Making the Cloud Greener
Rice engineers are turning the wasted heat of data centers into renewable energy.
By Alex Becker
Step inside a data center — the unseen heart powering our digital lives — and you’ll find racks of humming servers, glowing LEDs and a palpable tide of heat. Every time you stream a movie, back up a photo or ask ChatGPT a question, those machines work hard — and get hot. Cooling them consumes a staggering amount of energy, nearly half of which dissipates as waste heat.
A new Rice study offers a compelling method to reclaim this electricity, while also reducing costs.
“There’s an invisible river of warm air flowing out of data centers,” says Laura Schaefer, the Burton J. and Ann M. McMurtry Chair of Mechanical Engineering at Rice and co-author of the study. “Our question was: Can we nudge that heat to a slightly higher temperature with sunlight and convert a lot more of it into electricity? The answer is yes, and it’s economically compelling.”
Published in Solar Energy, the research introduces a solar-thermal-boosted organic Rankine cycle — a compact power system that converts heat into electricity. By adding low-cost rooftop solar collectors to warm the coolant stream before it reaches the ORC, Rice engineers found a way to turn low-temperature waste heat into a usable energy source.
“Efficiency gains are being outpaced by demand,” says graduate student Kashif Liaqat. “If we want the digital economy to be sustainable, we have to reclaim some of the energy that is currently just thrown away.”
Because this setup doesn’t require additional power to operate (unlike traditional methods of converting heat to energy, such as electric heat pumps), Schaefer says solar thermal offers “a cleaner, simpler pathway” to reducing data centers’ energy consumption.
The team modeled systems in Ashburn, Virginia, and Los Angeles, two of America’s biggest data center hubs. Their hybrid approach recovered 60%–80% more electricity from the same waste heat and cut electricity costs by 5.5% in Ashburn and 16.5% in Los Angeles. “Los Angeles performed better because of stronger solar resources,” Liaqat says. “But even in Ashburn, the hybrid system meaningfully increases output and cuts costs.”
Using off-the-shelf solar collectors connected directly to a data center’s cooling system, the setup functions as a “behind-the-meter” clean energy generator. “It gets stronger when the sun is out — right when cooling loads are highest,” Schaefer explained.
Next steps include testing the system at an operational site and exploring thermal storage for nighttime recovery. “We’re not saying this replaces efficiency work,” Schaefer says. “But we are adding a new tool — one that turns a liability into an asset.”
From the Winter 2026 issue of Rice Magazine