Wind chill of -20°. Yes, that’s Fahrenheit. So, what does a good Minnesotan do in this type of weather? Travel to the middle of Iowa in a blizzard, and drive to North Dakota where the wind chill is -40°, of course. Why in the world would any sane person do this in the middle of winter you ask? This is a good question, and one I’m still asking myself.
Those of us who live in the Midwest seem to approach the cold a bit differently than those who are fortunate enough to reside in milder, dare we say, warmer, parts of the country. When we venture outside, we put on an extra layer, warm boots, choppers, hand warmers, and a face mask. At that moment in time, we believe we can bear almost anything. We are invincible; therefore, we believe everybody and everything around us is also immune to the cold. Unfortunately, that is not always the case. As we know, some electrical equipment is happy being banished to the frozen tundra outside while other equipment does not function very well in the extreme cold.
Because electric utility transformers are typically under load, they are typically not negatively affected by the cold. In fact, because they are inherently heat producers, they actually prefer colder weather. Really, the only time in the winter they are unhappy is when they are buried alive in so much snow that they cannot dissipate heat. As long as you dig them out when the blizzard hits to allow for air circulation, they’ll still be happy.
Now, what about those generators that have to operate in colder climates? That’s another story. Typically, gen-sets are dormant until called upon to spring into action, so they are not consistent heat producers. They sit quietly without any load, and wait, wait, wait. Natural gas units do not experience as many ill effects from the cold, but diesel generators provide some challenges. Some grades of diesel fuel do not do well in cold temperature. And when your fuel source isn’t cooperating, your generator function is at risk.
How can we address this dilemma with diesel generators? There are several provisions that should be considered when you are counting on your generator to start at artic temperatures. First is to provide some external protection for your generator. Providing an exterior enclosure is always a good first step. Ideally, a heated walk-in enclosure is preferred, but even just a temperature-regulated enclosure is valuable. Here’s another hint: Make sure the heating equipment for the enclosure is circuited to a source that is live when the generator is off. This sounds obvious, but you would be surprised how often this is overlooked — and there is no live power source when the generator is dormant. Another thing to take into consideration is fuel grade. Number 2 Diesel does not like cold temperatures and often starts to gel in weather colder than 20° ABOVE Fahrenheit. This could inhibit free flow of fuel into the generator and either prohibit the generator from starting or limit the fuel flow to the gen-set. This is a common problem when the exterior generator has a sub base tank that sets directly on grade and experiences the bulk of the cold from the frozen ground. Number 1 Diesel and winter blend fuel are not impacted by the cold as much as a Number 2 diesel fuel and may be a more suitable choice for an exterior generator.
It is important to remember that different grades of fuel have different levels of energy output and burn at different rates. This will affect the quantity of fuel required for a desired run time and will have an impact on the efficiency of the equipment and the emissions. This, in turn, may affect some rebate programs and curtailing agreements. It is also worth noting that if the generator shares a common tank with other equipment, such as boilers, the other pieces of equipment also need to be specified for that particular fuel grade. Existing equipment may require retrofit of burners and fuel nozzle to address the pressure flow and liquid density.
If Number 1 diesel or a winter blend fuel is not feasible or practical, then tank heaters should be evaluated in addition to a temperature-regulated enclosure. Tank heaters should be used in conjunction with some method of “stirring” the fuel to assure the warmed fuel actually circulates in the tank. You should also be mindful of the piping to exterior fuel tanks. Exposed piping should be heat traced if there is a concern of pipes freezing. It is also prudent to monitor either the fuel temperature or the heating elements to know if or when the heating equipment stops working or if the fuel temperature goes outside the acceptable tolerance level.
There is no one specific solution for assurance of exterior diesel generator fuel flow issues. Each individual situation must evaluate the climate, the available fuel types, fuel cost, rebate programs, emission requirements, manufacturer’s recommendations, and facility protocol to weigh them together and be able to decide the best solution for each generator installation.
Next week’s temperature is predicted to vary between 27°F and -1°F, which will prove to make both me and some exterior generators unhappy. Maybe it’s a good time for a trip to South Dakota!