Sainsbury’s brings green power to the checkout with ‘kinetic plates’

Energy will be captured every time a vehicle drives over “kinetic road plates” in the car park and then channelled back into the store.

The kinetic road plates are expected to produce 30 kWh of green energy every hour — more than enough energy to power the store’s checkouts. The system, pioneered for Sainsbury’s by Peter Hughes of Highway Energy Systems, does not affect the car or fuel efficiency, and drivers feel no disturbance as they drive over the plates.

My first reaction is that somebody apparently thinks they can violate the first law of thermodynamics. If the energy comes from the car, then it will necessarily affect the car — it will slow it down. Now, this makes sense if you install it where the car was going to slow down anyway, like an approach to a stop sign. But not if the car is going to want to maintain speed, or if the slowdown/stopping is unnecessary.

Sincerely sustainable contains a quote which implies that these are being used as speed bumps. But harvesting energy from speed bumps is only green in a very abstract way, since the car is going to speed up again once past it — you’d be greener by not having the speed bumps there at all, which is one reason why you get better mileage on the highway — you eliminate those stops and starts. A car that is already going the desired speed is going to surrender energy to the device and slow down even though it didn’t need to. Green-wise, you’d be better served with an improved design of the traffic flow. (They also claim that they will generate 30 kW of electricity every hour, when they mean 30 kWh. Call the unit police.)

What they are doing is getting the customers to pay for some of their electricity.

Another example of this appears in Cocktail Party Physics : body heat (spoiler: it stars neither Kathleen Turner nor William Hurt)

Boesel has retrofitted much of his exercise equipment (stationary bikes, treadmills, elliptical machines) so that gym members can produce a little bit of usable energy during their workouts — not a lot, mind you, but enough to run the fans, for example, or the stereo system. Combine that with other strategies for improving energy efficiency, and Boege keeps his electricity costs to a bare minimum. In time, he thinks he can break even, and maybe even turn a small profit.

Tapping the energy from the exercise equipment is a fine goal for the owner, but calling it green is another thing. It’s being powered by the food we eat, via our physical exertion, and that means you have to look at the energy used to bring that food to the table. Dollars to donuts (or tofu) that energy is not green — the delivery trucks run on gas or diesel, the water may be bottled, etc. So once again, the circumstances matter. If you’re recovering otherwise wasted energy, fine, but don’t get on the treadmill for the purpose of generating energy. If someone needs to consume an extra few calories so they can go work out, they’ve basically become a very inefficient battery, and the energy they generate isn’t green. Much like the regenerative braking on Jennifer’s Prius: if you drive around the block, stopping and starting, in order to charge up the battery, then energy will have come from the gasoline.

I noticed the phrase “judicious use of the A/C.” If that means making the patrons sweat some more, there’s the cost of un-doing the dehydration. As I noted in my inaugural post, excess sweat is wasted, from a thermodynamic standpoint, and if you’re drinking bottled water, that’s one more consideration of how green this strategy is.

(and Jennifer also finds herself under investigation by the unit cops, for using “Watts per hour”)

This is reminiscent of the hydrogen economy that was touted a few years back, but about which we haven’t heard much lately. Why? One reason is that it’s not green, It sounds green, but that’s just because you’ve slapped a green-label veneer on something, but when you peel back that layer you find some very un-green components. When all is said and done, this is a little like money laundering — you’re just making it harder to trace the true source.

But there is a true source. The energy we use on this planet ultimately comes from one of two places: the sun, or radioactive materials leftover from the planet’s formation (which came from another sun). You have to trace your generation back to one of those, somehow. If that audit hits a “fossil fuel” source at any point, then your source isn’t green (assuming “green” here refers to sources that do not include sequestered Carbon). Anything involving food runs into issues of fertilization and transportation — even driving to the store to buy it — and packaging, all of which typically involve unsavory sources of energy from a “green” perspective.

So my objection is this: using “Green” makes it sound like you are having no or minimal impact on the environment, and it can be misleading. It can make you focus on a very small reduction in emissions, while distracting from the very large amount that’s already there, and other much more significant improvements that could be made. Be a little skeptical of the users of “Green” and its synonyms, because they may just be feeding you an advertising gimmick.

———

Update (more space here than in the comments section. It’s good to be the king):

I don’t necessarily disagree with the comments from BlackGriffen and Jennifer — as I said, harnessing otherwise wasted energy is fine. But consider this scenario:

Someone (Not Jennifer, because I never meant to pick on her) is very impressed by such a gym that she decides to join up, and figures, “What the heck, it’s only a half mile out of my way on my commute. Just an extra mile round trip!” Now, Not Jennifer is a beast in the gym and works out for two hours a day and can manage 100W that whole time (along with 100% efficiency), and works out 25 days a month. That’s 200Whr x 25 = 5kWh of electricity generated (saving the gym owner perhaps 50 cents). And it’s only a mile extra on the commute, so that’s 25 miles of driving, and Not Jennifer drives a Prius, too, so that’s only a half gallon of gas a month. Unfortunately a gallon of gas contains more than 30 kWh of energy. So we’ve traded in excess of 15 kWh of fossil fuel for 5 kWh of human-generated energy in this (admittedly contrived, but certainly plausible) scenario.

That’s my worry — that things like this will happen, because the whole picture isn’t being considered. Yes, education is important. Human power is pretty feeble compared to the machines we have around us, which is why we have them around us. But I have trepidation about tagging things as “green” that may not be, and may not only foster a sense of community but a sense of “I’ve done my part” when that’s not really the case.

———

Update II: Some numbers at Dot Physics and Hamiltonian Function for kinetic plates and humans, respectively.