The five most common renewable energy storage solutions each have advantages and drawbacks. Potential adopters and investors need to understand these technologies to make informed decisions. This article highlights the strengths and weaknesses of each energy storage solution in terms of innovation and execution.
Pumped-Storage Hydropower
Pumped-storage hydropower (PSH) uses hydroelectric turbines to convert the potential energy of elevated water into electricity. Power from a renewable source pumps water from a lower reservoir to a higher one. This configuration makes it possible to deploy PSH in some environments where constantly flowing water is challenging to find.
Although 94% of the energy storage in the U.S. is PSH, new facilities are complex, long-term projects taking 3-5 years to build. The timeline often deters investors looking for short-term investments in a quickly changing market. Furthermore, constructing large-scale water reservoirs may damage or disrupt the local environment.
Lithium-Ion Battery
According to the Environmental and Energy Study Institute, lithium-ion batteries control 90% of the global market for grid-scale battery storage. These batteries are efficient, last up to 15 years, and have a very high energy density. As a result, lithium-ion batteries and solar panels have replaced diesel generators in many developing countries, providing reliable access to electricity.
Unfortunately, batteries are not a sustainable energy storage technology. The materials used to make them are highly reactive or toxic, and mining has proven to be damaging to the environment. Finally, most parts of the world do not have a reliable infrastructure to recycle batteries on a large scale.
Thermal Energy
Thermal energy storage technology harnesses the sun’s heat to melt salt or other materials and store them in an insulated holding facility. The stored heat can engage a turbine to produce electricity when needed. The adaptability of thermal energy storage is attractive, but it is dependent on the local climate. Without enough sun, the efficiency can suffer, making it less cost-effective.
Compressed Air
A compressed air energy storage (CAES) system pumps air into a storage facility. As the stored air leaves containment, it passes through an expansion turbine generator to produce electricity. Depending on storage size, CAES can hold a tremendous amount of energy.
The technology of CAES systems has not advanced far enough to make them a viable solution. Artificial containment structures are an expensive alternative in areas with no natural caverns. Moreover, the very low power density and efficiency of existing CAES facilities is not an encouraging sign.
Flywheel Energy Storage Systems
Flywheel energy storage systems use the rotational inertia of a spinning flywheel to produce electricity. New technologies make these kinetic energy storage systems (KESS) reach efficiencies equal to lithium-ion batteries but with no negative environmental impact. Furthermore, flywheels have a high energy density, can operate with little maintenance, and last for many years.The KESS industry leader is Amber Kinetics, a California-based company that has developed the only available long-duration flywheel energy storage system. Since installing its first long-term KESS in Alameda, CA in 2014, Amber Kinetics has deployed many more units worldwide, most notably in the Philippines and Australia with over 578k cumulative hours running and 916MWh discharged.
