pressure towards exhaust reduction (like nitrogen oxide, sulfur, carbon monoxide, carbon hydrogen and lead). Also the problem of overall energy consumption is being addressed. Modern technology such as electronic motor management and catalytic converters so far achieved major improvements. In terms of carbon dioxide generation, however no good solutions have been found. The usage of petrol is becoming more difficult. Therefore much effort is underway to replace petrol with the following liquid fuels: • Liquid gas: it is mainly considered because natural gas supply is more abundant than oil. • Regenerative fuel (biological alcohol and gas): regenerative fuel is a renewable form of energy. Therefore it can not run out ever though the total amount of power is limited by the available production area. Regenerative fuels also produce exhaust, but it is not increasing the amount of carbon dioxide in the atmosphere. • Liquid hydrogen: since it is mainly produced by electrolyzing water, the future availability is limited by the availability of electric energy. This fuel does no increase the amount of carbon dioxide in the atmosphere. Hydrogen can be used to generate electric power directly by fuel cells. Since hydrogen is difficult to store and transport, its use is subject to many research projects. A special focus is in generating hydrogen from solar electric power collected at remote sites around the equator. Major problems are the limited efficiency rate of the electrolysis (70%) and its price. Solid fuel like coal and wood are another form of chemical storage. Because it is difficult to handle, solid fuels are not used for smaller vehicles. Traditionally they are used for trains and ships. The uses of solid fuel for transportation seem to become less important. Electric energy storage in batteries is another form of chemical storage. At the beginning of the automobile age, battery powered cars had an important market share. Until now, attempts to bring them back to the market have not been very successful. With the increasing importance of energy saving and environmental protection this might change. So far the main problem to build electric cars with acceptable performance is the low energy content of batteries in respect to its weight. This limits the driving range of cars to about 100 km. Also much time needed to recharge an empty battery, so it might be better to exchange the battery as a whole. So far the near term market might be limited to small cars (“city cars”). To overcome the above limitations, the so called hybrid car is under development. It uses a combination of an electric and a petrol engine. While the electric engine is sufficient for short and slow trips (city traffic), the petrol engine improves the range and (horse)power performance of the car. Nuclear power offers an excellent ratio between mass and power density. However because of system size, security reasons and costs such systems are confined to ships, submarines and space vehicles. Plans to build nuclear powered airplanes have been abandoned. Additionally to the military ships and air carriers there are also civil examples of nuclear powered freighters and icebreakers. However the future development in the civil sector seems to be uncertain. Electricity Production Electric energy is form of energy that can be transformed best into most other forms of energy. It is for example possible to transform it with very low loss into mechanical or heat energy. Moreover its market share in future seems to increase. Therefore electric energy systems can be used as a reference for the comparison of different energy systems. In this chapter the different principles of electric generation will be discussed first, then the typical features of generators will be evaluated. Most of nowadays electric power stations first transform the primary energy into mechanical energy (= rotation). Using electric generators the rotation is finally transformed into electric power. Dynamic Electric Conversion (Electric Generator) The technology of generators is well developed and is already existing for about 100 years. Generally in a generator a magnetic field generates electricity in rotating coils that are mounted on the generator's axis. Big generators deliver up to 1 GW of electric power and have a conversion rate of up to 99.5%. Also small generators that generate only a few kW of power have efficiency rates of more than 90%.
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