Physics loophole would allow us to harness electricity from Earth's magnetic field with potential to scale up

08/04/2016 - 18:13

David Lindley

It might seem that classical electromagnetic theory would hold few surprises, but two researchers argue that one aspect of received wisdom is wrong. They show theoretically that a device, sitting passively on the Earth’s surface, can generate an electric current through its interaction with the Earth’s magnetic field. The power from the proposed device would be measured in nanowatts, but might, in principle, be scaled up.


Ref: Electric Power Generation from Earth’s Rotation through its Own Magnetic Field. Physical Review Applied (29 July 2016) | DOI: 10.1103/PhysRevApplied.6.014017


We examine electric power generation from Earth’s rotation through its own nonrotating magnetic field (that component of the field symmetric about Earth’s rotation axis). There is a simple general proof that this is impossible. However, we identify a loophole in that proof and show that voltage can be continuously generated in a low-magnetic-Reynolds-number conductor rotating with Earth, provided magnetically permeable material is used to ensure curl(v × B0) ≠ 0 within the conductor, where B0 derives from the axially symmetric component of Earth’s magnetic flux density, and v is Earth’s rotation velocity at the conductor’s location. We solve the relevant equations for one laboratory realization, and from this solution, we predict the voltage magnitude and sign dependence on system dimensions and orientation relative to Earth’s rotation. The effect, which would be available nearly globally with no intermittency, requires testing and further examination to see if it can be scaled to practical emission-free power generation.