By Katarina Zimmer
Solving the variability problem of solar and wind energy requires reimagining how to power our world, moving from a grid where fossil fuel plants are turned on and off in step with energy needs to one that converts fluctuating energy sources into a continuous power supply. The solution lies, of course, in storing energy when it’s abundant so it’s available for use during lean times.
But the increasingly popular electricity-storage devices today — lithium-ion batteries — are only cost-effective in bridging daily fluctuations in sun and wind, not multiday doldrums. And a decades-old method that stores electricity by pumping water uphill and recouping the energy when it flows back down through a turbine generator typically works only in mountainous terrain. The more solar and wind plants the world installs to wean grids off fossil fuels, the more urgently it needs mature, cost-effective technologies that can cover many locations and store energy for at least eight hours and up to weeks at a time.
Engineers around the world are busy developing those technologies — from newer kinds of batteries to systems that harness air pressure, spinning wheels, heat or chemicals like hydrogen. It’s unclear what will end up sticking.
“The creative part … is happening now,” says Eric Hittinger, an expert on energy policy and markets at Rochester Institute of Technology who coauthored a 2020 deep dive in the Annual Review of Environment and Resources on the benefits and costs of energy storage systems. “A lot of it is going to get winnowed down as front-runners start to show themselves.”
Finding viable storage solutions will help to shape the overall course of the energy transition in the many countries striving to cut carbon emissions in the coming decades, as well as determine the costs of going renewable — a much-debated issue among experts. Some predictions imply that weaning the grid off fossil fuels will invariably save money, thanks to declining costs of solar panels and wind turbines, but those projections don’t include energy storage costs.
Other experts stress the need to do more than build out new storage, like tweaking humanity’s electricity demand. In general, “we have to be very thoughtful about how we design the grid of the future,” says materials scientist and engineer Shirley Meng of the University of Chicago.