German-Japanese solid-state cooler demonstrates heat-driven cooling without electricity

New lab-scale device uses thermal expansion of nickel-titanium alloys to create minimal cooling without electricity, offering potential for ultra-low-energy refrigeration systems.

Researchers from Germany’s Karlsruhe Institute of Technology and Japan’s University of Tsukuba developed a solid-state cooler using two nickel-titanium-based films: a 22-micrometer titanium-nickel (TiNi) thermal actuator and a 26.5-micrometer titanium-nickel-iron (TiNiFe) refrigerant layer. The device operates via a heat-driven cycle—no electrical motors required—where thermal expansion of the actuator triggers phase transitions in the refrigerant. In lab tests, it achieved a 12.9-kelvin temperature span with electrical resistance heating, settling at 4.0 kelvins after 20 cycles and maintaining 2.2 kelvins with a 130°C heat source. It produced 2.09 milliwatts of cooling power at 3.32 watts per gram of active material. Published in *Nature Energy*, this is a feasibility study, not an optimized system. The device’s milliwatt-scale output is insufficient for high-power applications like GPUs, and its temperature spans are too small for modern thermal loads.

This work addresses energy-intensive refrigeration—a key energy sector—by proving heat-driven cooling without electricity. While current output is too low for practical use, the principle demonstrates how thermal expansion could eventually reduce global electricity demand for cooling, particularly in resource-constrained settings where refrigeration access is limited. For now, it remains a lab demonstration; scaling to meaningful cooling capacity would require significant engineering advances.

The signal moves *energy* abundance potential by showing a pathway to ultra-low-energy cooling systems. It does not yet impact *sustenance* or *security* needs directly but could later reduce electricity costs for refrigeration in developing regions. Current limitations mean it’s a friction item: the technology is not ready for real-world deployment. Next, researchers must optimize the system for higher cooling capacity and larger thermal loads to move beyond milliwatt scales. The source notes this is a feasibility study—not a commercial solution—so the full potential remains unproven.

Source: New Atlas