It was posted on The Climate Thread, Technology Thread and the Energy thread.
Sorry I did not know that posting it so that it reached all target audiences was a problem.
I will not do so in future.
No need for the denigration but the post you were replying to clearly stated
The first use of pumped storage was in the 1890s in Italy and Switzerland. In the 1930s reversible hydroelectric turbines became available. These turbines could operate as both turbine-generators and in reverse as electric motor driven pumps. The latest in large-scale engineering technology are variable speed machines for greater efficiency. These machines generate in synchronization with the network frequency, but operate asynchronously(independent of the network frequency) as motor-pumps.
