4

- i CHAPTER 4

. SCREENING ANALYSIS

TABLE OF CO NTENTS

4.1 INTRODUCTION

................................ ................................ ................................ ........... 4

- 1 4.2 DISCUSSION OF TECHNO LOGY SCREENING

................................ ........................ 4

- 2 4.2.1 Linear Compressors

................................ ................................ ................................ ......... 4

- 3 4.2.2 Increased Evaporator Surface Area

................................ ................................ ................. 4

- 3 4.2.3 Improved Evaporator Heat Exchange

................................ ................................ .............. 4

- 3 4.2.4 Increased Condenser Surface Area

................................ ................................ .................. 4

- 4 4.2.5 Improved Condenser Heat Exchange

................................ ................................ ............... 4

- 4 4.2.6 Forced

- Convection Condensers

................................ ................................ ....................... 4

- 4 4.2.7 Higher

- Efficiency Fan Motors (for Non

- Compressor Refrigerators)

.............................. 4

- 4 4.2.8 Higher

- Efficiency Fan Blades

................................ ................................ .......................... 4

- 5 4.2.9 Improved Resistivity of Insulation

................................ ................................ ................... 4

- 5 4.2.10 Gas

- Filled Panels

................................ ................................ ................................ ............. 4

- 5 4. 2.11 Improved Gaskets, Double Gaskets, and Improved Door Face Frame

............................ 4

- 5 4.2.12 Solid Door (for Cooled Cabinets)

................................ ................................ .................... 4

- 6 4.2.13 Improved Expansion Valve

................................ ................................ .............................. 4

- 6 4.2.14 Fluid Control or Solenoid Valve

................................ ................................ ...................... 4

- 7 4.2.15 Off

- Cycle Defrost, Reduced Energy for Automatic Defrost, Adaptive Defrost, and Hot

- Gas Bypass Defrost

................................ ................................ ................................ .. 4

- 7 4.2. 16 Electronic Temperature Control

................................ ................................ ...................... 4

- 7 4.2.17 Conversion to Alternative Refrigeration System

................................ ............................. 4

- 8 4.2.18 Component Location

................................ ................................ ................................ ........ 4

- 9 4.3 REMAINING DESIGN OPT IONS

................................ ................................ ................. 4

- 9

LIST OF TABLES Table 4.2.1 Thermoelectric COP Data

................................ ................................ ......................... 4

- 8 Table 4.3.1 Retained Design Options

................................ ................................ ........................ 4

- 104-1 CHAPTER 4. SCREENING ANALYSIS

4.1 INTRODUCTION
This chapter discusses the screening analysis conducted by the U.S. Department of Energy (DOE) of the technology options identified in the market and technology assessment for miscellaneous refrigeration products ( C hapter 3 of the preliminary technical sup port document ( preliminary TSD))

. In the market and technology assessment, DOE presented an initial list of technolog y options that can be used to reduce energy consumption of each of the products covered in this rulemaking

. The goal of the screening analy sis is to identify any technology options that will be eliminated from further consideration in the rulemaking analyses.

For each product, the corresponding candidate technology options are assessed based on DOE analysis as well as inputs from stakeholders including manufacturers, trade organizations, and energy efficiency advocates . Technology options which are judged to be viable approaches for improving energy efficiency are retained as inputs to the subsequent e ngineering a nalysis

. Technologies that pas s through the screening analysis are referred to as “design options” in the engineering analysis. Technology options which are not incorporated in commercial products or in working prototypes, or that fail to meet certain criteria as to practi ca bility to m anufacture, install and service, as to impacts on product utility or availability, or as to health or safety will be eliminated from consideration in accordance with Energy Conservation Program for Consumer Products: Procedures for Consideration of New or Revised Energy Conservation Standards for Consumer Products

. 61 FR 3 6974, section s 4(a)(4) and 5(b).

The technologies identified in the market and technology assessment were evaluated pursuant to the criteria set out in The Energy Policy and Conservation A ct, as amended (EPCA or the Act) . ( 42 U.S.C. 6 291

- 6317 ) EPCA provides criteria for prescribing new or amended standards, which will achieve the maximum improvement in energy efficiency the Secretary of Energy determines to be technologically feasible

. (42 U.S.C

. 6 295 ( o )( 2 )(A) ) It also establishes guidelines for determining whether a standard is economically justified

. (42 U.S.C

. 6 295 ( o )( 2 )(B) ) In view of the EPCA requirements for determining whether a standard is technologically feasible and economically ju stified, Appendix A to subpart C of Title 10 Code of Federal Regulations Part 430 (10 CFR Part 430), Procedures, Interpretations and Policies for Consideration of New or Revised Energy Conservation Standards for Consumer Products (the Process Rule), sets f orth procedures to guide DOE in the consideration and promulgation of new or revised product efficiency standards under EPCA

. These procedures elaborate on the statutory criteria provided in 42 U.S.C. 6295 and in part eliminate problematic technologies ear ly in the process of revising an energy efficiency standard

. Under the guidelines, DOE eliminates from consideration technologies that present unacceptable problems with respect to the following four factors:4-2 (1) Technological feasibility

. If it is determ ined that a technology has not been incorporated in commercial products or in working prototypes, then that technology will not be considered further.

(2) Practicability to manufacture, install, and service

. If it is determined that mass production of a te chnology in commercial products and reliable installation and servicing of the technology could not be achieved on the scale necessary to serve the relevant market at the time of the effective date of the standard, then that technology will not be consider ed further.

(3) Impacts on product utility to consumers

. If a technology is determined to have significant adverse impact on the utility of the product to significant subgroups of consumers, or result s in the unavailability of any covered product type with performance characteristics (including reliability), features, size, capacities, and volumes that are substantially the same as products generally available in the United States at the time, it will not be considered further

. (4) Safety of technologies

. If it is determined that a technology will have significant adverse impacts on health or safety, it will not be considered further.

The following section detail s the technology options that were screened out for each product covered by this rulemaking and the reasons why each were eliminated.

4.2 DISCUSSION OF TECHNO LOGY SCREENING

For the products in this rulemaking

, the screening criteria specified in section 4.1 were applied to the technology options to either retain or eliminate each technology from the engineering analysis. DOE also eliminated some technologies that were determined to provide littl e or no potential for energy use reduction for one of the following additional reasons: (a) the technology is already used in baseline products and is incapable of generating additional energy efficiency or reducing energy consumption, (b) the technology d oes not reduce energy use, and (c) there is insufficient data demonstrating benefit of the technology.

For all products, DOE screened out linear compressors, increased evaporator surface area, improved evaporator heat exchange, increased condenser surface area, improved condenser heat exchange

, forced

- convection condensers, higher

- efficiency fan blades, improved resistivity of insulation, gas

- filled panels, improved gaskets, double gaskets, improved door face frames, solid doors, improved expansion valves, fluid control or solenoid valves, off

- cycle defrost, reduced energy for automatic defrost, adaptive defrost, hot

- gas bypass defrost , electronic temperature control, conversion to thermoelectric or absorption refrigeration systems, and component location fo r the reasons that follow

. DOE also screened out conversion to vapor compression and higher

- efficiency fan motors for non

- compressor refrigerators.4-3 4.2.1 Linear Compressors
While promising potential has been reported for linear compressors, DOE does not have suf ficient information about commercial ly available linear compressors to allow accurate predict ion of the performance and cost impacts of this technology.

Moreover, the LG design is proprietary

, as discussed in s ection 3.3.3.1

. Embraco is inviting co

- development partnerships for their Wisemotion linear technology, 1 but DOE does not have information about restrictions and limitations that may be associated with such partnerships. Other compressor manufacturers who have indicated that they have invest igated linear technology have stated that linear compressor technology does not provide a clear path to improved efficiency, and some have indicated that they are no longer actively pursuing this technology. Consequently, DOE concludes that the potential f or widespread use of linear compressors is not certain. For these reasons, DOE has eliminated linear compressors from further consideration in the analyses.

4.2.2 Increased Evaporator Surface Area
Increasing the heat exchanger surface area can be achieved by inc reasing the face area of the evaporator or adding more tube rows. These measures are limited by the geometry of the cooled cabinet. Most compact cooled cabinets use roll

- bond or coldwall evaporators that are located along the back (for roll

- bond designs) o r side (for coldwall designs) walls of the cabinet. Such designs typically take advantage of all available wall space; therefore, there is little to no room for growth in these products. For these reasons, DOE has eliminated this design option from further consideration for cooled cabinets

.

4.2.3 Improved Evaporator Heat Exchange
Improving heat exchanger performance can be achieved through the use of enhanced fins and/or tubes. These types of fin and tube enhancements are common in air

- conditioning applications w here slit and louvered designs are used to enhance the fin surface and different types of internally

- grooved surfaces are used to enhance the tubing. Application of similar enhancements in cooled cabinet evaporators is complicated by the potential for fros t

ac cumulation on the evaporators when the operating at the lower end of their compartment temperature range

. In order to avoid the energy use associated with frequent defrost, fin spacing in the evaporators of refrigeration products is comparatively spars e. During defrost, the typical flat fin design of these evaporators assures that the frost slides rapidly off the fins and doesn’t get stuck on fin enhancement features. The low fin density allows the evaporator to work effectively without blocking airflow with a considerable accumulation of frost. Although little or no frost accumulation may occur in energy testing conducted using a 55  ̊F standardized compartment temperature for cooled cabinets, these products generally also are designed to operate with

co mpartment temperatures down to 40  ̊F or lower , for which evaporator temperature generally4-4 would be below freezing. DOE has eliminated this option from consideration in the subsequent analysis for cooled cabinets

.

4.2.4 Increased Condenser Surface Area
Increasing the heat transfer surface area of condensers can be achieved by (a) increasing the width of the rows of tubes, (b) adding more tube rows along the direction of air flow, or (c) adding more tube rows across the direction of air flow. However, such measures are constrained by the geometry of the cooled cabinet. Most cooled cabinets have their condensers located underneath the cabinet in a small compressor compartment ; however, DOE observed that space for condenser growth wa s very limited in the units that it examined during its reverse

engineering analysis . Therefore, DOE has eliminated this option from consideration in the subsequent analysis for cooled cabinets

.

4.2.5 Improved Condenser Heat Exchange
Use of heat exchanger enhancements for the condenser is complicated by the need for adequate performance when the heat exchanger has not been cleaned. Most cooled cabinets’ condensers (other than hot wall condensers integrated into the outer shells of the products) are made of either steel tubes with steel wire fins or copper tubes with widely

- spaced aluminum fins. These condensers have a very open construction which reduces the impact on performance of dust collect ing on the condenser surfaces. High

- densit y flat fin condensers are known to require more careful attention to cleaning , which occurs infrequently or never in consumer refrigeration products.

4.2.6 Forced

- Convection Condensers

Some smaller, “countertop” cooled cabinets use hotwall condensers. However, m ost undercounter and standard

- size cooled cabinets already use forced

- convection condensers. Therefore, DOE has eliminated this option from consideration in subsequent analyses.

4.2.7 Higher

- Efficiency Fan Motors (for Non

- Compressor Refrigerators)

In its reverse

- engineering analysis, DOE found that non

- compressor refrigerators typically utilize brushless DC fan motors. Therefore, because this technology is already widely implemented in baseline units, DOE elected not to consider it as a design option for non

comp ressor refrigerators. However, DOE retained this design option for cooled cabinets, which typically do not utilize brushless DC fan motors.4-5 4.2.8 Higher

- Efficiency Fan Blades
Cooled cabinet fan blades use an axial design. They are typically injection molded plas tic with a three

- dimensional shape for improved performance as compared with older stamped sheet metal designs. There is in general little data available to quantify the energy benefit possible with further improvement in fan blade design in today’s refrig eration products. Fan performance is highly dependent on details of integration with the system: orifice geometry, tolerance of blade/orifice gap, match of system flow impedance to fan performance, etc. Hence, making credible estimates of energy savings po tential through fan blade replacement requires testing fan blade swaps in baseline products. The cost of fabrication of improved fan blade geometries would be not be significantly higher than that of current designs , so most of the cost increase associated with this technology option would be associated with paying for the blade development , tooling, and/or licensing fees. During discussions with manufacturers, no information was provided which would allow credible calculation of savings and costs associate d with improved fan blades. Hence, DOE has eliminated this option from further consideration.

4.2.9 Improved Resistivity of Insulation
Past research has demonstrated that the resistivity of polyurethane (PU) foam insulation can be improved through the use of add itives that reduce the thermal conductivity of the foam. Discussion with manufacturers has confirmed that there are no available options for improvement in PU foam insulation performance (other than reverting to use of banned blowing agents). Due to the la ck of available information and the predictions that there is no significant benefit to be expected from PU foam improvements, DOE has eliminated this option from consideration in the engineering analysis.

4.2.10 Gas

- Filled Panels
Investigation of the status of g as

- filled panels suggests that there has been some evaluation of this technology by manufacturers of consumer refrigeration equipment, but that no manufacturers are using it in their products. The costs are reported to be as high as for vacuum insulation p anels (VIPs), with less reduction in thermal load. DOE has not been able to identify a credible supplier that would provide gas filled panel products to the refrigeration industry. Consequently, DOE has eliminated this technology from further consideration

.

4.2.11 Improved Gaskets, Double Gaskets, and Improved Door Face Frame
Past investigation on reduction of heat load in the gasket and door face frame area has focused on (1) limiting the conduction of heat through metal casing material passing underneath the gas ket magnet on the cabinet side or in the region of the gasket clip on the door side into the cabinet interior, (2) using a gasket which provides additional cover of frame surfaces towards the interior of the magnet to prevent cold air from reaching the hig h

- conductivity metal casing near the gasket magnet, and (3) providing a long thin “throat” area between the gasket and the interior4-6 to limit convection heat transfer , although this is not generally done with glass doors . Most current designs are effective in addressing these issues.

Limited information is publicly available which would allow quantification of additional improvement potential for the door frame/gasket area of cooled cabinets, hybrid refrigeration products, and ice makers . Some manufacturers use extra

- strong gasket magnets to limit infiltration and thermal loss, but it is unclear whether significant thermal improvement is possible with such systems. Manufacturers during the 2011 Residential Refrigeration Products Rulemaking indicated during t echnical discussions that properly designed and installed gasket systems provide a tight seal and that there isn’t any further reduction in air leakage that could be achieved with improvements in the gasket system such as increasing the magnetic force. 2 In addition, consumer safety laws preclude use of excessive door sealing force.

It is expected that incremental improvement may be possible for some products; however, the lack of good quantified information on general improvement potential in this area mak es these technology option s unsuitable for consideration as design option s

.

4.2.12 Solid Door (for Cooled Cabinets)
Replacing the glass door with a solid door, although it would notably improve energy efficiency, would negatively impact cooled cabinets’ consumer utility by eliminating one of its dual functions, the display of the products stored within. Discussions with manufacturers have indicated that cooled cabinets with solid doors would be much less desirable to consumers. Hence, DOE has eliminated this option from further consideration.

4.2.13 Improved Expansion Valve
Miscellaneous refrigeration products exclusively use capillary tubes for refrigerant flow metering. These tubes are inexpensive and they lend themselves easily to low

- cost fabrication of suction l ine heat exchangers by brazing the capillary to the suction line. Automatic, adjustable thermostatic or electronic expansion valves are available, but they generally are oversized for consumer products such as cooled cabinets and refrigerators . Furthermore , it is unclear whether there is any potential for energy savings using alternative expansion devices. DOE has proposed

e nergy test s for miscellaneous refrigeration products using a single fixed ambient air temperature (90 °F for vapor

- compression cooled c abinets , non

- compressor refrigerators, and hybrid refrigeration products; 72 °F for ice makers and non

- compressor cooled cabinets ). A capillary tube can be designed to provide optimized performance for th e single test condition . Systems are generally desig ned to operate with evaporator exit conditions having little or no superheat during energy testing, thus maximizing use of the evaporator. In the lower ambient temperature typical in homes, the pressure available to move refrigerant through the capillary t ube is lower, thus possibly leading to increased superheat and less than optimum performance. An automatic valve could provide optimum performance for a wider range of operating conditions, but such4-7 improvement would not be reflected in energy testing. DOE has eliminated this option from further consideration.

4.2.14 Fluid Control or Solenoid Valve

Off

- cycle refrigerant migration reduces a refrigeration product’s efficiency by allowing warm and/or vapor

- phase refrigerant to pass into the portion of the refrigerati on system inside the cabinet. A fluid control or solenoid valve installed downstream of the condenser can be used to prevent such refrigerant migration. Research has demonstrated that solenoid valves can yield substantial energy savings. 3 A lthough many dua l

- zone cooled cabinets use similar solenoid valves to allow control of multiple compartments with a single compressor

, use of these valve s may present a possible reliability issue . Also, operation with an off

- cycle valve requires that the compressor motor be capable of start ing up against a substantial pressure difference. The starting windings of compressors that can do this reliably over the life of a refrigerator draw more power and hence reduce the compressor’s steady

- state efficiency. The different eff iciency levels of commercial refrigeration compressors designed for instant restart versus restart after pressure equalization have energy efficiency ratio ( EER ) ratings which differ by 10 percent or more. Such a difference would be expected for residentia l compressors operating with an off

- cycle valve, and this difference would more than neutralize any benefit accrued from using the off

- cycle valve. Hence, DOE has eliminated this option from further consideration.

4.2.15 Off

- Cycle Defrost, Reduced Energy for Auto matic Defrost, Adaptive Defrost, and
Hot

- Gas Bypass Defrost

DOE has identified a few cooled cabinet s that use active heater defrost; however, the vast majority of miscellaneous refrigeration products use passive (off

- cycle) or manual defrost. Because these four design options are only relevant to products that use active heater defrost, they will not be applicable to most products. Hence, DOE has eliminated th ese option s from further consideration.

4.2.16 Electronic Temperature Control

DOE has not identified any relevant information showing the energy benefit of electronic temperature control. Potential benefits of electronic control when operating with single

- speed compressors are fine

- tuning of the run times and fine

- tuning of the cut

- in a nd cut

- out temperatures. While there may be potential for incremental improvement associated with such fine

- tuning, the lack of data supporting claims for energy savings make it difficult to properly analyze this option.4-8 4.2.17 Conversion to Alternative Refrigera tion System
Thermoelectric cooling technolog y currently do es not achieve efficiency levels which make it attractive as a design option alternative to vapor compression technology for improving cooled cabinet energy efficiency. Because data on the efficienc y of thermoelectric modules is limited, DOE conducted energy consumption and reverse

- heat

- leak testing to calculate the coefficient of performance ( COP ) of five thermoelectric refrigerators. During the reverse

- heat

leak test, DOE placed electrical heaters inside the refrigerators and determined the heater wattage necessary to maintain a refrigerator cabinet temperature of 90 °F in an ambient temperature of approximately 39 °F, corresponding to the reverse of the conditions required for the energy test. DOE calculated COP for thermoelectric modules using Equation 1 :

Equation 1

CCC = Q h eeeee ( r − ∑ f )

Where: Q H is the average power of the heater during the reverse

- heat

- leak test, in Watts; P ref is the average power of the refrigerator at a compartment temperature of 39 °F, determined during the energy test, in Watts; and P fan is the sum of the average power of a ll fans in the refrigerator, in Watts.

These test results , which account solely for the efficiency of the refrigeration system in that they do not include parasitic fan power, are presented in Table 4.2

. 1

.
Table 4.2

. 1 Thermoelectric COP Data Storage Volume (ft 3 ) COP 0.25 0.093 0.87 0.16

1.6 0.14 1.7 0.18 1.7 0.14

In comparison, the lowest compressor COP in the capacity range most utilized by miscellaneous refrigeration products (300

- 400 Btu/hour) is 0. 9 (equivalent to an EER of 3.0), which is five to ten times the COP measured for the thermoelectric modules as listed above. Hence, DOE has not considered conversi on to thermoelectric technology as a design option for
vapor

- compression products in the engineering analysis. DOE has also screened out heat pipes, which are only implemented as part of thermoelectric refrigeration systems, from its cooled cabinet analysi s.
Because vapor

- compression technology is more efficient than thermoelectric technology, DOE has considered conversion to vapor compression as a design option for non

- compressor4-9 cooled cabinets. However, DOE has not considered this design option for non

- c ompressor refrigerators because vapor

- compression refrigerators are part of DOE’s existing authority for coverage; they are part of a different set of product s that have their own different standard levels.

4.2.18 Component Location
Locating the compressor at the top of the cooled cabinet was noted as a potential technology option. However, this change would increase structural requirement s for the cabinet, increase risk of product tip

- over, and provide much less practical use of spac e from the consumer perspective. It also makes design for re

- evaporation of defrost water more challenging. It is unlikely that the savings would justify all of these drawbacks.

Another option is to locate the evaporator fan motor outside the cabinet to r educe internal loads from the heat loss of the motor. Evaporator fan motor input wattages are now in the range of 3 W to 7 W, with fan blade efficiency in the range of 20 percent to 30 percent and motor efficiency in the range of 20 percent to 50 percent

. Hence, load reduction associated with moving the motor loss outside the cabinet is only in the range of 1 W to 5 W for the portion of time during which the evaporator fan is in operation , which is typically less than 50 percent of total operating time . The loss associated with the added infiltration and conduction is likely to be comparable to th e savings from the fan relocation . Additional issues with this approach include reliability, reduced design flexibility, and the fact that reduction of motor losses (by using more efficient fan motors) may be a more effective approach to reducing the impact of the fan motor power input.

No options for relocation of components have been identified which merit further consideration in the engineering analysis.

4.3 REMAINI NG DESIGN OPTIONS

Table 4.3

. 1 list s the design options that were retained by DOE for cooled cabinets and

non

- compressor refrigerators , the two product categories for which DOE performed design option analysis

. Each of the se technologies w ere considered in the engineering analysis.4-10 Table 4.3

. 1 Retained Design Options Design Option Cooled Cabinets Non

- Compressor Refrigerators Improved compressor efficiency  Variable

- speed compressors  Forced

- convection evaporator  Higher

- efficiency fan motors  Increased insulation thickness   Vacuum

- insulated panels   Improved resistivity of glass door  Conversion to vapor compression  Heat pipe 4-11 REFERENCES

1 < http://www.embraco.com/wisemotion/Default.aspx>(Accessed September 19, 2014)

2 U.S. Department of Energy

- Office of Codes and Standards. Technical Support Document: Energy Efficiency Standards for Consumer Products: Refrigerators, Refrigerator

- Freezers, and Freezers , September, 2011. Washington, DC. EERE

- 2008

- BT

- STD

- 0012.

3 Coulter, W.H. and Bullard, C.W. “ An Experimental Analysis of Cycling Losses in Domestic Refrigerator

Freezers,” ASHRAE Transactions , 1997. Vol. 103, Pt. 1.