The quality of life today is dependent upon access to a bountiful supply of cheap energy. For a sustainable future, the energy should be derived from non-fossil sources; ideally, it should also be reliable and safe, flexible in use, affordable, and limitless. This paper examines the present global use of energy in its various forms, and considers projections for the year 2020 with particular attention to the harnessing of 'clean' and renewable forms of energy for electricity generation and road transportation. The incorporation of renewables is constrained in many instances by the variable and intermittent nature of their output. This calls for the practical application of energy-storage systems. An evaluation is made of the prospects of the candidate storage technologies - pumped-hydro, flywheels, hydrogen (for use in fuel cells), batteries - for application in centralized and distributed electricity supplies, and in electric and hybrid electric vehicles. The discussion concludes with the developments foreseen over the next 20 years.