Can Earth’s rotation generate power? Physicists divided over controversial claim (archive)

As Earth rotates and part of its magnetic field remains static (at least according to a 1912 proof), a conductor on its surface would move through some components of the field. Experiments suggest that an unusual magnetic material can help harness energy from the planet’s rotation. But not everyone is convinced.

The rotational kinetic energy of our planet is 1/5 M * R² * w² with (approximately) M = 6e34 kg, R = 6.3e6m, w = 7.4e-5 rad/s, which gives approximately 5e36 joules. Yearly we need roughly 3¹⁶ Wh. If the technique provided all of Earth’s electricity needs, which was around 11 trillion watts in 2022, this would slow the planet’s spin by 7 milliseconds over the next century, the authors calculate. This is similar to the change in speed caused by natural phenomena such as the Moon’s pull and changing dynamics inside the planet’s core.

For instance Jeener claims to prove that no such effect is possible. But this conclusion results from a failure to recognize a distinction between the corotation with Earth of the nonaxially symmetric components of Earth’s magnetic field and the nonrotation with Earth of the axially symmetric components. Because the distinction has considerable empirical support, Jeener’s argument is likely incorrect.

Carlo Rovelli, a theoretical physicist from Aix-Marseille University in France, is more open to the idea. He notes that energy is conserved for an electric charge moving in a uniform magnetic field, which seems to rule out the effect. But since the charges in the experiments are moving in a solid material, Rovelli says, this argument is not relevant.

Meanwhile, authors have found in the laboratory that Mn-Zn ferrites material—appear to be photoactive, so that experiments must be protected from light. Worse, Mn-Zn ferrites have very high Seebeck coefficients, and laboratory temperature gradients easily overwhelm or cancel (depending on orientation) the sought-after effect. Reliable results therefore require either isothermal conditions or that temperatures at both ends of the Mn-Zn cylindrical shell be measured simultaneously with the emf, in order to control for the Seebeck voltage.

The researchers replicated these effects in a different setting with a largely unregulated environment, a residential building 5.5 kilometers east of their primary lab. They also found that a solid bar of manganese-zinc ferrite did not display these effects, nor did a metal tube with different magnetic and electrical properties display these findings.

Notably, the team says the device stopped generating power when its orientation was changed in relation to the Earth’s magnetic field. “The voltage is 0 when the device is oriented with its long axis in the E-W direction and -18 microvolts when the device is oriented with the “red” end toward the north (we call this the 0 degree orientation),” Chyba explained, “but +18 microvolts when the “red” end is oriented toward the south (the 180 degree orientation).”

The largest initial expense was for the three battery-operated data-logging digital multimeters, which the professor said cost about $1,500 each in 2016. The battery-operated meters would log data for five to ten hours per experimental run, with the experimenter typically returning around eight hours afterward to turn the lights on and log the data. “I think the total expense to reproduce (or rebut) this experiment today would be under $10,000,” Chyba estimated. See also:

Attempting to Extract Power from Earth’s Rotation: A Failed Experimental Test. Rinke Wijngaarden, a retired physicist, failed to find the same effect during his own 2018 experiments. In a story about the team’s latest findings, Wijngaarden told Nature that he has followed the research since 2016, and although he thinks their new device is interesting, he is “still convinced that the theory…cannot be correct.”