Bus NGV - ©20minutes-F.Brenon

In a world where the energy transition is expanding and ecological and economic awareness is growing, new measures are being taken in the automotive field to find alternative solutions to the extremely polluting gases of this industry. NGV (Natural Gas for Vehicles) are considered the most efficient alternative to conventional fuels (diesel, gasoline, ...) and are used mainly for buses, trucks and garbage trucks.

The market of NGV buses (Natural Gas for Vehicles)

NGV (or BioNGV) is becoming more and more important in the busses, trucks and tippers storage.
Natural Gas for Vehicles can come in two different forms: in a gaseous form, called CNG (Compressed Natural Gas) and in a liquid form, called LNG (Liquefied Natural Gas). Even though their form is different, CNG and LNG have the same purpose. Biogas is also part of these natural gases. They are considered as biofuels. This means that if a bus, truck or other vehicle is running on NGV, it also has a tank for conventional fuel. If the natural gas tank runs out of fuel, then the gaseous fuel (gasoline or diesel) will take over from there. A normal vehicle can run on NGV only by installing a specially designed tank.

The economical as well as the ecological aspect of Natural Gas for Vehicles allow it to know an important growth within the different collectivities (mainly concerning the "city buses" and garbage trucks) as well as in the sector of the heavy vehicles. Indeed, it is a substitute fuel designed to be used for urban vehicles, reducing air pollution and by extension the impact of transport on the environment.
With a composition mainly based on methane (CH4) and a single carbon atom (C), NGV is the cleanest and least polluting hydrocarbon that exists for this type of vehicle. As a comparison, the light hydrocarbons we know today like propane and butane are composed of 3 carbon atoms. For gasoline or diesel, there are up to ten carbon atoms, which makes them relatively polluting gases.

natural gas extraction

This natural fuel can be created from two different methods. Firstly, we find a rather usual technique: by extraction via natural deposits underground. Following this extraction by drilling and pumping the gas, it can be purified in order to be transported to its final destination (transport via pipelines or methane tankers). The second process that can be used to obtain natural gas for vehicles is through a methanization technique. It consists in a fermentation of waste products (vegetable, sanitary or food) followed by a mixing and a precise filtering of these, which creates the totally biodegradable gas that is the BioGNV.

Composed out of methane, it is a natural gas which we have all already been confronted with in our daily life because it is the same gas used to warm our houses or for our stoves. Its use is simply diverted and modified to be used as fuel.

cooking gas

More and more manufacturers and collectivities tend to invest in and use natural gas vehicles to try to stop the increase of air pollution. Actually, this fuel is known to emit 20% less CO2 (carbon dioxide) than other energies.

Regarding this energy transition, there are standards such as the Euro 6 anti-pollution standard designed to limit harmful gas emissions and the carbon footprint of the mobility industry. This is why it is essential to encourage the use of renewable energies rather than polluting fossil fuels.
According to studies by the International Gas Union, natural gas (NGV) is a fuel that has been growing at a rate of almost 20% per year for the past 10 years around the world.

energy transition

The advantages

The positive impact on the environment and the reduction of toxic gas emissions produced by natural gas for vehicles are not the only advantages that can be identified with its use.
In addition to being almost non-polluting, NGV vehicles have a multitude of other advantages.
First and foremost, buses and other NGV vehicles are quieter due to the very slow combustion of gas, they are also more efficient. In addition, they have a greater autonomy thanks to the bi-fuel system (gasoline or diesel taking over when the tank is empty). According to the drivers, the comfort and smoothness of driving are notable compared to the fuels usually used.
No toxic smoke or fine particles are emitted when using NGVs.

The last major advantage in the use of natural gas concerns the economic aspect. The use of natural fuel in the mobility sector extends the life of the exhaust pipes of buses by up to 3 times. Also the engine degrades much less quickly and its lifetime is multiplied by 2. This is possible thanks to the gaseous state of NGVs, which avoids all difficulties that can occur with fuels in liquid state, such as potential mixing with the engine oil. The risk for the engine is thus considerably reduced.

Gas detection in NGV bus depots

Driving on bi-fuel means taking twice the risk. Indeed, it is necessary to prevent new risks linked to natural gases and to store the equipped vehicles.

ATEX standards to be respected

This type of fuel is nevertheless dangerous in terms of storage, as it is a flammable and explosive substance. This is why it is important to determine which regulations are to be taken into account. In this case, the ATEX regulation (ATmosphères EXplosives) is essential for everyone’s safety. This standard defines the areas where specific safety devices must be installed and the means of prevention in question.
For this field of activity, the ATEX standards apply to NGV storage stations but also to maintenance workshops in certain cases.

ATEX standards

As a reminder, the ATEX reglementation includes different categories. There are areas with dust (ATEX 20, 21 and 22) as well as areas with gas or vapor; and it is by this category NGV buses depots are concerned. It is divided into 3 categories (1, 2 and 3):

  • Zone 0: Area containing explosive gas/air (or dust) mixture permanently or for a long time
  • Zone 1: Area in which an explosive gas/air (or dust) mixture is likely to occur in normal plant operation (occasional risk)
  • Zone 2: Area in which an explosive gas/air (or dust) mixture is not likely to occur in normal plant operation (equipment malfunction)

Once the area has been determined, it must be delimited by clear signals as well as by specific facilities such as ventilation, one or more gas detectors or emergency escape equipment.

Other standards are imperative and essential to follow such as the ICPE regulation ( Classified Installations for the Protection of the Environment) which allows, thanks to inspections of equipment and others, to prevent risks to local residents while protecting and preserving biodiversity.

Gas detection and preventive measures

When the ATEX zone is defined, the person in charge of the establishment concerned must take certain necessary measures:

As previously mentioned, measures directly related to the storage of natural gas buses must be implemented, such as the installation of a gas detection system. This system will warn all the teams of a failure (gas leak, fire start, ...). In order to do this, there are different types of detectors to monitor temperature changes, gas leaks, pressure, gas concentration rates (carbon monoxide, natural gas).

Flame and gas detection devices such as QUASAR 900 open path, Searchline Excel or specific gas detectors such as the OLCT100, GD10P or SearchPoint Optima Plus for CH4 detection are recommended.

Quasar 900 open path

Finally, the ECE R110 European regulation stipulates that it is imperative to perform periodic inspections on the components of NGV vehicles. The vehicle's compressed gas tanks must be checked every 4 years and replaced every 20 years.