Physical energy storage employed worldwide

The increasing level in renewable energy capacity presents new challenges. In essence, renewables are weather-dependent and inputs such as solar radiation or wind are not constantly available. The integration of energy storage technologies are important to improve the potential for flexible energy demand and ensure that excess renewable energy can be stored for use at a later time. This paper will explore various types of physical energy storage technologies that are currently employed worldwide. Such examples include direct electrical storage in batteries, thermal storages in hot water tanks or building fabrics via electricity conversion as well as compressed air energy storage. Through this study it has been shown that no single storage system can meet all the criteria to become the ideal energy storage system, each system has its own suitable application range. (C) 2015 The Authors. Published by Elsevier Ltd.