Neal+Ryan+Final

=The Hydrogen Car: From Theory to Reality (Including Safety, Greenhouse Gas emissions, and Infrastructure) Using One Possible Adaptation: PEM Fuel Cells=

Abstract
The hydrogen car has been a talked about subject for eliminating greenhouse gas emissions for years. There are many variations of this car, as well as numerous fuel cells to power it. This paper will discuss the use of PEM fuel cells to power these cars, as well as the safety, greenhouse gas emissions, and infrastructure involved with the implementation of this car.

Overview of the Hydrogen Car
A hydrogen power car works the same as an ordinary car. It runs, drives, and contains nearly all the same systems as a normal gasoline or diesel powered car. The main difference between a normal car, and that of one powered by hydrogen, is that a hydrogen powered car either burns hydrogen in a normal combustion engine to increase the efficiency of the engine, or contains a hydrogen fuel cell that powers the car without the need of a fossil fuel. Many car manufacturers have started creating hydrogen powered cars for that very reason. This decision is also compounded by the fact that there is a finite supply of fossil fuels available to the human population. The benefits of this form of technology environmentally are explained in detail: “Current fossil-fuel burning vehicles emit all sorts of pollutants such as carbon dioxide, carbon monoxide, nitrous oxide, ozone and microscopic particulate matter. Hybrids and other green cars address these issues to a large extent but only hydrogen cars hold the promise of zero emission of pollutants. The Environmental Protection Agency estimates that Hydrogen fuel cell vehicles could reduce greenhouse gas emissions by 41.4% using the steam reforming process to produce the hydrogen fuel.(1) Should a new technology for the creation of hydrogen fuel arise that doesn’t involve the use of fossil fuels, these cars would be truly 0 emission vehicles. This is because unlike hybrids, hydrogen powered cars use only emit water vapor, which is a non-greenhouse gas emission. It has also been said that these cars should be in mass production by 2015, and what’s more, they will be remarkably similar to an internal combustion vehicle, as Tom Mcghie said of The HydroGen4 made by General Motors, and developed at the Opel-Vauxhall research center in Germany: “The new car can travel 300 miles on a single tank of hydrogen -- a by-product of the petrochemicals industry. The cost per mile will be similar to those of normal cars. The car can top 100mph, with acceleration comparable to a conventional car and is silent when running.”(2)

It should be noted that not everyone believes Hydrogen cars are the way of the future. David W. Keith and Alexander E. Farrell are two opponents of this technology, as well as Roger A. Pielke Jr et. al (mentioned below) believe that there may be reasons to avoid hydrogen fuel cell vehicles. The former, Keith and Farrell believe these HFV’s are only viable in the long run, while the latter, Roger A. Pielke Jr et.al have questions of their legitimacy entirely (explained later). Keith and Farrell’s concerns are that while hydrogen fuel as a long term solution is viable, in the short term, it is far from a reality. Efficient vehicles will likely not be seen for another 25 years, and before that time, we should be focusing on electric vehicles. There should also be an emphasis on heavy freight vehicles like trains, ships, and trucks, because they pollute more and the benefits for increasing they’re efficiency would be more quantitative. (3)

How A Hydrogen Fuel Cell Works
A hydrogen fuel cell works very much like an everyday battery. A chemical reaction takes place, and this reaction generates energy, which creates electricity to power a battery that powers the car. However, unlike a common battery, a hydrogen fuel cell is replenishable, and only needs more hydrogen and oxygen fuel to continue the reaction. A hydrogen fuel cell converts chemical energy directly into electrical energy. This process happens with no moving parts whatsoever, and emits no pollutants or harmful greenhouse gases. As long as fuel is supplied to the cell, it can convert it into direct current that can be used to power any most anything, in this case a car, much like any normal battery. A combination of cells can be linked together in a parallel or series circuit (called a fuel-cell stack) to increase the current output or electrical voltage. (4)

A basic explanation of the workings of a hydrogen fuel cell goes something like this: At the anode, diatomic hydrogen is ionized in the reaction: 2H2 => 4H+ + 4e-. Electrons generated from this reaction pass through a circuit, where the flow is harnessed as electricity, as they travel to the cathode. At the cathode, diatomic oxygen reacts with the protons and electrons generated in the first reaction at the anode to produce water in the reaction: O2 + 4H+ + 4e- => 2H2O.(5) “[Hydrogen] Fuel cells function by capitalizing on the movement of the electrons that takes place in this redox reaction. This is accomplished by routing the electron flow through an external circuit that can be used to power electrical loads. The end result of this reaction is an efficient conversion of hydrogen fuel into usable electricity."(4) Figure 1 shows this process in action.

Fig. 1: How a PEM Fuel Cell works. (6)

Hydrogen Fuel Cell Safety Questions
Some critics of HFV’s have argued that these vehicles are potentially explosive, and thus would be a danger to the people who drive them. Hydrogen gas, H2 is stored in a large tank in the car, and compressed to very high pressure to increase the amount available which extends the driving range. (7) This often leads to the myth that hydrogen cars are hydrogen bombs waiting to happen. However, while the compressed hydrogen does carry a small explosion potential, the idea that a hydrogen powered car is equivalent to a hydrogen bomb is a complete fallacy. The fuel cell from a hydrogen car works very differently from a hydrogen bomb, and no fission or fusion is needed. Critics of these cars have however pointed out that they could potentially be used as pressurized bombs, and contain the explosive power of 220 pounds of TNT. (8) This is something the automotive industry will have to work around if these cars are ever able to make it to the market.

Hydrogen fuel must be stored at high pressure or in cryogenic tanks, which creates a problem for manufacturers, as this would be tricky to do in a car. However, there have been recent discoveries that could make this necessity a thing of the past. One of these comes in the form of storing these fuels in a solid state: “A possible solution is to store hydrogen in a safe chemical form. Earlier this year, Williams and his team figured out a way to release hydrogen from an innocuous chemical material - a nitrogen-boron complex, ammonia borane - that can be stored as a stable solid. Now the team has developed a catalyst system that releases enough hydrogen from its storage in ammonia borane to make it usable as a fuel source. Moreover, the system is air-stable and re-usable, unlike other systems for hydrogen storage on boron and metal hydrides.” (9)

A different team found that the best solution to storing the fuel for HFV vehicles on a per cost basis, and using H2 gas instead of a solid compound, was found to be lowest pressure of those tested. It was according to M.D. Paster: “[A] Type III uninsulated carbon-fiber two-tank configuration, designed with a safety factor of 2.25. (The tank is designed so that the burst pressure is at least a factor of 2.25 times the working pressure which in this case is 350 bar) Modest-pressure ambient-temperature gas storage results in very low volumetric efficiency but also relatively low capital cost” This would still be very high pressure for a vehicle though, and would mean convincing everyday consumers of these vehicles’ safety would still be a concern. (10)

PEM Hydrogen Fuel Cell at A Glance
PEM fuel cells are one of the many cells that are being developed to use in hydrogen cars. It is one of the best options, for the reasons below, as well as one of the simplest. “The PEM (Proton Exchange Membrane) fuel cell functions through the use of a specially designed and produced polymer that acts to create a voltage difference with the addition of hydrogen fuel and oxygen” It is a good starting ground for hydrogen fuel cells because it is simple, easy to set up, and viable in most applications. PEM fuel cells operated on hydrogen (H2 gas) and oxygen (from the air). The only by products of this operation are electricity, water, and excess heat. Electricity is produced via the electrochemical process of oxidation-reduction (described above), which happens in the respective anode(oxidation) and cathode(reduction) in two separate and simultaneous half reactions. “PEM fuel cells have a theoretical maximum efficiency of 83%; however, to obtain a usable amount of power, fuel cells operate at lower efficiencies, usually between 30 and 60%.”(4)

PEM Fuel Cell Efficiency/Output
The watt hour per kilogram (Wh/Kg) of a PEM fuel cell exceeds 400, which is many times better than most rechargeable batteries (the energy source for electric cars on the road). This would provide for more efficient transportation, and will reduce weight, helping to decrease energy needed to power the vehicle. (11) “The best case scenario the fuel cells can be produced at $100/kW, operate at 50% efficiency, and generate electricity at <$0.08/kWh if hydrogen can be supplied at $10/GJ.” (12) It should also be noted that this efficiency degrades slightly over time. There is also a minor hiccup for running a car in that change in fuel cell output also needs to be accounted for with this new technology. The voltage output follows a 20-50 μV/h increase for the first few thousand hours, and then levels off to less than 3 μV/h after that. While this doesn’t present a major problem, it is something to consider. This may also be minimized with good materials and careful preparation. (13)

Current/Voltage Ratio and Fuel Efficiency
The current-voltage relation of a hydrogen fuel cell is given by the equation V = .787 - .0533(log(i)) - .148i + (Vcomp / exp) – Vreformate (14) Where V is the voltage output by the cell in volts I is the current density in ampere per square centimeters Vcomp/exp is the “voltage correction for power consumed/generated by net air compression/expansion, =−0.08 for hydrogen; =+0.067 for methanol reforming; =0 for gasoline POX.” Vreformate is the “voltage penalty due to H2 dilution when operating on reformate=0 (hydrogen); =0.06 i for methanol reformate; =0.128 i for gasoline POX.”(14)

Valid for cases where i is between 0 and 1.5 A/cm^2

Fig 2: Comparison of different PEM fuel cells (PEMFC stands for PEM fuel cell). (7)

Figure 2 above shows three fuel cell vehicles, one run on Hydrogen, one on methanol, and one on gasoline. It should be noted that while the Hydrogen car has the least range, it is by far the most energy efficient.(7)

It was found that the efficiency of the PEM Cell was also related to the temperature of the fuel as well. Figure 3 shows this rather odd correlation.

Fig. 3: Cell performance for different temperatures (30-100 C) in H2/250 ppm CO. Uppermost curve is pure H2 at 80C.(15)

Where will this fuel come from?
Naturally, this brings about the question of how to obtain the fuel for these vehicles. In a society where we grow more and more concerned about fossil fuels, and how they can continually be obtained, we need a fuel that is easily obtained. Hydrogen, H2 as it occurs in its stable form, is easily the most abundant element in the universe (16). It is rarely found in this form however, and must be forced out of compounds which contain hydrogen, such as H2O or hydrocarbons. There are many processes to do this but two of the most common ones are electrolysis and steam reforming. In electrolysis hydrogen is taken from water using electricity. The process is described like so: “electricity is used in the presence of a catalyst to separate the hydrogen from the oxygen in the water.” Using this method, it is possible to eliminate the CO2 emissions of a car completely, provided renewable electricity is used. (17) Another approach is to liberate the hydrogen by "reforming" fuels such as natural gas or methanol. Hydrogen fuel, H2 can also be created through the process of steam reforming, using natural gas, which accounts for almost half of hydrogen fuel. Jeremy Rifkin described the process as follows: “natural gas reacts with steam in a catalytic converter. The process strips away the hydrogen atoms, leaving carbon dioxide as the byproduct (and, unfortunately, releasing it to the atmosphere as a global warming gas). [ . . .] Hydrogen can also be processed from gasoline or methanol.” (18) However, unlike electrolysis, steam reforming doesn’t eliminate CO2 emissions. It does reduce them by up to 50% over gasoline vehicles though.6 (6) What’s more, this fuel has to be implemented on a large scale, which is a daunting proposal, not only for the construction, but making it profitable. David W. Keith and Alexander E. Farrell note that while hydrogen fuel is cheaper to refine than gasoline, which would inherently make the fuel cheaper to consumers, it is much harder to distribute and store, which would increase the cost of the proposed fuel: “Today, hydrogen is produced from natural gas on a large scale and at low cost: hydrogen production consumes ∼2% of U.S. primary energy, and at the point of production, it costs less than gasoline per-unit of energy. Although hydrogen production is simple, as a low-heating-value, low-boiling-point gas, it is inherently expensive to transport, store, and distribute—all strong disadvantages for a transportation fuel.”(11) This means that while it is cheaper to create, it’s more expensive to get to customers, and will likely result in consumers being less than willing to switch over to hydrogen cars, or bother with the large investment required to obtain one. Environmental Impacts of the HFV

One of the major upsides for the hydrogen car over the plug in electric car is its ability to reduce carbon emissions dramatically. To this end, C.E. Thomas noted “Most electricity in the United States is generated by burning coal [. . .] coal emits nearly twice as much carbon as does natural gas, the fuel most commonly used to generate hydrogen. In addition, fuel-cell electric engines are twice as efficient as the combustion engines that are still required in hybrids”(23) While that means that using the best current technology (steam reforming) to produce the hydrogen fuel necessary to run a HFV, the vehicles are not zero carbon emission, however, they emit half as much greenhouse gas pollutants as any current vehicle. The possibility for a zero emission HFV is still possible; however, the process of creating the fuel for them would have to be using a new technology that does not involve the consumption of natural gas or any other fossil fuel.

Are HFV’s Really Zero Emissions Vehicles?
To the claims of hydrogen cars having zero emissions, one MIT researcher said: “ ‘Ignoring the emissions and energy use involved in making delivering the fuel and manufacturing the vehicle gives a misleading impression’ “. (19) However, while it is certainly try that the making of Hydrogen fuel does emit greenhouse gases, as previously mentioned, it is an unfair argument to say that making the vehicle leads to greenhouse gas emissions, as this would be the case with any type of car made until the technology to make them improves. Having taken all that into account, it can still be said that Hydrogen cars will reduce the emission of greenhouse gases by a significant amount over their competitors. However, it has been stated that even though they emit less pollutants, there have been claims that the water vapor these cars produce could affect local humidity, and thus upset the environment. To this end Roger A. Pielke Jr and his fellow researchers from the University of Colorado explain how water vapor could affect the environment: “Variation in water vapor affects local, regional, and global climates. Data on such effects are sparse because of complexities in the water vapor life cycle. However, our preliminary calculations indicate that a complete shift to fuel cell vehicles would do little to slow water vapor emissions, which presumably have increased perceptibly in some metropolitan locations through the growth in use of internal combustion engines. In some locations, changes in relative humidity related to human activity have arguably affected local and regional climate. Depending on the fuel cell technologies actually employed, relative humidity in some locales might conceivably increase by an amount greater than with internal combustion engines. This increase could lead to shifts in local or regional precipitation or temperature patterns, with discernible effects on people and ecosystems.” (20)This brings up the great point he makes, that while the effect of this water vapor, which we haven’t really explored, may very well be less harmful than the greenhouse gases emitted by cars (and in all likeliness, this is the case), we should take the time to not on study, but also consider these effects before we charge ahead with this technology. (10)

Infrastructure
Building the infrastructure for these cars is a much different story. It has been said that the infrastructure for these new breed of cars would be very expensive, and may very well be what hinders the technology. David W. Keith and Alexander E. Farrell quantify this estimate: “Although technically feasible, a hydrogen refueling infrastructure would be expensive: initial cost would likely exceed $5000 per vehicle even if one assumes large economies of scale.”(3) This however, has not stopped most of the big car companies from developing a hydrogen fuel cell vehicle. However, John Dodge says it will be many years before they are effectively available to the market: “FCVs like the Chevy Equinox, Honda Clarity, Hyundai Tuscon and BMW's Hydrogen 7 are among the 45 or so built so far. Even with consumers clamoring for cheaper and cleaner alternatives to gasoline, moving to an entirely new technology will take years if not decades to clear the formidable technical and economic hurdles.” (11) Another problem for these vehicles, and the new technology is customer expectations. As with all new technology, customers will be expecting the newest and the best, and if the car they pay so much for only goes 100,000 miles before breaking down, they won’t be happy. (21) This leads into the refueling problem. The Chevy Equinox FCV (Fuel Cell Vehicle) took over 7 minutes to fill from a half full tank, which will be a problem for companies trying to sell these cars, as customers won’t be so patient at the pump.(11) All of these things will have to be worked out on a nationwide scale before the car can be implemented.

Government Research into Infrastructure
FreedomCAR (Cooperative Automotive Research) is a program run by the U.S. government, through the U.S. Department of Energy Efficiency and Renewable Energy. It has focused on the helping research more environmentally friendly, less greenhouse gas polluting vehicles for highway transport. It aims specifically at battery powered vehicles, like hydrogen cars, as well as the infrastructure to transport and sell these cars on an everyday basis. (22) The Department of Energy has also done research into the storage of this fuel on board vehicles: “In recent years, DOE has backed research on some 200 different storage materials, ranging from packing hydrogen into metal solids called metal hydrides to a slurry of alane powder in a light mineral oil. To date, none meets DOE's targets for storing and releasing enough hydrogen fuel on demand.” (23)

Conclusion
The hydrogen car is certainly a viable solution to eliminating greenhouse gases, although more research needs to be done in to creating hydrogen fuel without fossil fuels, and whether or not the water vapor produced from these cars will not be harmful, there is certainly the possibility that the HFV's could eliminate greenhouse gases if operated with this in mind. While the infrastructure to implement these cars isn’t ready just yet nationwide, there have been initiatives to make it so. The PEM fuel cell, while only one idea to power this car, is certainly a viable solution, and has the potential to be the lead platform, as it is both energy efficient, and capable of doing the job.