My thoughts are: Sure you can generate electricity with a bike. The real question is should you?
What is you purpose for generating the electricity in such a manner? Is it to help the planet? If so, you may be better off going solar or sticking to the grid. If it's just a fun experiment, go for it. If you live off the grid, again, solar is a good choice. It's almost too easy to hook up an alternator to a small gasoline engine (like a salvaged lawn mower engine) to produce far more power than pedaling can produce.
One good scenario for having a bike generator would be if you already have a battery bank that is charged via other means and you just want some exercise. You might could also use it to charge a small battery bank for small applications (like maybe exterior lights or something). You could also rig a bike to a washing machine so you can wash your clothes with calories via human exertion lol.
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