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For on-site gen-set operations, which is better: Diesel or natural gas?

For situations where on-site power generation is needed – whether during normal operations or an emergency– which is the better fuel choice, natural gas or diesel?

This was an important question addressed during a Power Generation University course held the morning of Monday, Nov. 18 at POWERGEN International. The course instructor, Daniel Barbersek, is business development executive with Waukesha-Pearce Industries (WPI Inc.).

Barbersek told POWERGEN attendees that factors to be considered when making this decision include: the impact fuel type has on engine operation, gen-set performance, system reliability, code acceptance, and total cost of ownership.

He said that the growth of natural gas generators in the market is replacing some traditional diesel applications, and it is important to understand the different roles fuel choice and maintenance play in generator reliability.
Barbersek said 80% of the market for generators is standby power, to back up the grid. Of the remaining 20% of market share for non-standby applications, they are broken down by run hours, with less than 500 hours/year, 1,000 to 2,000 hours/year and more than 2,000 hours/year, with different technology choices available depending on this factor.

Why has use of natural gas grown for this application? Barbersek pointed out several limitations around diesel, including issues around sulfur and its removal and the need for regular quality testing and an active maintenance program. Fuel needs to be consumed within its storage life, or provision must be made to replace stale fuel with clean fuel.

An additional topic covered was the differences between rich and lean burn engine technology. A lean engine is a lot more efficient, Barbersek says.

He also discussed a bi-fuel arrangement, which would involve using a mix of diesel and natural gas for on-site gen-sets. Barbersek says this can be a good alternative approach, and the industry standard is 75% gas and 25% diesel.

Barbersek also discussed the fact that different gen-set technologies may be more compatible with different fuel types. So if you have an idea of a specific fuel type you want to use, you may need to choose your technology accordingly.

At the end of the day, what the companies that use these gen-sets need is performance, he said. They need this power to work consistently. And fuel concerns are one of the main topics that need to be researched.

Another important topic covered during this course was the reliability of natural gas in terms of supply availability.

Barbersek also covered the total cost of ownership for gen-sets using either of these fuel technologies and the effect demand response has on total cost of ownership for these two fuel types. As an example of how emergencies affect the choice of fuel for on-site power production, Barbersek gave the example of Hurricane Sandy. Many lessons were learned there that can be applied today, to save time and money … and headaches.