This is reprinted from my other blog. I usually confine my posts on this blog to issues with the science of global warming rather than policy issues, but I know I get a lot of folks with science backgrounds here and I would honestly like to see if there is something in this I am missing:
Now when you shop, your can be responsible to power the supermarket tills. As in with the weight of your vehicles that run over the road plates the counter tills can be given power. How? Well, at the Sainsbury’s store in Gloucester, kinetic plates which were embedded in the road are pushed down every time a vehicle passes over them. Due to this a pumping action is initiated through a series of hydraulic pipes that drive a generator. These plates can make up to 30kw of green energy in one hour which is enough to power the store’s checkouts.
The phrase “there is no such thing as a free lunch” applies quite well in physics. If the system is extracting energy from the movement of the plates, then something has to be putting at least as much energy into moving the plates. That source of energy is obviously the car, and it does not come free. The car must expend extra energy to roll over the plates, and this energy has to be at least as great (and due to losses, greater) than the energy the building is extracting from the plates. Either the car has to expend energy to roll up onto an elevated plate to push it down, or else if the plates begin flush, then it has to expend energy to pull itself out of the small depression where it has pushed down the plate.
Yes, the are small, almost unmeasurable amounts of energy for the car, but that does not change the fact that this system produces energy by stealing or leeching it from cars. It reminds me of the scheme in the movie “Office Space” when they were going to steal money by rounding all transactions down to the nearest cent and taking the fractional penny for themselves. In millions of transactions, you steal a lot but no one transaction really notices.
I have seen this idea so many times now portrayed totally uncritically that I am almost beginning to doubt my sanity. Either a) the media and particular green advocates have no real understanding of science or b) I am missing something. In the latter case, commenters are free to correct me.
By the way, if I am right, then this technology is a net loss on the things environmentalists seem to care about. For example, car engines are small and much less efficient at converting combustion to usable energy than a large power station. This fact, plus the energy losses in the system, guarantee that installation of this technology increases rather than decreases CO2 production.
Postscript: One of the commenters on my last post on this topic included a link to this glowing article about a “green family” that got rid of their refrigerator:
About a year ago, though, she decided to “go big” in her effort to be more environmentally responsible, she said. After mulling the idea over for several weeks, she and her husband, Scott Young, did something many would find unthinkable: they unplugged their refrigerator. For good.
How did they do it? Here was one of their approaches:
Ms. Muston now uses a small freezer in the basement in tandem with a cooler upstairs; the cooler is kept cold by two-liter soda bottles full of frozen water, which are rotated to the freezer when they melt. (The fridge, meanwhile, sits empty in the kitchen.)
LOL. We are going to save energy from not having a refrigerator by increasing the load on our freezer. Good plan. Here is how another woman achieved the same end:
Ms. Barnes decided to use a cooler, which she refilled daily during the summer with ice that she brought home from an ice machine at her office.
Now that’s going green! Don’t using electricity at home to cool your groceries, steal it from work!
Update: The one place one might get net energy recovery is in a location where cars have to be breaking anyway, say at a stop sign or on a downhill ramp of a garage. The plates would be extracting speed/energy from the car, but the car is already shedding this energy via heat from its brakes. Of course, this is no longer true as we get more hybrids with dynamic breaking, since the cars themselves are recovering some of the braking energy. Also, I have never seen mention in any glowing article about this technology that placement is critical to having the technology make any sense, so my guess is that they are not being very careful.