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energy storage
The process of storing, or converting energy from one form to another, for later use. Energy storage can improve the efficiency and reliability of the electric utility system by reducing the requirements for spinning reserves to meet peak power demands, making better use of efficient baseload generation, and allowing greater use of intermittent renewable energy technologies. Energy storage technologies include utility battery storage, flywheel storage, superconducting magnetic energy storage, compressed air energy storage, pumped hydropower, and supercapacitors.
Technologies
Utility battery storage (UBS)
UBS systems allow utilities or utility customers to chemically store electrical energy for dispatch at a time when its use is more economical, strategic, or efficient. Existing UBS systems use lead-acid batteries. Compact, low-maintenance valve-regulated lead-acid (VRLA) batteries have been developed for distributed power applications. The suitability of a battery system to utility applications is affected by factors such as its response time, power density (the amount of power available from a battery in relation to its mass or volume), discharge rate, and life cycle costs.
Flywheel storage
In flywheel storage, a flywheel spinning at very high speeds is used to store energy by combining it with a device that operates either as an electric motor that accelerates the flywheel to store energy or as a generator that produces electricity from the energy stored in the flywheel. Modern flywheels use composite rotors made with carbon-fiber materials. The rotors have a very high strength-to-density ratio, and rotate in a vacuum chamber to minimize aerodynamic losses. The use of superconducting electromagnetic bearings can virtually eliminate energy losses through friction.
Superconducting magnetic energy storage (SMES)
SMES systems store energy in a magnetic field created by the flow of direct current in a coil of superconducting material that has been cryogenically cooled.
Compressed air energy storage (CAES)
Compressed-air energy storage is a technology that uses off-peak electricity to compress air and store it in airtight underground caverns. When the air is released from storage, it expands through a combustion turbine to create electricity.
Pumped hydropower
Pumped hydro facilities use off-peak electricity to pump water from a lower reservoir into one at a higher elevation. When the water stored in the upper reservoir is released, it is passed through hydraulic turbines to generate electricity.
Supercapacitors
With characteristics of both batteries and capacitors, supercapacitors (also called electrochemical capacitors or ultracapacitors) could be used by utilities to regulate power quality.
Related category
• ENERGY STORAGE
Source: U.S. Department of Energy, Distributed Energy Program
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