Why is This Called "Green" Rather than "Theft"

From Greenlaunches.com (via Engadget) comes a technology that I have written about before to leech energy from cars to power buildings:


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.


  1. feeblemind:

    Yes indeed, I saw the same problem with the scheme half-way through the read and I was no more than an average physics student. I believe it was John Stossel who once wrote that journalists should not be allowed to report on the topics of science or economics because they know nothing about either subject.

  2. DrTorch:

    You summarized these issues nicely. The cost to the ICE of the car, the potential for some benefit if the car was braking anyway.

    I am surprised that a business guy skipped the obvious: what is the cost (in dollars and energy consumption) to build such a Rube Goldberg contraption!? That doesn't look cheap, especially retro-fitting paved surfaces. In addition you need to manufacture generators, power lines, and install (power consuming) switches that alternate the power source to the grid when no-one is driving over your plates. I'm skeptical you could ever break even on such a contraption.

  3. Dan Smith:

    Good post! Here's an example of the same kind of mindless green thinking from the state of Minnesota. We have an annual State Fair that attracts thousands each summer just before Labor Day. A couple of years ago, one of the local TV stations decided to go green publicly. During the fair they do their broadscast news from the fairgrounds and they devised a way to generate electricity by having volunteer fairgoers ride stationary bikes and the energy is stored on batteries for use during the broadcast. I found the resulting crowing about green news to be a bit much. With a strong background in science (BA in Biology and MD)I found the calculations of energy conversion not to be difficult. I won't bore you with the details, but I still have them on file. The bottom line was that the cost of the "green" electricity was far higher than what it would have cost to either pay for power off the grid or run a diesel generator. I didn't have enough data to compare CO2 production with the power company, but my figures showed less CO2 production from the diesel, probably because a generator is more efficient compared to a human burning stored carbohydrate and pedalling. I also did not factor in the CO2 cost of the people travelling to the fair or laundering their sweaty clothes, but those would have increased CO2 production by the cyclists. When I wrote a letter to a reporter at the station about my findings, I got a lukewarm response and nothing was reported.

  4. Tim:

    There is a place where this would make sense -- you need to install these in lieu of speedbumps. So the losses to the car are recovered, or partially recovered, instead of lost.

    Of course, doing that you are open to questions about the point of traffic calming devices in the first place.....

  5. Anon:

    Dan Smith:

    You can repeat the calculations for solar cells if you'd like and get the same result.

    Even with subsidies, it is cheaper to go off the grid using Honda and Exxon. You can even sell electricity back to the grid at a loss, just like the solar junkies.

  6. Me:

    Note that the idea to furnish natural stopping points (like garages) with such a system is worth evangelizing. Garages probably won't net sufficient numbers of such events, but try going for the niche currently occupied by that ugly disease of out streets and parking lots called a 'speedbump' (same argument for theft of momentum holds for the concrete implementation, but I'd feel slightly happier if that momentum was used for some good instead of being wasted).

  7. rob sama:

    Before refrigeration, people used salt to preserve their food. I doubt today's anti-salt activists would look kindly upon that practice tho.

  8. brazil84:

    "what is the cost (in dollars and energy consumption) to build such a Rube Goldberg contraption!? That doesn’t look cheap, especially retro-fitting paved surfaces. In addition you need to manufacture generators, power lines, and install (power consuming) switches that alternate the power source to the grid when no-one is driving over your plates."

    Also, I imagine you will have to tear up the street in order to repair these things when they fail.

    "I’m skeptical you could ever break even on such a contraption."

    I'm skeptical too. It would appear to me that the main value lies in being able to claim you are green.

  9. Dr. T:

    Did everyone notice the key phrase in the PR blurb: "power the checkouts". Not power the mall or power the stores, just the checkouts, and that's only when many cars drive into the garage.

    This system must have cost a fortune. I cannot imagine that it will ever break even due to the initial capital costs plus ongoing maintenance costs. I'll bet the breakdown frequency will exceed that of cheaply built escalators.

    The people that sell systems like this remind me of the old-time snake oil salesmen (or the current purveyors of quackery). The sales pitch is slick but the product causes more harm than help.

  10. Max:

    Sorry, I have to comment, because actually dynamic branking is a loaded word. Usually, you should know that, dynamic braking is associated with trains that brake by using a chopper to translate electric energy into thermal energy. They create energy by burning energy over a resistance. So, no, actually dynamic braking is one of the most wasteful techniques known to mobile machines.
    There is a quite strong difference between dynamic braking and regenerative branking, which is different as described above =)

  11. James H:

    It's not "theft", it is a redistribution of energy. It's not "fair" that you have all of this energy, and the store can't use it to run the registers as you drive by.

  12. Douglas2:

    The fridge family is not just transferring the load from their refrigerator to their freezer. If you look at energy consumption and temperature difference, your average chest freezer is far better than even the latest greenest energy-star refrigerator.
    This is partly due to usage patterns, we just don't open that chest freezer quite as often as we open the refrigerator in our kitchen.
    It is also partly due to gravity, because when we open a kitchen fridge or freezer all of the cold air dumps out onto the floor -- but with a chest freezer, aside from the air disturbed by the suction and turbulance of opening the thing, the cold air still gravitates to the lowest place, which is still in the freezer.
    If you don't believe me search out the "off-grid" blogs and messageboards. People who are trying to subsist with solar, wind, storage batteries, and inverters are converting chest freezers into fridges by plugging them into 120V-AC switching thermostats. Crude, but apparently effective. I can't help thinking that they've never heard of a paraffin/kerosene fridge, however. Surely they could run one on something carbon-free like whale-oil.
    Part of no-fridge family's efficiency will also be mindset. When we moved from Europe to Tennessee we bought a big American side-by-side fridge because, um, I guess my wife wanted one. I took to rinsing empty milk bottles, filling them with water, and using them to fill the empty space/replace air/increase thermal-mass. It was part of the experience of living in an exotic place, and all that. In the home we are in now we are using what was sold to us as a "dorm fridge" which is still larger than the refrigerator compartment of our fridge back home, and a chest freezer. We aren't big on Sam's-Club sized condiment bottles, however. And if you are going to use your eggs in a few days, they don't need to be refrigerated if your house is cool anyway. And the whole case of cola doesn't need to be in the fridge at the same time.

  13. Fred Z:

    Thermodynamics and the laws of conservation of energy: Lies - all lies.

  14. epobirs:

    The 'Office Space' scam has roots in reality. A number of people got away with this in the 60s before and couldn't be prosecuted without the banks admitting they'd been cumulatively pocketing vast sums of their clients' money. Changes in their accounting method to make things more honest eliminated the loopholes that were being exploited, applying the philosophical basis that if we don't own the scam, the scam don't run.

    The off-gridders make lots of claim but don't stand up to scrutiny that includes the criterion 'what is your time worth?' My mother can remember deliveries from the horse-drawn ice wagon for the family icebox (back when it was really an icebox) when she was a child but would never go back. I for one find it a major mark of civilizational improvement that I can have a well stocked refridgerator with a good variety of food available at my whim. I'd rather designate hippies as a food group than give that up.

  15. Alex:

    What about putting these in deacceleration lanes? Sometimes you have to drop from 70 to 20 mph on that one little stretch, which I imagine converts a lot of energy to heat (I could calculate it, but it would be pointless because I don't know how efficient these bump things are).

  16. Florian:

    The phrase "30kw of green energy in one hour " doesn't make any sense anyway.

    Either it is "30kW power" or "30kWh energy per hour".

  17. Ryder:

    This is so funny… but there is so much more to tell. I was attending the 31st annual “Health and Harmony Festival” in the heart of Sonoma County, California (don’t ask how I got there…)

    Of course this is dominated by Obama worship, green politics, vegitarianism…. and of course getting high and dancing to live music as a means to “change the world” after you are done buying your $30 tie dye shirt.

    On the stage, the MC of the show, between musical acts, asked the crowd of thousands… “How many of you have cell phones!?” and then offered this bit of trivial “knowledge”: “Where is the best place to recharge your phone… in your car, or at home?”

    Of course she advised the stoned masses that they should charge their phones in their cars… because “there is this little generator in there, which is running anyway, so you should use the free energy coming from it!”


    A dancing hippie stepped on my lower lip as my jaw dropped. A woman dressed as a sunflower told her car driving “earth first” fan club to use gasoline to charge their phones.

    My plan is to get an electric car without batteries, and tow a gas powered generator behind it to power the thing directly. That way I get to claim that I am green, AND use the commute lanes for being so environmentally friendly.

    Why is it that support for the environment relies so heavily on stupidity?