Batteries



Batteries remain one of the most common forms of energy storage. Lithium-ion batteries are widely used in consumer electronics due to their high energy density. Lithium-ion batteries store lithium ions that move from the negative to the positive electrode during discharge and back during charging. Researchers are working to improve lithium-ion battery technology to increase energy capacity and lifetime. New anode and cathode materials with higher energy density are being developed.



Energy Storage System in technology gaining interest is lithium-sulfur batteries. Sulfur has a very high theoretical specific capacity of 1675 mAh/g, over five times greater than traditional graphite anodes. However, lithium-sulfur batteries face challenges from the insulating nature of sulfur and polymer separators that can be dissolved by battery electrolytes. Scientists are working on new composite cathode materials and solid-state electrolytes to help realize the full potential of lithium-sulfur batteries.



Flow batteries offer an alternative battery architecture with independent scaling of power and energy capacity. In flow batteries, the electroactive materials are stored in external tanks connected to the power conversion system where the redox reactions occur. This allows the energy capacity to be increased simply by using larger electrolyte tanks, without affecting the maximum power output which is determined by the size of the power conversion stack. Further cost reductions through materials optimization and manufacturing improvements could help flow batteries compete in large-scale energy storage applications.



 Flywheels



Flywheels store kinetic energy in a spinning rotor or flywheel. In a flywheel energy storage system, excess power from the grid or renewable sources is used to accelerate the spinning rotor. During discharge, the rotational inertia of the flywheel is used to generate electricity via an electro-mechanical generator.



Recent advancements in composite materials and magnetic bearings have significantly improved flywheel performance. Stronger, lighter carbon composite rotors allow higher energy densities to be achieved in a smaller volume. Magnetic bearings eliminate friction and wear Issues of traditional mechanical bearings, reducing losses and improving lifetime. Flywheel systems offer high power output over short durations and can perform thousands of charge/discharge cycles with minimal degradation. This makes them well-suited for applications requiring fast response times like frequency regulation in the power grid.



Advanced flywheel systems are being developed and commercialized at multiple Megawatt-hour scales. However, achieving very high energy densities while maintaining safety continues to be a challenge, limiting their adoption for large-scale longer duration storage. Improvements in rotor design and failure containment systems are active areas of flywheel research and development.



Compressed Air Energy Storage



Compressed air energy storage (CAES) systems store energy in the form of compressed air. During charging, surplus electricity is used to power high-pressure air compressors that inject compressed air into an underground storage facility, usually a depleted gas field or aquifer. Later, when energy is needed, the stored compressed air is released through turbines to generate electricity.



The first generation CAES plants built in the 1970s used natural gas combustion to reheat the expanded air before entering the gas turbine, dramatically improving the roundtrip efficiency. Adiabatic CAES systems aimed to recover some of the heat of compression to preheat air during discharge without using fossil fuels. Recent research focuses on developing Advanced Adiabatic CAES technologies that provide grid-scale energy storage with high efficiencies of over 70% through thermal energy recovery and storage.



Underground geological structures are required for large-scale CAES systems with multi-Gigawatt-hour storage capacities. Developers are exploring alternative above-ground configurations using man-made caverns or tanks to avoid siting challenges of geological formations. Integrated with renewable generation, CAES can provide cost-effective long-duration storage to help decarbonize the electric grid. Continued technology improvements aim to better leverage the inherent benefits of CAES for grid balancing applications.



Pumped Hydroelectric Storage



Pumped hydroelectric energy storage (PHES) is a mature and proven grid-scale storage technology. In a PHES plant, energy is stored by pumping water from a lower elevation reservoir to a higher elevation reservoir, usually using surplus grid electricity during off-peak times. When power is needed, the stored water is released through hydroelectric turbine generators to produce electricity.



Over 95% of global energy storage capacity is provided by PHES facilities with multi-Gigawatt, multi-100-MWh systems. Advantages include virtually unlimited storage capacity scalability based on reservoir sizing, long operational lifetimes exceeding 50 years, and high roundtrip efficiencies of over 75-80%. However, PHES requires specific and suitable topographical conditions making new large-scale plant development challenging.



Recent PHES research focuses on hybridizing with other renewable technologies. For example, solar-pumped hydro involves using solar photovoltaics to directly power water pumps. Developments are also underway to deploy modular pumped hydro units with underground reservoirs with storage capacities in the 10's of MWh range. With advanced control strategies, PHES continues playing a vital peaking power and grid balancing role as variable renewable penetration increases on the electricity grid.

About Author:

Money Singh is a seasoned content writer with over four years of experience in the market research sector. Her expertise spans various industries, including food and beverages, biotechnology, chemical and materials, defense and aerospace, consumer goods, etc. (https://www.linkedin.com/in/money-singh-590844163)