From 2pm to 6pm on summer weekdays, energy providers face a big problem: Far more people use electricity at those times than at any other point during the year. That period — when homes and offices are using power at the same time, and air conditioners are blasting — is what New York utility company Con Edison refers to as ‘super peak’ because of the stress it puts on the electricity grid.

As the populations of cities grow and people start using electricity in new ways (like to charge electric cars), it's becoming increasingly hard for providers like Con Edison to keep up with demand. But a new energy storage system helps one type of energy consumer — grocery stores — become more flexible about when they use energy, giving Con Edison a break in the process.

A three-year-old company called Axiom Exergy makes a battery that stores thermal energy rather than electricity, in the form of frozen saltwater. At night, when there is less stress on the electricity grid, Axiom’s system uses energy to freeze tanks of saltwater. Then, during peak hours, that frozen water can keep refrigerators cold, eliminating the need to use electricity for cooling. The system can be controlled from anywhere.

“It doesn't make sense to have these enormously power hungry systems just running at a flat constant rate all the time,” Amrit Robbins, Axiom Exergy’s president and cofounder, tells Business Insider. “Supermarkets spend about 55% of all energy they consume to create cold, so rather than storing energy or electricity, we just store cold directly for later use.”

A rendering of Axiom's energy storage system Axiom Energy

Axiom’s technology doesn’t reduce the overall energy usage of a given store — it just changes when that energy is used. But providing grocery stores flexibility about when they consume electricity can lead to enormous savings on their energy bills. Utility providers often offer customers billing plans that charge more for power consumed during peak and super-peak hours, and give much cheaper rates for energy consumed at night.

Robbins estimates that Axiom’s batteries will lower grocery stores’ overall energy demand by 40% during those expensive peak hours. That saves them lots of money, and also helps Con Ed ensure that it can continue to provide power during peak hours without the risk of blackouts.

As part of a new initiative by Con Ed, Axiom will install its energy storage systems in 20 to 25 grocery stores throughout the two boroughs. The installation won’t cost the grocery stores anything up front — the system will pay for itself in energy bill savings, and some of that money will go to Axiom.

Robbins says Axiom’s technology has the potential to do much more than lower grocery stores’ energy bills.

The technology could eventually be installed in homes or apartment buildings with central air conditioning — a much bigger market than refrigeration. That would allow landlords and homeowners more flexibility in their energy use. And since the ice batteries can provide cooling for up to 6 hours, they can also act as a kind of back-up generator to keep refrigerators running if electricity goes out during an emergency. Most importantly, Robbins says, figuring out new solutions for energy storage can help utility companies increase the amount of power they use from renewable sources. Flickr / Matthew Rutledge

“The bottom line here is that if you can get a lot of energy storage on the grid, and you have some buffer and some flexibility in the grid, that enables you to add a lot of additional intermittent renewables like solar and wind to the grid without causing blackouts,” Robbins explains.

The Brooklyn/Queens project will be the first time that Axiom brings its technology to market, though the California-based company has two other initiatives planned in its home state as well. Robbins is convinced that technologies like Axiom’s will be utilized more and more in the future.

“Utilities are moving away from making bigger substations and power plants to meet this ever-changing load that the population has, and moving toward much more intelligent, cloud-connected sets of assets that can be turned on and off as necessary,” he says. “We’re in the right place at the right time.”