29 The first hydroelectric power station was built in Appleton, Wisconsin, USA, in 1892. Do some research about the location of hydroelectric power plants in Italy. WATER POWER Hydroelectric power is a renewable source of energy that uses the force of water to produce electricity. There are three different methods in which the mechanical energy of water can be exploited to generate electricity: with a dam, or capturing sea waves or sea tides. Hydroelectric plants connected to How much electricity is produced by hydroelectric power plants in Italy? The amount of water stored in reservoirs, and consequently the quantity of electricity that can be produced, is highly dependent on the climate, the season, and the rainfall. a dam A dam is a structure usually located near a river or another water stream in order to block its course. The water diverted from its course is stored in a reservoir, which is a sort of artificial lake. When the dam is opened, water is released through a pipe; the force of the water spins the blades of a turbine which is connected to a generator that produces electricity . The amount of electricity produced depends on the quantity of water flowing in the pipe . Energy production from waves and tides Waves and tides cause water in the oceans to be constantly in motion, and this movement can be used to produce electricity. However, the use of wave or tidal power has been quite limited because there are only a few places in the world that have sufficiently strong waves or large variations in tides to produce enough power. Wave power plants harness the energy from waves on the surface of water, or some metres under the ocean surface; these movements provide periodic flows of water that spin a turbine connected to a generator. Tidal hydroelectric power plants work by forcing ocean water through a turbine. This system depends on regular tidal activity to generate power. The tidal activity is predictable; for this reason, it is possible to know in advance the quantity of energy produced by a tidal plant, while this is not possible for wave plants. Advantages and disadvantages Hydroelectric power has some important advantages: it is clean and produces no emissions of harmful substances in the atmosphere. However, it also has some disadvantages: for example, building a dam is very expensive and requires a suitable location, which is not always available. Moreover, water power depends on climate conditions and it is not available in periods of drought. dam: diga drought: siccit to exploit: sfruttare to harness: imbrigliare 74 ELECTRICITY reservoir: invaso, cisterna stream: corso (d acqua) tide: marea