Fortunately, as alternators work at relatively low speed compared to a generator, ie the old style car Dynamo D.C. generators, ratios are more associated with your own strength. If the tire can be removed to run a belt from the rim you can even get output on a simple direct drive from rim to alternator. One can even get a friction drive without taking the tire off at all, though this is not so easy to drive. A 100 watt Solar panel will probably only average 2 amps at best even if it is rated three times or more higher, due to sun angles, latitude, and cloud cover. Whereas a bike/alternator can output 30 to 50 amps or even even more. The output depends on your strength and endurance, the more reason to live in a small community. Output can be gotten at any time of the day and in any location (cave, capsule, survival shelter etc.), irrespective of sun, wind, or water.
If we accept 12 volts D.C. as a standard then focus from that for all the other considerations, I cannot think of a cheaper way, a safer way, an easier way, a more flexible way, a more readily available way, or a more reliable way to generate electricity. I do have an exercise bike driving a car alternator, it is a proven thing too, able to bring a good charge to the batteries in the dead of night. (Its a hell journey to the "Little House" in the dead of night without a lamp to guide you back.) One wag has suggested a guide rope for returnees as it would save the batteries.
Testimonial by Darryl.