Compressed natural gas used with diesel for better economy

Fuel consumption is the biggest operational cost in any truck fleet, and ISUZU believes it has a solution for this problem, using a combination of Compressed Natural Gas and Diesel Dual Fuel (CNG-DDF).

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Automotive use of CNG is a proven technology - up to 14 million NGVs (Natural Gas Vehicles) operate in 80 countries worldwide.

ISUZU Motors South Africa (IMSAf) has been testing a fleet of CNG-DDF converted trucks during the past five years with proven reliability.

CNG & LPG fuels are different. While CNG consists of methane, LPG includes propane and butane. CNG is typically used as a substitute for petrol / diesel in automotive applications, while LPG is often used in industrial, refrigeration, agricultural and catering industries.

Unlike LPG, CNG is lighter than air. In case of leakage, CNG disperses quickly in the atmosphere with low risk, while LPG spreads on the ground and poses a high risk of ignition. CNG has less carbon so it produces lower amounts of carbon monoxide and carbon dioxide during combustion. Consequently, CNG is a better and safer option than LPG.

The current challenge in any fleet is ‘how green can we be’?

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The use of CNG has the following advantages:

  • Reduction in Carbon footprint - cleaner fuel - Natural Gas Vehicles (NGVs) emit 20-25% less greenhouse gases and virtually no toxic pollutants.
  • Reduction in Particulates.
  • Reduction in Engine noise thanks to natural gas’s smoother combustion.
  • Reduction in fuel consumption.
  • Reduction in fuel theft and adulteration.
  • Less engine carbon deposits = longer engine life.
  • Improved engine oil quality owing to a reduction of carbon emissions.

ISUZU CNG-DDF is easy to operate:

The diesel cycle engine remains in standard execution with 100% fallback to Diesel at any time.

  • Simply by pressing a button, it switches between Dual Fuel mode (Diesel/Gas mixture) and 100% Diesel mode.
  • It automatically reverts to 100% diesel mode when the natural gas cylinder is empty or when a fault is detected in the CNG system.
  • Quick gas filling time compared to lengthy charging times for electric trucks.
  • Driver training is still necessary.
  • Trip times & performance.

Engine performance and efficiency are maintained in Dual Fuel mode - engine torque and power remain practically the same. Trip times are unaffected. The engine works with Diesel and Natural Gas (CNG) simultaneously – a special engine control unit determines the optimal gas/diesel fuel mixture. With similar torque and power, trip times are unchanged.

Safety Rules:

  • CNG is lighter than air and will disperse harmlessly into the atmosphere - an odorant is added for safety and easy detection.
  • CNG has a narrow range of flammability - ignites at concentrations of between 5% and 15% (petrol = 1-8%).
  • Statistically proven safety record - superior to conventional fuels.
  • CNG is Non-Toxic.

The coastal price of diesel fuel is R21.91/litre – a diesel tank of 400 litres costs nearly R8 800. While Brent Crude hovers around 84 USD a barrel, the Middle East and European wars present weekly crises and the oil price is volatile. All of this means that fuel, and CNG in particular, should be a strategic - and not just a price – consideration.

The challenge for CNG is the distribution network. Municipalities are an ideal application from an environmental, fuel consumption, anti-theft and centralised refilling viewpoint. CNG is currently only available in the Gauteng region. The CNG gas cylinders mounted to a Dual Fuel truck add to the tare mass and reduces payload – GVM and GCM remain unchanged.

CNG gas cylinders need chassis space making the conversion to CNG-DDF more suited to long wheelbase models. The fact that the cylinders can be fitted as an option to 20 ISUZU long wheelbase models is a huge advantage for fleet replacement planning, ISUZU says.

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