Energy Storage – A global overview and technological comparison

Abstract: Energy storage systems are currently expanding worldwide. This is seen as a result of an increased amount of renewable intermittent energy in the electrical grid. Energy storage is mainly used to balance the supply and demand and increase the reliability of the grid. Energy storage is also used for applications such as heating and cooling of buildings, in electric vehicles and in portable electronic devices.   This project aims to give an introduction and a general overview to most of the current energy storage technologies used globally. This has been done by providing concise descriptions of the chosen technologies, complemented with an overall comparison matrix showing data for these technologies, and finally with a technical and sustainability discussion. The technologies are segmented under four main categories: mechanical energy storage, electrochemical energy storage, thermal energy storage and chemical energy storage.   The study has shown that Pumped Hydroelectric Energy Storage (PHES) is and will still be the main energy storage technology for years to come. Other technologies such as sensible heat storage and Lithium-Ion batteries have undergone significant developments in the recent years, and might become viable options in place of PHES in the future. Currently there is no one single optimal energy storage system which is fitting for all applications; therefore, this study was not able to define a single storage technology that can be promoted as the “best”, globally. Instead, a mix of several types of energy storage technologies is the most optimal storage solution.