2.1. Vehicle Emission Standards.
The effects of these emissions (as seen in Fig. 1) have resulted in various international initiatives to raise a general awareness of the dangers and effects of pollution on ecological systems. It has also been, therefore, a common motive for companies in the industrial sector to work towards decreasing their emission levels, usually in obligations to hold to certain regulations. Examples of such regulations are the Euro Emission Standards, which have been applicable across numerous countries (in and outside the EU) conforming to it by decision:
Fig. 2
The table in Fig. 2 shows emission standards for cars of construction dates after 1992 to after 2005 (as projections). The numbers represent mainly emission limits. Going down, these limits seem to get tighter and tighter, such that new innovations are expected to keep car emissions at a minimum.
Of the various technological developments that might offer a cleaner alternative to internal combustion engines I intend to consider the pros and cons of fuel cell systems in road vehicles. In places where they could in future be widely marketed, they are expected to not only meet emission standards (like the EU’s) but to bring emissions down and decrease the harmful effects of driving on the environment. However, it is important to realize what sets it apart from previous attempts to do the same in other developments that offered ecologically safe systems. Also, how does a fuel cell battery compete with a combustion engine? This paper looks at the kind of alternative the fuel cell system would be.
3. Background.
A fuel cell is an electrochemical device in which a chemical reaction takes place. The reaction changes chemical into electricity. A sufficient size and number of fuel cells can generate enough electricity to power vehicle motors and systems, among other things.
A claim in the Britannica encyclopedia says that the use of fuel cell systems can be traced all the way back to the 60s, when they were first being developed. Companies like UTC Fuel cells have provided fuel cell technologies to NASA since the Apollo space missions. Apparently, the technology was developed as scientists were in search of high-efficiency, stable power supplies for machines that were to go into outer space and needed reliable power sources. It seems to have been ideal for this task because, even today, these devices are found in almost all satellites and spacecrafts alike.
4. Principle of the Fuel Cell System.
The complexity of how fuel cells work in cars can probably be compared to that of a combustion-engine vehicle. These basic charts outline this similarity:
COMBUSTION: FUEL → HEAT → IGNITION → ENGINE → WORK
FUEL CELL: FUELS → FUEL CELL → REACTION → DC → MOTOR → WORK
Hydrogen gas is fed to each cell’s anode electrode to eventually make energy. The electric motor runs on this energy and does work. Although the onboard storage of hydrogen is considered to be a problem because of space and safety, manufacturers in Berlin, Lisbon and Copenhagen claim to be successful in storing it on bus structures that are to function in future. They store it in its liquid form at very low temperatures to have a higher concentration of energy per unit volume. It is also known to have been contained onboard the car structures of a series of FCV prototypes in pressurized tanks. Below is the diagram of a Fuel Cell Bus concept design, which would use liquid hydrogen:
Fig. 3
This is the concept for a fuel cell-driven bus to be manufactured by MAN in Germany. The fuel cell battery takes the place of a diesel engine, with another high-energy battery storage to assist when there is additional peak load. The hydrogen is stored as liquid in an LH2 storage system (consists of “vacuum super-insulated bottles”) which is able to store it at –253oC. This storage system contains 700 liters of liquid hydrogen, which will be adjunct to a safety system. The website of this source also says that under these conditions this storage would be lighter and less voluminous than the storage of gaseous hydrogen. Initially the bus will or has been tested for an extended period before beings integrated within suitable bus fleets.
There are a few things we can also deduct from the diagram in Fig. 3 about the principle of fuel cells in vehicles. Firstly, for a large commercial vehicle, the concept seems like it could be rather practical with regard to weight and spatial distribution. In an unusual installation, these hydrogen tanks are located at the top of the bus structure above the driver and passenger seats. It seems the manufacturers have made this possible without the cost of passenger space and thus comfort inside the bus. In this representation of their size, they are still larger than the gasoline storage size that such a bus would have. The weight seems to be also evenly distributed between the front and back of the bus by the tanks and the battery/drive unit. Adding to this balance are the tanks on either side of the bus. This gives optimistic insight to getting fuel cell vehicles in public transport.
4.1. Generating Electricity with Hydrogen + Oxygen
Many articles argue that probably the biggest advantage that fuel cells have over other power-supplying devices is their ability to generate power and to do it by very clean, efficient and usually practical means. What a fuel cell does is it converts the energy of chemical reactions of two fuels directly to DC (Direct-Current) electricity at a constant rate. The chemical reaction is that of hydrogen and oxygen, which if supplied continuously would give continuous electrical energy. As power is drawn from the cell, the tank provides the hydrogen to maintain the chemical process at the same time. The unique function of the fuel cell in an FCV is probably what might set it apart from most other vehicles in development. These fuels, if they can be made readily accessible, are capable of producing power in fuels cells without the cost of making many pollutants or byproducts. This would make fuel cells a better alternative to the internal combustion engines powering transport vehicles.
During the oxidation of hydrogen with oxygen from the air, the only major byproduct produced is supposed to be pure water along with heat, which is considered to be minor. The water is produced at a fuel cell’s cathode where hydrogen electrons are bonded with their ions and, combined with oxygen, create water. This shows fuel cells using hydrogen and oxygen to generate electrical energy by chemical reactions that must cause a flow of electrons, and not by using them as fuels to create what would be thermal energy.
4.2. Other Fuels for Running Fuel Cells
Today fuel cells are being made that use substances that are rich in hydrogen. Manufacturers have expressed their concern that it would be much more convenient for consumers in general if fuel cells could function on alternative fuels that are more available. Due to such concerns some have focused their developments towards enabling fuel cells to do just this. The fuels to be used are categorized within the so-called hydrocarbon and alcohol groups. Manufacturers are considering fuel cells that function on propane, natural gas or methanol. Their use in fuel cells is explained by their hydrogen content and how practical they are in being handled and distributed. Apart from that, more problems with the storage of hydrogen would be alleviated because of an increased energy per unit volume (like in the case of liquid hydrogen). These alternative fuels are mainly being considered for the fuelling of fuel cell vehicles because of the perceived difficulties of also handling pure hydrogen.
Propane and natural gas for instance have been used as heating and cooking fuels in many households, meaning that living in a house with this supply would enable one to refuel using one’s own gas pipe. Apart from these fuels, methanol as a liquid fuel has similar properties to the gasoline fuel used in cars, meaning that it would be as easy to transport and distribute through filling stations. Using fuels that are not so radically different from what we use daily would help boost confidence in this technology.
Alternative fuels also has a slight disadvantage when it comes to functionality and . To be able to run on these alternative fuels the fuel cells need a “reformer”, which must extract this hydrogen from the fuels. Reformers are sometimes thought to be important in making fuel cell technology successful, because it allows for alternative power sources. However, they generate more heat and emit some amount of carbon dioxide apart from hydrogen, which ends up decreasing the efficiency of a fuel cell. Furthermore, the system becomes more complex and more expensive to build and service. Fuel cells, then, are capable of running on hydrogen rich fuels that may be more readily available, but as they must do so through reformers, it is achieved at the cost of efficiency and being clean.
5. Comparison of Fuel Cell with Combustion Engine.
5.1. Efficiency
Efficiency is used to compare the performance of machines, specifically those which are designed to do work. To put it into perspective, one definition says that it is the ratio of useful energy obtained from a machine to the total energy transferred (the work done).
All machines waste some energy in the process of doing work, as it can be lost as heat and sound in the presence of friction, incomplete combustion and other incomplete chemical reactions. It is because of this that a machine’s efficiency is always less than one; this is true for all engines. The majority of energy is wasted in an engine and goes to the cars exhaust and creates other wastes such as carbon dioxide and smog. Engines are quite inefficient in this way, meaning they generally do not make the best use of the energy.. When talking about increasing the efficiency of a car i.e. the efficient use of fuel in powering the car, the decrease of wasted energy is meant, and this is commonly achieved by consuming or burning less fuel.
Probably one of the more revolutionary benefits of fuel cell systems is its concept to maximize efficiency to levels that we have never known before of any other vehicles of the past. The internal combustion engines in automobiles that we are used to cannot convert much more than 20-25 percent of energy in the gasoline into energy used to do mechanical work. Cars that are powered by hydrogen fuel cells using electric motors on the other hand are a lot more efficient in that they make use of between 40 and 60 percent of the fuel’s energy. Another source also quotes that these cars have the potential to be up to 80 percent efficient. Even using hydrogen-rich fuels like gasoline, their efficiency is twice as good as an internal combustion engine’s. The design flexibility of FCVs, managed by using four small electric motors instead of one large one, allow for light, aerodynamically perfected structures (which reduce the air drag of the vehicle) to which some of this efficiency is owed. The technology responsible for this efficiency seems to be unmatched by other vehicles and improves efficiency dramatically.
5.2. Mileage
The reformers that can be used with alternative fuels help increase the mileage of the vehicle as a single tank of any hydrogen-rich hydro-carbon would have enough hydrogen to power an FCV for the same distance as a conventional vehicle – over 480 km – as opposed to the 320 km it would travel on a hydrogen tank with it compressed at about 3.5*106 kg/m2. In the meantime researchers are designing and testing tanks that are capable of storing more hydrogen at higher pressures, to improve mileage to present standards.
5.3. Safety
When we consider the safety of a device, we look at the safety issues linked with using the technology and how it may affect consumers.
With hydrogen there would be many risks involved when having to handle the fueling or storage of it, as there are with gasoline. The difference here is that we would not be at all familiar, as ordinary drivers, with handling this fuel in a car or on the road. In another argument, some researchers believe that hydrogen is less dangerous than most other energy-carrying fuels because of its properties. Here is a table I found that supports this view:
Characteristics Related to Fire Hazards of Fuels
Fig. 4
The figures outline what could be valid points that hydrogen in air diffuses quickly and has an almost insignificant density for flammable conditions. The properties shown here suggest that the potential to catch fire compared to other fuels is very low.
Despite this, as long as there are well-grounded concerns that hydrogen may still be a dangerous alternative to gasoline as a fuel it makes it harder for some of us to see it as being necessarily better.
5.4. Cost
At the moment fuel cell technology is relatively expensive, making present FCVs in many cases too expensive for most consumers to afford. While there is confidence that such cars will help improve the state of our environment, not many people are willing to pay so much money on the short term. The web site fuelcelltoday.com reckoned that in December of 2003 a fuel cell stack alone cost about £400,000+. Although it is a well-desired product of technology, the sum of half a million pounds for a medium-performance car would not allow it to compete with others on the market and make an impact.
In order to make FCVs a successful alternative, manufacturers would have to find efficient, cost-effective ways to produce them.
6. Introducing Fuel Cell Vehicles.
Fig. 5 The developments of the newest FCVs have been aimed towards creating vehicles that fulfill our transportation needs and at the same time do not harm the environment. In this there is the difficult task of satisfying the environmentally conscious and also drivers in general. Ideally, people driving such a car would not miss out on a significant amount of performance, cost or convenience benefits compared to most of today’s drivers. Making a car to fulfill this role has taken The above diagram shows a Ford P2000 FCV prototype, where at least in the body structure there is very little to tell it apart from what we see all the time. It differs mainly in its inner auto components, where the focus has been. Its technologies have excelled where a higher performance and certain conveniences have been asked of non-combustion vehicles. For instance, a compact and small set of electric motors and fuel cells (the battery) can allow for design flexibility and lightweight structures.
Fig. 6
The outer design structure of this FCV is no more than a lightweight semi-detachable frame. The same fuel cell platform/chassis can be secured on to several different designs. Most of the crucial functional integrations such as steering, gears, transmission, and electronics are supposed to be pre-installed with seats on the platform so that changing model designs is made easy.
Fig. 7
6.1. Question of Reformers
The use of “reformers” is in question because they emit some CO2 and add to the complexity and cost of the vehicle. There are several particular disadvantages that stir the uncertainties:
- Apart from complexity and cost and complexity, reformers add to the maintenance requirements of a fuel cell system
- It could decrease the performance of the cell if it allows any carbon oxides to reach the cell anode
- It emits small amounts of pollutants and greenhouse gases
I believe manufacturers will maximize efforts to use hydrogen tanks and get wholly efficient FCVs on the market as they have come so far in the development of them.
On the left is a fuel cell stack. A single fuel cell in an FCV produces less than 1.16 volts of electricity, which produces far less than the required 70 or so kilowatts needed to propel a normal passenger vehicle to the speeds we use. Such fuel cell stacks accommodate multiple fuel cells (over 100) to be able to provide sufficient power. The amount of power generated depends on the number and size of each cell.
Fig. 8
6.2. The PEM Fuel Cell
The type of fuel cell typically used in an FCV is called a proton exchange membrane fuel cell (PEMFC) – sometimes called a polymer electrolyte membrane. Of the several kinds of fuel cells, this uses the simplest reaction to produce electrical energy by using hydrogen and oxygen. Just how the PEMFCs work can be modeled by the diagram below:
Fig. 9
In 1 to 4 of this diagram, the process of how such a PEMFC comes to generate electricity and only make water as a byproduct is explained. It is evidently quite different to the type of cell found in a regular car battery, but this shows the logical manner in which a continuous current is made (by the flow of electrons). As the light bulb represents the connection to what would be the electric motor, among other electrical devices, it is easier to see the electrochemical powering of cars as an alternative to powering by combustion.
7. Fuel Cells in Today’s Consumer Vehicles.
More FCVs may arrive on the scene as early as 2004, which is the time when companies like Ford and DaimerChrysler plan to release their limited productions of a new line of fuel cell-powered cars (based on Ford’s P2000 and DaimerChrysler’s NECAR 4 prototypes). Only these two manufacturers have announced mass-market FCVs for the year 2004, with Ford reported to have the slight edge with an earlier release date. Other FCV developers like Honda and Toyota are not expected to offer such vehicles until later this decade. One might ask how manufacturers like Ford envision the management of their FCVs in places that have not yet adjusted their systems to support and service them. As it turns out, owners of these Ford vehicles will buy tanks of liquid or gaseous hydrogen and presumably use them to refill their onboard hydrogen tanks. The P2000’s power system also uses the fuel stacks that house a combined total of 400 PEM cells, which produce a sufficient 90 kilowatts of electric power. A conventional car battery is also used to operate some of the car’s electrical system and store energy recovered from regenerative braking technology. The end product would be that it performs much like the Ford Taurus, only more efficient and, an underlying factor, more ecologically safe; having 35 less horsepower it is also 40 percent lighter and can so match the Taurus’ performance.
8. Conclusion.
Many features of fuel cell systems suggest that they would make adequate alternatives to combustion engines. This success in road transport is mainly due to their efficiency, their relatively high performance in comparison to other highly efficient non-combustion vehicles and their use for public transport. It has to be said though that their potential to make an impact on human transportation is hindered by other shortcomings that make it difficult to choose an FCV over a conventional, high performance car.
I believe the prospects of future FCVs look good, when one considers the capabilities that these developments can foretell. At the same it is difficult to predict, simply on a technological basis, how they would fare in replacing present-day cars to reduce emissions. FCVs are arguably one of the most anticipated technologies for the future auto industry. In my study, fuel cell systems have definitely shown the potential to change the experience and effects of driving in the next one to two decades. However, they may not offer a feasible alternative within the next two years mainly because their technologies would still have to gain the appreciation of whole societies before its benefits are realized.
At the moment fuel cell systems may seem radically new and unfamiliarity with them might even put people off at first. Still, having been in use for a while by research organizations such as NASA they have, at least, gained the confidence of a select few after their functions in space shuttles. If such a confidence grew, fuel cells in FCVs may have a positive impact on vehicular emissions as an alternative to combustion engines.
References/Bibliography.
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Breiter, Manfred, Electrochemical Processes in Fuel Cells (1969)
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Colin, A. Vincent, Modern Batteries: An Introduction to Electrochemical Power Sources (1984)
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Linden, David, Handbook of Batteries and Fuel Cells (1984)
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Noyes, Robert, Fuel Cells for Public Utility and Industrial Power (1977)
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Energy Conversion, Britannica (1999)
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Fuel Cell, Encarta Premium Suite 2003 DVD
- http://auto.howstuffworks.com
- http://forwarddrive.com
- http://www.bizjournals.com
- http://www.eihp.org
- http://www.fueleconomy.gov
- http://www.globaltechnoscan.com
Sources to come
Department of Transport: Transport Statistics, Great Britain
Emission Standards: EU, http://www.dieselnet.com/standards/eu/ld.html
Fuel cell test, http://www.bizjournals.com/pacific/stories/2002/01/07/daily21.html
Fuel Cells, Energy Conversion, Britannica
Fuel Cell Bus, http://www.eihp.org/eihp1/workshop/experts/bvg/index.html
How Fuel Cells Work – Problems with Fuel Cells, http://auto.howstuffworks.com/fuel-cell3.htm
Tim Kirk, Physics for the IB diploma, Energy and power. Oxford 2003.
T. Nejat Veziroglu. Hydrogen Energy System: A Permanent Solution to Global Problems. University of Miami
Mark Cropper, Driving the future – the Ford Focus Hybrid Fuel Cell Vehicle, Fuel Cell Today.
Ford P2000 Fuel Cell Vehicle, http://www.fueleconomy.gov/feg/fcv_components.shtml
Fuel Cell Chassis, http://www.fueleconomy.gov/feg/fcv_benefits.shtml
First Drive-by-Wire FCV, http://www.fueleconomy.gov/feg/fcv_whatsnew.shtml
Fuel Cell Stack, http://www.fueleconomy.gov/feg/fcv_PEM.shtml
PEM Fuel Cells, http://www.fueleconomy.gov/feg/fcv_PEM.shtml