With bulky solar panels being not only obtrusive but also pretty expensive, even if Wal-Mart did buy some, a group of engineers at the University of Texas at Austin have a better idea.  Spray-on solar cells. Chemical engineers at Austin's univerity are working on developing a spray-on version of solar cells that would energize surfaces and take the place of the bulky solar panels.  Here's wishing the group much success and we can't...