Pumped Hydro

 

As the solar industry grows it will eventually be necessary to store energy. By far the largest energy storage today is pumped hydro – about three times larger than Australia’s entire electricity capacity.

When electricity is cheap, water can be pumped up a 500 metre high hill, and released when the price rises, through a turbine to generate electricity. Pumped hydro doesn’t need to be located on a river, since the same water goes back and forth.

Since storage is needed only for a day, the water store can be quite small. The area of lake required to provide one day’s storage is 5 m2 at 500 metre high, per person. There are thousands of suitable sites in Australia.

Hydro recovers 70-85% of the energy pumped into storage.

Hydro is good for peaking generation and it only takes 15 seconds to start generating power.

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Pumped hydro in Japan  Source

The Kidston Pumped Storage project

Cenex is planning to turn two disused gold mine pits into a pumped hydro system.

Power will be 330 MW with a capacity of 1,650 MWh per generation cycle. 

During peak power demand periods water will be released from the upper to the lower reservoir, passing through 3 x 110MW reversible pump/generators acting in generation mode. During off peak periods, water will be pumped back from the lower to the upper reservoir with the pump/generators acting in pumping mode. 

Being an old mine, much of the infrastructure is still in place. Roads, powerline connection, buildings, and a water supply dam. Website

 Kidston Gold Mine 270km north west of Townsville.

A change in water level of approximately 8m in the upper reservoir and 44m in the lower reservoir during a full generation cycle, with an average water head of approximately 190m over the course of the cycle.

 

Energy in falling water

1000 kilograms of water (1 cubic meter = 1 tonne) at the top of a 100 meter tower has a potential energy of about 0.272 kW·h (capable of raising the temperature of the same amount of water by only 0.23 Celsius 

Water has to fall 435 M to warm itself 1Co .

To heat it from 0 to 100oC, it needs to fall 41.6 KM! So you need a lot of falling water to heat water.

To boil off the water once it had reached 100oC, the water would need to fall over 2,100 KM. 

Genex Power is currently developing the large scale Kidston Hydro Pumped Storage Project located in Northern Queensland. The Kidston Project involves the installation of a 330MW Pumped Storage Plant at the historical Kidston Gold Mine site. Once completed, the Kidston Project is expected to deliver power into Queensland's electricity network during peak demand periods. The Kidston project has low capital intensity given the unique characteristics of the old mining site including, existing dams, water, pipeline and electricity infrastructure. Following the recent completion of a pre-feasibility study, the project has now transitioned into full feasibility stage. If it goes ahead, it will be the biggest solar plant (although it may face some competition from competing proposals), but certainly the largest combined solar and storage project in the Australia, and a world first on the latter metric.

 

An 11 MW El Hierro pumped hydro facility, partnered with wind, now makes Canary Island 100% renewable

   

A new concept is to use wind turbines or solar power to drive water pumps directly, in effect an 'Energy Storing Wind or Solar Dam'. This could provide a more efficient process and usefully smooth out the variability of energy captured from the wind or sun.[20][21] [22]

One can use pumped sea water to store the energy. The 30 MW Yanbaru project in Okinawa was the first demonstration of seawater pumped storage. A 300 MW seawater-based project has recently been proposed on Lanai, Hawaii, and several seawater-based projects have recently been proposed in Ireland.

 

Tidal pumped hydro

Another potential example of this could be used in a tidal barrage or tidal lagoon. A potential benefit of this arises if seawater is allowed to flow behind the barrage or into the lagoon at high tide when the water level is roughly equal either side of the barrier, when the potential energy difference is close to zero. Then water is released at low tide when a head of water has been built up behind the barrier, when there is a far greater potential energy difference between the two bodies of water. The result being that when the energy used to pump the water is recovered, it will have multiplied to a degree depending on the head of water built up. A further enhancement is to pump more water at high tide further increasing the head with for example intermittent renewables.[23] Two downsides are that the generator must be below sea level, and that marine organisms would tend to grow on the equipment and disrupt operation. This is not a major problem for the EDF La Rance Tidal power station in France.

Instead of pumping water uphill, the pumped storage idea can be inverted, pumping air under water.

Source: Wikipedia