HARNESSING ENERGY 



167 



in which the water is shot through a nozzle against 

 the under blades of the wheel. In this way the effi- 

 ciency is raised to about 75 per cent. Figure 279 shows 

 the construction of the three types of wheels. 



The development of hydroelectric power in the 

 United States has also brought about the development 

 of a more efficient device for securing the greatest 

 amount of energy possible from the falling water. 

 This device is known as the water turbine. The water 

 is taken from a dam or large waterfall and run through 

 a closed pipe or duct to the turbine wheel and out 

 through a tail race. The turbine wheel is usually set 

 in a vertical position and connected directly to the 

 electrical generator. Such turbines have efficiencies as 

 high as 90 per cent. Figure 280 shows a cross-section 

 diagram through a modern hydroelectric power plant. 

 Great quantities of energy are being wasted yearly in 

 unharnessed water power. The following table shows 

 the estimated available water power of the world and 

 the amount developed. The amounts are expressed in 

 horse power. This is a unit of working rate. When a 

 source of energy is doing work at the rate of 33,OCO 

 foot pounds per minute it is working at the rate of 

 one horse power. 



Each year finds new water power projects in prog- 

 ress, thus lessening the great energy losses. The 

 Hoover Dam project in the United States and the 

 Dnieper River project in Russia are two of the largest 

 ever attempted. Figure 281 shows a picture of a water 

 power project in the Ozark Mountains of Missouri. 

 The Osage River has been held back by a huge dam, 

 creating a lake with an area of 95 square miles and 

 a shore line of 1,300 miles. The water enters the pen- 

 stocks 1 through huge gates which are opened and 

 closed by the cranes traveling along the top of the 

 dam. This project alone, when completed, will harness 

 more than 128,000 horse power of previously wasted 

 energy. 



1 Penstocks, gates or passageways for regulating the flow of 

 water. 



What is the source of the energy about us? It 

 seems strange to think that the light energy from an 

 electric bulb came from the sun, but a little thought 

 will show that this is true. The light energy came 

 from electrical energy which was produced from the 

 mechanical energy of a steam engine, steam turbine, 

 or waterfall. In the steam turbine and engine, heat 

 energy from coal was used to furnish the mechanical 

 energy. Where did the coal get its energy? From the 

 sunshine that fell millions of years ago on great tropi- 



FIG. 280. CROSS SECTION OF A WATER-POWER SYSTEM 



cal forests which were later changed into coal beds. 

 If the electrical energy for the light came from a 

 water power project the sun, of course, furnished the 

 heat to evaporate the water ; the vapor condensed, fell 

 as rain, and finally rushed down the mountain toward 

 the ocean. In this same way nearly all energy can be 

 traced back to the sun as its source. Try to trace to 

 its remotest source the energy you use in walking. 



Courtesy Union Electric Light and Power Co. 



FIG. 281. BAGNELL DAM ON THE OSACE RIVER IN MISSOURI 



