That is pretty nifty. But I have to agree with
Baraka_Guru about utilizing solar and wind energy, but for different reasons. We are developing technology that can potentially yield solar power with 50% efficiency, and the best part is the new technology would be cheaper than roofing shingles. I wish I had my sources, as I am recalling information researched over two years ago in a proposal for my university to invest in solar energy.
3.5-million-US$? PFFT---got that in my money clip. Definitely economic for building projects, though.