This is actually really interesting!
Think about it. We've been limited to solar cells for a long time for producing electricity, and those have limitations we are constantly struggling against. But... Now, you can make a simple isolated enviroment consisting of water and salt. Design it such that fresh water runs down from a resivoir into a lower resivoir with salt. Expose the lower resivoir to sunlight, and use the greenhouse effect to speed up the evaporation of the water. Direct the vapors up to the upper reservoir, where they precipitate out, and flow back down! Thus, we generate electricity and use the sun to separate the two components to repeat the cycle.
(plus if you want, you can capture the heat from the condenser, for even more energy)
Not something you could put in your car, but on a large scale I bet this could work. Similar to large steam powered plants.