Need help to solve bearing problem where shaft won't turn smoothly (practical)?
In terms of speeding up the process, the time it takes will depend solely on the amount of power going to your heater or however you are going to do itWith that said, if the heater is hooked directly up to the panel (given that the panel outputs the same voltage as the heater), you will be waiting for the power as it is developed by the panelIn another method, you could have a correctly sized battery that would store this power as the panel makes it, which would result in the power being generated and stored even when you are not using the cookerThe power would be there when you need it rather than waiting on the panel to make itThis can become expensive because a type of charge controller is needed.
It isn't clear if the shaft if vertical or horizontal but in either case is there any thrust or axial loading on the shaft In the case of a vertical shaft just the weight of the shaft could impose a thrust load on the bearings and if they are not designed to handle any thrust that can put them in a bind.