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| 4. Advantages / Disadvantages about CNG and NGVS |
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What is CNG?
CNG is the abbreviation for Compressed Natural Gas. It is a natural product, which covers basically all gas hydrocarbon compounds that originate from the earth, and which can be combusted. Natural gas consists by volume of at least 85% methane as well as up to 10% of nitrogen and carbon dioxide. The rest is made up of gases like ethane, propane and butane. It belongs to the same group of organic resources as crude oil and coal. |
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| In principal, natural gas can be offered in two forms: |
- CNG (Compressed Natural Gas, stored at a pressure between 200 -240 bar)
- LNG (Liquid Natural Gas, stored at -164°C; this way, the volume can be reduced to 1/6000 of its original size)
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| Currently, only Compressed Natural Gas (CNG) is offered in Singapore. |
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| What is the difference between LPG and CNG? |
- CNG is basically composed of methane whereas LPG is a mixture of propane, butane and other chemicals.
- Another important difference from a physical point of view is that CNG does not liquefy under high pressure - it remains a gas, unless it is cooled down to at least - 164°C. LPG on the other hand becomes liquid when it is compressed or when it is cooled down (therefore the name "Liquefied Petroleum Gas").
- CNG directly comes from a gas field. The only process, which sometimes needs to be done, is filtering the gas. But usually, the gas can be used as a fuel right away after the compression process. LPG, however, is an artificial product. It is a mixture of the above-mentioned gases. Hence, these gases need to be blended, before they can be used as fuel.
- CNG has a greater part of Hydrogen and is therefore lighter than air (this attribute in fact makes CNG very safe: once there is a leak in the system, the gas will simply be released to the atmosphere). LPG on the other hand, is twice as heavy as air. This gas is usually a by-product which accumulates from the oil drilling as well as the refinement of oil.
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| Can an LPG car also be filled with CNG, or vice versa? |
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No, this is not possible. First, the different pressure levels make it impossible to fill CNG into an LPG tank. Since LPG is operated with a pressure of 5 - 15 bar and CNG is operating with a pressure of 220 bar, the gas cylinder might even burst. However, the filler plugs at the refilling stations have different standard sizes. It is therefore practically impossible to fill CNG into an LPG vehicle.
Secondly, both gases have different ignition points and calorific values. The electronic devices, which are part of the conversion kit, guarantee an optimal combustion for a specific type of gas. However, if a different gas was used, the combustion might not happen properly, or might even be suspended. |
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| When will the natural gas resources be exploited? |
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| The resources of crude oil are estimated to be exploited within this century. However, the natural gas fields are said to supply sufficient gas until the next century. Gas supply will therefore certainly last longer than the life expectancy of your current CNG car. |
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| How much CNG will my car consume? |
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| Example: A bivalent car with 1.6l displacement consumes about 5.3 kg CNG (equal to 5.8l) per 100 km, which costs about $8.00 (at 1.51 SGD per kg) for these 100 kilometers. Compared with a Petrol consumption of 7.1l, per 100 km, which triggers costs of about $13.51 (at 1.90 SGD per liter) for 100 kilometers, CNG is indeed the cheaper alternative. |
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Is CNG environmentally friendlier than other fuels?
Yes, it is. As CNG mainly consists of methane, the exhaust fumes of CNG basically consist of water vapours, Carbon Dioxide and some fractions of Carbon Monoxide. There are no other carbons or toxic particles in the exhaust fumes. It is therefore much more environmentally friendly than other fuels. Thanks to that, CNG vehicles fulfill all present emission standards worldwide (such as the European EURO 4 standard). They do not need any additional aids, such as catalytic converters, etc. |
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Is CNG Poisonous?
No, CNG is neither poisonous, nor does it contain toxic substances or other cancer-causing contents. |
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Is CNG odorised like LPG?
CNG in its pure form does not smell. However, for safety reasons, scents are mixed with the CNG. This makes it possible to notice whether there is a leak in the system. These strong-smelling scents are not hazardous. They can be smelt at a low concentration of CNG. That means, once the "Gas" can be smelled, the concentration is still too low to ignite. The scent is the same as your household gas. If this smell can be perceived, a certified car workshop should be visited, and the car should be checked for possible leaks. |
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Why should I use a NGV?
Prices of conventional fuels such as Petrol and Diesel are quite high, and it is foreseeable that these will rise even further. The prices for CNG, however, are much lower than that of Petrol and Diesel. Gas is therefore a cheap alternative fuel.
Further, the gas for Singapore is supplied by gas fields, which are located in nearby countries such as Malaysia and Indonesia. The transportation of gas is therefore quick and short. Thus, a continuous supply is guaranteed, and due to the vast resources, the prices for CNG in Singapore will stay low for a long time. |
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How long can I use the installed CNG gas conversion technology?
Usually, the lifetime of CNG kits lasts for many years, and you can use it as long as you use your car. However, please regularly visit the car workshop for routine maintenance. |
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Is the usage of CNG harmful for the engine?
No, the opposite is the case. The usage of CNG can extend the lifetime of the engine. This is due to the clean combustion of CNG and the fact that no carbon is generated during the combustion of CNG. That means that the engine and the oil in the engine are kept much cleaner if Petrol or Diesel were used. |
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How much CNG will my car consume?
Obviously, the fuel consumption of gas depends on the size of the engine. However, since 1 kg CNG has more energy (kj/kg) than 1 liter Petrol, the consumption of CNG is lower than that of Petrol under equal conditions.
Example: A bivalent car with 1.6l displacement consumes about 5.3 kg CNG (equal to 5.8l) per 100 km, which costs about $6.60 (at 1.25 SGD per kg) for these 100 kilometers. Compared with a Petrol consumption of 7.1l, per 100 km, which triggers costs of about $13.86 (at 1.95 SGD per liter) for 100 kilometers, CNG is indeed the cheaper alternative.
1 kg CNG = 1,1 litres Petrol (under 200 bar pressure) |
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What is the difference between bi-fuel and monofuel?
Cars, which run on Petrol and CNG, are called bi-fuel (or also bivalent) cars, whereas serial- produced Natural Gas Vehicles (NGV), which cannot run on Petrol, are called monofuel (or monovalent cars. Many car producers have already reacted to the new trend and do now offer serial produced CNG vehicles. Among them are Mercedes Benz, Fiat, Citroen, Peugeot, Opel, Renault, Volvo, VW, Honda and Ford.
In order to enjoy the vast benefits of CNG, one can purchase a brand new Natural Gas Vehicle. A much more simple way to get a CNG powered vehicle, however, is to simply convert the petrol car into a bi-fuel vehicle.
Almost all converted cars are bivalent cars. Converting a car does not mean to change the entire engine. It simply means that an additional system is added to the car. After the conversion, the car will additionally be equipped with a Gas cylinder, gas pipes and valves, and further an electronic sensor and control units.
In contrast to monofuel cars, bi-fuel cars provide a greater flexibility for the driver. As the original petrol engine remains, the driver can decide by himself whether he wants to drive with CNG or with Petrol. In areas, where the density of CNG filling stations is very low, the advantages of bi-fuel cars in contrast to monofuel cars become obvious. If the CNG gas tank is empty, the system automatically switches to Petrol, and keeps on driving - without any interruption. Moreover, due to the additional tank, bi-fuel cars can be driven longer distances without being refilled. |
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Can my car be converted into a NGV?
Almost every Petrol car can be converted to a bivalent car. It furthermore does not play a role, whether the engine usually needs unleaded or premium Petrol.
The conversion of carbureted vehicles is much faster and easier, since this kind of vehicle does not possess sophisticated electronic parts to regulate the engine and the combustion process.
In Singapore, however, most of the cars on the roads have modern cars with new ECUs. In an injection engine, the quantity of gas pumped into the engine is regulated electronically. This makes injection engines much more fuel-efficient, and reduces unnecessary emissions. However, since more electronics are involved, the conversion takes a longer time, and the conversion may for certain vehicles require additional electronic parts, such as a timing advance processor, an injector emulator and a lambda sensor emulator. And all these parts, of course, need to be fine-tuned to guarantee an optimal and efficient combustion and to keep emissions as low as possible. |
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I have a Diesel engine - can it be converted either?
Converting Diesel cars is not as easy as converting Petrol cars. There is a simple reason for that. The mechanism of Diesel cars is based on the principle of "self ignition". The combustion in Diesel engines is reached by mixing the Diesel fuel with hot air under a high pressure. Then, the fuel ignites automatically; an ignition spark is not required. (This is also the reason why a Diesel car should never be filled with ordinary Petrol). CNG, however, has a high ignition temperature (about 600°C). Diesel cars do not have sparks to initiate the combustion process. And the heat generated in a Diesel engine is not sufficient to ignite the air-gas mixture. Hence, if a Diesel engine should be converted to a CNG engine, holes have to be drilled into the engine block, and an additional spark plug system needs to be installed. This is very costly and requires much time. |
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Will I have to remove my Petrol tank?
No, the Petrol tank will be kept. The gas will be stored in an additional tank (cylinder). This cylinder is usually installed in the trunk of your car. But there are also other possibilities, e.g. installing the cylinder beneath the car. |
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Will my car have technical problems after the installation of the kit?
There is no reason to be concerned. Many conversions have already been successfully accomplished. One of our suppliers, Galileo has experience for over 17 years now, and so far, no information about greater damages has been reported. |
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Can the gas tank explode during accidents, or when the car heats up?
Generally speaking, a CNG gas tank is much more secure than a conventional Petrol tank. Petrol tanks are usually made of plastic, which is much less secure than a robust gas cylinder of pure steel. And even though the Petrol tank is made of plastic, only very few cars burn after an accident.
Further, once the pressure of the line from the gas cylinder to the engine exceeds a certain pressure, the valve at the cylinder will automatically shut. This way, maximum security is guaranteed, and no gas is able to evaporate. Even police cars drive on CNG in certain countries. |
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Is it possible to remove the CNG equipment after some time?
Yes, that is possible at any time. The car conversion kit just consists of some piping valves, cylinder, switches and the regulator. Everything can be uninstalled and removed completely. |
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Is it possible to install a second-hand car conversion kit?
This is not possible. A new conversion kit needs to be purchased for each car that is converted. Used conversion kits should not be used again - for safety reasons. |
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I still want to use ordinary Petrol. Is that possible after the conversion?
Yes. The gas-feature is added to your engine system, which means, your car will still be a Petrol car. However, this Petrol car can either be operated with Petrol OR gas. This is the great advantage. There will be a switch installed inside the car. So the driver can decide, whether he wants to drive with Petrol or gas - simply by pressing the button. By default, the car switches to CNG. When the cylinder has been depleted, it will switch to Petrol automatically. |
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Can I switch from Petrol to Gas while the vehicle is in operation?
The type of fuel can be changed, even while you are driving. There is no need to stop or to switch off the engine. Feel free to press the switch any time. |
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Will the switch from Petrol to Gas harm the engine?
No, absolutely not. Technical devices and sensors, which are installed in the car, will guarantee that the switch from Petrol to Gas or from Gas to Petrol will happen without any difficulties. |
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How can I know how much gas is left in the gas cylinder?
The new CNG - Petrol switch integrates a digital gauge. Similar to a Petrol gauge, this light indicator optically indicates how much gas is left in the cylinder. |
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Who is the supplier of the conversion kits?
The Italian company OMVL is a leading player in the Alternative Fuel Vehicles (AFV) sector, designing, manufacturing and marketing complete fueling systems for gas-propelled vehicles and for the conversion of engines from petrol to CNG and LPG. Established in 1980 at Argelato near Bologna, since 2001 OMVL has been part of the SIT Group, an Italian multinational specializing in safety, monitoring and control systems for domestic gas heating appliances and for Alternative Fuel Vehicles. The merger has given a further impulse to the internationalization of OMVL, which currently collaborates with the most important manufacturers of motor vehicles worldwide, including Volkswagen, Citroën, Ford and FIAT, selling to Europe (43%), the Americas (14%) and Australasia (43%). The company’s headquarters and manufacturing premises are now based in Pernumia (Padua), while commercial branches or production plants are located in Iran, Brazil and Argentina. |
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How many NGVs do already exist?
The CNG technology has already been on the market for many years. Some countries already have a huge number of CNG vehicles - with an increasing tendency. Currently, there are about 4,900,000 CNG cars worldwide.
Main Sources: (visit these sources to get even more information about the number of CNG cars worldwide). |
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- http://www.angva.org
- http://www.iangv.org/content/view/17/35/ |
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| There are still many other countries with CNG cars, such as UK, Spain, Poland, Sweden, Nigeria, Slovakia, Portugal, and many more. |
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What was the first car, which used gas as a fuel?
Interesting enough, the very first car in the world, which was created by Karl Benz, the ancestral father of today's global player "Mercedes Benz/Daimler Chrysler" was operated with gas (Ligroin).
And even famous Henry Ford experimented with (liquid) gas, that he manufactured by incinerating bio material.
However, all of these gases did not come out of the earth, but were somehow manufactured synthetically. |
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