This ultrasonic flow meter is non-intrusive and capable of accurately measuring low flows during off-peak hours in a CHP environment.
This ultrasonic flow meter is non-intrusive and capable of accurately measuring low flows during off-peak hours in a CHP environment.

In recent years, there has been growing interest in combined heat and power (CHP), also called cogeneration. CHP works by using modular turbines connected in parallel to generate electrical power on site, capturing the heat created, and using it to heat the facility in winter, and drive an absorption chiller in warm months.

So, why is a technology that has been around since Edison creating interest from industries as diverse as manufacturing, shopping malls, and health care? Three reasons: efficiency, money, and independence.


CHP systems capture heat when generating electricity, making them markedly more efficient than typical public utilities that do not. A natural gas-fired power plant operates at around 35 percent efficiency. By capturing and using the heat generated by a CHP system’s turbines, CHP users are able to achieve efficiencies in excess of 90 percent.

“There is a growing awareness of energy consumption and energy costs,” said Peter C. Houck, former assistant general manager of Related Urban. “The demand for energy optimization, energy management, and energy measurement is huge.”

Related Urban is a developer and manager of premium properties that owns the retail portion of Time Warner Center in New York City. The Time Warner Center qualified for financial incentives from New York State Energy Research and Development Authority (NYSERDA). They put the money to good use, winning the Building Operators and Managers Association (BOMA) International Building of the Year Award.

“The incentives for going cogen aren’t just in New York,” said Brad Selmon, president of M.A. Selmon Co., an East Coast rep firm specializing in control instrumentation and accessories.

“I believe all states have similar programs. I recently helped a major Massachusetts sporting goods manufacturer convert to CHP by setting them up with ultrasonic flow metering. They got federal and state incentives in the hundreds of thousands of dollars. It worked so well, they are installing a CHP unit at another site and getting similar incentives.

“The metering was key to qualifying because you have to be able to verify to the state how much you are reducing your carbon footprint.”


Of course, incentives are essentially money, but there are other ways to save money (or avoid wasting it) and it all comes down to measurement. For instance, in 2008, Related Urban wanted to upgrade its metering system at the Time Warner Center. The original flow meters had been inside the piping and degraded over time from continuous contact with hot and chilled water. They opted for ultrasonic, but were very cautious. Most of the metering would be submetering for their retail clients’ heating and air conditioning use. Related Urban wanted consistent accuracy so they weren’t underpaying itself or overcharging its clients for heating and air conditioning. The company’s experience with intrusive metering led it to look into clamp-on ultrasonic metering.

“While the company was naturally concerned with peak usage flows of heated and chilled water, it also was very concerned with off-peak measurements,” said Izzy Rivera, product sales engineer for Flexim Americas Corp. “The company had done its homework and knew that measuring peak flows with ultrasonic technology was a fairly established practice. It was the low flow rates during off-peak when the businesses were closed for the day that would make the difference. Intrusive meters would be able to measure low flow rates accurately until they began to degrade, but the lion’s share of ultrasonic meters would fail miserably when flow rates slowed. Fortunately, we had already had some challenging experience with measuring slow flow rates.

“A few years ago, a company named Coastal Monitoring Associates had come to us. They specialize in monitoring ground water contamination to keep clients within EPA [Environmental Protection Agency] standards,” said Rivera. “The meter they used in their patented technology had been discontinued, and they wanted to know if our ultrasonic technology could do the job.”

Peter Chirivas, an engineer at Flexim, called it a really interesting challenge. “No one at Flexim had ever thought about measuring such slow flows. We had developed the capability to measure gases, liquids, slurries, and all of them over a wide range of temperatures. But they had never tried extra slow flows.

“Coastal hydrologist Ron Paulsen and I worked on the challenge after hours. Coastal’s need was clear and we wanted to be of help. To our surprise, one of our existing meters really did well. We made some adaptations to further improve accuracy and got down to the 1-2 percent range. It worked so well, we now incorporate the technology in a variety of our other meters. We were ready when Related came calling. Related initially bought 28 meters to measure points for physical plant management and the company was pleased with the meters’ performance, Related ordered an additional 50 to submeter their retail clients.”

Sizing Systems

“We had tried ultrasonic metering before without success,” said Dale Desmarais, sales and marketing manager for Aegis Energy Services Inc., a manufacturer of modular CHP systems.

“We sell our systems directly to end-user facilities and also through third-party developers. Because of our TVI [True Vertical Integration] we can provide a full turnkey project, ‘CAD [computer-aided design] to completion.’

“We also have the ability to install the system for free and charge for the electric and heat we produce through our shared savings program. We deliver electric savings from 10-15 percent versus the public utility, so it is critical that we accurately size our system. The original ultrasonic meter we tried was attractive because it installed on the outside of the pipe and saved us significant time. But, it was not reliable and was extremely inaccurate on slow flows. One of our core values is, ‘Deliver on what we say we will do,’ and if we were to oversize an installation, we would not be able to utilize the heat and would not give the customer the savings they expect.

“When we heard of Flexim’s low flow capability, we gave it a try. The results were so accurate that we now use one in most every application,” said Desmarais. “The importance of the ultrasonic meter is that it is extremely valuable to us as we do not need to dedicate other resources, such as the time to identify and hire a qualified plumber, schedule and perform the work, and pay the costs associated with installation of an in-pipe meter. Banks and investors, owners, CFOs, facility engineers, and energy service companies all rely on this accuracy to execute results on their projects, and the Flexim Btu meters are what Aegis relies on to help deliver as promised.”

Independence from the Grid

A final advantage for incorporating CHP technology either as the prime means of electrical power, heat, and cooling, or as a backup, is that your business is no longer dependent on the power grid. If you haven’t actually experienced black outs and brown outs, you have read of their devastating effects. And now we have the added threat of terrorists. Nearly every day we hear of how vulnerable the grid is to terror attacks. So, as long as accurate measurements are included, CHP adds up to a win-win for most everyone involved.

Publication date: 7/28/2014

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