Generation Fuel Choices for Facility Resiliency

Author: Stephen Laslo, PE

The resiliency of a power system is partially defined by its ability to meet the building energy needs during long duration outages. Generally, diesel fuel would be considered more resilient. This is because it relies on no infrastructure outside the local facility. During certain disasters, the natural gas supply can become compromised by the added load or system damage. 

​With diesel, planners set goal runtime based on your system load, generator size and how much on site fuel clients can afford to store and maintain. Some planners never consider refueling as part of disaster recovery because few can predict the reliability of a supplier during these events. If a three-foot snow event hit parts of the country where this is uncommon, there exists the likelihood that a fuel truck could not reach the site after seventy-two (72) hours. If the same snow event occurred a northeast city, used to large snowfalls, a fuel truck could likely make a delivery within the seventy-two (72) hours. It becomes a regional analysis with many facets.

Not to say natural gas should be discounted as a fuel for resiliency projects, because it has distinct advantages. Natural gas systems do not have to consider on site storage. It is much cleaner.  Today’s cleaner low Sulphur diesel fuel can allow algae to grow within the tank if even the slightest amount of moisture migrates into the container. If the algae forms and the generator starts, it will immediately plug the injectors and foul the system. To prevent this an owner must use their fuel to turn it over or have a maintenance contract with a company that can monitor it and keep it clean.

A further consideration for fuel choice is the cost and size difference between diesel based and natural gas units. For the same engine displacement diesel based units can deliver more power. This is a direct result of the fuel characteristics. In general a natural gas unit will cost more and take up more space than a diesel unit of the same rating. This size and cost difference becomes more significant as the unit increases in power output rating.