Don't expect much from bicycle-powered electricity

February 01, 2011

I'm all in favor of carbon-free electricity, and I applaud the Columbia Athletic Club's decision to install generators on its stationary exercise bikes. ("Gym's exercise bikes generate electricity," Jan. 31) But their math is a bit suspect.

Twenty such bikes used 20 times per week (presumably for one hour each time) will indeed generate about 3,600 kilowatt-hours of power over the course of a year, if each bike user produces about 175 watts while pedaling. Those are not unreasonable assumptions.

But that will not be enough to "light 72 homes for a month," unless we can "light" a home for 69 watts on average. In the new world to come where all lighting is from either fluorescent or LED bulbs, that might actually be achievable, but it is hardly typical now.

A more reasonable comparison is that a typical household uses on average something like 1 kilowatt continuously, or 500-1,000 kilowatt-hours per month. So the Columbia exercise bikes generate in total, on a day to day basis, about half the electricity for an average home, and an even smaller fraction of the electricity used by the Athletic Club itself. That is, there won't be any human-powered electricity going into the grid, and even the reduction in energy costs for the club will be small.

Most of us are in favor of "green" solutions to our energy needs, but in evaluating any new technology, we need to be honest and smart about what we can actually expect and not get carried away by the hype.

George Kaplan, Colora

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