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 Kyōto 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 ruinous environmental 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.
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.
Solar power is another ancient energy source that has benefited from developments in modern technology. The oldest forms of solar power used sunlight as a direct source of heat energy. One simple device used to reflect solar energy, the parabolic mirror (a dish with a concave reflective surface), can be traced to 3rd century BC Greek mathematician and inventor Archimedes. In 1882 the Frenchman Abel Pifre demonstrated that a parabolic mirror could reflect and focus the sun's rays onto a water boiler, producing sufficient steam power to operate a small printing press. Several modern solar power stations use an array of such reflectors, which move to track the sun, focusing solar energy onto a central boiler.
A relatively new form of solar power, the photovoltaic cell, converts sunlight directly into electricity. The photovoltaic cell is a semiconductor device, closely related to a computer chip, that relies on the photoelectric effect. Discovered by French scientist Antoine Edmund Becquerel in 1839, the photoelectric effect describes how sunlight can create an electric current by generating electrically charged particles.
Developed by scientists at Bell Laboratories in 1954, modern solar cells are generally made of crystalline silicon, a semimetallic element. Photovoltaic cells were first developed in the 1960s as a power source for orbiting spacecraft in the U.S. space program. They are now widely used as a power source for satellites, remote communications systems, traffic signs, and consumer electronic devices such as pocket calculators and watches. Advancing technology has driven production costs down by 80 percent in the past 20 years, and solar electricity is beginning to emerge as a potential competitor to fossil fuels.
In one new application, several companies have integrated solar cells into a new generation of roofing shingles, tiles, and window glass, allowing homes and office buildings to generate their own electricity. In the United States, a home equipped with this technology costs roughly $20,000 more than an average, traditionally powered home. A significant market for this technology is emerging in Japan, due to a system of government supports introduced in 1995. By the end of 1998, Japan is expected to have at least 25,000 solar-powered homes-enough to electrify a city of 100,000 people.
Both the United States and the European Union (EU) announced solar-roof programs in 1997. These programs, which are still being formulated, are partnerships with state and local governments as well as the private sector. They are intended to provide tax incentives, low-cost financing, and other assistance for those who want to use solar power.
The main impediment to increased reliance on solar power is cost. Most experts believe the cost of solar cells must fall by 50 to 75 percent to be fully competitive with coal-fired electricity. Automated manufacturing, larger factories, and more efficient cells may deliver major cost reductions in the near future. But for now, solar cells are used primarily in remote locations, where access to other forms of power is sharply constrained.
One breakthrough that promises to significantly reduce costs is the development of a new generation of thin-film solar cells. These cells are less than one one-hundredth the thickness of conventional solar cells. They do not need to be sliced or rigidly encased, eliminating a costly process, and they can be made into large, flexible sheets ideal for integration into building materials. Thin-film solar cells also use less raw material, further reducing costs.
The technology with the most potential to reshape the world energy economy in the century ahead may be the fuel cell. The principle behind fuel cells was first discovered in 1829, nearly 50 years before the first internal-combustion engine. Fuel cells are electrochemical devices that combine hydrogen and oxygen in an electrolyte fluid (a solution of ions that conducts an electric current), creating an electrical charge across a membrane. The reaction produces a steady flow of electricity. Unlike most power plants, which use mechanically spinning generators, fuel cells have no moving parts.
The fuel-cell concept first attracted interest in the late 19th century, when a fuel cell three times as efficient as American inventor Thomas Edison's best electric generator was demonstrated. But the technology was expensive, and interest in the concept withered. Advances in materials and electronics were necessary to make fuel cells useful and practical. In the 1960s fuel cells captured the interest of the U.S. space program, which developed small, efficient fuel cells for use in spacecraft. These orbiting fuel cells were expensive, but by the 1980s—in the wake of the 1970s oil shortages—they had again attracted the interest of government researchers and investors.
Fuel cells are roughly twice as efficient as conventional engines in converting fuels to mechanical or electrical power. They require little maintenance, are nearly silent, and emit only water vapor. Along with the solar cell, some experts believe the fuel cell could allow human civilization in the 21st century to step beyond the age of fire (combustion), which has provided the bulk of the world's energy for more than ten millennia.
Unlike most power plants, where larger facilities were long associated with lower costs per unit of energy, fuel cells are nearly as economical on a small scale as on a large one. Researchers are particularly interested in the proton-exchange-membrane (PEM) fuel cell, a design that is now being studied as a potential motor vehicle engine, small-scale electricity generator, and even as a power source for laptop computers. Ballard, a Canadian company that has invested heavily in PEM fuel cells, believes the cells can eventually produce electricity at less than $100 per kilowatt, undercutting modern coal-fired power plants by a factor of five or more.
The first generation of fuel cells will likely obtain hydrogen from natural gas, which can be separated into hydrogen and carbon dioxide when it is heated. But the long-term goal is to use hydrogen directly. Hydrogen is the most abundant element in the universe and is found on earth as a component of water. Hydrogen can be produced from water through electrolysis, which involves splitting water molecules into oxygen and hydrogen by running an electric current between submerged electrodes.
Electricity generated from renewable resources can produce hydrogen through electrolysis, but the process is expensive using currently available technologies. Chemists recently developed a solar-powered “water splitter” that nearly doubles the efficiency of converting solar energy to hydrogen. But the procedure is costly, using two different semiconductors. Finding less-expensive semiconductors is one key to making the device economical. Some experts believe that the discovery of an inexpensive and efficient way to electrolyze water would make hydrogen-powered fuel cells the world's dominant energy carrier within a few years.
Until that occurs, natural gas could form a kind of bridge to a hydrogen-based energy system. Natural gas is more abundant than oil, and it has been less heavily exploited, raising the prospect that it will be an important energy source early in the next century. Because the system for transporting natural gas can also be used to carry hydrogen, a separate system for hydrogen could be built up gradually. One approach would be to mix hydrogen with natural gas and carry the fuels in the same pipelines, shifting later to new pipelines that are designed to carry pure hydrogen.
Other Energy Alternatives: Geothermal, Biomass, and Ocean Power
Three other renewable energy sources may play an important part in the next century's energy system. Geothermal heat, found deep in the earth's crust, can be captured for direct heating, or it can be used to generate electric power. Hot springs, which transfer some geothermal heat to the earth's surface, have been used since ancient times for recreation, therapy, and heating purposes. The first facility to turn geothermal heat into electricity, by using steam to spin a mechanical turbine, was built in Tuscany, Italy, in 1904.
Some 8000 megawatts of electricity around the world are currently generated from geothermal energy, a tiny fraction of global electrical production. The world's largest geothermal energy complex is located at The Geysers in northern California. It has a production capacity of more than 1200 megawatts—enough electricity to satisfy most of the daily power demands of a city the size of San Francisco. Geothermal power plants also operate in Nevada, Oregon, Utah, and Hawaii. Iceland sits atop a massive volcanic system, and geothermal energy heats most of the country's homes. Other regions that have access to large reserves of geothermal energy are Mexico, Central America, Indonesia, and the Philippines.
Although the potential to tap geothermal energy around the globe is almost without limit, in many regions adequate heat to generate electricity lies 5 km (3 mi) or more beneath the earth's surface. Drilling holes to access that heat can be prohibitively expensive.
Biomass provides another ready source of renewable energy. Agricultural wastes, ranging from sugarcane bagasse (the pulpy waste remaining after the cane is crushed) to rice hulls, can be burned directly or turned into combustible gases or liquids, such as ethanol. These products are currently used to produce electricity and as a substitute for petroleum. In Brazil, waste materials from the sugar industry alone could, in theory, provide most of the country's power. Ethanol from sugarcane already supplies half of Brazil's automotive fuel. The United States government is currently subsidizing efforts to turn Midwestern corn into ethanol for use as a transportation fuel.
Advocates argue that efficient use of biomass will not lead to an increase in atmospheric concentrations of carbon dioxide because newly planted crops—a primary source of biomass—will absorb any carbon dioxide produced. But the price of biomass fuels cannot yet successfully compete with fossil fuels in most markets. Technological advances that allow biomass to be converted into fuels with greater efficiency could eventually make biomass a competitive alternative.
Scientists are also looking at ways to tap the energy embodied in the ocean's tides, waves, currents, and temperature differentials. Two sizeable tidal power installations are currently in place, including a facility in Nova Scotia's Annapolis Basin that has been in service since 1984. Owned by the Tidal Power Corporation, a public company, the project captures energy from the tremendous movement of water in the Bay of Fundy.
Some researchers believe the most promising of these ocean energy technologies is ocean thermal energy conversion (OTEC), a process that uses temperature differences in the ocean to create electricity. The process works by capturing the heat differential between the warm water on the ocean's surface and the colder water below to drive a generator. Proponents believe that these naturally occurring temperature gradients have the potential to produce millions of megawatts of electricity, but the technology is still at an experimental stage.
The Falling Cost of Renewables
The major obstacle to increased use of renewable energy technologies remains their high cost relative to fossil fuels. As a result, most of the new technologies currently remain at the niche stage. Those niches are growing rapidly, however. As markets expand, manufacturers of the new technologies can shift toward mass production, a process that can dramatically lower costs.
Solar cells, for example, have gone from powering satellites and remote communication systems to providing energy for a growing range of applications that are not connected to a main power grid, including consumer electronic devices, highway signals, and water pumps.
Remote military bases, island resorts, and wastewater treatment plants are among the niches where fuel cells may soon gain a foothold. Some companies are focusing on developing tiny fuel cells for laptop computers and cellular phones; weighing half as much as conventional batteries, they can supply 50 times as much power.
Decentralizing the Energy System
Since the first human dwellings were constructed tens of thousands of years ago, much of our energy use has occurred inside the home. But in recent decades, that energy supply has come from increasingly distant sources, some of them halfway around the world. Many experts believe that the 21st century energy system will be marked by decentralization—a reversal of the current trend toward ever-larger power plants and growing distances between the sources and the consumers of power.
A decentralized energy system, which locates an affordable and accessible source of power near its point of use, might combine a range of new energy technologies—for example, electricity-generating fuel cells in basements, rooftop solar panels, and wind turbines scattered across pastures. In the past, many people within the energy industry argued that such a system would be unreliable and chaotic, subject to frequent disruptions and sharply fluctuating prices. However, recent developments in instantaneous telecommunications and sophisticated electronic controls may help solve this problem. According to some experts, the technology already exists to coordinate thousands—even millions—of individual generators, turning them on and off as readily as computers on the Internet can send and receive information.
A number of communications companies, including Motorola, Inc., and Pacific Bell, are developing the means to operate a diversified, “intelligent” power system. The generators would supply power to the grid when demand was high, and batteries would draw and store energy when demand was low. The idea behind such a system is to use computer controls to fine-tune the balance between energy supply and demand, increasing the efficiency promised by the new technologies and reducing costs throughout the entire power system.
A major challenge in the move toward increased use of renewable forms of energy is that these resources are by nature intermittent and may not always be available when needed. As long as these energy sources are contributing less than 30 percent of the power in a given region, existing electricity grids will probably have enough reserve generating capacity to ensure reliability. But as these new energy sources become increasingly dominant, the system as a whole will need to be adapted. The simplest solution is to build backup generators that employ efficient gas turbines and a variety of sophisticated energy storage devices.
Preparing for an Energy Revolution
Like the computer industry, with which it shares many technologies, the renewable energy business is being led by dozens of entrepreneurial start-up companies, many financed with venture capital. As business has boomed in the late 1990s, major corporations have jumped in as well. British Petroleum Company PLC, General Electric Company, and Royal Dutch/Shell Group are among the large companies that have stepped up their investments in renewable energy technologies.
The pace and extent of the move toward renewable energy in the next century will depend on many factors. Foremost among them are the relative expense of fossil fuels and the intensity of opposition to renewable energy coming from powerful oil and electric power companies. International initiatives, such as the Kyōto Protocol, which ultimately could serve to depress demand for fossil fuels, may have an important impact. And the willingness of governments to fund research, enact tax incentives, and break open electric utility monopolies, could also encourage the turn toward renewable energy sources.
Many economists argue that because it is difficult and expensive to find an alternative to fossil fuels, the transition should be delayed for as long as possible. But their position may be based on a technological pessimism that is out of place today. The first automobiles and computers were costly and difficult to use, but the pioneers persevered, made improvements, and ultimately triumphed in the marketplace. Just as automobiles followed horses and computers displaced typewriters, so the advance of technology may one day make smokestacks and gasoline-powered automobiles look primitive and uneconomical.