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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.

Factors Which Drive Innovations Toward the Next Generation of Refrigeration System Design

Katrina Krites | Marketing and Business Development

Manager, Food Retail

Emerson’s Commercial and Residential Solutions Business

The coronavirus pandemic has increased the retail food industry’s collective focus on food quality, safety and sanitation in supermarkets while driving consumer adoption of click-and-collect. At the same time, industry regulations impact retailer behaviors. These factors have brought more attention upon refrigeration systems. In a recent Progressive Grocer article (pages 76–80), I explored how refrigeration products, monitoring and sensing devices can support these initiatives.

Impacting food quality and safety

A grocer’s approach to refrigeration is a fundamental part of creating ideal shopping experiences for consumers. Starting with the configuration of the display cases, merchandising strategies are designed to present food in the most appealing ways. Many cases are now equipped with enhanced controls that turn on lights when a shopper approaches. By leveraging case controls and the internet of things (IoT) technologies, retailers can more effectively keep perishable foods within ideal temperature ranges, thus positively impacting food quality and safety while maximizing shelf life.

Continued improvements in data analytics and cloud-based, IoT technologies are enabling connectivity among equipment and devices, which will allow retailers to achieve much greater holistic controls of not only their refrigeration assets, but also other key facility systems, such as HVAC and lighting. These are areas in which Emerson has invested significant resources and will continue to do so in the future.

Closely related to that are the abilities to monitor and track the temperatures and locations of perishable foods throughout various steps along the cold chain journey.

Acceleration of click-and-collect

If what we’ve seen in 2020 is any indication, the supermarket industry can expect the continued adoption of online fulfillment options. This change in consumer shopping preferences will continue to drive innovations in the next generation of refrigeration system design.

With the growing popularity of click-and-collect, retailers are adding capacity specifically for these cold-storage purposes. With variable-capacity modulation capabilities that can adapt to changing load variations, the Copeland™ digital X-Line series provides refrigeration flexibility and reliability in click-and-collect applications. In addition, its onboard controls can be networked into a supermarket’s building management system (BMS) for complete refrigeration control and monitoring.

Our facility management controls (E2) and enterprise software (Connect+) also help retailers to remotely monitor their refrigeration assets, optimize system performance, and provide data-driven, proactive alerts of potential equipment issues.

The role of regulations

The regulation of refrigerants continues to be a source of great uncertainty for our industry. For several years, regulations have targeted the phase-down of hydrofluorocarbon (HFC) refrigerants to reduce carbon emissions and their potential contribution to climate change. Many retailers face global, national and state regulatory mandates that ban the use of refrigerants with high global warming potential (GWP) and call for the deployment of energy-efficient refrigeration equipment. As a result, the industry is undergoing a shift toward alternative refrigerants with lower GWP levels and no ozone depletion potential (ODP).

All of this has helped to bring low-GWP refrigeration solutions into the spotlight, and Emerson supports a wide range of options for retailers along the sustainability continuum.

Whether it’s natural refrigerants like CO2 or propane, or lower-GWP synthetic A1 or A2L blends, Emerson equipment is designed to cover the full spectrum of refrigerant preferences in various types of architectures. It’s important to remember that there is no one-size-fits-all solution for this refrigerant transition; food retailers are employing a wide range of strategies, depending on their unique regulatory and sustainability mandates.

Many operators simply may not immediately require a drastic reduction in refrigerant GWP and instead are seeking a more gradual transition toward their future sustainability goals. We are helping these retailers to develop equipment strategies that will allow them to transition to lower-GWP refrigerants today, while giving them a pathway for achieving reduced GWP levels in the future.

Energy regulations are also in play, and Emerson is committed to helping the industry meet Department of Energy (DOE) efficiency targets for commercial refrigeration equipment. For example, our recent launch of the Copeland digital X-Line series is designed to meet the DOE’s annual walk-in energy factor (AWEF) efficiency standards for walk-in coolers. These products can also help operators in the state of California to comply with the California Air Resources Board (CARB) requirements for small-format grocery and convenience stores. The X-Line series utilizes low-GWP R-448A and is designed to service a limited number of medium- or low-temperature refrigeration fixtures — making it ideal for small, urban store formats or large supermarkets seeking to add refrigeration loads outside of their existing direct expansion (DX) systems.

Innovation throughout the cold chain

Leveraging the power of IoT, operational data and the software that can extract insights and value from this information will also play much larger roles in future supermarket refrigeration strategies. To that end, continued efforts to achieve connectivity throughout the various links of the cold chain will allow supermarkets to gain much greater control of food quality and safety well before it reaches the shelves of grocery stores.

 

 

Grow Your Bottom Line With Sustainable Refrigeration Retrofits

Katrina Krites | Marketing and Business Development

Manager, Food Retail

Emerson’s Commercial and Residential Solutions Business

Across the food retail market, supermarket operators are re-evaluating their legacy refrigeration architectures. A dynamic mix of regulatory mandates, sustainability goals and the emergence of e-commerce fulfillment models are dictating changes in the status quo of refrigeration. We recently published an article in the RSES Journal that discussed refrigeration retrofit strategies that allow retailers to meet their sustainability objectives while improving their bottom lines.

When considering refrigeration retrofits, food retailers must remember that sustainability is a two-sided coin. While reducing leaks of global warming potential (GWP) refrigerants is important for lowering direct emissions of greenhouse gases (GHGs), many supermarket operators often overlook the potential for indirect GHG emissions caused by poor system energy efficiencies.

The Environmental Protection Agency (EPA) estimates that supermarkets are the most electricity-intensive of all commercial buildings. Commercial refrigeration systems account for 40–60% of supermarket energy consumption and are by far the greatest contributor to indirect GHG emissions. Combined, direct and indirect emissions make up the true measure of sustainability, or a system’s total equivalent warming impact (TEWI).

Reduce direct emissions with lower-GWP refrigerants

The transition from high-GWP refrigerants and those with ozone depletion potential (ODP) is inevitable. Common legacy refrigerant options such as the HFC R-404A will be phased down while hydrochlorofluorocarbons (HCFCs) such as R-22 are being phased out. But this does not necessarily mean operators should immediately transition to an alternative refrigerant or embark on a complete refrigeration rebuild.

Lower-GWP A1 refrigerants, such as the hydrofluoroolefin (HFO) blend R-448A/R-449A, are available that allow end-users to retrofit their existing system, reduce GWP from direct emissions by up to 60%, and still maintain a familiar operational footprint similar to the one they have today.

For those operators currently using R-22, the transition to R-448A/R-449A is relatively straightforward and requires very few substantive architecture changes. The transition from R-404A to R-448A/R-449A is slightly more involved but can still be accomplished without significant architectural changes. R-448A/R-449A produces compressor discharge temperatures that run approximately 10–12% higher than R-404A. This may require additional compressor cooling mitigation such as head cooling fans, demand cooling modules, or a liquid or vapor injected scroll compressor. Consult your compressor OEM’s guidelines for specific retrofit procedures.

Improve system energy efficiencies

Any system retrofit or upgrade comes at a cost, so food retailers must ensure their investment delivers long-term viability and returns to their bottom line. This is where reducing indirect emissions by improving energy efficiencies plays such an important role. The U.S. Department of Energy (DOE) estimates that every dollar saved in electricity is equivalent to increasing sales by $59.

While it makes sense to undertake energy-efficiency measures in conjunction with a refrigerant transition, energy optimization best practices can — and should — be performed periodically on all systems. Before considering any retrofit options, start by performing a system assessment to determine your current performance metrics — which in many cases will deviate significantly from the system’s original commissioned baseline.

The next logical step in the energy optimization process is to enable a variable-capacity modulation strategy by either upgrading to a digitally modulated compressor or adding a variable-frequency drive (VFD) to a fixed-capacity compressor. Variable-capacity modulation provides significant system improvements, not just to energy efficiency but also to overall refrigeration system performance, reliability and lifespan. Benefits include:

  • Precise matching of capacity to changing refrigeration loads
  • Tight control over suction manifold pressures, allowing increased setpoint and energy savings
  • Improved case temperature precision
  • Reduced compressor cycling (on/off)

In digital compressor retrofit scenarios, we’ve demonstrated that replacing an underperforming, fixed-capacity compressor with a variable-capacity compressor can result in an additional 4% energy savings — even before activating digital modulation capabilities. And once digital modulation is activated, operators can expect an additional 12% energy savings.

Whether you’re trying to reduce your direct emissions with lower-GWP refrigerants or seeking to improve energy efficiencies and lower your indirect emissions, Emerson has compression technologies and sustainable refrigeration solutions to help you meet your specific objectives. The Copeland™ digital semi-hermetic and Copeland™ digital scroll compressors provide opportunities to transition to lower-GWP refrigerants and enable variable-capacity modulation to drive energy efficiencies.

Online Order Volumes Drive Grocers to Re-Evaluate Refrigeration Strategies

Katrina Krites | Marketing and Business Development

Manager, Food Retail

Emerson’s Commercial and Residential Solutions Business

As I discussed in a previous blog, the coronavirus pandemic forced many food retailers to shore up their click-and-collect fulfillment capabilities to meet consumer demand for an in-store shopping alternative. While many shoppers tried click-and-collect for the first time during the early phases of the pandemic, industry experts expect this change in buying habits to continue well into the future. In a recent ACHR News article, I explored further how grocers are adapting their refrigeration strategies to support an increased volume of click-and-collect orders.

With the onset of the pandemic and the precipitous rise in online fulfillment, many grocers scrambled to add refrigerated areas to stage their customers’ fresh and perishable orders. Months later, the impacts of the lingering pandemic continue to be felt throughout the cold chain — from food retail to distribution and warehousing strategies. For many grocery supply chain stakeholders, this is an opportunity to deploy innovative technologies that they had only thought about implementing previously.

Explore new distribution warehouse strategies

The grocery industry had been experiencing growth in distribution warehouse infrastructures well before the pandemic; with increased e-commerce fulfillment requirements, we expect this trend to accelerate. As part of their efforts to support click-and-collect fulfillment, many retailers are experimenting with various store formats, including dark stores, micro-fulfillment centers (MFCs) and automated warehouses.

In many cases, existing store layouts are not ideally or efficiently designed to handle large amounts of online orders, and having employees on the sales floor picking to fulfill orders can disrupt the in-store shopper experience. To alleviate these emerging pressures, we may see more MFCs and dark stores dedicated exclusively to the fulfillment of online orders.

Implement food safety and environmental controls

As retailers integrate more of these types of fulfillment facilities to improve efficiencies in their picking and order consolidation processes, ensuring food safety will become increasingly important. There’s no question that the pandemic has created renewed focus on grocers’ efforts to protect the health and safety of employees, customers and of course, food. As part of this focus, grocers are evaluating various tools and technologies to help them monitor and control equipment and systems so that their employees can concentrate on providing positive customer experiences.

This will likely translate into a greater demand for critical control systems that help grocers achieve food safety-related objectives, including:

  • Identifying key refrigeration and facility performance issues
  • Implementing periodic air changes (refreshes)
  • Keeping food safe and sanitary

The abilities to perform remote monitoring, troubleshooting and problem resolution — including predictive failure and maintenance analysis — are becoming essential resources for retailers hoping to schedule service intervals and minimize disruption to in-store shoppers. Grocers can also leverage these tools and technologies to implement a variety of other key store activities, such as: enabling connected, hand-washing stations for increased sanitation; installing remote, wireless sensors for food quality monitoring; or providing enhanced HVAC controls to help maintain indoor air quality.

Consider sustainable refrigerant alternatives

As grocers adapt to the consumer preference for click-and-collect fulfillment, many face the prospect of remodeling their stores to supply this additional refrigeration load. This will give them a prime opportunity to transition toward alternative refrigerants with lower global warming potential (GWP).

Many retailers have considered beginning this transition for quite some time but were uncertain about when to start the process. From a timing perspective, it may make sense to start aligning new store design upgrades with their future refrigerant and sustainability objectives. And in certain areas of the country — where grocery demand may be returning to pre-pandemic levels — many retailers will be well-positioned to invest in new refrigeration equipment or store upgrades.

Proposed EPA SNAP Rule 23 Addresses A2L, HFO Refrigerant Use

RajanRajendran2 Rajan Rajendran | V.P., System Innovation Center and Sustainability

Emerson’s Commercial & Residential Solutions Business

In May, the Environmental Protection Agency (EPA) pre-published Rule 23 of its Significant New Alternatives Program (SNAP), which proposed approving (or listing) multiple substitute refrigerants for commercial refrigeration and air conditioning equipment. Overall, the HVACR industry was pleased to see the EPA actively evaluating the use of lower-global warming potential (GWP) refrigerants, although many stakeholders have sought clarifications on several aspects of the proposal. I recently provided Emerson’s perspective on the proposed SNAP Rule 23 for an article that was published in ACHR The NEWS.

Per normal rulemaking protocols, the EPA accepted public comments on the proposed rule to give equipment manufacturers and industry associations opportunities to submit their thoughts and concerns. Like many industry stakeholders, Emerson expressed our appreciation to the EPA for once again approving new low-GWP refrigerants. As I stated in the article, the HVACR industry relies on federal guidance to provide regulatory consistency across the U.S. — rather than allowing states to assume that role — and SNAP Rule 23 is a continuation of the EPA’s efforts to provide that much-needed guidance.

New A2L listings for AC applications

The SNAP Rule 23 proposal lists several mildly flammable (A2L) refrigerants, including R-454B and R-32, as acceptable, subject to use conditions in new residential and light commercial air conditioners and heat pumps. Other A2Ls listed as acceptable in these applications include: R-452B, R-454A, R-454C and R-457A. The rule also lists R-32 as acceptable, subject to use conditions for new self-contained air conditioners that are typically used for comfort-cooling applications (e.g., rooftop units, water-source heat pumps and ground-source heat pumps) and split systems.

For industry stakeholders, this proposal is an indication that the EPA is likely to move towards approving A2L refrigerants in comfort-cooling applications where applicable safety standards — developed by the Underwriters Laboratory (UL) and the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) — are now in place to govern the safe use of A2Ls in these applications. As the development of A2L safety standards for commercial refrigeration is still ongoing, it is important to remember that the SNAP Rule 23 proposal does not yet include recommendations for the use of A2Ls in commercial refrigeration.

With respect to A2Ls, Emerson and other industry stakeholders questioned why the SNAP Rule 23 proposal did not also recommend these newly approved refrigerants for use in positive displacement chillers. From Emerson’s perspective, we welcome new low-GWP options for residential and light commercial air conditioning applications and would like to see substitutes such as A2L refrigerants used to replace R-410A for positive displacement chillers.

Narrowed use of R-448A and R-449A in commercial refrigeration

In terms of Emerson’s other concerns on the SNAP Rule 23 proposal, we are seeking clarification on the narrowed use limits placed on R-448A, R-449A and R-449B in stand-alone, medium-temperature commercial refrigeration units. Today, these hydrofluoroolefin (HFO) refrigerants are used broadly across many applications and provide the flexibility to meet various design requirements. It is our hope that we could potentially remove unnecessary restrictions and/or simplify the guidelines for using these refrigerants within these applications.

Other prominent stakeholders also objected to the EPA’s proposed use limits of these HFO refrigerants, noting that they impose an unnecessary burden on the industry’s transition away from high-GWP refrigerants. R-448A, R449A and R-449B have already been listed as acceptable without these limitations in many types of applications, including: low-temperature, stand-alone equipment; remote condensing units; supermarket systems; and cold storage warehouses.

Overall, Emerson sees the SNAP Rule 23 proposal as a positive step in the right direction for both the EPA and our industry. Considering the global initiative to phase down higher-GWP, hydrofluorocarbon (HFC) refrigerants, the approval of new lower-GWP alternatives will give manufacturers the confidence to move forward with plans to integrate these approved refrigerants into their product development lifecycles.

 

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