Last updated April 17, 2018 at 3:58 pm
No more cooked legs while using your laptop thanks to a new nanofilm.
It’s a feeling most of us will know. You’re sitting on the couch working away on your laptop, and you start to feel your legs getting warmer and warmer from the heat of the laptop. After a while you need to move just to let your legs cool down.
All that heat is wasted energy, a by-product of the workings of the electrical circuits. The more heat produced, the more energy lost.
However, researchers from University of California, Berkeley have worked out a way to harness that lost energy. They’ve developed a special film that could be applied to computers and other equipment to capture the waste heat and use it to produce electrical energy at a level never achieved before.
Electricity from heat
It’s been estimated that nearly 70 percent of the energy that we produce is lost as waste heat – mostly at temperatures less than 100 °C from computers, cars or large industrial processes.
The researchers developed films just 50-100 nanometres thick – around one one-thousandth of the thickness of human hair – that convert heat to electrical energy by a process called pyroelectric conversion. For sources of heat where the temperature fluctuates, the film can turn waste heat into useable energy with higher energy density, power density and efficiency levels than previous pyroelectric energy converting devices.
An illustration of how the thin-film device system converts waste heat to energy. Credit: Shishir Pandya
“We know we need new energy sources, but we also need to do better at utilizing the energy we already have,” said Lane Martin, who oversaw the research. “These thin films can help us squeeze more energy than we do today out of every source of energy.”
Using this pyroelectric conversion, the heat being given off by your laptop could be converted into electricity and fed back into the battery, giving you times between recharges, with the added bonus of a cooler lap.
However, while the researchers suggest that with more development the nanofilm technology could be used for harvesting waste heat from high-speed electronics, it’s also likely we would eventually see it rolled out across a wider range of applications. Everything from electronics to potentially car engines could be used as a heat source.
“By creating a thin-film device, we can get the heat into and out of this system quickly, allowing us to access pyroelectric power at unprecedented levels for heat sources that fluctuate over time,” Martin said. “All we’re doing is sourcing heat and applying electric fields to this system, and we can extract energy.”
Pyroelectric conversion
Pyroelectric conversion has been known for a long time, but one of the challenges of developing thin-film systems was accurately measuring the actual effect itself. And that’s one reason scientists are so excited about these results – not only have they amped up the conversion, but they developed a way to measure the properties of the film while it was happening.
With that shortcoming overcome, the researchers could unlock the potential of the pyroelectric films.
When the temperature of the film changes, for example by absorbing heat from a nearby source, the position of atoms in specially designed structures shift slightly. This shift causes a change in the polarisation of the material, which then creates an electrical voltage.
By changing the properties of nano-structures within the film, the scientists could maximise this polarisation shift and voltage generation.
However, when the temperature stays constant at its new level, the pyroelectric voltage gradually degrades. This makes the new films particularly useful for use with sources where the temperature changes regularly – changing temperature would keep the polarisation changing, and therefore maintain the voltage generation.
For the researchers, they’re next turning their attention to customising the films to optimise their power generation for specific waste heat streams and temperatures.
The research has been published in Nature Materials.
