Natural gas vehicles have performance characteristics (power and torque) similar to diesel and gasoline vehicles. Despite its lower energy density, using natural gas results in marginally higher equivalent fuel consumption. When it comes to bi-fuel vehicles, these typically rely on gasoline for their start up cycle, but can be switched over to full natural gas operation.
In North America, Cummins Westport (CWI) is the leader in producing engines that operate 100 per cent on natural gas – compressed (CNG), liquefied (LNG) or renewable (RNG). At present, CWI has over 80,000 natural gas engines in service worldwide. These include 6 to 12 litre applications in school bus, transit and truck markets. CWI engines are based on Cummins diesel engines platforms, built to match their performance and durability.
Natural gas and diesel blending technologies allow for the use of compression ignition rather than spark ignition. There are a range of technologies used that are broken down into two distinct types. The first is a high pressure injection process, such as the Westport High Pressure Direct Injection technologies. The second type is a low pressure injection technology. In the case of high pressure injection, the objective is to limit diesel use to a pilot ignition source – eliminating the need for spark plugs – with direct substitution of diesel throughout the combustion cycle. The advantage of this technology is that it allows natural gas to match diesel efficiency.
Low pressure blending technologies cannot displace the same proportion of diesel fuel and therefore will run on diesel for a larger portion of operations. Experience with blending technologies for on road vehicles is somewhat varied, with individual developers claiming a range of performance. As blending technologies do not operate as natural gas only vehicles, there are some advantages that come from the ability to operate on two fuels. These technologies may be appealing for fleet owners that may need more fuel flexibility or that are not looking to replace vehicles, but to extend their use while gaining environmental and cost improvements resulting from partial use of natural gas as a fuel.
The following list includes links to developers of fuel blending technologies. Contact developers directly to learn more about the performance improvements that are specific to their particular fleet applications.
Natural gas is a promising fuel option for Canada’s marine sector. All of the technologies needed to use natural gas as a marine fuel are proven and commercially available.
Vessels operating in a number of regions around the world need to have flexibility in the kind of fuel that can be used by their vessels. As a result dual and multi fuel technologies are frequently used. Adding natural gas to the list of useable marine fuels has resulted in significant development of both dedicated natural gas and dual fuel engines.
Most marine engine manufacturers have opted for blending technologies similar to those used in on road engines. These engines will rely on a petroleum based fuel as a pilot or ignition source and will typically have the ability to run multiple fuels. At present, a limited number of dedicated natural gas engines are currently available in the marine market.
Experience in the marine sector shows the performance of natural gas engines is equivalent to petroleum based fuels. Some marine vessels use a direct drive, however electric propulsion is quite common with combustion engines used as generators. This means that most marine applications focus on kilowatt hours of generation per volume of fuel required, rather than in litres per 100 kilometers travelled as key measures of performance and efficiency.
Natural gas is also a promising fuel for rail applications.
Current generation locomotives can be converted to use natural gas as a fuel, using diesel as a pilot or ignition source. Similar performance characteristics, as were noticed with on road vehicles, have been observed with both high and low pressure injection technologies. It is important to note that locomotive conversions are not the same as on road engine conversions. High pressure direct injection has been used in conversions with favourable results.
In North America two original equipment manufacturers provide all new and repowered locomotive engines. General Electric has developed a natural gas locomotive package which has been made available to the market. Progress Rail, a Caterpillar company has also developed a natural gas version of its locomotive engines. In the case of Progress Rail, the engine technology shares a number of similar characteristics with Caterpillar’s heavy mine haul tuck natural gas engine.
Off Road vehicles such as mining trucks are ideally suited for LNG because of their large fuel use and the environmental and economic benefits natural gas offers. Natural gas conversions for off road applications have been limited to a small number of applications. At the largest end of the spectrum, mine haul trucks have attracted a great deal of attention. Similarly, new emissions regulations for off-road vehicles (United States Environmental Protection Agency Tier 4 requirements) make natural gas an appealing compliance option.
Heavy mine haul trucks have been leading this industry segment. With large volumes of fuel used, the mining industry is interested in the potential for fuel cost and emissions reductions.
Natural gas as a transportation fuel is typically 10 to 20 per cent less expensive than diesel and gasoline mainly due to the lower commodity cost of natural gas.
Understanding range and operating time for natural gas powered vehicles is about energy density. If compressed natural gas (CNG) is being used, roughly four times the fuel storage volume is required and if liquefied natural gas (LNG) is being used roughly twice as much volume is required. In practical terms, this forces fleets to think about the way vehicles are used, where additional fuel can be stored and how frequently refueling might be needed.
For example, transit busses using natural gas can operate for a full day with on-board fuel and long haul transport trucks can be equipped with CNG tanks that give them a range of 1,200 kilometres. Opting for less on board storage and more frequent refueling can reduce up-front costs and ultimately improve payback. Having the appropriate range for operational needs is what fleets should strive to accomplish.
LNG has also been used for on road transportation, but longer term experience is informed by marine applications, wherein tankers have used boil off gas to fuel their engines. When it comes to on road applications, there are significant range advantages that come with the use of LNG. Opting for larger tanks to accommodate LNG can be a cost effective way to increase range and reduce time associated with refueling. For rail and marine applications this allows for another aspect in determining payback opportunities. By switching to natural gas the fleet has an opportunity to rethink its fueling supply and can potentially find other savings.
Estimating Payback Opportunities
To calculate payback, consider the following:
- Vehicle type to be converted or replaced
- Understanding the options for on road vehicles is dependent on available new vehicles and the desire to use aftermarket technologies. The two biggest vehicle costs will be engine upgrade and fuel storage.
- Understanding the options for marine vehicles will depend on fleet requirements.
- Understanding the options for rail locomotives depend on the options for complying with new emissions regulations. As engine modifications are being contemplated, the potential for benefits increase.
- Understanding the options for off road vehicles will be tied to available refueling options as well as public pressure to reduce emissions in urban areas.
- Anticipated fuel consumption
- Once a vehicle owner has decided on the vehicles that will be converted or replaced, it becomes easier to anticipate fuel consumption.
- Knowing how much fuel is required, will impact on board fuel and refueling requirements which will have an impact on costs.
- Knowing the type of natural gas – LNG or CNG – that will be used will also impact fuel consumption, on board storage and refueling patterns.
- Refueling scenarios
- Finding the right fit in fuel suppliers can have a significant impact on the success of a fleet fuel switch. An important rule of thumb is that the greater the volume of fuel that a fleet uses, the greater the number of options.
- Public and semi-public on road refueling is limited, with a few options across Canada.
- Marine and rail refueling options at present are open for discussion, which may have a significant favourable impact for early adopters. Purpose built refueling is the norm, requiring partnerships with fuel providers.
- Facility upgrades or modification
- Ensuring vehicle storage and maintenance facilities meet the requirements for gaseous fuel is an important consideration.
- These additional costs must be well understood and must be included in any payback scenario.