37.

kilowatt-hour produced) of thermal electric generating plants improved dramatically, as did the efficiency of transmission of electricity over high-voltage lines.

Increases in technical efficiency are, however, subject to the law of diminishing returns, and the efficiency of energy use in the U.S. appears to be approaching an asymptotic limit at somewhat less than 40 percent. In 1971 the efficiency of the U.S. energy system (Fig. 11) was about 36 percent, and had probably declined a little during the previous two years. The decline came about because of lessened efficiency of energy use in electric-power generation and in automotive transportation. The heat rate in thermal electric power generation has been increasing recently, after about 50 years of almost steady decline, because of environmental requirements and a lower average grade of coal used in more than half of the powerplants. Automotive transport efficiency decreased in part because of new pollution standards, but more because of added weight and power controls. Efficiency of energy-resource use has declined each time electric heating replaced direct space and water heating by a fossil fuel.

Additional increases in efficiency of the energy system will be costly, both in effort (money) and freedom of choice. It is clear that provident technology and restriction of consumer choice must be relied upon in the future if the aggregate efficiency of energy use is to be improved further and if the availability of energy to the U.S. economy is to be maintained at a level consistent with the national welfare. Economic technology is nearing its limit for efficiency improvements.

Until recently, efficiency of energy use was not a matter of public concern in the U.S., because it had been increasing at a rate which allowed

37.

kilowatt-hour produced) of thermal electric generating plants improved dramatically, as did the efficiency of transmission of electricity over high-voltage lines.

Increases in technical efficiency are, however, subject to the law of diminishing returns, and the efficiency of energy use in the U.S. appears to be approaching an asymptotic limit at somewhat less than 40 percent. In 1971 the efficiency of the U.S. energy system (Fig. 11) was about 36 percent, and had probably declined a little during the previous two years. The decline came about because of lessened efficiency of energy use in electric-power generation and in automotive transportation. The heat rate in thermal electric power generation has been increasing recently, after about 50 years of almost steady decline, because of environmental requirements and a lower average grade of coal used in more than half of the powerplants. Automotive transport efficiency decreased in part because of new pollution standards, but more because of added weight and power controls. Efficiency of energy-resource use has declined each time electric heating replaced direct space and water heating by a fossil fuel.

Additional increases in efficiency of the energy system will be costly, both in effort (money) and freedom of choice. It is clear that provident technology and restriction of consumer choice must be relied upon in the future if the aggregate efficiency of energy use is to be improved further and if the availability of energy to the U.S. economy is to be maintained at a level consistent with the national welfare. Economic technology is nearing its limit for efficiency improvements.

Until recently, efficiency of energy use was not a matter of public concern in the U.S., because it had been increasing at a rate which allowed

FIGURE

10'5 Bitw)

7.7

EXPORTS 1.6

17.3

39.

energy costs to decrease. Now efficiency is a matter of concern (1) because it is one of the factors in the rising cost of energy, (2) because lower efficiency depletes the finite stock of fossil and nuclear fuels faster, and (3) because lower efficiency increases adverse environmental impacts of thermal and other effluents of the energy system. Unless we put our faith in provident technology again and again to provide new stocks of energy materials faster than we can use them up, and to provide economic solutions for related environmental problems, we shall need to pay attention to the efficiency of use of energy and other resources.

The cost of energy affects the cost of other resources, especially those that require a lot of energy to extract from the ground, to process, and to transport. Mining and the metallurgical industry are significant users of energy. Rising energy costs can decrease ore reserves, by making it too costly to mine and process material classified as ore under cheaper energy conditions.

The impact of environmental controls on the availability of nonrenewable resources is a pervasive one. We decrease potential reserves by barring mining in areas regarded as scenic, historic, or environmentally fragile; by banning the use in powerplants of fuels containing impurities which will produce undesirable effluents; and by insisting on complete environmental restoration after mining.

Depletion of known reserves may be increased by application of environmental standards. When meeting environmental standards requires additional metallic equipment, lowered operating efficiencies, and more ton-miles of materials transport, depletion is increased beyond what it would be with lower standards.

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