<P> Salinity gradient energy is called pressure - retarded osmosis . In this method, seawater is pumped into a pressure chamber that is at a pressure lower than the difference between the pressures of saline water and fresh water . Freshwater is also pumped into the pressure chamber through a membrane, which increases both the volume and pressure of the chamber . As the pressure differences are compensated, a turbine is spun creating energy . This method is being specifically studied by the Norwegian utility Statkraft, which has calculated that up to 25 TWh / yr would be available from this process in Norway . Statkraft has built the world's first prototype osmotic power plant on the Oslo fiord which was opened on November 24, 2009 . </P> <P> Biomass energy can be produced from combustion of waste green material to heat water into steam and drive a steam turbine . Bioenergy can also be processed through a range of temperatures and pressures in gasification, pyrolysis or torrefaction reactions . Depending on the desired end product, these reactions create more energy - dense products (syngas, wood pellets, biocoal) that can then be fed into an accompanying engine to produce electricity at a much lower emission rate when compared with open burning . </P> <P> It is possible to store energy and produce the electricity at a later time like in Pumped - storage hydroelectricity, Thermal energy storage, Flywheel energy storage, Battery storage power station and so on . </P> <P> The worlds largest form of storage for excess electricity, pumped - storage is a reversible hydroelectric plant . They are a net consumer of energy but provide storage for any source of electricity, effectively smoothing peaks and troughs in electricity supply and demand . Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir to an upper reservoir . Because the pumping takes place "off peak", electricity is less valuable than at peak times . This less valuable "spare" electricity comes from uncontrolled wind power and base load power plants such as coal, nuclear and geothermal, which still produce power at night even though demand is very low . During daytime peak demand, when electricity prices are high, the storage is used for peaking power, where water in the upper reservoir is allowed to flow back to a lower reservoir through a turbine and generator . Unlike coal power stations, which can take more than 12 hours to start up from cold, a hydroelectric generator can be brought into service in a few minutes, ideal to meet a peak load demand . Two substantial pumped storage schemes are in South Africa, Palmiet Pumped Storage Scheme and another in the Drakensberg, Ingula Pumped Storage Scheme . </P>

Who created the worlds first central electric power plant