A mountain, a tower, a thermos of molten salt. These are the batteries that could power our renewable future.

Climate change is pushing the power grid to the limit. Energy storage could help.

Blackouts are a devastating reality of our climate-changed world. An unprecedented winter storm in 2021 knocked out power for millions of Texans for days, killing hundreds, and this summer Californians managed to barely save their state’s power grid from the brink of collapse during a record-breaking heat wave.

Some blackouts are caused by storms destroying infrastructure like transmission lines and substations — just look at what’s happened in Puerto Rico after Hurricanes Maria and, more recently, Fiona.

But many blackouts can also be blamed on how the electric system works. Namely: The goal of the power grid is to deliver electricity to your home as soon as it’s been generated at a power plant. There isn’t a great pool of electricity waiting in reserve for when demand spikes. Experts say that needs to change.

“Electricity systems are real-time systems,” said Eric Fournier, research director at UCLA’s Institute of the Environment and Sustainability. There’s little room for error.

In the past, there was an easy fix. If grid operators ever needed more power, they’d just burn more fossil fuels, in real time, to meet demand. But that makes climate change worse (electricity generation is responsible for 25 percent of total greenhouse gas emissions in the United States). It’s a vicious cycle: Climate change is what’s pushing our grids to the limit.

Switching to clean energy is the obvious solution. But while wind and solar power are efficient, they’re not always available: Solar power turns off at night, and wind turbines can’t generate power on a still day. With renewables, demand can still outpace supply.

We need a way to store renewable electricity. That sounds like … a battery. But batteries — at least the kind found in our cellphones and cars — aren’t necessarily the best solution. Lithium-ion batteries, which have become the de facto standard for rechargeable batteries and are used in everything from phones and laptops to electric cars, are expensive to produce and might be better suited for those portable applications than sitting static in storage racks.

“We need to think about solutions that go beyond conventional lithium-ion batteries,” said Dharik Mallapragada, a principal research scientist at the MIT Energy Initiative and co-author of a recent study on the future of energy storage. Money is on everybody’s mind at COP27, the UN climate negotiations currently underway in Egypt, and the world needs affordable solutions that can work for wealthy and poor countries alike.

“No single technology is going to make this happen,” Mallapragada said. “We have to think about it as a jigsaw puzzle, where every piece plays its role in the system.”

The power grid is a massive machine. To make a battery for it, we have to think big — and weird. On this week’s episode of Unexplainable, Vox’s podcast about unanswered questions, we explore what the future batteries of the grid might look like, from the time-tested to the fantastical. There are many ways to bottle lightning.

On a very basic level, all batteries work by taking electricity, storing it as a different form of energy, and turning that energy back into electricity (or, to be extremely technical, electric energy) when it’s needed again.

Lithium-ion batteries are chemical batteries, which means they store electricity as chemical energy. They’re very efficient; they can generally release upward of 90 percent of the energy put into them.

But a battery doesn’t have to be based on chemical energy — there are all kinds of other energy types we can convert that electricity into. Take, for example, pumped hydro.

Pumped-storage hydropower, or pumped hydro, is the biggest kind of grid-storage battery currently in operation in the United States. It’s also the oldest; the first pumped hydro facility in the country opened in New Milford, Connecticut, in 1930.

The concept behind pumped hydro is pretty straightforward. Sometimes power plants — especially renewable power plants like wind — generate more electricity than we can use, and grid operators end up having to simply dump that energy in a process called “curtailment.”

But if those renewable power facilities were hooked up to pumped hydro, that excess energy could be used to pump water up a hill or mountain and fill a reservoir. That movement uphill raises the water’s potential energy; when the energy is needed, the water is released and sent through a hydroelectric turbine, turning the potential energy back into electricity.

Pumped hydro took off in the United States during the 1970s and ’80s when the country saw a boom in nuclear power. Nuclear plants were very good at constantly generating a steady amount of electricity around the clock, Mallapragada said, but there wasn’t an easy way to increase or decrease their output.

To be able to respond to fluctuating demand, grid operators built pumped-hydro stations to store the excess energy generated by nuclear power plants during times of low energy use; without pumped hydro, that energy could have gone to waste. (It’s a similar dilemma to the one faced by solar and wind power plants, and recently some pumped-hydro stations have seen their energy sources shift from nuclear energy to renewables.).Read More…