If you google "crystal radio", you will find that the power used is the radio wave captured by the "long" antenna. My idea goes somewhat along these lines. It is common knowledge that every astrological body produces natural radio waves. If we expand our antenna, by building a 40 foot tall radio tower, and place a coil of wire down the center of the tower. We unground the tower, and connect one wire of the coil to the ground. The other end of the coil should produce wildly fluctuating voltage. We run the output through a series of ceramic rectifiers. After taking readings for a period of time, we take an average and build a voltage regulator, with capacitors to fill in the ocational valleys in the output. We would now have usable DC electrical power.