Wind powered pump-storage plant

Re: Wind powered pump-storage plant

Yes the hydro storage would serve as a kind of "battery" to store excess energy produced by the wind turbines thus mediating the output.

I have to say I don't like the parameters set up for the exercise. The losses are not "negligible" by any means, and to relegate them to the scrap heap is, in my opinion, teaching poor practices.

In practical terms there are at least the following problems to such a design:

1). Site wind. You'd be amazed at the number of wind turbines (especially small scale) that get erected on sites which really don't have enough wind to produce, much less produce surplus. Especially considering the next factor.
2). Elevation for hydro reservoir. Simply filling a tank will have limited power capacity, as the available stored potential kinetic energy will drop off quickly as the tank drains. Pumping the water uphill will give an added advantage. Hydro storage has been discussed on this forum before, and largely deemed impractical on small scale.
3). Energy transfer losses. Far from being negligible, these are significant to the design of a system such as this. Wind turbines aren't very efficient to begin with. Turning that mechanical power into electrical power and then back into mechanical power to pump water will use up much more. The friction losses of the water going through the pipe into the reservoir will not be small either. And then you have to lose more when the stored potential kinetic energy gets converted back in to electricity.
4). Demand variations. Having to "ramp up" power production on demand is a major problem for all utility systems. To be able to quickly turn the stored power back into electricity at a second's notice isn't easy. Chemical batteries can manage this, but are impractical for large-scale storage. In the real world, the system you propose would require multiple turbines and a quite complex computerized monitoring system to anticipate and "spin up" additional turbines as demand increases.

You could perhaps cut out some of the losses by using the turbines to pump directly, continually refilling the reservoir as wind permits, and supplying the electric from turbines kept spinning continuously.

As for the ability of the hydro to produce, it is a function of being able to spin the turbines at the correct speed with enough pressure behind them to overcome the resistance of the (varying) magnetic field interface. In simple terms, you either need a very large volume of water flowing very fast (geared down to provide the necessary torque), or a lesser amount with significant pressure (head) behind it.

The formula supplied by your teacher is, in my opinion, too simplistic to be of any real value. Why not ask him/her if it should apply to the hydro side as well, since this is a totally theoretical exercise?