Booming growth means soaring electrical demand—but raises the question of how to deliver the needed watts over already-jammed lines. Distributed energy (i.e., putting generation near the users instead of far away) is increasingly the best or only solution. And the “icing” to sweeten the value, in many DE applications, is that the engine’s exhaust can be used and reused locally for steam to heat and cool. In such cases, not only are transmission bottlenecks avoided, but plant efficiency zooms to perhaps double or more.

Even so, it’s rare for new power stations to be permitted and built near urban centers; besides the usual gauntlet of strenuous local objections they must surmount—the local aversions to smokestacks, constant noise, and assorted other environmental and aesthetic impacts—there’s simply the issue of paying higher in-town land and construction costs.

Who would have imagined, then, that a new plant proposal in an unusually sensitive, activist college community would not only overcome these obstacles, but ultimately would win strong approval from city government, the neighborhoods, and even environmentalists?

That’s indeed what happened recently when the University of Wisconsin at Madison decided it needed more power, then embraced a proposed joint-ownership with the local utility. Under the plan, the campus would get the steam, and the utility the power. After some creative wheeling-and-dealing—including some highly innovative solutions that would help offset plant emissions dramatically, and minimize or eliminate environmental impacts—the Madison community is arguably enjoying healthier air quality as a result. It is getting energy with the highest-possible cogen efficiency one could ask for, and it can boast of having the cleanest power plant in the state. In short, it’s a win-win-win all around.

Energy Synergy
Old, stately buildings amidst picturesque waterways, blending new research complexes with hives of multistory dorms: the UW campus, located at Wisconsin’s state capital, probably epitomizes the image of a bustling Big Ten school. A recent construction boom in Madison has added several big “high-energy-using facilities,” notes Bob Stoffs, who handles community affairs at Madison Gas & Electric Co. “The university,” he adds, “has already grown considerably and plans for a lot more.” Obviously, more heating and cooling would be needed.

As for electricity demand, this too has been edging up 2%–3% a year consistently. This will translate into scores of added megawattage needed to meet recent and future growth. The synergies derived from adding power generation and tapping the resulting exhaust for campus steam cogeneration were obvious, Stoffs says: “It was just a natural fit.”

From the perspective of MG&E project manager Don Peterson, who would oversee the undertaking, a most appealing facet was the prospect of using virtually all of the available exhaust heat to raise plant efficiency “up to over 70%.” This obviously beats the 40%–45% electrical conversion typical of the best single-cycle plants. Moreover, combining production of the campus’ steam with the utility’s power would, of course, be easier and cheaper to maintain. And cogeneration would slash total emissions: Reusing the engine exhaust would reduce CO₂ (“greenhouse gas”) by 15%, and NOx by up to 80%.

To generate needed power and heat, two natural-gas-fueled GE LM6000 (rated 43 to 47 MW) aeroderivative gas turbines and a SAC4 auto extraction steam turbine would nearly match the projected load. The total yield in power and heat—150 MW—would provide electricity for up to 45,000 Madison homes. Steam at 500,000 lbs per hour would suffice for several university buildings and, for summer cooling, would also produce a chilled water capacity of 20,000 tons. MG&E would buy and install the engines, and the university would contribute its part by housing the plant near an existing coal-fired heating station on Walnut Street. Fortunately, with 4.5 acres already set aside for such an expansion, the real estate issue was neatly solved. Again, joint ownership meant that MG&E would get the power-generation assets of the new West Campus Cogeneration Facility (WCCF), and UW-M would own the steam.

Finessing NIMBY Factors
It was a perfect onsite match for the utility and its big campus customer. But the two turbines would require smokestacks and attendant exhaust, however well contained the latter might be by the best-available control technology. And all of this would be positioned near campus housing and other residential neighborhoods. A sizeable and very noticeable power plant would also arise within the studious community, perhaps marring the university ambiance. The high-pitch whine of turbines and hiss of steam release valves would presumably be constant. These are typical apprehensions evoked by power-plant initiatives. In this case, too, there were fears for safety, health, and property values. MG&E realized the proposed WCCF might stir “not-in-my-backyard” resistance. Stoffs recalls: “It got pretty clear, early on” that the utility should sit down and meet with all parties—environmental groups, neighborhood associations and the city of Madison—“to negotiate how could we make this new plant, and this is kind of expansion, more acceptable in the community. ... We knew,” he adds, “there would need to be, if not concessions, at least we had to be very careful about what we added to the environment in terms of emissions and impact.”

To address this, the utility began holding public meetings, presenting the proposed plan and explaining why heat-and-power was the best solution. In these, audiences learned, for instance, that the turbines would burn clean natural gas—which would eliminate the heavy metals, ash, and SO₂ associated with older coal-burning plants in the region. Secondly, state-of-the-art selective catalytic reduction (SCR) would reduce NOx emissions to the lowest levels technically achievable. Catalytic oxidation would remove CO, as well as volatile organic compounds (VOCs) and greenhouse gases. Thirdly, for backup fuel the plant would stock ultra-low sulfur diesel. Bottom line: the new power generation would not exceed a minuscule 2.5 parts-per-million NOx. It would thus record the lowest emissions of any plant in Wisconsin.

This was a “hit,” but, to top it off, the utility went a huge step further with the community by proposing to offset, as much as possible, the additional NOx and CO that the WCCF would produce—low as it would be. This offset could be put on the table in the form of a dozen new initiative the utility would introduce to reduce emission from other operations and community pollution sources. The cumulative effect would leave a major dent in the most unhealthy kinds of emission. In fact, they would achieve a reduction impressive enough that the effort would, in large measure, negate the new plant’s NOx and CO.

“What we agreed to do,” Stoffs explains, “was basically to net-out the emissions from the plant for the major regulated kinds of emissions.”

Among the corrective measures MG&E and UW-M offered were plans to:

• Improve the equipment and processes at a regional coal plant (Blount Station) so as to allow burning consumer paper packaging as a fuel. This would not only reduce fly ash and other coal emissions but would provide an efficient incineration disposal of a waste material.
• Use new operational dispatch strategies which would help offset the new emissions.
• Provide $200,000 to the city of Madison to underwrite ultra-low sulfur diesel (ULSD) fuel for Metro Transit buses, implementing this a year before it would become mandatory. (ULSD reduce SO2 by and estimated 97% small particulates by 8% vis-à-vis regular diesel.)
• Also fund $200,000 in local renewable energy projects.
• Install pressure-vacuum vent caps at 50 large gas station storage tanks in Madison, to control vaporous VOCs —a major precursor of ozone.
• Provide Dane County residents free gas can caps designed with automatic shutoff valves and closures; applying these would significantly reduce VOCs. As a result, Stoffs recalls, “The university gave out a large quantity of gasoline cans that seal very tightly...and caps for residents in the area to use on their lawn mowers and [so on] to reduce VOCs.”
• Track small particulate pollution (i.e. PM 2.5) by setting up an air-monitoring and reporting station on Madison’s west side. PM 2.5 sources include traffic exhaust, industrial processes, power plants and especially diesel-powered buses and trucks. Reports are posted online at www.cogenadvisory.com and are cited for community educational and environmental health.

Peterson adds: “This air-monitoring station will help residents get a better understanding of PM2.5 levels in their neighborhood.”

All of these steps and proposals the utility and university put in writing to the community groups, so that, by the time the public-hearing process was complete, virtually no opposition remained; on the contrary, support was strong.

Plant Particulars
GE Aero Energy Products of Houston, TX, is a leading supplier of aeroderivative gas turbines for industrial and marine applications; the company is advertised as “the world’s largest and most experienced aeroderivative gas turbine service provider.”

A sizeable and very noticeable power plant sprang up within the studious community.

As noted above, natural gas is the engines’ primary fuel; backup is provided by ULSD, should the pipeline fail. For maximized power output in a wide range of ambient temperatures, each turbine is equipped with a mechanical chiller.

Besides installing two turbines and generators, Aero Energy’s package included a heat-recovery steam turbine, condenser, steam-turbine generator, transformers, two 250,000-gallon water tanks, two natural gas compressors, and assorted component. Technical advisory services and training for a largely automated plant (employing sixteen workers) were provided. Total cost: about $180 million.

As a regulated utility project, payback occurs in the typical regulated fashion, but with a notable difference: The plant is actually owned by a nonregulated subsidiary, which leases it to MG&E on a long-term agreement. As Peterson explains, this enables amortization of rates over a much longer period, thus adding an element of “intergenerational equity,” as the utility calls it. Current customers will not be saddled with a disproportionate burden for cost-recovery (as had often occurred in the past). Peterson explains: “If you look at regular utility accounting, it really socks most of the cost to the customers who are there in the first years of the plant.” Plants often remain productive for several decades after debts are paid off, at which time, future ratepayers reap an unfair benefit. Thus, he says, “by... leasing it we level those payments by ratepayers and reduce the rate shock of the project.” Earnings are of course regulated by the Wisconsin Public Service Commission.

Heating, Cooling, and Steam
Electricity, steam and cooling were commissioned in phases from April to November 2005. Pre-existing steam and chilled-water loops were in place on the campus, as was a gas main. Hookups were thus “pretty routine,” says Peterson. Piping is divided into two systems, and the new WCCF happens to sit at the juncture. “We intersect into two chilled water lines,” he says, with 42 inch diameter pipes fed by a 36 inch chilled water line.

A similar crossing-point joins two steam systems, “one for the east and one for the west sides of the campus,” Peterson says. The 500,000-lbs.-per-hour steam output is now powering new research laboratories dedicated to interdisciplinary research between medical, pharmacy, nursing and other biological sciences. Steam provides their climate-control, humidification, autoclaves, and distillation. Thanks to the additional steam generation, there’s ample supply to accommodate a program that will eventually more than double the heating and cooling load.

One operational challenge arising from the WCCF has proved to be that of balancing and managing the relatively extreme swings between peak and baseline steam loads. Of course the power output is steady and continuous. But the resulting steam load is a different story, as Peterson explains: Average loads in relation to their peak loads “are fairly steep,” with the baseline being quite low. By comparison, he notes, running this same plant at an industrial site would likely yield a continuous, more easily managed steam load. Here on a campus, though, utilization largely depends on the finicky weather and seasonal extremes. At times, the steam isn’t needed at all. But during cold weather and intense load periods, the campus will need all the steam it can get, and the grid needs all its available power. So, he says, “As we were evolving the design of the plant, we found it was more economically efficient to add more duct firing [i.e. additional heat for steam—beyond what is yielded by recycled exhaust heat] to give more generation capacity...” Duct-firing, he notes, is a common way of boosting power to get “a lot more steam, for not a whole lot more capital cost.” Although plant efficiency declines because the added fuel goes to make steam but not more electricity, “if you’re only doing it for a few hours a year it become economically an efficient way of doing things.”

Similar peak-and-baseline and efficiency issues came up with the chilled water. Historically, the university has relied on steam-driven chillers. There was an initial assumption this would continue. But an engineering analysis revealed that steam chillers “are not very efficient,” he says. It makes more sense to use the steam to produce more electricity—then, “use that power inside in very efficient electric-driven chillers.” At present, chilling output is already 20,000 tons. Over the next eight years this will rise to about 50,000 tons of chilled water; electric rather than steam-driven chillers will likely provide all.

Alternatively, absorption chillers (which can also be powered by steam) were evaluated as an option, but this was rejected primarily due to the amount of chilled water that we would be needed. “Absorbers are problematic because you need a lot more tower water,” he notes. The in-town power plant faces environmental restrictions on water usage—and the steam boilers are already drawing high volumes. For that matter, the water-using cooling tower sits atop the power plant rather than on the ground, in order to conserve real estate in the urban setting. “We’ve got this massive steel structure that we have built inside the plant to support all of the weight of that water on the roof,” he says of the atypical arrangement. There’s a question of where and how future towers would be constructed, if at all. At this point, meeting the future demand for cooling most efficiently remains something of an open-ended challenge.

Water Supply, Noise Abatement
Obtaining a million gallons a day for steam and/or cooling—and up to two million in summer— presented still another logistical problem. The urban setting and its environmental restrictions, too, rendered this, more difficult.

A ready source sits nearby at Lake Mendota, but such a volume of water removal it would need to be replenished—and the adjacent waterways are already being impacted by the local construction boom and increasing usage. Moreover, drought periods severely impact some waterways, while at other times in the year, water levels are quite high.

Thus the WCCF is being supported with a novel system of pumps and conduits to circulate water as needed, while also preserving the delicate ecology, adjusted seasonally. Lake Mendota’s water is drawn out in million-gallon daily volumes, but then replenished. A well is tapped and its water pumped into the nearby Yahara River. Stoffs notes: “At times, when we’re taking water out of the lake we may be affecting that downstream river habitat.” So this, too, is addressed by a groundwater well which the utility constructed for pumping water back into the river. There’s also a collection system for stormwater runoff; this is filtered and reinserted into the groundwater. During drought the pump increases the lake water replacement. At any rate the cumulative effect is to balance and maintain the local waterways in all seasons.

A final issue should be mentioned: Stringent noise ordinances required measures to keep sound-levels below 60 dBA at the property line, notes Peterson. This necessitated installing critical grade silencers on major equipment, and a special concrete stress panel used, he says, for the siding or the cladding of the building. “It’s a sandwich panel using a couple of inches of concrete, a couple of inches of Styrofoam, an inch or two of concrete, and then a decorative finish like brick veneer or acid-etched concrete.” More veneer covers the stress skin panel and dampens the noise further, he adds. “And we’ve gone to a special silencer made in Austria, called Glaunach, which is ... for our safety,” he says. “So,” he sums up, “if we happen to have an over-pressure [steam] situation in the middle of the night, we don’t wake up half of the neighborhood by blowing a safety at three o’clock in the morning,” adding: “With onsite power in the urban environment, residential areas, sound and mitigation of the noise is always an issue.”

All in all, as a kind of hybrid between central and distributed power, the WCCF plant is, Stoffs notes, “an extremely unusual arrangement.” Only one other similar university-utility cogen partnership of this kind—a much smaller one—can be found, at the State University of New York. Even if the concept hasn’t caught on yet, it probably makes eminent sense, he says, and could for suitable at potentially dozens or scores of collegiate locales.

In Madison, one key catalyst that made it all “go” was, of course, the community buy-in. In this regard, the activism of local environmentalists—contrary to stereotype, perhaps—actually helped. The Sierra Club members, for example, were already conversant in some of the technical issues with DE, on emissions and energy efficiency, Stoffs says.

The group was already favorably disposed to distributed generation, especially for its cogen efficiency—even though, in this case, the result would entail a considerable physical structure, residing in town.

Moreover, the WCCF’s NOx emission were perceived to be, relatively speaking, perhaps less noxious in health terms than the potentially more harmful effects already emanating from PM sources elsewhere, citywide—source which MG&E and the UW-M offered to combat as compensation.

Being confined into an uncharacteristically small parcel for such plant—a mere two 2.5 acres, and scant space for construction—also posed challenges that a more bucolically sited facility would not have encountered. However, solutions to this and other challenges were also devised, such as putting the cooling tower atop the roof, and installing state-of-the-art noise abatement. Despite some of the unusual challenges that were overcome, as Peterson notes: “We were able to bring the project online and meet our timeline, and ...bring it in on budget as well.”

In recognition, the WCCF recently received a Governor’s Award for Environmental Excellence; an Energy Star award from the US Department of Energy is also pending.

MG&E knew that a rural plant might be easier to build. But, says Stoffs, the combination of cogen efficiency, no transmission barriers, and lower overall emissions made the urban site a more intelligent decision. “We went right to this solution,” he says, especially for the cogeneration gains. He sums up: “If you’re going to generate power at a distance, obviously the heat value is likely to be lost. You have to have the load and the demand in the same proximity, in the same place. The only way you can get all that extra use out of the fuel is to have it onsite.”

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

DE - July/August 2006