Every time you stream a show, upload a photo, or ask an AI a question, powerful computers inside data centers are working nonstop.
These facilities use enormous amounts of electricity and produce just as much heat.
Keeping them cool already requires a large share of their energy use, and nearly half of that ends up wasted as low-temperature heat that simply drifts into the air.
Researchers at Rice University may have found a way to change that.
Their new study shows how to capture that wasted energy and turn it back into clean electricity by giving it a little boost from the sun.
“Data centers are like invisible rivers of warm air,” said Laura Schaefer, professor of mechanical engineering at Rice.
“The challenge is that the heat they produce isn’t quite hot enough on its own to be useful. We asked whether sunlight could give it the lift it needs, and the answer is yes.”
The system they designed is called a solar thermal-boosted organic Rankine cycle (ORC). An ORC is a compact generator that can produce electricity from low-temperature heat using a safe working fluid.
By itself, data center heat is usually too cool to power an ORC efficiently. But the Rice team added a clever twist: simple rooftop solar thermal collectors, the same kind often used to heat water in homes.
These collectors warm up the coolant stream just before it enters the ORC, creating a “solar bump” that makes the process practical and cost-effective.
The team tested their idea with computer models in two very different U.S. data center hubs: Ashburn, Virginia, and Los Angeles, California. Both rely heavily on data infrastructure, but Los Angeles enjoys far more sunshine.
The results were impressive in both places. The hybrid system was able to recover 60% more electricity in Ashburn and 80% more in Los Angeles compared with using waste heat alone.
During sunny hours, efficiency jumped by more than 8%, and the cost of producing electricity from the waste heat dropped by over 5% in Virginia and more than 16% in California.
Graduate student Kashif Liaqat, who co-authored the study, explained why this matters: “Data centers already consume as much electricity as a mid-sized country, and demand is only growing. If we want digital growth to be sustainable, we have to reclaim some of the energy we’re throwing away.”
What makes the approach even more appealing is its simplicity. The solar collectors are low-cost and low-profile, making them easy to mount on data center rooftops.
Because the ORC runs on the waste-heat side of the cooling system, the electricity it generates directly offsets grid power use, acting like a behind-the-meter clean energy source that works best exactly when cooling loads are highest—on hot, sunny days.
The researchers now want to test the system in a real-world data center and explore adding thermal storage, which could capture solar heat during the day and use it at night.
They believe this method won’t replace other efficiency efforts, but it can be a valuable new tool. As Schaefer put it, “We’re turning what used to be a liability into an asset.”
