Reliability and Flexibility

The next generation of portable power

Photo courtesy of Caterpillar
A fleet of CAT portable generators

The global portable generator market is expected to grow at a compound annual growth rate of 7.91% from 2017 to 2021, according to a study by This is due to a growing demand for uninterrupted and reliable power supply from all major end-users, especially commercial and industrial needs.

Portable generators power critical facilities, remote events, and households during blackouts. Portable power generators are also an essential part of the construction industry. When contractors find themselves at job sites where there is intermittent electrical service or none at all, portable generators allow contractors to continue working without disruption and meet deadlines.

“When it comes to portable generators, there are typically two general categories that they fit into,” says Jim Siffring, vice president of sales in the Western United States for Girtz Industries.

“The first category is portable gensets that are part of a larger system and have a specific task associated with it,” says Siffring. “Examples are aggregate crushing spreads, portable asphalt plants, TV production trailers, tower cranes, etc. In these applications the loads and load characteristics are generally well-known and the generator can be designed to work well for that specific task.”

“The other general category is rental applications,” he says. “In a rental fleet, flexibility is the key. It is important to keep in mind that these generators can end up just about anywhere, doing just about anything.

“A generator designed for rental fleets in warm climates is often specified without any kind of starting aid equipment, such as engine coolant heaters or battery chargers. If that machine were to end up in a northern climate in the winter, it would not be useful without some of these items installed.”

Credit: Sunbelt Rentals
Selecting the appropriate generator size for the application is key.

Size Matters
Concerning sizing, the issues related to underloading on genset engines has been well documented.

“Everyone that has been in the rental business has had the case of the guy that needs a 25 kW genset, but asks for 50 kW so that he has some safety factor, and the only unit that is available in the yard is an 80 kW, so he takes that to his site,” says Siffring.

“Now he has a severely underloaded genset and before long he is having issues with the emission controls on the genset, which may cause a shutdown.”

Generally speaking, standby- and prime-rated diesel generator sets are designed to operate between 50 and 85% load, while continuous-rated diesel generator sets optimize between 70 and 100% load. Operating diesel generator sets at loads less than 30% for extended periods can impact uptime and engine life, according to Caterpillar.

Flooding is also an issue. In disasters such as Hurricanes Katrina and Sandy and the Fukishima Nuclear Power Plant disaster in Japan, the industry learned that flooding can and will happen.

“A diesel genset may be above the level of the water. But we found that the fuel storage may not always be that high. As soon as the water enters the fuel tank, the system is down and will be for some time,” says Siffring.

Credit: Sunbelt Rentals
A portable power system from Sunbelt Rentals

All Shapes and Sizes
Generators come in all shapes and sizes and are used for various purposes. In particular they are used in onsite applications as backup power for construction and during disaster-related outages.

When it comes to the world of generators, the general rule of thumb seems simple. The bigger the generator, the greater the output it will produce and for a longer period of time. But there is much more to it than that, say experts.

Portable generators have come a long way and technology has advanced tremendously. New technology, utility regulations, and emissions standards are also changing the generator game and generators are becoming cleaner, quieter, and still more powerful.

Credit: John Walsh
The G70 from Doosan Portable Power is
engineered to provide high reliability with low
cost operation.

As the generator market is expected to reach the $25 billion mark, diesel generators are expected to lead the way. This segment is primarily driven by increasing demand from data centers, IT facilities, and healthcare infrastructure in developing regions and is expected to create new revenue pockets for the generator sales market during the forecast period, according to a MarketsandMarkets report.

Wheeled portable generators are still the biggest sellers and are often used to power homes and small businesses like restaurants. Stationary generators are larger and more expensive but usually run on propane or natural gas. Larger portable generators can be towed on a trailer to any location.

Generator sales often spike during major storms like hurricanes. In poorer countries where power goes out frequently due to infrastructure issues, generators are a necessity. Much larger generators can even be used to power hundreds of households during blackouts.

Choosing the right generator is key.

“No two projects are the same,” explains an expert from Sunbelt Rentals, one of the largest equipment rental companies in North America.

Credit: Mike Newell
A wheeled John Deere portable generator powers a housing construction site.

Safety First
According to Sunbelt Rentals, it is especially important on large projects that the person responsible for sizing a project is familiar with the safety standards for tying in temporary power and understands the electrical loads on the system as well as the availability and capability of the many temporary power options available.

Sunbelt’s field experts emphasize that when looking for a generator, it is important to follow safety guidelines for temporary power.

“If the customer is a small business or residence, most utility companies will provide guidance on transfer switches and backup generators to ensure that an emergency generator is disconnected from the grid while running,” they say. “This is critical so that power cannot be back-fed to the grid, creating a potentially unsafe situation if crews are working on a powerline they think is dead.”

Photo courtesy of Hedrick Brothers
A 2,250-kW diesel power emergency generator is put in place at a Florida detention facility.

For larger jobs, experts should be called upon who can do everything from site studies to interconnection plans that comply with IEEE Standards for utility grid interconnection, Sunbelt Rentals staff advise. Responses from providers must be tailored to the complexity of the project and the amount of input and response that the customer desires.

“Some utility companies have technical expertise and simply order equipment, while others ask us to provide turnkey projects with engineered solutions, electrical single-line diagrams, plot plans, interconnection protection documentation, as well as full installation and operation of the project,” explains a Sunbelt associate.

And some projects can be very large.

For the Super Bowl in 2016, Sunbelt Rentals provided 5 MVA to get power to more than 1,100 customers in Massachusetts so they could watch the New England Patriots in the Super Bowl. It was a massive undertaking.

Near Sacramento, CA, a pharmaceutical manufacturing plant needed to make critical repairs and upgrades to its main power substation. The plant produces various medicines with two and three-week batch processes. Any interruption would result in significant financial loss, and more importantly, a shortage of critical, life-saving pharmaceuticals.

For this job, Sunbelt Rentals installed and tested 5 MW of generator power with transformers to power the plant’s 12,470-volt distribution system. The project was installed over the three-day period prior to Christmas 2016; the generators were brought online by 8 a.m. on December 26. The generators provided plant power for three days while substation repairs were made, ensuring continuous production for the plant.

Specifications can vary greatly depending on factors such as local codes, geographical location, climate and elevation, fuel availability, and many other considerations.

“Local engineers usually have a pretty good understanding of these requirements and will specify the correct features and options to meet the requirements of the local conditions,” says Siffring. “That is why it can be valuable to consult with local engineers or providers if the system is being designed somewhere other than the end-user’s location.”

“Safety is always a key concern when dealing with power products and industrial job sites,” says Michael Goche, director of product management for Generac Mobile Products.

“With our new mobile generators, we’ve relocated each product’s control panel to the rear of the unit to separate it from the generator’s power distribution, making maintenance-related tasks safer than ever before. With this change, operators and service providers are now able to check diagnostic information, output demands, active alarms, and maintenance requirements via the generator’s Power Zone controller without having to tangle with power cords and other potential worksite hazards,” says Goche.

New Rules Require New Technology
The latest developments and trends for generators are largely coming from regulatory and corporate changes in utility power company responsibilities. State and federal air quality regulations are creating more need for clean generators. Meanwhile, utility companies are under pressure to keep the lights on during upgrades.

“We are seeing an increase in the number of states and municipalities that are putting pressure on utility companies to keep customers powered,” writes Sunbelt personnel. “In some cases, utility companies are self-policing these new policies in order to increase customer satisfaction and fulfill their commitment to keep their customers’ power on.”

While many companies still take an entire city circuit offline for eight to 12 hours during substation maintenance, consumers are becoming less tolerant of outages.

Credit: iStock/Lex20

As the prevalence of electronic devices in personal and business lives grows, as well as the interconnection of household appliances, devices, and even vehicles grows, utility companies everywhere will be pressured to use temporary generators to keep customers powered during both planned and unplanned outages.

Current Environmental Protection Agency emissions regulations are also playing a role. Tier 4 engines are the new standard in new generators.

“It is vitally important to size the generator properly,” writes Sunbelt. “Tier 4 engines are not designed to run lightly loaded, and will shut down if run under a light load for too long. In the past, it was common to oversize a generator to make sure enough power was available if needed, but now it’s more critical to ensure proper sizing to avoid generator exhaust system problems.”

Siffring agrees. “A significant problem that we see with final Tier 4 diesel engines is underloading,” he says. “So, sizing power needs is more important than ever because underloading—running a generator at less than its power capacity—leads to issues like wet-stacking.

“When a diesel engine is operated on light loads, it will not attain its correct operating temperature to properly burn fuel, which results in unburned fuel being introduced into the exhaust system. This fouls injectors and creates carbon build-up. When wet stacking happens, it can lead to all sorts of issues in the engine. Properly sizing a generator minimizes under-loading and helps ensure reliable performance.”

Positive Progress
A positive advancement that is proving beneficial to customers is utilizing equipment specifically designed for the rental market.

“This equipment has the ability to provide multiple voltages and single- or three-phase power from generators up to 1 MW,” says a Sunbelt staffer. “This allows us to deliver equipment with the flexibility to change voltage as needed, and in some cases, switch to single-phase power quickly without restrapping the alternator.”

Restrapping is the process of changing metal bars on an alternator in order to change the voltage and number of phases provided. However, this process can take up to 30 minutes, or sometimes more, depending on the generator design.

“Being able to quickly switch voltage and phase allows us to better respond to emergencies and get customers powered faster,” says the staffer.

And with the advent of the EPA Tier 4 Interim and 4 Final, people have had to re-think their sizing philosophies.

“The newer generators need to create significant heat, which equates to being loaded—usually to a minimum of 30 to 50%—to get reliable performance out of the emission controls,” says Siffring.

“Sizing a generator correctly to the project has become as critical as getting the correct permits. I compare it to permits because it can work the same way. If the generator running a tower crane shuts down, it can stop the project as quickly as a permit issue.”

Some of the other items to take into consideration are sound requirements, physical location, fuel quality, access, and durability.

A noisy generator operating in a residential area is going to cause complaints. A genset located in the dust plume of a rock crushing application will have a greater incidence of generator winding insulation issues. Having inadequate fuel filtration in a location where fuel quality is an issue will cause reliability issues and loss of engine power. A light-duty standby genset put into a prime power application will probably not last as long as the user would like it to.

“I live in Denver, so one thing that I think about a lot is elevation de-rate,” says Siffring. “Most folks in the United States never have to worry about elevation, as most gensets don’t really start to de-rate until you get upwards of a couple thousand feet. Where I live is around 6,000 feet above sea level, so most generators have a significant reduction in power output and cooling capacity. We have to design around those limitations.”

Parallel Technology and A Changing Market
Probably the most exciting trend in generators is the advent of simple and reliable paralleling systems for generators. Paralleling generators has been done for years, but only recently has the technology been refined into a design that makes paralelling simple and reliable.

Electronic engines and controls have opened the door to sophisticated systems that are user-friendly and don’t require an electrical engineering degree or years of experience to understand. A fleet owner can improve utilization by having multiple smaller gensets taking the place of single large units.

For example, a rental house could supply three 500-kW gensets as opposed to a single 1,500-kW unit for a project. In this example, the project may need 1,500 kw for the peak loads, but in other parts of the day the load may be significantly lower.

This can give the project operator a level of redundancy, as well as allow for maintenance windows when the project may only need one or two of the 500-kW units running.

Generator paralleling technology has moved ahead very quickly in the last few years, and what once was a challenging proposition is now becoming as simple as plug and play.

“This really lends itself well to disaster recovery as assets can be moved with smaller tow-vehicles, generators can be spread out for smaller requirements or grouped together for larger needs, and power capabilities can be tailored to changing requirements as local utilities and resources are brought back online,” says Siffring.

“I think they will become commonplace in the rental market,” says Siffring. “Girtz, as an aftermarket provider, has designed and manufactures a product that allows paralleling between several competitive machines. We see the demand for this system on the rise.”

Goche agrees. “Instead of purchasing or renting a 500-kVA diesel generator, the same power can be achieved by paralleling two 250-kVA generators. This allows for flexibility and redundancy, as you can switch out one unit for maintenance or add and remove units if power requirements change. A highly scalable approach, most Generac Magnum mobile generators allow for paralleling up to 32 units.”

Another trend is the market’s desire for TPEM or Flex credit engines.

This program allows end-users to purchase lower Tier generators and still be in EPA compliance. The EPA will allow users to purchase gensets with Tier 2 or Tier 3 engines to be delivered on or before December 31, 2017. This trend will end on that day, however, since all portable gensets will be considered Tier 4 after Jan 1, 2018.

Manufacturing Gensets Means Being Nimble

While the overall US generator market stands at around $19 billion and growing, manufacturers have been adapting to significant market changes in order to stay ahead of the curve.

From emissions standards to infrastructure needs to changing customer habits, flexibility is key, says Todd Howe, Manager of Global Generator Products for Doosan Portable Power, one of the largest manufacturers in the country.

“[Customers] are getting smarter about managing equipment,” Howe says. And when Howe mentions smarter management, he is referring to the 1,000 or so rental companies—from very large to small—that purchase Doosan products. Doosan produces generators ranging from 20kW to 500 kW.

Advancements in software and paralleling technology, however, have changed the game, as have federal emissions standards. Howe says generator manufacturers have gone above and beyond to update their portfolios.

Howe says he does not expect significant top-down changes to the Tier 4 emissions standards for at least five years. That allows for stability in what he calls a growing and crowded market.

And with the generator market expected to grow significantly, manufacturers must keep a close eye on the trends and scale accordingly.



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