Energy is all around us – we just need to work out how to tap into it. Now a team from MIT has developed a device called a thermal resonator, which could essentially pull electricity out of thin air by taking advantage of gradual ambient temperature changes over the course of the day.

Scientists have been experimenting with ways to use temperature fluctuations as a source of energy for years now. Most of these devices work on the thermoelectric principle, meaning they generate electricity by taking advantage of temperature differences between two sides of a material. As heat travels from the hotter side to the cooler side, charge carriers flow with it and create a voltage difference, generating electricity in the process.

Previous work has applied the thermoelectric effect to clothing, paint and cooking pots, and these materials may eventually be built into factories and power plants to recycle waste heat. However, in all of these applications the temperature difference needs to be quite significant. The new technique taps into more gradual fluctuations over longer periods of time, allowing it to work with the natural changes in temperature throughout the day. This is called the pyroelectric effect.

"We basically invented this concept out of whole cloth," says Michael Strano, co-author of the study. "We've built the first thermal resonator. 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."