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Add Variable-speed Compression to the Refrigeration Technology Toolbox

Joe Summers | Senior Product Manager – Scrolls & Drives
Emerson’s Commercial & Residential Solutions Business

Among the available options to improve refrigeration efficiency and performance, variable-speed compression technology has historically been an underutilized asset in the system design toolbox. Instead of exploring its many benefits, many supermarket and restaurant retailers continue to hold on to persistent misperceptions about high costs and implementation complexities. Today, shifting market dynamics, technological advances and sustainability concerns are reshaping the conversation. In a recent article for Consulting-Specifying Engineer, I explored the growing business case for variable-speed compression technology across an expanding spectrum of commercial refrigeration applications.

What’s causing the industry to re-examine the potential of variable-speed compression technology? Sustainability initiatives, refrigerant regulations and energy-efficiency mandates are driving food retailers toward more efficient refrigeration equipment. Many are evaluating equipment that will help them to lower their total equivalent warming impact (TEWI) by:

  • Delivering high energy efficiencies and/or achieving ENERGY STAR® certification
  • Leveraging lower-global warming potential (GWP) refrigerants

At the same time, food retailers are responding to market trends by adopting smaller-format stores that favor distributed refrigeration strategies over traditional centralized architectures. As a result, self-contained, reach-in refrigerators and freezers, display cases and walk-in coolers — that don’t need to be connected to a centralized rack system — are becoming more commonplace while offering increased merchandizing flexibility.

Due to a steady decline in the applied costs of power electronics, manufacturers of variable frequency drives (VFDs) have made tremendous strides in improving their application potential and ease of use. All told, the cost/benefit analysis of variable-speed compression technologies has improved significantly, bringing them into parity with traditional refrigeration options while delivering a variety of end-user benefits, including:

  • Improved energy efficiency via better load matching, less cycling on and off, soft start-ups and faster pull-downs
  • Increased precision and accuracy of temperature and humidity control
  • Enhanced equipment reliability via proactive motor failure prevention, improved diagnostics, reduced start/stops and power fluctuation management
  • Accelerated return on investment (ROI) via energy and equipment savings
  • Adaptable to multiple applications
  • Decreased, more controllable noise levels
  • Opportunities to become even more affordable via the availability of state and utility incentives that can greatly reduce upfront costs

How Emerson is supporting OEMs

For original equipment manufacturers (OEMs) of these self-contained systems, variable-speed compression represents one of the few remaining options capable of helping them to improve energy efficiencies or meet market demands for environmentally friendly refrigeration equipment.

Emerson’s variable-speed compression technology consists of a variable-speed compressor — typically a low-profile horizontal or vertical scroll — paired with a VFD. Rather than using a traditional induction motor, compressors are equipped with brushless permanent magnet (BPM) motors to deliver:

  • Improved efficiency, even at low speeds
  • Increased power density to allow for smaller compressors
  • 15 to 30% overall efficiency improvements while reducing size and cost

Pairing a low-profile scroll compressor with a VFD enables it to modulate across a much broader capacity range. Rather than cycling on and off, compressors can precisely match capacity in response to changing refrigeration loads. This paired VFD and compressor approach delivers twice the speed and capacity in a much smaller scroll compressor (e.g., 7,000 revolutions per minute [RPM] versus 3,500 RPM) while delivering:

  • Improved equipment reliability
  • Continuous and more precise temperature and humidity control
  • Low starting torque to eliminate startup current spikes

Copeland™ variable-speed compressor lineup

Copeland horizontal and vertical scroll compressors are seamlessly integrated with Copeland EVM drives to create best-in-class, variable-speed compression solutions for commercial refrigeration.

Variable-speed horizontal scroll compressors

Horizontal scrolls are well-suited for lower-profile, medium-temperature (MT) applications such as stand-alone display cases and self-contained packaged systems.

  • ½ to 4 HP capacity modulation range
  • Approved for use with R-290 (GWP = 3) and lower-GWP A1 refrigerants (R-448A, R-449A)
  • Height is less than 10 inches, providing maximum design flexibility

Per the recent charge increases approved by the UL 60335-2-89 safety standard, Emerson is currently qualifying our horizontal scroll compressors for R-290 charges up to 500g. We are also working to make them A2L-ready when A2Ls are approved for use in commercial refrigeration.

Variable-speed vertical scroll compressors

Traditional vertical scrolls have an expanded capacity range that can cover a wide spectrum of MT and low-temperature (LT) reach-in and walk-in equipment.

  • ¼ to 7 HP capacity modulation range
  • Approved for use with R-448A and R-449A; currently qualifying A2Ls for future use
  • Vapor-injection option available for LT applications

Variable-speed fractional hermetic compressors

Fractional Copeland hermetic compressors are ideal for smaller, MT and LT reach-in units, display cases and walk-ins. Their small profile helps to maximize available merchandizing space.

  • ⅛ to ⅞ HP capacity modulation range
  • Integrated VFD with smart controller
  • Approved for use with R-290

Today, Emerson continues to expand its variable-speed compression solutions to provide end-users and OEMs with an ideal combination of versatility, high performance, reliability and efficiency. To learn more, please explore our variable-speed compression solutions.

 

 

Copeland™ Scroll Booster Architecture Balances Sustainability, Serviceability and Flexibility

Andre Patenaude | Director – Solutions Integration,

Emerson’s Commercial and Residential Solution’s Business

As refrigerant regulations continue to progress rapidly, commercial refrigeration stakeholders are looking for refrigeration solutions capable of balancing their sustainability, serviceability and equipment lifecycle goals. Emerson recently completed the development of a new distributed system architecture called Copeland scroll booster. It is designed specifically to help food retailers achieve these goals while providing the flexibility to accommodate a wide range of low- (LT) and medium-temperature (MT) applications.

When searching for viable and sustainable commercial refrigeration strategies, stakeholders often find themselves weighing the pros and cons of many different system types. Systems that use alternative refrigerants with a global warming potential (GWP) below 150 typically introduce increased service complexities and lifecycle costs. Other systems may not quite achieve sustainability targets but offer serviceability improvements. And when you consider the ever-expanding diversity of system designs needed to address modern commercial refrigeration requirements, system selection becomes even more complex.

Much of the work taking place at Emerson’s The Helix Innovation Center is focused on solving this industry-wide challenge, and the Copeland scroll booster architecture is a key outcome of these efforts.

Leveraging a new refrigerant alternative

Regulatory mandates are driving significant changes within commercial refrigeration system designs to minimize environmental impacts. Many operators are seeking alternatives to traditional centralized direct expansion (DX) refrigeration systems, which utilize large charges of high-GWP hydrofluorocarbon (HFC) refrigerants and are prone to leaks. This has led to an increasing variety of distributed refrigeration approaches — which offer smaller refrigerant charges, lower-GWP refrigerants and wider application flexibility.

Although natural refrigerants CO2 (R-744) and propane (R-290) have the lowest possible GWP ratings, they also come with high operating pressure (R-744) and flammability (R-290), introducing operational complexities and design limitations that many food retailers may not be prepared to address. Newer refrigerant blends — such as the A1 hydrofluoroolefin (HFO) refrigerant R-513A — deliver excellent performance characteristics, much lower GWP than HFCs and zero flammability. Offering the lowest possible GWP (573) among non-flammable refrigerants, R-513A has low-pressure characteristics that provide a familiar operating envelope and require no special training, certification or safety mitigation measures.

Mechanics of Copeland scroll booster

The Copeland scroll booster system is designed to use R-513A for both LT and MT refrigeration loads. Its distributed architecture offers an efficient and environmentally friendly alternative to large centralized systems. System configurations can scale from small, low-charge condensing units to larger distributed racks charged with several hundred pounds of refrigerant.

This innovative technology overcomes the typical challenges of operating a low-temperature system, including requiring compressor cooling via liquid injection and lowering compressor lifespan due to high compression ratios and discharge temperatures. This straightforward architecture leverages the advantages of R-513A’s low-pressure, high-efficiency and key system components to significantly lower discharge temperatures and compression ratios.

This flexible architecture is comprised of one or more MT scroll compressors coupled with one or more LT scroll compressors, where MT compressors can either be placed in a condensing unit or within a typical rack configuration. Condensers may be located remotely or integrated into the system and placed indoors or outdoors. To help reduce refrigerant charge, piping and associated costs, the LT scroll compressors can be placed near the LT evaporators, i.e., directly on top of or beside the case or remotely near the load.

The “booster” design strategy provides significant performance improvements by discharging (or boosting) the LT compressor directly into the nearest MT compressor’s suction line. The lower discharge temperatures of the LT scroll compressor minimize the suction gas temperature of the MT unit and allow the MT compressors to operate within their design limits without the need for additional cooling. The net result is an overall system efficiency gain while greatly minimizing the mechanical loads on the LT compressors.

Simplifying operational complexities

The innovative use of a low-pressure, low-GWP refrigerant within a simple, distributed architecture that’s based on familiar operating principles fills an urgent need within the larger food retail market. The Copeland scroll booster system helps operators to meet their sustainability goals without introducing unnecessary serviceability complexities. Offering the design flexibility to service store formats of varying sizes, its benefits check many key boxes on the list of modern supermarket refrigeration priorities:

  • Lower-GWP, A1 refrigerant (i.e., R-513A)
  • Reduced refrigerant charge
  • Lower leak rates due to lower-pressure system
  • Lower utility costs
  • System familiarity with technicians and end users
  • Low total cost of ownership (TCO) from lower annual energy consumption and lifecycle climate performance (LCCP)
  • Secure remote facility monitoring capabilities

Proof of concept and future evolution

Emerson has conducted successful trials of this technology in various applications and climates. This year, a distributed scroll booster system was installed at Gem City Market, a new small-format supermarket built in Dayton, Ohio. The project involved collaboration among the surrounding Dayton community, city officials and commercial refrigeration industry leaders — including Hussmann and Chemours — who donated their respective expertise and resources to the project. In the future, when even lower-GWP refrigerants (such as A2Ls) are approved for use by applicable codes and standards, a distributed scroll booster system can be adapted for use with these ultra-low refrigerant alternatives (less than 150 GWP).

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