1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

FIGURE 2-3. Energy overview of United States. (From EIA, Annual Energy Review 2001, U.S. Department of Energy, Energy Information Administration, Washington, D.C., November 2002.)

record level of 11 million barrels per day in 2000. This finding is disturbing, especially when compared to the U.S. petroleum imports in 1973, which totaled 6.3 million barrels per day. In October 1973, the Arab members of the Organization of Petroleum Exporting Countries (OPEC) embargoed the sale of oil to the United States, causing prices to rise sharply and sending the country into a recession. Although petroleum imports declined for two years, they increased again until prices rose dramatically from about 1979 through 1981, which suppressed imports. The increasing import trend resumed in 1986 and, except for some slight dips, has continued ever since. This dependency on foreign energy affects the security of the United States and must be addressed by its political leaders.

Energy is crucial in the operation of the industrialized U.S. economy, and energy spending is high. In recent years, American consumers have spent over a trillion dollars a year on energy [11]. Energy is consumed in four major sectors: residential, commercial, industrial, and transportation. Industry is historically the largest user of energy and the most vulnerable to fluctuating prices and consequently shows the greatest volatility, as shown in Figure 2-5. In particular, steep drops occurred in 1975, from 1980 to 1983, and again in 2001 (not shown) in response to high oil prices. Transportation was the next largest energy-consuming sector, followed by residential and commercial use.

Energy sources have changed over time for the various sectors. In the residential and commercial sectors, coal was the leading source as late as 1951 but then decreased, as illustrated in Figure 2-6. Coal was replaced by other forms of energy. Meanwhile electricity's use and related losses during generation, transmission, and distribution increased dramatically.

FIGURE 2-4. Energy flow of United States in 2001 (quadrillion Btu). (From EIA, Annual Energy Review 2001, U.S. Department of e Energy, Energy Information Administration, Washington, D.C., November 2002.) 0
FIGURE 2-5. Energy consumption by sector in the United States. (From EIA, Annual Energy Review 2001, U.S. Department of Energy, Energy Information Administration, Washington, D.C., November 2002.)
FIGURE 2-6. Residential and commercial energy consumption in the United States. (From EIA, Annual Energy Review 2001, U.S. Department of Energy, Energy Information Administration, Washington, D.C., November 2002.)

The expansion of electricity reflects the increased electrification of American households, which typically rely on a wide range of electrical appliances and systems. Home heating in the United States also underwent a significant change. Over a third of all housing units were heated by coal in 1950 but only 0.2% were coal heated in 1999. Similarly, distillate fuel oil lost a significant share of the home heating market, dropping from 22 to 10% over the same period. Home heating by natural gas and electricity, on the other hand, rose from 25 to more than 50% and from 0.6 to 30%, respectively [11].

In the industrial sector, the use of coal, once the leading energy source, decreased as the consumption of both natural gas and petroleum rose (see

FIGURE 2-7. Industrial energy consumption in the United States. (From EIA, Annual Energy Review 2001, U.S. Department of Energy, Energy Information Administration, Washington, D.C., November 2002.)

Figure 2-7). Electricity and its associated losses also grew steadily in this sector. Approximately 60% of the energy consumed in the industrial sector is used for manufacturing. The remainder goes to mining, construction, agriculture, fisheries, and forestry [11]. The large consumers of energy in the manufacturing industries, for which the fuel of choice is primarily natural gas, include petroleum and coal products, chemicals and associated products, paper and associated products, and metal industries. Nearly 7% of all energy consumed in the United States is used for nonfuel purposes such as asphalt and road oil for road construction and road conditioning; roofing products; liquefied petroleum gases for feedstocks at petrochemical plants; waxes for packaging, cosmetics, pharmaceuticals, inks, and adhesives; and gases for chemical and rubber manufacture [11].

The transportation sector's use of energy, which is mainly petroleum, has more than tripled over the last 50 years, as shown in Figure 2-8. Gasoline accounts for about two-thirds of the petroleum consumed in this sector, with distillate fuel oil and jet fuel being the other main petroleum products used in this sector.

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