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Storing Energy

The major drawback to solar and wind energy is its unpredictable nature.

Sunlight reaching the Earth’s surface is attenuated by clouds and wind is always variable.  In order to circumvent the variable nature of these energy sources and provide a more steady generation of electrical energy, solar and wind collection is often interfaced with energy storage devices, such as batteries, that store excess collected energy for use at a later time.





Although a rechargable battery is a common form of energy storage in which electricity is converted into chemical energy, other storage strategies are currently being used...



Pumped Hydro

Water located at a higher elevation contains potential energy that can be recaptured when it flows downhill through a waterwheel connected to a generator.

In reverse, electricity sent through the generator can turn the waterwheel to pump the water back uphill.  In this way, excess solar and wind energy can be stored as potential energy to be used when needed.



Compressed Air

A similar way to store excess energy is by using it to compress air into an airtight vessel, like a cavern underground.

Excess energy is used to drive a compressor that squeezes the gas and increases its pressure relative to the pressure outside.  This pressure difference is analogous to the differing height of water in the pumped hydro storage scheme and represents a source of potential energy that can be reclaimed when the gas expands.



Hydrogen Fuel Cells

Excess electricity can be used to separate water (H20) into two gases, hydrogen and oxygen, through a process known as electrolysis.  The electric energy is now converted into chemical potential energy.








The stored energy can be retrieved when hydrogen and oxygen are recombined to form electricity in a hydrogen fuel cell with a byproduct of water.









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