While integrated, on-generator paralleling solutions have been available for more than a decade, some users only consider paralleling for large kW and mission critical projects due to perceived cost, space requirements, and complexity.
With the advent of on-generator controllers, paralleling systems are being used more frequently for modest or low kW projects due to the advantages in reliability, redundancy, scalability, flexibility, availability, serviceability and ease of use offered by these newer systems. They are also used on projects where space requirements pose challenges for larger generators.
Advantages of Parallel Generation vs. Single Genset Configurations
Parallel generation offers many advantages versus single genset configuration including better reliability, redundancy, reduced cost and space requirements, and the flexibility to add or subtract generators from the system depending on growth and usage.
“Generac’s Modular Power System (MPS) feature generator mounted paralleling switches which allows the generators to automatically connect to a common generator bus without the need for external switching devices. With the on-generator integration of the paralleling switching, there is no need for expensive and complicated third-party switchgear,” said Mark Sweeney, Business Manager – North Central for Generac.
The generators are simply cabled to a common electrical connection point: junction box, large transfer switch, or a distribution panel. Through this level of integration Generac has been able to offer thousands of parallel solutions at the price point of single larger capacity generator (i.e. 3 x 500 kW for the same cost as a 1 x 1500 kW). The MPS extends up to 2000 kW with a different hardware configuration to support the system capacity increases.
Redundancy Gains with Paralleling
Parallel power generation is simply more reliable than single engine generator solutions. With multiple generators on call, redundancy is built-in and reliability is increased because each generator backs up the other. The resulting gains in reliability for the critical loads are significant. For example, if a standby generator has an assumed reliability of 98%, an N+1 configuration has a reliability of 99.96% and an N+2 configuration has a reliability of five nines (99.999%).
“A common concern is that the redundancy benefits result in significant added costs because one or more of the generators are under-utilized,” noted Sweeney. “However, most applications have typical load levels at 50 to 60%, with little or no load shedding, which means you can easily achieve N+1 redundancy for the application’s mission critical load,” he explained.
For ground up designs, mission critical loads are often separated onto their own circuits. In these configurations, typical load factors may even be higher and still maintain N+1 or N+2 redundancy for the most critical loads through the ability to shed less critical loads.
Expandability Benefits with Paralleling
Many times when sizing generators, it is difficult to adequately plan for anticipated load growth. If growth projections are too aggressive, precious project capital is expended before it is necessary. If growth projections are too low, the facility may be left without reliable standby power or require expensive generator upgrades.
Generac’s MPS solutions allow users to simply “plug and play” additional generation modules anytime they are required. Smaller units of different kilowatt ratings could be used in any combination to meet a particular load profile.
“For a growing facility, being able to easily expand the capacity of generators reduces the initial cost as a more modest generator system can be specified. This lower initial investment can help meet budget or capital constraints while offering the flexibility to add onto the system quickly due to unexpected growth,” said Sweeney.
Utilizing multiple smaller generators instead of a single large unit solution also offers greater application flexibility. This can be a significant advantage in meeting many site-specific logistical constraints. Multiple smaller generators offer greater weight distribution making roof-top installations more feasible. This provides a compelling option versus installing a larger generator into the building requiring the use of a complex remote cooling scheme.
Smaller generators are also shorter and lower, providing flexibility in applications with height or depth constraints. This often opens up the parking garage as another location possibility for the generators. In addition, the generators do not need to be located side-by-side or even together, thus providing significant installation flexibility for retrofit projects.
“We have seen a significant increase in paralleling solutions for modest kW projects as more and more engineers and specifiers realize that on-generator paralleling significantly reduces the cost and complexity compared to traditional paralleling which relies on bulky third-party switchgear,” said Sweeney.
For more information about Generac’s multi-faceted MPS solutions, please contact your local Generac Industrial Power Network Distributor, call 1-844-ASK-GNRC or email ASKGNRC@generac.com.