Hydrogen Fuel Cells - The Fuel of the Future

By: Will Jobs

Hello, this is my research project on hydrogen fuel cells. Before I begin, however, let me introduce you to how I got this whole thing started. Well I had, for a long time, been interested in such revolutionary ideas as perpetual motion and other things that could change our world. And then came the science fair. At first I decided to research perpetual motion.....only that didn't turn out too well. Being as it is not possible due to a violation of the laws of both physics and thermodynamics, I decided instead to do a project on chaos theory, which was somewhat of a success, me getting 1st place. However, later in the year we had to do an English research report. And so, that is when my interest into hydrogen fuel cells grew. I quickly got much research into this area and compiled the report you will see below. All of my sources are listed as well as parenthetically cited, for further reading if you so choose. While doing my research I often hoped for a source that had every piece of information that I could possibly hope for, but I never found it. Well, I hope I can be the saving grace for some poor lost soul in English class now. I hope you enjoy it.

Before continuing, let me just get the legal stuff out of the way. If you would like to use this as a source, just e-mail me at jabber1052@aol.com and I'm sure I'll let you do it. The work was created, well finished anyway, on June 10th, 2004. This document is protected by law and plagiarism is taken seriously. So, without further adieu, my paper.

Hydrogen Fuel Cells - The Fuel of the Future

    Since the Industrial Revolution began, man has sought out the most efficient, cleanest, and in one word, perfect engine to run everything from large scale machines to hospitals. However, up until now, no solution had been found. One invention may change that. Hydrogen fuel cells, with hydrogen’s abundance, cleaner emissions, and greater efficiency than that of oil will be the solution to an eventually oil-barren world.

     To truly understand and appreciate the magnificence of the fuel cell’s power, one must look back into their history. Invented in 1839 by Sir William Grove, Grove used porous platinum electrodes and sulfuric acid as the electrolyte, also later using this device to be the first to successfully split water in the process of electrolysis in the same year (“Frequently Asked Questions” 2). Next came William White Jacques, who substituted phosphoric acid as the electrolyte and was the first to coin the term “fuel cell” (2). Further research was done in Germany in the 1920s who developed the carbonate cycle and the solid oxide fuel cell (2). Later, as there was no practical use for these inventions at the time of their creation, General Electric made the first proton exchange membrane (PEM) fuel cells for power supplies in the Apollo and Gemini space missions, which were a success as they performed quite reliably, also making fresh drinkable water in space (Rifkin 3). During the 1960s, NASA used alkaline fuel cells for electricity in space (“Frequently Asked Questions” 2). As time passed, hydrogen fuel cells gained popularity and widespread support, being deemed a solution to pollution and other problems plaguing the modern world.

     One must therefore wonder, “Why use hydrogen fuel cells? Why not just modify the existing oil infrastructure to suit our needs?” Well, the answer to this question is quite complex. Currently, the dependence of the United States on the Middle East for oil is greater than that of the “oil shock” of the 1970s, and oil imports are expected to increase (“Fuel Cell Basics: Benefits” 1). In fact, as Jeremy Rifkin so eloquently put it, “... virtually ever aspect of modern existence is made from, powered with, or affected by fossil fuels” (Rifkin 5). Passenger vehicles use approximately 6,000,000 barrels of oil every single day, which amounts of about 85 percent of oil imports (“Fuel Cell Basics: Benefits” 1). If just twenty percent of cars were powered by fuel cells, oil imports would be cut by about 1,500,000 barrels of oil per day (1). The Energy Information Association estimates that about 10 million barrels of oil were used per day in the year 2000 – 155 billion gallons in 1998 (2). The world’s fuel use is so great that, in forty years or so, all of the cheap, recoverable crude oil in the world will be gone, and some experts claim that by the end of this decade global oil production may peak, leaving much of the oil remains in the Middle East and allowing prices to skyrocket (Rifkin 1). As tensions rise between Islam and the West, oil prices also rise, countries gain debt, and the United States loses its access to oil (1). Due to the weakness of American power grids, disruption by terrorists in terms of physical or computer attacks is quite likely, striking the heart of America ’s system (2). “Because they are efficient, modular and fuel flexible, fuel cells can enable a transition to a secure, renewable energy future, based on the use of hydrogen” (“Fuel Cell Basics: Benefits” 1). It is not only the economic stability that fuel cells provide that has made them such a possible prospect. The primary goal of fuel cells is to reduce pollution (Nice 4). Vehicles fueled with pure hydrogen create no pollution, emitting only water and heat (“Fuel Cell Basics: Benefits” 2). And since scientists have linked air pollution to heart disease, asthma, and cancer, polluted urban air is a serious problem as it is as dangerous as passive smoking (2). Fuel cell power plants make less than one ounce per 1000 kilowatt-hours of electricity produced, while conventional combustion generating systems produce a whopping 25 pounds of pollutants (2). In fact, fuel cell power plants are so low in emissions that they have been exempted from air permit requirements in many states (2). “Fuel cells can reduce pollution today and offer the promise of eliminating pollution tomorrow” (2). Fuel cell vehicles are more efficient than combustion systems because they make energy electrochemically and do not burn their fuel (1). Fuel cell passenger vehicles are up to three times more efficient than internal combustion engines, and when fueled by pure hydrogen, are fifty percent efficient, and even more efficient ones are under development (2). If used with a turbine, electrical efficiencies rise to over sixty percent and if the waste heat that is made is used for heating and cooling, the efficiency is well over 85 percent (2). This explains why so many companies are “jumping” at the chance to fund research and invest money into their development. The quality of power and reliability is so high that in six years only one minute of down time will be encountered and equipment that requires careful, controlled energy flow will run flawlessly (1). If not used for mainstream power, hydrogen fuel cells also see a quite lucrative future in terms of backup power, as they are already doing this in hospitals and such and can be completely independent of grid power (1). Also, hydrogen is the most abundant element (Rhey 4). Found chemically combined everywhere on Earth, it is seen in water, fossils, and all living things, but unfortunately it is rarely found free-floating in nature (Rifkin 2). Hydrogen can be delivered more cheaply than electricity, as well as more efficiently and has many more energy applications than electricity ever will (2). Fuel cells allow for more efficient vehicles as well as a transition to renewable energy use (“Fuel Cell Basics: Benefits” 2). As an author at Fuel Cells 2000 once wrote, “Fuel cells, in combination with solar or wind power, or any renewable source of electricity offer the promise of a totally zero-emission energy system that requires no fossil fuels and is not limited by variations in sunlight of wind flow. This hydrogen can supply energy for power needs and for transportation” (1). The future will be in decentralized, renewable energy, because as the oil market grows by 1.5% per year, the wind and photovoltaic markets double in size every three years (Rifkin 2). It is these qualities that allow hydrogen fuel cells to be “the fuel of the future”.

     Since hydrogen fuel cells are based on hydrogen, it is therefore imminent that one has sufficient knowledge of hydrogen to understand their inner workings. Hydrogen, when spilled, rises instead of remaining onsite for possible fires (Motavalli 59). Also, hydrogen is odorless and its flame, though invisible and while hydrogen is very flammable, it emits little radiant heat and will not hurt anyone unless they are actually touching the fire (59). Hydrogen cars do not burn their hydrogen, however an accident could create a spark which is one of the risks currently being studied (59). Hydrogen has the highest energy content per unit weight of any fuel – 52,000 Btu/lb (approximately 120.7 kJ/g) (“Frequently Asked Questions” 4). It also burns clean, and when burned with oxygen, its only byproducts are heat and water, while, when burned with air, it only forms oxides of nitrogen (4). The cost of hydrogen, when used at large-scale sites, such as factories, only costs $0.32 per pound (6). If the hydrogen is needed in liquid form and also required to be transported to the user, the cost rises to about $1.00 - $1.40 per pound (6). However, for pure hydrogen, people often have their own electrolyzers and this costs about one to two dollars per pound (6). When the cost and benefits of hydrogen use are all accounted for, hydrogen does not seem like such a bad thing. However, the main problem of hydrogen is fuel storage (Motavalli 117). Hydrogen tends to leak from any container that it is sealed in, and, because it is the smallest atom, it is quite difficult to contain. Hydrogen can be gotten from electricity from conventional, nuclear, and renewable sources, thus making hydrogen a very flexible fuel to use (“Fuel Cell Basics: Benefits” 1). 48 percent of hydrogen is made from natural gas, while thirty percent is from oil, 18 percent is from coal, and only four percent is from electrolysis (“Frequently Asked Questions” 7). Other sources of hydrogen include gas or methanol, however reforming these substances is expensive and produces carbon dioxide as does the gasification process used to extract hydrogen from coal (Rifkin 2). The process by which hydrogen is extracted from natural gas involves natural gas reacting with steam in a catalytic converter to strip away the hydrogen atoms, leaving carbon dioxide as the byproduct (2). Another benefit of hydrogen is that it can be made from landfill gas, “anaerobic digester gas” from wastewater treatment plants, biomass technologies, ammonia, borohydride, and even compounds with no carbon, thus ridding our atmosphere of any other harmful gases besides just the greenhouse gases (“Fuel Cell Basics: Benefits” 1). Such novel feed stocks will require much attention in the future and the hydrogen fuel cells may in this way prevent the buildup of greenhouse gases. However, with all of these methods aside, a very important process by which hydrogen is made is electrolysis. This process, which uses electric current to pull hydrogen from water, is quite convenient and one day electrolyzers may be seen at every fueling station across America (1). One may ask, “Why use electrolysis in the first place?” However, the answer to this is simple. Electricity can be stored only in batteries which are heavy and slow to recharge (Rifkin 3). However, hydrogen can be stored more cheaply (Rifkin 3). Electrolysis works by sending electric current through water to separate it (“Frequently Asked Questions” 5). Electricity enters the water at the negative cathode, passes through the water, and exists via the anode, i.e. the positive cathode, where oxygen collects and hydrogen collects at the cathode (5). Fortunately, the hydrogen produced from one gallon of water using an electrolyzer could drive a hydrogen fuel cell car as far as a gas vehicle could on one gallon of gas (5). In terms of energy requirements, if it is assumed that 1.23 volts is used, the energy required in electrolysis is 32.9 kilowatt-hours per kilogram of water (6). If the voltage is 1.75 volts, the voltage required in commercial electrolysis, the energy required is 46.8 kilowatt-hours per kilogram, which is a seventy percent efficiency (6). If the voltage is lowered, the energy efficiency is increased, and so scientists are currently doing research into this area (6). Some sources of energy for electrolysis include renewable sources, such as the sun, wind, water, geothermal, and biomass can be used to make electricity to do electrolysis to split water into hydrogen and oxygen and store the hydrogen in a fuel cell to make energy later with heat as the byproduct possibly being used to heat homes (Rifkin 3). In fact, wind, hydropower, and biomass (the process of burning plant material such as wood waste and agricultural residue) is already cost competitive in much of the world (3). Wind power is the fastest growing source of energy, costing only six to eight centers per kilowatt-hour, down from forty cents in the 1980s (3). Another pressing issue involving hydrogen is its safety. As Peter Yoyentzie of the Energy Research Corporation pointed out, “Hydrogen is a strange beast.... It’s the smallest molecule, and it leaks out of everything. You also can’t see it burn. In a car, it has to remain stable through collisions and constant agitation. That’s a lot to expect” (Motavalli 58-59). Hydrogen safety is a chief concern primarily because of one event in the 1930s. Back in 1937, the Hindenburg, a German zeppelin, caught fire, killing 37 and giving hydrogen a bad name in the process (57). However, this is not the full story. The Hindenburg was not hydrogen fueled, hydrogen was only used in place of helium it that was not available during the Nazi regime (58). Sixteen cells were filled with hydrogen which gave it lift, and this hydrogen only fueled the fire, it did by no means start it (58). When an electric discharge swept through the zeppelin from the docking station, it immediately ignited the highly flammable cellulose compound on the fabric covering and the aluminum powder coating which was used to reflect sunlight to prevent hydrogen expansion and is currently used in rocket fuel (58). This heat burst the hydrogen cells and ignited the escaping gas (58). In fact, 35 of the 37 who died on the Hindenburg died by jumping or falling and only two died from the burning coating and diesel while the hydrogen burned quickly, up and away from the people (“Frequently Asked Questions” 8). As Addison Bain, a hydrogen specialist and retired NASA engineer, put it, “I guess the moral of the story is, don’t paint your airship with rocket fuel” (Motavalli 58). As with all fuels, hydrogen does have some dangers, but is no more dangerous than gas, propane, or methane (“Frequently Asked Questions” 8). “Hydrogen is a lot safer to carry around than gasoline. If we had a hydrogen economy and someone proposed introducing gasoline, it would be prohibited as way too dangerous. I would for a darn sight rather be in a crash in a hydrogen car than in a gasoline car, from the fire and explosion perspective. Hydrogen is fifty-two times more buoyant, and thirteen times more diffusive than gasoline. Victims generally survive better in a hydrogen fire, because they’re not burned unless they’re in it” (Motavalli 59). Fifteen thousand cars are destroyed by engine fires every year and five hundred die from auto accident-related burns (59). “Like gasoline, hydrogen can be dangerous. And, also like gasoline, we can learn to use it as safely as possible” (60).

     Although several different forms of hydrogen fuel cells do exist, they all have the same basic components and operation. According to Karim Nice, “A fuel cell is an electrochemical energy conversion device that converts hydrogen and oxygen into water, producing electricity and heat in the process” (Nice 1). Fuel cells are classified by the type of electrolyte they use (1). Some may be for cars, some may be for power plants, and others for portable applications. The electrolyte, depending on the type of fuel cell it is, can be a polymer, phosphoric acid, molten carbonate, or some other kind of electrolyte (Motavalli 54). Basically, a fuel cell is an electrolyte sandwiched between two porous electrodes (the anode and the cathode) (“How Fuel Cells Work” 1). In a fuel cell, hydrogen or a hydrogen-rich fuel is fed to the anode where a catalyst separates hydrogen’s negative electrons from the positive ions (protons) (1). Then, at the cathode, oxygen combines with electrons and possibly water or protons to form hydroxide ions or water (1). The basic components of fuel cell systems are the fuel processor, the energy conversion device (fuel cell or fuel cell stack), the current converter, and the heat recovery system for stationary applications (4-5). Some other components may include systems to control fuel cell humidity, temperature, gas pressure, and waste water (5). The first component is the fuel processor. Its job is to convert fuel into a form useable by the fuel cell, and if the fuel is pure hydrogen, this is not required, or may be used to filter out any impurities (5). The energy conversion device, also known as the fuel cell stack, makes electricity in DC form from chemical reactions (6). The current converter/inverter takes the fuel cell’s DC power and converts it into a form used commonly, AC, or alternating current, while DC stands for direct current (6). This power must then be conditioned to control the flow, voltage, frequency, and other characteristics, reducing system efficiency by two to six percent (6-7). The heat recovery system, used in stationary applications with fuel cells such as SOFCs and MCFCs, uses the excess heat produced to make steam or hot water which can be converted to electricity with a gas turbine or other piece of equipment, and this increases the overall efficiency of the system (“How Fuel Cells Work” 7). In order to fully understand a hydrogen fuel cell, however, its parts must be more thoroughly examined. At the cathode, oxygen is forced through the catalyst, forming two oxygen atoms each with a negative charge, which attracts the two positive hydrogen ions through the membrane to combine with two electrons as well, forming water (Nice 3). At the anode, electrons are conducted from the hydrogen molecules and are used in the external circuit (2). Channels etched into the anode spread hydrogen gas evenly over the catalyst (2). The catalyst is the place at which electrons combine with hydrogen ions and oxygen to form water, and since it is a special material which aids the reaction of hydrogen and oxygen, usually it is made of platinum powder coated onto carbon paper of cloth and is rough and porous (2). Meanwhile, the electrons that have been freed from the hydrogen go to the cathode through a wire, making electric current since they cannot go through the electrolyte, and the intensity of this power is determined by the size of the electrodes (Motavalli 55). The power produced by a fuel cell depends on the type of fuel cell it is, and the size, temperature, and pressure at which gases are supplied to a cell (“How Fuel Cells Work” 2). A single cell is only strong enough for the smallest of applications and a typical stack contains hundreds of fuel cells (2). Each fuel cell makes 0.7 volts of energy (Nice 3). Also, to increase power, often pure hydrogen is used as a fuel. However, it is difficult to store much of this gas and the infrastructure to get hydrogen to customers is quite inefficient (“How Fuel Cells Work” 3). These “direct” hydrogen fuel cells make pure water released as vapor, and less vapor is made than internal combustion engines with the same power (2). Fuel cells can be fueled with methanol, natural gas, gas, or gasified coal, but they must be reformed (3-4). This allows for the use of higher energy density fuels and the use of conventional fuels as well, however, the reformer adds to the complexity, cost, and maintenance and they allow for carbon monoxide to reach the anode, which decreases the performance of the cell (3-4). The efficiency of fuel cells goes almost unmatched as well. A fuel cell powered with pure hydrogen has an eighty percent efficiency, meaning that it converts eighty percent of the energy of hydrogen into electrical energy (Nice 4). However, when a reformer to convert methanol of about 30-40 percent efficiency and an electric motor and inverter to convert electrical energy to mechanical work, the overall efficiency drops to about 24-32 percent (4). Compared with gasoline and battery engines however, this number is quite significant and may be what influences future buyers of these cars. Some examples of fuel cells include proton exchange membrane fuel cells (PEMFCs), alkaline fuel cells (AFCs), phosphoric acid fuel cells (PAFCs), solid oxide fuel cells (SOFCs), and molten carbonate fuel cells (MCFCs) (5). Hydrogen fuel cells, with a process as complicated as chemistry class, may be the solution to an oil-barren world.

     But with the use of hydrogen comes the question “Where shall this hydrogen come from?” Reformers are there to answer it. A reformer can take hydrogen from any hydrocarbon or alcohol fuel, such as natural gas, ethanol, methanol, propane, gas, and diesel (“Fuel Cells Basics: Benefits” 1). The first fuel cell cars may even run off a fossil fuel (Motavalli 56). Reformers also avoid the issue of hydrogen’s safety (57). With a reformer, forty percent of the fuel to electricity efficiency is maintained using hydrocarbon fuels (“Fuel Cell Basics: Benefits” 2). Reformers work by converting hydrocarbons into a gaseous mixture of hydrogen and carbon compounds called reformate (“How Fuel Cells Work” 5). This is then sent to another reactor which removes impurities such as carbon oxides or sulfur (5). Possible fuels for use with a reformer include natural gas, propane, and methanol (Nice 4). Gasoline will probably not be used because it contains sulfur which poisons fuel cells (Motavalli 56). In 1997, however, a joint project of Arthur D. Little Inc., Latham , New York ’s Plug Power, and the U.S. Department of Energy made a gasoline reformer (56). Bob Derby, the marketing director of Epyx, a small company which also was working on a gasoline reformer, said, “We envision a reformer that can work with multiple fuels and can be changed on the fly to use gasoline, ethanol, or methanol. You could compare the unit to a portable generator, except its efficiency levels will be much higher and its emissions levels much lower” (56). Indeed, this would be quite efficient as the requirements of a certain fuel would be much more lenient and the availability more prominent. Most fuel cells in transportation with a reformer use external reforming, having an external reformer to send this reformate into the fuel cell. In larger stationary fuel cells, which run at very high temperatures, the fuel can be reformed inside the cell itself, but “traps” are still required to catch any impurities (“How Fuel Cells Work” 5-6). Also, “... ‘reformed’ hydrogen is not pure, and isn’t likely to deliver the same performance as hydrogen gas” (Motavalli 57). It is crucial to remove impurities from this hydrogen gas because they bind with catalysts, thus reducing efficiency and the life expectancy of the cell (also called poisoning) (“How Fuel Cells Work” 5). Reformers would produce small emissions, but would reduce smog-forming pollution by ninety percent, and if the fuel is a fossil fuel, the carbon dioxide emission is cut in half (“Fuel Cell Basics: Benefits” 2-3). Also, reformers would allow modern society to maintain the current fuel infrastructure and it would be easier to store these fuels. Unfortunately, as with any possible solution, there are drawbacks. A reformer lowers the efficiency of the fuel cell because an extra step is required in the process (Nice 3-4). Also, even though reduced, pollution is still released, thus harming the environment (“How Fuel Cells Work” 6). Any carbon monoxide can reach the anode, as said before, and destroy it, and a reformer adds to the cost of the fuel cell. While reformers seem a possible solution to the problem of hydrogen leaks, it only postpones the need for research now.

     As time passes and more research is done, certain fuel cells are shown to be more designed for certain applications than others. In this way, the proton exchange membrane (PEM) fuel cell is the only type seriously being considered for use in cars (Motavalli 55). The reason for this is simply that the power density of PEMFCs is so high that something as big as a small piece of luggage can power a car (Nice 3). As Jim Motavalli, the author of Forward Drive put it, “The PEM cell... ... has no equal in terms of size, low operating temperatures, and adjustable power outputs, or quick starting” (Motavalli 55). They operate, as said previously, at a relatively low temperature compared with other fuel cells, allowing for their usage in cars. In a PEMFC, the electrolyte is the proton exchange membrane and is a solid polymer which only conducts positively charged ions and blocks electrons (Nice 2). Ordinary air is pumped to the cathode providing a source of oxygen (3). The electrodes of a PEM fuel cell are porous carbon electrodes (“Types of Fuel Cells” 2). The PEMFC also requires a noble-metal catalyst, usually platinum, to separate hydrogen’s electrons and protons (2). This is very sensitive to carbon monoxide poisoning and needs an additional reactor to reduce the carbon monoxide in the fuel gas, thus adding to the cost, however developers are currently researching platinum and ruthenium catalysts that are resistant to carbon monoxide (2). In order for this device to work, protons must move through the electrolyte to the cathode to combine with oxygen and the electrons, making water and heat (“How Fuel Cells Work” 1). In a PEM fuel cell, the anode has the reaction 2H2 à 4H+ + 4e-, the cathode has the equation O2 + 4H+ + 4e- à 2H2O, and the net reaction is 2H2 + O2 à 2H2O (Nice 3). Essentially, what this means is that overall hydrogen and oxygen make water. PEM fuel cells have a high power density, a low weight, require only hydrogen, oxygen form the air, and water, and do not need corrosive fluids (“Types of Fuel Cells” 1-2). Also, they have low temperatures (176 degrees Fahrenheit, 80 degrees Celsius), a quicker warm-up time, great durability, and no expensive containment structures are required (Nice 3).Unfortunately, the barrier with these fuel cells is hydrogen storage (“Types of Fuel Cells” 3). Hydrogen has a low energy density and is difficult to store enough onboard to go the same distance as gas-powered cars before refueling (3). The applications of PEMFCs are mainly in terms of transportation, rarely are they used in stationary applications (2). PEMFCs are most likely the fuel cell to be seen in future cars because of their size and low temperatures. They are a fuel of the future.

     Another type of fuel cell, the phosphoric acid fuel cell (PAFC), has the potential for small stationary power generation, with a higher temperature than PEMFCs, and a longer warm-up time (Nice 5). This makes them unsuitable for cars. Again, in this kind of fuel cell, the protons move through the electrolyte to the cathode to combine with oxygen and the electrons, making water and heat (“How Fuel Cells Work” 1). The electrolyte of a PAFC is phosphoric acid contained in a Teflon-bonded silicon carbide matrix, while the electrodes are again porous carbon electrodes, and the catalyst is usually platinum (“Types of Fuel Cells” 3). Phosphoric acid fuel cells have an 85 percent efficiency with the co-generation of heat and electricity, and a 37-42 percent efficiency when generating energy independently, which is slightly more than the 33-35 percent efficiency of combustion power plants (4). A benefit of PAFCs is that they are more tolerant of impurities in reformate than PEMFCs are, which are easily poisoned by carbon monoxide (4). Unfortunately they are less powerful than other fuel cells, are usually large and heavy, and are very expensive, usually costing between $4000 and $4500 per kilowatt hour to operate (4). PAFCs are considered the “first generation” of modern fuel cells, as they were first used commercially and are the most mature, with over 200 units in use (4). Often used in stationary power, they are also sometimes used in large vehicles such as city buses (4).

     Direct methanol fuel cells, another type of fuel cell, are a relatively new type of fuel cell powered by pure methanol mixed with steam which is fed directly to the fuel cell anode (4-5). The advantages of this are that there are less fuel storage problems since methanol has a higher energy density than hydrogen, and it is therefore easier to transport and supply to the public using the current infrastructure (5). Unfortunately, since a reformer would be required for this type of fuel, pollution is abound, as is the high cost of a reformer and the possibilities of anode poisoning.

     Since the U.S. space program alkaline fuel cells have been used to power rockets (Nice 5). They are one of the oldest fuel cells, first being used in the space program for electrical energy and fresh drinking water onboard the space ships (“Types of Fuel Cells” 5). Running at somewhat high temperatures (100-250 degrees Celsius, approximately 212 to 482 degrees Fahrenheit) with newer ones running at somewhat lower temperatures, they have a high performance due to the rate of chemical reactions and are very efficient, with efficiencies up to sixty percent in space applications (5-6).The electrolyte of AFCs (alkaline fuel cells) is a solution of potassium hydroxide in water, and the catalyst, anode and cathode are all made of non-precious metals due to the high temperature required (5). Negative ions go through the electrolyte to the anode where they combine with hydrogen and make water and electrons (“How Fuel Cells Work” 2). Unfortunately, being the oldest, these cells have the most disadvantages. They are very expensive (however this is not important in space and undersea operations by the government), and they need a longer run time, as currently they only run about 8000 hours, while its competitors run over 40,000 hours (“Types of Fuel Cells” 6). In addition they are quite susceptible to contamination and require pure hydrogen and oxygen (Nice 5). In fact, they are so easily poisoned that even the carbon dioxide in the air can affect it, and thusly, the lifetime of the cell is low (“Types of Fuel Cells” 6). Alkaline fuel cells provide a moderately temperatured, very efficient however non-durable means of running stationary applications.

     The molten carbonate fuel cell (MCFC) is especially suited for large stationary power generators (Nice 5). Running at exceptionally high temperatures (1112 degrees Fahrenheit, 600 degrees Celsius), they can use the steam for higher efficiency (5). This high temperature fuel cell has a molten carbonate salt mixture suds in a porous, chemically inert ceramic lithium aluminum oxide (LiAlO2) matrix for the electrolyte (“Types of Fuel Cells” 7). The electrodes and the catalysts can run with non-precious metals as they are generally the only ones which can stand such high temperatures (7). Their high efficiency qualifies them for cost reductions over PAFCs, with their efficiency being about sixty percent, much higher than the 37-42 percent of PAFCs, and when waste heat is captured and used the efficiency is almost 85 percent (7). In this type of fuel cell, the negative ions go through the electrolyte to the anode where they combine with hydrogen and make water and electrons (“How Fuel Cells Work” 2). Fortunately, MCFCs do not require an external reformer because their high temperatures can convert the fuels to hydrogen while inside the cell by internal reforming, thus reducing the cost (“Types of Fuel Cells” 7). Also, poisoning by carbon monoxide or dioxide is not likely and carbon monoxide can even be used as a fuel and it is resistant to other impurities as well (7). The primary disadvantage of MCFCs, however, is their durability because high temperatures and the corrosive electrolyte accelerate component breakdown and corrosion (8). This increases the cost of this type of fuel cell, even though previously efficiency had set that price lower. The applications of this kind of fuel cell are vast, being used currently for natural gas and coal-based power plants for electricity, and they also have industrial, military, and stationary applications (7). This kind of efficiency can only be found in molten carbonate fuel cells.

     Stationary power applications are few and so in order for fuel cells to take over the fueling industry, they must first have possible candidates to replace combustion power plants. Among these is the solid oxide fuel cell. Used in large-scale stationary power generators for electricity for factories and towns, they run at very high temperatures (1832 degrees Fahrenheit, 1000 degrees Celsius) (Nice 5). Although their reliability is a problem, the steam produced can be channeled to turbines to make more electricity and thus have a higher efficiency (5). The electrolyte of an SOFC is a hard, non-porous ceramic compound, meaning that the cells do not need to be constructed in a plate-like configuration (“Types of Fuel Cells” 8). As with other high temperature fuel cells, non-precious metals are used for the electrodes and the catalyst (8). In solid oxide fuel cells, as with alkaline and molten carbonate fuel cells, the negative ions go through the electrolyte to the anode where they combine with hydrogen and make water and electrons (“How Fuel Cells Work” 2). No external reformer is needed due to the high temperature as well, reducing the cost of the fuel cell (“Types of Fuel Cells” 9). SOFCs have a fifty to sixty percent efficiency to convert the fuel to electricity and, with cogeneration the efficiency rises to 80-85 percent (8). The advantage of SOFCs is that they are very tolerant of different kinds of fuels. “SOFCs are also the most sulfur-resistant fuel cell type; they can tolerate several orders of magnitude more sulfur than other cell types. In addition, they are not poisoned by carbon monoxide (CO) which can be used as a fuel. This allows SOFCs to use gases made from coal” (9). The main disadvantages of solid oxide fuel cells are caused by the high temperatures. They have a slow startup, require thermal shielding to retain the heat and protect personnel, the durability requirements of materials is high, they need very strong and exotic materials which cost much, and lower temperature SOFCs have less durability issues but make less power as well (9). Solid oxide fuel cells have many of the same applications as molten carbonate fuel cells, being able to be used for stationary applications as well as industrial and military purposes. Although it runs at higher temperatures than molten carbonate fuel cells, it still has about the same efficiency and thus it will probably be molten carbonate fuel cells which see more of a future.

     Regenerative (reversible) fuel cells are a recently invented type of fuel cell currently being researched by NASA. These cells produce electricity like normal fuel cells, but they also use electricity from solar power or another source to divide the excess water into oxygen and hydrogen fuel by electrolysis. Thus these cells are also called reversible fuel cells and are efficient.

     Fuel cells undoubtedly have a number of applications, and those that are known today are not even the beginning of the wide spectrum of ideas and things to which fuel cells can apply. In passenger cars, PEMFCs will probably reign king, with their high power density and small size, low temperature, quick starts, responsiveness, etc. (“Frequently Asked Questions” 3). PAFCs will be used in buses and long-haul trucks while direct methanol fuel cells are possible for cars (3). Fuel cells may also serve as side power units, such as APUs (auxiliary power units) in long-haul trucks which would reduce emissions by 45 percent, have less wear and tear on the vehicle and would result in lower fuel use (“Fuel Cell Basics: Benefits” 3). APUs in Class 8 trucks save 670 million gallons of diesel fuel per year and 4.64 million tons of carbon dioxide per year (3). They hybrid car will combine internal combustion engines with strong nickel hydride batteries which recharge by the kinetic energy when the car brakes, and this may lead people into buying fuel cell cars (Rhey 2). Honda already has the first EPA-approved fuel cell car, the Honda FCX, and Ford invested 420 million dollars, partnering with Daimler-Chrysler and a Canadian fuel cell company, Ballard Power Systems, to create a commercial hydrogen-powered car (2). Another application, stationary uses, involves such things as power plants, hospitals, factories, and regular buildings to provide energy for. “... I think the building market comes first, then you get the prices down and put fuel cells in cars” (Motavalli 179). So as seen in this quote, research and development in one area of fuel cells will invariably affect others. Buildings make up two-thirds of the electricity in the United States , and so they would provide a large market for fuel cells (179). If fuel cells were manufactured instead of hand-assembled by Ph.D’s, the cost would come down from three thousand dollars per kilowatt to about eight hundred dollars, and if the waste heat generated was used to provide heating, cooling, and dehumidification, the efficiencies of these machines would rise from fifty percent to about ninety percent (178-179). The net cost of a building with a hydrogen fuel cell will be about one to two cents per kilowatt hour compared to the current cost of about six cents to the hour (179). This is a dramatic difference in price, and once the savings of hydrogen fuel cells are realized, more and more buildings may opt to use them as their sole source of power. Also, the military is another place where fuel cells will be making important changes. Seventy percent of the weight to get the US army into battle is fuel, and if fuel cells were used, they would give power for special operations, in remote areas, backup power, and would reduce energy use by twenty percent at federal facilities (“Fuel Cell Basics: Benefits” 4). As said in an article from Fuel Cells 2000, “Fuel cells may provide life-saving power for the soldier of the future, who will be carrying enough electronic equipment to require one kilowatt or more of electronic power” (4). If fuel cell production could be made more practical, not only the military, but almost every organization would be seeking them for their own. Another important category of applications of fuel cells is developing countries. The hydrogen economy will give developing countries access to clean, sustainable, economical hydrogen-based energy systems for growing energy demands as well as being a source of clean drinking water (“Frequently Asked Questions” 4). In nations without electricity currently, if they moved right to hydrogen fuel cells they would be one step ahead of everyone else and could become a world power. Hydrogen fuel cells could make electricity more efficiently than power plants today, and electricity will be gotten from a reaction and the heat and water produced can turn turbines to generate more electricity (Nice 6). Fuel cells are already used as backup power to hospitals and factories as well (Nice 6). One of the most important categories of application of fuel cells, however, is portable power. Many companies are investing money and resources into this area and thus it has become a “hot” topic. Fuel cells in portable applications would have a longer life than batteries and would not need to be recharged, they would only need to be refueled, and since they have a higher power density, they would be smaller (“Fuel Cell Basics: Benefits” 3). Also, they would provide access to electricity where an electric grid is not available (3). Neah Power Systems made a silicon honeycomb design for the electrode of its direct methanol fuel cell, increasing the power density with a smaller size and it can power a notebook laptop for up to eight hours (Rhey 2). Toshiba made a prototype of a direct methanol fuel cell to power a notebook for five hours, and its products, oxygen and water, were recycled back into the cell (2). Another company, NEC, is almost done building a fuel cell based on carbon nanotubes small enough to power a cell phone or handhelds (2). As Jim Motavalli put it, “... the fuel cell is just an enclosed box, with no spinning parts and no noise. It’s not much to look at, but its implications are vast, not only for transportation but also for the entire energy constellation, since fuel cells work even better in stationary applications – such as home power generation – than they do in cars” (Motavalli 55). The plethora of applications to which a fuel cell applies is so mind-bogglingly large that no one can conceive of it; the ideas around now are only the beginning, there will be more.

     Before the hydrogen fuel cell really plays a major role in our economy, however, it must beat out its competitors in terms of driving range, cost, efficiency, etc. The fuel cell’s main competitors are the gas turbine, the gasoline engine, the battery, diesel, and many others (Nice 1). Combustion engines work by burning their fuels and using the pressure created from the expansion of the gases to do mechanical work (1). Batteries store energy by converting it into chemical energy and then going back to electrical energy when needed (1). The efficiency of the gas engine, as all of the heat that comes out as exhaust is wasted, is about twenty percent (4). Batteries have a more complex efficiency. In the beginning, a battery is about ninety percent efficient, but with the electric motor/inverter, it goes down to about 72 percent efficient (4-5). If the electricity was originally made at a combustion power plant, then only forty percent of the fuel was converted to electricity, and the process of charging has a conversion of AC power to DC power, with about ninety percent efficiency, making the overall efficiency 26 percent (4-5). If the electricity was originally generated by a hydroelectric plant, the efficiency is a whopping 65 percent (4-5). So the original maker of the electricity plays a large role in determining the efficiency of the fuel. Natural gas production is expected to peak between 2020 and 2030, right after the oil crisis, so natural gas is not necessarily a safe route to go for hydrogen or for a fuel (Rifkin 3). There are many differences between gas and fuel cell powered cars. First of all, FCVs (fuel cell vehicles) are propelled by an electric motor powered by electricity from fuel cells, not an internal combustion engine (“Frequently Asked Questions” 2-3). Also, fuel cells are more energy efficient, release less greenhouse gases, are quieter than, and have more power for electric accessories than gas powered engines (2-3). Gas engines have a farther driving range (300-400 miles), however, than fuel cell engines (250 miles) (2-3). There are also differences between fuel cells and battery powered engines. Both are propelled by an electric motor, however a battery has its electricity stored in a battery and must be recharged, while fuel cells use hydrogen or another fuel and must be refueled, and batteries can go farther before refueling because of battery designs (2). And as Chris Borroni-Bird put it, “There are three central automotive goals... ... efficiency, range, and emissions. Diesel has the efficiency and range, but there are emissions problems. Batteries have the emissions and the efficiency, but not the range. The fuel cell promises to have extremely low emissions, with excellent range and efficiency” (Motavalli 148). Fuel cells will one day out perform all other engines in their class.

     Fuel cells in all their glory do have their own unique challenges that prevent the modern world from immediately switching over to them. One of the main questions is where to get hydrogen fuel from: to get it pure or extracted from a fossil fuel (56). While both do have their own advantages, most likely the first fuel cells will extract their hydrogen from fossil fuels such as methanol due to the reliability of the existing infrastructure. Also, when buying a car, there are four main issues which should draw one’s attention to which engine they should buy: “Is it quick and easy to refuel?”, “How far can one travel in it before refueling?”, “Is it as fast as other cars on the road?”, and “What does it emit in terms of pollution?” (Nice 5). Cost is the greatest challenge and factor to be remembered. Many designs require expensive, precious metal catalysts or materials that can stand high temperatures (“Challenges” 1). The durability and dependability of the cell is also important, as high temperature fuel cells tend to break down, PEM fuel cells need effective water management systems, and catalyst poisoning ruins fuel cells (1). Also, hydrogen costs more to make than gas, and the methods that are cheaper create greenhouse gases (1). Currently, the system of delivering gas and other conventional fuels cannot be used for hydrogen and a new infrastructure would be needed for hydrogen delivery (1-2). Another pressing issue, storage, is important because hydrogen has a low energy density volume, making it difficult to store in a compact space, however high-pressure tanks and research into metal hydrides and carbon nanostructures is underway (2). Hydrogen has many safety risks and must be handled with care, meaning that consumers must be educated of hydrogen’s properties and risks (2). Finally, in order for hydrogen fuel cells to really take off, their technology must be embraced by consumers widely (2). Without this the benefits will never be realized. “Although the potential benefits of fuel cells are significant, many challenges, technical and otherwise, must be overcome before fuel cell vehicles will be a successful, competitive alternative for consumers” (1).

     Recently, President Bush designated 1.2 billion dollars for a hydrogen fuel cell initiative which may make fuel cell car costs compete with conventional gas-powered cars in this decade (Rhey 2). And, if that were not enough, Congress also approved the Hydrogen Fuel Cell Act of 2003 to call for the deployment of 100,000 hydrogen fuel cell vehicles by 2010 (2). This shows that the public and the government are both ready for a revolution of fuel cell cars. But before this can happen, changes must be made in everything from the infrastructure to education. First of all, with the addition of fuel cells to the system, a possible new hydrogen power grid could be created (Motavalli 179-180). The way this would work is that since cars are parked 96 percent of the time, commuters would go to work, plug into a hydrogen line coming out of their job’s building and their car would produce electricity which they could sell back to the grid during peak power demand (179-180). This means that a new system of distributed energy rather than centralized power will be needed as each customer would also be a producer with the company being merely a regulator in the scheme of things. “If successful, fuel cells could not only hasten a shift in our energy infrastructure but also power mobile computers all day on a single charge” (Rhey 1). Currently the entire grid is fully interactive with state-of-the-art technology which will allow an easier shift from centralized power (Rifkin 5). Also, “Once the customer, the end user, becomes the producer and supplier of energy, power companies around the world will be forced to redefine their role if they are to survive” (4). There are less than twelve hydrogen fueling stations in the U.S. and only a few fuel-cell cars which are million dollar prototypes, however Ohio has a 100 million dollar plan to open up to four more hydrogen fueling stations (7). Fortunately for the power plant companies, distributed energy will actually bring them in more profits, and the company General Electric already is offering the first fuel-cell generator system for the public, Plug Power, which uses a natural gas or propane reformer to produce up to seven kilowatts of power (Nice 6). As Jeremy Rifkin so modestly said, “The fossil-fuel era brought with it a highly centralized energy infrastructure, and an accompanying economic infrastructure, that favored the few over the many. Now, on the cusp of the Hydrogen Age, it is possible to imagine a decentralized energy infrastructure, enabling individuals, communities, and countries to claim their independence while accepting responsibility for their interdependence as well” (Rifkin 6). Even in Europe, Romano Prodi, the president of the European Commission, unveiled the EU’s $2 billion commitment to producing 22 percent of its electricity from renewable sources by 2010 (7-8). So indeed, “The hydrogen economy is a world fundamentally different than the world we know now. Picture it... Hydrogen is available to everyone, everywhere – from the corner fueling station to the large industrial facility on the outskirts of town” (“Frequently Asked Questions” 3-4).

     “Imagine a motor vehicle fuel so clean-burning that you could drink the effluent from the tailpipe, with urban smog a distant memory” (Motavalli 140). This is the future of fuel cells. A computerized model shows that, when all is accounted for, a car with an onboard reformer could get seventy miles per gallon, while compressed hydrogen gets one hundred miles per gallon (182). A future fuel cell will be 99 percent efficient, complete with electrolyzer to make its own fuel. This is what dreams are made of. They will outperform all other engines and methods of fueling and will power everything from cell phones to power plants to cars. The future is near, and soon it will be here.

     Because of hydrogen’s abundance, cleaner emissions, and greater efficiency than oil, an oil-barren world will no longer be a problem. With many applications, high reliability, efficiency, and quality of power, hydrogen makes a likely candidate for fueling everything from cars to cell phones. Once a more efficient, nonpolluting method of acquiring pure hydrogen is found, hydrogen fuel cells will outrank all other engines in all classes. Erik Rhey once said, “... fuel cells have the potential to be to the 21st century what James Watt’s steam engine was to the 19th century” (Rhey 2). He could not have been more right.    

Works Cited
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Motavalli, Jim. Forward Drive. San Francisco: Sierra Club, 2000.
Nice, Karim. "How Fuel Cells Work." HowStuffWorks. [Online]. 18 May 2004
	
	<http://auto.howstuffworks.com/fuel-cell.htm>.
Rhey, Erik. "Fuel Cells." PC Magazine. July 2003: 92-93. [EBSCO]. 23 May 2003
	
	<http://search.epnet.com/>.
Rifkin, Jeremy. "The Hydrogen Economy." E Magazine: The Environmental Magazine.
	Feb. 2003: 26-36. [EBSCO]. 23 May 2003 <http://search.epnet.com>.
U.S. Department of Energy. "Challenges." U.S. Department of Energy. 27 Jan. 2003.
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U.S. Department of Energy. "Frequently Asked Questions." U.S. Department of Energy. 
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U.S. Department of Energy. "How Fuel Cells Work." U.S. Department of Energy. 13
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U.S. Department of Energy. "Types of Fuel Cells." U.S. Department of Energy. 27 Jan. 
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