Plug in Hybrids as Grid Energy Storage
Other Grid Energy Storage Options
Grid energy storage involves using excess electricity to charge, or fill a system, such as PHEV batteries, which is capable of providing electricity back to the grid when demand is higher. In addition to the previously discussed Vehicle-to-grid scenario, the following are potential options for storing surplus energy (possibly from solar or wind) for future use
- Pumped water
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Hydroelectric power converts the potential energy of water at a high elevation into electricity as it flows through a turbine to a lower elevation (Ref. 1). If surplus electricity is used to pump water up into a reservoir, the water can later be used to produce hydroelectric power.
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In the UK the Dinorwig power station has 6 reversible pump/turbines which move water back and forth between two reservoirs. (Ref 7)
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Batteries
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Fairbanks Alaska has a large battery bank which helps to balance the demand on the grid and stabilize the quality of the power. Batteries are expensive, require regular maintenance and have a n estimated lifespan of only a few decades, with diminished capacity over time
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Thermal
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Thermal energy can be stored in insulated reservoirs. Molten salt can be used as the working fluid in a solar power plant. The salt is heated to over 1000 degrees by concentrated solar energy and stored in insulated tanks where it can remain hot for up to a week. When the sun isn't shining the heat is still available to run a steam turbine and generate electricity (ref 8).
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Flywheel
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Excess electricity can be used to accelerate a heavy rotating disc. When power is needed, the inertia of the rotating mass is converted back into electricity and the motor, acting a s a generator, reduces its speed.