One of the best things that’s come from electrified cars is regenerative braking. In cars that use traditional friction brakes, a car’s kinetic energy is turned into heat and dispersed into the environment. With regenerative braking, that energy is turned back into electricity with the use of a generator. But, if you start looking around your car, you’ll notice several other places generating heat, from the radiator to the exhaust pipe. Why aren’t we reclaiming that energy as well?
- Every place your car is hot, your car is throwing away energy that could have been used for acceleration, powering the stereo, etc.
- New research from mechanical engineers at the University of Utah has led to the creation of a silicon chip which converts heat into electricity, which could turn everything from radiators, to shock absorbers, to exhaust systems into generators.
Your car’s radiator is the embodiment of wasted energy. Heat that could be used propulsion is literally cast out into the environment instead of being used. This isn’t just in ICE cars either, everything from EVs to fuel cell cars have cooling systems. (Photo: Getty Images)
Volta, Peltier and generators
The science of generating electricity directly from heat has been understood for over 200 years. The so called, thermoelectric effect, was discovered by Alessandro Volta in 1794. His work involved the heating of two different types of wires, creating voltage. In 1834, French physicist, Jean Charles Athanase Peltier, discovered a device using two parallel conductive plates that can either generate electricity when one plate is cooled and one is heated, or, can work as a cooler or heater if voltage is applied to the device. Unfortunately, these devices have never been efficient enough to warrant their use as generators, until now.
Associate Professor of Mechanical Engineering, Mathieu Francoeur, at the University of Utah recently published a paper in the journal, Nature Nanotechnology, explaining how his new device exceeds the limits of Black Body Radiation, previously thought impossible. It has the potential to change everything from cars to mobile phones.
Technology to the rescue
Black Body Radiation is energy absorbed or emitted by an object that is purely thermal. A theoretical limit exists at which any more energy turns into light emissions. Francoeur’s device has surpassed that limit and allows greater efficiency in converting heat to electricity than believed possible.
The device uses two silicon wafers, both 5 mm (0.197 inches) square. The use of silicon wafers is fairly new in this application, previously most of the devices were made using metal plates, sometimes exotic.
What makes this work unique, is being able to position the two wafers just 100 nanometers apart. It has been understood for quite some time that the closer the two plates, the more efficiency increases. However, if the two plates touch, the thermoelectric effect doesn’t work. The gap between the plates is maintained by spacers he refers to as micropillars and a vacuum exists between the two plates.
Turbochargers on ICE powered cars recover some of their wasted heat. But, If youve ever accidently brushed up against a tailpipe, you know there is still plenty of heat energy escaping out the back of the car. (Photo: Getty Images)
WHY THIS MATTERS
Right now, Francoeur’s work is all the laboratory. But, if it can be adapted to real world applications, it could be applied to anything that requires cooling. At this point, all cars whether full electric, hybrid, fuel-cell or even just ICE powered, require cooling systems. Turning heat back into electricity instead of just throwing it out into the environment could drastically improve efficiency. As an earlier example, Francoeur calculated a laptop using his device could go from six hours of battery life to nine hours, a 50 percent improvement. It might not scale-up the same way to cars, but even if it’s only 20 percent, that is still free energy.