Researchers at MIT are developing new technology for converting heat into light and then into electricity that could eventually save fuel in vehicles by replacing less-efficient alternators and allowing electrical systems to run without the engine idling.
The technology, called thermophotovoltaics, uses gasoline to heat a light-emitting material, in this case tungsten. A photovoltaic cell then converts the light into electricity. The idea has been around since the 1960s, says John Kassakian, MIT electrical engineering and computer science professor. But until now, the light emitters for the photovoltaics produced inefficient and very costly systems. Improvements in the materials used in these latest devices – possible in part because researchers can modify the material structure at the nanoscale – are now making much more efficient systems, Kassakian says.
According to Kassakian, the system could potentially be a more efficient way to power electrical systems in a vehicle than the current alternator-based one, which wastes energy in two stages: the internal combustion engine converts only about 30 percent of the energy in fuel into movement, and then the alternator is only 50 percent efficient in converting the mechanical energy into electricity. He says a small prototype thermophotovoltaics device that could confirm the system’s improved efficiency might be ready in a year.
The researchers modified the surface structure of the light emitter, etching into it nano-sized pits to tune the wavelengths of light emitted to precisely those a photovoltaic cell can convert most efficiently into electricity. They further refined the device with the use of filters that allow the desired wavelengths of light to pass through to the photovoltaic cells, but reflect other wavelengths back to the light emitter. The reflected light carries energy that helps keep the emitter hot, reducing the amount of fuel needed.
In addition to replacing the alternator with a thermophotovoltaic module, says Kassakian, the technology could be part of an air-conditioning system for vehicles that doesn’t require a compressor. Because this would significantly decrease the load on an engine, it could make it possible to turn off the engine when the vehicle stops in traffic and easily restart it. Today’s hybrids use this technique to save gas, but require large batteries to provide electricity for the radio and lights, and to restart the engine, and they have to turn the engine back on when the battery charge runs out. In the new MIT system, these batteries wouldn’t be necessary.
Indeed, if the new materials do make more efficient thermophotovoltaics, there will be no shortage of potential uses. Kassakian says a particularly good application, when combined with the a new air-conditioning system, could be for use in trucks with sleeper cabs to cool the cabs and provide electricity for televisions and other equipment. And, says Donald Chubb, a researcher at the NASA Glenn Research Center, “The military has had a lot of interest in it for portable power supplies in the field. Because there are no moving parts, there wouldn’t be any noise, so you couldn’t detect it.”
It will be several years before the technology can used in vehicles, though. Challenges include scaling up the fabrication process, developing effective insulation and cooling systems to manage the heat generated, and ensuring that the system remains efficient on a larger scale. The MIT research is funded in part by Toyota, but the automaker has not committed to implementing the technology.
Why China is still obsessed with disinfecting everything
Most public health bodies dealing with covid have long since moved on from the idea of surface transmission. China’s didn’t—and that helps it control the narrative about the disease’s origins and danger.
These materials were meant to revolutionize the solar industry. Why hasn’t it happened?
Perovskites are promising, but real-world conditions have held them back.
Crypto is weathering a bitter storm. Some still hold on for dear life.
When a cryptocurrency’s value is theoretical, what happens if people quit believing?
Anti-aging drugs are being tested as a way to treat covid
Drugs that rejuvenate our immune systems and make us biologically younger could help protect us from the disease’s worst effects.
Get the latest updates from
MIT Technology Review
Discover special offers, top stories, upcoming events, and more.