Increased mechanization has simplified our daily lives significantly, but their high energy consumption nature has also raised concerns about depleting fossil fuels (currently the main source of energy). Research is being carried out worldwide to find alternate sources of energy. Solar and wind energy sound most promising but their intermittent nature is a major drawback. To counter this, significant R&D is being done to devise efficient energy storage devices. This module attempts to give an overview of alternate energy systems and highlight the importance of energy storage devices. Principle of operation, R&D and future trends, merits and limitations of various energy storage systems will be discussed. Pumped storage devices, fuel cells, batteries and their types, super capacitors and hydrogen storage will be focused upon.