Wind and solar generators both produce DC current, so in that area you are fine. The key thing would be to make sure you have the correct voltage. This can be done by using the proper resistance, or a voltage regulator such as a 7805 which puts out 5 volts. A 7815 puts out 15, etc. The easiest way to stop the flickering would be to use a battery, but the other alternative would be to hook up a capacitor which would do just as much for the random flickering, but it won't work when the sun disappears. My suggestion would be a 4700 micro farad capacitor. That is the basic idea of how to hook something up to a power source that is not completely constant.