Natural gas as a fuel source can significantly reduce emissions and is more affordable than gasoline or diesel. CNG Energy Partners will assist your fleet in selecting the best solutions available today for compressed natural gas vehicle conversions, compressed natural gas vehicle conversions, natural gas fuel storage, bi-fuel vehicles system selection, natural-gas-powered buses and transit vehicles options, selecting technologies used in natural gas fueling systems, fleets converting their vehicles to this fuel source with bi-fuel or dual-fuel conversion systems. We can also help to build private, public-private, or all public access fueling infrastructure using the best technologies available today. Please give us a call to discuss your project today!
Light Duty Vehicle Conversions
Light duty vehicle fleets generally can be converted to CNG for rather inexpensive capital funding. Most of the conversion kits suitable for light duty vehicles are designed so that the vehicle can maintain operations in a bi-fuel mode, meaning that the engine can operate independently on either gasoline or CNG. This configuration gives the light duty vehicle operator the option to modify their schedule to refuel with CNG as needed or to continue to operate on the gasoline stored within the vehicle.
The introduction of CNG storage tanks on an existing light duty chassis is generally an action which takes useable space away from the owner/operator. Tank technology soon will be approved that will allow for irregular shaped tanks, but for now, only cylindrical tanks are approved.
Medium Duty Vehicle Conversions
Medium duty vehicle fleets generally are powered by an medium duty diesel engine. Standards for diesel engines have been more stringent since 2007 when particulate traps were introduced into the exhaust system and regeneration was added to vehicle operations. Diesel is a compression ignition engine system, meaning that the fuel is ignited when pressure inside the cylinder creates enough temperature to cause the diesel fuel to explode.
Conversion to CNG can most economically be made by installation of tanks and a dual fuel system in which simultaneous operation on both diesel and CNG is accomplished by using diesel compression to ignite the CNG. This mode allows operators to use CNG somewhat efficiently and to use diesel as a starter, low speed accelerant, and as a primary fuel when gas pressure is too low. By somewhat efficiently, we realize that the stop & go operation of delivery vehicles and of school buses will significantly diminish the economic savings of CNG when used in a dual fuel mode. Fleet owners can expect no more than 65% of their fuel use (and lower per gallon cost) to be CNG. This creates a smaller per gallon payback than with dedicated CNG but has the less expensive initial capital outlay.
Obtaining EPA Certification of the conversion and also of the emission levels for dual fuel is not likely since the exact quantity of diesel and CNG to be used by the engine is dependent upon the end use and operational cycles of the vehicle. However, there are more and more diesel engines being approved by the EPA in an Out of Useful Life (OUL) status, meaning that the engine has exceeded its established warranty by time and or mileage and therefore can be modified without diminishing the EPA emission requirements for the original engine year group. This Certificate of Conformity provides approval to change the fuel but not the emission standard and is applicable to engine models within that Engine Family. Dual fuel operates as a compression ignition system which can continue to run on diesel when CNG pressures are too low.
The EPA has also approved some conversion kits for engines that are considered Inside Useful Life (IUL) for obvious reasons. Here the engine can be converted to dual fuel CNG if such operations do not exceed the emission standards for that specific year of manufacture only. These require significantly more testing prior to approval by the EPA, reducing the number of available engine conversions to a select few. This too is dual fuel which operates as a compression ignition system which can continue to run on diesel when CNG pressures are too low.
Conversion to a dedicated system requires that the diesel engine be significantly modified to change from a compression ignition system to one of spark ignition. In the dedicated CNG mode, there is no diesel present to ignite the CNG so a spark system must be added to the engine to ignite the CNG. Because of the properties of CNG during ignition, the cylinder must be reshaped to ensure that there is an even flow of the explosion. All metals exposed to the cylinder ignition must be hardened to withstand the higher temperature of the process. This is a dedicated system which operates only on CNG; there is no other fuel available for that engine to run on.
As of Feb 2013 there are only three medium duty engines that meet the EPA standards for dedicated CNG; one by OEM and two by conversion from diesel. Cummins Westport is moving forward with the CNG version of their popular Cummins ISB engine for fielding in 2015. Current engine options are:
- The OEM Cummins Westport ISL-G dedicated CNG engine.
- The Mercedes 906 engine converted to CNG by Motori USA.
- The Detroit DT 466 engine converted to CNG also by Motori USA. At one time ESI was converting this engine (and the T444 engine) into the Phoenix dedicated CNG engine, but this process has been halted.
Crunching the math is necessary for each process to determine which is more beneficial to the fleet owner, keeping in mind the operational needs of the fleet and the location of CNG refueling stations. Dual fuel vehicles expect to achieve 60-80% CNG use on long haul operations while dedicated achieves 100% CNG use. The number and size of tanks becomes a range limiting factor for dedicated CNG vehicles.
Heavy Duty Vehicle Conversions
Heavy duty line haul vehicles require the power, torque and fuel economy of large diesel engines. There are several opportunities developing in the heavy duty engine lineup.
Cummins Westport will offer the ISX12-G engine in five tractor systems later in 2013.
Motori USA is currently undergoing tests of the Mercedes 4000 engine converted to a dedicated CNG mode.
Both of these engines use the lessons learned from their medium duty CNG engine predecessors. Both are capable of being the bridge engines for transportation.