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Explore the Advantages of Lowering Refrigerant Charges

Andre Patenaude | Director – Solutions Integration,

Emerson’s Commercial and Residential Solution’s Business

The need to reduce refrigerant charges in commercial refrigeration systems is often the focus of environmental regulations and sustainability initiatives shared by many supermarket retailers and operators. The reason is simple: lowering refrigerant charges reduces the potential for leaks and their associated environmental impacts. But there are also more pragmatic operational motivations for lowering refrigerant charges — from improving refrigeration system energy efficiency, performance and reliability to avoiding equipment replacement costs. In part two of a recent RSES Journal article series, I examine some of the leading strategies for reducing the refrigerant charges in existing refrigeration systems.

Implement variable fan speed control

Most centralized direct expansion (DX) systems are designed for peak summer heat and use mechanical head pressure control valves to maintain fixed pressure in the condenser equivalent to 105 °F condensing. In cooler seasonal conditions, this approach creates a considerably oversized condenser, where a substantial portion of the condenser volume is being used to store liquid in order to build pressure up to 105 °F minimum condensing.

A potential fix to remedying this situation is to remove the mechanical head pressure control valve and install a variable-frequency drive (VFD) to control the condenser fan’s speed. Instead of operating with a minimum fixed head pressure, this strategy provides variable head pressure throughout the year. This allows the system to operate with less refrigerant by removing the need to have a “winter charge” to flood the condenser in low ambient conditions.

Note: For operators in northern climates with sustained periods of sub-zero temperatures (-20° F to -30° F), utilizing a flooded head pressure approach may be necessary to keep systems running during those periods.

If you discover that a condenser needs to be replaced, an additional charge reduction can be achieved from implementing a split-condenser design. The approach effectively helps to maintain system pressure by cutting the condenser surface area in half as ambient temperatures drop, creating a net reduction in condenser surface area, which further lowers the system charge. In summer months, when the condenser utilizes every inch of its surface area, excess liquid refrigerant can be stored in a large receiver tank designed to hold both the summer and winter charges. Consider also using a low-condensing approach in combination with an efficient liquid subcooling strategy to achieve additional charge reductions while maximizing system performance, energy efficiency and reliability.

Adopt a looped piping strategy

In conventional centralized DX systems, individual liquid refrigerant and return suction lines are fed from the refrigeration rack to each case in a supermarket — which requires a large refrigerant charge to support the full load of all cases. An alternative to this approach would be to adopt a looped piping strategy by running fewer large lines to designated sections of the store, from which smaller lines branch off to individual cases. For example, instead of running 30 long lines to individual cases, four to five line loops would support key store sections — with much smaller lines branched off these loops to feed the individual cases. In doing so, store operators can reduce piping, lower leak rates, and achieve a significant reduction in refrigerant charge.

Disconnect and re-distribute remote refrigeration loads

Another common centralized DX refrigeration challenge is to provide adequate refrigeration for cases that are located farthest from the machine room. Unless the system is operating perfectly, the liquid refrigerant traveling through those long liquid lines can develop flash gas bubbles by the time it reaches these distant cases. This results in a variety of issues, which can ultimately increase the amount of refrigerant needed and impact case temperatures.

One potential solution is to disconnect these remote cases from their suction group and install segments of distributed equipment to handle them individually. This reduces the refrigerant charge in the centralized DX system and allows it to operate more efficiently. The Copeland™ digital outdoor refrigeration unit, X-Line Series is ideal for servicing these remote cases or supporting new refrigeration requirements, such as walk-in coolers for click-and-collect fulfillment. In addition, the Copeland indoor modular solution provides flexible options for spot merchandizing cases, which could also be disconnected from a DX system.

Transition to distributed architectures

The prospect of large-scale leak events is always a possibility in large DX centralized systems, which can often be charged with up to 4,000 pounds of refrigerant. If even half of that charge were to be emitted in a catastrophic leak, operators would face potential environmental penalties and excessive refrigerant replacement costs. But this centralized approach is no longer the only option for large-supermarket refrigeration. In their place is an emerging variety of distributed architectures designed to lower refrigerant charges, deliver improved energy efficiencies, and operate using lower-GWP refrigerants.

Distributed architectures that utilize Copeland scroll compression technology can deliver significant system efficiencies, particularly when using a low-pressure refrigerant like R-513A. For example, Emerson’s distributed scroll booster architecture is designed to overcome common low-temperature system challenges and leverage R-513A’s low pressure and high efficiency to provide:

  • Lower discharge temperatures and compression ratios: 1.9:1 at -10 °F saturated suction temperature (SST) and 20 °F saturated discharge temperature (SDT)
  • Reduced compressor strain and related maintenance issues
  • Increased overall system efficiency and lifespan
  • Reduced stress on pipes and fittings, which lowers the potential for leaks

All the strategies discussed herein will not only help to lower your refrigerant charge but also deliver a variety of system efficiency and reliability benefits.

Strategies for Maximizing Refrigeration System Efficiencies

Andre Patenaude | Director – Solutions Integration,

Emerson’s Commercial and Residential Solution’s Business

For many supermarket operators, reducing energy spend in their refrigeration systems is a key sustainability objective. But as most refrigeration systems drift from their original commissioned states, they inevitably lose efficiencies over time. In a recent RSES Journal article, I explored some of the root causes of this all-too-common problem and presented proven strategies for maximizing refrigeration system efficiencies.

There is often a domino effect that contributes to declining refrigeration efficiencies: setpoints are changed, mechanical subcooling strategies become ineffective, condensing pressures increase, and overall system energy consumption rises. At the same time, maintaining consistent case temperatures can become a constant struggle — often causing the reliability of these systems to suffer.

But this inefficient, unreliable state neither has to be your status quo, nor does it necessarily mean that it is time to replace your existing refrigeration system. In fact, there are a variety of tools and techniques for taking back control of your supermarket refrigeration system.

Shore up your liquid subcooling strategy

Refrigerant (liquid) subcooling results in denser liquid — which packs more BTUs per pound and maximizes system capacity and performance — and is a strategy utilized within many supermarket refrigeration systems. But because this approach is based on design parameters that account for the hottest anticipated day of the year, it can present challenges in other weather conditions. In some regions, this can represent more than 95 percent of the time

As ambient temperatures drop, the condenser operates more efficiently, thus decreasing the subcooling load requirements. The net effect is that the plate heat exchanger — which acts as an evaporator to cool the refrigerant — is oversized for most of the year. And as the system tries to adapt to changing weather conditions, the liquid quality output can become more erratic and cause flash gas in liquid lines, which can starve the evaporator.

To manage this load variability, system designers often use electronic evaporator pressure regulators (EPRs), which must be properly set to maintain ideal liquid-out temperatures. If not, these conditions can combine to create a perpetual state of fluctuation as the system “hunts” for the liquid quality for which it was designed, resulting in a myriad of system issues with the potential to negatively impact energy efficiency and reliability.

Install electronic expansion valves

Replacing a system’s mechanical expansion valves with electronic expansion valves (EEVs) is the key to helping operators overcome these subcooling challenges and restoring system efficiencies. EEVs are typically located at the inlet of the subcooler to control and modulate the refrigerant flow of the heat exchanger much more effectively, regardless of whether it is the hottest or coldest day of the year. As temperatures and liquid quality fluctuate, EEVs allow a system to run at maximum capacity and deliver the performance advantages for which it was originally designed:

  • Higher BTUs per pound of circulating refrigerant
  • Reduced liquid line size and charge reduction
  • Improved efficiency for energy savings

Note: for optimum control of a subcooling heat exchanger equipped with an EEV, consider using a variable-capacity compressor like the Copeland™ scroll digital compressor or adding a variable-frequency drive (VFD) to a Copeland Discus™ compressor to provide a balanced load approach.

Raise system suction pressures

The higher the system suction pressures are, the lower the associated compressor power consumption will be — particularly in lower-temperature refrigeration systems. For every 1 PSI increase in suction pressure, a compressor’s energy efficiency ratio (EER) is improved by approximately 2%.

Electronic evaporator pressure regulators (EPRs) are commonly used in centralized racks to maintain evaporator temperatures within various suction groups and optimize the suction pressure to its highest possible point based on case demand. To save additional energy, technicians may “float the suction pressure” by allowing it to rise slightly when the lowest temperature case is satisfied. This can only be achieved if the EPRs are properly set.

Low-condensing operation

Another way to offset the inefficiencies of a system designed for the hottest day of the year is to implement low-condensing operation (aka “floating the head pressure”). Instead of artificially keeping head pressures near 105 °F with the use of head pressure control valves, EEVs installed at cases allow systems to float head pressures down as the temperatures drop — typically maintaining temperatures at 10–20 °F above the ambient temperature.

On average, systems can achieve 15–20% EER improvements on compressor performance for every 10 °F decrease in head pressure. EEVs are designed to modulate with fluctuations in capacity and liquid quality to digest flash gas and control superheat. Using this technique, supermarket operators can reliably float system pressures to 70 °F or lower and achieve:

  • 15–20% EER improvements on compressor performance
  • Increased compressor capacity for faster pull-down rates
  • Lower pressure, which reduces system stress
  • Higher system reliability, which lowers total cost of ownership (TCO)

Give your system an efficiency boost

Emerson provides the tools, technologies and expertise to help operators implement efficient liquid subcooling and low-condensing pressure strategies. Our EX series EEVs feature a patented ceramic gate port design that can manage a wide range of liquid quality and condensing pressures — and deliver precise refrigerant control via variable-capacity modulation from 10–100%.

The companion EXD-SH1 or SH2 superheat controller regulates evaporator superheat to optimize system performance, regardless of ambient conditions. Its integrated display allows operators to check a variety of system conditions, such as superheat, percentage of valve opening, pressure and temperature values.

Natural Refrigerant Cooling Trends for 2021

Andre Patenaude | Director – Solutions Integration,

Emerson’s Commercial and Residential Solution’s Business

I was recently interviewed by Accelerate America to discuss cooling trends for 2021, particularly with respect to the natural refrigerant and sustainable cooling marketplace. The Emerson to Continue Pushing NatRefs article (pages 20-22) also gave our organization an opportunity to discuss some of the specific plans we’re making to support our ongoing commitment to sustainable refrigeration technologies.

There’s little doubt that the installation of natural refrigerant-based systems will continue to increase this year, especially in California, where retailers will be preparing to meet 2022 California Air Resources Board (CARB) regulations. Elsewhere, we can also expect many retailers to continue with trials of natural refrigerant systems as potential strategies for meeting their sustainability targets. Whether it is a transcritical CO2 booster system or micro-distributed, R-290 integrated display cases, these architectures give retailers viable options for utilizing refrigerants with the lowest available global warming potential (GWP).

New investments and refrigeration solutions

For our part, Emerson will continue to invest heavily in research and development (R&D), which includes completing the construction of a new transcritical CO2 test lab at our main campus in Sidney, Ohio. This will be our second dedicated CO2 R&D facility, complementing our current CO2 test lab located at The Helix Innovation Center in Dayton, Ohio. These labs are designed to accelerate product development, collaborate with OEM partners and end-user customers, and help deliver simplified CO2 solutions for the industry.

We are also continuing the development of compression technologies, controls and valves for CO2 in commercial refrigeration, including a new rack supervisor CO2 and facility management controller for transcritical CO2 booster systems. These solutions are built with native applications that help to manage not only all of the standard system operational requirements, but also address high ambient strategies while providing enhanced integration with our CO2 case controls. We are also investing in the development of industrial CO2 compressors, including a new heat pump CO2 compressor.

In addition, we will continue to expand our R-290 based compression technologies, valving and electronic controls, including:

  • Copeland™ low-profile scroll portfolio of fixed- and variable-speed technologies that covers a capacity range from ¾ to 4 HP
  • Copeland variable-speed hermetic reciprocating compressor line that utilizes R-290 in fractional horsepower ranges from ⅛ to ⅞ HP

These R-290 solutions will deliver game-changing efficiency and performance improvements for commercial refrigeration reach-in OEMs as well as environmental life sciences, medical and pharmaceutical applications.

The critical role of digital controls

When dealing with CO2-based systems — and even to some degree, R-290 — digital controls are essential for providing basic refrigeration system management and optimizing energy efficiencies. These controls also contribute to a data stream that operators can leverage in analytics software to detect trends, automate decision making, and drive system performance.

Through the combination of our controls and compressor platforms, we are helping retailers to integrate their entire heating, refrigeration and air conditioning systems. For example, our E2 facility management controller, new CO2 rack supervisor controller and CO2 compressors — which include parallel compressor applications rated to operate at higher suction pressures — are capable of handling not only refrigeration requirements but also incorporating air conditioning systems.

COVID-19 impacts on retrofits and remodels

As the result of the increased food retail sales volumes, previously planned retrofit and remodel projects — either to improve energy efficiencies or transition to lower-GWP refrigerants — may continue to be temporarily placed on hold. The majority of remodeling efforts taking place during these high-volume periods are to provide mission-critical system improvements.

One such mission-critical area where retailers are investing in new refrigeration technologies is in support of emerging e-commerce fulfillment capabilities. While this may also divert attention away from planned retrofits, we expect to continue helping our end-user customers deploy new refrigeration equipment to augment their current systems to meet click-and-collect fulfillment requirements.

 

 

Refrigeration Strategies for Small-Format Retailers

Andre Patenaude | Director – Solutions Integration,

Emerson’s Cold Chain Business

The trend toward smaller grocery store formats has taken hold across the global food retail industry. These small-footprint outlets — which can be located closer to customers in urban centers and universities — are designed to provide optimal shopping experiences that are tailored to appeal to customers’ regional preferences. While traditional centralized refrigeration systems are too large for these small facilities, new equipment is emerging to suit these smaller spaces and support retailers’ unique operational goals and constraints. As I discussed in a recent article for ACHR The NEWS, many retailers are adopting a more decentralized refrigeration approach to support their small-format operations.

Compared to typical large-format grocery stores — which can cover more than 100,000 square feet and are found in most suburban areas — small-format stores are usually less than 40,000 square feet in size and are popping up in non-traditional locations and under-served communities. In terms of refrigeration, large stores utilize complex refrigeration rack systems, which can contain thousands of pounds of refrigerant. Small-format stores require completely different refrigeration strategies — which often means taking a decentralizing approach for more flexibility and much lower refrigerant charges.

Space constraints drive refrigeration options

Lack of space for mechanical rooms and other facility access restrictions are among the primary considerations for small-format retailers. Some stores are located inside residential buildings, which may prevent the use of remote racks or condensing units to be installed on rooftops. In mixed-use spaces, basic considerations such as door clearances can also dictate equipment selection.
The good news for retailers is that there are many refrigeration alternatives designed to address these challenges. The alternatives are often more flexible and typically combine a distributed refrigeration architecture for primary refrigeration needs, along with stand-alone cases — which integrate the refrigeration system into the case — that can be moved around a store to support seasonal and regional offerings.
Distributed approaches to refrigeration system design typically rely on indoor or outdoor condensing unit (OCU) architectures that allow the refrigeration equipment to be installed in closer proximity to fixed display cases. Another advantage of this approach is the ability to deploy a distributed controls architecture, which allows individual refrigeration assets to be operated and controlled independently. Thus, if a facility controller were to fail, there would be little to no impact on individual assets.
In addition, utilizing distributed controls in tandem with a centralized building or facility management controller results in a hybrid approach that delivers the best of both worlds: independent asset control and centralized visibility to all assets.

Multiple approaches for varying preferences

As is the case with large-format retailers, it’s important to remember that there is no one-size-fits-all approach for selecting a refrigeration architecture for smaller formats. From environmental sustainability to system lifecycle costs and servicing requirements, retailers have a wide range of pain points and business criteria on which to base their individual decisions. Emerson is committed to supporting small-format retailers with a variety of refrigeration solutions that can be utilized in most existing and emerging small-format architectures, including:

– A full complement of compression technologies
– Facility management controls and valves
– Copeland™ Digital Outdoor Refrigeration Unit, X-Line Series
– Copeland™ Indoor Modular Solution

We are actively partnering with OEM and retail customers to help create high-value, small-format refrigeration solutions. By combining refrigeration technology and component portfolios with design and domain expertise, our goal is to provide fully integrated solutions that can address a wide range of end-user criteria.

Emerson to Participate in Online ATMOsphere America 2020

Andre Patenaude | Director – Solutions Integration,

Emerson’s Cold Chain Business

As an industry steward and leader in the development of environmentally friendly refrigeration technologies, Emerson is pleased to announce our participation and Silver sponsorship at the ATMOsphere America 2020 conference, which will take place October 20 through October 22. Due to the COVID-19 health crisis, this year’s event will utilize an online, virtual format to make the business case for natural refrigerants.

Per usual, the annual event will feature a packed agenda of keynote presentations, technology case studies, HVACR market trends and policy updates to provide a complete picture of the latest developments and future trends related to the use of natural refrigerants. In addition, ATMOsphere America 2020 will be expanding its scope to cover opportunities for natural refrigerant technologies in Central and South America. As a result, the agenda will include sessions that discuss both international- and national-level policy developments, highlight notable projects, and bring together stakeholders to talk about their experiences.

Policy and Standards panel discussion

Among the industry experts speaking at the event are Emerson’s Rajan Rajendran, V.P., system innovation center and sustainability; and Jennifer Butsch, regulatory affairs manager. Rajan and Jennifer will be participating in the Policy and Standards panel discussion on Wednesday, October 21 at 11:10 a.m. EDT. This distinguished panel will also include Tony Lundell, senior director of standards and safety with the International Institute of Ammonia Refrigeration (IIAR), Christina Starr, senior policy analyst with the Environmental Investigation Agency (EIA), and Glenn Gallagher, air pollution specialist with the California Air Resources Board (CARB).

This panel discussion will explore the current status of federal hydrofluorocarbon (HFC) regulations in the U.S. and the potential impact of presidential administration changes upon future rulemaking. Rajan and Jennifer will give a short presentation and then take questions from the online audience.

Latin America CO2 transcritical case study and training panel discussion

On the final day of the conference (October 22), Emerson’s Carlos Obella, V.P., engineering services and product development for Latin America, will present a case study in a session titled, Casos de Estudio: Refrigeracion Comercial e Industrial at 3:20 p.m. EDT. The presentation will demonstrate how they have applied an enhanced control algorithm to ensure the optimized system management of CO2 transcritical systems with liquid and vapor ejectors. The case study will highlight an installation located in Sao Paulo, Brazil, which utilized dynamic superheat management and the implementation of overfeed evaporators to considerably increase the overall coefficient of performance (COP) when compared to other direct expansion (DX) solutions. Other system features to be discussed include: heat reclaim regulation, dynamic suction setpoint and remote monitoring via a web-based application. In addition, Emerson’s Alonso Amor, technical manager for Mexico, will present on the learning centers in both Brazil and Mexico in a session titled, Panel de Discusion: Capacitacion at 12:20 p.m. EDT.

 

ATMOsphere America 2020 promises to be extremely informative for those interested in learning more about natural refrigerant technologies and the policies that impact their use. To learn more about the conference and view a detailed session agenda, please visit their website. To attend any of the sessions, please register here.

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