Recycling Heat Just Got Way Cooler

Image courtesy Hinode JAXA/NASA

For indispensable reporting on the coronavirus crisis, the election, and more, subscribe to the Mother Jones Daily newsletter.


We waste 60 percent of all the energy we produce burning fuels and in power plants—most lost as excess heat. If we could harvest that waste heat we could use a lot less electricity.

Now a paper in the current Journal of Applied Physics suggests a new way to recycle waste heat. The process might, for instance, double the run time of cellphones and laptop computers and increase output in power plants.

Here’s the current conundrum. Existing solid-state technologies that convert heat into electricity are inefficient. Existing systems that efficiently convert heat into electricity produce very little power. Your choice: high efficiency or high throughput, but not both.

On top of all that, theory predicts that energy conversion can never exceed a specific value, the Carnot Limit. Even so, modern commercial thermoelectric devices only achieve about one-tenth of the Carnot Limit.

So how to do it better?

The MIT experiments involve a different technology—thermal diodes—which suggest future efficiencies as high as 40 percent of the Carnot Limit and ultimately perhaps 90 percent.

Here’s what the researchers did:

  • They started from scratch rather than trying to fix existing devices.
  • They carried out their analyses using a supersimple system that generated power with a single quantum-dot device—a kind of semiconductor confining electrical charges very tightly in all three dimensions.

Add to their efforts the results of another MIT paper showing an intermediate step towards achieving heat transfer at a rate orders of magnitude higher than predicted by theory.

The end result: heat converted into harnessable electricity at a rate promising enough that a new company, MTPV Corp (Micron-gap Thermal Photo-Voltaics), is already working on the development of a new technology based on the work described in this paper.

Co-author Peter Hagelstein tells MIT that when work began on the project in 2002 such heat-recycling devices “clearly could not be built. We started this as purely a theoretical exercise.” Developments since then have brought theory much closer to reality.

I suppose someone’s going to get filthy rich and powerful making a cleaner-powered world… Conundrum: Part 2?
 

DEMOCRACY DOES NOT EXIST...

without free and fair elections, a vigorous free press, and engaged citizens to reclaim power from those who abuse it.

In this election year unlike any other—against a backdrop of a pandemic, an economic crisis, racial reckoning, and so much daily bluster—Mother Jones' journalism is driven by one simple question: Will America move closer to, or further from, justice and equity in the years to come?

If you're able to, please join us in this mission with a donation today. Our reporting right now is focused on voting rights and election security, corruption, disinformation, racial and gender equity, and the climate crisis. We can’t do it without the support of readers like you, and we need to give it everything we've got between now and November. Thank you.

DEMOCRACY DOES NOT EXIST...

without free and fair elections, a vigorous free press, and engaged citizens to reclaim power from those who abuse it.

In this election year unlike any other—against a backdrop of a pandemic, an economic crisis, racial reckoning, and so much daily bluster—Mother Jones' journalism is driven by one simple question: Will America move closer to, or further from, justice and equity in the years to come?

If you're able to, please join us in this mission with a donation today. Our reporting right now is focused on voting rights and election security, corruption, disinformation, racial and gender equity, and the climate crisis. We can’t do it without the support of readers like you, and we need to give it everything we've got between now and November. Thank you.

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate