Energy Storage Part 1: Types of Storage Systems

Why do we need energy storage?

Our electrical energy used in our homes, businesses and factories is generated as we need it. If demand goes up Electrical Plants generate more electricity. But if the demand goes higher than currently available from local power plants electrical energy must be brought in via high voltage transmission lines from other generating facilities. This process is expensive and less reliable. Usually this high demand is only necessary for a few hours and then drops to a normal levels again. By storing energy by various means at the local level, it can be ready to augment existing generation during high peak demands.
This process provides a low cost source of electricity and more reliable. In addition it does not require the need to build new power plants which are very expensive and are very difficult to get approved through regulatory red tape. Another increasingly important reason for energy storage is that much of our power is from renewable resources such as solar, which do not produce a consistent amount of energy throughout the day. For example solar is only good during daylight hours and only produces at maximum efficiency on clear days. Similarly, wind power only produces on windy days. If on a hot windy day such as Santa Ana conditions in Southern California not all of the energy produced can be used and goes to waste. However with an energy storage system, excess electricity can be stored during the day and used at night in the absence of sun and wind.

Type of Energy Storage 
Batteries: Although Lead-Acid batteries have been used for years, Lithium-Ion batteries are giving a renewed interest since they last up to ten years, provide large output currents, and quickly recharge.
Hydroelectric: This process stores water from rivers behind dams and then controls the output flow to generate reliable electricity. This process has been in use for years and works great in states with significant rain fall and mountainous terrain. More advanced Systems pump water from a lower lake during the night with low cost electricity and then release water from the upper lake during the day to add to the utility.
Thermal: During night time hours when electricity is the cheapest, a refrigerator/freezer is used to create ice. During prime time daylight hours the melting ice is used to air condition buildings without additional building air conditioning and saving electricity.
Compressed Air: Low cost, off hour utility energy is used to compress air in large tanks or underground vaults at high pressure. Then during peak energy requirements the compressed air is used to rotate a generator and provide additional electricity.
Flywheels: Flywheels have been used for backup power for many years. During normal operation electricity is used to turn the flywheel. When power is lost, the flywheel continues to spin for some time generating electricity. This can be used for backup or to provide additional power during high usage times. Their drawback is the limited amount of time that they can run without additional power.
Super Capacitors: These devices can store energy and release as needed. Capacitors have been used for years in electronic equipment to smooth the power to electrical circuits. New technology is allowing them to be used for large scale storage applications.

Part 2 will deal with how energy storage can help provide backup power and reduce electrical costs in business and residential applications.