> power out isn't "matched or exceeded"
>> The water would then be pumped out. The electricity generated by the water pouring in
>> is matched or exceeded by that needed to pump it out.
> except that it won't supply any energy itself. The island could supply two million Dutch homes
> when fully emptied, yes - but for only about half a day. And no, power out isn't "matched or
> exceeded" by power in, it's definitely exceeded. There are no perpetual motion machines.
To be fair if they can time the pumping in and out with the tide state then filling it up at high tide and emptying it at low tide would give a possibly useful gain. But of course that spectacularly reduces the flexibility that was the point of the exercise ibn the first place...