Spanish island to be fully powered by wind, water

Originally posted by FabianFnas
A question about storing energy in a dam of water in a higher level:

You need energy when you pump up the water. How many percent of that energy do you get back when you let it down again in a hydro power plant?

I would think it is quite ineffective process...

arr it just so happens I have done some internet research on this very subject:

http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

"... energy efficiency varies in practice between 70% and 80%,[1][2][3][4] with some claiming up to 87%.[5] ..."

-Not too bad I suppose -but I think it surely can be made to be much more efficient! This is because the most energy efficient electric motors are about 98% energy efficient and I see no significant reason why they couldn't be designed to power ultra-low friction piston pumps (rather than turbines ) to pump water up into a reservoir with an energy efficiency of perhaps ~96% ?

Originally posted by humy
arr it just so happens I have done some internet research on this very subject:

http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

"... energy efficiency varies in practice between 70% and 80%,[1][2][3][4] with some claiming up to 87%.[5] ..."

-Not too bad I suppose -but I think it surely can be made to be much more efficient! This is because ...[text shortened]... er than turbines ) to pump water up into a reservoir with an energy efficiency of perhaps ~96% ?

My guess is the loss of efficiency is not so much due to electromechanical losses in the motors but a lot of the loss coming from friction of the water flowing down pipes.

I would not be surprised to find work done to lower the friction co-efficient of water flowing in pipes would give them a better shot at 95+%.

For instance, coating the inside of the pipes with teflon for instance or some of these hydrophilic compounds Nissan just developed for car paint.

Originally posted by sonhouse
Originally posted by humy

Wow, I thought it would more like 30% or something...
Okay, now we're talking!