Alternative energy comprises renewable sources of energy (hydro; biomass; wind; geothermal; solar, which includes [concentrating solar power]; and ocean sources, comprising tidal, wave, marine currents, ocean thermal energy and tapping the salt gradient), nuclear power, and waste. The use of renewable sources of energy can be optimised if advanced energy storage systems are developed and employed, so energy storage is another topic covered in this paper. Finally, the use of hydrogen as an energy carrier, while at present an adjunct of fossil fuel-based energy, is seen as being a key facet of a renewable-energy-based system in the very long run. Hence the issues pertaining to the future development of hydrogen in the energy system are discussed in this paper by Ainsley Jolley, Climate Change Working Paper No.7.