Last year the California Energy Commission posted the results of a study aimed at assessing efficiency of deploying piezoelectric systems to generate clean electricity from roadways.
“Based on the laboratory evaluations and road tests, the application of the piezoelectric energy harvesting system in one lane of a one-mile-long roadway has the potential to generate 72,800 kilowatt-hours of energy per year,” the team reported.
How is that clean energy, in any sense of the word? Any system that gains some energy from a passing car must necessarily decrease the (kinetic) energy of the car by an equal or greater amount. And the vast majority of cars get their kinetic energy by burning fossil fuels. Sounds like a more expensive, less direct, and less efficient version of a gasoline generator.
It depends. Is this energy the same energy that is already being burned?
Looking at an extremely simple example: Solar powered calculators (the real ones). They harness light from the light bulbs in a room which would be otherwise dark. The only time they are harnessing that power, is when the light is on. They add no extra draw to the light, they are 100% passive. The only time you’d really have to take into consideration how green that power is (explicitly for the calculator) is if you are turning on that light explicitly to power the calculator.
If the tech being talked about is just harnessing the “junk energy” of the vehicles in their normal operation, this would be 100% green energy. If it is adding a load, it is 100% dirty when powered by an ICE. If it’s somewhere in the middle… I hope you get my point.
You’re also ignoring the fact that not all vehicles are ICE.
That’s a fair point, a device could theoretically harvest energy that would have otherwise been wasted, and that would be green energy. I imagine a wind system could work, though it might result in cars experiencing additional drag from slower wind speeds.
However, the piezoelectric generators mentioned in the article quite clearly do not use waste energy. They compress under the weight of the cars, turning a small amount of gravitational potential energy into electricity. That energy must be made up with extra fuel.
Finally, even if all of the vehicles on the road were powered by clean electricity, it would still be a useless system. Piezoelectrics are nowhere near 100% efficient, so you’re just taking electricity from the vehicles at a loss.
I mean, I can think of many ideal places for such things. Intersections for instance, where cars will be wanting to slow down or come to a stop regardless. Speed limit changes, where you want cars to slow down. Even in place of speed bumps, assuming you can get enough of a drag on the car to effect a slow down.
How is that clean energy, in any sense of the word? Any system that gains some energy from a passing car must necessarily decrease the (kinetic) energy of the car by an equal or greater amount. And the vast majority of cars get their kinetic energy by burning fossil fuels. Sounds like a more expensive, less direct, and less efficient version of a gasoline generator.
It depends. Is this energy the same energy that is already being burned?
Looking at an extremely simple example: Solar powered calculators (the real ones). They harness light from the light bulbs in a room which would be otherwise dark. The only time they are harnessing that power, is when the light is on. They add no extra draw to the light, they are 100% passive. The only time you’d really have to take into consideration how green that power is (explicitly for the calculator) is if you are turning on that light explicitly to power the calculator.
If the tech being talked about is just harnessing the “junk energy” of the vehicles in their normal operation, this would be 100% green energy. If it is adding a load, it is 100% dirty when powered by an ICE. If it’s somewhere in the middle… I hope you get my point.
You’re also ignoring the fact that not all vehicles are ICE.
That’s a fair point, a device could theoretically harvest energy that would have otherwise been wasted, and that would be green energy. I imagine a wind system could work, though it might result in cars experiencing additional drag from slower wind speeds.
However, the piezoelectric generators mentioned in the article quite clearly do not use waste energy. They compress under the weight of the cars, turning a small amount of gravitational potential energy into electricity. That energy must be made up with extra fuel.
Finally, even if all of the vehicles on the road were powered by clean electricity, it would still be a useless system. Piezoelectrics are nowhere near 100% efficient, so you’re just taking electricity from the vehicles at a loss.
I mean, I can think of many ideal places for such things. Intersections for instance, where cars will be wanting to slow down or come to a stop regardless. Speed limit changes, where you want cars to slow down. Even in place of speed bumps, assuming you can get enough of a drag on the car to effect a slow down.