University of Tsukuba in Japan researchers have developed a way to recover environmental heat with a new type of thin-film thermoelectric cell, based on two different materials that show changes in their redox potential on cycling of temperature. The device is driven by differences in temperature and capable of recovering background heat energy at slightly above room temperature.

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.

The University of Tsukuba researchers have developed a new kind of thermoelectric system that can harness small energy differences at low temperatures. Their results have been reported in Applied Physics Express.

Vcell of the SIB-type thermocell against T. TL (= 295 K) and TH (= 323 K) are the lowest and highest temperatures, respectively. Inset shows schematic picture of the thermocell. Image Credit: University of Tsukuba. Click image for the largest view.

First author Takayuki Shibata said, “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.”

In the device, changing the temperature alters the ability of different layers in the device to hold onto electrons. If one layer has a greater affinity for electrons than another, this creates a potential difference. 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 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 around 25 and 50º Celsius. This result reflected an efficiency of around 1.0%, although the theoretical maximum for this device should be around 8.7%.

Corresponding author Yutaka Moritomo said, “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. 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.”

This technology may be seen as a breakthrough someday. The operating conditions are quite interesting. While the efficiency isn’t exciting yet, the discovery works. and that is the first step with hopefully many more to come.


Comments

4 Comments so far

  1. Bianca on February 22, 2018 1:09 AM

    This technology may be seen as a breakthrough someday. The operating conditions are quite interesting.

  2. Charlie on February 23, 2018 12:24 AM

    In the device, changing the temperature alters the ability of different layers in the device to hold onto electrons.

  3. Charlotte on February 26, 2018 12:41 AM

    This technology may be seen as a breakthrough someday. The operating conditions are quite interesting.

  4. Victoria on February 27, 2018 12:30 AM

    Thermoelectric batteries, like ours, have been proposed before but those have been based on liquid-based cells, which are impractical for real-world applications.

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