Energy storage spans a wide array of devices and mechanisms that can be deployed to manage power supply, to create a more resilient T&D network and bring cost savings to utilities and consumers.
Batteries, which represent just one classification of energy storage technology, have the potential to address various energy- and power-intensive applications. However, the gamut of energy storage devices – including mechanical, electrical and electrochemical – all have a part to play if grids are to properly exploit the technology.
Despite the growing interest in battery-based storage systems, global energy storage capacity is dominated by pumped hydropower, which accounts for over 85% of all stationary energy storage capacity.
Intelligent energy storage systems that are being commercialised are using the following storage devices or technologies:
Electrochemical forms of energy storage
Electrochemical energy storage encompasses many battery chemistries, but below are some of the most promising for grid-tied and other types of stationary storage applications.
Commercialised in consumer electronics and electric vehicles, lithium ion batteries are also a favoured choice for energy storage systems developed for behind-the-meter as well as grid-scale applications. The technology is best suited for storing energy in the range of a minutes to a few hours.
Sodium suphur (NaS)
NaS batteries have been used for large-scale energy storage for over the past 15 years. The technology is suitable for applications where energy has to be stored for several hours, up to a day.
Redox flow batteries
Vanadium redox flow batteries and variants of this type of chemistry are being commercialised in energy storage systems where operators are looking for a reliable and rugged technology, which can be left in the field and requires little maintenance. Remote grids in hot climates are ideal for flow battery storage systems.
Lead acid batteries
The technology is one of the most widely deployed battery technologies in the world, both in motive and stationary applications. However, in order to build lead acid batteries that can operate with longer lifetimes in grid-tied storage applications, the industry has developed lead carbon versions to endow lead acid batteries with more power and performance.
Several companies that build turnkey intelligent energy storage systems are using batteries based on Aqueous Hybrid Ion (AHI) chemistry, developed by Aquion Energy, which uses a saltwater electrolyte and other abundant materials to deliver a sustainable battery that has the potential to be very low cost when mass produced, which is also non-toxic.
Electrical forms of energy storage
Ultra-, or supercapacitors use a double layer capacitor design. They combine benefits of capacitors and secondary batteries. They are being used more in stationary storage applications where high amounts of power need to be released rapidly.
Mechanical forms of energy storage
Flywheels harness kinetic energy in the form of rotating mass to deliver instantaneous electricity. Flywheels capable of storing more energy with extended times for discharging energy are being deployed for grid-tied storage applications, for grid services.
Compressed air energy storage (CAES)
Along with pumped hydro, compressed air energy storage is one of the most mature energy storage technologies in deployment. Liquid air energy storage (LAES, which uses liquid, as opposed to compressed, air as the storage medium is highly scalable with the potential to deliver capacity in the GWh range.