Major energy upgrades and use of Clamp-on technology
for chilled, hot and domestic water proves to be most
reliable and accurate
The University of Akron has a reputation for being environmentally active in their use of energy resources. Not only do they have an Office of Sustainability that acts as a liaison on all capital planning projects; they also have their FirstEnergy Advanced Research Center that develops energy technology to generate efficient electric power with minimal carbon dioxideemissions. They have also fine-tuned their energy systems to get the most value out of them and their newer buildings were built to LEED standards. They only had two things holding them back from being an energy efficiency leader: a large enough staff to make needed upgrades and the lack of money to pay for them --problems all too common with colleges and universities around the country.
Then three things happened that solved all of their problems. First, the Ohio state government passed House Bill 251 which called for a 20 percent reduction in energy consumption and greenhouse gas emissions at public institutions in the state. That would seem daunting since they had already honed their energy systems to be as efficient as possible. And it would have been disastrous without the other two events. Second, the Ohio Air Quality Development Authority (OAQDA) offered them $60 million in financing via bonds to help them achieve the goals set by the state.
David J. Cummins, vice president of Finance and Administration and CFO said, “The University of Akron is extremely pleased to make use of QECB financing as part of the overall financial package to assist us in significantly cutting energy costs and greenhouse gas emissions. This project will improve both the indoor and outdoor environment in numerous buildings across campus, while also benefiting the residents of our county and region.
”That was a real blessing, but it wasn’t over. The third thing that happened was that Johnson Controls made the university an offer it couldn’t refuse --a guaranteed energy performance contract. That contract means the upgrades will be paid for by the savings in energy and utility costs over the term of the 15-year contract. The university will not pay upfront costs and Johnson Controls guarantees the contracted savings. The company has been successful in many similar ventures, performing more than 2,500 performance contracting projects with guaranteed savings of $7.5 billion.
As famed engineer W. Edwards Deming once observed, “You can’t manage what you don’t measure.” Nowhere are those words truer
than when using a building management system such as Metasys®. If accurate data doesn’t go into the system, optimum efficiency cannot be achieved. And at the University of Akron the two biggest users of energy are their hot and chilled water systems.
“The chilled water was pretty straight forward,” said David Musser, mechanical engineer and project manager at Akron. “But it was the hot water system that had always been a challenge. You see, we run water at 400 degrees Fahrenheit and four hundred pound per
square inch pressure. That creates some measuring difficulties. A few years ago we weren’t making our own steam. We were buying
it locally because it cost less and running it through the heat exchanges in dorms and other buildings. But we had no way to know if what the steam company was billing us for was accurate. We wanted our own measurements to verify, so we began looking at flow meters. We didn’t want intrusive metering because it was expensive to install, we’d have to shut down the system to calibrate it, and it wouldn’t be likely to last long in that environment.
We decided to try Ultrasonic Clamp-on meters because they were nonintrusive and the technology made sense for our application. The only problem, and it was a big one, was the gel that held the transducers to the pipe would break down because of the 400 degree temperature and the meter would start giving ridiculous readings.
How ultrasonic meters measure flow:
The technique most ultrasonic flow meters use is called transit-time difference. It exploits the fact that the transmission speed of an ultrasonic signal depends on the flow velocity of the carrier medium, kind of like a swimmer swimming against the current. The signal moves slower against the flow than with it. When taking a measurement, the meter sends ultrasonic pulses through the medium, one in the flow direction and one against it. The transducers alternate as emitters and receivers.
The transit time of the signal going with the flow is shorter than the one going against. The meter measures transit-time difference and determines the average flow velocity of the medium. Since ultrasonic signals propagate in solids, the meter can be mounted directly on the pipe and measure flow non-invasively, eliminating any need to cut the pipe.
A high-temp ultrasonic solution:
“We continued to search for a good metering solution for the difficult high temperature measurement. We asked a local
sales Representative, Brian Papa from Chaltron if he had any ideas. It turned out one of the companies he represents had developed a hightemperature ultrasonic flow meter.”
“What Dave experienced is typical o fultrasonic transducers in a hot environment,”said Papa. “Depending on the meter, the gels used for acoustic coupling between the ultrasonic transducers and the pipe have a limited temperature tolerance. Also, high temperatures accelerate the aging of the transducer’s piezzo elements and reduce their operating life.
“That’s why my client, FLEXIM Americas, developed their WaveInjector transducer mounting fixture. It permits the transducer to be mounted at a safe distance from the pipe while still maintaining accurate readings. It enables a set of standard transducers to operate accurately at temperatures ranges from -160 up to 440 degrees Centigrade.”
“We bought one and Brian oversaw the installation,” said Musser. “The first thing we found out was that the steam company was under billing us. It turns out the ultrasonic had a much better turndown than the other meter and was much more accurate on low flow. We added 12 more meters to our larger buildings for hot,
chilled and domestic water.
“Now with the performance contract, we are completing most of our buildings with 28 more FLEXIM meters. These are 2 channel meters that will do both the hot and chilled water Thermal Energy measurement in the same meter. The contractor initially wanted to use some other meter, but we showed him the meters we had already installed, pointed out that they have been maintenance free, need no calibration and are excellent on low flow measurements.
And they communicate directly with their building management system. I think the contractor realized that these meters would be an asset and help Johnson Controls fulfill their part of the contract. It’s clear that accurate and reliable metering is critical to any performance based agreement, but also essential for any important monitoring system.
Without accurate metering you can’t obtain the efficiency objective.”To date everything on the performance contract is on or ahead of schedule and the ultrasonic meters will soon be communicating with the Metasys® building management system.