-equivalent of 100 barrels of oil to fabricate a quantity of batteries that can store the energy equivalent of a single barrel of oil.
Indeed, a recent study by the U.S. National Renewable Energy Laboratory (NREL) found in 2030 the overall capital cost—not including variable operation, maintenance, and replacement costs—for a 4-hour battery storage system would provide electricity for between $124 per kilowatt hour (kWh) and $338/kWh. By 2050, this might fall to between $76/kWh and $258/kWh.
By comparison, coal power (even the most expensive kind) costs $104/mWh. That’s megawatt hours, not kilowatt hours. (One megawatt equals 1,000 kilowatts.) Advanced combined cycle gas plants cost about $41/mWh, wind approximately $56 /mWh (onshore) and $118 /mWh (offshore), and solar $60 mWh (roof top), and $157 mWh (thermal plant).
In conclusion, it is not possible in the near future to count on batteries to back up much of the renewable power being added to the electric grid as a result of government mandates and incentives in the United States and abroad. Instead, natural gas and coal plants provide the vast majority of back-up for intermittent renewable power. Batteries may work well in your phones, kindles, and laptops (except when they are catching fire), but they are a poor source for utility-scale power.