Natural Gas vs. Diesel Generators

It’s only been a few years since the traditional logic for generators was that diesel meant inexpensive and reliable, but also noisy and messy. Natural gas meant quieter, cleaner and a little more expensive. Although in recent years, thanks to the advance in technology, it means that the difference between diesel generators and natural gas generators are not so clear cut.

The battle between the two different types of generators are that diesel generators are renowned for providing response, power and durability, while natural gas generators are more environmentally friendly. Although it’s known that the environmental point is true, in some cases a diesel generator is not as much the clear winner when it comes to power and output. Through many years of manufacturing and improved technology, natural gas generators can optimise the RPM of these engines, in order to make their response output similar to that of diesel generators.

When it comes to energy density, diesel has greater peak energy density than natural gas by more than three times. With this in mind, energy density is heavily affected by both the engine and fuel conditions. Therefore a poorly looked after diesel generator or one running on poor quality fuel will likely still outperform a natural gas generator, but most importantly, will not perform at its peak.

Diesel generators tend to have a ‘sweet spot’ of around 50-70% load and will usually accept 65% first step load (for example, a 100kva generator will only take 65 kva on its first step), with 80% being the recommended maximum for long-term optimal operation. Running them under a lighter load for a long period of time may lead to problems known as ‘wet stacking’. Wet stacking is when the engine sends unburned fuel and soot into the exhaust system leading to much lower usage efficiency.

Many businesses that run engines under light loads which often incorporate load banks to consume the excess energy wasted. This is a viable approach as it helps to reduce wet stacking, although it can waste a significant amount of fuel. Alternatively, those operators could increase the load on the generator to bypass wet stacking, or some operators may go as far as purchasing a natural gas generator as they have much lower loads than diesel generator sets.

(Bellwood Rewinds offer load bank testing as part of our comprehensive service that covers all things generator related).

Well, it used to be clear-cut between the two, with diesel generators being considerably less expensive than comparable natural gas generator models. If you’re looking for a competitive replacement for a diesel generator, we’d suggest only doing this when high kW’s are needed; power producers can create configurations made up of smaller engines combined to provide generators with the cumulative kW needed for significantly larger operations. Over the past few years however, natural gas suppliers have also been declaring their fuel prices as beneficial, but is this actually the case?

While the decrease in natural gas prices is definitely making them a more attractive option, plummeting oil prices are having exactly the same effect on diesel generator fuel. While we can’t make a prediction in this case, due to constantly fluctuating fuel prices, we can’t see natural gas generators directly competing in price with diesel generators anytime soon.

The handling of fuel between both of the generator types is also not so clear-cut. A range of variables should be accounted for, such as the situation and the need.

For natural gas generators, it is recommended that you supply to the generator through a pipeline to ensure safe delivery and less exposure to danger or exterior sources. Although as you can imagine, the trouble with this is natural disasters like earthquakes that disrupt earth can cause problems for the pipeline, often leading to supply interruptions requiring maintenance. If you’re situated in the United Kingdom, earthquakes are rare and the risk is also much lower. Although surprisingly, even some very serious weather conditions can disrupt gas supply lines such as tornadoes and hurricanes.

On the other hand, diesel generators are supplied by delivery, which of course has its strengths and weaknesses too. If a truck can access your site, then there are no problems or limits on delivery frequency. However, weather conditions can also disrupt the availability to deliver to some operators in rural locations. Additionally, diesel generators can also become contaminated with water, particulates and algae over time. But, thanks to major advances in technology, filtration systems are now available and can significantly reduce the effect and growth of any algae and unwanted particles clogging up your diesel generator.

There are some other minor factors to consider when determining which generator is the ‘best’ fit and, as always, your needs and situation factor into this also. Although, both types of generator industries are rapidly increasing their manufacturing and year-on-year are competing with each other to reduce their weaknesses. Despite this being said, new diesel generators are still ahead of the game and account for around 81% of the generator market, which is an absolutely astonishing figure.

Basically, it boils down to this: gas sets are much more suitable for base load running and CHP (combined heat and power), so it’s dependent on the needs. Also, if you’re looking for something environmentally friendly and would like a cleaner burning fuel, we do recommend a natural gas generator as this is no doubt the prominent strength of this generator type.