A little bit of engineering (Несколько текстов для зачёта), страница 7

In some industrialized countries, the electric power industry is being restructured to break up monopolies (the provision of a commodity or service by a single seller or producer) at the generation level. Because this trend is pressuring nuclear plant owners to cut operating expenses and become more competitive, the nuclear power industry in the United States and other western countries may continue to decline if existing nuclear power plants are unable to adapt to changing market conditions.

Asia is widely viewed as the only likely growth area for nuclear power in the near future. Japan, South Korea, Taiwan, and China all had plants under construction at the end of the 20th century. Conversely, a number of European nations were rethinking their commitments to nuclear power.

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Sweden

Sweden’s political parties have committed to phasing out nuclear power by 2010, after Swedish citizens voted in 1980 against future development of this energy source. However, industry is challenging the policy in court. In addition, critics argue that Sweden cannot fulfill its commitment to reducing emissions of greenhouse gases without relying on nuclear power.

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France

France generates 80 percent of its electricity from nuclear power. However, it has canceled several planned reactors and may replace aging nuclear plants with fossil-fuel plants for environmental reasons. As a result, the government-owned electricity utility, Electricité de France, plans to diversify the country’s electricity-generating sources.

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Germany

The German government announced in 1998 a plan to phase out nuclear power. However, as in Sweden, nuclear plant owners may take the government to court to seek compensation for plants shut down before the end of their operating lives.

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Japan

In Japan, several accidents at nuclear facilities in the mid-1990s have undercut public support for nuclear power. Japan’s growing stockpile of plutonium and its shipments of spent nuclear fuel to Europe have drawn international criticism.

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China

China, which currently operates only three nuclear power plants, has plans to expand its nuclear capabilities. However, whether China will be able to obtain sufficient financing or whether it can develop the necessary skilled work force to expand is uncertain.

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Eastern Europe

A number of eastern European countries—including Russia, Ukraine, Bulgaria, the Czech Republic, Hungary, Lithuania, and Slovakia—generate electricity from Soviet-designed nuclear reactors that have various safety flaws. Some of these reactors have the same design as the Chernobyl reactor that exploded in 1986. The United States and other western countries are working to address these design problems and to improve operations, maintenance, and training at these plants.

VII

SOLAR ENERGY

Solar energy does not refer to a single energy technology but rather covers a diverse set of renewable energy technologies that are powered by the Sun’s heat. Some solar energy technologies, such as heating with solar panels, utilize sunlight directly. Other types of solar energy, such as hydroelectric energy and fuels from biomass (wood, crop residues, and dung), rely on the Sun’s ability to evaporate water and grow plant material, respectively. The common feature of solar energy technologies is that, unlike oil, gas, coal, and present forms of nuclear power, solar energy is inexhaustible. Solar energy can be divided into three main groups—heating and cooling applications, electricity generation, and fuels from biomass.

A

Heating and Cooling

The Sun has been used for heating for centuries. The Mesa Verde cliff dwellings in Colorado were constructed with rock projections that provide shade from the high (and hot) summer Sun but allow the rays of the lower winter Sun to penetrate. Today a design with few or no moving parts that takes advantage of the Sun is called passive solar heating. Beginning in the late 1970s, architects increasingly became familiar with passive solar techniques. In the future, more and more new buildings will be designed to capture the Sun’s winter rays and keep out the summer rays.

Active solar heating and solar hot-water heating are variations on one theme, differing principally in cost and scale. A typical active solar-heating unit consists of tubes installed in panels that are mounted on a roof. Water (or sometimes another fluid) flowing through the tubes is heated by the Sun and is then used as a source of hot water and heat for the building. Although the number of active solar-heating installations has grown rapidly since the 1970s, the industry has encountered simple installation and maintenance problems, involving such commonplace occurrences as water leakage and air blockage in the tubes. Solar cooling requires a higher technology installation in which a fluid is cooled by being heated to an intermediate temperature so that it can be used to drive a refrigeration cycle. To date, relatively few commercial installations have been made.

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Generation of Electricity

Electricity can be generated by a variety of technologies that ultimately depend on the effects of solar radiation. Windmills and waterfalls (themselves very old sources of mechanical energy) can be used to turn turbines to generate electricity. The energies of wind and falling water are considered forms of solar energy, because the Sun’s heating power creates wind and replenishes the water in rivers and streams. Most existing windmill installations are relatively small, containing ten or more windmills in a grid configuration that takes advantage of wind shifts. In contrast, most electricity from hydroelectric installations comes from giant dams. Many sites suitable for large dams have already been tapped, especially in the industrialized nations. However, during the 1970s small dams used years earlier for mechanical energy were retrofitted to generate electricity.

Large-scale hydroelectric projects are still being pursued in many developing countries. The simplest form of solar-powered electricity generation is the use of an array of collectors that heat water to produce steam to turn a turbine. Several of these facilities are in existence.

Other sources of Sun-derived electricity involve high-technology options that remain unproven commercially on a large scale. Photovoltaic cells (see Photoelectric Effect; Solar Energy), which convert sunlight directly into electricity, are currently being used for remote locations to power orbiting space satellites, gates at unattended railroad crossings, and irrigation pumps. Progress is needed to lower costs before widespread use of photovoltaic cells is possible. The commercial development of still other methods seems far in the future. Ocean thermal conversion (OTC) generates electricity on offshore platforms; a turbine is turned by the power generated when cold seawater moves from great depths up to a warm surface. Also still highly speculative is the notion of using space satellites to beam electricity via microwaves down to Earth.

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Biomass

Fuels from biomass encompass several different forms, including alcohol fuels (mentioned earlier), dung, and wood. Wood and dung are still major fuels in some developing countries, and high oil prices have caused a resurgence of interest in wood in industrialized countries. Researchers are giving increasing attention to the development of so-called energy crops (perennial grasses and trees grown on agricultural land). There is some concern, however, that heavy reliance on agriculture for energy could drive up prices of both food and land.

D

Current Status

The total amount of solar energy now being used may never be accurately estimated, because some sources are not recorded. In the early 1980s, however, two main sources of solar energy, hydroelectric energy and biomass, contributed more than twice as much as nuclear energy to the world energy supply. Nevertheless, these two sources are limited by the availability of dam sites and the availability of land to grow trees and other plant materials, so the future development of solar energy will depend on a broad range of technological advances.

The potential of solar energy, with the exception of hydroelectricity, will remain underutilized well beyond the year 2000, because solar energy is still much more expensive than energy derived from fossil fuels. The long-term outlook for solar energy depends heavily on whether the prices of fossil fuels increase and whether environmental regulations become stricter. For example, stricter environmental controls on burning fossil fuels may increase coal and oil prices, making solar energy a less expensive energy source in comparison.

VIII

GEOTHERMAL ENERGY

Geothermal energy, an aspect of the science known as Geothermics, is based on the fact that the earth is hotter the deeper one drills below the surface. Water and steam circulating through deep hot rocks, if brought to the surface, can be used to drive a turbine to produce electricity or can be piped through buildings as heat. Some geothermal energy systems use naturally occurring supplies of geothermal water and steam, whereas other systems pump water down to the deep hot rocks. Although theoretically limitless, in most habitable areas of the world this subterranean energy source lies so deep that drilling holes to tap it is very expensive.

IX

ENERGY EFFICIENCY IMPROVEMENTS

In addition to developing alternative sources of energy, energy supplies can be extended by the conservation (the planned management) of currently available resources. Three types of possible energy conservation practices may be described. The first type is curtailment, that is, doing without—for example, closing factories to reduce the amount of power consumed or cutting back on travel to reduce the amount of gasoline burned. The second type is overhaul, that is, changing the way people live and the way goods and services are produced—for example, slowing further suburbanization of society, using less energy-intensive materials in production processes, and decreasing the amount of energy consumed by certain products (such as automobiles). The third type involves the more efficient use of energy, that is, adjusting to higher energy costs—for example, investing in cars that go farther per unit of fuel, capturing waste heat in factories and reusing it, and insulating houses. This third option requires less drastic changes in lifestyle, so governments and societies most commonly adopt it over the other two options.

By 1980 many people had come to recognize that increased energy efficiency could help the world energy balance in the short and middle term, and that productive conservation should be considered as no less an energy alternative than the energy sources themselves. Substantial energy savings began to occur in the United States in the 1970s, when, for example, the federal government imposed a nationwide automobile efficiency standard and offered tax deductions for insulating houses and installing solar energy panels. Substantial additional energy savings from conservation measures appear possible without dramatically affecting the way people live.

A number of obstacles stand in the way, however. One major roadblock to productive conservation is its highly fragmented and unglamorous character; it requires hundreds of millions of people to do mundane things such as turning off lights and keeping tires properly inflated. Another barrier has been the price of energy. When adjusted for inflation, the cost of gasoline in the United States was lower in 1998 than it was in 1972. Low energy prices make it difficult to convince people to invest in energy efficiency. From 1973 to the mid-1980s, when oil prices increased in the United States, energy consumption per person dropped about 14 percent, in large part due to conservation measures. However, because oil has become cheaper during the 1990s, the U.S. Energy Department predicts that by the year 2000 energy use in the United States will increase to within 2 percent of 1973 levels. Over time, improvements in energy efficiency more than pay for themselves. However, they require large capital investments , which are not attractive when energy prices are low. Major areas for such improvements are described below.

A

Transportation

Whereas transportation uses 25 percent of the total energy consumed in the United States, it accounts for 66 percent of the oil used in the United States. Cars built in other countries have long tended to be more efficient than American cars, partly because of the pressures of heavy taxes on gasoline. In 1975 the U.S. Congress passed a law that mandated doubling the fuel efficiency of new cars by 1985. This law, coupled with gasoline shortages in 1974 and 1979 and substantially higher gasoline prices (especially since 1979), caused the average efficiency of all U.S. cars to improve by about 40 percent between 1975 and 1990. However, much of this improvement has been offset by dramatic increases in the number of cars on the road and by the growth in sales of sport utility vehicles and light trucks (which are not covered by federal efficiency standards). By 1996 the number of automobiles used worldwide had grown to 652 million vehicles. This number is expected to increase to nearly 1 billion by 2018. Experts predict that unless more efficient technologies are developed, this growth will raise demand for gasoline by over 20 million barrels per day. Automobile manufacturers have the technical capability today to build cars with a much higher fuel efficiency than that mandated by Congress. Mass-production of cars with this efficiency would require vast capital investments, however. New engine technologies that rely on electric batteries or highly efficient fuel cells, as well as engines that run on natural gas, may play a much greater role in the early 21st century. Increases in the prices of gasoline and parking have encouraged two other modes of transportation: ride sharing (either van or car pools) and public transportation. These methods can be highly efficient, but the sprawling character of many U.S. cities can make their use difficult.

B

Industry

Profit-conscious business managers increasingly emphasize the modification of products and manufacturing processes in order to save energy. The industrial sector, in fact, has recorded more significant improvements in efficiency than either the residential or the transportation sector. Improvements in manufacturing can be classified into three broad, somewhat overlapping, categories: improved housekeeping—doing routine maintenance on furnaces and using only necessary lighting; recovery of waste—recovering heat and recycling waste by-products; and technological innovation—redesigning products and processes to embody more efficient technologies.

C

Buildings

In the 1950s and 1960s efficient energy use was often neglected in constructing buildings and houses, but the high energy prices of the 1970s changed that. Some office buildings built since 1980 use only a fifth of the energy used in buildings constructed just ten years earlier. Techniques to save energy include designing and siting buildings to use passive solar heat, using computers to monitor and regulate the use of electricity, and investing in more efficient lighting and in improved heating and cooling systems. A life-cycle approach, which takes into account the total costs over the entire life of the building rather than merely the initial construction cost or sales price, is encouraging greater efficiency. Also, the retrofitting of old buildings, in which new components and equipment are used in existing structures, has been successful.