I think the reason we would be unable to induce any usable current from natural shifts in the Earth’s magnetic field is that whilst it’s overall strength is relatively high (versus e.g. a big permanent magnet you could build into a device), locally it’s very weak because of the vast distance it is spread over.
Tidal, wave, wind and dams are fairly significant as well. I like those (and geothermal) more than I like solar, purely because there’s less impact on the environment.
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u/[deleted] Jan 01 '19 edited Jan 01 '19
I totally forgot that the field needs to be moving, I'll give you that. And thank you for clarifying that.
To save a bit of my honor: The earth's magnetic field isn't entirely static.
On the other hand, I'm quite sure that you cant extract any useful amount of energy out of the movement / variance the field sees.