Pumped-Hydro Storage Efficiency

Have just been looking at a news article, claiming that making your home independent from the electric grid, may not be the best option. Rather than storing your energy at home, it is suggested that feeding it back into the grid may be a better option. It was suggested that the efficiency of pumped-hydro storage is more efficient than batteries. I was skeptical and research into the subject made me more so.

I found articles suggesting overall efficiencies that could be as high as 90%!

Now lets have a look at this:

1. We have an electric motor driving a pump pushing water up to an elevated reservoir. Losses are:

- Electric motor inefficiency.
- Water pump inefficiency.
- Transfer thru pipes inefficiency.

2. We have a water turbine driving an alternator. Losses are:

- Turbine inefficiency.
- Alternator inefficiency.
- Transfer thru pipes inefficiency

Now if we multiply all these inefficiencies together, plus the inefficiency of electric transfer to and from the power station, there is no way an efficiency of 90% can be achieved.

Does anyone out there have some knowledge about this? I would be surprised if an overall efficiency of more than 60% would be possible.

via International Skeptics Forum http://ift.tt/2zQmlti