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At the Hawaiian Electric Companies, more than 17 energy storage projects are underway or planned to provide grid service or explore and pursue this technology to support the use of more renewable energy and maintain reliable service for customers.
Across all islands we serve, we are implementing storage solutions to help us transform our electrical system. These projects are either owned/operated by the Hawaiian Electric Companies or third parties.
Different Types of Energy Storage can be used to meet many different needs.
The type of energy storage technology selected will depend on the grid application or service provided to meet a particular need. There are various grid services needed to support reliable grid operations. These range from the sub-cycle/seconds timeframe to maintain system frequency (balancing generation and load) and voltage to the hours timeframe of shifting energy from one period to another. The type of grid service will determine the duty cycle and performance requirements of the energy storage system. It is important that the correct technology be selected for the application in order to ensure performance, cost, and life expectancy requirements.
Energy storage falls into four main categories:
- Mechanical: pumped storage hydroelectric, compressed air energy storage, flywheels
- Electrochemical: batteries, capacitors
- Thermal: solar thermal, ice storage, grid interactive water heating
- Chemical: hydrogen storage
Excess energy is typically available during the late night and early morning hours, though solar energy may be in excess during the middle of the day during certain load and weather conditions. Stored energy can be used in three ways. One is load leveling (energy shifting), holding energy produced when demand is low and using it when demand is high. Long-duration energy storage technologies such as compressed air energy storage (CAES), pumped storage hydroelectric, and long-duration batteries work well for this. Another is ramping. Energy from renewable sources like wind and solar typically rises and drops off faster than typical firm-energy generators can ramp down or up to meet the change. Stored electricity can be used to fill in the difference. Shorter duration, fast response storage technologies such as batteries and flywheels work well for ramping. Renewable electricity output can fluctuate second-to-second and minute- to- minute causing problems in voltage regulation. Batteries, flywheels and capacitors can help address these issues.
Details on the various energy storage technologies can be found at the U.S. Department of Energy’s energy storage website. Learn more >