“We have mostly looked at solar,” says Lyn Peters, Environmental Services Manager at the Fresno Unified School District, “but not that seriously. We’ve investigated it in the previous five years, but solar energy requires a lot of space. To have solar rays, you need a lot of acreage or rooftops or some other space to keep them away from kids playing.”

So when an engineer approached the district with the concept of cogeneration systems in 2000, it seemed like a good idea. The project involved three high schools—Hoover, Sunnyside, and McLane. The cogens installed on each campus to produce electricity to the school’s grids were reciprocating engine generators—low NOx internal combustion engines that run on natural gas.

Before the installation, the district had a standard power set-up—electricity and gas supplied by Pacific Gas & Electric (PG&E), and gas by SPURR. The only cost savings they had in place were some remodels and upgrades in their lighting and HVAC systems. The idea was that the cogen system would provide the baseload power that the utility required per day. “This would help the district manage their purchase power costs by limiting the demand costs the utilities charged on peak power,” says Pat Hale, national sales manager at Yazaki Energy. “In addition, it allowed them to recover the heat that would normally go out of the exhaust pipe when the generators burned the fuel, as well as recover the heat from the water flowing through the engines to cool them.”

“Two of the schools, Hoover and Sunnyside, have basically the same set up,” explains Strategic Mechanical’s Lonnie Petty, the project manager who was also the lead on this project. “They each have three Tecogen gas generators (also known as Tecos) that produce electricity to the school grid. The waste heat is taken from the Tecos and the pools are heated as the first priority.” The second priority is to heat, at Hoover only, the domestic water with whatever heat is available. Then the energy that’s left over from the pools is used to supply heat to the campuses themselves.

At Hoover and Sunnyside, along with the three Tecos are one pool heat exchanger and two chillers. At the third and smaller school, McLane, there are two Tecos and one chiller. All the chillers are Yazaki absorption chillers, models WFC-SH30 and WFC-SH20, which provide both cooling and heating. All of the Tecos are 75 KW at 460 V.

“As far as cooling for the schools is concerned,” says Petty, “the waste heat from the Tecos is run through the Yazaki absorption chillers and that heat generates chilled water for the campus air conditioning system. The chillers provide about 50 tons of free cooling this way.” The smaller school, McLane, however, only uses a single 30 ton chiller. Sunnyside and Hoover use 50 tons each, accomplished by using both a 20-ton and a 30-ton chiller.

The Main Players
Once the project was ready to roll forward, the plan was that the district would provide the engines for three cogeneration plants. The consulting engineer then specified what size chillers he wanted, how the wiring and plumbing would be done, and other such details of the design and installation. Once the specs were written, the district put out a public bid.

The winning team for this project included sales engineers from Norman S. Wright Co., Lonnie Petty of Strategic Mechanical as both the mechanical engineer and the lead, and Chuck Shinneman of Building Systems Engineering as the consulting engineer. Shinneman designed the plants, Petty was in charge of all phases of installation, and the Norman S. Wright engineers coordinated and facilitated activity and communication among the above parties, Yazaki, and the district.

Worth the Cost
So what motivated the district to go with this project? The short answer is long-term savings. After the engineer showed them how much they would save and how much the local utility would give as a rebate towards the cost of the cogen, they thought the benefits would mitigate the initial costs.

The total cost for the project was $4 million, so the district’s decision to follow through was obviously well thought out. “This wasn’t something where, at the time, they said, ‘This seems like a good idea so let’s jump on it quick before someone else does!’ “ says Hale. “It was a forcefully measured process that should yield very good results because of the time it took to plan it. There was quite a long period of research and design integration that occurred before installation.” It took about two years to develop a design and plans for bidding.

“Cost was a big concern,” shares Peters, “but the payback will come in about four years. Any payback under five years is good, especially considering the increasing cost of electricity in California.” The funding was attained mainly through a Certificate of Participation loan, a low interest loan available in California that’s usually granted for large equipment purchases. The engineers and cogens were paid for separately from the installation itself.

“I think it took great vision on the district’s part to take this approach to powering the schools,” says Hale. “From an environmental standpoint the cogen systems have great value, but they also help provide the very best facilities for the students. And the project helps protect the operating cost that taxpayers incur to maintain these facilities.”

Thinking It Through
Peters does not recall anyone at the district being opposed to the idea of using the cogens on the campuses. “I think there was a general reluctance at first, on every level,” she elaborates, “that had to be overcome because of the money situation. Questions had to be answered, and the first one was why is this economical? But I don’t really remember anyone being against it. It was presented over a period of time and during that time questions came up. They weren’t negative questions, just information-based, like ‘how does this work?’, etc. And as the idea developed, everyone was slowly for it.” It may have also helped that the technology itself has actually been around for quite some time, and as part of their research, the school spoke with businesses that have already been using the same cogens in similar applications.

Before installation, the district understood that their decision was a commitment, and that the power systems would have to be monitored regularly. “This is not something you just put in, walk away from, and treat like windmills, where the wind will keep blowing them around and around until an eagle flies into them,” says Peters. “They require and will continue to require a lot of TLC to keep them economical.”

The Technical Lowdown
In addition to the economic advantages the integrated building systems provide, they allow the school to recover—by means of heat exchangers—the heat that would normally go out of the exhaust pipe (when the generators burn the fuel), as well as the heat of the water flowing through the engines to cool them. This means the pools are now heated with the rescued heat instead of additional energy that would have previously been needed from the utility.

“The pools are heated by using Yazaki single-effect absorption chillers,” explains Hale. “Instead of being powered by electrical energy or gas or thermal fuels, these are actually powered by hot water. So the heat that has been produced for baseload power needs at the schools is now being used where it is needed in the most appropriate and most economical way.”

“When the chillers are satisfied and don’t need to run anymore,” elaborates Hale, “that energy can then be diverted to the pool. When it makes more sense to provide cooling, the energy drives the generators and—instead of dumping it into the atmosphere—it’s recovered and used to reduce the costs of the building. So they’re burning the match twice, so to speak.”

More Than One Hat
Atypical to most installations of this kind, the project manager, Petty, also acted as the GC on this project. He came into the picture after the project engineer designed the plants.

“It’s much easier to coordinate the other subcontractors this way,” begins Petty. “Since we coordinate it, we’re always thinking about the efficiency of the system. The building, slab, and block work is all incidental to the mechanical work, so when we’re the lead, it makes it easier for us to coordinate the subcontractors.”

Petty, who has experience being a GC in this way, notices that other subs like working for another sub. “That’s because we schedule a little better than some of the generals do. So many of the jobs in this project were mechanical in nature, so it was easier this way. Most GCs don’t really understand what the mechanical or electrical controls are in a building, and the controls in this case are very sophisticated. So it’s much easier for coordination purposes. We could also work directly with the owner, which meant one less layer of bureaucracy.”

Laying It All Out
On all three schools, a block building houses the Tecos and the heat-reclaiming materials. They also contain cooling towers and a radiator—a Young Touchstone—that takes the waste heat to the atmosphere when the Tecos can’t utilize the waste heat.

“They are at a location that is as close to the pools as we could get them and still coordinate with available space on campus,” says Shinneman.

For all three schools, the waste heat from the swimming pool provides space heating and cooling to the central plant heating and cooling systems (which goes to the campus rooms), and they have what’s called a two-pipe changeover system.” This means there are two pipes that run around the campus,” says Shinneman. “Whether the campus wants cooling or heating depends on the temperature of the water in them, which depends on the season or time of day. So we have the capability of providing either hot water for heating or chilled water for cooling, in addition to heating the swimming pools.”

One of the outstanding aspects of this project is the efficiency and versatility of the Tecos. They provide up to four thermal sources for the schools—heat for pool, space heating, space cooling, and domestic hot water. Often cogens used in similar applications supply two or sometimes three sources. “This is something I haven’t done before in similar configurations,” says Shinneman. “To add the cooling, that’s not common.”

The cooling was added to get a greater utilization of the available thermal energy—to get more bang for the buck, so to speak. “The big problem in cogeneration is finding a home for the thermal energy. The PG&E requirement for getting less expensive gas is 42.5 % of overall efficiency. If we do that we save about 20 cents a therm for gas, which is not insignificant. So we can get the benefits of the less expensive gas this way,” says Shinneman.

Many times thermal energy can’t be utilized this well. “One reason is the owners’ threshold for return on investment. How many years of energy savings is it going to take to pay back the capital? A lot of owners have mandates by their boards, or whoever, that they don’t want to have any longer than a few years. And the district, being an institution, will own its facility forever. So because the school was willing and able to have a longer payback time, that allowed us to spend a little more money to take advantage of things we might not have been able to otherwise.”

Installing the Goods
All in all, the installation pretty much went as expected. The fact that the engineers did a lot of planning beforehand probably had a lot to do with it—and the fact that the owner was good to work with. “A lot of the piping was prefabricated, so there was very little field welding and assembly time at the job sites,” says Greg Genelin, a service manager at Strategic Mechanical who worked alongside Petty during the installation.

“Once the buildings were built and the equipment arrived, the time it took to pipe these buildings was two to three weeks,” says Petty. “This is very quick. We were working on two of them at the same time, so we had crews that were set up to go from one school to the next. One crew was setting up equipment and the other crew was installing piping. For this project there was a lot of underground piping needed to hook into the school’s infrastructure. On one of the sites we utilized approximately .25-mile of pre-insulated pipe to get over to the pool heating system. We had a crew set up as the underground piping crew, and they would take care of all that.”

Petty estimated that the installation took about six months of actual working on the job. “We had a certain time frame and we went way over it. For one thing, it took a while to get some of the equipment. Then at the end of installation, it was realized that there was a special breaker—required in all PG&E installations—that needed to be installed on a cogen facility. The engineers were not informed of this until the project was finished, so they had to go find the switch gear and panel, and the district had to buy the necessary equipment to install it.

Shinneman attributes a lot of the installation success to thorough engineering on the part of all involved, and the fact that there was fairly good documentation to begin with. “Probably what helps us is that we’ve done a fair amount of these over the years, dating back to the mid ’80s,” says Shinneman. “Knowing that there’s all these potential gotchas, we really coordinated with all the vendors and had them review the documents. We’ve had good vendors, as well.”

The Utility Factor
The Tecos have only been running for several months now. “We had the construction done almost a year ago, by April of 2004, and since that time we had been trying to get PG&E to sign off on this,” says Petty.

“PG&E has certain guidelines not spelled out in the prints,” says Genelin, “so my advice to anyone who is installing one of these systems is to find out from the power company if you need to reduce your gas load or electric load at a certain time during the day. You’ll also want to find out what kinds of rebates they have and follow out their systems, as well as determine the exact interface utility equipment required.

Considering the fact that the PG&E account with the Fresno Unified School District has been considerably shaved down by the use of the cogens, the aforementioned oversight on the part of PG&E may seem a little suspicious. However, even with the loss of revenue, PG&E has been nothing but gracious to the district in general. So it appears that the reason for the lack of communication was simply due to the fact that the utility is still figuring out how to best manage the installation of cogen technology. “PG&E is still learning how to deal with all the bureaucracy and details that come with installing these,” adds Petty.

Ironically, to get a rebate, a business purchasing cogens needs to go through their local utility. “PG&E has been as helpful as they can possible be,” says Peters, “Obviously they would rather see people buying their energy from them, but they have never laid out any restrictions about it or been impolite. We are their biggest account in the area, so they know they haven’t lost a customer just because we’re using less electricity in the summer time.”

Looking Back
One of the biggest challenges Strategic Mechanical came across during installation was the small mechanical room sizes. “We had to maintain 40 small spaces,” says Genelin. “Maintaining electrical and access clearance for the motors themselves was almost impossible.” But they pulled through nonetheless.

They also found that the quick reaction time of the controls was difficult to coordinate with the staging on and off of the Tecogens. “If we were to design one of these systems, we would have put in a storage tank so the system didn’t react so fast,” starts Petty. “Right now you have reaction times of seconds, and control valves don’t react that fast. This means you can exceed the maximum temperature that your reclaim equipment will allow. So if you have something that would provide you with a little more operating time in between sequence changes, like a storage tank, it would be easier to control.”

They also would have loved to have seen another heat exchanger added to pick up the waste heat. “These plants are feeding so many different kinds of mouths—with cooling, heating, domestic hot water, and heating for the pools and electricity—and all these things vary as to when they are on and off, or whether they are happening at the same time. All these different scenarios create the need for a pretty high level of control coordination. And that was definitely higher in this project than I’ve seen in the past,” says Petty.

Better Than Expected
Although the power systems have only been online for a few months, they’ve been running splendidly and non-stop the entire time. They’ve passed all tests, such as air-quality tests and those run by the utility to fulfill electrical safety requirements. In other words, so far so good. “Our original expectations were that they would heat the pools to 80 degrees [F] and that we could keep them on in the winter time and summer time at whatever temperature was desired,” says Peters. “Then, if there was any heat left over in the summer, we could cool the buildings. In reality, we not only heated the pools from cold—from below 50 degrees [F] to temperatures of 80 degrees [F] in less than a week—but the excess energy that would normally just go out the stack is instead used to heat the water in the HVAC loop and heating of the classrooms. So it’s sort of an unintended consequence. And the systems have far exceeded our expectations.”

Shinneman notes that the quality of the workmanship was particularly outstanding on this project. “The mechanical contractor did an extremely good job. It’s a real showpiece. And the tradespeople who worked on the project, they all really knew what they were doing. They were all professionals and the project reflects that.”

AMY SORKIN is an LA-based freelance journalist and copywriter who specializes in marketing communications. Her articles and profiles have appeared in over 30 publications including Marie Claire, Woman's Day, and The LA Weekly.

DE - July/August 2005