Quote:
Originally Posted by Eratosthenes
interesting....the energy required to lift 28 GL of water by 100m elevation is ~ (28,000,000,000 * 9.81 * 100) = 27.468 TJ of energy
How much of this energy is recovered when it is later unleashed and runs through the turbines?
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Wivenhoe Pumped Storage Hydro Power Station is rated at 2 x 250 MW generating units x 10 hours generating time / 14 hours pumping time per 24-hour cycle. The recoverable energy is thus 5 GW.hr or about 18 TJ per 24 hour cycle, but the losses in pumping and pipeline friction etc mean that you need to expend more energy pumping the water uphill than you recover in the generating phase. The usable stored energy is "roughly the same" as the 9 TJ of theoretical fusion energy contained in a single raindrop.
I don't have the exact efficiency number for Wivenhoe, but the 250 MW generator / motor units, and the pump / turbine units, would have very similar electro-mechanical efficiency in both modes of operation; a typical 24-hour cycle is 14 hours of pumping followed by 10 hours of generating, giving an indicative overall "round-trip" efficiency of about 71%. Industry standard figures for large-scale pumped storage of 70% - 80% is typical, so the numbers stack up.
https://en.wikipedia.org/wiki/Pumped...droelectricity
Modern rechargeable battery technologies are more efficient (80% - 90%, say) but we don't have any electro-chemical battery technology that can scale to GW.hr capacity yet.
The point of pumped storage systems is to act as giant batteries, which can store "base load" scale energy whenever and wherever it is generated, and release it when it is needed. Wivenhoe was built to allow Queensland's coal-fired power stations to operate at maximum base load efficiency round-the-clock, "pumping electricity uphill" in the off-peak periods, and releasing it in peak demand periods, but the same concept works with solar and wind power, for example, which by their very nature are not necessarily generated at times of peak demand.