Can tidal power plants have an effect on the Earth's rotation?
I just read an interesting article on the project to build power plants that tap into tidal energy. It's really weird to see that article now because I was discussing that exact subject with Fabien on the Stevens Pass chairs last Saturday.
A couple comments:
- There is a power plant in France that works on this principle. It's been operating since 1966 and it's producing 550 million kWh a year. China operates eight similar plants, and Canada also has one.
- This energy is *NOT* renewable. It's basically gravitational potential energy. Thoses of you familiar with physics know about the principle of action and reaction, which in this case implies that such energy tapping would in return have an impact on the relative motions of the Earth and Moon. Of course this effect is very very small and probably safe to ignore but we do have a precedent: the Moon itself now always shows the same face to us because the dissipation of the tidal energy into deformations of the crust quickly forced it into the minimal energy position which is the one where the tidal bulge on the rock always faces the direction of the tidal force. This is exactly similar: the deformation was tapping from the tidal energy, which slowed down the rotation of the Moon. How long would it take for the Earth? I didn't make any calculations but I'm pretty sure that would be a huge number.