This Is Still A Stupid Idea

I probably have posted on the electricity generating speed bump more times than it deserves, but Glen Reynolds linked this story and I am seeing it linked uncritically all over.  Here was the email I dashed off to Instapundit:

The speed bump / power device at the Burger King in New Jersey is the silliest technology I have ever seen and I am amazed that so many people praise it or write uncritically that it provides free power.  Energy is never free, it comes from somewhere.  In this case, the energy is actually stolen from the car.  The electricity power produced is equal to or less than the extra power the car has to expend going over the bump.

This electricity might be "free" if it is used where cars are braking anyway, say on a long down ramp in a parking garage, or on a suburban street or school zone where speed bumps already exist.  But the Burger King example, and in fact most of the examples I have seen of this installation, are just vampiric theft, very similar to what the US Government does in many of its programs, creating a large benefit for a single user and hoping that distributing the costs in small chunks across a wide number of people makes these costs invisible.

I wrote more about the technology here.


  1. anon at work:

    It has to be less and the rest appears as heat.

  2. Rob Sama:

    I emailed him as well. Told him it was theft of mechanical energy from the car. He should know better.

  3. Jens Fiederer:

    At least the article you linked DOES mention that concern:

    "New Energy's MotionPowerâ„¢ technology is designed to be installed in locations where hybrid, next-generation electrical, and conventional fuels-driven vehicles decelerate or stop, thus ensuring that vehicles are not 'robbed' of energy they would otherwise use to accelerate. Instead, MotionPowerâ„¢ devices actually assist vehicles in slowing down, and in the process of doing so, capture the vehicles' motion energy before it is lost as brake heat, and creatively convert that energy into clean 'green' electricity. "

    However, it seems to me to be WRONG. Yes, it actually might be helpful with "conventional fuels-driven vehicles", but if I understand correctly it absolutely WOULD rob hybrid (or any other car that uses regenerative braking rather than just "brake heat") vehicles.

  4. LoneSnark:

    Yes, but there are so few regenerative-braking vehicles they can largely be discounted.

    That said, even if they were installed in a smart location (a stop sign at the bottom of an off-ramp) I still question if they would ever pay for themselves, since the energy taken from each car cannot be very much without harming safety, which normal speedbumps do.

  5. Highway:

    Actually, given proper driving behavior, there is NO time where any speed bump or hump installation would 'assist' in slowing down vehicles. Even with a bump shaped like that, drivers should slow down to the safe speed to traverse the device *before* they engage the device. People don't go faster approaching a device thinking that the device will help slow them down. They slow down in advance of the device and then glide over it. So the energy 'robbed' from the vehicle is added to the energy to get the vehicle back to the desired speed after the bump, not subtracted from the kinetic energy prior to the bump (which they argue is wasted as heat by the brakes anyway).

  6. Larry Sheldon:

    This is but a minor fraud in a vast desert of frauds.

    These superduper 250 MPG cars that need to be recharged at 30 miles (or what ever the right numbers are--where are they going to plug in? The block heater plug in the parking lot? Who is going to pay for that? Maybe an extension cord from the office dropped out a windw? In howling sub zero weather. Add a log to the heating system george.

  7. A Friend:

    Couldn't this just be used as way to "impose" regenerative braking on cars that don't otherwise have it? Just suck some kinetic energy from them as they approach a stop and convert to electricity. I see a future where every stop sign has a series of hoses full of water under the pavement that you drive over, and the pressure created is used to generate some electricity. Wouldn't be a lot, but it's similar to giving them all regen brakes. Or, cooler, some kind of magnetic field slow down device, like a reverse mass driver. I bet on low speed roads you could recapture a good deal of the energy needed to move the car. (At high speeds it is lost to air resistance.) Of course, in front of my house, I'd like the chain arrestor from an aircraft carrier. Going 45 mph in front of my house? Not anymore, you're not!

  8. PJ:

    There is another aspect to this which should be noted, which is another flaw in 'green' concepts that attempt to save energy ... the capital cost vs energy recapture.
    How much does this cost and how much energy does it collect?

    It seems like a lot of cost mechanical materials to recover a tiny amount of useful energy. The $50,000 cost was bandied about. $50,000 for a speed bump? To get maybe 4-10kw at certain times.
    $50k buys a lot of generating capacity: That's 15-20kwh of nuclear plant or 20-30kwh of a coal or gas plant.
    So you could buy into a piece of a real power plant, spend $100 for asphalt for a plain ol' speed bump,
    and have money left over for planting a few trees and being really green.

    I can see why Coyote blogger hates it - it's a great analogy for every wasteful vampiric Govt program!
    Create a large expensive contraption/bureaucracy, make it steal from one source (of money/energy) to provide a tiny benefit (of money/energy) for some other 'nice' purpose, and pretend you are doing good by ignoring
    the costs/expenses you created.

  9. Rick Summerson:

    I have read this website for years now and enjoy it quite a bit. I am an electronics engineer and have read enough of your previous blogs to know you have a very good understanding of the long established rules of thermodynamics. This system from gasoline to electricity would astonish me if the total conversion efficiency exceeded 10%. I am 50 this year and still can't believe the general public is so ignorant of basic physics. The biggest problem I have with your website is that no matter how much I really believe in being a true libertarian I find it nearly impossible to believe that if I was in charge I couldn't control everything better. I heard a good quote from a local college economics professor where he says that he starts his semester of 25 or so students by telling the entire class they couldn't produce a single pizza. It's quite similar to the attempt of one person to make a pencil. In the end he produces a pencil, but can he make it for a nickel?