Seite - 119 - in Water, Energy, and Environment - A Primer

8.4 HYDROPOWERANDWINDENERGY Hydropower andwindenergyare closely related in that both are systems that use turbineblades to convert thekinetic energyof a moving fluid into electricity. In the caseof hydropower the fluid is water, in the case of wind energy it is air. In both cases the energy available for conversion is proportional to the third power of v, the fluid speed past the turbine: v2 from the kinetic energy in the flow (½mv2) and v from the rate atwhich fluid is moving through the blades. Thus, if the fluid speed is doubled, the available energy increases by a factor of 23=8. 8.4.1 Hydropower Theuseof fast-movingor fallingwater forhumanpurposeshasa longhistory. Indiautilizedwaterwheelsandwater-poweredmills more thantwothousandyearsago; theRomansusedwaterpower to saw wood and stone, and to produce flour from grain; and watermills have been used for centuries in China. In the late 1800s hydropower became a source for generating electricity, and the first commercial hydroelectric power plant was built at Niagara Falls in the US in 1879. Today the term hydropower is used almost exclusively to refer to the modern development of hydroelectric power, which is seen as an important means for economic development. Resistance to these hydropower schemes can arise from the human displacement sometimes involved and adverse environmental impacts. Deployment of hydropower falls into two categories: traditional hydropower generation (flow-of-river and high-head; see Figure 8.10) and pumped storage, ameans of storing excess electricity. Asof the endof2017,global installed traditional hydropower capacitywas1267GW,while installedpumped storage capacity was 153 GW. It currently is producing 17% of the world’s electricity and is the largest source of renewable electricity in the world (71%). China leads the world in hydroelectric Renewableenergy 119