One startup to watch in the infrastructure space is Austin-based Accelsius, which said this morning that it raised $65 million to scale its data center cooling technology. The round was led by strategic investor Johnson Controls, with participation from electrical giant Legrand. A person familiar with the deal said it valued Accelsius at more than $600 million.
Accelsius is part of a growing class of liquid-cooling startups trying to keep AI data centers power-efficient as chip temperatures rise. CEO Josh Claman told me operators are increasingly worried about how much of their power budget gets eaten up just keeping servers from burning up.
The company takes a different approach from today’s dominant liquid-cooling method, which involves pumping water over cold plates attached to servers. Operators have gravitated to water because it’s conceptually simple, Claman said—but it’s becoming riskier as racks get hotter. Removing more heat requires pumping water faster, which raises the chances of leaks and accelerates wear on equipment. In some cases the water gets so hot that it has to be cooled with power-hungry chillers.
Accelsius instead uses a refrigerant that enables two-phase cooling, where the coolant changes from liquid to vapor as it absorbs heat from a GPU. The phase changes soaks up heat, so the system can cool increasingly hot racks without requiring colder water—making it a potentially more efficient way to cool AI infrastructure.
That matters because as racks get hotter, the water used to cool them heats up too. Many operators have responded by installing chillers to cool water, but chillers can consume a significant share of a data center’s total power.
At CES last week, Nvidia CEO Jensen Huang said the company’s next-generation AI chips, known as Vera Rubin, wouldn’t require power-hungry chillers. The comment rattled investors, sending shares of several data-center cooling suppliers, including Johnson Controls, lower.
But Claman said his phone lit up after the remarks, largely because they reinforced a point he’s been making for years: two-phase cooling allows data centers to operate with warmer water, reducing reliance on chillers.
“I think what Jensen was trying to get across was, ‘We’ve engineered this to be efficient,’” Claman said. “If you’re not using it efficiently, that’s kind of your problem.”
