We all do know that crystals have the ability to amplify or capture energy, but what about finding a way to use light in the most simpliest way. I was shown something in class a when I was in fifth grade, that dealt with the way light can push a object that is either black or white. I might not be a genious, but I got a idea that could use some looking into.
How about using a crystal to concentrate light to a small point on a perpeller that spins just like a Hydro damn does. Creating electricity that would then flow back through and power the light source. This could create a unlimited amount of energy right? Well not for a city or anything, but maybe enough to power a car or vehicle.
To control how much light is being concentrated into the crystal, we could create like a way to either concentrate it into a single beam or widden into a bigger beam if you feel like.
Now take a book out of the Solar Power Cars, how do they use electricity to run their engines without any crude oil?