As the penetration of variable renewable energy (VRE) such as solar and wind power increases, energy storage is needed for the successful development of a resilient and flexible electricity network. Energy storage systems can provide a host of services to support the grid and address some of the new challenges that high penetration of VRE introduces into the power systems. Energy storage can operate as a standalone system or be co-located with power generation facilities. For owners of coal power plants, there is an alternative to integrate a storage system with generating units to obtain some operational advantages such as improved flexibility, and other benefits. In recent years, there has been a significant increase in the application of utility-scale energy storage systems, and the growth rate is set to continue or even accelerate in the coming years.
Various energy storage systems are commercially available and in operation around the world. Many more storage technologies are emerging into the market or are under development. According to the form in which energy is stored, energy storage technologies can be broadly divided into five categories: mechanical, electrochemical, chemical, electrical and thermal storage. Each system has different capabilities and parameters that make it suitable for particular applications to support the grid. This study reviews the available and emerging utility-scale energy storage technologies and their deployment. The need and opportunities for fossil fuel-based energy storage systems are investigated. Thermal energy storage, batteries and chemical energy storage using water electrolysis for hydrogen production are identified as suitable storage technologies for integration with coal power plants. The possibility of pairing these storage systems with coal plants for enhanced performance and flexibility is explored. The costs, advantages and shortcomings of different integration solutions are analysed and compared, and future research and development (R&D) needs are discussed.