A Princeton-led team has built a tabletop device that generates voltage directly from Earth’s rotation through its magnetic field. While the power output is orders of magnitude too small for practical electronics, the breakthrough suggests Earth’s spin could someday provide constant, fuel-free energy if the effect scales up. The team is now calling for independent labs to reproduce the results.
This.
That thing is at best a sensor, certainly not a power generation device.
The antenna in my phone likely “harvests” orders of magnitude more electricity when receiving signal.