"It Just Won't Work".
Google paid several engineers to try and find a way that renewable energy could be made to work.
Their conclusion: It won't.....It cannot be made to work. Period.
All renewables, those we know and those we can envision barely, at best, produce more energy that what is required to produce the device. Every Single One. Every Time.
This is Google, which so very much wants to find a way to power humanity on Magic Fairy Dust and Unicorn Farts in order to save the planet from humanity and evil Carbon Dioxide....
their conclusion: Ain't Gonna Happen.