DaveC426913 said:
I think the most obvious and very short answer is that air conditioners are very inefficient converters. They take a LOT of power and mechanism to cool just a small amount.
A decent air conditioner will run an EER of between 11 and 13. Call it 12. That is 12 BTU/hour cooling per watt of input power.
Human power output can vary. Peak mechanical power output in the 300 to 400 watt neighborhood is possible. But 100 watts is more accurate for sustained output. If we hook a 100% efficient generator to the treadmill, that means that we can get 1200 BTU / hour of cooling.
How many watts of cooling is that?
Google said:
1 btu per hour =
0.29307107 watts
So from our 100 watts of input power we are getting ##1200 \times 0.29307107 = 350## watts of output cooling.
That is not a "very inefficient converter".
However, the human body is not a particularly efficient machine. A ball park figure is 25%. In order to generate those 100 watts of output mechanical energy, we burn 400 watts of food energy and produce at least 300 watts of waste heat to be dumped via the 350 watts of air conditioning.
That sounds pretty darned close to break even in terms of energy.
In terms of economics, it is a non-starter. At ten cents per kwh, you are buying yourself a penny per hour. $7.20 / month if you run the thing 24/7. Then you have to worry about condensate, cleaning, maintenance, freon leakage, initial expense and the fact that the resistance is not as smooth as something like magnetic eddy currents. And you still have to plug the thing in because goodness knows the customers will want their animated LED display and fancy programs.
The exercise bike in my home cost about $350 when I bought it. Google says $500 or so today. It dumps energy with magnetic eddy currents and has a little one or two amp power supply to run the LED display and manipulate the magnets.