An ESCO turns a problem-ridden site into an energy-efficiency showcase.

By David Engle

The end of this combined-heating-and-power (CHP) tale is so much better than the beginning that it’s best to start with the last and then come back. Consider these happy outcomes:

• Five years after the commissioning of two 750-kW Waukesha reciprocating engines in June 2002, the Greater Rochester International Airport (GRIA) of Monroe County, NY, now generates about 90% of its electric power (1,160 kW–1,450 kW) and saves $500,000 yearly on its electric bills. This latter figure is guaranteed under an energy services performance contract (ESCO). (Ah, but there’s a catch: the Waukeshas running now are not the originals; more on that later.)
• Exhaust heat from the engines warms a water loop, which circulates the length and breadth of the airport concourse. Passengers and employees stay warm and comfy in winter and in summer receive the benefit of an exhaust-heat-fired absorption chiller yielding about one-half of the site’s cooling need. Winter CHP efficiency comes to an impressive 87%, and summer cogen efficiency—when expensive cooling load is offset—is 59%.
• Besides CHP, other energy-saving measures are also shaving costs. These include lighting retrofits on the tarmac and in the concourse (T8 fluorescents and pulse-start metal halides) with photocell on-off switches in daylighted areas where the code permits; high-efficiency air handlers; variable-speed-drive pumps; chiller demand controls; and operational strategies.
• Total overall energy consumption has been slashed about 47% (despite an additional load added by 9/11-related, beefed-up security and new baggage-handling equipment); and the GRIA now enjoys a more favorable utility rate classification.
• There’s now improved backup power, with the grid running in parallel with the plant. The inconvenience of recurring power outages—once fairly common—is now virtually eliminated.
• Annual reductions in carbon-dioxide emissions are calculated at 2,260 tons (equivalent to 385 autos and 226,000 gallons of gasoline).
• Of the project’s total $2,500,000 capital cost, about $500,000 was provided by the New York State Energy Research and Development Authority’s (NYSERDA’s) CHP Demonstration Program. Another $357,067 was provided under NYSERDA’s Commercial Industrial Performance Program for the energy-efficiency measures, and $25,000 helped fund Web-enabled advanced monitoring of utility consumption. Total NYSERDA contracts awarded add up to about $900,000.
• Payback of Monroe County’s $2 million capital outlay is guaranteed within 10 years of the project’s 2002 launch (i.e., by 2012) and is currently expected in 2009.
• Thanks to the combined efficiencies realized, this outlay is being funded from existing revenue streams, without requiring cuts elsewhere or raising taxes.
• Another cost-saving benefit is that the purchase of a CHP system enabled the GRIA to avoid the cost of multiple emergency-only backup diesels, which sit idle most of the time. Instead, the airport owns clean-burning natural-gas engines that run almost continuously, earning their keep.
• Due to the perseverance and success at the GRIA of the project’s vendor-developer, Siemens Building Technologies Inc., the firm subsequently has flourished in the adjacent communities, equipping cities, industrial sites, farms, schools, and universities, and partnering extensively with NYSERDA to lower the region’s energy costs, reaping millions of dollars in revenues.

One of two skid-mounted, 750-kW reciprocating engines is delivered to the Greater Rochester International Airport.

For its part, NYSERDA also gained its several objectives. The agency’s broad mandate during the six years that it has been underwriting CHP has been, as NYSERDA Project Manager Scott Smith explains, “to build the marketplace by developing a portfolio of projects illustrating best-in-class applications, and to tell what we’ve learned ... what works, what doesn’t ... and what ‘bumps’ we encounter along the way.”

In this case, he adds, the 1.5-MW, high-efficiency, high-profile, 375,000-square-foot airport cogeneration project “filled a spot in our portfolio” for a good-sized public-sector plant. “As proposed, it met our efficiency targets,” he says.

Third, the “energy-reliability aspects” were a selling point, providing power during grid outages.

And finally, he says, “We were also interested in telling the story of the contracting mechanism”—the vendor-guaranteed savings and risk avoidance. The prospect of underwriting a vendor who would ensure customer savings with high energy efficiency looked like an important demonstration model to encourage.

The second of two Waukesha engines is installed at the airport.

When “CH*P Happens”
As noted above, though, this promising cogen project and its eventually successful conclusion did not begin auspiciously. So now that you know the outcome, it’s appropriate to go to the beginning.

In 2000, energy expenses for Monroe County government services were rising, but revenue streams were flat. For instance, the airport draws 2.12 MW of electricity, burning 7 million Btus of gas for heating and 12.5 million Btus for cooling its round-the-clock operation.

Raising taxes would be one solution—but, of course, that’s never popular.

At about the same time, NYSERDA announced the availability of selective funding to help pay for high-efficiency onsite cogen power. Thus, the timing of the county’s need, and the state’s offer to help pay for good projects, coincided perfectly.

The GRIA’s energy load could be efficiently carried by installing a plant sized at 1.5 MW. The airport’s physical layout—being served by two electrical feeders for an east and a west terminal—dictated two 750-kW natural-gas engines (Waukeshas were selected), one for each wing, along with a 300-ton absorption chiller.

This array, Smith recalls, “sort of struck a balance between trying to maintain a really good efficiency to preserve economics and having enough power available during an outage to run critical systems, keeping the airport functioning.”

Groundbreaking
As with any construction project and especially with CHP, difficulties were encountered before the construction was completed.

For example, not long after the hijacked aircraft struck New York City and the Pentagon on 9/11, extra-heavy security was imposed at the GRIA. Restrictions became so onerous to construction work, an airport official later remarked, that if 9/11 had happened before the contractual agreement had been reached, the deal would probably never have been signed.

At any rate, each Waukesha arrived, along with custom-designed, 18-foot-by-5-foot-by-1.5-foot skids made of two I-beams and cross-connecting braces, as a former Siemens service account engineer recalls.

“The generators,” as he describes them, were “bolted to the slab [the skid] with the engine sitting on top.” Also attached and configured were a 7.5-horsepower pump, heat-exchange plates, and assorted plumbing, tubing, controls, sensors, and fixtures. The total weight was about 29,000 pounds with everything on it, all resting atop 4-inch springs.

This skid, with its integrated-CHP component bolted in place—all fabricated by a nearby engine dealer rep—is common today. But, as the rep notes, “It was an innovation at the time,” and, being on the cutting edge, engineering design and know-how for it was still evolving.

Concrete pads for each skid package were then poured next to the two terminals, and small, weather-tight enclosures were erected.

Piping to carry hot water to a second-floor chiller unit was affixed to the building’s exterior.

Fully automated controls were added to the building-management system (BMS).

Interconnection with the local grid yielded unexpected results.

An absorption chiller, rated for 300-ton output, uses exhaust heat from the two generators to provide summertime cooling.

Total year-round fuel efficiency of the airport’s CHP is typically more than twice that of the power-only application.

Grid interconnection followed. Whenever the grid might fail (as was happening several times a year), the Waukeshas could “keep on ticking” in island mode. Once power returns, there’s a manual transfer using Kirk-key interlocks—a utility-mandated safety precaution—instead of being automatic. Light-emitting-diode indicators at the main breakers monitor the parallel status, again for safety.

At commissioning, everything was thoroughly tested in phases, and many adjustments were made, Siemens later reported.

But almost immediately, challenges presented themselves.

And they were not easy to fix. The entire project team of manufacturers and designers “worked together to solve the problems,” notes Smith. “In that time they lost fuel lines, valves, and engines and eventually had to have a full replacement of both units by the manufacturer.”

What were some of the challenges? Here are several, major and minor (in no particular order), which, incidentally, are not atypical of CHP projects.

Inadvertent Power Export
The Rochester Gas & Electric (RG&E) grid voltage, as it turned out, occasionally sagged below 480 V; meanwhile, the airport’s new power plant held steady. To safeguard against an unwanted outflow of current from the GRIA to the grid, switchgear at the airport was designed to automatically shut down the cogen system if necessary.

“The concern was that it would run backward for a long period of time,” recalls Siemens Energy Engineer Bert Spaeth, noting that this is because, in a parallel hookup, voltage goes from the higher-output source to equalize the lower. “This would present public safety issues. But our configuration would cause the system to shut down to avoid that.”

Who was at fault?

RG&E and Siemens discussed what, why, how, and who needed to find and correct the voltage irregularities.

Finally, Siemens—in order demonstrate and precisely quantify the issue empirically—ended up purchasing and installing ultra-sensitive Dranetz-BMI meters, which indicate even tiny drops and spikes in volts and amps. These proved that all the voltage lags were on the utility side. RG&E got it straightened out after that, but only after more shutdowns had plagued the airport’s power reliability.

Standby Power?
As mentioned above, the two gensets were meant to keep things running in case of a blackout. In this role the Waukeshas replaced two 80-kW backup diesels that would have provided minimal juice for security, emergency lights, and other critical functions.

In thorough precommissioning testing to simulate power outages, the two Waukeshas came on and islanded perfectly, time and again.

Thus, it turned out to be more than a bit ironic and disconcerting, when, in August 2003—amidst the notorious blackout that left tens of millions of power customers in the dark—one of the GRIA’s generators just happened to be “down for maintenance,” Smith recalls.

Although the other worked fine throughout, “The airport did not have full power in the blackout like they would have wanted,” he says. “They did have some power—which would not have been the case before this project was installed,” he notes. “But one of the drivers of this project—as with a lot of CHP—is increased reliability.”

In its first big reliability test, the system was less than a total success.

And the root cause was simply a case of bad timing and terrible luck.

The real lessons to draw from this, Smith adds, are several. The first, he says, is the fact that routine maintenance needs to be done—“And there’s a chance that it will coincide with a reliability event.” This seemingly remote possibility is nonetheless something to plan for—meaning, to the extent possible, that operators should schedule maintenance downtime with some thought given to potential threats to reliability—i.e., don’t do them when storm systems are on the Doppler.

The second lesson is that project managers should develop the art of “expectations management” with clients, explaining to them that, for example, despite their having made the onsite power investment and despite having purchased for themselves what is statistically higher reliability, stuff nevertheless still happens. “They need to be aware,” says Smith, that occasional glitches, “adjustments, and even changes in hardware are all quite normal.”

In this case, airport managers were forgiving. But at the county level, a few were taken aback by the imperfect performance. Thus, Smith suggests, it would be worthwhile for project managers to go over with clients exactly what kind of energy surety they’re getting. Even though cogeneration is properly regarded as a “reliability enhancement,” there are, he notes, varying levels of reliability to be calculated, depending on the system configuration. For example, one strength of the GRIA CHP system design, from a reliability standpoint, is its two-engine configuration. “If one engine is down for some reason and grid power is lost—as in the case of the August 2003 blackout—the airport still has power,” Smith says. If system backup is not in place, a client needs to understand that “there’s a far higher likelihood that you’re going to have a reliability event at some time,” he adds. And this should be planned for.

The good news, despite the slight disappointment in 2003, is that during other brief grid outages since 2002, the GRIA has remained fully energized and functional without needing to run diesel backups.

But there is a third, more vexing issue.

Getting Very Bad Vibes
The skid-mounted system itself turned out to be, as Siemens recalls, the project’s most serious challenge. “We had,” the company’s former employee says, “numerous things malfunction from the get-go: broken water lines, oil and glycol leaks, loose wiring,” and failures of sensors and control settings.

These elements failed individually, sequentially, and with frequency that troubled both Siemens and the airport.

Months of troubleshooting ensued, and ultimately the root problem was traced to the skid design itself.

Experimental alterations in design and eventually a complete rebuilding followed, along with assorted reparative strategies, until—after virtually a complete re-engineering and multiple parts replacements—the problem was finally licked.

The silver lining here was that major design improvements were implemented by two major engine manufacturers, the former employee reports.

Putting Out Bad Data
Falling in the category of annoyance more than disaster, the data collection system—needed to maximize efficiency and savings—was spotty.

Two such systems are in place. One gauges the electric utility usage; the other records gas inflow, electrical output, and heat recovery.

Meters and sensors are wired into an energy-management system (EMS). Data are logged in 15-minute intervals. Daily and monthly summaries are then tabulated and provided to the county to show the usage averages, peaks, kilowatts, kilowatt-hours, and thermal efficiency; and now it’s all Web-enabled.

In the early days—as Siemens later reported this problem to NYSERDA—the data simply weren’t making sense. “[I]t became apparent that something was wrong with the heat-recovery information. The system-supply temperature was low,” a report stated.

Investigation followed. As it turned out, the specified temperature gauge was the wrong one for the job, and it was not picking up the engine exhaust heat. A technician rewired it, and the system has since registered correctly and is producing water 10 degrees warmer on the supply side. The problem was solved (except for occasional short lapses, which are readily correctable by a work-around).

When Contracts Protect Clients
Although the GRIA indeed suffered multiple inconveniences, as a business proposition these costly repairs were ultimately covered by the vendor. Thus—in view of those multiple upbeat points noted at the outset—Smith observes: “The airport is still satisfied with the project.” The days of repeated breakdowns were annoying, he says, but “ultimately they [the county] were served well by the energy services agreement with Siemens.”

It took a long time to get the CHP system running smoothly, he adds. “But I think that even now they’d say that, in the end, after a lot of hassle and troubleshooting, they got what they wanted from the primary vendor.”

Monroe County Executive Maggie Brooks concurs. “This partnership has been a positive experience that has met our expectations to produce energy and reduce costs,” she says.

As of March 2007, she adds, the county plans to embark on a renewable energy plant at its Mill Seat Landfill to yield electricity from methane.

Spaeth adds, too, that Siemens is still performing top-end overhauls and other maintenance for the GRIA, as well as for several county sites that were developed soon afterwards; some enjoy guarantees as long as 18 years.

On that score, a district power system in Rochester, NY, came online to energize Monroe County Hospital and the community college in May 2004. The plant yields about 10 MW of steam cogen power and uses Caterpillar gensets.

Additional projects that blossomed from the GRIA job and other Siemens trailblazers include a parallel-grid nursing home in Cortland, NY—where three 600-kW reciprocating engines and a diesel backup provide all hot-water heating and potable water from recovered engine exhaust heat—and schools in the nearby towns of Depew, Eden, and North
Tonawanda, powered with 150-kW and 300-kW engines, some on the grid and some off (as determined by utility tariffs, which can still be punitive to onsite projects, Spaeth notes).

All in all, Siemens is picking up lots of business.

Through it all, NYSERDA’s help in capitalizing projects is a most welcome catalyst, adds Spaeth, who coordinates Siemens’s growing portfolio with the agency. Lowered interest payments, he says, “help on payback and rate of return as well.”

NYSERDA requires contractors like Siemens to do several things, such as publish performance data that can be generally useful to the CHP industry. Would-be adopters can gain increased confidence by viewing empirical performance over time.

Yes, it is more paperwork, Spaeth says, but well worth doing to get “another set of eyes and an engineering review. And it gives a lot of validation to your project when you have NYSERDA backing it up.”

	Sick Skid: The Patient's History

Engines Purring; Capital Growing
Meanwhile, the Siemens maintenance team is accumulating critical know-how enabling it to give designers feedback on avoiding future errors and on improving operational performance. As the former Siemens engineer (who once oversaw 12 engines) notes: “Every time we build one of these things, we learn from previous experiences and we put that into the new design.”

A few examples of skid design changes:

• Controls (they’re too vibration-sensitive) are being removed and remounting off the skid.
• Multiple vibration-dampening efforts are being undertaken.
• Skids are being specified with very rigid mounts.
• Siemens isn’t over-relying on the manufacturers’ guidance.
• Smaller, multiple engines are being specified.

Obviously, the bigger the engines get, the more the vibrations. And they’re throttled back to run at 1,200 rpm instead of 1,800 rpm—producing “a huge difference,” he notes.

To compensate for the reduction in power, more engines are being specified (e.g., two 500-kW engines running at 1,200 rpm replace one 750-kW engine doing 1,800 rpm). But the costlier strategy works because equipment life is lengthened and the far fewer maintenance intervals “make it pay back pretty quick,” he suggests.

NYSERDA’s CHP project manager sums up: “Regardless of what engines are used, no CHP application is simple,’’ Smith says. And yet, engineers and clients alike continue to take the performance of these custom-designed projects for granted. Even though the application of a given engine may be repeated successfully many times, onsite power generation remains, he says, “a complex installation ... an increment above the complexity of even a chilled water plant. And there are always potential issues that will arise.”

La Mesa, CA–based writer David Engle specializes in construction-related topics.

DE - July/August 2007