Diesel generators are designed to run on diesel fuel, but some businesses are exploring alternative fuels like natural gas or propane to reduce costs and emissions.
Diesel generators are not naturally compatible with gas, but some can be modified to run on a combination of diesel and gas (bi-fuel1).
Understanding the differences between diesel and gas generators, and the feasibility of conversion, helps determine the best power solution for your business.
What are the differences between a diesel generator and a gas generator in terms of fuel compatibility2?
Diesel and gas generators operate on different fuel systems and ignition methods. This affects their compatibility with other fuels and their overall performance.
Diesel generators rely on compression ignition, while gas generators use spark ignition, making them fundamentally different in design.
Key differences between diesel and gas generators:
| Factor | Diesel Generator | Gas Generator |
|---|---|---|
| Ignition Method | Compression ignition (air heats the fuel to ignite). | Spark ignition (spark plug ignites the fuel-air mixture). |
| Fuel Type | Diesel fuel with high energy density. | Natural gas, propane, or gasoline. |
| Fuel Efficiency | Higher energy density = better fuel efficiency. | Lower energy density = more fuel needed for the same output. |
| Maintenance Requirements | Requires less frequent maintenance due to slower engine wear. | More frequent maintenance due to carbon buildup and spark plug wear. |
| Startup Time | Fast startup, suitable for critical power needs. | Slightly longer startup due to gas supply lines and ignition. |
| Emissions | Higher NOx and particulate emissions. | Lower emissions, cleaner combustion. |
Why fuel compatibility matters:
Diesel generators are more fuel-efficient and have better load acceptance under heavy use. However, gas generators produce fewer emissions and are often more cost-effective where natural gas is readily available.
Can a diesel generator be converted to run on natural gas or propane?
Converting a diesel generator to run on gas is technically possible, but the process is complex and not always practical.
A diesel generator can be converted to a bi-fuel system, allowing it to run on a mix of diesel and natural gas.
How bi-fuel conversion works:
-
Gas Injection System:
A gas injection kit is installed to introduce natural gas or propane into the engine's air intake. -
Diesel and Gas Mixing:
The generator starts on diesel, and once the engine reaches operating temperature, gas is introduced. -
Controlled Combustion:
Diesel fuel ignites the air-gas mixture through compression, allowing the generator to run on up to 70% gas and 30% diesel. -
Automatic Switching:
If the gas supply is interrupted, the generator automatically switches back to 100% diesel operation.
Advantages of bi-fuel conversion:
| Benefit | Explanation |
|---|---|
| Lower Fuel Costs | Natural gas is often cheaper than diesel, reducing operating expenses. |
| Extended Runtime | Using gas and diesel together increases total available fuel capacity. |
| Reduced Emissions | Gas burns cleaner than diesel, reducing overall emissions. |
| Fuel Flexibility | The ability to switch between gas and diesel ensures reliability during fuel shortages. |
Limitations of conversion:
- Not all diesel engines are compatible with bi-fuel conversion.
- Conversion kits can be expensive, with costs ranging from $5,000 to $20,000 depending on the generator size.
- Bi-fuel systems are less efficient under high load conditions compared to pure diesel operation.
Practical example:
A 1000kVA Cummins generator converted to a bi-fuel system could reduce diesel consumption by up to 50%, saving approximately $500–$1,000 per month in fuel costs, depending on local gas and diesel prices.
What are the risks and challenges of using gas in a diesel generator?
Running a diesel generator on gas or converting it to bi-fuel operation comes with several risks and technical challenges.
Improper conversion or operation can cause engine damage, efficiency loss, and safety hazards.
Key risks and challenges:
| Risk/Challenge | Cause | Potential Consequence |
|---|---|---|
| Knocking and Pre-Ignition | Gas ignites before the piston reaches the optimal position. | Reduced engine efficiency, increased wear. |
| Incomplete Combustion | Poor gas-to-air mixture ratio. | Increased emissions, carbon buildup. |
| Lubrication Issues | Gas burns at a higher temperature than diesel. | Overheating and increased wear on piston rings. |
| Backfire and Explosion Risk | Improper gas mixture or ignition timing. | Equipment damage, safety hazard. |
| Warranty Void | Manufacturer warranties may not cover engine damage from gas conversion. | Loss of financial protection. |
Why gas ignition causes problems:
Diesel engines rely on compression ignition, but gas requires a spark to ignite. When gas is introduced, the compression ignition system may not burn the gas mixture completely, leading to engine knocking and reduced efficiency.
Safety considerations:
- Gas leakage can lead to fire or explosion risks.
- Improper installation of a gas injection kit can lead to backfire and damage to the engine.
- Overheating caused by incorrect gas mixture can cause long-term damage to engine components.
Conclusion
Diesel generators cannot run solely on gas, but they can be converted to bi-fuel operation using a gas injection system. While this can reduce fuel costs and emissions, the conversion process is expensive and introduces mechanical and operational challenges. Careful evaluation of generator size, load requirements, and fuel availability is essential before considering a bi-fuel conversion.
