Have you ever wondered how much power a human can produce? I did one day while I was exercising. It occurred to me that if I could capture the energy I was expending while I was exercising I could get fit and save money. Of course this would only be useful if I was going to be generating a reasonable amount of power so it was time to do some research.

The first bit of information I found was about people at a house warming party. The host was advised to turn down the heating by a couple of degrees if the house was going to be full because each guest generates about the same amount of heat as a one bar electric fire. I felt this was unlikely because each bar on an electric fire puts out roughly 1KW of heat – a rather large amount for a person I felt. Having experienced first hand the way a house (actually a flat) warms up when packed with people I was sure that humans put out a fairly significant amount of power though – my guess was around 100W which I later confirmed was roughly right.

This didn’t help all that much though because capturing the heat produced by a person and putting it to good use generating electricity would be difficult. Very few devices can work on small temperature gradients and those that can aren’t very efficient. What I needed to find out was how much mechanical power a person can generate. After much searching I found this page on human powered vehicles which includes a graph showing how much power a person can generate.

The average healthy person can generate about 75W for 8 hours before becoming exhausted. If you want more power over a shorter period of time you could generate about 200W for an hour. A top class athlete could generate around 300W for 8 hours and can manage 350w for an hour. If you are generating electricity using top class athletes you are best off letting them work for 8 hours.

So, assuming you are an average person, what can you do with your 75W. Not a lot really. You could light a standard light bulb but I would recommend using energy saving bulbs. Most computers are pretty much out of the question. You could probably power a laptop in energy saving mode. Alternatively you could power a decent sized radio but forget that room dominator.

Considering the small amount of power I could generate I gave up on the idea of trying to capture it. Oh well, another good idea consigned to the scrap heap.