Costa Rica powered with 100% renewable energy for 75 straight days {rains and geothermal}

Science alert ^ | 20 MAR 2015 | MYLES GOUGH

[whodathunkit]

They don’t use hydro power, to pump back to the other side of the same dam, to generate power again later. That was the point related to this article.

If a higher reservoir is available it would be used. The pumped storage system can be a closed loop and not located at the generating facility.

You can just close down the valves now and open them back up later. That was the point when pump storage was discussed with hydro power.

Water turbines of that size are designed to operate most efficiently at a certain rpm. They also act like flywheels and resist changes in speed. Good design takes these factors into consideration. There is a similarity to coal fired plants not being able to shut down quickly, there is a time element involved in the output change. Pumped storage increases overall efficiency as well as increasing total output capacity. There is a good example of this design on the Allegheny River in central Pennsylvania (Kinzua Dam) that operates this way. Look on google maps, you can see a round reservoir above and adjacent to the dam on the top of the mountain!

[Lazamataz]

Renewable energy will kill the planet Earth.

[thackney]

If a higher reservoir is available it would be used.

As I said, moved to another location.

Water turbines of that size are designed to operate most efficiently at a certain rpm. They also act like flywheels and resist changes in speed.

Yep, that is part of the reason hydro power dams of any significant size are not built with just one unit. The open and close valves to adjust total flow (water and power generated) while keep each individual unit operating efficiently.

[thackney]

increasing total output capacity

If your pump storage is going through the same hydro plant that generates the power in the first place, there is no increase in capacity.

Pumped storage is not used to increase total capacity. It is used to move power generated at off-peak times to allow more flow at peak times.

[whodathunkit]

I understand what you are saying, However the pumped storage system is a separate loop and normally does not send water back into its own reservoir. (If that were the case, the only gain would be from not having to slow down the turbine thus keeping it running at peak efficiency, probably not worth the extra design costs.)

With that said, most pumped storage systems generate electricity in addition to the main facility during peak load thus temporarily increasing total system output.

[thackney]

However the pumped storage system is a separate loop and normally does not send water back into its own reservoir.

My experience is different. It may not be the most common.

Cheers and thanks for the exchange.

[thackney]

For reference of what I have seen:

http://www.ferc.gov/industries/hydropower/gen-info/licensing/pump-storage.asp

Closed-loop pumped storage as projects that are not continuously connected to a naturally flowing water feature; and

Open-loop pumped storage as projects that are continuously connected to a naturally flowing water feature.