It all began when a Florida university decided it was going to become the greenest of all green campuses [In the U.S. or worldwide]. It wasn’t Florida State or the University of Florida. It was the much less heard of Nova Southeastern University near Ft. Lauderdale. But Nova isn’t exactly a pipsqueek when it comes to size or accomplishments. Its 300-acre main campus is home to 28,000 undergrad and graduate students. It is widely respected for the quality of its academics. It is home to the training facilities for the Miami Dolphins. It boasts the largest library in Florida and the largest aquatics pool on the East Coast. And it also figures to be the home of what will be, when finished, the fourth largest ice-conversion chiller facility in the country, which is where Nova Southeastern’s “green” story begins.
Ice Conversion Chillers
Nova Southeastern University is currently building what will be the fourth largest ice-conversion chiller facility in the United States. The facility aims to provide efficient cooling with the absolute minimum power required.
“We wanted to create an air-conditioning facility that would deliver the kind of cooling we need in Florida, while using the absolute minimal power possible,” says Jim Marinelli, HVAC manager for Nova Southeastern. “We already had three, what we call main central plants on campus, but they were older and we wanted to replace them with a greener plant that could expand to meet the future needs of the school.”
Ice conversion saves power because it makes ice at night when power costs less, then melts it during the day to chill water that is distributed through an underground piping network to many of the buildings on campus. In addition to the energy dollars saved, Florida Power and Light also offers significant incentives for this type of air conditioning. Nova’s current plant features two 2,300-ton chillers and custom-built insulated steel-lined concrete tanks that hold 390,000 gallons of cooled water. The plant is designed to expand to three more chillers as the campus grows.
Looking for Better Monitoring
“When we were getting close to bringing the first two chillers online, we started looking for a way to have better monitoring capability over every aspect of the chillers so we can keep them running at peak efficiency in real time,” says Marinelli. “We went to our mechanical contractor, Hill York, and asked what they could do to improve our metering capabilities.”
He went to the right source. Not only is Hill York (www.hillyork.com) the largest mechanical contractor in Southern Florida, it is also the only America Green Star Certified contractor in the state to be recognized by the United States Green Building Council.
The building oversight management system being employed to monitor the chillers features a clamp-on ultrasonic flowmeter, which accurately monitors how many gallons per minute are going through the chiller barrel.
“Most people think that a Building Automation System (BAS) gives you all the monitoring capability you need,” says Larry Clark, LEED AP, director of corporate business development at Hill York. “But that just isn’t so.” While BAS has internal functions capable of generating large reports, but they are limited in their ability to plot and trend multiple data points over a user-designed timeline. The facilities personnel at Nova wanted to track all of the functions of their chillers in real time, particularly water flow.
BOM for System Insight
Hill York recommended what it calls Building Oversight Management (BOM). “We are a licensed dealer for utiliVisor, which we believe to be the most effective BOM in the industry,” says Clark. “They provide an online, real-time tool that provides oversight, analysis, and reporting for a building’s mechanical plant and utility management. It works with the building’s BAS through non-interfering interfaces that enhance without disrupting the operation of the equipment, controls, or BAS. It collects and formats data for delivery over the Internet, monitors for operations and equipment error states, provides real-time oversight access via the Internet, and monitors overall system performance.”
The system allows Nova to see everything happening throughout the chiller system from a computer interface. It works with the BAS and other resources and can monitor all of the facilities controllers.
“I can click on any building, go to any air handler, and raise the supply temperature, shut the machine down, check on humidity, carbon dioxide, supply air temperature, and so on,” says Marinelli. “But one of the big advantages is that both Hill York and utiliVisor also constantly monitor the system from their own facilities, and if anything isn’t performing as it should, they immediately notify me and give recommendations to correct the problem.”
“We like to call our system a real-time Web-based observation resource,” said Tim Angerame, sales engineer at utiliVisor. “We take information from the system itself, push the information out to the Web, and are able to view the plant data from any Internet connection because utiliVisor is an ASP model.” The system looks at the information in conjunction with the utility rates and calculates performance on a real-time basis.
Flow Control – The Critical Measurement
Flowmeters are integrated with the building oversight management system, which allows operators to monitor all aspects of the chiller systems via the facilities controllers.
Of all the parameters monitored by the new system, Marinelli is most concerned with water flow. “In the past we have had test and balancing done at our other plants,” says Marinelli. “But I’ve never been happy with it because it can’t be accurate without actually measuring the flow of the chilled water.” In the past they’ve measured the flow by differential pressure, which Marinelli doesn’t trust as an accurate reading. “I want to know how many gallons per minute are going through the chiller barrel; I want to know how many gallons per minute are going through the condenser barrel,” he says. “Fortunately, the utiliVisor system includes ultrasonic flowmeters that we retrofitted directly onto the piping of the new
The meters Marinelli refers to are Flexim’s BTU nonintrusive ultrasonic flowmeters with all flow transducers and temperature sensors connected to one unit to eliminate errors.
“We always specify Flexim flowmeters because their accuracy is within 1 percent of rate backed up with ‘wet flow’ calibration certification,” says Angerame. “More important, they maintain that accuracy even at low flowrates.” While chiller applications do not require very low flowrate capability, Angerame says the Flexim meter captures low velocities better than any other meters he has encountered. “If the flowrates aren‘t detected, you’re giving away free energy,” he says.
“It’s like I finally have control over my chiller system,” says Marinelli. Not only are Hill York and utiliVisor constantly monitoring its operation, Marinelli can use the flowmeter data to fine tune the system. He can accurately place settings where the factory recommends for optimum system performance.
But there’s more to it than that, says Marinelli. Since his pumps are outfitted with variable-frequency drives, he can stop running them at full speed. Before the Flexim meters, he used butterfly valves and gate valves to back down flow. Now he’s able turn every valve wide open and program the frequency drive to run at the optimum speed to deliver the cooling water.
For instance, if he has a 1,000-ton chiller that calls for 2,000 gallons in the evaporator barrel, he can use the variable-frequency drive to ramp up the pump until the flowmeter tells him he’s getting the 2,000 gallons he needs to lock the drive on that setting. So, while he may have 60 hertz available, he may need only 50 hertz to get the flow he needs and save power. “I don’t need to run my pump at full speed,” says Marinelli. “The frequency drive brings the pump up gradually instead of starting all at once. Not only does that cut down the amperage, it also saves considerable wear and tear on the pump and motor.”
The addition of its BOM and the ultrasonic flowmeters are helping to enable Nova Southeastern to achieve its stated goal of becoming the greenest college campus.
Jack Sine is a freelance writer specializing in green building and indoor air quality issues. He can be reached at firstname.lastname@example.org or at 845-831-6578.