1.2 Problem
It is no secret that supplies of economical oil will be exhausted in the 21st century. The search for alternative fuels has been in progress for a while now. Another challenge is to find a solution that would significantly reduce gas-emissions, while maintaining a high performance to attract consumers. Today, the most efficient solution is hybrid cars. Some automakers have already put on the market their own version. Toyota is selling the Prius, while Honda is selling the Insight. GM is almost ready to display its own hybrid car. As for hydrogen-based, more research needs to done before automakers are ready to produce them.
1.3 Scope
Because the time awarded to this research was limited, so is the content. The components that make a hybrid car will not be described nor will the types of electric motors inside the hybrid vehicle. Hydrogen as a fuel is analyzed; however, its usage in fuel cells is only briefly introduced.
2. DISCUSSION
2.1 Hybrid
2.1.1 Process
Hybrid automobiles are vehicles that use both gasoline and electricity for power. Unlike solely electric powered cars, hybrids don’t have to be plug in. It’s the gasoline engine that charges the electric motor. The combination results into better fuel efficiency than conventional gas-powered cars. The table 1 shows the difference in MPG (miles per gallon). The two hybrid cars, the Honda Insight and Toyota Prius, have significantly more MPG than their other models. This results in a huge difference in the annual fuel cost. Furthermore, hybrid cars can go over 100 mph, which is quite fast and highly superior to any electric automobiles. For addition information on the performance of hybrids, you can take a look at the specifications of the Honda Insight and Toyota Prius in Appendix A.
2.1.2 Parallel and Series Configurations
Hybrids are typically characterized by their driveline configuration as either parallel or series vehicles.
2.1.2.1 Parallel
Figure 1.1 illustrates a parallel hybrid. Both the electric motor and the gas-powered engine can drive the wheels [4]. This allows the driver to decide according to road conditions the one he wants to use. The electric motor, powered by batteries, plays a smaller role in the parallel configuration than in the series arrangement. It tends to be a smaller in size also. As for the internal combustion engine, it works just the same as in conventional cars.
Figure 1 Parallel Configuration [10]
2.1.2.2 Series
In series hybrids, the internal combustion engine is there to charge the batteries. This means that the batteries can be charged by an internal or external source. Only the electric motor drives the wheels. The big problem with this type of configuration is that the battery is always on, thus shortening its life. Figure 1.2 illustrates the series configurations.
The parallel configuration is more complex than the series, because it shuts on and off. This requires more mechanical components to link the electric motor and the gas engine.
Figure 2 Series configuration [10]
2.1.3 Energy Consumption
A great advantage with these hybrid vehicles is that they don’t need to be recharged. You won’t have to worry about how much time is left before your next charging session, since the motor has the capacity of recharging itself.
The interesting feature that hybrid have is the “idle stop”. This can happen when the car stops at a red. The gasoline motor automatically stops running and leaves the car running on electric power. When the driver pushes the clutch, the engine automatically restarts to get the vehicle moving from a dead stop. This makes it more efficient than pure gasoline cars since those vehicles waste energy when idled on the streets. By shutting down the gasoline motor, the vehicle saves the energy that would have been wasted.
Note
While the car is idle, the power steering and air conditioning are still operating even tough the car is dead silent.
2.1.4 Environment
One of the main reasons for the creation of hybrid vehicles is the need for cleaner cars. Hybrids have showed that they can reduce air pollution dramatically. They cut down gas emissions and greenhouse gases by 50 percent because of the “idle stop” feature as well as their smaller gasoline engine. For example, Table 2 shows the emissions produced by the Prius, Perf Prius and the Corolla.
Table 2 Exhaust Emissions [9]
a “Car values are vehicle exhaust (tailpipe) emissions. “TE” values are total emissions-car plus upstream, including fuel cycle emissions from raw material extraction through vehicle refueling. Pollutant emissions of Corolla are from test at 160 900 km; Prius at 193 080 km. All test made using California Phase 2 reformulated gasoline.
Over the years, the U.S. have fallen behind foreign competitors in clean car technology, and this has resulted in the world paying the price in the form of higher levels of urban smog and accelerated global climate change. “Now that U.S. President Bush has refuse the international global-warming treaty means that the U.S. industry is likely to face another period without firm policy signal for rapid development of hybrid technology [6].” Despite the low emissions produced, environmentalists are still not satisfied. The State of California has introduce a zero emission law that will be applied in 2003. This law says that automakers will have to produce at least ten percent of their productivity with zero-emission cars.[] The hybrid cars are not included in that group.
2.2 Hydrogen
2.2.1 Production
Why is hydrogen considered an alternative fuel? This is because it is the most abundant element on the Earth. It comprises of 75% of the environment [1]. The dependence on foreign countries for fuel would subsequently disappear. Furthermore, its physical and chemical properties make Hydrogen a good stable alternative fuel. Although hydrogen fuel is technology of the future, its idea dates back to a long time ago.
I believe that water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light, of an intensity of which coal is not capable. Some day the coal bunkers of steamships and the tenders of locomotives will, instead of coal, be stored with theses two condensed gases, which will burn in the furnaces with enormous heat energy.
…Water is the coal of the future. ( Jules Verne) [1]
Unlike fossil fuels that can be extracted, hydrogen has to be produced. Hydrogen can be produced from a variety of feedstock: natural gas, biomass and water.
2.2.1.1 Hydrogen from Natural Gas
Hydrogen can be produced by steam reforming with natural gas. However it creates a dependence on foreign countries.
2.2.1.2 Hydrogen from Biomass
Hydrogen can also be produced by biomass. “Biomass includes all organic substances, such as plants wood chips, bales of straw, liquid manure, and organic wastes [1].”This type of production favors countries with vast agriculture.
2.2.1.3 Hydrogen by electrolysis
Electrolysis is an interesting method of producing hydrogen since its main resource consists of water [3]. This process separates water in its basic elements: hydrogen and oxygen. This favors countries where cheap hydroelectricity is available.
2.3 Storage
One of the main disadvantages with hydrogen as a fuel is that it takes a lot of space to store it. In comparison to a conventional gas powered engine, it requires four times the storing space [5]. Hydrogen can be stored in two different shapes: compressed-gas cylinders and liquid hydrogen.
2.3.1 Gaseous State
Compressed-gas cylinders are made out of stainless steel and have a pressure level of 20 mPa (mega Pascal). Those cylinders are the same as those used for conventional gas-powered vehicles since hydrogen in gaseous state can be stored at room temperature. This type of technology is fairly simple.
2.3.2 Liquid State
Liquid hydrogen must be stored at very low temperatures; therefore special fuel tanks are necessary to prevent losses and to keep it cold. Liquefaction systems are light and compact, but refueling would be expensive and probably perceived as unsafe because of the low temperatures.
2.3.3 Transportation
Another important point is the transportation. Trucks or trains can transport hydrogen in both gaseous and liquid state. Insulation of the storage facilities is critical. Pipelines can also transport gas-hydrogen. In Germany they are two large distribution networks that have more than 50 km of pipeline. There haven’t been any accidents in 50 years.
2.4 Environment
Hydrogen is the cleanest fuel that is available [1]. The combustion is almost pollution-free. The main combustion product is water. The amounts of carbon monoxide, sulphur oxides, carbon dioxide or greenhouse gases are negligible. However, it does emit NOx.
2.4.1 Fuel Cells
Hydrogen used in fuel cells is the future. “A fuel cell is a device that transforms hydrogen and oxygen into electricity [3].” It will produce absolutely no emissions. Unlike the hybrid vehicle, the environmentalist would approve this fuel since it is “zero-emission”. There still much research to be done before automakers introduces these cars to the market.
2.5 Safety
A concern with hydrogen as a fuel is safety. In 1937, a fire destroyed the German zeppelin Hindenburg and killed thirty-six people. The accident was blamed on the hydrogen that was on board. According to retired NASA engineer Addison Bain, the hydrogen did fuel the fire, but it did not ignited. [3]He believed that it was a cellulose-doping compound used to coat the fabric covering. This tragedy has given a bad reputation for hydrogen safety. The truth to matter is that gasoline is also highly volatile and we have seen many car explosions. Some scientists are still arguing whether hydrogen fuel is safe to use for domestic cars or not. Some say that hydrogen is simply too volatile while others argue that it is safer because hydrogen is more buoyant and diffusive; therefore you must be inside the fire to burn.[3] What is certain is that hydrogen does not react like most gases.
3. CONCLUSION
3.1 Summary
Toyota and Honda’s hybrids seem to have been a success. They have been selling quite well unlike the electric cars that have been on the market. Their good performance, and affordable price have attracted consumers. Furthermore, the “idle stop” feature is a great way to preserve energy. Research on hydrogen are not yet developed enough for automakers to launch it on the market. The storage remains a big issue to solve and safety is still a concern.
3.2 The Future
Hybrid and hydrogen vehicles will help preserve our oil and make the air we breathe a little cleaner. Nonetheless, it’s still a matter of time before the oil runs out. Moreover, the vehicles produced aren’t perfectly “zero-emission”. These two alternatives to gasoline-powered engines are only a transition to the fuel of the future: fuel cells.
REFERENCES
[1] Walter Peschka, Liquid Hydrogen, New York: Springer-Verlag Wien, 1992
[2] Choosing an Alternative Transportation Fuel – Air pollution and Greenhouse Gas Impacts , Paris, Organisation for Economic Co-Operation and Development, 1993
[3] Jim Motavalli, The Race to Build “Clean” Cars for the Future, San Francisco: Sierra Club Books, 2000
[4] Daniel Sperling, Future Drive – Electric Vehicles and Sustainable Transportation, Washington, D.C.: Island Press, 1995
[5] ; Peter Kushnir; Army Logistician, Fort Lee; May/Jun 2000; Vol. 32, Iss. 3; pg. 10, 3 pgs
[6] ; Eban Goodstein; The American Prospect, Princeton; Sep 24-Oct 8, 2001; Vol. 12, Iss. 17; pg. 8, 2 pgs
[7] ; Eric Peters; Consumers' Research Magazine, Washington; Jun 2000; Vol. 83, Iss. 6; pg. 10, 5 pgs
[8]
[9] Lester B. Lave & Heather L. Maclean, Are Hybrid Vehicles Worth It?, IEEE Spectrum, New York; Mar 2001; Vol 38, Iss. 3; pg. 47, 3 pgs
[10] http://www.soton.ac.uk/
Appendix A
