Innovations in Energy Technology
RICHARD E. BALZHISER
Over the next half century, the developing nations will vastly expand their use of commercial energy to meet the basic needs of their rapidly growing populations. But the drive for improved health, education, and welfare, as well as some measure of economic parity with the industrialized nations, will inevitably lead to pressure on the global environment, including climate. Not surprisingly, then, new, innovative means of global sustainable development will be required, with efficiency forming the backbone of all future strategies of sustainability.
Electricity will play a crucial role in fostering this innovation because of its unique ability to bring precision, control, and versatility to the workplace, and to capture and convey information. But while contributing to a less energy-intensive path, electrification also is among the most capital-intensive of the energy options. Thus it is imperative that electrification strategies crafted for each developing country consider its human, energy, and capital resources and focus on high-leverage applications that improve education and health, thereby enabling industrialization and economic development. Indigenous resources and practices will play important roles as nations seek to find their niches in the global economy.
This paper addresses the role that electricity can and will play in the rapidly globalizing economy. And although the paper concentrates on the new technologies available for generating and delivering electricity, the innovative ways that recently have been found to utilize electricity to improve economic productivity, reduce environmental degradation, and move toward sustainable use of global energy resources are where much of the excitement resides.
Energy use is driven primarily by population growth, economic development, and technological development. Worldwide, population growth is exploding-from 2 billion in 1900 to 5.5 billion in 1995 to perhaps 8-10 billion by the middle of the next century. Much of this growth will occur in the emerging nations where economic development is a top priority, and this development will require prodigious amounts of energy.
World energy use has soared during the last half century (Figure 1), with fossil fuels providing the bulk of the increase; nuclear and hydro (shown in the figure as primary electricity) have made minor contributions. The world now uses over 300 quads of energy a year, with the United States consuming a quarter of that total. Half of the world's people still have no real access to commercial energy, however. Efforts to improve their quality of life will be a major driver in future energy use.
Much of the growth in energy consumption over the next 50-60 years will be fueled by coal, oil, and gas, which are very unevenly distributed around the world. Coal is the overwhelming resource in Asia, Russia, and North America; the only significant supply of oil is in the Middle East, and gas is particularly abundant in the Middle East and the Russian territories. Of the fossil fuels, only coal has staying power, although technology has gone a long way toward increasing the reserve-to-production ratios for both oil and gas in recent years. As for the solar resource, concerted efforts will be made to exploit this resource in the twenty-first century.
A look at the intensity of energy use reveals a number of historic patterns and phenomena. From the beginning of the industrial revolution to just after World War I, the United States went through a development cycle in which the energy input per unit of economic output climbed steadily. At the end of that period, however, the energy intensity of the economy turned down. Why? It was true that automobiles, furnaces, and industrial processes were becoming more efficient, but also electricity was taking root in the economy. In the 1920s, the electric motor unit drive revolutionized manufacturing. Later, it revolutionized the office, home, and farm. As electricity continued to replace less-efficient energy sources, the amount of energy needed to produce a unit of gross national product (GNP) steadily declined. Electricity's fraction of total energy is now approaching 40 percent in the United States and continues to climb.
This phenomena has not been unique to the United States; every industrialized country, beginning with Great Britain in the 1880s and extending through Japan in the l950s (Figure 2), has passed through a similar historic pattern in energy intensity in which, over time, the peak of energy intensity has declined. This pattern has enormous significance for the developing nations. In these nations, energy technology has advanced so rapidly in a historical context that they can pass through the same development cycle using only a fraction of the energy required a century ago.
Although the use of electricity has been closely linked to economic prosperity and improvements in social welfare, electrification has exaggerated the global disparities in energy use (Figure 3). More than a tenfold difference in electric-generating capacity per capita exists between the rich and poor nations, correlated with a nearly a hundredfold difference in per capita GNP. These gaps must be closed. But those working toward that goal must recognize that the type and scale of technology appropriate for the wealthiest nations may be very different than those appropriate for the poorest nations.
As the next century unfolds, the issue of global sustainability will begin to transcend the separate concerns of population, energy, economy, health, social welfare, and the environment. New means of achieving sustainable development will be required, and efficiency is likely to act as the backbone of all future strategies of sustainability. In this, electricity will be important in reconciling human aspirations with resource realities.
Of the trends important to the future direction of energy technology, efficiency is first and foremost. Fossil power plants were only about 5 percent efficient at the turn of the century (Figure 4), but today they are routinely 35 percent or more efficient, even with extensive environmental controls. Tomorrow they will be in the 60-70 percent range, with environmental cleanup integral to the process design. Similar improvements in efficiency are in store for the delivery of power as the “second silicon revolution” takes hold. And on the end-use side, one only has to look at the dramatic improvements in computers over the last few decades to see the potential for more gains in efficiency through electricity.
The wide variety of advance combustion turbines that are emerging will eventually push combustion turbine efficiencies into the 60 percent range. Aeroderivative combustion turbines, which, as the name implies, are derived from today's aircraft fan jets, are more compact than today's heavy frame turbines and are designed for rapid ramp-up to full power. They can achieve efficiencies of nearly 50 percent at the 50-megawatt power level. Advanced cycles of future interest for the aeroderivatives include the steam-injected gas turbine (STIG), the humid air turbine (HAT), and the chemically recuperated, intercooled, steam-injected turbine (CRISTIG).
The combustion turbine, which burns natural gas and is dominating new capacity additions in the United States, is readily transferable to any region of the world where gas or oil is available. The advantages of this turbine include high efficiency, low capital cost, low emissions, modularity, short lead time, and, at least for the foreseeable future, low fuel costs. These machines can be used in simple cycle or coupled with a heat-recovery steam turbine in a combined cycle mode. Because this technology has advanced rapidly, machines with capacities in excess of 250 megawatts are now available in sizes that permit factory fabrication and railway delivery.
Coal, which represents about 80 percent of the world's fossil reserves, is a resource so large and geographically dispersed that the world's dependency on it can only grow. In China and India, coal is destined to be the principal energy pathway for economic development over the next half century. Indeed, by one estimate, to accommodate its growth, China must build one medium-sized power plant every week between now and the end of the decade.
Fortunately, two decades of research on clean coal technologies stand ready to help minimize the environmental impact of coal. These technologies range from coal preparation to post-combustion control. But the real promise lies in technologies for which higher efficiency and environmental cleanup are integral to the engineering design.
Fluidized-bed technologies are particularly attractive near-term options for coal combustion in the 50-100 megawatt range. These systems trap sulfur in a limestone bed and burn cool enough to suppress the formation of nitrogen dioxide.
Perhaps the most significant technology for the long term is the integrated gasification combined cycle (IGCC), which gasifies coal, strips away the impurities in the gas, and then runs the gas through a combustion turbine in combined cycle mode. IGCC systems can be designed to convert coal into many different products, including electricity, chemical feedstocks, and liquid fuels. Advanced versions, now being tested on a pilot scale, replace the combustion turbine with a fuel cell, lifting systems efficiency to about 60 percent.
IGCC is beginning to catch on worldwide (Figure 5). Today, IGCC systems are being planned or under serious consideration in 21 countries, but this is just a start. Close observers of China's energy situation regard IGCC as China's best technology option for the long term. In the United States, the 100-megawatt cool-water facility in the Mojave Desert, first developed 10 years ago by the Electric Power Research Institute (EPRI) and a number of industrial and utility partners, has attracted visitors from many different countries, all eager to see the cleanest power plant in the world.
A comparison of the costs of the five currently available fossil systems that will set the competitive benchmark for electricity generation globally reveals that today's IGCC system can produce power at just over $0.04 per kilowatt-hour (Figure 6). (The kinds of cost figures shown in Figure 6 tend to be very site-specific, and the ones actually used represent some standardized assumption for the United States.) This is comparable to the figures for the traditional pulverized coal plants with flue gas scrubbers, but nearly 20 percent higher than those for gas-fired combustion turbines.
Fuel cells promise to be an especially clean and highly efficient form of dispersed fossil generation. Unlike conventional combustion-based technologies, fuel cells convert fuel to electricity through a flameless oxidation process, much like a battery. Development activities are now focused on the molten carbonate fuel cell, with potential capital costs in the $1,500 per kilowatt range and a thermal efficiency of 54-60 percent. EPRI is participating in a 2-megawatt demonstration in Santa Clara, California.
Further out, researchers are excited about the potential of solid oxide fuel cells for extremely compact, low-cost dispersed generation. Inexpensive units as small as 5 kilowatts (or units as large as 5 megawatts) can be run at 50-SS percent efficiency. Larger cells can produce steam hot enough for industrial applications, boosting total efficiency to the 80 percent range.
Photovoltaic solar technology should head the list of promising technologies for remote applications in the equatorial regions of the world. This technology is modular at scales appropriate for even low-power applications in village life. For example, the some 600,000 villages in India that receive 12 hours of sunlight daily could benefit from the use of “pre-electrification” levels of power for simple lighting and cooking, low-power TV sets, and, in some households, efficient refrigerators.
Even though photovoltaic systems cannot compete today for bulk power generation, they are often the least expensive option for small, distributed applications in remote areas, even in North America. The market is building as costs decline. Worldwide, photovoltaic sales are about 60 megawatts a year and growing between 15 and 20 percent annually.
The real long-term promise of photovoltaics rests on the fact that it is part of the family of solid-state technologies that are still in the early, robust stages of technological discovery and development. Research continues to make great progress: cell efficiencies are climbing; manufacturing techniques are being adapted from integrated circuitry; and costs are falling. In the last decade, costs have fallen from about $1.00 per kilowatt-hour to about $0.30 per kilowatt-hour, and within 20 years these costs are expected to fall even further to between $0.07 and $0.10 per kilowatt-hour.
Most of the focus has been on crystalline silicon flat plate technologies. But others bear watching, for they will extend the range and scale of future application. Thin films of amorphous silicon or other semiconductors have less demanding material requirements and hold out the promise of very low-cost, routine use. Their relatively low efficiencies can be boosted using multiple film “sandwiches” to absorb a broader spectrum of sunlight.
At the other end of the scale, high-concentration systems will become useful for utility applications. A 2-kilowatt installation now going up in Georgia is expected to produce power at 19 percent efficiency-a world record for total systems efficiency. This is expected be followed shortly by a 20-kilowatt system in Arizona able to produce power at about $0.10 per kilowatt-hour.
Solar thermal systems represent another intriguing option for utility-scale application. The most commercially advanced of the various designs is the trough-type collector. In the 1980s, California-based Luz International installed a number of these systems, using as backup a natural gas power generator. The systems were competing, however, in a size range that was the natural niche of combustion turbines, which burst on the scene as a fierce competitor in the late 1980s. Because the turbines could be installed for roughly one-tenth the capital costs of the Luz system ($3,000 per kilowatt-hour), the market failed to develop, and Luz went out of business a few years ago. But interest is rekindling in exporting solar thermal systems to regions of the world without gas supplies. To that end, the Rockefeller Foundation is now trying to pull together the various Luz subcontractors.
Wind energy is coming of age for power production. It has become competitive in the United States; it is rapidly taking hold in Europe; and now it is poised for broad international deployment. The developing nations, particularly India, have shown increasing interest as well.
Technologically, the leader in this field is the variable-speed turbine developed by U.S. Windpower, EPRI, and the U.S. Department of Energy. This turbine is capable of producing electricity for $0.05 per kilowatt-hour, given an average wind speed of 16 miles per hour. The turbines are rated at 350-450 kilowatts and can operate at wind speeds of between 9 and 60 miles per hour. Fierce competition is setting in, and a variety of new wind machines-constant speed and variable speed-should emerge in the next decade. Wind power costs will likely drop to the $0.03 per kilowatt-hour range within the next two decades.
TABLE 1 Cost of Electricity from Renewable Sources (cents per kilowatt-hour), 1995-2010
ªWaste is delivered free at $0.04-$0.05 per kilowatt-hour.
Biomass is a vast resource that includes waste products, as well as crops grown specifically for energy production. The fundamental challenge with biomass, however, is ensuring that its use to produce energy is compatible with other agricultural interests.
To produce energy from biomass, one can either burn the materials directly or convert them to a gaseous or liquid “biofuel” such as ethanol or methanol. Biotechnology is slowly reducing the costs of biofuels by opening up the cellulosic resource base. Waste from lumber and agricultural production currently constitutes the largest source of biomass, but many studies also are looking at short-rotation trees and perennial grasses that could be cultivated specifically for electricity or fuels. Moreover, new conversion technology holds out considerable promise. For example, the World Bank is sponsoring a project in Brazil to gasify a waste product-bagasse from sugar cane-to fuel an advanced combustion turbine. Gasification technology is important worldwide.
The costs of renewable energy are expected to decline substantially over the next 15 years and to reach a new plateau of competitiveness early in the twenty-first century (Table 1). It is conceivable that the economics of some of the more dynamic technologies, such as photovoltaic, could improve even faster. Certainly the incentives are growing, with the emerging markets for dispersed generation in Asia, Africa, and Latin America.
MODULARITY AND DISPERSED GENERATION
Renewables, gas turbines, fuel cells, and other future generating options offer the advantages of modularity-small, factory fabricated, and quickly installed. They can be placed close to the load, deferring the need to build and maintain transmission and distribution lines. As the costs fall, modular units are beginning to challenge the primacy of the central station design, and technical visionaries have begun to describe a tune when the economies of scale will be superseded by the “economies of precision.”
This will open the door to dispersed generation (Figure 7), which may evolve much in the same way the computer industry has seen large mainframe computers give way to small, geographically dispersed desktop and laptop computers. These can be stand-alone units, or interconnected into fully integrated, extremely flexible networks.
DELIVERY OF POWER
New technology also can assist in the challenges of transmitting and distributing power in the developing nations. In the poorer nations, the issues are primarily those of bringing electrification to the countryside - that is, of finding low-cost means of distributing power to often very remote and scattered villages and farms. This typically means running single-phase lines and contending with the myriad problems of maintenance and reliability. Some of the new equipment for condition-based monitoring, for example, could be very helpful in remotely sensing the conditions of breakers, transformers, and substations. With tools such as these, utilities can improve service and minimize the number of qualified technicians required.
At the other end of the spectrum-in the booming economies of some of the Pacific Rim countries-the transmission and distribution problems are somewhat different. Transmission lines tend to be loaded beyond their capacity from continuous growth in electrical demand, and serious power quality problems are emerging from new high-tech loads. The plasma arc of a new minimill, for example, can produce an instantaneous surge in demand of 300 megawatts, which is enough to break a generator shaft.
This is where the thyristor-based technology of the second silicon revolution will have a major impact. Macroelectronics brings the electronic switching capability typically found in microelectronics up to the half-million-volt level, effectively revolutionizing power delivery. Power can be sent to precisely where it is needed; network stability and power quality problems can be controlled; and long transmission lines can be strengthened. Power flow over lines longer than 100 miles is constrained by stability limits. An EPRI-developed Flexible AC Transmission System (FACTS) can provide the additional support required to improve grid stability. Indeed, by using FACTS, a utility can, with a relatively small investment, double the amount of power that goes down a given line. The investment in FACTS to double the amount of power in a 400-mile line, for example, might be as low as $20 million - representing as little as 5 percent of new construction. Given the phenomenal growth in the Asian markets, FACTS technology has a role to play in relieving the burden of new transmission line construction and improving electrical system reliability, which will allow the economies of these countries to flourish.
To appreciate electricity's unique role in the world and to envision the long-term future of energy technology, it is important to recognize that electricity has become the gateway to the electromagnetic spectrum. Gradually more and more parts of the spectrum have been put to work: radio waves for communications, X-rays for medical diagnostics, microwaves and infrared for heating. Now the world is witnessing an explosion of energy-efficient electrotechnologies for industrial use and public works: plasma-fired furnaces, radio-frequency and infrared textile drying, microwave drying of food products, microwave disinfection of medical waste, ultraviolet and electron beam treatment of wastewater, to name a few.
The high-tech world of today will become increasingly dependent on the ability to manipulate the spectrum. The direct result will be an enormous market pull for the efficiency and productivity gains available through high technology. And the indirect result will be better conservation of resources and a reduced environmental impact.
Electricity, whether 50 or 60 cycle or even direct current, can be converted to other forms or frequencies to provide high-value services from light to motive power, from communication networks to medical diagnostics and therapy, and from environmentally clean industrial processes to clean and efficient transportation systems. Just as the environment of many heavy industrial centers has been cleaned up using electric steelmaking and minimill technology, such urban centers as Los Angeles can be cleaned up using increasingly clean vehicles-internal combustion and electric-in this decade.
Heat pump technology continues to improve, providing increased efficiency and comfort with less use of primary energy. More specifically, heat pumps “concentrate” solar energy from the air or ground and deliver it to the home or office with overall efficiencies that exceed 100 percent in terms of energy delivered for each primary unit of fossil fuel used to generate the electricity.
Transportation, space conditioning (heating, cooling, ventilating), and cooking (where microwave and other new technologies are increasing their market penetration) are all potentially high-volume users of electricity in the developed world. For many developing countries, however, better lighting technology, water purification and waste detoxification electrotechnologies, single-phase motors, more efficient and forgiving electrical delivery and storage systems, and even increasingly efficient and affordable photovoltaic and wind machines for remote areas will begin the electrical revolution and will accelerate it for others wanting to speed along the path to a better future.
This being said, some observers have maintained that electricity is too elegant, too inefficient, and too environmentally burdensome to stay the course. These concerns deserve serious consideration if nations are to begin to demonstrate the global stewardship necessary to ensure that today's young people have enough resources to realize their aspirations for a better life.
First, to the point of elegance, electricity is an energy form and indeed the ultimate in elegance and versatility. It is quick (speed of light), clean, and efficient (90+ percent), and it can be produced from any of the natural energy resources-fossil, renewable, or nuclear-as well as waste.
The second point raises the question of efficiency and the historical reality that only 20-30 percent of primary energy can be converted into electricity, with the rest discharged to the atmosphere. Historically, fossil and nuclear energy have relied on the steam turbine to generate electricity. While this technology has improved significantly, the gas turbines currently available are able, in the combined cycle configuration, to convert gas, oil, and gasified coal at efficiencies of from 40 to 60 percent. These efficiencies will continue to rise. Renewable conversion efficiencies also are continuing to rise, and, as they do, the economics will improve because the fuel is either free-water, wind, and sun-or modestly priced-biomass or waste.
Finally, can the environment tolerate the emissions burden that 10 billion people will impose? “Innovation” is the most potent of the renewable resources, and it should be assumed that the future will hold a better understanding of and answers to the climatic concerns, nuclear waste disposal, and recycling opportunities that will extend the earth's finite natural resources.
In energy terms, it seems imperative that the viability of the nuclear resource be sustained and that the ability to use renewables and coal cleanly be improved. While electricity will likely increase its market share as the form of choice, direct heating, furnaces, gas stoves, and internal combustion vehicles and airplanes also are likely to be evident for a long time. Fuel cells will probably offer an opportunity to convert to electricity at the point of use whether in the home, the office, or the automobile. Gasified coal will back up the natural supply of oil and gas and will be used primarily for feedstock and electricity.
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