Why can't we use electric alternators in space to produce energy?

When you start withdrawing energy from the alternator its rpm will start reducing,in order to maintain that you reinforce it with solar panel. Now again you can only withdraw only that quantity of energy that you input to the system from the solar panel,that means only source of energy is the solar panel so why not to directly supply the Solar panel energy which can sent to earth in form of power beam and no need of the stadium size alternator.If the energy is to come from the solar panel then why put such huge panel into the space better install those panel on earth surface and reduce the installation and operation cost.thks