There is an age-old debate on what is better – a single, large generator set or paralleling multiple, smaller generator sets. There are good arguments on both sides.
- efficient operation through cycling gensets off-line based on load
- easier installation
Pro Single Unit:
- decreased complexity – no paralleling equipment need
- increased efficiency at higher loads
- simplified maintenance
Before the question can be truly answered, you need to consider specifics of you or your customer’s installation and requirements. There are a number of factors to consider, including:
- physical installation requirements
- basic site requirements – size of critical loads, load profile
- required reliability and redundancy requirements
- maintenance considerations
- owning & operating costs
- controls complexity
Suppose you have a facility with a load requirement of 2 MW. What is the best method to provide generator set power – a single 2 MW unit, two 1 MW units, four 500 kW units, forty 50 kW units? (I think we can rule the last one out.) Let’s take a look at one of the factors above – physical installation requirements. The larger generator sets typically have a higher power density. Not including working clearance around the generator sets, the total footprint of each option is roughly:
1 x 2 MW genset: 164 sq. ft.
2 x 1 MW genset: 182 sq. ft.
4 x 500 kW genset: 180 sq ft.
And when working clearances are added, the single large generator set will take significantly less space than multiple, smaller generator sets. But the single, larger generator set cannot be broken up into smaller blocks, so you need to consider not only the total footprint but the footprint of the individual units. A 2 MW genset is 30% longer that a single 1MW genset, and 40% longer than a 500 kW genset. If there is a minimum length requirement driven by the site, smaller paralleled units may be a better fit for your site.
Of course, this does not consider the additional equipment required for installation – fuel systems, exhaust systems, distribution, and paralleling equipment – that would be required for multiple smaller generator sets. Or outdoor installations, where the generator set would be installed in an enclosure.
- How important are space constraints in your installation(s)?
- Do you have any examples where space played a role in your decision process?
- What are some other factors that you consider when determining if paralleling generator sets is right for your installation?
- What are some of the concerns you have with paralleling units? With a single unit?
I will be exploring this topic more in upcoming blogs, and I am interested in your opinion. Please post below.
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