Recent technological advances in standby power generation have brought paralleled power systems to a much wider range of applications. The new products that embody these advances present electrical contractors with outstanding opportunities to expand both the scope and nature of their work, as well as their bottom line profits.

Generac’s Modular Power System (MPS) is a true breakthrough advance that brings all the advantages of paralleled power solutions to a much greater range of standby applications — and at a much lower cost. Because of that, these kinds of larger projects are now within the realm of more and more electrical contracting firms. Due to the nature of this work, there is an opportunity for greater margins on higher dollar jobs, provided that those responsible for specifying, quoting and installing these systems have an understanding of how they work and how to properly install them.

Advantages of the Modular Approach
Generac’s modular gensets are like building blocks that can be put together in any combination of up to ten generators. In this manner, MPS offers a superior alternative to large, single engine generators that are expensive and one dimensional in their capabilities. It also makes obsolete traditional paralleled solutions that rely upon switchgear, because Generac’s advanced paralleling technology is onboard each generator. The results are tremendous cost savings as well as the additional advantages of scalability, flexibility and redundancy.

MPS gensets are built around mass-produced automotive and truck engines that — because of economies of scale — are far less expensive than large specialized diesel or natural gas engines. Eliminating bulky and expensive switchgear from the equation makes the MPS solution even more cost-effective.

Generac’s modular gensets range in output from 100 to 600 kilowatts, with MPS-compatible Gemini ® Twin Pack models offering up 750 kW of output. Multiple fuel types offer additional options for a variety of commercial and industrial applications. These allow the design and implementation of systems ranging up to 6000 kW, or 6 megawatts.

MORE CHOICES, MORE POSSIBILITIES
Generac’s MPS modules are available with four fuel options — diesel, natural gas, liquid propane (LP) vapor and bi-fuel (a combination of diesel and natural gas). The bi-fuel option is especially attractive in certain applications, because diesel fuel storage is minimized and natural gas comprises 80 to 90% of the fuel consumed.

The Gemini® Twin Pack model, featuring two generators within a single sound attenuated enclosure, is also MPS compatible, offering the highest power density in the industry.

MPS units of different output ratings, and even different fuel types, can be combined and paralleled without any additional consideration.

 

Available MPS Modules

 

• 100 kW natural gas
• 135 kW natural gas or LP
• 150 kW natural gas
• 200 kW natural gas
• 300 kW diesel
• 300 kW bi-fuel
• 375 kW diesel
• 375 kW bi-fuel
• 400 kW diesel
• 500 kW diesel
• 600 kW diesel
• 600 kW Gemini® bi-fuel
• 750 kW Gemini® diesel
• 750 kW Gemini® bi-fuel

Before discussing the additional advantages of the modular approach, let’s review how traditional paralleling systems have typically been configured and installed.

Traditional Paralleling of Electrical Generators
The concept of paralleling multiple gensets to produce greater amounts of power is not new. In fact, it is a well-proven method commonly used with large megawatt units in premium installations. By paralleling multiple large gensets (effectively ranging from 750 kilowatts to 2.6 megawatts), high output systems can be created for applications requiring large amounts of backup power. The multiple generators also back up each other, providing the benefit of redundancy that increases overall system reliability and coverage of the critical load.

As feasible as this approach may be, the very nature of this kind of system makes it very complex, unwieldy and expensive. The reason for that is the required use of traditional paralleling switchgear.

Historically, paralleled power generation has been accomplished by utilizing the products of third party vendors that integrated UL 891 dead front panel boards into generator paralleling switchgear. Though effective, this approach has its limitations — cost being the most notable drawback. The capital cost for low voltage traditional generator switchgear is typically $20,000 to $25,000 per section. Paralleling two generators typically involves one section for each genset, plus a master control section, totaling between $60,000 to $75,000.

Space for such a system is a major consideration. The switchgear cabinets need dedicated floor space inside a building. Each section is typically 36” wide, 48” deep and 90” tall, with a required clearance of at least three feet to the front and back. When the space required for the huge gensets and the array of switchgear is added together, the square footage requirements become significant. The generators themselves are very heavy, necessitating placement at ground level on highly engineered pads with considerable soil preparation, which further limits site options.

Because of its inherent complexity, installation of such a system requires a high level of expertise on the part of the contractor and engineer, as well as proper coordination between the generator and switchgear technicians. That rarely goes smoothly, unless the entire system of generators and switchgear has been built as an integrated system and tested at the factory. Because of all these factors, it soon becomes obvious that this traditional approach can only be justified for a limited number of high-end applications.

The complexity of the traditional control system brings its own set of potential problems. Each generator in the system typically includes four to six micro-controllers, and for the entire system to work well, they must operate perfectly together. These controllers oversee the following functions for each genset while a master controller integrates them into a paralleled system:

Genset protection

• Speed control
• Load balancing
• Synchronizing
• Voltage regulation

 

These controllers are typically a combination of analog and digital technology from various manufacturers that are hardwired together into an amalgamated system. They often operate at different voltages or signal outputs, making them more difficult to calibrate and maintain. Thus, a two generator paralleling system would require nine to fourteen controllers once the master control section is included in the controller count. Getting all these elements to work together in harmony is a major challenge for engineers and installers. Experience shows that there are numerous points of potential failure that can render the system inoperable.

Isn’t There a Better Way?
Naturally, the question is — why so many controllers? Why not design the system with a single controller per generator? If the complexity, space requirements and cost of the paralleling switchgear could be eliminated, wouldn’t that be a far superior approach that would still take advantage of the benefits of paralleling, such as redundancy? Why not develop a modular system using smaller generators that would provide additional benefits and make them available for many more mainstream kinds of applications?

Those were the questions that Generac Power Systems engineers asked themselves as they tackled the challenges of taking a new approach to paralleled power. The result was a true breakthrough that brought with it additional advantages to make the MPS solution a far superior method of paralleling generators.

Modular Scalability
Many times when sizing generators for new or expanding facilities, it is difficult to effectively plan for anticipated load growth. If projections are too aggressive, precious project capital is expended before it is necessary. If estimated needs are too low, the facility may be left without reliable standby power or require expensive generator upgrades.

The Modular Power System is designed with expandability in mind, allowing multiple generators to be added as needed. MPS modules are designed to simply “plug and play” and may be combined with other MPS units of any size. Additional kilowatts can be added at any time. This expandable system can be scaled to more precisely match load requirements as facilities grow or change. Units of different kilowatt ratings (or even different fuel types) can be combined in any combination to meet a particular load profile.

Modular Reliability
With multiple generators on call, redundancy is built-in and reliability is increased because each generator backs up the others. If the electrical load is divisible, one or more generators can handle a portion of the load while the other redundant gensets are offline.

The multiple genset system provides improved reliability through design:

 

• Proven high volume engines are more reliable than very large, low volume engines
• Integrated system components are designed and manufactured to work together
• Redundancy is provided for critical loads
• Coverage is available during maintenance
• Backup power is available even if one unit is not operating

In many applications, the load requiring the highest degree of reliability is a smaller portion of the total generation capacity. In these situations, the MPS solution automatically backs up the most critical load with the benefits of n+1 or n+2 redundancy. Since many standby power systems are designed with the gensets using only 60 to 70% of their full rated capacity, a system with three or more units offers built-in redundancy without the need to invest in an extra generator.

To realize the benefits of increased system reliability, it may be necessary to implement load shedding of less critical loads. MPS supports this functionality through definable load shed contacts. The contacts can be integrated with transfer switches, facility shunt trip distribution breakers, or integrated into the building management system.

Modular Flexibility
By utilizing multiple generators instead of a large, single engine unit, much greater application flexibility is available. The Modular Power System can offer significant advantages in meeting site-specific logistical constraints. Since the MPS generators are lighter, rooftop installations have better weight distribution. MPS gensets are also shorter and lower, providing flexibility in applications with height or depth constraints. In addition, the MPS generators do not need to be located side by side or even together, thus providing significant flexibility for retrofit projects.

MPS also provides flexibility during service operations. With multiple generators available, a unit can be taken out of service for scheduled maintenance or repair without complete loss of standby power. Remaining in-service units can still serve critical loads, utilizing the priority loading feature of the MPS controller. Units are identified as out of service in the controlling software and the system adjusts priority loading sequences automatically.

Modular Serviceability
The prime movers powering MPS gensets are readily serviced by automotive or diesel truck technicians. With less expensive service and replacement parts, the maintenance cost for the MPS solution is slightly less than the large single engine solution when compared on a kilowatt basis.

Though catastrophic failures of standby generators are not common, the MPS solution significantly mitigates the effects of such an event. The inherent redundancy of the system ensures backup power even during equipment failure. The capital cost to replace a unit is a fraction of the single engine approach. Finally, the smaller modular units are also easier to move and place on site. Instead of requiring a heavy-duty crane, the MPS units can be handled with a forklift or much smaller crane in most cases.

Modular Availability
Because they use readily available engines, the lead times for these products are measured in weeks instead of months. For hard-pressed project managers, this quicker delivery can make a difference in meeting deadlines and avoiding delay-related penalties.

The System is the Solution
“We’re seeing MPS projects of all kinds,” says Don Vanderbrook, Generac’s director of applications engineering. “As more and more engineers realize the advantages of this system, they’re being increasingly creative in applying the concept and the technology to their own unique challenges.”

The considerable cost savings also open some eyes, according to Vanderbrook. “The larger the project, the more significant the cost savings is with the modular solution. When future or projected load requirements are uncertain, the scalability factor is a big money-saver and greatly reduces upfront costs, because modules of any size can simply be added if and when they’re needed.”

One look at the numbers will convince most any project engineer that the Modular Power System is worth a serious look. For example, a traditional 600 kW single engine natural gas standby genset costs around $140,000 and is typically available with a lead time of twelve to sixteen weeks. The alternative MPS solution, available in about six weeks, is comprised of four QT Series 150 kW natural gas units with a total price of approximately $66,000. That’s a savings of $74,000, or 52%.

For projects involving switchgear, the cost differential is also significant. As an example, Vanderbrook cites a recent project where the original proposal called for a single 1750 kW diesel genset with switchgear. “Our alternative was an 1800 kW Modular Power System. By eliminating motor-operated breakers and switchgear through the use of MPS and five Generac closed transition transfer switches, our quote was $35,000 less. An additional benefit is that we are able to include an automatic load shedding feature and offer levels of redundancy the original system lacks.”

Though the actual numbers may vary, the point is clear — MPS offers a tremendous value to the end user. This solution is now feasible and cost-effective for all kinds of standby applications, so contractors will start seeing these systems more and more often in the future.

A Typical Configuration
The accompanying diagram shows a typical configuration of an integrated paralleling system with two gensets and two automatic transfer switches (ATS). To understand the sequence of operation, let’s look at an automatic start sequence initiated by a utility failure.

The generators are connected to the system controller via a single RS485 data line. A two-wire start line is run from each ATS in a manner similar to any single engine standby solution, except the connection is made to the system controller. In this illustration, the critical load ATS is configured to pick up load within ten seconds after an outage.

Upon utility failure, the transfer switches sense the loss of utility power and send a two-wire start signal to the system controller that provides a start command to all the generators in the system. The gensets start and accelerate to rated speed. The system controller gives the first generator that reaches rated voltage and frequency its permission to close onto the dead generator bus. Upon sensing the energized generator bus, the critical load ATS will transfer onto generator power.

At this point, with one generator on the bus, the second ATS for equipment load is prevented from transferring onto the generator bus by a priority loading feature built into the system controller, thus preventing an overload of the first unit onto the generator bus. With the generator bus now energized, the remaining generator must synchronize to this power waveform before it can switch onto the bus for parallel operation. The integrated generator controller controls this process.

As additional generators parallel to the bus, the system controller compares available generation capacity to expected load. Load is added in order of priority only when sufficient capacity is available.

Another function of the system controller is load shedding. If a generator does not start or is taken offline during operation, load equal to the lost generator capacity remains offline or is removed from the system. Load shedding can be performed within the ATS or via a shunt trip circuit breaker within the facility’s distribution system.

Profitable Opportunities
By embracing this technology and becoming familiar with how these products are configured, electrical contractors can boost their revenues and profits through the installation of modular systems. As the number of these applications increases, the opportunity for relatively easy, higher margin work will grow. For many contractors, taking on these kinds of jobs will provide a real boost to the bottom line.

Generac and its industrial dealers conduct periodic MPS seminars for the engineering and electrical contracting community. To obtain product information or learn about the offerings in your area, contact your local Generac industrial dealer or call toll free 888-GENERAC.

 

 

FORT SAM HOUSTON — AN MPS SHOWCASE

U.S. Army complex in San Antonio, Texas. As one of America’s oldest military bases, “ Fort Sam” is the home to various functions, including the active maintenance of all U.S. Army medical records. The campus includes numerous buildings and features three separate Generac Modular Power Systems:

3 x 500 kW diesel • 2 x 500 kW diesel • 4 x 600 kW diesel

The North Beach installation at Fort Sam consists of three 500 kW diesel gensets and is a good example of how these projects take shape from the contractor’s point of view. Jim Lambrecht, sales representative of the local Generac dealer, Waukesha-Pearce, Inc., provided advice and technical assistance throughout the planning and installation process.

“We were a little skeptical since this was something new, but after attending a few emonstrations and meeting with the project engineer (Alderson & Associates) and some of the technical people, we decided to try it on the North Beach project,” says John Wright, vice president of Nathan Alterman Electric.

Because of the nature and requirements of the application, the advantages of the MPS approach were key elements in its selection. “There was a requirement for redundancy and the cost was lower compared to other parallel systems,” Wright says. “The ability to expand the system in ‘blocks’ was another plus. The infrastructure was designed to add another generator to support future expansion of the UPS system along with other emergency loads and still maintain redundancy. The client likes the flexibility of the modular system for maintenance and future expansion capabilities.”

Project time and space constraints also were a factor in choosing MPS, according to Wright. “Two of our projects at Fort Sam were fast track. Delivery was about four weeks better than a standard paralleling system and installation was much simpler. We were able to pull, test and protect the feeders from the building to the collection box about four weeks after approval versus waiting ten to twelve weeks on traditional paralleling gear. I would say that this type of system easily saved us four weeks on the overall schedule. Space was another big issue, since these are existing buildings with very limited space, but we were able to configure the system to fit the site.”

When asked what advice he would have for other contractors considering these kinds of jobs, Wright was succinct. “If cost, delivery, flexibility and ease of installation are important factors, you should consider using this kind of system.”