Constraints for the prototype

• Not dangerous (no unprotected flywheel with spokes) if it is to be left in a school

• Be within my time budget (not big for the moment)

frame
   either an old stationary cycle where I could fit a generator, or  a few soldered tubes, a seat and a handle bar. We need a handle bar to properly cycle.

generator
   https://www.k-tor.com/shop/generators/power-box-50/
   this pedal powered generator can directly charge a 12V lead battery, it is the simplest solution
battery
   classic car lead battery
greenhouse

There the greenhouse itself, Ideally I would take a proper one with real glass, but it's too big an investment before being sure the concept works.

lighting

Concerning the LED system it looks like I need to have different kind of leds one to make the plants grow and another to get flowers.

water

A system to water the plant may be required, otherwise a human intervention is needed.
I don't think I will use hydroponics, but it remains an option.

heating

I suppose a heating system is required to prevent the plants from freezing (and maybe to better simulate the summer)