Monday, April 26, 2010
It is estimated that over 600,000,000 passenger cars travel the streets and roads of the world today. Most of them use petrol or diesel for their source of power. But at the end of 20-th century engineers and scientists started to develop more alternative fuels for cars.
Innovative technology makes today’s automobiles cleaner and more fuel-efficient than ever. Ongoing advancements in fuels and technology will continue to drive future progress. Auto engineers have developed sophisticated emissions-control technology that is putting cleaner automobiles on the road everywhere. Catalytic converters use precious metals to reduce smog-forming emissions from cars. Automakers have dramatically reduced evaporative emissions with tighter gaskets, hoses and better gas tanks. Computers have revolutionized clean vehicle controls by precisely metering the fuel and air that go into the engine, reducing the smog-forming emissions coming out of the engine. And, a computer system called aeon-board diagnostics constantly monitors the performance of the vehicle to help keep clean technology working. Automakers are developing clean, fuel-efficient technologies that run on diverse fuels.
The most dramatic changes are occurring this century. Automakers have invested hugely in developing diverse automobiles that run on alternative fuels like clean diesel, biodiesel, ethanol, hydrogen, and compressed natural gas or that run on hybrid technology using both conventional combustion engines (gasoline or diesel) and electric engines. These advanced technology vehicles are being introduced for sale as quickly as possible. Because consumers, as well as different regions of the world, favor different technologies, automakers are developing a range of automobiles that run on different fuels.
Ethanol or Ethyl Alcohol can be made chemically from Petroleum or by the more traditional method of fermenting sugar derived from vegetable matter. In this case it is often known as “Bio-Ethanol”.
The main sources of sugar required to produce ethanol are fuel or energy crops, grown specifically for energy use and include cereals, sugar beet, sugar cane and maize. Obviously there is a possible conflict between the need to grown these crops for food and for fuels, and next generation processes to derive sugar by hydrolysis from waste straw, sawdust, grass and other cellulose sources are now being piloted. There is also ongoing research into the possible use of municipal solid wastes.
The main environmental benefit of bio-ethanol is that the CO2 generated when it is burned comes originally from the atmosphere. The plants used to make ethanol absorb CO2 as they grow, so the cycle of making and then burning bio-ethanol does not increase atmospheric CO2.
BioDiesel is a transport fuel oil made mainly from organic vegetable oils by a production process called trans-esterification. General feedstocks for such an oil are soybean or rapeseed.
Biodiesel can be used alone, or blended with petrodiesel. All modern diesel engines can run on up to 5% bio-diesel and higher concentrations up to 10% can be used in some vehicles, subject to limits set by the vehicle manufacturer.
In 2007, biodiesel production capacity was growing rapidly, with an average annual growth rate from 2002-06 of over 40%.
Battery Powered Electric Vehicles have been around in limited quantities for some time and have useful applications for inner city use because of their zero local emissions, but if the energy to recharge the batteries is generated using fossil fuels, there is no overall environmental advantage. In addition, the limited range provided by even the best current battery technology is a limiting factor in their usefulness for general use. Nevertheless, they have their place – especially where they can be recharged using electricity which is generated without using fossil-fuels – and the electric vehicle technologies that auto manufacturers have developed for battery-powered vehicles will provide the basis of future fuel cell powered vehicles.
CNG (Compressed Natural Gas) is composed primarily of methane. It is stored under pressure on the vehicle at pressures up to 250 bar (3600 pounds per square inch). CNG cylinders are manufactured to internationally approved standards and made from light, high strength composite materials.
There are three types of Natural Gas Vehicle: Dedicated, Bi-Fuel and Dual Fuel. Dedicated vehicles run on natural gas only.
Bi-Fuel vehicles operate on CNG whilst retaining the ability to use petrol as a reserve fuel. The engine can operate on either fuel but not on both simultaneously. The compression ratio of the engine must remain at a level suitable for petrol. Currently this type of engine is used almost exclusively on vehicles below 3,500kgs.
Dual Fuel engines are derived from diesel engines. A small amount of diesel is retained as a pilot source of ignition. The primary fuel Natural Gas, is mixed with the incoming air as the bulk fuel.
Because of its relatively high Hydrogen content it produces less CO2 (and more H2O) than Gasoline or Diesel which have a higher proportion of Carbon. It also burns at a lower temperature and so generates less NOx.
Two main types of hybrid-electric vehicles exist, and they have different advantages and different applications, but both have fuel efficiency advantages over conventional internal combustion engined vehicles.
Parallel hybrids can run simply on battery power when zero emissions are required – say in the city – and purely on their parallel internal combustion engine for higher speeds and/or longer distances. In this mode they can also recharge the battery for the next phase of battery operation. In addition they can usually use both power sources together to give additional acceleration, and this means that the internal combustion engine can be relatively small and low powered, and largely avoid inefficient “transient” operation, because of the boost provided by the battery power.
Series hybrids run solely on battery power in all conditions, with a relatively small internal combustion engine available to recharge the batteries when zero-emissions are not required and to act as a “range extender”.
Because the internal combustion engine is only driving a generator, it can run at a constant speed and reasonably constant load, which is very efficient.
6. Hydrogen Fuel Cell
The Fuel Cell is a means of converting the chemical energy in a fuel directly into electricity, very efficiently, without any burning, which is a wasteful process with undesirable side effects (like pollutants).
Hydrogen is often called the fuel of the future because it contains no Carbon (and therefore produces no CO2) and it can be made from water.
However there are considerable problems to be overcome:
• the amount of energy required to make it, by separating the Hydrogen and Oxygen in water,
• its highly explosive nature when mixed with oxygen
• its very low density (the lightest material in the universe!) and consequent low energy density
So it is likely to be some years before it becomes a serious contributor. Nevertheless, Auto manufacturers are already working hard on the technology to use Hydrogen in internal combustion engines, and in the longer term in fuel cells, which produce electricity directly from the fuel, without burning, making it more efficient and much cleaner than a combustion engine.
* Fuel Cells
The fuel cell principle has been known for many years but they only became usable devices thanks to the space race – NASA developed usable fuel cells to provide safe, clean efficient electricity generation in space craft and other organisations, including auto manufacturers, have further developed them for commercial use.
Although fuel cell vehicles (FCVs) are still an emerging technology and are not likely to be in mass production for some years yet, they are seen by many as the long term solution for personal transportation energy. Fuel cells have the potential to very significantly reduce energy use and pollution and also to reduce our dependence on fossil fuels.
Like series hybrids, FCVs operate solely on electric power, but in this case there is no need for a battery or an internal combustion engine as the fuel cell does the job of both, and it does so more efficiently.
FCVs are fuelled with hydrogen, either stored on board, under pressure or in liquefied form, or converted from hydrogen-rich fuels; such as methane (CNG) or methanol, using an onboard device called a “reformer.;
FCVs fuelled with pure hydrogen emit no pollutants; only water and heat; while those using hydrogen-rich fuels and a reformer produce only small amounts of pollutants.
So our future is not covered with CO2 after all. Toyota has released a new hybrid Prius. Chevrolet's electrical Volt reaches sales by end of the year and Honda is testing hydrogen fuel cell FCX Clarity. So, when it’s time to buy a car, do it the green way = the right way!
Henry Tiirik ja Martin Lapp 12B