content: I think that we should be doing what we can where can do it. Every city has available roof space for solar collectors. As we shift to more electric vehicles I bet they will eventually come with photo voltaic surfaces. I understand that most commercial vehicles average about 100 miles use per day. If all of those trucks had battery packs that charged all day and were changed out each night with fully charged batteries off the shelf technology could take them out of the petroleum use pool. A local beer distributor recently put enough solar collectors on its warehouse roofs to power its refrigeration needs. Just look around at all of the roof space over gas station pump areas. Most of those stations could probably do the same thing. It costs a little more up front but will pay off in the long run.