Here’s a news item that may get a “So what?” reaction from many readers. But reserve judgment until the end to find out why this could actually be big news. Researchers at MIT have come up with a device they call a thermal resonator that harvests energy from changes in temperature. As reported by Engadget, the thermal resonator has a foam made of nickel or copper at its core that is coated with graphene to increase its conductivity. Then it is infused with octadecane, a phase-changing material that stores the electricity created. The result is a device that is always capturing heat on one side and storing it on the other.
A thermal resonator could capture electricity from the difference in ambient temperature between daytime and nighttime. Another example is the difference in temperature between a building during normal business hours and overnight. “We’re surrounded by temperature variations and fluctuations, but they haven’t been well-characterized in the environment,” says Michael Strano, one of the team of researchers at the MIT chemical engineering laboratory.
The devices can be adapted to respond to specific changes in temperature, such as those that occur when an electric motor or compressor cycles on and off. “We are surrounded by temperature fluctuations of all different frequencies all of the time. These are an untapped source of energy.”
The first working prototype produces only 1.3 milliwatts of current. Not much, but enough to power sensors in remote locations without needing to connect them to a power source. “We basically invented this concept out of whole cloth,” Strano says. “It’s something that can sit on a desk and generate energy out of what seems like nothing.” The MIT researchers have been using an early prototype to power the weather monitoring system seen in the photo. The thermal resonator is in the black box located behind the white weather sensors. The black case to the left contains test equipment to monitor the performance of the prototype.
The team suggests the devices could serve as backup power sources that supplement more traditional sources. For instance, they can function when solar panels are shaded. They can even be mounted beneath solar panels where their heat absorbing properties could help cool the panels, boosting their efficiency. While there are other pyroelectric devices, the thermal resonator has proven in testing to produce up to three times the electricity of those other devices.
Here’s the good news I promised you earlier: Some of you may remember when LEDs were first invented. Early prototypes gave off little more than a faint glow. Today, they are bright enough to be used for automobile headlights and theater lighting, among other common uses. Don’t scoff at a device that puts out a wimpy 1.3 milliwatt current. Think instead what it could mean for the future.
Kourosh Kalantar-zadeh, an engineering professor at RMIT University in Melbourne, Australia, agrees with me. It’s “a novel development with a great future,” he says. “It can potentially play an unexpected role in complementary energy harvesting units. To compete with other energy harvesting technologies, always higher voltages and powers are demanded. However, I personally feel that it is quite possible to gain a lot more out of this by investing more into the concept. It is an attractive technology which will be potentially followed by many others in the near future.”