Carbon fiber (carbonized fiber) is a material that until recently was used exclusively in the most advanced and expensive applications, such as astronautics, aviation, or Formula 1 racing. What connection could there be between activities optimizing logistics costs and the use of one of the most expensive materials in the world? There is a company that has successfully combined these seemingly contradictory elements.
The Hexagon Composites ASA group (based in Alesund, Norway) is the third-largest customer (in terms of material consumption) of carbon fiber manufacturers in the world. The first two are Boeing and Airbus. How is it that a little-known company from Norway buys such significant quantities of carbon fiber, and where is such a large amount of material used? The answer is simple – in applications for supplying and transporting natural gas.
Natural gas (CNG) is a mixture of gaseous hydrocarbons used mainly in industry and for home heating. In recent years, the use of CNG as a vehicle fuel (especially in public transport) has developed significantly. There are several important arguments defining the growing popularity of CNG. First and foremost is the price (about 50% of the price of diesel fuel) and a significant reduction in toxic substances emitted during natural gas combustion.
One of the most developed applications of CNG as a vehicle fuel is public transport. Mainly due to the lack of need to build an extensive supply infrastructure and pressure from city authorities regarding pollution restrictions in metropolitan centers, city buses became the first beneficiaries of natural gas use. One of the biggest challenges regarding tank installation was the emerging trend for low-floor buses. The lack of space in the lower part of the vehicle forced manufacturers to redesign tanks storing up to 1,500 liters of gas. Therefore, lightweight cylinders placed on the roof of buses, made mainly of carbon fiber, began to be used. Standard metal cylinders would be far too heavy.
The design of the cylinders proposed by Lincoln Composites and Raufoss Fuel Systems is entirely based on composite materials. The structure of the material and the design is durable enough to allow for up to 1050 bar to be applied to tanks based on the same technology! Such high pressure is mainly used in hydrogen transport. For CNG operating in buses, the standard working pressure is 200 bar.
One of the biggest differences in using so-called type 4 cylinders compared to standard metal ones is weight reduction. In this case, it is as much as 70% when using composite cylinders. This has a colossal impact on logistics and operating costs, for example, for a bus fleet. Another benefit is increased safety due to the safety margin assumed during cylinder production. Despite the maximum pressure that can be applied to the cylinder, which is 260 bar, the structure successfully withstands pressure on the order of 600 bar. The assumed safety margin is three times the standard operating value. Another argument in favor of composite cylinders is the lack of corrosion due to the use of non-metallic materials in their production.
The potential of natural gas as a fuel has been noticed not only by bus manufacturers. Recent years have seen very strong expansion among smaller vehicles. A precursor in the automotive market turned out to be Daimler AG, which was the first (for several years now) to use lightweight tanks made entirely of composite. The first model to receive the new type of fuel was the current generation Mercedes B-Class. The design of the vehicle equipped with 5 tanks of different sizes does not suffer from a loss of space in the passenger or cargo area (as happens with LPG installations used in Poland, for example). The sets were hidden in the car’s structure, so the only indicator of the use of a different fuel for an observer is the inscription on the car’s tailgate – NGT.
The range of a car operating only on CNG is about 300 km. Together with an additional 54-liter tank for unleaded gasoline, it allows reaching up to 1,000 km on a single refueling. Vehicles of this type achieved the greatest success in Sweden, where there is very strong state lobbying for energy sources alternative to crude oil. The proposal to use natural gas as a fuel is extremely attractive, especially for taxi drivers, who in this way receive a car that allows them to save about 50% of fuel costs while maintaining the practically unchanged character of their car. That is why the next vehicle to receive CNG tanks will be the “beloved” car of German taxi drivers – the Mercedes E-Class. Plans for the further future assume the installation of CNG technology also in the next generation of the Mercedes B-Class from 2012, which will be a platform for several different cars of similar size offered by Daimler AG.
The article comes from the magazine “Logistyka” 1/2011.