Energy efficiency: An overview
The interdependence between energy and industrial growth is crucial in formulating policies for sustainable development. Industry is a major market for energy, and the pricing and availability of energy closely affect industrial growth. Conservation of energy is possible through short-term measures in the industrial sector, but major changes in the structure and mode of transportation also become necessary if significant gains are to be made. But as the economic life of vehicles is relatively short, a transition in the road transport sector can be implemented more easily than in the case of rail transport, where replacement of existing capital stock is slower.
The major technical measures for energy conservation in industry include the recovery of heat from exhaust gases, the introduction of integrated energy systems, the recycling and re-use of materials, and automatic control, as well as the search for more advanced equipment and processes. Energy conservation in industry has led to improvements in overall energy efficiency in many countries over the last 15 years. In the United States, for instance, industrial energy use declined by 17 per cent between 1973 and 1986. This occurred in spite of a 17 per cent increase in industrial production during the same period. Structural changes and the replacement of open-hearth furnaces by more efficient basic oxygen furnaces has cut energy needs by half in the steel industries of most industrialized nations. Co-generation has grown rapidly in the United States and may surpass the share of nuclear energy by the end of the century.
Seen globally, these gains from decreased energy and materials intensity in the industrialized world may well be offset by the growing industrialization in developing countries. It is therefore imperative that the frontiers of technology shift along with the movement of many energy-intensive operations in the developing countries.
The iron and steel industry exemplifies the progress made in energy conservation and at the same time shows the potential for further improvements. With 6 per cent of the world's commercial energy consumption, the steel industry is a highly energy-intensive sector. Table 1 shows, however, that use of energy per ton of steel produced in India and China is more than twice as high as in Italy and Spain. The two latter countries have turned to the electric arc furnace, which uses 100 per cent scrap and as a result requires only two-thirds of the energy needed to convert the ore to the final product. The world recycling rate could easily be doubled or even tripled (Brown et al., 1985) from the present levels. In the United States, investments in energy conservation could cut the energy required per ton of steel by a third by the turn of the century. In China and India, investments to upgrade from the open hearth furnace would save at least 10 per cent of energy use. A World Bank study estimates that such investments could pay for themselves in less than a year (quoted in Brown et al., 1985). Further conservation could be effected in developing countries which plan to expand capacity, such as Brazil.
Table 1 Energy use in steel manufacturing in major producing countries, ranked by efficiency, 1980
Source: Brown et al., 1985.
a. These 15 countries account for 84 per cent of world steel production.
b. Production figures represent averages for the years 1978-1981.
c. Energy totals are for crude steel-making, including ironmaking.
The aluminium industry provides another case of an energyintensive industry where there is high potential for energy conservation. As table 2 shows, there are still wide disparities in electricity use for aluminium smelting. Energy intensity could be further reduced in this industry to 46.27 GJ/t, using currently available technology (Brown et al., 1985). Recycling can cut energy requirements by over 90 per cent, but recycling rates worldwide averaged only 28 per cent in the early 1980s (Brown et al., 1985).
Table 2 Electricity use in aluminium smelting in major producing countries, ranked by eficiency, 1981
Source: Brown et al., 1985.
a. Average primary production for years 1980-1982.
b. Electric energy equivalent.
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