Why is Energy Storage Important:?
Energy storage must consider both the amount of energy that can be stored (energy density of the material) and the efficiency at which it can be recovered. Some materials have high energy storage capacity but low rate of recovery.
Energy Density of Some Materials (KHW/kg)
Energy density storage drives the choices that can be made:
At the turn of the century electric vehicles were common place (using basically lead-acid batteries). Since gasoline has much higher energy density it quickly dominated the way vehicles were propelled.
In fact, gasoline has one of the highest energy density storage capacities known. This makes it very difficult to duplicate the convenience that gasoline has traditionally provided (e.g. 350 kg of batteries is equivalent to 1 kg of gasoline !).
Pumped Hydroelectric Energy Storage:
Simple in Concept --> use excess energy to pump water uphill --> pump from lower reservoir (natural or artifical) to upper reservoir
Energy recovery depends on total volume of water and its height above the turbine
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%)
Real Life Facility in Michigan
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