Energy storage

Due to concerns regarding climate change and greenhouse gas emissions as well as depletion of fossil fuels, renewable energy sources have great potential as alternative energy sources in energy systems. Renewable energy sources such as solar and wind are intermittent and fluctuating. Hence, energy storage systems are important parts of the renewable energy sector. Energy storage is particularly significant for electricity generation from solar, wind, tidal, and ocean thermal energy conversion technology, in order to ensure availability of electricity at all times. The use of electricity storage is warranted by capacity restrictions of grids. To exploit wind energy, wind turbines are installed in large numbers in regions where the wind potential is high. When the wind turbines work simultaneously, the grid may not be able to transmit the produced electricity and the wind turbines may be forced to shut down. For heating applications such as district heating, thermal energy storage can play an important role for peak shaving and storing thermal energy when the production is higher than the demand. Thermal energy storage can be achieved with a wide variety of technologies. Depending on the specific technology, thermal energy storage allows excess thermal energy to be stored and used hours or days or months later, at scales ranging from individual processes, buildings, and multiuser buildings to districts, cities, and regions. In this chapter, energy storage technologies are described and assessed, focusing on electrical and thermal storage.