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POWR2 offers six Hybrid Energy System (HES) models with outputs from 3.7 to 60 kVA and storage ranges from 7.5 to 120 kWh. All models include forklift pockets, lift and drag skid lift points. (POWR2)

Developments in engine-based gensets

With demand for generator sets steady and regulatory change settling, suppliers can rationalize their offerings and push improvements in areas like noise abatement and economy.

Generator set OEMs may be at a unique time when it comes to further engineering development. They have responded to the most stringent emissions regulations in the world: Tier 4 Final in the U.S. and Stage V in Europe. For now, regulations seem set for the foreseeable future.

“We are at something of a plateau with emissions standards, which means engine makers can take a breath,” said Tyler Wiegert, senior analyst at Power Systems Research (PSR), an international firm that tracks and forecasts global powertrain production data.

Engine makers are indeed ready for new challenges—and there are plenty yet to tackle.

Market insights

One challenge for engine makers is how to optimize their engines designed in the rush to meet the tight timelines of the phase-in period of those emissions regulations, according to Wiegert. They also have the pressure of delivering cost-effective solutions that meet a worldwide set of complex regulations and local market conditions. While the U.S. and European standards are stringent, they add complexity by differing in crucial ways with each other.

“Stage V requires a DPF, while often engines delivered in the U.S. can get away with SCR and DOC only,” he said, referring to diesel particulate filters, selective catalytic reduction, and diesel oxidation catalysts, respectively. An example that illustrates the point is FPT Industrial’s N67 200 kWe Tier 4 Final engine, fitted with its HI-eSCR aftertreatment system with a DOC as well. Presented in December 2018 at the Power-Gen International exhibition, the 223-kW standby-power engine is “DPF free,” FPT points out.

“In this moment, emissions are the most challenging driver from a technological point-of-view and have an important impact on our product,” Alessandro Zilli, FPT Industrial product marketing manager – Power Generation, told Truck & Off-Highway Engineering. “At the same time, exhaust aftertreatment systems are important for the power generation industry due to the emissions standards being implemented globally.”

Other regions of the world follow even different, less stringent regulations. Engine makers also have to contend with variations in fuel quality worldwide. The engines are used differently as well, from providing only standby power in industrialized nations to primary power in less developed ones.

Other market drivers, according to Zilli, are the reliability and versatility to guarantee higher performance and more efficient possession / use costs—i.e., continually improving the total cost of ownership (TCO) equation.

“[Engine manufacturers] are looking at how to optimize their production so that they can most efficiently produce an engine that meets all of their markets,” Wiegert explained to TOHE. “OEMs typically must have seven or eight different versions of one engine to meet these different requirements.”

The good news is that demand remains steady if not steadily increasing. In the fourth quarter of 2017 and the first quarter of 2018, market demand jumped by 10%, according to Wiegert. Fuel costs and emissions are driving sets powered by natural gas or gasoline.

“In the 10-kW to 2-MW range, alternatives to diesel are growing faster than diesel in the last two years,” he said. Gasoline is the fuel of choice for smaller sets, natural gas for larger ones.

The strong economy has also driven sales (which might temper a bit in 2019). There are new niche markets as well. “Marijuana production has created a huge demand for standby generators in marijuana [growing facilities],” Wiegert shared.

Who could have predicted that?

Keeping quiet and compact

Other regulations are becoming more important, too, such as limiting noise in urban settings. “We are seeing more use of electric starters and low-noise sets as well as sets optimized for consumer convenience,” said Wiegert.

A good example of this trend are the Silent Plus offerings from Himoinsa, the Spanish supplier of power generation equipment. The Silent Plus family is powered by Yanmar, FPT and Scania engines, in the power range of 20 to 550 kVA. They feature a dual-core exhaust system as standard along with insulating materials such as high-density, 100-mm (3.9-in) thick rock wool and silent blocks.

In 2018, Himoinsa launched the new HRFW S+ and HRSW S+ generator sets, equipped with FPT and Scania engines. Possible uses include urban areas, sporting, music and cultural events, where noise restrictions require generators to be increasingly quiet.

Another critical element is the footprint and size of the generator. Smaller is better, but meeting emissions regulations like Tier 4 Final requires more aftertreatment equipment, increasing the size of sets by as much as 25%, according to Wiegert.

Newer models are touting reduced footprints as well as reduced noise emissions. One such example is Cummins’ QSG12 50-Hz diesel generator series with new models C400D5 and C450D5 powered by a Cummins 4-cycle, inline, 6-cylinder dual speed engine. They provide power in the 360- to 450-kVA range. An improved design and “advanced combustion” system mean less space and higher power density, according to Cummins. With a reduced noise level of 67 dB(A) at 75%, Cummins believes the new genset models are especially suitable for hospitals, manufacturing, commercial and industrial facilities.

Future tech—hybrids and more

Electrical hybridization is not only for moving vehicles. “Generator sets that meet Tier 4 Final are sensitive; they do not like running at inefficient low loads,” said Toby Nunn, operations director for POWR2, in an interview with TOHE. “When they do, this can lead to wet stacking.”

Wet stacking is a condition in which unburnt fuel passes into the exhaust system, and into the sensitive aftertreatment used to meet Tier 4 Final.

“Understandably, generators are often over-specified, spending much of their service life running on low loads. This has always been an issue with diesel generators, but it’s especially damaging to Tier 4 Final units, causing significant and sometimes permanent damage,” Nunn added.

To help solve these problems, POWR2 offers its Hybrid Energy Systems (HES), an add-on unit that integrates with diesel generators to optimize load supply. It creates a hybrid system that uses lithium-ion battery system and automatic load-level sensing to switch power supply as needed between the generator and the HES.

The idea is to keep the diesel engine operating near its ideal load point most of the time, using the generator for higher loads and storing excess energy in its battery for use when lower loads are demanded, saving more energy and reducing fuel consumption overall.

“Other solutions use a load bank or heat up the exhaust to keep the aftertreatment working, but that is burning fuel and not creating any energy for useful work,” explained Nunn.

What other developments might we see in the near future? “Not only will we see more hybrids, but more energy storage systems with generator sets,” said Joe Zirnhelt, chief operating officer and strategist of Power Systems Research. “An internal combustion engine will be part of the picture for generator sets for the foreseeable future. But how they are configured and how they participate in the system might change. The engine might not be a dedicated genset outside of an office building—it might be balancing power within a small microgrid system.”

More use of gasoline and natural gas along with newer sets increasing their power density and decreasing footprint is also easy to predict.

Zirnhelt also sees increasing use of telematics for remote monitoring and operation. Remote operation means not having to send a person to service a remote generator, ideal for oil and gas or agricultural use among other applications.

Perhaps one of the more interesting ideas for the future is something Thomas Bourgeois, deputy director for the Pace Energy and Climate Center jokingly terms cash-for-clunkers.

“Engine-based generator sets can last a long time,” he said. Many existing sets are 20 years old or more, and those old sets are vastly more polluting than the newer sets that meet Tier 3 or Tier 4 Final emissions. “We are advocating a program of retiring those old sets and replace them with newer sets as one of the fastest ways of improving overall emissions.”

Untreated biogas as power-gen fuel source

Scania Engines’ bread-and-butter power units for generator sets are diesel engines, as with many traditional engine makers, but it also is exploring not-so-traditional alternative and sustainable power sources for future systems.

Though only in the experimental phase, Scania Engines announced in 2018 a multi-year project that involves testing one of its engines running raw gas, or biogas that is “untreated,” for power generation. Working with energy recovery specialist Tekniska verken, the researchers take the raw biogas directly from the digestion chambers, which break down the organic waste to be used as fuel for the Scania engine, to see how it performs over 600 hours of tests.

The project’s goal is to discover a quicker and cheaper process of producing biogas for power generation.

Scania also is working with waste-recycling entity Telge Återvinning to test the use of landfill gas in its engines. The “simple gas” is extracted directly from landfill sites without refining or upgrading it by drilling holes directly into Telge’s landfilled waste.

“There are landfill sites all over the world,” said Holger Mattsson, project coordinator at Scania Engines, in a statement. “If we can effectively use the lower-quality gas that comes directly from these sources, there is huge potential for the market and for consumers.”

A Scania 16-L V8 engine designed for low-pressure compressed natural gas (CNG) in power generation is being used for the projects. It is switchable between 1,500/1,800 rpm in power nodes between 333 and 426 kW prime power. Other provided specs include continuous operating power: 330 kW (50 Hz), 350 kW (60 Hz); and gas feed pressure: 50 mbar.

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