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Show INTRODUCTION In the United States, the industrial sector accounts for 40% of the nation's total energy consumption (1). Moreover, most major energy studies (2, 3, 4, 5) examining future trends in U.S. energy demand have concluded that if economic growth continues at levels at or near historical levels , the industrial fraction will likely rise to nearly 50% by the year 2000. Thus, energy efficiency improvements in the industrial sector can have a substantial impact on national energy consumption levels. Much of the U.S. industrial base was built in an era of declining energy prices. Approximately 57% of the industrial capacity began operating in 1950 or earlier and 93% of all manufacturing capacity begain operating before 1971 (6). During the period from 1950 to 1970, the aggregate energy cost (weighted fuel cost average) in the industrial sector, discounted for inflation, declined by almost 30% (7). Because of these declining real prices, energy costs were a small fraction (on the order of 3% or less for many industries) of the total production cost and energy utilization was not a prime design factor. The rapid price escalation of oil and gas, which account for about 75% of industrial purchased fuels (1), has led to a greater awareness of energy utilization and spurred greater conservation efforts.' It is interesting to note that even though real fuel prices declined between 1950 and 1970, U.S. industrial energy use per unit of output (as measured by the Board of Governors of the Federal Reserve Systems industrial index of production) declined by about 1.7% per year (2). In response to the rapid fuel price escalation since 1973 industrial energy consumption per unit of output has declined at an annual rate of 5.5% (2). Much of this decline has been achieved with relatively low cost, low risk actions such as insulating pipes, packing valves, turning off unnecessary lights, better regulation of heating and cooling temperatures, etc. Many of these options have, however, been exhausted and future reductions in energy intensity will require capital expenditures to replace or modify existing processes. Thermal energy storage (TES) is one option available to industry to further improve the energy efficiency of existing processes. By storing and reusing energy that would otherwise be discharged to the environment energy 8-3 |