Rechargeable batteries help power the products that enhance our quality of life such as smartphones, laptops, tablets, portable music players, and electric vehicles. Though these rechargeable batteries make life easier in many ways, they also cause major headaches. The materials that go into the batteries, such as lithium, are hard to come by and also difficult to recycle due to their toxicity. Fortunately, researchers at MIT have developed a system for converting heat into electricity, which would allow society to lessen its dependence on the harmful batteries.
The process creates electricity when fuel-coated carbon nanotubes are lit from one end, and burn through to the other, like a fuse. As MIT described in a press statement, “the effect arises as a pulse of heat pushes electrons through the bundle of carbon nanotubes, carrying the electrons with it like a bunch of surfers riding a wave.”
The system isn’t new: it came into existence in 2010 following a breakthrough made by MIT Chemical Engineering Professor Michael Strano and other employees of the institute. However, the initial development, based on “a previously unknown phenomenon,” didn’t produce enough current to be effective. As a result, the employees worked with the system so that they could not only make it more efficient, but also convey just how the process works.
Today, the researchers are able to prove the theory via their mathematical model which provides an explanation as to why the hot wave sometimes produces single voltage, while in other instances it produces two diverse voltages.
The research team’s theory, as quoted by MIT, shows that “the thermopower wave ‘divides into two different components,’ which sometimes reinforce one another and sometimes counter each other.”
The reworked system is much more efficient than it was before. This improved productivity has helped to create devices that turn heat energy into electrical energy at greater than a 1 percent efficiency. Though that figure may seem low, the energy efficiency is thousands of time greater than anything previously reported, according to the team.
The process has resulted in devices that are on par with the best modern batteries, like lithium-ion or fuel cells, according Strano.
The team no longer coats the carbon nanotubes with explosive fuel. Instead, they choose to cover the nanotubes with ordinary table sugar. As sweet as the current fuel is, the team hopes to use other combustion fuels in the future. The system just needs heat to work, so a variety of future heat sources that result in better efficiency are fair game, according to Strano.
Though the team has used the nanotube-based power system to fuel simple devices, such as LED lights, the system has the potential to power much more. Albert Liu, an MIT doctoral student who worked with Strano and the rest of the team on the upgrade of the system, said that the system “should have a virtually indefinite shelf life.” The longevity of the system’s power production could make it useful on deep-space probes, according to MIT.
The system is also very versatile because of its varying sizes. This makes it increasingly suitable for smart watches, fitness trackers, and other wearable devices.
Though there is an impetus to replace batteries using toxic materials as soon as possible, and much progress is being made with the system, it will likely be several years before it is used to produce a widely commercialized product, the team said.
The group of researchers consist of Strano, Liu, Sayalee Mahajan, Anton Cottrill, Yuichiro Kunai, David Bender, Javier Castillo Jr., and Stephen Gibbs. Their latest findings were recently published in Energy & Environmental Science.
