I took my children to the San Diego Natural History Museum today,  and as we were wandering through an exhibit about water,  I came across a display illustrating the sea windmills that are being developed in England.  These underwater windmills were generating power using the tidal current generated twice a day by the moon.

The concept of harnessing the tide to generate energy has never occurred to me,  but it sure sounds like a viable alternative for coastal cities to generate clean, local, renewable energy.  I am not well versed as to the challenges this type of energy produces, but it deserves some research.

A couple of quick sites that I found in my initial internet search:

Wikipedia entry

Sea Windmills

Another interesting exibit explained how in Africa,  A children’s merry-go-round was attached to a water pump,  and as the children played, spinning round-and-round, and powered a pump, bringing water to the surface.