Datacenter cooling could get a lot more affordable, and sustainable, if a joint German-Japanese research project can be scaled beyond the laboratory.
Researchers from the Karlsruhe Institute of Technology and the University of Tsukuba published a paper in Nature Energy on Friday discussing the success they had with a solid-state cooling technology that doesn’t need any electric input at all, and was still able to demonstrate temperature reductions in laboratory experiments.
For those unfamiliar with solid-state cooling, it’s a more sustainable alternative to traditional compression cooling that relies on environmentally harmful refrigerants and lots of electricity. Instead of compressing and expanding a gas to generate cold, some solid-state systems rely on thermoelectric materials that, when supplied with electricity, can generate temperature differences. Thermoelectric solid-state cooling systems can be incredibly small, but there’s a catch: They still need energy, and they’re only a quarter as efficient as modern compression cooling systems, as the researchers noted.
Enter elastocaloric cooling, which relies on shape-memory alloys that change temperature when mechanically loaded and unloaded through a phase transition. It’s that sort of material and methodology that the KIT and Tsukuba team experimented with.
Like other forms of solid-state cooling, elastocaloric systems have traditionally required electricity to effect change in the shape-memory alloys they use, relying on actuators that can get quite large. What the researchers wanted to develop was a miniaturized form of elastocaloric cooling that didn’t require any electricity at all, instead relying on the waste heat being generated by the objects it wanted to cool – for example, a computer processor, as they mention in their paper. Based on their demonstration, it appears to have worked.
The researchers used a pair of super thin nickel-titanium foils for their elastocaloric system with opposing functions: One foil shrinks when subjected to heat, generating movement that translates into mechanical energy and acting as its own actuator. That mechanical energy is transferred to the second foil, which is loaded and unloaded to trigger a phase transition that produces the cooling effect.
Laboratory tests demonstrated that their technology isn’t only theoretically feasible, but also actually works – albeit to a limited extent.
“Our prototype achieves a temperature span of 12.9 K at the refrigerant film level and 4.0 K at the device level under Joule-heated actuation at 86°C (187°F),” the team said in their report. When subjected to an external heat source of 130°C (266°F), the system still maintained a device-level temperature span of 2.2 K – not a lot, but it still shows the device, even at its most basic, single-pair-of-films level, works.
"For us, the decisive moment was seeing measurable cooling for the first time, actually generated by a heat-driven system," KIT PhD candidate and paper lead author Yi-Ting Hsiau said of the project in a release put out by the university. "This showed us that the principle doesn't just work on paper."
With the concept of electricity-free miniaturized cooling now proven, the team is planning to build larger experimental units to optimize cooling performance.
Electricity-free and water-free cooling designs couldn’t come at a better time: Energy generation used to power and cool things like datacenters is on the rise, as is the water footprint of such facilities, in part also linked to cooling. Add climate change to the mix, and cooling electronics and people is only more of a concern – according to IRENA, heating and cooling together now account for more than 40 percent of global energy-related carbon dioxide emissions. Sorting out the datacenter energy and water problem has a lot to do with figuring out how to keep systems cool, and while this research is in its infancy, it could prove to be a valuable contribution to reducing the tech industry’s energy footprint.
"We believe this is just the beginning," said Jingyuan Xu, head of KIT’s ZEco Thermal Lab, working on zero-emissions and eco-friendly heating and cooling tech. "By scaling up this technology, we aim to develop compact cooling systems that utilize abundant heat sources for sustainable cooling." ®
