Generating Electricity From Temperature Fluctuations

Scientists in Japan have devised a thermoelectric battery that can convert heat into electricity even with a shallow temperature gradient.

AsianScientist (Feb. 21, 2018) – A team of scientists in Japan has developed a device that generates electricity from minute variations in temperature. They reported their results in the journal Applied Physics Express.

Every time we convert energy from one form to another, part of that energy is lost in the form of heat. Trying to efficiently get that energy back is very difficult once it is lost to the environment. Thermoelectric devices can change heat energy into electricity, and vice versa. But to capture energy from heat efficiently, these devices typically need to work at high temperatures with a large temperature difference.

In this study, researchers centered at Japan’s University of Tsukuba have developed a new kind of thermoelectric system that can harness small energy differences at low temperatures.

“Thermoelectric batteries, like ours, have been proposed before, but those have been based on liquid-based cells, which are impractical for real-world applications. We created a thin-film device that operates on the same principle but with two types of solid redox materials that produce a change in the potential difference in the cell over a heating and cooling cycle,” said first author Dr. Takayuki Shibata of Hokkaido University.

Small changes in temperature alter the ability of different layers in the device to hold onto electrons. If one layer has a greater affinity for electrons than another, a potential difference is created. The flow of electrons from one layer to the other can then be harnessed to do work as the cell is discharged, in the same way that a normal battery works.

The researchers then tested their devices for harvesting waste heat energy near room temperature. Their device produced an electrical energy of 2.3 meV per heat cycle between 25 and 50 degrees Celsius. This result reflected an efficiency of around one percent, although the theoretical maximum efficiency for their devices should have been around 8.7 percent.

“We still have some work to do on improving the efficiency, but we expect that these issues will be overcome by optimizing the anode and cathode materials,” said corresponding author Professor Yutaka Moritomo of Hokkaido University.

“Importantly, we have shown that solid-state thermoelectric batteries are viable and our film deposition method could be extended to large areas. This technology offers realistic prospects for large-scale heat energy recovery, which could be help a range of industries become more efficient.”

The article can be found at: Shibata et al. (2017) Thermal Power Generation During Heat Cycle Near Room Temperature.


Source: University of Tsukuba; Photo: Shutterstock.
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