Taking a train ride across Denmark, a small, tidy country with lots of rich farmland, is a unique visual experience these days. At almost any point on the journey, you can spot at least one or two giant, three-bladed wind turbines turning slowly in the breeze, quietly and cleanly converting currents of air into currents of electricity. These gleaming white machines now produce a full 7 percent of Denmark's electricity.
Unlike conventional power plants, which are owned by large private or public companies, Denmark's wind turbines are often owned by the farmers on whose land they stand, or by farmers' cooperatives. The revenue produced by the wind turbines typically flows directly into the local community, and to the manufacturers and service firms that maintain them. Denmark also draws on a form of renewable energy known as biomass (biological materials derived from plants). Small, locally based power plants burn straw and other agricultural waste to produce electricity as well as hot water for local heating.
The rapid transformation of Denmark's energy system during the last ten years may turn out to be the leading wave of something much larger. Around the world, new energy technologies that do not rely on fossil fuels such as coal, petroleum, and natural gas are moving from the experimental stage to commercial reality. Sunlight, wind, and other renewable resources are increasingly converted into useful forms of energy with ever-greater efficiency. The new technologies still provide less than 1 percent of the world's energy supply, but they appear to be advancing rapidly.
The timing of these advances could be of critical importance to the future of modern civilization. Most experts believe that an energy system based on fossil fuels cannot be sustained for another century. According to several recent estimates based on currently known oil reserves, oil production will peak within the first 10 to 20 years of the 21st century.
Even if additional reserves are discovered, many scientists say that continued reliance on fossil fuels as a primary energy source over the coming decades could release into the atmosphere billions of metric tons of carbon dioxide and other heat-trapping gases. International efforts, including the December 1997 Kyoto Protocol, are already underway to cap emissions of these gases, which many scientists have linked to global warming (an increase in the earth's surface temperature). But the efforts of fossil fuel-dependent companies to thwart emissions caps may delay ratification and implementation of the protocol.
Many experts believe a transition toward renewable, carbon-free energy technologies would go a long way toward addressing the problems of dwindling oil reserves and the potentially ruinousenvironmental impacts linked to the burning of fossil fuels. Such a transition could make the 21st century the age of renewable energy.
Energy for the 21st Century
It has been nearly a century since the world had a comparable opportunity to change its energy system. Much of the system now in place was created in an explosion of invention that began around 1890 and was largely completed by 1910. Cities all over the world were transformed as automobiles and electric lights replaced horse-drawn carriages and gas lamps. Technologies that had prevailed for centuries became obsolete in a matter of years, and the 20th century emerged as the age of fossil fuels.
Some observers believe that a series of revolutionary new technologies?including advanced solar cells, wind turbines, and fuel cells?are in about the same place today that the internal-combustion engine and electromagnetic generator occupied in the 1890s. These key technologies have already been developed and commercialized, but they only occupy small niche markets. In the next century these devices could lead to a new generation of mass-produced machines?machines that efficiently and cleanly provide the energy that enables people to take a hot shower, sip a cold drink, or surf the Internet.
Thanks to a potent combination of advancing technology and government incentives, renewable energy may finally be coming of age. Signs of this change are visible in world energy markets. In the 1990s wind power generation grew at a rate of 25.7 percent per year, and production of solar energy expanded 16.8 percent annually. During the same period, oil production grew just 1.4 percent per year. As the computer industry discovered not long ago, double-digit growth rates can rapidly turn a tiny economic sector into a giant.
Advances in electronics, software, and synthetic materials are likely to play a key role in any new energy system. The silicon semiconductor chip, a technology that is less than 40 years old, is now used in nearly every industry. Increased processing power and the miniaturization of electronic devices make it possible to control nearly all energy devices more efficiently, opening new ways of producing, consuming, and conserving energy. Using the latest semiconductor chips, for example, the blades of a wind turbine can now be precisely and inexpensively positioned to maximize efficiency. Developments in chemistry and materials science may also offer critical breakthroughs in the years ahead, allowing the creation of a new generation of sophisticated, lightweight materials.
The 21st century may be as profoundly shaped by the move away from fossil fuels as the 20th century was marked by the move toward them. But most experts believe a new energy system will take decades to develop. Investment in the current system is massive, and enormous resources will be required to build a new one. As events in the late 19th century demonstrated, however, underlying markets can shift abruptly, drying up sales of traditional energy and transportation sources and affecting scores of industries. The economic health and political power of entire nations may be boosted, or in the case of some countries that now rely on oil production, sharply diminished. Nations, industries, cities, homes, and lives will likely be reshaped in ways that cannot be fully anticipated.
A wide range of renewable energy resources could play an important role in the 21st century. These include ancient sources of power, such as the wind and sun, as well as comparatively new forms of power, such as the fuel cell. A host of other resources, including geothermal heat, biomass, and ocean power, may also figure prominently in the world's next energy system.
Wind Power
Technological advances are breathing new life into an energy source long tapped by humans: the wind. The first windmills for grinding grain appeared in Persia just over 1,000 years ago. They later spread to China, throughout the Mediterranean, and then to northern Europe, where the Dutch developed the towering windmills for which the country is still known. The technology found other applications, including pumping water for irrigation and drinking in the American West in the late 19th century. But it was not until the late 1970s, when Danish researchers applied advanced engineering and materials to wind-power generation, that the technology emerged as a potentially serious competitor to fossil fuels.
The Danes invented a machine composed of three propeller-like fiberglass blades that point upwind of a steel tower, on which they are mounted. The latest versions, manufactured by companies based in Germany, India, Spain, and the United States, have aerodynamic blades up to 40 m (130 ft) long. These spinning blades use a system of gears to translate their power to an electronic drive with sophisticated microprocessor controls. The generator is housed atop the tower, and like all electric generators it uses spinning magnets to create an electrical field.
Roughly 40,000 of these machines were in place worldwide by the end of 1998. In Germany, the wind industry has grown spectacularly in the 1990s. Germany's total wind generating capacity even surpasses that of Denmark, having crossed the 1 percent threshold in 1998. In the windy northern state of Schleswig-Holstein, wind power accounts for 12 percent of the total electricity generated.
The cost of wind-generated electricity is already competitive with coal-fired plants, the world's leading source of electricity. Growing markets are fueling investment in the technology, which is expected to further drive costs down. Enron Corporation, the largest natural gas company in the United States, recently purchased two wind-power manufacturing companies and is developing projects around the world. Two large Japanese trading companies have announced plans to develop extensive wind-energy projects, as has a subsidiary of a major U.S. electric utility company. And companies in Denmark and The Netherlands are making plans to build offshore wind farms in the North Sea.
Wind energy is a widely available resource. In the United States, for example, sufficient winds for extensive electricity production are found in New England, the central Appalachian Mountains, around the Great Lakes, in the upper Midwest, across the Great Plains and Rocky Mountain states, and along the coastal range of the West Coast. Some experts have estimated that wind harnessed in North Dakota, South Dakota, and Texas could supply all U.S. electricity needs.
Particularly windy regions outside the United States include Patagonia in South America and the steppes of Central Asia. In northwestern China, the wind resource base has been conservatively estimated at 350,000 megawatts, sufficient to provide all of China's electricity.
One obstacle to the development of wind energy on a greater scale is that some of the world's largest wind resources are found significant distances from major urban and industrial centers. Developers are hesitant to invest in large wind farms without guaranteed access to markets, which in some cases would require the construction of expensive new transmission lines. But as the cost of wind turbines continues to fall, developers in some remote wind-rich regions, including Patagonia and the state of Wyoming, are considering building the additional transmission lines that are needed.
Objections to wind power include the aesthetic impact of wind turbines on the visual landscape, noise from the spinning rotors, and their potential to harm birds. However, careful siting of the turbines can reduce their visual presence, and design advances are reducing wind and mechanical noise. In addition, experts are currently studying ways to keep birds from striking the rotors.
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