Will a viable alternative to the internal combustion engine exist within the next decade

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ENGINEERING

Will a viable alternative to the internal combustion engine exist within the next decade?

Viewpoint: Yes, battery-powered, fuel-cell electric, and hybrid vehicles are technologically viable alternatives to the internal combustion engine now, and they are likely to be economically viable within the decade.

Viewpoint: No, current internal combustion engine technology has many advantages over its potential competitors—lower costs of production and operation, a longer driving range before refueling, and better overall performance—that will ensure its dominance for several decades to come.

The internal combustion engine is a versatile power source, used in everything from lawn mowers to rockets. However, it is most commonly associated with the car and other road transport vehicles, and it is this association that has come under increasing criticism and scrutiny in recent years. With a growing awareness of the risks of pollution to both health and the environment, the internal combustion engine has become less desirable, and practical alternatives are being sought by governments, corporations, and environmental groups worldwide.

Essentially, an internal combustion engine works like a cannon. A flammable substance, such as gasoline, is ignited in a small, enclosed space, and the resulting explosion releases energy in the form of expanding gas that can propel an object with great force. A typical car engine has hundreds of such explosions a minute, and harnesses some of the energy produced to turn the drive shaft. As the name implies, the combustion takes place inside the engine, as opposed to an external combustion engine, where the fuel burns outside of the engine, such as in a steam-powered train.

Today, the internal combustion engine is the dominant vehicle engine the world over. However, there were many other alternatives proposed and produced in the early days of automobiles, including electric, steam, and even liquid air-powered cars. The first electric motor was produced in 1833, and many models of electric cars were available from the 1880s to the turn of the century. Steam cars were also produced in the 1880s. The first gasoline-fuelled, internal combustion engine cars were built in 1891 and quickly made an impact. They had a much longer range than electric cars, and competed well against steam cars in endurance races.

Early electric and steam cars had many advantages over rival internal combustion models, including speed. In 1898 an electric car achieved the record speed of 39.25 mph (63 km), and a year later another electric model went over 65 mph (104.6 km). That record held until 1902, when a steam power vehicle reached 75.06 mph (121 km). Electric cars were also quieter—some were almost silent—and did not produce unpleasant exhaust fumes.

However, the internal combustion engine, while noisier, hotter, and dirtier than electric motors, began to dominate the car market. Other types of cars had their own problems. Early electric batteries were heavy and corroded quickly, needing to be replaced every two years, and there were many cases of battery leaks producing noxious fumes. Gasoline became cheaper; the speed, performance, range, and durability of the internal combustion engine were improved; and consumers began to prefer the noise and power of the internal combustion engine-driven car. The electric engine came to be associated with senior citizens, while the petrol engine was seen as progressive, reliable, and perhaps most importantly, cheaper to buy and run. The internal combustion engine thus prevailed.

However, while the internal combustion engine-driven car dominated the twentieth century, the twenty-first seems likely to see the reintroduction of electric cars. There are compelling reasons to find alternatives, from a greater awareness of the effects of pollution and fears over global warming, to concerns that the supply of oil is drying up, or at least becoming more expensive to find and extract.

Many different types of cars are being developed. Most of the problems that plagued the battery-powered car of the nineteenth century have been resolved. Modern car batteries are safer, last longer, and provide more power than previous-generation batteries. Another alternative electric car type uses fuel cells, which produce electricity rather than storing it as long as there is fuel in the cell. The standard fuel for fuel cells is hydrogen, which is a cheap and plentiful gas but which is also extremely flammable, and is often linked in the public mind with the Hindenburg airship disaster.

Hybrid engines have also been proposed. These use either a combination of two alternative technologies, such as fuel cells and batteries, or one alternative technology with a standard internal combustion engine. While many of these combinations result in a longer drive range and improved performance, the need to have two engines adds weight and size to the vehicle.

There is much debate over which alternative engine or combination is best able to reduce car emissions and still provide the consumer with the necessary power and range. Currently, there are a bewildering choice of options, each requiring its own infrastructure of refuelling stations and service industries. A number of different alternative vehicles are in use all over the world, and are particularly successful in niche areas, such as inner-city transport. However, it seems likely that only a few, possibly just one, will emerge as a serious challenger to the internal combustion engine.

The same concerns over the environment that have given rise to alternative engine research have also resulted in many recent improvements to the internal combustion engine. Modern cars have significantly lower emissions of undesirable gases than those of a few decades ago, and are more fuel efficient. Yet at the same time, car manufacturers have made and promoted larger cars, which tend to have lower fuel efficiency.

Perhaps the biggest negative factors that alternative car engines have to overcome are not technical, but economic and perceptual. Currently the cost of alternative cars is much higher than standard vehicles. While mass production techniques will bring prices down, it may still be many years before they approach parity with internal combustion engine cars. Operating costs also need to be lowered, and the availability of refuelling stations needs to be increased. Public perception also needs to be changed if alternative engines are to become desirable. Whatever the realities, electric cars are still seen by the majority of car buyers as small, powerless, and operable only over short distances.

There is a seemingly unstoppable trend to new engines in cars to replace the long-serving internal combustion engine, for a variety of compelling reasons. However, when such technology will become commonplace on the roads is still an open question.

—DAVID TULLOCH

Viewpoint: Yes, battery-powered, fuel-cell electric, and hybrid vehicles are technologically viable alternatives to the internal combustion engine now, and they are likely to be economically viable within the decade.

Not only will a viable alternative to the internal combustion engine exist within the next decade, it exists today, although the term "viable" may be cause for disagreement. Applying Webster's definition of viable as "workable and likely to survive or have real meaning" raises new questions: viable technologically or viable economically? Technologically, the answer is "yes." The alternative to the internal combustion engine is the electric powered vehicle. Small numbers of battery-powered, fuel-cell electric, and hybrid electric vehicles are in use today, and there is a worldwide race to get more of the new technology vehicles on the road. One factor slowing that race is vehicle cost, so economically, the answer is a qualified "yes."

There are many uncertainties regarding what is economical. In the year 2001, there is no contest. The internal combustion vehicle is more economical than any alternative. The internal combustion engine revolutionized transportation and the economy, as the twentieth century evolved. By the start of the twenty-first century, there were more than 200 million vehicles on the road in the United States. Fueling their internal combustion engines has forced the country to rely on imported oil from the Middle East and to scramble for reserves with the uncertainty of supplies.

Within the next decade, the cost of fuel and the cost of protecting the environment may shift the balance. Environmental issues may be so compelling that health and safety concerns may force a change regardless of cost. There is also the pressing question of global warming and where the internal combustion vehicle emissions fit into the equation.

Although great improvements have been made in reducing emissions from internal combustion engines, the ever-increasing numbers of vehicles, the size/style of the vehicles, and the increasing number of miles driven have combined to negate any progress in emission control. After over 100 years of improvements, the technology of the internal combustion engine is reaching its limits for improvement. The United States Environmental Protection Agency (EPA) estimates that motor vehicles in the United States still account for 78% of all carbon-monoxide emissions, 45% of nitrogen-oxide emissions, and 37% of volatile organic compounds in the atmosphere.

Background for the Shift to Alternatives

How do the three types of electric vehicles that are in use—battery powered, fuel cell, and hybrid electric—compare? The technology for batteries is very different from the technology for fuel cells, although neither has any moving parts, which makes them both very quiet and reliable. Batteries store electricity, and when they run out, they have to be recharged. Battery-powered vehicles are limited for the most part to the local utility types because presently there is no battery that can go the distance that an internal combustion-powered vehicle can on a full tank of gas. Some battery-powered vehicles are recharged from photovoltaic cells in California, but most are recharged from the grid. They generally are not viewed as competitors to the internal combustion engine. Fuel cells do not store electricity but rather continuously produce electricity as long as the fuel is available. Fuel-cell technology is well developed. Fuel storage issues are the major focus of current research to give fuel-cell vehicles the performance the public expects of a vehicle. Hybrids are, in some views, the best of both worlds.

Most experts agree that fuel cells are the leading technology as an alternative to the internal combustion-powered vehicle. To maintain a leadership position in energy technologies, major oil companies are joining car and engine manufacturers in research and development to bring fuel-cell powered vehicles to market. Where hydrogen is the fuel of fuel cells, very probably there will have to be another choice at the pumps before the first decade of the twenty-first century plays out.

The fuel cell is not a new technology, having been first developed in 1839 when William Grove, a British physicist, discovered the principle of the fuel cell. It took over 120 years, however, before NASA (National Aeronautics and Space Administration) found an application for them in the 1960s when fuel cells were considered safer than nuclear power in space flight. Fuel cells were used in both the Gemini and Apollo missions and continue to be used in space ventures as a source of electricity and water.

With NASA's success, industry became interested, but early research and development efforts were not very encouraging and the technology appeared to be much too expensive. An increase in effort came when the Office of Transportation Technologies of the United States Department of Energy (DOE) started supporting research and development in 1984. In 1990, the United States Clean Air ActAmendments along with the National Energy Policy Act of 1992 gave impetus to the development of alternatives to the internal combustion engine for vehicles. The California Air Resources Board recognized in 1990 that it probably would not be possible to meet their first goal of zero emissions with gasoline-powered vehicles by 1998. That goal was unrealistic, so a new timetable was set up. Beginning in 2003, 10% of the new vehicles in California will be required to be zero (or nearly zero) emission vehicles. Similar regulations are now on the books in states on the East Coast.

The Technology of Fuel Cells

A fuel cell is an electrochemical device, that is it produces electricity by a chemical reaction. In the fuel cell, hydrogen gas and oxygen from the air are combined to produce electricity, and heat and water are byproducts. Because there is no combustion, fuel cells meet the zero emissions standard. A fuel cell is composed of two electrodes, an anode (positive electrode) and a cathode (negative electrode). The electrodes are separated by a porous medium that serves as an electrolyte. Fuel cells come in five varieties that are distinguished by the electrolyte employed.

The fuel cell that is leading the field for vehicle use is identified as a PEM fuel cell. PEM stands for proton exchange membrane, and also for polymer electrolyte membrane. The PEM is a thin film polymer membrane that is coated with a platinum catalyst. An electrolyte by definition is a substance that dissociates into positively and negatively charged ions in the presence of water. The membrane is moist, and though the membrane does not dissociate, it serves as an electrolyte in the sense that it allows positively charged particles—protons—to pass through it, thus the name proton exchange membrane. In the cell the membrane looks like a piece of thick plastic wrap.

In the fuel cell, hydrogen enters at the anode, where the catalyst on the membrane splits it into a proton and an electron. The proton passes through the membrane; the electron cannot. Instead, the electron moves out of the cell, through the external circuit. The electrons moving in the external circuit are the energy source that drives the vehicle.

On the cathode side of the catalyst-coated membrane, the proton meets oxygen (from the air) and an electron (from the external circuit) on the cathode. As it combines with the oxygen, water is formed. Although this is a heat-producing reaction, and in many cases these reactions are easy to start, this reaction would not happen without the catalyst.

One single cell produces about 0.7 volts. The cells are stacked in series so their voltages add up. PEM stacks were used on the Gemini spacecraft, although the early version was not as efficient as present fuel cells, since the former made extensive use of platinum, an expensive element. Researchers at Los Alamos eventually found a way to reduce the platinum by 90%. Additional research at a Canadian-based company, Ballard, further advanced the technology, and the company has about 400 patents on fuel-cell improvements. Ballard's PEM stack has reached well over the power density needed for today's vehicles. International Fuel Cells (IFC), a United Technologies Company (best known for its jet engines), also has made advances in the technology, including reducing size, weight, and cost—important to bring economic viability to

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fuel cells. However, there is still work to be done on streamlining the design and manufacturing processes to produce cheaper cells. Mass production of fuel cells will also bring down the cost.

Some see the key issue in the move toward fuel cells as the fuel itself, now that most of the research and development on the cells is concentrating on fine-tuning to improve the economy of production. Where will the hydrogen come from? All the major car manufacturers are working toward sending a fuel-cell powered vehicle to market in numbers. The oil companies are working with them to develop fuel sources.

There are also technologies related to fuel storage that need to be addressed. Where hydrogen is the fuel, the problems arise of how to safely store enough hydrogen, or how to produce enough hydrogen on board, to give the fuel-cell powered vehicle the same distance a user can get on a fill-up of gasoline with an internal combustion engine. Economic viability is in danger if the fuel-cell driven vehicle cannot provide the same convenience as its internal combustion-driven competitor. Storage of compressed gas on board is being considered. Liquefied gas is also being investigated but that involves very cold temperatures for storage. Cryogenic technologies are involved that may be too costly. There is also the fear of hydrogen stemming from the infamous Hindenburg disaster of 1937, when the hydrogen-gas powered airship exploded mid-air, killing thirty-six people.

Allowing that the storage on board problems are solved, oil companies are looking at producing hydrogen to be pumped into a vehicle's storage system. Texaco has over 150 patents on a technology they call gasification that uses otherwise undesirable heavy oil, petroleum coke, and wastes and converts them into hydrogen. The company could market hydrogen at a pump with this system.

Another approach is to store a source of hydrogen in the vehicle. One of the dominant technologies to produce hydrogen on board is the fuel processor, a mechanical device that uses heat and a catalyst to change the chemical composition of a hydrocarbon to free the hydrogen in a system integrated with the fuel cell in the vehicle. IFC has a prototype ready. The hydro-carbon could be methanol, methane from natural gas or other sources, or even gasoline that is stored in the vehicle.

The Technology of Hybrid Electric Systems

The hybrid electric vehicle runs on batteries that are recharged as the vehicle drives. This eliminates the down time at the recharge station for battery electric vehicles and makes the vehicle as useful as any internal combustion-driven counterpart. There are a number of systems employed to recharge the batteries. One that stands out is the microturbine, which meets California's tough emission standards. Capstone, a California company, has a microturbine that was put on a Chattanooga, Tennessee, bus in 1997 as an on-board battery charger, and it logged more than 30,000 miles with no breakdowns. The bus generates less than 1/25th the emissions of a diesel bus. Microturbines are now being used in cities as far away as Christchurch, New Zealand, and Tokyo, Japan. A microturbine is lighter in weight than an equivalent diesel engine. In Christchurch, diesels were replaced with micro-turbines in hybrid electric buses. A microturbine has only one moving part and is very environmentally friendly. The Capstone microturbine can run on just about any liquid fuel from natural gas to landfill methane to diesel.

In Los Angeles, ISER, a bus manufacturer, has a turbine-hybrid drive system that employs lead-acid batteries with Capstone microturbines recharging them. An onboard computer network continuously monitors vehicle power and battery charge levels, and adjusts the turbine power output to provide just the right amount of power to operate the vehicle. When the generators are not needed, they are automatically turned off and the bus runs on battery power. At that time the bus is a zero emissions electric vehicle. The batteries provide surge power for acceleration and recapture energy during braking. The microturbine is fueled with propane.

Presently all the major auto manufacturers are producing hybrid electric test vehicles under the DOE Office of Transportation Technologies Hybrid Electric Vehicle Program. One of the recent models is a Dodge Durango Hybrid sports utility vehicle. Federal legislation to create up to $3,000 in tax incentives for purchasers of hybrid vehicles could make them competitive with internal combustion engines. The down side is that many of them are still using petroleum-based fuels. The good news is that fuel cell and hybrid electric vehicle technologies have moved out of the skunk works and are now on the market to provide a technologically viable alternative to the internal combustion engine vehicle. Within a decade these alternatives might even be economically viable.

—M. C. NAGEL

Viewpoint: No, current internal combustion engine technology has many advantages over its potential competitors—lower costs of production and operation, a longer driving range before refueling, and better overall performance—that will ensure its dominance for several decades to come.

Although concerns over the environment and fuel supplies have fostered an abundance of research to find alternatives to powering cars and other vehicles, each new prototype of the "engine-of-the-future" has demonstrated that replacing the efficient and dependable internal combustion engine will be a difficult task. Many informed observers, including officials within the Energy Information Administration at the United States Department of Energy, predict that several decades will pass before any of the new technologies under development—including electric, fuel cell, and hybrid technology—will begin to have an impact on the market supremacy of the internal combustion engine. This versatile engine design, which currently powers more than 200 million vehicles in the United States, has been the backbone of the transportation industry for more than a century and for good reason.

From the very beginning the internal combustion engine has had competitors. For example, the first electric-powered car dates back to the 1860s, and in 1899, an electric car set the world record for speed by going faster than 62 miles per hour. But the internal combustion engine became the technology of choice because of its dependability and convenience.

Over the years, research has continued to improve the internal combustion engine, and it has yet to reach its full potential, including its potential for fuel efficiency and producing cleaner emissions that are less harmful to the environment. During the 1990s, the internal combustion engine was improved significantly in terms of its environmental impact. Increased miles per gallon of gas, for example, has resulted in better fuel efficiency and less pollution. Lower polluting emissions have also resulted from improvements in gasoline, such as the addition of oxygenates, which has lowered carbon-monoxide emissions by 18%. Furthermore, additional improvements such as progressively reducing the use of sulfur in gasoline will further reduce polluting emissions created by the internal combustion engine.

Overall, because of technologies such as the advanced catalytic converter and electronic combustion control, automobile emissions already are lower by 95% compared to the 1960s, despite the fact that many more cars are on the road today. In addition, most of the cars produced in the United States in 2001 and beyond emit 99% less hydrocarbons than cars made in the 1960s. Even if no further improvements were made in the internal combustion engine, its impact on the environment would continue to decrease solely due to newer cars with far lower emissions replacing older cars as they wear out and are sent to the scrap heap.

With a vast amount of experience in designing internal combustion engines and huge facilities for producing them, vehicle manufacturers are also not about to relegate these engines to obscurity in the near future. Most important, however, current internal combustion engine technology has many advantages over its potential competitors—advantages that the consumer demands. These include lower costs of production and operation, which results in lower costs for the consumer; a longer driving range before refueling; and better overall performance.

The Internal Combustion Engine versus the Electric Car

At the beginning of the twentieth century, more than 100 electric car manufacturers in the United States were vying to produce the vehicle of choice in this then young but rapidly developing industry. In less than two decades, nearly all of them had closed up shop. Many of the factors that led to the demise of the electric vehicle, including the large disparity in cost and convenience, still remain valid reasons why such vehicles are unlikely to replace the internal combustion engine in the next decade.

Despite a decade or more of intensive research and testing, electric cars are only able to travel approximately 100 miles (160.9 km) before they need to be recharged. Furthermore, this recharging takes a considerable amount of time compared to the relatively quick refueling that takes place at the local gas station. In comparison, a standard internal combustion engine can take a vehicle about 345 miles (155.2 km) before refueling is required. Electric cars can also only match the internal combustion engine in terms of horsepower for a short period of time (approximately one hour) before their power starts to diminish due to such factors as speed and cold weather. The electric motor's shorter range and slower overall speed might have been acceptable early in the twentieth century when families and businesses usually were condensed into smaller geographic regions. However, in today's society people routinely travel much farther distances, and a consumer public that places a high premium on its "time" has not shown a propensity to accept electric cars that are slower and require more stops and recharging.

In a society that is growing more and more environmentally conscientious, a much touted advantage of electric cars is that they are much cleaner in terms of environmental impact than cars run by internal combustion engines. Although electric cars produce nearly zero emissions from the car itself (perhaps as much as 97% cleaner than an internal combustion engine), this advantage is greatly negated by how electric engines are charged. For example, fossil fuels such as coal and oil are often used to generate electricity, which also produces its own pollutants. Even some noted environmentalists have conceded that this fact offsets any of the environmental advantages electric cars have over the internal combustion engine. Gasoline is now also lead free, but battery wastes still pose significant environmental problems, including the disposal of lead and cadmium.

The Internal Combustion Engine versus Fuel Cells

Another technology proposed as the wave of the future are fuel cells, with most of the focus on hydrogen fuel cells. A fuel cell is an electrochemical device that uses hydrogen and oxygen gases to produce electricity. However, like the electric car, fuel-cell cars would have a limited range in comparison to the internal combustion engine-driven cars, probably around 200 miles (321.8 km) or so. Although this range will increase with improvements such as reducing the weight of the car, reduced car weight would also improve mileage in cars powered by the internal combustion engine. Comparably, the fuel cell still would only achieve one-third of the range achieved with an internal combustion engine. In addition, there is the issue of producing the energy stored in the fuel cells. This energy would be created by fossil fuels or the generation of electricity to isolate hydrogen from the air, issues that, like the electric car, would result in environmental pollutants. Hydrogen is also volatile and an extremely small molecule that can filter through the smallest of holes, which increases safety concerns over leaks and pressurized tanks that could burst.

Fuel cells are also extremely expensive to manufacture. The cost of $500,000 per kilowatt of power associated with the first fuel cells used to provide power to space capsules in the early 1960s has been lowered to approximately $500. Nevertheless, a fuel-cell engine and drive train costs as much as 10 times the cost of producing an internal combustion engine. As a result, on average the cost of fuel-cell technology is approximately $25,000 to $30,000 (and perhaps as much as $45,000 to $65,000) compared to the average $2,500 to $3,000 cost for the standard internal combustion engine in many cars. Few consumers are going to readily accept this significant added expense.

Another factor to consider is the local gas station, which represents an already existing nationwide infrastructure for providing fuel to motorists. No such infrastructure exists for fuel-cell vehicles. While the current infrastructure could be adapted to accommodate fuel cells that use on-board reformers to isolate hydrogen from gasoline, diesel, or methanol, the on-board technology would further increase already higher costs. In addition, it would take up even more space than the large tank currently needed for fuel cells to provide adequate driving distances. Fuel-cell technology also still requires fossil fuels just like the internal combustion engine. It would also likely take more than a decade for energy companies to create the number of new or overhauled manufacturing facilities needed to produce enough hydrogen to meet consumer demands. Furthermore, some estimates indicate that only 2% of stations would be able to offer fuel-cell car refueling by the year 2011 and only 3.5% by the year 2020.

The Internal Combustion Engine versus the Hybrid

In a sense, the hybrid electric car is a concession that the internal combustion engine will be around for many years to come. Like the electric car, the concept of the internal combustion engine-electric hybrid goes back to the early days of automobiles, with the first United States patent filed in 1905. However, they were never developed as fully as the electric car. In essence, the hybrid uses a battery-powered electric motor for riding around town but also has an internal combustion engine that could be used for traveling longer distances and, in some models, to help recharge the battery-powered electric motor.

Although this alternative to the internal combustion engine as the primary source of power seems attractive, the drawbacks of the current technology used in this approach are substantial. For example, an internal combustion engine combined with the need for many batteries and a large electric motor to power the car requires extra space and more weight, which decreases the vehicle's overall fuel efficiency. Both the National Academy of Sciences and the National Academy of Engineering have stated that this technology is not cost-effective in terms of being environmentally friendly, especially since the use of gasoline or diesel reduces the environmental benefits that are essential to any new motor technology. Hybrids would also cost approximately $10,000 to $15,000 more than current car technology.

No Imminent Alternatives

Several reports and studies have stated that current technology will not provide a viable alternative to the internal combustion engine within the next decade and, perhaps, not for many more years following. In its June 2000 policy study The Increasing Sustainability of Cars, Trucks, and the Internal Combustion Engine, the Heartland Institute predicted that "it will be 30 years before even a modest 10% of all cars and trucks on the nation's roads are powered by something other than internal combustion engines."

While the technology does exists to make alternatives to the internal combustion engine, it has yet to advance to a level that makes it competitive or viable in terms of consumer needs and wants. For example, although some electric vehicles have been marketed aggressively in places like California, they still make up only a small percentage of the market. And companies such as Honda and General Motors have quit producing them. Even in Europe and Japan, where gas costs two to three times more than in the United States and where significant government and manufacturing subsidies are in place to support consumers in buying electric vehicles, they make up only about 1% of the market.

With the increasing popularity of sports utility vehicles (SUVs) in the Unites States throughout the 1990s, consumers obviously have shown their attraction to vehicles with more horsepower and greater size. To date, alternatives to the internal combustion engine have resulted in smaller cars with less power and less passenger and luggage room. Furthermore, to make up for the technology's additional weight and to increase driving distances before refueling or recharging, these cars are integrating more lightweight materials in their construction. The result are cars that are less safe in the case of accidents, another fact that consumers are not likely to ignore.

Even if the internal combustion engine were never improved upon, it is not likely that alternative technologies can overcome factors such as size, safety, cost, convenience, and power within the next decade. But the race is not against a technology that is standing still. While new technologies will continue to improve, car manufacturers also continue to invest billions in improving the internal combustion engine. Although currently cost-prohibitive, a standard internal combustion engine may one day get 80 miles per gallon and be able to travel 545 miles before refueling. Furthermore, advances in other technologies, such as computerized explorations for gas and horizontal drillings, are increasing the long-term production outputs of oil and gas fields in the United States and other western countries, thus increasing the prospect of a continuous, long-term, and relatively inexpensive supply of fuel.

To become a "viable" alternative to the internal combustion engine, alternative technologies must be as efficient, dependable, and powerful. Furthermore, they must be as competitive in terms of cost to the consumer. To reach these goals within a decade is not possible given the internal combustion engine's current vast superiority in these areas.

—DAVID PETECHUK

KEY TERMS

ELECTROCHEMICAL CELL:

Where electric energy is produced by a chemical process. Electrons leave the cell at the anode and return to the cell at the cathode. Any device to be run by the cell is attached between the anode and the cathode.

EMISSIONS:

Substances discharged into the air.

FOSSIL FUELS:

Fuels that are formed in the earth from plant or animal remains. Fossil fuels include coal, oil, and natural gas.

HORSEPOWER:

A unit of power equal to 746 watts.

HYDROCARBONS:

Organic compounds containing only carbon and hydrogen; often occur in petroleum, natural gas, and coal.

HYDROGEN:

The simplest and lightest of the elements; usually colorless and odorless; highly flammable.

INFRASTRUCTURE:

The resources (including personnel, buildings, or equipment) required for an activity.

MEMBRANE:

A semi permeable surface or thin film.Charged particles and small molecules selectively pass through the membrane separating them from a mixture.

POLYMER:

Commonly called plastic. The term literally means many parts. A polymer is produced by many molecules of one or more types repeatedly joining together. The smaller units are called monomers.

SKUNK WORKS:

A laboratory where research and development is done usually on proprietary projects or behind-the-scenes.

FUEL CELLS IN SPACE

NASA (National Aeronautics and Space Administration) started publishing reports of SPINOFFS annually in the 1970s. The reports feature industry/government collaborations on breakthrough technologies that are being developed as a result of the space program. Had NASA been writing such reports in the 1960s, fuel cell technologies would have been high on the list of early success stories. Fuel cells—cells that generate power through the interaction of oxygen and hydrogen gases—were first invented in the early nineteenth century but not widely used until the early years of the space program. Fuel cells are still being featured in SPINOFF reports; in 1999, for instance, the development of a next-generation PEM fuel cell was featured.

After fuel cells provided on-board power for the Gemini and Apollo spacecraft, industry became interested. Today, three fuel cell power plants provide the 28-volt direct current needed for the space shuttle. The fuel cell system generates all the electrical power for the vehicle during all mission phases. Cryogenic hydrogen and oxygen are used for the cells. In addition, cryogenic oxygen is supplied to the environmental control and life support system for crew cabin pressurization. The storage temperature for the liquid oxygen is minus 285°F (minus 176°C), and minus 420°F (minus 251°C) for liquid hydrogen.

In addition to providing all the on-board electrical power (there is no backup battery), fuel cells also produce water as a byproduct of the electrochemical reaction. This water is then used as drinking water for the crew as well as for spacecraft cooling. The fuel cells are alkaline fuel cell (AFC) power plants that each contain 96 individual cells. The electrolyte, a solution of potassium hydroxide, gives the fuel cell its name. AFCs have the advantage of a fast reaction and high performance, so they are popular for military and space applications. However, AFCs are also costly. The anode catalyst contains platinum and palladium, and the cathode catalyst contains gold and platinum. The cost factor is no doubt part of the reason for continuing research on fuel cells.

—M. C. Nagel

Science in Dispute