Crackpot energy scheme

Boomberg reports: “Paris Marathon to Harvest Runners’ Energy With Pavegen Tiles”:

Paris Marathon organizers will lay energy-harvesting tiles across the course on Sunday to ensure not all the effort expended by the race’s 40,000 runners goes to waste.

The goal is to get their cost down to $76 per tile.

Seriously, has anyone thought for 1 second about whether this thing is economically viable? As hare-brained ideas go, this is up there with flywheels on buses, and laptops powered by static cycles. Because hey, laptops are so easy to use when you’re pedalling a cycle, mobile or otherwise. Not!

Of course, whenever these truly insane schemes are pumped up, the promoters always talk about how they’re low-carbon, environmentally clean, gets people fit, and harnesses power that would have otherwise gone to waste.

OK, the get fit bit is usually true. The rest of it is usually arrant nonsense. The first glaring problem is that, economically, they make no sense. The second problem is that there’s no such thing as free energy … Laws Of Thermodynamics … you know, reality as it actually exists and stuff like that. In order to power these machines, people power them with mechanical energy. But that energy isn’t free. It has to come from somewhere. Where? From calories in food that the people eat. It gets worse, though. Inconveniently, converting energy from one source to another inevitably involves entropy. In other words, the conversion process is inefficient to a greater or lesser extent, and energy is wasted. Given it’s an inviolable law of physics which no engineer can overcome no matter how clever, that inevitably leads engineers to devise machines in such a way that the waste is kept to a minimum as technology and cost considerations allow. Since eating, digesting, and processing food consumes a lot of energy, and mechanical energy generated by humans creates heat (perhaps it hasn’t escaped your attention that you get hot when you exercise), it ought to be apparent that powering stuff by using human energy is never going to make sense. It might be fun and a novelty worthy of some entertainment value.

Rant over.


About mcturra2000

Computer programmer living in Scotland.
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4 Responses to Crackpot energy scheme

  1. It’s not as mad as that from a pure energy standpoint. Marathon running per se is much more energy wasteful than just the race – the training uses many times more calories than the runner expends in the race itself. However excercise is worth the food use for each person.

    What the organisers probably haven’t twigged is that the scheme will slow the runners down so there will be no hope of any record time.

    I hope they extend the concept to the Tour de France and fit an energy harvesting system to the bike wheels. Let’s call them, er, dynamos.
    Oh hang on, serious cyclists stopped using them because it slows them down.

  2. Sidekick says:

    Also how much energy is used to make these tiles. It’s like hybrid cars, you use so much carbon in just making the thing, it isn’t better for the environment.

  3. Charles Hang says:

    First of all, you’re probably right that this idea is uneconomical, in the sense that the investment in paying for and installing the tiles isn’t going to be recouped by the electricity generated.

    That said, I think you (unintentionally) set up a strawman with your comments about the Laws of Thermodynamics (presumably, you’re referring to the Second Law about entropy). It’s not as if the marathoners wouldn’t be using energy anyway; this just makes it possible to recoup some of the energy the runners are already exerting into the pavement via the tiles. Saving energy by doing so doesn’t violate the Laws of Thermodynamics any more than regenerative braking or combined cycle power plants do.

    Of course, if the tiles slow the runners down, as a previous comment says they do, then that offers a good reason for not using them, since that takes away from the point of a marathon. However, that’s totally removed from any scientific basis why this idea won’t work.

    Put another way, there are a couple of perfectly legitimate reasons to have this project:

    1/ The tiles are going to be installed long-term, in which case they could recoup their investment from all of the Parisians walking over them in the future.

    2/ This is some sort of pilot project in the process of improving the technology.

    I think it’s a fallacy on the part of some people to say that renewable energy shouldn’t be deployed just because it isn’t immediately economical. Even if, say, a solar power system is more expensive than fossil fuels, it still makes sense to build some in the process of improving them, just as it made sense to build a room size computer decades ago to do basic computations in the process of developing the laptop I’m using the write this post.

  4. shinygoldcar says:

    The Bloomberg article is light on technical detail, but I don’t think we want to get bogged down in a technical discussion anyway.
    There is always a potential to recover “wasted” energy, that is energy that does work that is not useful. For example, regenerative braking recovers unwanted kinetic energy and charges the battery, otherwise that energy would just make your brakes hot, which serves no useful purpose to the driver/rider. But you don’t want to increase energy consumption, just recover the energy that gets thrown away.
    My guess is these tiles are slightly more flexible than hard running surfaces, therefore some energy is used to deform these tiles. I think the runner uses more energy, so will get tired more quickly. Great if you want to get fit or you are training. Maybe not what you want in a competitive race, but as long as it affects everyone equally at least it’s fair. However, judging by the image in the article, it looks like the runners can just avoid the tiles!

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