In the US, there is a slowly-growing trend of covering parking lots with solar panels, rather than buildings. You can put up very cheap i-beans + corrugated metal structures with the added benefit of shading cars. It doesn't work everywhere, but in sunny - and especially dry - regions, it's great.

edit: I could see this working well in AUS and USA because we've got lots of space and sun. Might be harder in Europe and northern Asian regions