, but the older systems in windturbines use a quite simple system. You take a small lightsensor that is stationary, place it under a disk, with a slit cut in it, that starts at its widest at 0° and gradually gets smaller untill fully closed when you reach +-360°again. Install another stationery LED oposite to the lightsensor, for the lightbeam. So the lightsensor will measure more light at 0° or a lower voltage(depending on the senor), and the voltage will change as the gap in the disk gets smaller untill no light can pass. Ofcourse you will need to put a closed cylinder around it so no foreign light can hit the sensor. Now just use the voltage difference of the lightsensor and translate in winddirections.