Dual-Fuel™ FAQs
- Q. How does the Dual-Fuel™ technology work?
- Q. How much will I save?
- Q. How / where can I obtain the gas?
- Q. How reliable is the product?
- Q. What is Genesis
- Q. What is the environmental impact of converting my vehicle?
- Q. Is the manufacturers warranty affected by installing this technology?
- Q. Can I convert my car?
- Q. How much does it cost?
- Q. What is the difference in price between natural gas and diesel?
- Q. What is the difference between LNG and CNG
A. Dual-Fuel™ Technology Introduction (PDF file: 332Kb)
Dual-Fuel™ technology enables a heavy-duty diesel engine to operate on a high proportion of natural gas. Firstly, a Dual-Fuel™ engine is a diesel engine, unchanged in its basic thermodynamic operation. However, with Dual-Fuel™, diesel combustion is used only to ignite a metered charge of natural gas and air. A small injection of diesel is made to ignite the gas and air. This is called a pilot injection. The pilot injection is delivered by the standard, un-modified diesel injection system fitted to the engine. Once ignited, the gas and air charge burns rapidly and cleanly. By using diesel pilot ignition and retaining the diesel’s high compression ratio, the gas combustion can be achieved at very lean air-fuel mixture ratios. Known as “lean-burn”, this delivers high efficiency and low NOx emissions. The high compression ratio of the diesel engine can be retained due to the high auto-ignition temperature of methane, the main constituent of natural gas. A diesel engine is the most efficient engine for road-transport. It is significantly more efficient than a spark-ignited engine due to:
- Higher compression ratio (higher compression pressure in the cylinder)
- Very lean-burn combustion (excess air combustion)
- No throttle to cause additional pumping work on the engine
The Dual-Fuel™ engine retains all of these attributes and achieves similar efficiency to the diesel engine – after all, it is still a diesel engine.
Methane, either as natural gas, or bio-gas (from waste or biomass decomposition) is an extremely clean and low-carbon fuel. Burning it in a Dual-Fuel™ engine replaces 50% to 80% of the diesel fuel. The result is lower emissions of NOx and diesel particulates with lower emissions of CO2.
Due to the high level of engine efficiency and high methane substitution, a Dual-Fuel™ engine can save over 20% CO2from the base diesel engine. This equates to over 25 tonnes of CO2saved per truck, per year. If bio-methane is used, the carbon-footprint is even further dramatically reduced.
Dual-Fuel™ technology has been focused on heavy-duty commercial transportation as it delivers a significant economic benefit in fuel-cost reduction in addition to its environmental benefits. Theoretically, Dual-Fuel™ technology can be applied to any size of diesel-cycle engine.
Dual-Fuel™ technology delivers the capability to utilize a widely available, low carbon, low emission alternative fuel – methane. The technology reduces the reliance on imported diesel fuel and increases the ability to efficiently and cleanly use liquid and gaseous bio-fuels. Dual-Fuel™ technology is available today.
A.
Dual-Fuel™ technology replaces 50% to 80% of the diesel with methane (usually supplied as natural gas). The cost saving is driven by the quantity of diesel saved and the price differential between gas and diesel.
Recent independent UK trials on the retro-fit Genesis system have concluded that an articulated regional distribution truck would save 7p/km, equating to £12,000 per year. This is based on the UK price differential of diesel and natural gas.
Our technology operates across the world - see how much you can save in your market
Q. How / where can I obtain the gas?
A. Gas is widely available. Dual-Fuel™ technology uses natural gas, which is the same gas that is supplied domestically and industrially via national grid systems. To supply compressed natural gas (CNG), a compressor station can be installed, feeding from the national gas grid, in most locations. Nationally, there are commercial organizations that will set-up and supply CNG. Alternatively, compressor stations are commercially available and can be installed and operated by the end-user for in-house supply.
Natural gas can also be used (liquefied natural gas LNG), not to be confused with LPG (liquefied petroleum gas), which can be delivered and stored at any location. LNG is becoming the method of energy-import into many countries, delivering gas from many of the world’s abundant sources. LNG makes an ideal road-fuel due to its relatively high energy density. LNG supply is limited to a small, but growing, group of independents, energy companies and industrial gases companies.
Care must be taken with the composition of the LNG. Ideally, the LNG will have a methane number >90 Mn and will have a low percentage of heavier hydrocarbons such as ethane, propane and butane.
Dual-Fuel™ technology has no problems burning bio-gas, so long as the methane content is high enough. Bio-gas can be harvested from land-fill waste, sewerage waste, animal waste, biomass or bio-digesters and liquefied. The liquefaction process should clean and refine the end-product, usually resulting in a high purity methane. A growing number of commercial organizations are producing bio-gas. Bio-gas has the highest energy yield per hectare/acre of any bio-mass derived bio-fuel and is therefore extremely attractive. Burning waste-derived bio-gas is an exceptionally environmentally friendly route to reduce greenhouse gases. Overall, the availability of bio-methane will increase dramatically. If you are an organization that produces or manages organic waste, why not use it to produce methane to power your fleet for Dual-Fuel™ trucks?
In most developed countries, the national government offers fiscal measures to encourage and subsidise the establishment of natural gas and biogas infrastructure. Visit you government's websites to find out what incentives are available.
Q. How reliable is the product?
A.
A Dual-Fuel™ truck is like any other diesel truck; so long as it is well maintained and given the correct fuel it will operate without issue. A Dual-Fuel™ engine is a diesel engine that can burn a cleaner fuel – methane. The combustion process, in-cylinder pressures, efficiency and heat rejection are all very similar to that of a basic diesel engine. Therefore, there is no increased mechanical or thermal stress on the engine. As the efficiency is similar, the heat rejected to the engine’s cooling system is similar and there is no additional stress placed on this system and there is no requirement to change the cooling system. Overall, the diesel engine is unchanged and responds as such.
This has been proven in the field. In the past several years, over 1,700 Dual-Fuel™ vehicles have covered an estimated 500,000,000 kilometers on three continents. Several operators have Dual-Fuel™ that have completed more than a million miles of running.
Unlike diesel fuel, which is controlled by national standards (BS, ISO etc), gas properties can vary depending upon its constituents. Most natural gas is mainly methane, but lower levels of ethane and propane and larger molecules are present. Methane has a much higher auto-ignition temperature than diesel and resists compression ignition. However, larger hydrocarbons have more of a tendency to auto-ignite and their presence can cause combustion "knock". This is the result of auto-ignition of the gas-air charge and can be heard as a sharp "knocking" noise. This is not good for the engine and if left unchecked can cause damage. Whilst a Dual-Fuel™ engine is tuned to accommodate a wide range of gas properties, there are instances where poor management of stored gas, or issues with gas supply can lead to knock. As a countermeasure to this situation, Dual-Fuel™ engines are fitted with a knock sensor that returns the engine to normal diesel operation if knock is detected, as a result of poor gas quality. Fundamentally, like any engine, the Dual-Fuel™ needs the right fuel. Correctly supplied and managed, there are no issues. Nobody would expect to run a Ferrari on low-grade gasoline, so there’s no difference here.
Research conducted in the USA and jointly published by Caterpillar and CAP concludes that running in Dual-Fuel™ mode can improve engine life and lengthen oil change intervals. Back-to-back tests were carried out running diesel and Dual-Fuel™ on the same engine. The engine lube-oil was analysed for metal and additive content, indicating sources of engine wear and additive depletion. The tests found less iron content and less additive depletion in the lube-oil from the Dual-Fuel™ engine.
The conclusion is shown below, with the website address to the US Society of Automobile Engineers (SAE):
http://commercialvehicle.sae.org/
The mechanism which could be attributed to this reduction in engine wear is the production of soot (hard carbon). As a Dual-Fuel™ engine burns much less diesel, much less soot is produced. It is this soot, which finds its way into the lube oil, that is the source of much engine wear as it acts like a grinding paste when mixed with the oil. Whilst no further exhaustive testing has been carried out in the field, it is clear that Dual-Fuel™ does not actually harm the engine. In the absence of exhaustive and expensive field testing, Clean Air Power does not advocate extended oil change intervals for Dual-Fuel™ engines, but the evidence suggests that running Dual-Fuel™, benefits the engine.
A.
Genesis is a retro-fit Dual-Fuel™ system that enables the conversion of Euro 5 Volvo FM13 tractor unit and Euro 3 specification Mercedes Axor tractor units to operate on diesel and natural gas.
Engine System:
The Dual-Fuel™ system is fitted to the engine and comprises of a gas-air injection and mixing device, a turbo-boost control valve and a an electronic Dual-Fuel™ control unit. These engine components are based on the same components that have been developed and certified on Dual-Fuel™ Caterpillar engines that are currently operating in the UK, USA, Australian and South America. The system is simplified and robust. Fitting the system requires absolutely no change to the internals of the engine and only minor modifications to the air inlet piping and the addition of the Dual-Fuel™ ECU and electrical harness.
The electronic control system takes the torque demand of the engine and processes this information to calculate the correct gas injection quantity and reduced diesel quantity. The diesel injection is now used only to ignite the gas mixture. At no point is the diesel injection increased over the baseline diesel tune. Air-fuel ratio is controlled by fuel injection and boost pressure. Boost pressure is controlled by the by-pass valve system via closed-loop-feedback.
Diesel performance and driveability is maintained over most conditions. From extensive customer trials, driver acceptance was high.
Vehicle System:
Gas containment is fitted to the vehicle. Gas can be stored either as compressed natural gas (CNG) or liquefied natural gas (LNG). CNG is stored in an array of 6 steel tanks arranged in two sets of three attached to the chassis. LNG is stored as a liquid at around minus 160 °C in a stainless-steel vacuum tank, mounted to the chassis. Systems to regulate and filter the gas are also fitted that deliver gas, at around 6 bar (90 psi) to the injectors.
The gas containment system is fitted with safety systems which include electronic shut-off valves, inertia shut-off valves and manual shut-off valves. Natural gas is inherently safe and clean. Contrary to uninformed public opinion, it is difficult to ignite, having a higher ignition temperature than diesel and gasoline and a very narrow flammable air-fuel ratio band. Natural gas is much lighter than air, so it disperses safely outside and does not pool to form dangerous invisible vapour clouds – as does gasoline and LPG.
Genesis is a solution to reduce transport fuel costs and reduce CO2 emission. Natural gas is cleaner and lower cost than diesel. It is the lowest carbon fuel of any fuel (except hydrogen). Therefore, the more you burn instead of diesel, the more money you save and the less CO2 is put into the atmosphere. Genesis has shown fuel cost reductions of 7p/km, extrapolated to £12,000 per year per truck. This, with an additional saving of 8.4 tonnes of CO2 makes it a worthwhile choice for both the operator and the environment.
For further information or to arrange a trial of a Genesis vehicle, please contact Steve Lymer via the standard enquiry form.
Q. What is the environmental impact of converting my vehicle?
A. If you are operating a Heavy Commercial vehicle then converting this will have a positive effect on the environment to the extent each Dual-Fuel™ truck saves almost 9 tonnes of CO2/year being dispersed into the atmosphere or the equivalent of removing 10 cars off the road.
Q. Is the manufacturer's warranty affected by installing this technology?
A. The manufacturer's warranty is not affected by installing the technology, except where a failure to the manufacturer's vehicle occurs that is directly attributable to an installation failure. The installation carries its own warranty covering manufacturing or material defect failures.
However, operators are recommended to confirm the warranty arrangements with their dealer
A.
Theoretically, any diesel engine can be converted to Dual-Fuel™. However, Clean Air Power offers fully engineered conversions for heavy trucks. Each conversion has undergone extensive development, requiring significant engineering.
Please contact us for further information.
Currently, the cost of development and components does not allow for an economic solution for cars as system payback times would be too long.
As the market develops and production volumes increase, we hope to be able to offer dual fuel conversions for smaller vehicles.
A. The cost of a Dual-Fuel™ Installation is dependent upon a number of factors;
- Make & Model of vehicle
- Specification of chassis
- Type of Gas containment required
- Amount of containment required
- Final customer specification of vehicle.
Q. What is the difference in price between natural gas and diesel?
A. Both the price of Natural Gas and Diesel vary according to economic trends worldwide therefore it is difficult to be specific at any moment in time, however as a guide, during the past decade the differential between NG and diesel has been in the region of 35%.
Q. What is the difference between LNG and CNG
A. Natural gas can be supplied and contained on the vehicle in one of two states:
1. Compressed natural gas – CNG
2. Liquefied natural gas – LNG
CNG
Compressed natural gas is usually gas with is taken from the national supply grid (at relatively low pressure) and compressed to 200 to 250 bar (200 to 250 times atmospheric pressure – 3000 to 3500 psi) by a gas compressor. The gas is still in a gaseous state, but held at these high pressures and contained in a strong, safe and certified pressure vessel; either a storage tank or an on-board fuel tank.
As the gas is compressed, it picks up oil and contaminants from the lubrication within the compressor. Therefore, this contamination must be reduced as, over time, it can deposit within the injection system, forming hard “lacquers” which affect the performance of the injectors, or lead to failure. Clean Air Power produces gas filters which remove most of this contaminant. It is recommended that filtration is used to protect and extend the life of the injection system. This is no different from the filtration requirements of diesel and gasoline in traditional applications.
LNG
The most efficient way to transport gas over distances exceeding approximately 3000km is by ship in a liquefied state. Hence, a significant and growing proportion of imported gas is coming via LNG tanker vessels. This is part of a growing global energy economy and represents a safe and secure supply of natural gas from multiple, abundant sources throughout the world
Natural gas, which is mainly methane, is a liquid at minus 162 degrees centigrade. Therefore, a liquefaction plant refrigerates natural gas down to this temperature, whereupon it liquefies. As it cools, heavier hydrocarbons and impurities liquefy earlier and can be taken off, leaving a pure, clean methane-rich LNG at the end of the process. The resulting LNG is stored or transported in insulated or cryogenic refrigerated containers to the end users. This LNG can be either vaporised and fed into the national grid network, or transported as LNG to other users, such as road transport, where it is an ideal road fuel.
As a liquid, LNG has over twice the energy density of CNG and can therefore provide increased vehicle range for a given stored volume.
LNG is a very "dry" and "clean" gas, containing very little oil content. All pintle-type gas injectors require a certain amount of oil content to lubricate the injector seat metal-to-metal contact to avoid catastrophic wear. Hence, almost all injectors that operate well on CNG, fail due to accelerated wear when operated on LNG. Due to the unique and patented design of Clean Air Power's gas injectors, both CNG and LNG source gas can be used. Most of Clean Air Power's 1,700 in-field vehicles operate on LNG, using these injectors.
Clean Air Power vehicles can store LNG or CNG. The choice of fuel depends on the customer's requirements or preferences. As part of the customer support process, Clean Air Power is happy to advise and assist customers in their selection of the most appropriate gas storage medium. Please contact us using the enquiry form:
On Dual-Fuel™ vehicles, CNG or LNG is heated and regulated so that a controlled flow of gas at a pressure of approximately 6 bar is fed to the gas injection system. The Dual-Fuel™ system itself operates fine on either gas medium.