Solar power has the highest power density among all renewable energies, so we should certainly be devoting a great deal of research into how best to capture and use that power. Being that solar electric power cells generally deliver their power in the form of DC current, as opposed to AC current like would be used in a home, it makes sense to pair solar power with batteries and battery powered devices. One problem with this strategy is that electronics tend to be small, and get smaller with each revision. Not only that, when one thinks of solar cells, they generally think of flat surfaces, of which there are few on electronic devices, or cars for that matter. Fortunately, all of these problems are being worked on, and solutions are being developed.
Take, for instance, this article from Technology Review. This article details what the European Polymer Solar Battery project has come up with: thin, flexible lithium polymer batteries with integrated solar recharging. What is noteworthy about this project is that the batteries must have a charging limiter built in to protect from over-charging the batteries. The batteries being used are the same as the ones used in the iPod nano. What possible problems might this be a solution to? Being a blog on automobiles, I think of the car battery. Removing the large lead-acid battery from under the hood and the associated charging system, i.e., the alternator or generator, belts and pulleys would obviously save gas and cut down on maintenance.
[Source: Technology Review]