Ask the EcoGeek: Muscle Power


Instead of solar and wind power to supply to your own house - which are both weather dependent - has anyone thought about systems that might require some actual work, but provide a usable amount of power?

I was thinking, what if each member of my family carried a 40lb bag up 3 floors an hung it on a hook that was connected to a generator; would an effort like that actually provide a significant amount of energy? Just a thought.
Regards,
Jens, London

Oh Jens...you don't even know what you've done! Your question is totally a word problem from a physics exam. And as much as this will likely frighten most people reading this, I'm going to treat it as such.If 120 lbs is lifted thirty feet and then allowed them to drop slowly over twelve hours, how much energy will be produced?
120 lbs * 30 ft = 3600 ft/lbs = 4880 joules = 1.356 watt hours / 12 hours = 0.113 watts.

So, in answer to your question, no, that would not provide a significant amount of electricity. In fact, in order to power one 60 watt equivalent CFL for twelve hours, each member of your family would have to march up the stairs about ten times.

But that doesn't mean that you don't have an excellent point. Every person is a magical little energy factory. Whataburgers go in...watt hours come out, and it is possible to harness that energy.

Some schemes in converting muscle power to electric power even seem pretty intelligent. A gym in Hong Kong has hooked its treadmills to a battery bank, using the energy of its clients to power the lights. A subway in Japan harnesses the energy used by people walking through turnstiles to power lights. And we've all seen various gadgets that can be shaken, squeezed, cranked or yanked to generate the juice that makes them work.

But a more personal and powerful option for a muscle-powered home is a pedal generator. Basically, it's just your average exercise bike, except there's a generator on the inside. The maximum output for a toned adult would be about 500 watts, but a sustainable level for someone like me (who's eaten his share of Whataburgers) is more like 150 watts. Amazingly, this would be enough to power both of my laptops, two CFL light bulbs and my cell phone charger for as long as I kept pedaling.

There are two problems though. First, no one can pedal forever. And second, they're not yet selling pedal generators at your local hardware store. But if you can get your hands on one, like the $230 pedal-a-watt bike-to-generator conversion kit, you could easily lower your electric bills, or charge an emergency backup battery, and become a healthier EcoGeek at the same time.

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