Latest "Green" Power Generation — Your Feet

gbjbaanb writes "Remember those ideas that suggested hooking gym machines to the power grid? Well, the Times is reporting that something like this to harness free energy is about to become a reality — the footfall of trudging shoppers is to become the latest source of emission-free energy. 'Engineers who have modelled the effects of the technology at Victoria Underground station in central London have calculated that the 34,000 travellers passing through every hour could power 6,500 lightbulbs. ... The plans for heel-strike generation follow successful trials last year at a bridge in the Midlands where generators converted energy from trains passing above into electricity powering a flood detector.' Possibly the most important thing for the readership is at the end: 'There could also be a range of domestic uses, for example powering iPods by plugging them into batteries placed in the owners' heels, using technology which is already available.' Obviously you'd have to get up and walk around, but, as they say, it's the thought that counts."

Re:Waste of resources

[dougmc]

I may agree that extracting energy from humans like this isn't practical, but your figures are wrong.

A world-class bike sprinter can put out 1500-2000 watts for a short period of time, perhaps a minute or so [wikipedia.org]. Lance Armstrong can put out about 500 watts for 30 minutes or so [pezcyclingnews.com], and a somewhat lesser amount for many hours.

I'm a pretty weak pedaler, but I can put out about 100 watts for an hour or so without too much trouble.

Re:There is no free lunch

[gbjbaanb]

by people walking on them, it will make it harder to walk

I remember some adverts for training shoes that had fluid capsules inside them to reduce stresses on your joints (or something, probably just marketing). People bought them but didn't complain they were difficult to walk in. If the generation systems are of the same order, then I can't see a problem.

I imagine it would cost a fair bit to install, but there's paths everywhere, whereas solar panels have a limited amount of area they can be installed on. Also, these wouldn't require the noxious chemicals solar panels are made of, and wouldn't require as much maintenance (I think).

For other areas, I thought bridges etc had to have soem 'squidginess' to them, or the traffic riding on them would quickly shake it to bits. As the article said, this principle also applies to antennas that wave in the wind, so its not just going to be used in every pavement in the world.

Re:There is no free lunch

[Anonymous Coward]

But as for free energy -- this is not it. By putting generators in the ground that are moved by people walking on them, it will make it harder to walk. I don't know the specifics, but I'm guessing that parts of the floor will move up and down a little as people walk on it, probably a few milimeters. It might be somewhat akin to walking on sand -- and I have to wonder what it would do to a wheelchair.

It shouldn't make it harder to walk at all; at least not noticeably. If piezoelectrics are used, the total deflection would be hundredths of of a millimeter, perhaps less.

Re:There is no free lunch

[sentientbeing]

Youre right.

I remember this being debunked using basic energy estimates and calculations last year by The Register.

http://www.theregister.co.uk/2007/07/30/all_the_power_they_would_ever_need/ [theregister.co.uk]

Re:There is no free lunch

[smaddox]

Also, these wouldn't require the noxious chemicals solar panels are made of, and wouldn't require as much maintenance (I think).

Noxious chemicals?

Silicon, and trace amounts of boron and phosphorous are noxious? You need to go back to chemistry class. Not only is silicon one of the most abundant elements on earth, it is one of the least harmful to humans.

Also, solar cells don't really require maintenance. You would want to clean them occasionally to get optimal power, but that involves spraying them off with a hose. That is the beauty of photovoltaics - there are no moving parts to break.

Re:There is no free lunch

[TubeSteak]

I remember some adverts for training shoes that had fluid capsules inside them to reduce stresses on your joints (or something, probably just marketing). People bought them but didn't complain they were difficult to walk in. If the generation systems are of the same order, then I can't see a problem.

I read an article (I can't find it, but I'm sure someone will pull it up) where they discussed the issues around cushioning in shoes.

What they found is that your body is used to a certain 'feel' from the ground when you walk. It turns out that more cushioning = more stress on your joints, because your body notices the lack of pressure & compensates with harder heel strikes.

The article tied all this into walking barefoot and some shoes that were about as close to walking barefoot as you can get.

Anyways, the moral of the story is that you do work harder with cushioned shoes and they're not good for the health of your feet & lower joints.

Re:There is no free lunch

[maxume]

Probably:

http://nymag.com/health/features/46213/ [nymag.com]

Re:There is no free lunch

[gbjbaanb]

Me? You're the one that needs to go back to eco-warrior class.

IIRC it was cadmium used in the manufacture that made solar cells not as green as they could be.


A quick google says
However there are many environmentalists and some scientists that are worried about the potential negative impact of solar cells (photovoltaic technology). This is because manufacturing process of photovoltaic cells needs toxic metals such as mercury, lead and cadmium

Still, I think its better than coal-fired power, but don't think any green energy generation is the perfect answer to all problems.

Re:There is no free lunch

[Tweenk]

Commercial PV cells are not made of doped silicon as you seem to presume. They are made of cadmium telluride. This thing IS noxious: Wikipedia is your friend. [wikipedia.org] Silicon cells are only used in laboratories, because for now they are much more expensive.

Additionally, silicon is abundant on Earth, but it doesn't mean it's cheap. Obtaining semiconductor grade silicon from sand or silicates is not a trivial process, and this is why it's still very expensive despite its broad usage.

Re:How about harness doors?

[isj]

Already done in the comic Gaston [wikipedia.org], where he invented such a device which could press the juice from 4 oranges, grind 30g coffee and stamp 5 letters. His coworkers were not pleased.