Emission rules are killing some generation projects in the West, but an industrywide consortium is mounting an impressive antidote: meet the new "super engine."

ARES, once a war god, is now wading into the modern turf-battle for onsite energy—that name serving as the acronym and nom de guerre for an all-out, cooperative campaign to revolutionize engine designs: the Advanced Reciprocating Engine Systems program.

Onboard this ambitious enterprise are the big-three engine-makers—Caterpillar, Cummins, and Waukesha. They're allied with a dozen-plus universities and national labs, all being coordinated under the auspices of the US Department of Energy (DOE). Early in 2001, the consortium estimated that $250 million in research and development (R&D) money would be needed to meet the project goals—part from industry, with a like part from the DOE—thus formally launching the collaboration to build advanced reciprocating engine systems. Now, several years into a decade-plus undertaking, the ARES campaign ranks as perhaps the most ambitious and broadly based public/private partnership in distributed generation (DG) history.

Natural Gas–Fueled Project
For their part, participants from the private sector also agreed to invest in research on a 50/50 partnership with the DOE. It's all aimed at meeting unprecedented but critically needed goals in recip engine efficiency and drastically slashed emissions. For example, initial ARES targets for the first phase, which began in 2001 and was set to end sometime in 2004 or 2005, sought to raise engine efficiency about 5%—or, from where it was then hovering (at around 38% to 40%), up to 44%.

Just as ambitiously, if not more so, ARES labs have been seeking to curb emissions down to one-quarter of pre-ARES averages, which stood between 1 and 2 g/bhp-hr. The first-phase goal would lower NOx down "to just about half a gram per horsepower-hour," says the DOE's Ron Fiskum, who is the director for ARES development.

Meanwhile, as engine efficiency is increasing and engine emissions are decreasing, all of this should come at substantially reduced per-kilowatt costs both for installation and operation.

Three tall orders, and the bar is being raised progressively higher for the second and third phases, the latter set to extend into 2010 and beyond. By that time, ARES-inspired engine efficiency is targeted to rise, eventually, to an unheard-of 50%. As an intermediate step, the researchers and engine-makers are aiming for 47% efficiency by the end of 2007–2008.

In other words, the ARES participants want to attain efficiency improvements totaling at least 1% each year through the decade's end.

Simultaneously, engine emissions are to be shaved down eventually to a diminutive 0.1 g/bhp-hr, "or," says Fiskum, "about 0.07 grams per horsepower-hour NOx, using pipeline natural gas."

That's a reduction down to something like one-twentieth of pre-ARES levels. "For us to reach 0.07 grams NOx," he says, "is going to be a major, major step."

Putting that goal in market-competitive terms, ARES team members hope to score lower costs per-kilowatt-hour than any other generator engine, including diesels, large rich-burn and/or lean-burn natural gas engines, small gas turbines, microturbines, and even fuel cells.

To get there, participants have embarked on dozens of research challenges related to everything in the engine power-train from subcomponents to materials, low-friction coatings, sparkplugs, ignition issues, sensors, controls, and of course post-exhaust emissions scrubbers. Each of the 17 participating organizations has taken appropriate chunks of the R&D workload. All are laboring under agreements with the DOE to pool and publish their results collaboratively (see sidebar).

Now, what about real, tangible products coming to market?
Of the three engine makers, Caterpillar was first off the mark with first-phase ARES products, initially introduced in limited production in December 2002. The company designates these as its G3500C-series for power generation, consisting, initially, of a 20-cylinder, 2-MW lean-burn G3520C engine; it has been followed since by 12- and 16-cylinder versions, the G3512C and G3516C.

Caterpillar's Gordon Gerber reports that within the first 18 months after launching G3500C production, the company had received orders totaling more than 500 MW of installed power. What accounts for this strong reception is undoubtedly the engine's mechanical efficiency, which measures, he says, as high as 44.5%. "That's about 19% higher than anything Caterpillar had previously achieved," he notes. By comparison, pre-ARES engines from five years ago were getting about 36% efficiency.

Again, getting this efficiency is only the start—the ultimate goal is 50% by the end of the decade.

Perhaps even more pertinent is the bottom-line impact: The newer generators can be installed with a first cost of $400 to $450 per kilowatt, making them cost-justifiable to thousands of new prospects worldwide.

Rev Up for Higher Power Density
Getting there, though, "is going to be tough," Gerber admits, but the ARES consortium's critical strategy involves focusing on increasing an engine's relative power density, defined as getting more power output from an engine's mass. Historically, diesel systems have tended to outperform their natural gas–fueled counterparts and others, on the density scale; however, many of the competing technologies have a difficult time meeting the projected high-hour engine emissions levels. Hence, their role for power generation is currently limited to standby and low-hour applications, especially when matched against natural gas–based technologies.

Power density can be increased incrementally, notes Gerber, by such means as revving up the rpm and extracting more force with each ignition. By improving these—without injecting more fuel, adding size, or increasing upfront purchase/installation cost, maintenance work, or emissions—he explains, "You can get significantly more effective kilowatts out of the same part," all without increasing life cycle costs.

ARES-inspired engineering to achieve such gains runs the gamut: leaner combustion; higher-energy sparks; cross-flow cylinder heads for improved engine "breathing"; reduced engine friction; more durable parts to reduce maintenance costs; integrated timing, speed, and combustion controls; optimized valve events; better component integration; leaner air/fuel ratios; and assorted emission controls. R&D on all of these components (and others) has been more or less farmed out to various research labs, with the whole effort being coordinated collaboratively under Fiskum and the DOE. Following are a few examples among scores of studies now underway or planned for the future. (Note: Most of the following was reported in presentations at PowerGen 2004, from which this summary is adapted.)

Cummins Inc. has sought to improve combustion efficiency and to increase brake mean effective pressure (BMEP), aiming to yield more power per crankshaft revolution. Again, diesel engines formerly ranked as the champs on this, but the new ARES models are equaling them and should eventually exceed diesels' continuous BMEP levels. Cummins' designs are achieving higher in-cylinder expansion ratios, better cylinder aerodynamics, reduced friction, and improved sparkplug durability. Another major focus, says Cummins' ARES participant Paul Plahn, has been "larger, single turbochargers, and getting turbocharger efficiency up." This challenge requires scrutinizing "every little piece in the chain …" he says, "and by getting the turbochargers refined, looking at the Miller cycle [and others]," as well as developing "tricks with valving" to reduce engine parasitic losses. Other Cummins efforts are focusing on alternator efficiency. Plahn, who is director of advanced product development for Cummins Power Generation in Minneapolis, also notes that additional ARES work is underway at Cummins' engine division in Indiana.

Waukesha Engine/Dresser has focused on integrating speed, control detonation, ignition, and emissions output; advanced ignition systems for high combustion with temperature- and pressure-sensitive capability; and structural strengthening for higher power density. (Note: Waukesha is very active in the ARES and the ARICE program, described later in this article, but is currently restrained from making statements about its products and marketing, in anticipation of an initial public stock offering now in progress.)

Another initiative at Caterpillar explores improved detonation sensing and control, with the aim of causing the timing to retard automatically at detonation. Adding sensors effectively for each cylinder—in contrast to the former, less extensive array—is now enabling more refined monitoring and timing control, Gerber explains. This will eventually translate into higher efficiency and greater power output.

At Purdue University, piston friction is an area of intensive interest, as friction obviously subtracts significantly from engine efficiency and power. Indeed, more than half of an engine's friction comes from piston rings sliding against cylinders. Purdue's ARES team has designed an entirely new piston ring and cylinder liner clad with a dimpled surface like a golf ball. Friction is reduced, yet without a loss in sealing ability.

Oak Ridge National Laboratory (ORNL) in Tennessee is developing improved engine controls and sensors at minute levels. These will enable engines to safely achieve progressively higher output limits "that previously couldn't be realized," says ORNL's Tim Theiss, who is a program manager within the Fuels, Engines, and Emissions Research Center. ORNL is also delving into the systematic and non-systematic instabilities that arise, he notes, "when engines work harder" at high rpm. By analyzing and then correcting these, engineering researchers at Oak Ridge will be able to design machines that can sustain longer-term operation at higher rpm—thereby attaining all-important, higher power density. As lab results steadily emerge, Theiss notes, "We're providing manufacturers more fundamental information on how these engines operate as you push the limits."

Beefing up the power density by means of such measures also tends to result, not surprisingly, in more intense stresses on ignition systems. To counteract these stresses, various labs are applying exotic new design solutions, such as corona discharge ignition, rail plug ignition, rotating arc plugs, and laser ignition. Each is being developed and tested in a coordinated way at ARES consortium labs. Owing to the ignition improvements already attained, the first wave of ARES engines are capable of exceeding the former practical limit of 1,200 rpm, and revving up to 1,800 rpm for 60-Hz applications—for roughly 40% greater output, pound for pound. Notwithstanding this, though, if a customer's overriding concern is fuel economy rather than high output, the rpm can be reduced, while still maintaining 60-Hz cycles.

For still another sparkplug innovation, Caterpillar has developed a high-energy pre-chamber sparkplug now being used in an open-chamber system. As Gerber explains, "An encapsulated gap in the sparkplug functions as a small pre-chamber, admitting the lean air/fuel mixture, yet protecting the spark and the resulting flame front from being extinguished by turbulent air in the cylinder." This allows the plug flame to achieve a sufficient size, heat, and duration to ignite leaner fuel mixtures "and ensure stable, repeatable combustion," he notes.

Research on sparkplugs and ignition is ongoing, in fact, at several sites. ORNL, for one, is studying plug erosions, aging, and failures. Theiss describes the lab's "new, really detailed techniques that give us good insight into what's going on with them." Oak Ridge is partnering with sparkplug maker Federal-Mogul Champion to develop metal alloys for a new high-performance plug. "Our testing results are being shared with OEMs to provide ongoing information on how it's working and what it's doing," he adds, "so that those sub-component manufacturers can provide better products" to consortium design engineers.

Finally, the California Energy Commission (CEC) is underwriting an entire parallel R&D program and target of its own, quite similar to ARES (and easy to confuse with it), called ARICE—for an advanced reciprocating internal combustion engine. The CEC has long been a DG champion and funder of critical research such as this. ARICE program director Avtar Bining reports that several research projects around the state are exploring topics such as advanced laser ignition system, homogenous charge compression ignition, enhanced cooled exhaust gas recirculation, lean-burn combustion, onboard EGR-assisted catalytic fuel reforming, and advanced engine control systems. The ARICE goals and timetable, he says, are quite similar to those of ARES, with the main difference being "a greater emphasis on lower emission," while easing up, somewhat, on ARES engine efficiency targets. At this time, none of the three engine-makers has achieved the ARICE-specific goals, but Bining reports Waukesha in particular has made impressive advances in ignition systems research. The company reportedly intends to sell ARICE-compliant engines in California.

Benefits Abounding
These advances and others are emerging from the labs just in time to address assorted challenges facing manufacturers, would-be power customers, air-quality regulators, and the public at large. With the advent of ARES, they all will discover plenty of progress to cheer about.

First, energy customers will experience what Gerber describes as a "paradigm shift" regarding the capabilities of natural gas engines. From a prior situation consisting, he says, of "fairly low power and not very efficient" gas-fueled machinery, customers will now be stepping up "to very powerful engines that are, frankly, quite efficient and can do a lot more."

One example is peak shaving (i.e., using onsite engines to offset the utilities' often-high hourly peak demand charges on very warm or cold days). This role is a classic one for diesel onsite power. For the past decade or so, US per-capita power consumption has been steadily rising, in tandem with peaking rates and durations. The result is that the value and importance of gas peak shaving has escalated even higher. Rather serendipitously, ARES systems are arriving at a time when the value of high-efficiency, low-cost gas engines for this role is especially ripe. Gerber observes, "There's now a new world of opportunity for owners of these products to apply them, and this has worked out quite well."

How well? As already noted, Caterpillar's first wave of G3500C machines won orders for more than 500 MW of generation in just 18 months. Rather unexpectedly, though, the portion of that stemming from exports was an astonishing 80%—most of it from Asian and Latin American markets gobbling up the new engines' higher power density and low running cost. Engines like these make an extremely attractive alternative to quirky local utility power. In China, for example, demand for power has been soaring at about 15% or more annually, a rate "too fast for their energy planners to satisfy," Gerber notes, adding: "Overseas markets love the higher power density, love the low emissions profile—and find the size small enough to manage easily, to work on, to take care of, to haul around, and to get sited and permitted." With a small footprint and 2 MW of output, "It's not this ‘monstrously big engine'—not that those are bad, but those are harder to deal with," he says. ARES generator sets can run in island mode (i.e., temporarily detached from the main grid). They're also doing well, he says, in combined heating and power (CHP) applications.

By comparison, domestic marketers must traverse a thicket of state-by-state emissions regulations, which at times make it difficult to site and permit new technologies. Some of California's current restrictions on NOx are so tough that, Gerber says, without ARES technology using available emission control technologies, DG "can no longer really be economically sited there" except for certain unproven, costly, and comparatively inefficient products.

The first-phase ARES engines may prove to be a satisfactory solution to air-quality regulators in non-attainment regions. However, that remains unresolved to date. In any case, the NOx output is now shaved down to just 0.5 g/bhp-hr—one-fourth the emissions of a few years ago, and approaching the output of small gas turbines.

Coming Up: Still Lower Emissions
Complying with pending air standards in places like Los Angeles, Phoenix, the San Joaquin Valley, and other trouble spots is now all-important to a successful future for the ARES program, says the DOE's Fiskum. "That's our goal," he notes. "We're putting most of our efforts into reducing engine emissions, so you can place these engines in California" and other environmentally sensitive areas.

And, as was the case in making a push for power density and efficiency, the quest to slash engine exhaust emissions down to trace levels is likewise broad-based and intensive. Again, university labs are exploring multiple avenues at once, including exhaust aftertreatment with two-stage catalytic reduction, selective NOx recirculation, lean NOx catalysts, improved sensors, and active flow controls. ORNL's Theiss makes note of particularly encouraging results with a lean NOx trap being developed and getting "very good NOx reductions," albeit in a lab setting. A next step will be "to figure out how and why it works so well," then to publish the results. "Perhaps more than the device itself," he says, "this is going to be particularly interesting to the industry."

Caterpillar's cleaner exhaust efforts are focusing on leaner fuel mixtures to lower combustion heat, thereby reducing NOx formation. Caterpillar has also researched a stoichiometric clean exhaust induction three-way catalyst, which is achieving an unprecedented 0.1 g/bhp-hr output, and less. That's one-fifth of the NOx output in the new G3500C line.

Another cleansing effort involves applying digital electronic optimization of the air/fuel ratio mixes. NOx control is sometimes made tougher due to fluctuating ambient humidity and pressure conditions; by reducing this variability, notes Gerber, Caterpillar will be able to improve the control process and eliminate the need for some sensors.

Finally, on the immediate horizon the ARES consortium looks ahead to supporting the DOE/CEC second annual conference, to be held March 15–16, 2005, in Diamond Bar, near Los Angeles. In alignment with the theme, "Moving forward in low-emissions and high-efficiency technologies," attendees will share information on current and pending breakthroughs in cleaner emissions technology, and strategize on meeting goals in the second phase.

The choice of an LA meeting location is something of a master stroke too: Hosting the consortium will be none other than the South Coast Air Quality Management District (SCAQMD), which has often voiced opposition to power permits region-wide. The up-close encounter between ARES members and SCAQMD may well turn out to be a sort of linchpin for shaping the future for gas-fueled generation. On this, the DOE's Fiskum observes rather dryly that if ARES' successes in lowering emissions are repeatedly spurned in the Western states, it will soon become tough for consortium members to keep funding the critical R&D. "All of this," he points out, "is not ‘just for fun.' It's for California … a major market. We're trying to do the best we can to meet their needs."

The ironic and undesirable outcome might be this: that West Coast air-quality regulators, by not recognizing the larger environmental advantages of CHP yielding minuscule NOx emissions, might inadvertently thwart some critical breakthroughs in the US that could soon be reaching a global market.

For its part, the DG industry, says Fiskum, must continue stating its case to regulators in Diamond Bar and elsewhere as compellingly as possible. "We hope we can turn them around," he says. "That's part of our job too."

La Mesa, CA–based writer DAVID ENGLE specializes in construction-related topics.

DE - March/April 2005