ABSTRACT
Hydropower can usefully generate energy over a vast range of scales, ranging from the largest power plants of any type in the world-the Three Gorges Dam and 22,500 MW power station in China down (Figure 8.1) to the “nano” scale hydropower plant of a mere 100 W-a factor of 20 million times smaller. Hydro is also an extremely versatile renewable energy source in terms of its wide variety of forms. The most important usage of hydro is the “conventional” or impoundment power plant hydro, where a dam is constructed to create a reservoir. When the water it contains is allowed to flow out in a controlled manner it can be harnessed to create electricity. The basic components of a conventional hydroelectric power station are illustrated in Figure 8.2. Power is generated as long as the gate in front of the penstock (the sloped channel running down to the turbine) is opened so that the downhill flow of water drives the turbine and the electric generator connected to it.
