There are going to be some huge companies thanks to solar. Those companies are also going to have big valuations, at least until the market is much more mature and saturated, but we're decades away from that.

As Ramez said, you don't bet on an "emerging industry", you bet on the winners in that emerging industry, otherwise you may very well lose your money. When new industries are born there are usually hundreds of competitors in the beginning, but eventually only a few big ones remain, and it's usually those that started early and got big early.