Experiments have been attempted with long wires extended from satellites cutting the Earth's magnetic field but mechanical problems seem to have frustrated the attempts.

i dont support wires from sat but imagine a system of wires at north or south pole or even equator stand alone, the thing is that they move by the movement of earth and there it is.You have energy

Earth's field is too weak to create usable electricity, in a practical package.The "Generator" would have to be large, and would take a lot of energy to move through the field, energy probably best spent on traditional generating means, or end users.