Page 594 - Environment: The Science Behind the Stories

(a) Ice Harbor Dam, Snake River, Washington (b) Turbine generator inside McNary Dam, Columbia River

Reservoir
1 Water flows from
the reservoir through
the dam. Powerlines
Dam

2 The flowing water Intake Powerhouse
turns the turbine.

3 The turbine turns
the rotor, which
consists of a series
of magnets.
Stator
Generator
4 Electricity is produced as the rotor spins past Rotor
the stator, which is the stationary part of the
generator made of coils of copper wire. Outflow Turbine
(c) Hydroelectric power

FIGURE 20.24 Large dams generate substantial amounts of hydroelectric power. Inside these dams
(a), flowing water is used to turn turbines (b) and generate electricity. Water is funneled from the reservoir
through a portion of the dam (c) to rotate turbines, which turn rotors containing magnets. The spinning rotors
generate electricity as their magnets pass coils of copper wire. Electrical current is transmitted through power
lines, and the river’s water flows out through the base of the dam. CHAPTER 20 • CONVENTI ON AL ENERGY ALTERN ATIVES

All these ecological impacts generally translate into neg- and wealth. Canada, Brazil, Norway, Austria, Switzerland,
ative social and economic impacts on local communities. We Venezuela, and many other nations today obtain large amounts
discussed the benefits, drawbacks, and impacts of dams more of their energy from hydropower (TABLE 20.4).
fully in Chapter 15 (pp. 421–422). Sweden receives 11% of its total energy and nearly half
its electricity from hydropower. In the wake of the nation’s
1980 referendum to phase out nuclear power, many people had
Hydropower is widely used hoped hydropower could play a still larger role and compensate
for the electrical capacity that would be lost. However, Sweden
Hydropower accounts for 16% of the world’s electricity pro- has already dammed so many of its rivers that it cannot gain
duction (see Figure 20.1b). For nations with large amounts much additional hydropower by erecting more dams. Moreo-
of river water and the economic resources to build dams, ver, Swedish citizens have made it clear that they want some
hydroelectric power has been a keystone of their development rivers to remain undammed, preserved in their natural state. 593

M20_WITH7428_05_SE_C20.indd 593 13/12/14 1:56 PM