HYDROELECTRICITY in head is created that can be used to drive turbines and generate electricity A large upstream reservoir may balance seasonal water flow rain or melted snow can be stored in the reservoir during the wet season to provide electricity during dry seasons Small run of river reservoirs or ponds are not large enough to provide seasonal balance They can however provide extra power during daily peak hours In most communities electric-power demand varies considerably at different times of the day To even the load on the generators pumped-storage hydroelectric stations are occasionally built During off-peak periods some of the extra power available is supplied to the generator operating as a motor driving the turbine to pump water into an elevated reservoir Then during periods of peak demand the water is allowed to flow down again through the turbine turbine to generate electrical energy Pumped-storage systems are efficient and provide an economical way to meet peak loads Waterpower is distributed unevenly among the continents and nations of the world Europe and North America have developed much of their waterpower waterpower Asia South America and Africa have abundant abundant waterpower potential but while countries such as China and Brazil have become leading hydroelectric 6
INTRODUCTION The Grand Coulee Dam was built between 1933 and 1941 Its water is used to generate electricity at the Grand Coulee Powerplant hydroelectric producers much of the waterpower resources on those continents remains undeveloped The use of hydropower in the United States has been significant since about 1900 The Columbia River drainage area which is the site of the Grand Coulee Bonneville and Hungry Horse dams has both the greatest potential and the greatest developed developed waterpower California ranks second in the nation in potential waterpower while the Ohio River 7
HYDROELECTRICITY basin is second in developed waterpower Significant Significant additional waterpower potential still exists in the Missouri and Ohio River basins and in the North and South Atlantic portions of the United States The largest hydroelectric power plant in the United States is the Grand Coulee which has a capacity of 7,600 megawatts Among water’s virtues as a source of power is the fact that it is renewable meaning that it can be used again after it supplies energy This contrasts with energy sources including fossil fuels such as coal petroleum and natural gas that are destroyed when they are used Hydroelectric installations also supply added benefits to a region For example a dam built to provide a head for water turbines usually creates a reservoir that can supply water for irrigation irrigation and drinking Potential sources of waterpower include the tides waves and currents of the ocean as well as the differences in temperature between the surface and the bottom of the ocean 8
Chapter One TYPES OF WATERPOWER The vast majority of the world’s hydroelectricity hydroelectricity is produced by the power of falling water Hydroelectric power plants are usually located in dams that are built across rivers In a dam water is collected at a higher elevation and is then led downward through large pipes to a lower elevation The falling water causes the water turbines to rotate producing electricity Oceans can also be used to create hydroelectricity hydroelectricity Those waterpower sources are known as tidal power and wave power Tidal power is created during the tide when the water level along the oceanic oceanic coast changes Wave power is harnessed by the up-and-down motion of waves 9
