Our energy needs are diverse, and so are the new innovations to harness different energy sources to supply our demands.
We've been looking at a whole host of interesting and innovative solutions for energy generation recently: from NASA's floor tiles that capture energy from your footsteps, and "solar" panels that generate energy from rainfall, all the way to sensors powered by our own bodily fluids.
Last week, we looked at the possibilities offered by tech which lets us harvest water from the air, via a range of proven techniques to capture evaporated moisture and create clean drinking water. And now it looks like we might even be able to harvest energy from the air as well.
How does that work?
Engineers from the Massachusetts Institute of Technology (MIT) have pursued this idea using a small device called a thermal resonator to capture energy from changing air temperatures (which occur naturally throughout a day-night cycle in many climates across the world) or even from waste heat sources.
Using new concepts from materials science, the researchers published a paper in the journal Nature, highlighting how special materials can dynamically exploit temperature fluctuations, needing as little as a 10 degree Celsius fluctuation to generate small amounts of persistent power, which could be useful as long-term power sources for low-drain, remote devices and sensors.
This thermoelectric system works by capturing heat on one side of the device material only and slowly radiating it across to the other side. By maintaining a common difference, the self-contained, and fully-portable device can consistently generate power.
It is a different approach to other explorations into converting thermal energy into electrical energy - including solar thermal panels, which are now commercially common. This device uses "high-thermal effusivity materials" to allow it to operate in the shade and in any kind of wind condition. It also outperforms other materials, such as more common pyroelectric materials, by a factor of more than three, in terms of power per area.
“We’ve built the first thermal resonator,” says Anton Cottrill, the study’s lead author.
“It’s something that can sit on a desk and generate energy out of what seems like nothing. We are surrounded by temperature fluctuations of all different frequencies all of the time. These are an untapped source of energy.”
While researchers explained that the ideal application of the current device would be difficult to access locations, where batteries need regular replacement or recharging, this kind of technology could also have a significant impact when combined with waste heat, such as in industrial applications or the warmth given off by servers in data centres.
It could also be used as a complement to photovoltaic solar panels, which get less efficient the hotter they become. Adding a device with this kind of heat-to-energy technology could reduce heat stress on the PV cells and cool them down, while at the same time generating bonus electricity by taking the heat away and converting it. Win-win!