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September 2008

R&D Expands Chilling Choices
By: Mike Sherer

When demand for efficiency pushes refrigeration manufacturers to tweak designs and develop new technologies, you—and your company’s bottom line—win.

Energy in all forms has shaped global politics perhaps more than any single issue so far this century. And while our residential use of energy for heating, cooling and lighting runs high, energy use in commercial buildings is growing rapidly and expected to exceed residential use by 2030.

Refrigeration now accounts for about 6.3% of the energy used in all commercial buildings, though restaurants are only a small percentage of total commercial space, according to Karim Amrane, Ph.D., v.p. regulatory and research at the Air-Conditioning, Heating and Refrigeration Institute. Of the energy used for refrigeration, walk-ins account for about 18%, reach-ins coolers for 5.4% and reach-in freezers for roughly 6.5%.

No surprise, then, that more of you have been considering and purchasing energy-efficient equipment in a variety of refrigeration categories. Even with higher initial purchase costs in many cases, energy-efficient equipment pays for itself more quickly practically every time the price of a barrel of oil rises.

Energy efficiency increasingly makes good economic sense, but many gains in efficiency also are the result of legislative mandates. Refrigeration manufacturers now find themselves in the position of facing a triple whammy—more stringent efficiency standards, more restrictions on the types of refrigerants they can use, and food codes in most states that now require operators to hold food at 41°F or below instead of 45°F. Their pain, however, is your gain.

Increasing Efficiency As Standards Change
Much has been made recently of the final phaseout of HCFCs as the Jan. 1, 2010, deadline looms for the ban on R-22 in the manufacture of new equipment. As of that date, R-22 can’t be used in any new refrigeration equipment, but R-22 can still be produced and stocks maintained to service existing equipment until ’20. After that, production of R-22 stops altogether, and all HCFC production and importation will be banned in ’30.

The phaseout is pretty much a nonevent for commercial refrigeration makers since R-22 is used primarily in air-conditioning systems. For many years now, most commercial refrigeration equipment has used more environmentally friendly HFC refrigerants such as R-134a, R-411A and R-401A. Acceptable refrigerants for commercial refrigeration equipment now also include R-507 in addition to R-134a, R-404A, and R-410A, all of which are HFC refrigerants. But the HCFC phaseout does bring up bigger issues for commercial refrigeration.

Manufacturers have largely adapted to early complaints that HFC refrigerants made compressors run louder and hotter. They’ve also had to tweak systems to make up for the fact that HFCs are a little less energy efficient than HCFCs or CFCs.

An even bigger challenge is that refrigeration manufacturers have also used refrigerant gases to blow foamed-in-place insulation like polyurethane. HFCs again are less efficient propellants than HCFCs or CFCs, so the R-value of blown insulation has fallen at the same time equipment makers have been forced to use less efficient refrigerants.

A 4"-thick panel of polyurethane blown with Freon, or R-11, in the ’80s, for example, had an insulating R-value of 34. The same 4" panel made with R-141b and R-22, both HCFCs, have R-values of 32 and 29, respectively. Made with R-134a (an HFC), however, a 4" panel has an R-value of only 28, which means 18% less thermal efficiency.

Of course the problem confronts all equipment makers. The DOE’s minimum efficiency standards for reach-in refrigerators and freezers take effect Jan. 1, 2010. The new standards are stringent enough, according to AHRI’s Amrane, that 50% of the refrigerators and 75 % of the freezers currently available won’t meet the grade.

The reduction in thermal efficiency of insulation means refrigeration manufacturers either have to increase the thickness of refrigerator walls or make up for it in other ways. If refrigeration systems themselves don’t become more efficient, then the effect of banning ozone-depleting, global warming gases such as CFCs and HCFCs will be negated by the increase in global warming gases produced to power less efficient equipment.

A Proactive Approach
Some large companies aren’t waiting around for governments to mandate what’s acceptable and what’s not. McDonald’s Corp., PepsiCo, Coca-Cola, Unilever, Carlsberg and IKEA have formed a co-operative initiative called "Refrigerants, Naturally!" to explore alternatives to HCFCs and HFCs. Learn more by visiting the Web site

Several years ago McDonald’s built an entirely HCFC-free store in Denmark, using CO2 as a refrigerant in beverage machines and the HVAC system and hydrocarbons—or HCs—in some refrigeration equipment. Using HCs as refrigerants may not gain widespread use due to safety issues (they’re highly explosive), and CO2 isn’t as effective in warmer climates for use in HVAC systems. The unit in Denmark, though, has proved more energy-efficient than comparable stores, making the point that alternatives can work. McDonald’s demonstrated similar CO2 and HC prototype equipment at the Beijing Olympics this summer.

"For us, it’s important to demonstrate leadership," says Bernard Morauw, senior director of worldwide operations for McDonald’s. "We can send a message to the industry, but at the end of the day it has to be a sound business decision. If [an alternative] isn’t economically viable or commercially feasible, we won’t pursue it."

To read about some new technologies that are saving money, read on for our sidebars "Technology To The Rescue" on page xx, "Making Better Walk-Ins" on page xx, and "What Else Is New?" on page xx.

Technology To The Rescue
To make up for less efficient refrigerants and decreasing R-values of insulation, manufacturers are taking advantage of every technological advancement that comes along. Two years ago when FER investigated reach-in technology, Ramin Faramarzi, manager of the Refrigeration and Thermal Test Center at Southern California Edison, suggested eight areas in which manufacturers could improve efficiency:

  • Minimizing heat gain with better and/or more insulation, improved door gaskets, etc.
  • Improving fan motor efficiency.
  • Downsizing compressors by balancing the load.
  • Designing better evaporators.
  • Designing better condensers.
  • Lowering the temperature "list".
  • Changing from capillary tube systems to expansion valve design.
  • Making demand defrost commercially viable.
Several changes have been implemented since our ’06 story was published. Many refrigeration makers have incorporated expansion valve design into new models. Manufacturers also have shifted over the past few years from common single-phase shaded pole electric motors to electronically commutated evaporator fan motors (ECMs) and permanent split-capacitor condenser fan motors (PSCs) for evaporators and condensers. PSCs are about 25% more efficient than the old single-phase motors, and ECMs are 50% more efficient.

How is this efficiency possible? ECMs are known to emit less heat than either shaded pole or PSC motors, and less heat inside a walk-in means a reduction in compressor run time. Fewer cycles leads to less energy expended.

California’s Title 20 now requires these energy-efficient motors as part of new walk-in design, and the state’s minimum efficiency standards for other refrigeration equipment pretty much make them essential components of most commercial refrigeration. When those same standards are adopted by the DOE and mandated nationally in ’10, PSCs and/or ECMs will likely be common components in commercial refrigeration equipment.

Demand Defrost, Split Refrigeration And More
Refrigeration makers also have become more adept at sizing compressor, condenser and evaporator so systems are more balanced, making compressors work less and more efficiently. Walk-in makers, in particular, are taking regional and operational variables into account like average ambient temperature and humidity and how often cooler doors are opened and closed. That helps them size components properly for different conditions, rather than spec’ing a standard box for every climate and condition.

Particularly exciting to many is the commercialization of demand defrost. Until recently, most commercial refrigeration equipment was designed to automatically run a defrost cycle on a timed basis whether or not the evaporator needed it. Computer chips and software have made it possible to monitor the actual temperature of the evaporator and run the defrost cycle only when needed.

Some manufacturers claim up to 75% fewer defrost cycles using demand defrost. One maker has taken the concept a step further by developing a "reverse cycle" instead of electric heaters to defrost the evaporator. Electronically controlled by an electric expansion valve instead of check valves or thermostatic expansion valves, this reverse cycle method saves time and up to 80% of the energy required for defrost, says the manufacturer.

Evaporator and condenser designs haven’t changed much, with many makers continuing to use a combination of coiled copper tubing and aluminum fins to facilitate heat transfer. But some manufacturers are experimenting.

One company has focused solely on a new evaporator design that eliminates the aluminum fins that easily trap food and dirt, whose buildup can quickly compromise efficiency. Instead of fins, the company continuously coils copper tubing without kinks or corners and encases it in a plastic sleeve. The sleeve has adjustable vents and fans at both ends, allowing you to direct cold air inside the refrigerator cabinet wherever you want it. The company makes a number of different sizes to fit standard reach-in cabinets as well as custom sizes, and says retrofits are simple.

Another manufacturer has designed its condenser coil in a similar fashion (without fins) to trap less dirt and make it more efficient. Still another has developed an electronically controlled brush mechanism that automatically cleans dust and debris from the condenser coil daily, which maximizes airflow.

Another strategy to improve performance and efficiency, according to Faramarzi, is lowering temperature list. The lower the condensing temperature and the higher the evaporating temperature, the better. At lower condensing temperatures, the refrigerant provides more cooling per pound. It also means lower pressure at the compressor outlet, which makes it easier for the compressor to push the gas refrigerant through the tubing. Higher evaporating temperatures also increase the refrigerant’s ability to remove heat, and increase the suction pressure through the system, again letting the compressor work less.

One way to accomplish this is by using a split refrigeration system instead a self-contained system. Most reach-in models, for example, are self-contained, which means the heat removed from the cabinet is dissipated right into the kitchen, which makes the compressor work even harder to remove more heat. Putting condenser and compressor on the roof or in another cooler space lowers the temp of the condenser. That makes the whole system more efficient.

Finally, in some refrigeration equipment, the compressor itself has become more efficient. Scroll compressors have been around for several years but haven’t gained a lot of traction in foodservice until recently. Rather than the typical piston and cylinder compressor that compress a small batch of refrigerant on each stroke, scroll compressors continuously pressurize refrigerant, meaning more even flow, more even temperature control and greater efficiency.

Scroll compressors tend to offer greater efficiencies the larger they are, so manufacturers generally don’t make them smaller than 1 hp. At that size, though, they’re becoming a more common option among walk-in manufacturers.

Making Better Walk-Ins
Walk-ins, as mentioned earlier, are still undiscovered territory when it comes to efficiency gains. Partly due to the fact that no one has yet come up with a standardized test method, and partly due to the fact that their sheer size makes them more difficult to drop off at a third party lab, no one’s yet come up with benchmark data on walk-ins.

The DOE says it’s working on some minimum efficiency standards for walk-ins but won’t give a timetable for when they might be ready. In the meantime, walk-in makers are taking advantage of the same energy-saving technology available with other commercial refrigeration equipment, including correctly sized systems, microprocessor-based controls, demand defrost cycles, floating head pressure controls, condenser and evaporator fan electronically commutated motors, and good piping design.

A regional walk-in manufacturer in the Northwest, in fact, did some bench tests at the Food Service Technology Center in San Ramon, Calif., to see what effect some of these design elements would have on walk-in performance and was pleasantly surprised by the outcome. The company compared a typical 8’ x 10’ walk-in with 3˝"-thick insulation to one built with 5" insulation, strip curtains, demand defrost, and permanent split-capacitor condenser and evaporator fan motors. The souped-up box was 28% more efficient in FSTC tests, which included simulated door openings.

Even better, while walk-ins aren’t eligible yet for Energy Star listings, the manufacturer convinced local utilities that its energy-efficient units would help qualify LEED-rated buildings. One Northwest utility now offers a rebate on the walk-ins of up to 35%, which reduces operator payback on the more expensive energy-efficient model to one year. Another utility offers a rebate of up to 70% of the cost of a replacement upgrade and 90% if it goes into new construction. The utility says giving operators the rebate is far cheaper than building new generating capacity.

What Else Is New?
Two years ago, the Refrigeration and Thermal Test Center’s Faramarzi suggested that condenser design might be improved not only by increasing the size of the coil, giving the condenser more heat transfer capability, but also by enhancing the tubing itself. A smoother interior surface, he says, instead of a rifled tube, could enhance refrigerant flow, avoid pressure drop and increase heat transfer.

For several years, one small company has been concentrating on unique valves that create a similar effect inside refrigerator tubing. One of the company’s valves creates what it calls "annular" flow of refrigerant through the evaporator tubing, essentially forcing the refrigerant to coat the walls of the tubing instead of flowing like a river. That enhances heat transfer by exposing more refrigerant to more of the tubing.

The valves can be easily retrofit into existing refrigeration equipment, and one commercial refrigeration manufacturer features an exclusive line of models that have the valves already built in. The manufacturer claims the models offer increased cooling capacity, better temperature and humidity control, and faster pull-down. A large QSR operator retrofitting refrigerators in many of its units with the valves has thus far experienced energy savings of about 10%.

Here are a few other innovations refrigeration makers have come up with in the past few years:

Reach-ins and merchandisers. In addition to many of the improvements already mentioned, one maker has come out with a line that features a slide-out refrigeration unit for easy servicing. Instead of copper tubing, the line uses flexible synthetic hose, allowing the unit to slide in and out repeatedly for maintenance and cleaning with out breaking the tubing.

Refrigerated drawers. Manufacturers have recently come out with models that let you control the temperature of each drawer in the unit, so you can freeze, refrigerate, chill or thaw foods in different drawers. They’ve added features like magnetic lid seals, insulated drawer inserts, drawer-fan interlock switches, microprocessor controls and hot gas defrost to help save energy.

Drop-ins and prep tables. Smart new designs use eutectic fluid or glycol gel to cool ingredient pans. The units circulate the refrigerated coolant through sleeves surrounding the pan inserts, so product is cooled from all sides. Every pan is cooled individually without the need for copper piping.

Another maker has put the evaporator coil over the pan inserts instead of below in traditional units, allowing the cold to sink into the food and protecting food from warm convective ambient air.

Undercounter/back-bar cases. A couple of makers offer models of display cases that feature separate temperature control for individual cabinets, letting you hold and display food and beverages at different temperatures. Some models also are stackable.

How’d We Get Here?
Our on-again, off-again focus on energy efficiency in this country dates back to the Arab Oil Embargo of 1973-74. While most of us remember the long lines of motorists waiting to fill up at gas stations, the initial government response was a push for conservation. Pres. Nixon lowered the national speed limit to 55, appointed an energy czar, and temporarily extended daylight savings time. Interest in alternative energy sources spurred some initial research projects into solar and wind power.

A look into efficiency standards was part of the conservation movement, and in ’75 the publication of ASHRAE 90 standards made voluntary efficiency programs possible. In ’76, however, California took what was then a bold step and actually legislated minimum efficiency standards, focusing primarily on residential HVAC and refrigeration. By ’77, the U.S. Department of Energy was created as a cabinet-level federal agency.

The ’79 energy crisis brought back gas lines, gas rationing, a call from Pres. Carter to voluntarily turn down thermostats, and more interest in alternative energy. Though gas became relatively cheap again after the crisis and remained so for another two decades, energy prices started to rise gradually, and the government began to look at energy-efficiency standards more seriously.

Ozone, CFCs And Montreal
About the same time, in the late ’70s, scientists noted an alarming depletion of ozone in Earth’s upper atmosphere and a growing hole in the ozone layer over Antarctica. Research linked ozone depletion to the use of chlorofluorocarbons, first invented in the ’20s and widely used in aerosol sprays and refrigeration systems. In ’87, the Montreal Protocol, an international environmental agreement, set requirements to phase out CFCs in developed countries by ’96. An amendment ratified in ’92 called for a scheduled phaseout of hydrochlorofluorocarbons as well.

In ’92, the first U.S. Energy Policy Act directed the DOE to establish energy-efficiency standards for commercial equipment. Based on ASHRAE’s 90.1, the standards focused primarily on HVAC, commercial water heaters, fluorescent lamps, electric motors and plumbing products. By ’02, though, California started regulating the efficiency of commercial refrigeration equipment, and the DOE adopted the same standards as a federal minimum as a result of the 2005 EPACT.

The current federal standards for reach-in refrigerators and freezers take effect Jan. 1, 2010, and the DOE is supposed to revisit the standards by ’13. In the meantime, California also set minimum standards for walk-in coolers and freezers in ’06. Because there’s no ASTM-approved test method for walk-ins yet, the standards are prescriptive, rather than established minimums.

The regs call for minimum design standards such as automatic door closers, insulation with an R-factor of 28 for coolers and 36 for freezers, electronically commutated evaporator fan motors, and ECM or permanent split-capacitor condenser fan motors. Both California and the DOE are looking to put minimum efficiency standards in place by ’12.

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