Tech Insights

Purdue Engineers Invent Continuously Tunable Device to Manage Heat in Batteries

June 26, 2023 by Shannon Cuthrell

Purdue University engineers have developed a continuously tunable thermal regulator that improves upon conventional thermal switches. 

Mechanical engineers at Indiana-based Purdue University recently developed a continuously tunable thermal regulator to manage heat in batteries and electronic devices. The solid-state device can reliably insulate against cold, dissipate heat, and work across a wide temperature range. 

 

Zixin Xiong, a Ph.D. candidate in mechanical engineering at Purdue, studies high-temperature thermal transport in the university’s Marconnet Thermal and Energy Conversion Lab

Zixin Xiong, a Ph.D. candidate in mechanical engineering at Purdue, studies high-temperature thermal transport in the university’s Marconnet Thermal and Energy Conversion Lab. Image used courtesy of Purdue University/The ESC Plan, by Charles Jischke

 

Developed with compressible graphene foam composites, the regulator can improve safety and performance in electronic device batteries and serve other systems such as electric vehicle batteries, space conditioning, and energy storage applications. 

The patent-pending device provides a stable thermal balance critical to a battery’s performance and safety—avoiding thermal runaway processes that can cause fires when the battery is too hot while also preventing internal damage from temperatures too low. 

According to Purdue, during testing at 85% strain between uncompressed and fully compressed settings, the graphene-based switch achieved thermal conductance at a ratio of 8.09. It also had a heat flux of 3 kilowatts per square meter and a 50 degrees Fahrenheit (°F) adjustable temperature window, which equates to an optimal thermal control device capable of accommodating harsh environments. 

 

How the Thermal Control Device Works

The tunable device marks an improvement from conventional thermal switches, which are limited since they manage heat dissipation by simply turning the conduction on or off. 

Amy Marconnet, one of the co-inventors and an associate mechanical engineering professor at Purdue, likened conventional thermal management technology to a scenario where people—the batteries, in this case—wear the same clothes all year round and in every climate. A tunable thermal regulator allows the battery to be insulated in cold conditions. And in warm environments, the heat can easily be dissipated. 

Envisioning a continuously tunable design, the Purdue engineers used compressible graphene foam built from nanoscopic carbon particles deposited in a pattern and separated by small air pockets. The foam acts like an insulator when uncompressed, and the air helps maintain the heat’s position. On compression, the air is released, and heat spreads in the foam. One can dial in the level of heat transfer based on the foam’s compression. 

In tests, the engineers placed a graphene foam sample (1.2 millimeters thick) between a heater and a heat sink and measured the temperature and heat flow using an infrared microscope. They found that when the foam was fully compressed (to 0.2 mm thick), its conductance increased to a factor of 8. The invention showed similar results in ambient temperatures ranging from 32 to 86 °F. 

 

engineers developed a continuously tunable thermal regulator using graphene foam

Purdue University engineers developed a continuously tunable thermal regulator using graphene foam, which uses compression to adjust the conductance. Image used courtesy of Purdue University by Tingting Du

 

Potential Applications

While the tunable thermal regulator was originally intended for EV batteries, it can also serve other applications, including energy storage and space conditioning. 

Additional uses could include sensors and detectors for industrial applications that need precise temperatures to maintain. The devices can also help sustain an appropriate temperature for space vehicles that endure harsh environments. 

A patent is pending for the technology. The inventors said they plan to focus on enhancing the range of thermal conductances with the regulator. They’re also looking to automate its manual operation, possibly using feedback from temperature sensors to adjust the parameters.