According to Mark Roemer Oakland, there are several types of energy storage systems that can save energy in various forms (kinetic, chemical, thermal) and convert them back to electricity for later use. High-quality energy storage systems help to improve flexibility in grid operations and are beneficial for providing electricity to homes in rural areas.
Let’s look at some basic details of common energy storage systems:
1. Pumped hydroelectric storage – Pumped hydroelectric storage systems consist of two reservoirs at different elevation levels and are built along the grid’s transmission lines. These turn the kinetic energy of falling water into electricity, store the excess electricity, and can respond within 10 minutes to the rising demand grid’s needs.
When the supply exceeds the demand, the energy is stored by pumping the water into the upper reservoir. The water is released into the lower reservoir when demand exceeds supply by running downhill through turbines to generate electricity.
2. Compressed Air Energy Storage – Only two Compressed Air Energy Storage (CAES) plans exist in the world (Germany and Alabama) presently since they require an underground reservoir.
First, CAES systems compress air using electricity and store it in an underground cavern. Then, the compressed air is released and used to drive the compressor of a gas turbine to generate electricity. CAES systems have high storage capacity, large power rating, and a long lifetime and can cut carbon dioxide emissions by 40 to 60 percent.
3. Batteries – Batteries are versatile energy storage options since these can be sited along transmission lines, at the generator, and in the distribution system. Plus, they can be used for electric vehicles, residences, commercial buildings, and more.
Batteries convert electricity into chemical energy and back to electricity when required. Thus, these work through an electrochemical process. Common battery types include lithium ion, sodium sulfur, lead acid, and metal air. Currently, lithium ion remains the popular option due to its high power, high-energy density, and high efficiency.
4. Thermal storage – Thermal storage systems utilize mirrors and lenses to collect solar energy in the form of concentrated solar power (CSP) which is used to heat a fluid to run a turbine and generate electricity. The fluid can be molten salts, water, and other molten material and is stored in large tanks until needed.
5. Flywheels – Flywheels energy storage systems utilize flywheels enclosed in a cylinder that contains a large motor inside a vacuum to convert electricity into rotational kinetic energy. These require little maintenance and have long lifetimes.
Flywheel rotors can reach very high speeds since the motors are driven by electricity. The motor converts the stored kinetic energy back into electricity when the stored energy needs to be discharged.
Mark Roemer Oakland suggests you research more about the future of energy storage systems that involve the development of cutting-edge technology and alternatives to current energy storage systems. Battery storage costs are declining rapidly which is generating new possibilities for energy storage and the future of energy storage systems certainly looks promising due to the emergence of new technology.