Emphasizing Part-load Performance

According to Joe Sanchez, application engineering manager, Bitzer US Inc., “One trend that addresses system efficiency is the shift to focus more on year-round system performance rather than its performance at peak demand.”

Sanchez elaborated: “This enables system manufacturers to design their products to be more efficient at the conditions where they will run most often, which is generally part load.”

Eric Walthall, regional marketing manager — North America, Danfoss, provided more background on this trend, explaining the parameters now being emphasized for efficiency are Integrated Part Load Value (IPLV) for chillers and Integrated Energy Efficiency Ratio (IEER) for rooftop units.

“Regulations have impacted compressors for the last couple of years as manufacturers have been preparing for the new ASHRAE 90.1 standard for chillers in 2015 and rooftops in 2016,” Walthall said.

The emphasis on part-load efficiency “will increase drastically for rooftops in four to five years as DOE is looking to raise the IEER minimum 30 percent over the current 90.1 level and [roughly] 15 percent over the 2016 level,” he added.

Yet, Walthall noted, “While the trend is squarely toward part-load efficiency, there is still a need in the market for full-load efficiency.

“This demand stems from legacy standards and the need to reduce peak demand on power plants,” he explained. “We are enhancing our fixed-speed scroll compressor portfolio with a technology called Intermediate Discharge Valve [IDV] that improves the compressor performance at part-load conditions while maintaining the compressor’s full-load performance.”

Ken Monnier, vice president, air conditioning engineering, Emerson Climate Technologies Inc., also commented on how compressor manufacturers are working to satisfy both efficiency parameters.

“Our industry continues to develop system technologies that simultaneously meet the needs of high-ambient efficiency ratings and those that are more moderate, or tend to be designed to meet a weighted average across high- and moderate-ambient load conditions,” Monnier said. “In response, several different compressor capacity modulation technologies have been developed in both residential and commercial applications, such as two-step, continuous-digital, variable-speed, and multiple-manifolded compressors. While fixed-capacity systems will continue to play an important role within the U.S. air conditioning space, our industry’s ability to apply the right modulation technologies to certain higher-efficiency application needs will garner much focus.”

And, as the emphasis continues to shift toward part load over peak load, innovations in variable speed will come to the forefront, according to many involved in compressor manufacturing.

Joe Orosz, executive vice president and COO of Torad Engineering LLC, referred to the part-load trend as “the movement from a peak-efficiency metric at a fixed speed and fixed condition to a system that looks at the compressor performance over a widely varying set of operating conditions and load points.”

Orosz noted: “This is putting increased pressure on the need to integrate some type of variable frequency drive [VFD] strategy into the unit design in order to reach the performance required.”

Summing it up, Sanchez said: “Applying VFDs to compressors is one of the best ways to increase the part-load efficiency of a system.”

He noted many of Bitzer’s compressors offer unloading features. “Nearly all of our reciprocating, screw, and scroll compressors can be used with a VFD to further optimize the system performance.”

Trending to Natural Refrigerants

Not only are compressor manufacturers closely following trends in efficiency standards, they are also keeping a tight watch on global refrigerant regulations.

“We are actively watching the area of refrigerants driven by various governmental concerns related to greenhouse gas emissions and global warming potential [GWP],” Monnier said. “This activity in the HVACR industry is following a faster-paced timeline in some areas such as refrigeration — especially in Europe.”

Specifically, Walthall noted: “The recent European F-gas regulation to phase out high-GWP refrigerants [e.g., R404A, R134a, and R410A] has global implications, and, as a global commercial compressor manufacturer, we are working to support global markets and prepare for a global HFC [hydrofluorocarbon] phasedown.”

Both Monnier and Walthall pointed out the current HFC phasedown is following the same pattern as the R-22 phaseout.

“We are evaluating a few new refrigerants as part of AHRI’s [Air-Conditioning, Heating, and Refrigeration Institute’s] AREP [Alternative Refrigerants Evaluation Program], and this is being done in close cooperation with the chemical refrigerant providers as well as our OEM customers,” Monnier said. “We followed the same process when we developed compressor solutions for the currently used R-410A, which was developed well in advance of the 2010 phaseout of R-22 to protect the ozone layer. That development actually began more than 10 years prior to the deadline, so it’s appropriate for us to look seriously at these options now, even though there is no comprehensive U.S. legislation currently in place.”

Similarly, Walthall said, “To prepare for this refrigerant change, we’re currently exploring various low-GWP replacement refrigerants.”

He also noted that, in the next few years, Danfoss expects European manufacturers to start developing air conditioning equipment with low-GWP refrigerants, to be followed a few years later in the U.S.

Overall, Schmidt said: “The new regulations to gradually prohibit and restrict use of HFCs, especially in more developed countries, signal a concern about the environment from the industry and end users. Developing countries are also looking for this and making agreements and proposals to substitute them for more efficient, economic, and sustainable alternatives.”

As a result, he pointed out the trend toward natural refrigerants is growing. “These refrigerants are a sustainable alternative for HFCs,” he said. “They’re more energy efficient, have low GWP, and don’t harm the ozone layer. For this reason, since 2011, the EPA has authorized the use of these substances, such as propane [R-290] and isobutene [R-600], for use in household and commercial equipment such as bottle coolers, chest freezers, display cases, and other special equipment, such as low-cooling medical systems. The allowance of HCs [hydrocarbons] as refrigerants will lead to lower operating costs, higher energy efficiencies, and the reduction of greenhouse gas emissions.”

In response to these trends, Schmidt said: “While these regulations directly impact our OEM customers, compressor manufacturers need to be prepared with products that can operate safely and reliably with these gases, all the while consuming the least power possible.”

Publication date: 3/30/2015

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