Browse Publications Technical Papers 2011-24-0122
2011-09-11

Liquefied Natural Gas (LNG) as Fuel for Road Heavy Duty Vehicles Technologies and Standardization 2011-24-0122

Natural Gas Vehicle (NGV) engine technology is mainly based on a well-known and already established engine functioning principle, the Otto engine. The recent developments achieved and the OEMs push for this kind of technology clearly shows the confidence and reliability of this technology, especially when it comes to the use of compressed natural gas (CNG). For the above-mentioned reasons, the number of applications involving NGVs has increased worldwide.
Environmental and economic reasons, on the whole, have been the main drive for this diffusion. Natural Gas chemical properties are an irrefutable proof of the advanced behavior, environmentally speaking, of a fuel that emits less CO₂ (due to its carbon-hydrogen balance when compared to other fuels) and less NOx and PM. In many countries, favorable taxation schemes have helped the development and entrance into the market of the NGV technology, especially for the light-duty vehicles. Until now, practically no heavy-duty vehicles or lorries have taken advantage of this fuel, because of payload restrictions, and due to the cylinders weight required for a suitable range, an issue requested by specific commercial mission profiles.
Nevertheless, Liquefied Natural Gas (LNG) offers the possibility of using this fuel for heavy-duty road transport applications due to its higher energy density. It should be taken into account that a temperature of -162°C is required (at atmospheric pressure) to maintain the fuel in liquid state, therefore the main issue of this technology lies on the cryogenic tank installed on board with a thermal behavior control system and the board vaporizer required to feed the internal combustion engine (ICE). This aspect (on board cryogenic vessels) and some others like the refueling infrastructure still require some standardization work, aspect that is being developed at ISO level.
In this context a new interesting opportunity arises with regards to the refueling infrastructure, that is the L-CNG filling stations concept.
This application could be used by all types of natural gas vehicles since it's able to deliver both LNG and CNG.
The gas in compressed form in this case is obtained from a liquid cryogenic pump at 300 bar followed by a downstream vaporizer, which releases gas in compressed form at 200-250 bar. In this way, a reduced amount of energy is required, when compared to the usual filling stations operated by compressors to build up the CNG from the piped gas.

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