Research shows a new way to harvest energy via heat

A research paper published by scientists at the Ohio State Univesity introduces a potential new way to harvest waste heat generated by magnetic materials, to repurpose them into useful energy once again.

Thermoelectric systems are mainly designed to use temperature differences in order to generate electric energy. However, due to inherent limitations of harvesting electric energy from heat, such systems are never actually used as a main source of energy. Instead, they are incorporated as a backup for engines and other machines that produce lots of heat, in order to increase the overall efficiency of that particular system.

For example, a typical internal combustion engine will have a thermoelectric system that is capable of capturing at least 20 percent of its generated heat, transforming it into electric energy to charge a car’s built-in lead-acid battery.

This new research explains that overall thermoelectric efficiency can be increased further by exploiting the properties of tiny particles called paramagnons. Normally, a thermoelectric system would use a temperature gradient — the movement of higher temperature electrons towards the colder part of the material induces the same effect as moving electrons using an electric charge or magnetic field (a.ka. the Seebeck effect). However, the temperature gradient also creates an additional effect of increasing the magnetic field on the colder side, while significantly weakening it on the hotter side.

An electric generator using the Seebeck effect.

It has been long thought that the heated part is not capable of producing additional energy. First, because the electrons have already moved towards the colder part. And second, it has effectively become a paramagnet, which has weaker magnetic properties because the material’s temperature had become sufficiently high enough to disrupt its molecular alignments.

The study has discovered that paramagnons, high-temperature magnetic particles that still retains some magnetic flux, are actually capable of pushing electrons via what is called a magnon-drag thermoelectric effect. This means, that even the heated part of the thermoelectric system would technically be capable of generating more electricity than it normally would if the correct material and configuration is used.

According to the published paper, the paramagnons are capable of pushing the electrons at “only for a billionth of a millionth of a second”. This, however, is already sufficient enough to get electrons moving at one direction to induce an additional electric current.

The conclusion of the research makes it clear that this is not some magical breakthrough where waste heat is now perfectly recyclable, or that thermoelectric systems are now closer to being an actual primary source of energy. More likely, this would simply increase the efficiency of future thermoelectric systems only by a tiny bit.

That being said, in systems where the tiniest bit of efficiency counts, such as space-based energy generation systems, this discovery would be very crucial in making thermoelectric energy even more viable in lessening the wasteful effects of heat generation during energy use.

Featured Image credit by Ministério de Minas e Energia via Flickr
Diagram Image credit by Ken Brazier via Wikimedia Commons

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