That is already a thing and it’s called concentrated solar power. Basically aim a shit load of mirrors at a target to heat it, run some working fluid through the target and use that to make steam to turn a turbine. There are a few power plants that use it but in general it has been more finicky and disruptive to the local environment than traditional PV panels would be.

My understanding is that valve says publishers can’t sell their games steam keys cheaper on other platforms but can charge whatever they want if steam is not the one providing the download. Network infrastructure isn’t free and if steam is the one actually facilitating the download they get to take their share.