The coronavirus pandemic brought the broader economy to a halt, but the energy storage industry didn’t get the memo.

Instead, developers made this year the biggest ever for battery installations in the U.S. More capacity is going into homes than ever before, helping families make better use of rooftop solar investments and keeping the lights on during outages. Large-scale projects reached new heights, including LS Power’s completion of the largest battery in the world, just in time to help California grapple with its summer power shortage.

Just a few years ago, energy storage was a niche item, something people built in the very few locations where a higher force compelled it. Now, utilities across the country are using batteries to solve numerous grid problems and planning far more for the near future. And the most boisterous of power markets, Texas, has finally broken open for storage developers, with major projects already underway.

Here is an attempt at condensing all of these upheavals and breakthroughs into a list of the crucial energy storage storylines from the year. Think of it as a cheat sheet for all things energy storage in 2020.

Deployment like never before

2020 will certainly go down as the biggest ever for the U.S. grid storage industry. The annual market for grid batteries passed the $1 billion mark and the 1-gigawatt threshold for the first time ever, per the latest Energy Storage Monitor report from Wood Mackenzie. Overall capacity installations doubled compared to 2019, a growth rate that you won’t see in any other kind of energy infrastructure right now.

In practical terms, this means more battery capacity is storing solar production that might otherwise go to waste. More battery peaker plants are discharging during times of extreme demand, without unleashing local pollutants into their surroundings, as the gas-burning alternatives do.

The rapid growth of wind and solar power comes with a well-known problem: They don’t work all the time. Energy storage is a solution investors should watch in 2021, even if it doesn’t yet lend itself to stock picking.

Governments around the world greatly raised their decarbonization ambitions this year. There is great uncertainty about how their promises will be delivered, but almost all scenarios involve massive building of solar and wind farms. As their share of power production grows, it will become crucial to bridge the times when the wind doesn’t blow and the sun doesn’t shine.

Building wind and solar together can reduce the gaps, while gas-fueled power plants can provide a nonrenewable backup. Also helpful are demand-side response agreements—when big power consumers promise to cut their usage during pinch points in exchange for lower prices.

Even with all these methods, though, it will be necessary to store excess electricity for use in lean times.

Lithium-ion batteries similar to those that power an electric vehicle are expected to provide most of the new storage capacity. Residential batteries can store power from rooftop solar panels, but it is so-called utility-scale stationary solutions for wind and solar farms that are really needed. They are often customized turnkey installations that provide between one to four hours of backup power. Battery packs cost nearly 90% less than in 2010 and will continue to get cheaper, according to researchers at BloombergNEF.

The coronavirus pandemic brought the broader economy to a halt, but the energy storage industry didn’t get the memo.

Instead, developers made this year the biggest ever for battery installations in the U.S. More capacity is going into homes than ever before, helping families make better use of rooftop solar investments and keeping the lights on during outages. Large-scale projects reached new heights, including LS Power’s completion of the largest battery in the world, just in time to help California grapple with its summer power shortage.

Just a few years ago, energy storage was a niche item, something people built in the very few locations where a higher force compelled it. Now, utilities across the country are using batteries to solve numerous grid problems, and planning far more for the near future. And the most boisterous of power markets, Texas, has finally broken open for storage developers, with major projects already underway.

Here is an attempt at condensing all of these upheavals and breakthroughs into a list of the crucial energy storage storylines from the year. Think of it as a cheat-sheet for all things energy storage in 2020.

Deployment like never before

2020 will certainly go down as the biggest ever for the U.S. grid storage industry. The annual market for grid batteries passed the $1 billion mark and the 1 gigawatt threshold for the first time ever, per the latest Energy Storage Monitor report. Overall capacity installations doubled compared to 2019, a growth rate that you won’t see in any other kind of energy infrastructure right now.

With increased use of rechargeable batteries to power modern technology, particularly electric vehicles, researchers have been looking for alternative materials for lithium-ion in rechargeable batteries. Modern batteries use lithium and cobalt, but these have a very limited supply.

Interestingly, the fluoride ion is the mirror opposite of the lithium ion, having the strongest attraction for electrons, which allows it to easily carry out electrochemical reactions.

Researchers in Japan are also testing fluoride-ion batteries as possible replacements for lithium-ion batteries in vehicles. They say these batteries could allow electric vehicles to run 1,000 kilometers (621 miles) on a single charge. However, current fluoride-ion batteries have poor cyclability, which means they tend to degrade rapidly with charge-discharge cycles.

In their new work, the researchers adopted a different approach to fluoride-ion battery design, identifying two materials that easily gain or lose fluoride ions while undergoing small structural changes to enable good cyclability.

The new battery materials are both layered electrides, says Rohan Mishra, assistant professor of mechanical engineering and materials science at Washington University in St. Louis.

Electrides are a relatively new class of materials that researchers have known about in principle for about 50 years, but it wasn’t until the past 10 to 15 years that their properties were better understood, Mishra says.

While these materials conduct electrons like ordinary metals, unlike the “sea of electrons” in metals where the electrons are delocalized throughout the crystal, in electrides, the electrons reside at specific interstitial sites within the crystal structure, similar to an ion.

“We predict that these interstitial electrons can be easily replaced with fluoride ions without significant deformations to the crystal structure, thus enabling cyclability,” Mishra says. “The fluoride ions can also move or diffuse fairly easily due to the relatively open structure of the layered electrides.”