Cache Energy installed a thermal battery at University of Minnesota Morris to convert excess wind power into heat, potentially cutting the campus's reliance on natural gas. The campus, which has operated on wind since 1999 and added a second turbine in 2011, now produces 10 million kilowatt-hours of electricity annually, more than it consumes, and sells the surplus to Otter Tail Power Co. The new battery, capable of 1,000 degrees Fahrenheit, could store that surplus for use in the campus's steam-heat loops. The battery unit, housed in a shipping container, was installed in March 2024 and has been running continuously since March 24. Cache's pellets, derived from limestone and coated with a proprietary binder, are designed to last over 30 years. Technicians from Illinois-based Cache Energy arrived on campus to install the unit. Troy Goodnough, the school's sustainability director, noted, "It's windy year-round here in western Minnesota." He added that the "warehouse-like" shop has high ceilings and several thousand square feet of floor space. According to Goodnough, the battery unit transforms electricity into intense heat. Its outlet temperature can reach 1,000 degrees Fahrenheit — more than hot enough to efficiently run a steam heating system. It took two hours to position the shipping container that houses the unit next to the school's carpentry shop, and then another few hours to connect the unit to the building's electrical and duct systems. It powered up on March 24 and hasn't stopped providing heat since, Goodnough said. Its task is not small, he added: The "warehouse-like" shop has high ceilings and several thousand square feet of floor space. "The cool thing is it's doing what it's supposed to be doing," he said. "It's working great." The battery unit contains limestone-derived pellets coated in a proprietary binder that keeps them intact throughout their 30-plus-year operating life, according to Cache. When exposed to a stream of moist air, the pellets get so hot they "can be used to make hot air or even vaporize water to make steam," Goodnough wrote last month. To recharge, the system uses electricity to dry out (and cool down) the pellets. Arpit Dwivedi, Cache's founder and CEO, said low-cost electricity helps make the economic case for customers to invest in thermal batteries rather than stick with equipment that runs on natural gas, which is also plentiful in the United States' midsection. "We know gas is cheap," he said, and that's a problem for tech developers looking to electrify heat. Another issue for big energy users, like UMN Morris, is that switching from gas to electric heat means replacing massive, long-lived boilers — likely fully paid for — with new equipment that needs to be leased or financed. That shift is necessary if the university is going to meet its aggressive climate goals of reducing greenhouse gas emissions by 87% by 2035 and reaching carbon neutrality by 2050, but it could incur a considerable balance-sheet burden. So from the outset, Dwivedi and his team were intent on reducing Cache units' upfront cost, he noted. "We knew that if we did not have a low-capex system, we would not have an economic advantage," he said. Like other emerging thermal battery designs, Cache's uses low-cost — if heavy — materials that are widely available in the United States. The primary inputs are steel, lime, and water, all of which Cache sources domestically, Dwivedi said. The proprietary binder that keeps the lime granules stable is by far the most expensive input, so the company focused on keeping that cost in check. Its secret ingredients are available domestically, too, Dwivedi added. Cache offers its battery as a lease product that it says bundles the battery unit, delivery, installation, maintenance, guaranteed uptime, and takedown "without capital burden." Just as an automaker leases a passenger vehicle, Cache retains ownership of the battery unit during the lease term, after which the customer has the option to buy it or send it back. Cache launched in 2022. For its first few years, space heating was a sideshow. Dwivedi and his team were more focused on the technology's potential to electrify low- and medium-temperature process heat for food, chemicals, and other types of industrial production. To that end, Cache recently conducted a pilot at a Duke Energy testing facility in North Carolina that "[hosts] several interested industrial companies," the company said last month in a news release. Cache still works on industrial heat, but it's also leaning into relationships with large space heating customers, particularly those with existing hot-water or steam infrastructure such as UMN Morris. That includes the U.S. Army, which is interested in the thermal battery's ability to provide reliable backup for military installations at risk of extended power outages. Cache was one of nine finalists in a demonstration cohort fielded last year by Grid Catalyst, a Minnesota-based clean energy acc