Unless you’ve been living out of a car trunk the past few months, you’ve probably heard at least something about the big splash electric vehicles are making in the market for new automobiles. Yet, despite all the awards heaped on the Tesla Model S and the fierce loyalty shown by owners of the Chevy Volt, electric cars are still far from proving a slam dunk with the general public.
You can chalk up at least part of that ambivalence to the longtime bane of electric vehicles – their own limited range. With presently available battery technology, it’s just plain tough to supply power to an electric motor, run the electronics store’s worth of gadgets and appliances in a modern car, and still go very far in a single charge.
But what if the very act of driving down the road itself produced electricity? What if there was a way to harvest energy directly from contact with the road surface?
It turns out that such a thing is indeed possible.
Researchers with the University of Ontario Institute of Technology did it back in 2011. They used piezoelectric sensors to translate physical pressure into electric current, not too much unlike the human-powered dance floor we featured in a previous article.
Individual sensors were arranged along the inside of a tire. The sensors were made of a material known as lead zirconate titanate, or PZT (recall that the Latin name for the element lead is plumbum, hence the “P” in PZT). When bent, PZT produces an electrical charge.
When a vehicle tire rolls down the road, the weight of the vehicle it supports causes the tire to deform along its bottom surface, where it meets the street. The University of Ontario researchers adjusted their experiment so that at 854 rpm (the equivalent of 62 mph, or 100 km/h), the layered PZT modules inside of their laboratory tire produced 4.6 watts. Even if multiplied by four tires, that’s not a lot of juice – about enough to light an 18-watt LED light bulb (which in turn offers the brightness of a 75-watt traditional incandescent).
That’s not an amount you’d want to try to run a blow dryer from. But, researchers Noaman Makki and Remon Pop-Iliev note, “Such a setup permits the extraction of tire-generated power to run onboard electronics.”
Theirs isn’t the only design to propose drawing energy from rolling tire pressure. Inventor Nevres Cefo was awarded a U.S. patent in 2001 for his “Electrical power generating tire system” idea. Cefo’s design takes quite a different approach, using the deformation of a rolling tire to push a set of magnets into a cylindrical receiver. This creates an electromagnetic field that, brought into proximity with a wound metal coil, produces electricity. With four (or possibly more) sets of magnets spaced evenly around the tire, rapid tire rotation would in effect make the wheel an electrical generator.
Might we someday see this type of technology in everyday vehicles? More offbeat and less practical innovations have certainly made their way into automobiles – headlight lens wipers, anyone? There’s already a precedent for placing electronic devices in tires, namely, the tire pressure monitoring systems that became mandatory in passenger vehicles during the first decade of this millenium.
Combined with systems such as transparent solar cells on automotive glass and other surfaces, and constantly improving batteries, power-producing tires could make the “range anxiety” associated with electric cars a thing of the past.