Unregulated distributed energy sources such as solar roofs and windmills and electric vehicle requirements for intermittent battery charging are variable sources either of electricity generation or demand. These sources impose additional intermittent load on conventional electric power systems. As a result thermal power plants whose generation is absolutely essential for any power system are increasingly being used for cycling operations thus increasing greenhouse gas emissions and electricity cost. The use of secondary energy storage might be a solution. Various technologies for storing electric energy are available; besides electrochemical ones such as batteries, there are mechanical, chemical and thermal means, all with their own advantages and disadvantages regarding scale, efficiency, cost, and other parameters.

The supply of energy from primary sources is not constant and rarely matches the pattern of demand from consumers. Electricity is also difficult to store in significant quantities. Therefore, secondary storage of energy is essential to increase generation capacity efficiency and to allow more substantial use of renewable energy sources that only provide energy intermittently. Lack of effective storage has often been cited as a major hurdle to substantial introduction of renewable energy sources into the electricity supply network. The author presents here a comprehensive guide to the different types of storage available. He not only shows how the use of the various types of storage can benefit the management of a power supply system, but also considers more substantial possibilities that arise from integrating a combination of different storage devices into a system. This book will be important to those seeking to develop environmentally sound energy resources.

Energy flow from many primary sources is not constant but depends on the season, time of day and weather conditions. Energy demand also varies with the same circumstances, but generally in reverse. Obviously there needs to be some way for energy suppliers to separate the processes of energy generation and consumption, by storing energy until it is needed.