Pumped Hydro



Pumped Hydroelectric Energy Storage:



Simple in concept: use excess energy to pump water uphill or back behind a dam

Pump from lower reservoir (natural or artifical) to upper reservoir.

Energy recovery depends on total volume of water and its height above the turbine

  • need at least 30-meters this is a stringent limit on locations
  • artificial lower reserviors can be made via excavation can achieve higher energy density due to large vertical distance (up to 1000 feet!)
  • facility does not impact free flowing stream
  • sediment build-up at dam base is minimized
  • Hydropower is 80% efficient (uphill or downhill). So to pump uphill and the get energy downhill, efficiency is 0.8x0.8 = 64%

Cost Issues:

Suppose a company has a coal fired plant which operates at 36% efficiency and uses excess power to pump water uphill. The overall efficiency of recovering that to deliver to the consumer is 0.36 x 0.64 = 0.23 (23%)

  • So stored energy is more expensive what's the incentive?
  • Need to balance this cost against the costs of building a power planet with capacity to meet some theoretical maximum demand but the rest of the time doesn't operate at this level


Real Life Facility in Michigan

  • Use Lake Michigan as Lower Reservoir

  • Upper reservoir is 75 meters higher

  • Peak capacity is 2000 MW (!)

  • Stored energy is 15 million KWH; 2000 MW drains in 7.5 hours



















China now has the largest engineered facility in Asia:

Specifications:

  • Two storage reservoirs, 1 km apart
  • Elevation is 590m
  • Storage volume is 8 million cubic meters. This equates to 4 GWHs (gigawatt hours)
  • Reservoir drainage: Two 7 meter diameter pipe branches into 3 3.2-m diameter pipes
  • Each 3.2 m diameter pipe is connected to a 306 MW turbine.
  • Total capcity is therefore 1.8 GW meaning the system can drain for about 2.5 hours to get 4 GWHS.
  • Total project cost estimated to be 1.1 billion dollars so that's less than 1.1/1.8 dollars per watt (about 60 cents per watt).

Also the world's first seawater pumped storage facilty recently came on line. Height is 600 m above sea level; total capacity is 600 MW.