CHAPTER 5. ENGINEE RING ANALYSIS

TABLE OF CONTENTS

5.1 INTRODUCTION ........................................................................................................... 5-3 5.2 METHODOLOGY OVERVIEW .................................................................................... 5-3 5.3 COST MODEL ................................................................................................................ 5-4 5.3.1 Manufacturer Selling Price Estimates.................................................................. 5-4 5.3.2 Downstream Analyses .........................................................................................5-5 5.3.3 Structure of the Cost Model Spreadsheet.............................................................5-5 5.3.4 Material Prices .....................................................................................................5-6 5.3.5 Results..................................................................................................................5-7 5.4 ENERGY CONSUMPTI ON MODEL ............................................................................ 5-7 5.4.1 Screened-In Technologies.................................................................................... 5-7 5.4.2 Screened-In Technologies Not Considered in the Engineering Analysis............5-8 5.4.2.1 Higher Efficiency Evaporator and Condenser Fan Blades ......................5-8 5.4.2.2 Low-Pressure Differential Evaporators ................................................... 5-8 5.4.2.3 Defrost Mechanisms ................................................................................ 5-9 5.4.3 Design Options..................................................................................................... 5-9 5.4.3.1 Higher Efficiency Lighting and Ballasts..................................................5-9 5.4.3.2 Higher Efficiency Evaporator Fan Motors ............................................5-11 5.4.3.3 Evaporator Fan Controls........................................................................ 5-12 5.4.3.4 Improved Evaporator Design................................................................. 5-12 5.4.3.5 Insulation Increases or Improvements ................................................... 5-14 5.4.3.6 Improved Glass Pack ............................................................................. 5-14 5.4.3.7 Higher Efficiency Condenser Fan Motors .............................................5-15 5.4.3.8 Increased Condenser Surface Area ........................................................ 5-15 5.4.3.9 Higher Efficiency Compressors............................................................. 5-17 5.4.4 Baseline Specifications ......................................................................................5-17 5.4.5 Non-Numerical Assumptions............................................................................. 5-20 5.4.6 Numerical Constants and Assumptions ............................................................. 5-20 5.4.7 Model Components............................................................................................5-21 5.4.7.1 Component Energy Consumption.......................................................... 5-22 5.4.7.2 Compressor Energy Consumption ......................................................... 5-23 5.4.7.3 Component Load Model ........................................................................ 5-23 5.4.7.4 Radiation Load Model ........................................................................... 5-23 5.4.7.5 Conduction Load Model ........................................................................5-24 5.4.7.6 Infiltration Load Model..........................................................................5-24 5.5 COST-EFFICIENCY CURVES .................................................................................... 5-25 5.6 RESULTS ...................................................................................................................... 5-32 REFERENCES ..................................................................................................................... .....5-33

LIST OF TABLES

5-1Table 5.3.1 Major Manufacturing Processes .............................................................................. 5-6 Table 5.3.2 Calculated Core Case MSP ...................................................................................... 5-7 Table 5.4.1 Performance Details for “Class A Lighting” Design Option .................................5-10 Table 5.4.2 Performance Details for “Class B Lighting” Design Option .................................5-11 Table 5.4.3 Performance Details for “E vaporator Fan Motor” Design Option ........................5-12 Table 5.4.4 Performance Details for “Improve d Class A Evaporator Coil” Design Option ....5-13 Table 5.4.5 Performance Details for “Improve d Class B Evaporator Coil” Design Option ....5-13 Table 5.4.6 Properties of Standard a nd Enhanced Class B Evaporator Coil ............................5-13 Table 5.4.7 Properties of Standard a nd Enhanced Class A Evaporator Coil ............................5-14 Table 5.4.8 Performance Details for “Improved Glass Pack” Design Option ..........................5-15 Table 5.4.9 Performance Details for “Improved Glass Pack” Design Option ..........................5-15 Table 5.4.10 Performance Details for “Impr oved Class A Condenser Coil” Design Option ...5-16 Table 5.4.11 Performance Details for “Impr oved Class B Condenser Coil” Design Option ...5-16 Table 5.4.12 Properties of Standard a nd Enhanced Class A Condenser Coil ............................5-16 Table 5.4.13 Properties of Standard a nd Enhanced Class B Condenser Coil ............................5-17 Table 5.4.14 Baseline Specifications ........................................................................................ 5-18 Table 5.4.15 Class A Equipmen t Class Baseline Specifications .............................................. 5-19 Table 5.4.16 Class B Equipmen t Class Baseline Specifications .............................................. 5-19 Table 5.4.17 Energy Consumption Model Numerical Constants and Assumptions .................5-21 Table 5.4.18 Engineering Constants ......................................................................................... 5-21 Table 5.5.1 Cost-Efficiency Data for th e Small-Size Class A Equipment Class ......................5-27 Table 5.5.2 Cost-Efficiency Data for th e Medium-Size Class A Equipment Class .................5-28 Table 5.5.3 Cost-Efficiency Data for th e Large-Size Class A Equipment Class ......................5-29 Table 5.5.4 Cost-Efficiency Data for th e Small-Size Class B Equipment Class ......................5-30 Table 5.5.5 Cost-Efficiency Data for th e Medium-Size Class B Equipment Class ..................5-31 Table 5.5.6 Cost-Efficiency Data for th e Large-Size Class B Equipment Class ......................5-32

LIST OF FIGURES

Figure 5.3.1 Components of MSP ............................................................................................... 5-5 Figure 5.3.2 Full Production Cost Assessment Stages ............................................................... 5-5 Figure 5.4.1 Components of th e Energy Consumption Model ................................................. 5-22 Figure 5.5.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class .................5-27 Figure 5.5.2 Cost-Efficiency Curve for th e Medium-Size Class A Equipment Class ..............5-28 Figure 5.5.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class .................5-29 Figure 5.5.4 Cost-Efficiency Curve for th e Small-Size Class B Equipment Class ..................5-30 Figure 5.5.5 Cost-Efficiency Curve for th e Medium-Size Class B Equipment Class ..............5-31 Figure 5.5.6 Cost-Efficiency Curve for th e Large-Size Class B Equipment Class ..................5-32

5-2CHAPTER 5. ENGINEERING ANALYSIS

5.1 INTRODUCTION

The engineering analysis establishes the rela tionship between ma nuf acturer selling price (MSP) and daily energy consumption (DEC), measur ed in kilowatt hours pe r day (kWh/day), for the refrigerated beverage vending machines covered in this rulemaking. This cost-efficiency relationship serves as the basis for cost/ben efit calculations for individual customers, manufacturers, and the Nation. In determining th is relationship, the U.S. Department of Energy (DOE) estimates the increase in the manufacturer selling price associated with technological changes that reduce the energy cons umption of the baseline models.

The primary inputs to the engineering analys is are baseline information, data for each equipment class addressed in the market and te chnology assessment (chapter 3 in the TSD) and technology options from the screening analysis (c hapter 4 in the TSD). Additional inputs include cost and energy consumption data that DOE estimated using a cost model and an energyconsumption model, respectively. The primary output of the engineering analys is is a set of costefficiency curves that show the relationship between MSP and daily energy consumption. In the subsequent markups analysis (c hapter 6 in the TSD), DOE determines customer prices by applying distribution markups, sale s tax, and contractor markups to the MSPs developed in the engineering analysis. After applyi ng these markups, the data serve as inputs to the energy use characterization (chapter 7 in the TSD) and th e life-cycle cost and payback period analyses (chapter 8 in the TSD).

In this chapter, DOE discusses representative baseline units for each class, the methodology used to develop MSPs, the methodol ogy used to estimate energy consumption, and output cost-efficiency curves.

5.2 METHODOLOGY OVERVIEW

This section describes the analytical me thodology used in th e engineering analysis. In this rulemaking, DOE is adopting a design-optio n approach, which calculates the incremental costs of adding specific design options to a ba seline model. For each equipment class, DOE analyzed three different machine sizes to assess how energy use varies with refrigerated volume. A small-, medium-, and large-sized machine we re picked for Class A and Class B equipment based on machines currently on th e market. See chapter 3 of the TSD for a detailed description of the Class A and Class B e quipment classes and section 5.4.4 below for additional detail on the different size machines analyzed.

For each eq uipment class and size, DOE developed a core case cost using a manufacturing cost model. The core case cost is the full production cost of the structure, walls, doors, shelving and fascia of the case, but does not include the cost of any energy-using components. DOE developed pricing for each de sign option and added the design option pricing to the core case costs to arrive at the fully absorbed production cost for each equipment class and size at various efficiency levels . To derive the MSP of a machin e at each efficiency level, DOE

5-3added a typical profit to the fully absorbed cost of production. DOE also calculated the impact of each des ign option on DEC using an energy consump tion model. The results of the engineering analysis are a set of cost-efficiency curves, in the form of MSP versus DEC, for three sizes of each equipment class.

5.3 COST MODEL

The cost mo del is a key analytical model used in constructing cost-efficiency curves. For beverage vending machines, the cost model was used to estimate the core case cost of a machine. The beverage vending machine cost model was ad apted from a cost model developed for DOE’s rulemaking on commercial refrigeration equipment (CRE). a DOE believes this approach is acceptable given the similarities in materials a nd manufacturing processes between the two types of equipment. Development of the CRE cost mode l involved the disassemb ly of a self-contained commercial refrigerator, an analysis of the materials and manufacturing processes, and the development of a parametric spreadsheet mode l. DOE modified the CRE model to apply to beverage vending machines using input from in terested parties on price estimates and its assumptions. Use of interested party input also confirmed the accuracy of the model adaptation.

5.3.1 Manufacturer Selling Price Estimates

The MSP includes the full cost of production and profit. The full producti on cost inclu des all direct and indirect costs to produce a unit. The manufacturer production cost is the sum of all the direct manufacturing costs: direct labor, direct material, and overhead (including investment depreciation) costs. The indirect costs for each unit are non-production cost elements, which include sales, general and admini strative, research and developmen t, and interest. To convert the full cost of production to MSP, a profit is a dded. The MSP includes all the production and nonproduction costs that make up the full production cost, as well as a profit. The components of MSP are shown in

Figure 5.3.1

. The cost of specific models

 or cost to an individual manufacturer to produce a refrigerated beverage vending machine

 will vary depending on the equipment’s precise design and features, actual manufactur ing processes, the equipment mix in the factory, and other production factors. There are also considerable differences in the levels of vertical integration that affect cost structure and, thus, the cost of equipment. Companies with a large market share and/or revenue base tend to be more vertically integrated than their smaller competitors. Yet, all manufacturers potentially buy at le ast some of their parts and/ or subsystems from outside vendors.

a See http://www.eere.energy.gov/buildin gs/appliance_standards/commercial_products.html for further detail on and validation of the CRE cost model.

5-4Figure 5.3.1 Components of MSP

5.3.2 Downstream Analyses

The MSPs derived in the engineering analysis are important inputs to the life-cycle cost analys is (LCC) and the manufacturer impact analysis (MIA). In the LCC, the MSPs are necessary to calculate the total installed cost of each unit. In the MIA, DOE constructs a number of scenarios that analyze how di fferent pricing schemes impact manufacturers financially. In the MIA, both MSP and the direct production cost components of MSP are important drivers of results. DOE discusses how the engineering analysis is used in the other analyses in chapters 8 (LCC) and 13 (MIA) of the TSD.

5.3.3 Structure of the Cost Model Spreadsheet

DOE used a detailed, component-focused ma nufacturing cost assessm ent methodology to estimate the full production cost of machines from each equipment class analyzed in the cost model. In doing so, DOE took into account many f actors that affect cost, including, for example, direct materials, direct labor, and factory overhead costs. Figure 5.3.2 shows the three major steps in generating the full production cost.

Raw Materials Fabrication Processes

Purchased Parts Finished Materials Assembly Processes Bill of Materials

Figure 5.3.2 Full Production Cost Assessment Stages

5-5The first step in the full production cost assessme nt was creating a complete and structured bill of materials (BOM) from the di sassembly of a commercial refrigerator with transparent doors. The commercial refrigerator was dismantled, a nd each part was characterized according to weight, manufacturing processes, dimensions, material, and quantity. The BOM includes the costs of materials, components, and fasteners. It also estim ates the cost of raw materials and purchased parts. DOE based assump tions about the sourcing of parts and in-house fabrication on industry experience, informati on in trade publications, and discussions with manufacturers. During the BVM rulemaking, DOE’s contractors conducted interviews and plant visits with manufacturers to guide the adaptation of the commercial refrigeration BOM. Information was gathered to account for equipmen t designs specific to BVMs and ensure that the model’s methodology and pricing were accurate.

After developing a detailed BOM, DOE iden tified the major manufacturing processes, listed in Table 5.3.1 , and developed a spreadsheet model. DOE estimated fabrication p rocess cycle times and entered them into the BOM. Fo r this analysis, $24.00 per hour was used as the average fully burdened labor rate based on typical annual wages and benefits of industry employees. In the final step of the cost assessment, DOE estimated assembly times and associated direct labor costs. Once the cost es timate for each unit was finalized, DOE prepared a detailed summary of relevant compon ents, subassemblies, and processes.

Table 5.3.1 Major Manufacturing Processes

Fabrication Finishing Assembly/Joining

Fixturing Washing Adhesive Bonding Stamping/Pressing Powder Coating Spot Welding

Brake Forming De-burring Seam Welding Cut and Shearing Polishing Inspecting & Testing Insulating

5.3.4 Material Prices

DOE determined the cost of raw ma terial s by using prices for copper, steel, and aluminum from the American Metals Market. 1 Prices for rifled and unrifled copper tubing were obtained directly from a tubing manufacturer. DOE noted that there have been drastic fluctuations in metal prices over the last few y ears. To account for these large fluctuations, DOE used prices of metals that reflect a 5-year av erage of the Bureau of Labor Statistics Producer Price Indices (PPIs) spanning 2002 to 2006 with an adjustment to 2008$. 2 DOE used the PPIs for steel mill products and coppe r rolling, drawing, and extrudi ng, and adjusted to 2008$ using the gross domestic product implicit price deflator. 3

Between 2003 and 2006, the price of steel rose over 60 percent and the price of copper rose over 140 percent. Because DOE used a 5-year average in material prices from 2002 to 2006, these drastic increases are normalized to better represent long-term ma terial price averages.

5-65.3.5 Results

In order to calculate how additional com ponents increase MSP, DOE first calculated a core case M SP for each equipment class. The MSP of each core case lacks any of the design options studied by DOE in the engineering analys is. Calculating the MSP of a unit without any studied design options allows DOE to construct the cost-efficiency relationship in conjunction with the energy consumption model. Table 5.3.2 displays the core case MSP calculated for each equipm ent class.

Table 5.3.2 Calculated Core Case MSP
Equipment Class 12-Ounce Can Capacity Size Designation Calculated Core MSP $ A 300 Small 1,449 A 400 Medium 1,758 A 500 Large 1,906 B 450 Small 1,159 B 650 Medium 1,330 B 800 Large 1,382

5.4 ENERGY CONSUMPTION MODEL

The energy consumption m odel is another key an alytical model used in constructing costefficiency curves. This model estimates the DE C of beverage vending machines in kWh/day at various performance levels using a design- options approach. DOE developed the energy consumption model as a Microsoft Excel spreadsh eet and is making the model available to the public on DOE’s website at http://www1.eere.energy.gov/build ings/appliance_standards/comm ercial/beverage_machines.ht ml. Appendix A of the TSD provides in structions for usi ng the spreadsheet.

For a given equipment class, the model estimates a DEC value for the baseline and DEC values for each of several performance levels above the baseline. The model calculates energy consumption at each performance level separatel y. DOE selected ENERGY STAR Tier 1 as the baseline level for each equipment class and machine size. 4 For the baseline level, DOE calculated a corresponding full pr oduction cost using the cost model (described in section 5.3 above). For each leve l above the baseline, DOE used the cost increases of the various design options to recalculate the full production cost.

5.4.1 Screened-In Technologies

In the ma rket and technology assessment (chapter 3 of the TSD), DOE defined an initial list of technologies that can be used to reduce the energy consum ption of refrigerated beverage vending machines. DOE then analyzed the following technology options:

 higher efficiency lighting

 higher efficiency lighting ballasts

 higher efficiency evaporator fan motors

 evaporator fan motor controllers

5-7 higher efficiency evaporator fan blades

 improved evaporator design

 low-pressure differential evaporators

 insulation increases or improvements

 defrost mechanism

 improved glass pack (for Class A machines only)

 higher efficiency condenser fan motors

 higher efficiency condenser fan blades

 improved condenser design

 higher efficiency compressors

5.4.2 Screened-In Technologies Not Consid ered in the Engineering Analysis

In the screening analy sis (cha pter 4 of the TSD), DOE narrowed this list by eliminating those technologies that can re duce the annual energy consumption of beverage vending machines but do not reduce DEC. DOE then screened out thos e technologies that we re not feasible, were not practical to manufacture, reduced equipment utility, or were considered unsafe.

The remaining list of screened-in technologi es became an input to the engineering analysis. However, for reasons noted below, DOE did not incorporate all of these technologies in the energy consumption model. These include hi gher efficiency evaporator and condenser fan blades, low-pressure differential ev aporators, and defrost mechanisms.

5.4.2.1 Higher Efficiency Evaporator and Condenser Fan Blades

Higher efficiency evapor ator and condens er fan blades reduce motor shaft power requirements by moving air more efficiently. Current BVM designs use stamped sheet metal or plastic axial fan blades. These fan blades are lig htweight and inexpensive. DOE was not able to identify any axial fan blade techno logy that is significantly more efficient than what is currently being used but did identify one alternative fan blade technology that might improve efficiency: tangential fan blades. These blades can produce a wide, even airflow im proving air distribution across the evaporator coil. Improved air distributi on has the potential to increase the saturated evaporator temperature (SET) and reduce compre ssor power. However, tangential fan blades are small and less efficient at moving air, and thus require greater motor shaft power. Because of these competing effects, DOE did not consider tangential fan blades as a design option.

5.4.2.2 Low-Pressure Differential Evaporators

Low-pressure differential evaporators redu ce energy consumption by reducing the power required by evaporator fan motors. However, in space-constrained equip ment, such as beverage vending machines, this reduction usually comes from a decrease in evaporator coil surface area. This surface area reduction genera lly requires a lower SET to ach ieve the same discharge air temperature and cooling potential, which redu ces compressor efficiency. Because of these competing effects, DOE did not consider low-pressure differential evaporators as a design option.

5-85.4.2.3 Defrost Mechanisms

Beverage vending machine evaporator coil de frosting is typically accomplished with offcycle defrost. Because off-cycle defrost uses no energy (and decreases compressor on-time), there is no defrost mechanism to reduce defros t energy consumption. Therefore, DOE did not consider it as a design option.

5.4.3 Design Options

After conducting the screening analysis and remo ving from consideration those technologies described above, the following technologies were impl emented as design options in the energy consumption model:

 higher efficiency lighting and ballasts (a combination of the first two design options listed above)

 higher efficiency evaporator fan motors

 evaporator fan motor controllers

 improved evaporator design

 insulation increases or improvements

 improved glass pack (for Class A machines)

 higher efficiency condenser fan motors

 improved condenser design

 higher efficiency compressors

Each design option has two to four technology levels, ranging from the worst performing to the best performing technology. The design opti ons and the technology levels for each design option are described below.

5.4.3.1 Higher Efficiency Lighting and Ballasts

Lighting is an important characteristic of beverage vending machines: it m akes the product visible to the consumer in Class A m achines and provides backlighting for product advertising in Class B machines. Lighting system s typically operate continuously and provide an opportunity for significant energy savings. As lighting system effi ciency increases, total energy consumption can be decreased in two ways: reducing the lighting system’s electricity consumption and reducing the heat generated inside the refriger ated volume, which reduces the compressor work.

It is important to avoid a reduction in the illu mination of the machine front (in the case of Class B machines) or of the vended product (in the case of Class A machines) with more efficient lighting design options, because it decr eases equipment utility – specifically, advertising ability. Therefore, DOE made every effort to ma intain constant system utility among the lighting design options. This approach meant that DOE had to consider lighting as a system, rather than distinguishing lamps and ballasts as separate design options. This approach became more important when considering light emitting diode (LED) lighting systems, which do not require ballasts like fluorescen t lighting systems.

5-9Although LED systems generally have a lower e fficacy than the fluorescent system s they replace, the fixtures used with LEDs direct light more effectively. As a result, the total lumen output of LED systems is lower than that of co mparable fluorescent systems, but the amount of light incident on a surface (illuminance) is roughly equivalent. BVM ma nufacturers, lighting manufacturers, and other tec hnical experts indicated that current LED technology provides adequate product lighting for Class A machines a nd, in most cases, is comparable to fluorescent lighting. For Class B machines, DOE origina lly believed that LED technology would be adequate, but BVM manuf acturers indicated that utility would be lost.

To account for variations in design between equipment classes, DOE used two lighting design options in the energy-consumption model. The first was for Class A machines and the second was for Class B machines.

Class A machines illuminate the beverage co ntainers being vended. Lamps must be sized to fit within the refrigerated space. DOE used 4- foot fluorescent lamps, based on the size of the transparent display front in machines currently on the market. DOE started with a minimum technology of T12 fluorescent lamps and magnetic ba llasts, but today is us ing a baseline of T8 fluorescent lamps with electronic ballasts, based on market data and conversations with BVM manufacturers. Additionally, these lamps were re quired to have a color rendering index (CRI) of approximately 80, which is typical for this type of equipment.

After the ANOPR, DOE re-evaluated its engi neering analysis assu mptions for Class A LED lighting system designs. The assumptions used in the ANOPR were adapted from those used in the CRE NOPR for Vertical Closed Transparent equipment. For the BVM NOPR engineering analysis, DOE modified its LED design assumptions by; (1) updating LED energy consumption data to be consistent with th e changes made between the CRE NOPR and CRE final rule; and (2) updating the LED system pricing based on commercially available LED retrofit kits which are designe d specifically for Class A beverage vending machines. The energy consumption (lamp rated power) for a 4-ft, 1 row LED fixture decrea sed from 27.2 W in the ANOPR to 11.6 W for the NOPR. In addition, th e efficacy increased from 50 Lu/W to 53.9 Lu/W. The cost of the same fixture in creased from $50.81 in 2007$ to $60.00 in 2008$. The LED specification modifications are reflect ed in the data in Table 5.5.1 below.

Table 5.4.1 Performance Details for “Class A Lighting” Design Option

Level Description Lamp Type Lamp Rated Power [watts (W)] Lamp Rated Light Output [Lumens] System Efficacy [Lumens/ W] System Light Output [Lumens] T12 4-ft T12, Magnetic F34T12 34.0 2,650 68.6 2,332 T8 4-ft T8, Electric F32T8 32.0 2,850 85.0 2,679

T8S 4-ft “Super” T8, Electric F32T8/HL 32.0 3,100 91.4 2,697 LED 4-ft LED 4-ft LED 11.6 625.6 53.9 625.6

5-10Traditionally, Class B machines use 5- or 6- foot, high-output (HO) T12 fluorescent lamps and ma gnetic ballasts to draw consumers’ atten tion to product logos and signal that the machine is functioning. DOE used this configuration as the minimum technology option. However, with the increase in demand from customers for ENERGY STAR qualified machines, BVM manufacturers have started using T8 fluorescent lamps, so DOE used this as the baseline. Some beverage vending machine customers dictate certain size fluorescent lamps (to reduce the number of lamp types that lighti ng repair personnel carry on their trucks). As a result, DOE used a 4-foot and a 2-foot T8 lamp to replace a 6-f oot T12 lamp. These lamps were also required to have a CRI of approximately 80, which is typical for this type of equipment.

After the ANOPR, Class B LED lighting system assumptions were also modified. The assumptions used in the ANOPR were also ad apted from those used in the CRE NOPR for Vertical Closed Transparent equipment. Fo r the NOPR engineering analysis, Class B LED assumptions were modified by: (1) updating LE D energy consumption and pricing data to be consistent with the changes made between th e CRE NOPR and CRE final rule; and (2) updating the fixture replacement ratio when moving from a fluorescent to a LED lighting system. The energy consumption (lamp rated power) for a 6-ft , 1 row LED fixture de creased from 33.4 W in the ANOPR to 22.5 W for the NOPR. In addition, the efficacy increased from 50 Lu/W to 59.2 Lu/W. The cost of the same fixture in creased from $50.81 in 2007$ to $134.67 in 2008$. To model use of LED systems in Class B equipmen t for the ANOPR, DOE used a 1 to 1 fixture replacement ratio when substituting an LED li ghting system for the fluorescent system. As mentioned previously, manufactur ers commented that more LED fixtures than fluorescent fixtures are needed to sufficiently backlight a cl osed front machine. As a result, DOE increased the ratio to 1.5 to 1. For the NOPR, when the LED design option is implemented in the engineering analysis 1.5 LED fixt ures are used to replace each fluorescent fixture. The Class B LED specification modifications ar e reflected in the data in Table 5.4.2 below.

Table 5.4.2 Performance Details for “Class B Lighting” Design Option

Level Description Lamp Type Lamp Rated Power

[W] Lamp Rated Light Output [Lumens] System Efficacy [Lumens /W] System Light Output [Lumens]

T12HO 6-ft., T12 HO Magnetic F72T12/ HO/SP 85.0 6,550 64.9 5,960

T8 2-ft. T8 & 4–ft. T8 Electric F17T8 & F32T8 49.0 4,250 90.4 3,910

LED 6-ft. LED - 22.5 2,001 59.2 2,001

5.4.3.2 Higher Efficiency Evaporator Fan Motors

In conjunction with fan blades, fan motors are necessary to transfer heat from the refrigerated space to the refrigerant. In most situations they operate nearly continuously and, therefore, use a significant amount of energy. As motor efficiency increases, energy consumption decreases due to a direct reduction in electr icity consumption and wa ste heat inside the refrigerated space.

5-11Table 5.4.3 shows details for the evaporator fa n motor design option. Currently, DOE considers shaded-pole motors (SPM) as the mi nimum technology, permanent split capacitor (PSC) motors as the mid-level t echnology, and brushless direct cu rrent (DC) or electronically commutated motors (ECMs) as the maximum technology. The motor efficiencies listed in Table 5.4.3 are from Energy Savings Potential for Co mmercial Refrigeration Equipment
, prepared by Arthur D. Little in 1996. 5

Table 5.4.3 Performance Details for “Evaporator Fan Motor” Design Option
Shaded-Pole Motor (SPM) Permanent Split Capacitor (PSC) Motor Brushless DC Motor (ECM) Rated Power [W] Actual Power

[W] Efficiency Actual Power

[W] Efficiency Actual Power

[W] Efficiency

15.0 75.0 20.0% 33 45.5% 20.5 73.2% 9.0 53.0 17.0% 21 42.9% 12.5 72.0% 6.0 40.0 15.0% 15 40.0% 8.5 70.6%

5.4.3.3 Evaporator Fan Controls

Beverage vending machine m anufacturers typi cally design evaporator fans to operate continuously. Circulating warm air through the ca se during compressor off-times prevents the evaporator coil from icing over. However, manuf acturers indicated during interviews that, under typical conditions, the evaporator fan is not required to run du ring all compressor off-times to keep the coils ice-free. Because of this, DOE deve loped a design option with controls to turn offthe evaporator fan during compressor off-time and a period of fan operation to accomplish offcycle defrost. Based on discussions with out side experts and beverage vending machine manufacturers, DOE estimated that a total of 1.5 hours of off-cycle defrost operation would be required during a 24-hour period. To assess the total co st of this design option, DOE took into account the additional cost of parts, engineering, and incr eased labor for assembly.

5.4.3.4 Improved Evaporator Design

Evaporator coils are an other component necessa ry to transfer heat from the refrigerated space to the refrigerant. Table 5.4.4 and

Table 5.4.5 show details for the evaporator co il design option. Based on available information, DOE considered a m inimum and a maximum technology level for this design option. DOE analyzed different ev aporator coils given the differe nces in design load between Class A and Class B machines. For each level, DOE specified an overall UA-value b and a coil cost. The UA-value is normalized to the standard coil, and the coil cost is normalized to the heat removal capacity of the coil. This allowed DOE to apply these details of coil design across all equipment sizes. In consultation with outside experts, DOE determined that the same coil improvements applied to different-sized coils w ould result in similar performance improvements.

b The overall UA-value is the product of the overall heat tr ansfer coefficient (British thermal units per hour (Btu/h)- ft 2 -°F) and the total surface area (ft 2 ) of the coil. This value can be derived from the total heat transfer rate of the coil (Btu/h) divided by the log mean temperature difference of the air and refrigerant flows ( Δ T LM ).

5-12Table 5.4.4 Performance Details for “Improved Class A Evaporator Coil” Design Option

Level Description Normalized UA [-] Normalized Coil Cost [$/Btu/h]
FEV1 Standard Coil 1 $0.0058 FEV2 High-Performance Coil 1.605 $0.0125

Table 5.4.5 Performance Details for “Improved Class B Evaporator Coil” Design Option

Level Description Normalized UA [-] Normalized Coil Cost [$/Btu/h]
ZEV1 Standard Coil 1 $0.0066 ZEV2 High-Performance Coil 1.646 $0.0143
The details of coil construction (shown in Table 5.4.6 and Table 5.4.7 ) were based on a baseline and prototype high-performa nce coil evaluated in a study by the Refrigeration and Thermal Test Center (RTTC) at Southern California Edison. 6 The high-performance coil uses a combination of enhancements to the heat transf er surfaces that increased its overall UA-value. These enhancements include a slightly higher fi n pitch and different fi n material. In summary, these changes result in an increased UA-value a nd increased coil cost. The increase in UA-value leads to an increase in the coil SET. Because comp ressor performance is dire ctly related to SET, reductions in total case energy consumption are r ealized through an improved energy efficiency ratio (EER) at the condensing unit. In consultation with outside e xperts, DOE determined that the same coil improvements applied to differently size d coils at different temperatures would result in similar UA-value improvements.

Table 5.4.6 Properties of Standard a nd Enhanced Class B Evaporator Coil Property Standard Co il High-Performance Coil Overall Width (in) 24 24 Overall Height (in) 6 6 Overall Depth (in) 3 3 Tube Rows per Circuit 15 15 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 0.012 Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Dimensions (in) 3 x 6 3 x 6 Fin Pitch (fins per inch) 6 7

5-13Table 5.4.7 Properties of Standard a nd Enhanced Class A Evaporator Coil Property Standard Co il High-Performance Coil Overall Width (in) 12 12 Overall Height (in) 8 8 Overall Depth (in) 3 3 Tube Rows per Circuit 28 28 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 0.012 Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Dimensions (in) 3 x 8 3 x 8 Fin Pitch (fins per inch) 7 8

5.4.3.5 Insulation Increases or Improvements

Increasing or improving insulation decrea ses the conduction load, which reduces

com pressor energy consumption. DOE looked at two different methods of reducing the conduction load. The first method was a 1/8-inch in crease in insulation thickness in all insulated panels. DOE assumed this addition required the m achine to expand outward rather than inward, because an expansion inward would likely re duce the capacity to store canned or bottled beverages. DOE also accounted for the increased core case costs (due to th e larger shell), design time, and fixture retooling.

The second method DOE explored was changi ng the insulation material. Currently, beverage vending machines use foamed-in-place pol yurethane as the primary insulation material. After discussions with insula tion manufacturers, industry expe rts, and BVM manufacturers, DOE concluded that there are no significant va riations among different polyurethane foams and blowing agents. Thus, DOE did not consider im provements in polyurethane foams or blowing agents. DOE also did not consider vacuum pane ls because they cannot provide the structural support of foamed-in-place designs, and cannot accep t the bolts and fasteners typically used on the skins and frame that house the insulation. However, DOE did consider aerogels as a replacement for foamed-in-place polyurethane. DOE considered an open cell, silica-based aerogel that comes in an expansion pack and is expanded to fit th e insulation cavity.

5.4.3.6 Improved Glass Pack

An im proved glass pack design option only a pplies to Class A machines. Improvements to the glass pack (a prefabricated assembly of gl ass sheets, coatings, framing, and fill gas) result in less heat transfer to the refrigerated volume by radiati on and conduction. This reduces the heat load on the refrigerant and hence the comp ressor load, thus reducing compressor energy consumption. The glass pack can be improved se veral ways, including adding panes of glass, adding low-emissivity (low-E) coating, changing fr om air fill to argon fill, and changing from an aluminum frame to a vinyl frame. Rather than examine each variation as an individual design option, DOE looked at three differe nt option packages, shown in Table 5.4.8

.

5-14The design options shown in Table 5.4.8 were then entered into WINDOW 5.2 7 to yield U-values c that account for heat transfer due to ra diation and conduction at each of the test conditions set forth in American National Sta ndards Institute (ANSI)/ American Society of Heating, Refrigeration and Air-Conditioni ng Engineers (ASHRAE) Standard 32.1–2004, Methods of Testing for Rati ng Vending Machines for Bottled, Canned, and Other Sealed Beverages

. 8 Table 5.4.9 catalogs the resulting U-values.

Table 5.4.8 Performance Details for “I mproved Glass Pack” Design Option Variable Baseline Enhanced Super Enhanced Frame Material Aluminum Aluminum Vinyl Number of Panes 2 2 3 Glass Type: Panel 1 Clear Clear Clear Glass Type: Panel 2 Clear Low-E Low-E Glass Type: Panel 3 - - Clear Gas Fill Air Argon Argon

Table 5.4.9 Performance Details for “I mproved Glass Pack” Design Option

Level Description Overall U-Factor at the ASHRAE 32.1 75  F Test Condition [Btu/h-ft-°F] Overall U-Factor at the ASHRAE 32.1 90  F Test Condition [Btu/h-ft-°F] DOOR 1 Baseline 0.704 0.717 DOOR 2 Enhanced 0.447 0.455 DOOR 3 Super-Enhanced 0.292 0.298

5.4.3.7 Higher Efficiency Condenser Fan Motors

Performa nce details for the condenser fan motor design option are identical to those shown in Table 5.4.3 . As with evaporator fan motors, the SPM is the minimum technology level, the PSC mo tor is the mid-le vel technology, and the DC motor or ECM is the maximum technology level. Because condenser fan motors are outside the re frigerated space, efficiency improvements only impact the direct electrical consumption of the motors and not the total case heat load.

5.4.3.8 Increased Condenser Surface Area

Condenser coils reject heat from the refriger ant to the am bient air. Based on available information, DOE considered both minimum an d maximum technology leve ls for this design option. For each level, DOE specified an ove rall UA-value and a coil cost, shown in Table 5.4.10 and Table 5.4.11 . The UA-value is normalized to the standard coil, and th e coil cost is normalized to the heat removal capacity of the co il. This allowed DOE to apply these details of coil design across all equipment sizes . In consultation with outside experts, DOE determined that the same coil improvements applied to different-s ized coils would result in similar performance improvements.

c U-value is a measure of air-to-air heat transmission (lo ss or gain) due to thermal conductance and the difference in indoor and outdoor temperatures.

5-15Table 5.4.10 Performance Details for “Improve d Class A Condenser Coil” Design Option

Level Description Normalized UA [-] Normalized Coil Cost [$/Btu/h]
FCO1 Standard Coil 1 $0.006 FCO2 High-Performance Coil 1.74 $0.015

Table 5.4.11 Performance Details for “Improve d Class B Condenser Coil” Design Option

Level Description Normalized UA [-] Normalized Coil Cost [$/Btu/h]
ZCO1 Standard Coil 1 $0.006 ZCO2 High-Performance Coil 1.67 $0.019
As previously mentioned, detail s of coil construction (shown in Table 5.4.12 and Table 5.4.13 ) were based on a baseline and prototype hi gh-performa nce coil evaluated in a study by RTTC. The high-performance coil uses a combina tion of enhancements to the heat transfer surfaces that increased its overall UA-value. Th ese enhancements include higher fin pitch and different fin material. In sum, these improvements give the prototype coil a higher UA-value, allowing the coil to run at a satu rated condenser temperature (SCT ) cooler than the baseline coil while maintaining the same heat rejection rate. DOE did not consider ri fled tubing because the refrigerant flow rates in beverage vending mach ines are typically not high enough to trigger turbulent flow. Because compressor performance is directly related to SCT, reductions in total case energy consumption are realized through an improved EER at the condensing unit.

Table 5.4.12 Properties of Standard and Enhanced Class A Condenser Coil Property Standard Co il High-Performance Coil Overall Width (in) 21 21 Overall Height (in) 10 10 Overall Depth (in) 4 4 Tube Rows per Circuit 36 36 Number of Parallel Circuits 1 1 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 in 0.012 in Tubing Inner Surface Smooth Smooth Fin Material Aluminum Copper Fin Surface Flat Wavy Fin Pitch (fins per inch) 4 5

5-16Table 5.4.13 Properties of Standard and Enhanced Class B Condenser Coil Property Standard Co il High-Performance Coil Overall Width (in) 12.5 24 Overall Height (in) 10 10 Overall Depth (in) 2.25 3 Tube Rows per Circuit 28 16 Number of Parallel Circuits 3 2 Tubing Material Copper Copper Tubing Outer Diameter (in) 3/8 3/8 Tubing Wall Thickness (in) 0.012 in 0.012 in Tubing Inner Surface Smooth Rifled Fin Material Aluminum Aluminum Fin Surface Flat Flat Fin Pitch (fins per inch) 6 7

5.4.3.9 Higher Efficiency Compressors

In consultation with compressor ma nufacturers and external technical experts, DOE determined that two levels of technology were applicable for the compressor design option. The minimum technology level is a standard single-s peed hermetic compressor, and the maximum technology level is a high-efficien cy single-speed hermetic compre ssor (see chapter 4 of the TSD for a discussion of why variable-speed compresso rs were not considered). Reductions in total case energy consumption are realized through a reduction in compressor power consumption.

DOE collected performance data for standard single-speed hermetic compressors from several manufacturers over a range of capacities applicable to the covered equipment (1,000 – 4,000 Btu/h). This data set was used to l ook up appropriately sized compressors when developing each design-option curve (see section 5.4.7.2 below for information on the calculation of comp ressor ener gy consumption). Although seve ral compressor manufacturers produce high-efficiency compressors, little data are currently available on their performance. Therefore, DOE approximated a set of high-e fficiency compressors by adjusting the power consumption of the standard compressors using a constant multiplier. DOE developed this multiplier through research and consultation with experts.

5.4.4 Baseline Specifications

DOE defined baseline specifications for each equipment class. These specifications include dimensions, numbers of components, te mperatures, nominal po wer ratings, and other case features that are necessary to calculate the energy consumption of each equipment class. In conjunction with the typical technological level of each design option (see section 5.4.3 above), the baseline specifications define the energy c onsum ption and cost of the typical-efficiency equipment on the market. DOE also provided de tails on minimum technology options for design options that are typically below the efficiency of currently available equipment. DOE did this because a small portion of the market does not meet the voluntary ENERGY STAR Tier 1 level. Table 5.4.14 below shows the specifications and units that are defined for each equip ment class.

5-17Table 5.4.14 Baseline Specifications Specification Units Refrigerated Volume ft 3 Number of Lamps in Refrigerated Volume - Number of Lamps not in Refrigerated Volume - Number of Ballasts in Refrigerated Volume - Number of Ballasts not in Refrigerated Volume - Evaporator Fan Nominal Rated Wattage W (Watts) Number of Evaporator Fans - Condenser Fan Nominal Rated Wattage W Number of Condenser Fans - Average Refrigerated Volume Temperature F (Fahrenheit) Nominal SET F Nominal SCT F Nominal Discharge Air Temperature (DAT) F Nominal Compressor Sizing Btu/h Solid Wall Area (including the door for Class B Machines) ft 2 Glass Area ft 2 Baseline Air Infiltration lb/hour Load from Electronic Components (bill changers, LED displays, etc.) kWh
DOE established baseline specifications for each of the equipment classes modeled in the engineering analysis by reviewi ng available manufacturer data, se lecting several representative units from available manufacturer data, and then aggregating the physical characteristics of the selected units. The baseline specifications were chosen so that the baseline machines met ENERGY STAR Tier 1 criteria (see chapter 3 of the TSD for further details on the criteria). This process created a representative unit for each eq uipment class with aver age characteristics for physical parameters (e.g., volume, wall area), and typical performan ce for energy-consuming components (e.g., fans, lighting).

DOE modified some of the baseline specifi cations assumed in th e ANOPR to represent equipment currently available on the market. Fo r Class A, DOE modified the exterior case dimensions, can capacities, and other associated specifications. For Class B, DOE verified the assumed can capacities, but modified the exte rior case dimensions and other associated specifications. For both classes, changes to cas e dimensions resulted in modifications to infiltration loads, refrigerated volumes and exterior wall areas. Table 5.4.15 and Table 5.4.16 show the results for each equipment class and size. Table 5.4.15 and Table 5.4.16 also include the 12-oz. can capacity of each si ze machine, for reference.

5-18Table 5.4.15 Class A Equipment Class Baseline Specifications Specification Small Medium Large Refrigerated Volume [ft 3 ] 17 22 34 12 oz. Can Capacity [#] 300 400 500 Number of Lamps in Refrigerated Volume [#] 2 2 2 Number of Lamps not in Refrigerated Volume [#] 0 0 0 Number of Ballasts in Refrigerated Volume [#] 0 0 0 Number of Ballasts not in Refrigerated Volume [#] 1 1 1 Evaporator Fan Nominal Rated Wattage [W] 9 9 9 Number of Evaporator Fans [#] 1 1 1 Condenser Fan Nominal Rated Wattage [W] 9 9 9 Number of Condenser Fans [#] 1 1 1 Average Refrigerated Volume Temperature [F] 36 36 36 Nominal SET [F] 8 8 8 Nominal SCT [F] 95 95 95 Nominal Discharge Air Temperature (DAT) [F] 19 19 19 Nominal Compressor Sizing [Btu/h] 2,400 2,900 2,900 Solid Wall Area (including the door for Class B Machines) [ft 2 ] 34 46 51 Glass Area [ft 2 ] 8 9 11 Baseline Air Infiltration [lb/hour] 7 8 11 Load from Electronic components (bill changers, LED displays, etc.) [kWh] 0.45 0.45 0.45

Table 5.4.16 Class B Equipment Cl ass Baseline Specifications Specification Small Medium Large Refrigerated Volume [ft 3 ] 17 22 26 12 oz. Can Capacity [#] 450 650 800 Number of Lamps in Refrigerated Volume [#] 0 0 0 Number of Lamps not in Refrigerated Volume [#] 2 2 2 Number of Ballasts in Refrigerated Volume [#] 0 0 0 Number of Ballasts not in Refrigerated Volume [#] 1 1 1 Evaporator Fan Nominal Rated Wattage [W] 9 9 9 Number of Evaporator Fans [#] 2 2 2 Condenser Fan Nominal Rated Wattage [W] 9 9 9 Number of Condenser Fans [#] 1 1 1 Average Refrigerated Volume Temperature [F] 39 39 39 Nominal SET [F] 12 12 12 Nominal SCT [F] 98 98 98 Nominal Discharge Air Temperature (DAT) [F] 27 27 27 Nominal Compressor Sizing [Btu/h] 2,300 2,400 2,400 Solid Wall Area (including the door for Class B Machines) [ft 2 ] 45 56 62 Glass Area [ft 2 ] 0 0 0 Baseline Air Infiltration [lb/hour] 9 14 17 Load from Electronic components (bill changers, LED displays, etc.) [kWh] 0.2 0.2 0.2

5-195.4.5 Non-Numerical Assumptions

In developing the energy consumption m odel, DOE made certain non-numerical assumptions concerning the analysis. These includ e general assumptions a bout the analysis as well as specific assumptions about load components and design options.

DOE assumed that all conditi ons are based on new equipmen t tested in a controlledenvironment chamber and subjected to the me thods of testing and rating in ANSI/ASHRAE Standard 32.1–2004. Manufacturers that certify th eir equipment to comply with Federal standards will be required to test new units using this method, which specifies ambient temperature, humidity, light le vel, and other requirements.

DOE did not consider variable-speed co mpressors as a compressor design option. Variable-speed compressors reduce energy c onsumption under real-world conditions by matching their capacity to the refrigeration load , which can change due to variation in ambient conditions and product loading. This eliminates the inefficiencies that occur due to mismatched capacity and load in a single-speed compre ssor during part-load ope ration. The ANSI/ASHRAE Standard 32.1-2004 test procedure prescribes st eady-state conditions. Thus, a variable-speed compressor would be limited to single-speed oper ation and the resulting EER would be no better than that of a properly sized single-speed compressor. Similarly, under ANSI/ASHRAE 32.1– 2004, the performance of a high-efficiency variable -speed compressor would be comparable to a high-efficiency single-speed compressor.

Because baseline models must meet ENERGY STAR Tier 1 criteria, DOE assumed that Class B machines meet the Tier 1 criteria wh en tested at the ANSI/ASHRAE Standard 32.1-2004 required 90°F test condition, and Cl ass A machines meet the Tier 1 criteria when tested at the ASHRAE Standard 32.1-2004 required 75°F test condition.

5.4.6 Numerical Constants and Assumptions

In developing the energy consumption m odel, DOE identified constants and m ade assumptions concerning numerical values used in the analysis. These include ambient conditions, financial assumptions, and parameters necessary to calculate the component and non-electric loads. Details of these assumptions are shown in Table 5.4.17 and Table 5.4.18 below.

5-20Table 5.4.17 Energy Consumption Model Numerical Constants and Assumptions Numerical Constants and Assumptions Value Source Test Chamber Temperature [°F] 75 or 90 ASHRAE Standard 32.1-2004 Test Chamber Relative Humidity [%] 45 or 65 ASHRAE Standard 32.1-2004 Test Chamber Pressure [pounds per square in (psi), absolute] 14.7 Assumed List Price Markup [$/$] 2.00 Assumed Lighting Operating Time Per Day [hr] 24 Assumed based upon ASHRAE Standard 32.1- 2004

Evaporator Fan(s) Run Time Per Day [hr] 24 or less, Less than 24 hours if the evaporator fan motor control option is selected, based on discussions with manufacturers Off-cycle defrost time per day if Evaporator Fan Control is Enabled [hr] 1.5 Assumed

R Value of Foam Insulation [ft2F·h/Btu·in] 8 Discussions with foam manufacturers; manufacturer data sheets R Value of Aerogel Insulation [ft2·°F·h/Btu·in] 10 Discussions with aerogel manufacturers

Convective Film Coeffi cient Inside Case Walls With Evap Fan On [Btu/h-ft 2 -F] 4.00 Communication with RTTC

Convective Film Coeffi cient Inside Case Walls With Evap Fan Off[Btu/h-ft 2 -F] 1.00 ASHRAE Handbook–Fundamentals 2005

Convective Film Coeffi cient Outside Case Walls [Btu/h-ft 2 -F] 1.46 Communication with RTTC Evaporator Coil Overall Bypass Factor [%] 17 DOE estimate Density of Air @ Test Temperature [lb/ft 3 ] 0.073 or 0.071 ASHRAE Handbook–Fundamentals 2005 High-Efficiency Compressor Cost Premium 6% Interviews with compressor manufacturers High-Efficiency Compressor Power Reduction 3% Interviews with compressor manufacturers

Electricity Cost [$/kWh] 0.08 Commercial Building Energy Consumption Survey (CBECS), Energy Information Administration (EIA), average commercial price in 2004

Table 5.4.18 Engineering Constants

Numerical Constants and Assumptions Number Source Specific Heat of Air @ Test Conditions [Btu/lb-R] 0.24 Thermodynamics by Cengel and Boles, 4th edition, 2002 Latent Heat of Vaporization of Water/Water Vapor @ Test Temp [Btu/lb] 1050 or 1044 Thermodynamics by Cengel and Boles, 4th edition, 2002 Latent Heat of Fusion of Water/Ice [Btu/lb] 143.5 ASHRAE Handbook–Fundamentals 2005
Conversion from Watts to Btu/h [Btu/h-W] 3.415179 ASHRAE Handbook–Fundamentals 2005

5.4.7 Model Components

Figure 5.4.1 shows the components of the en ergy consumption m odel. The model calculates DEC in two major subsections: component energy consumption and compressor energy consumption. Component energy consumption is the sum of electri cal energy directly

5-21consumed by each fan motor and lamp. Com presso r energy consumption is calculated from the total heat load (expr essed as Btu/h).

The total heat load is the sum of the component load and the non-electric load. The component load is a sum of the heat emitted by evaporator fan motors and lighting inside the refrigerated space. (Condenser fan motors are outside the refrigerated space and do not contribute to the component heat lo ad.) The non-electric load is the sum of the heat contributed by radiation through glass (for Cl ass A machines), heat conducted through walls and doors, and warm air infiltration.

Figure 5.4.1 Components of the Energy Consumption Model Total Heat

Load [Btu/h]

Component

Load [Btu/h] Non-Electric Load [Btu/h]

Fan Motor Heat Load

[Btu/h] Lighting Heat Load [Btu/h] Radiation Load [Btu/h] Conduction Load [Btu/h] Infiltration Load [Btu/h] Daily Energy Consumption [kWh/day]

Compressor

Energy Consumption

[kWh/day]
Compressor Model (ARI 540)

Electric Energy Consumption

[kWh/day]

Heat Load

[Btu/h] Legend: Component

Energy Consumption

[kWh/day]

Fan Motor

Energy Consumption

[kWh/day] Lighting Energy Consumption

[kWh/day]

5.4.7.1 Component Energy Consumption

Component energy consum ption is the sum of electrical energy directly consumed by each fan motor and light fixture.

Fan mot or energy consumption is calculat ed by summing the power draw of each evaporator and condenser fan motor, and multip lying the total motor pow er by the total running time over 24 hours. This analysis assumed condens er fans only run when the compressor is on. The evaporator fan is assumed to run 24 hours a day, unless the evaporator fan motor control

5-22option is selected. In this case, the evaporator fan motor is off during compressor off-cycle tim es except for defrost periods.

Lighting energy consumption is calculated by summing the power draw of each fixture and ballast, and multiplying the total by the tota l operating time of the lighting system over a 24- hour period.

5.4.7.2 Compressor Energy Consumption

DOE calculated comp ressor energy consumption (CEC) using the compressor model described in section 6.4 of Ai r-Conditioning and Refrigeration Institute (ARI) Standard 540- 2004, Performance Rating of Positive Displacem ent Refrigerant Compressors and Compressor Units . This model is based on a 10-coefficient po lynomial derived from empirical compressor performance data for power, mass flow, current, a nd efficiency. The coeffi cients are derived for each of these parameters as a function of SET and SCT. Compressor coe fficients, or tabulated empirical data (from which coefficients can be derived), are available from compressor manufacturers. Similar to the method used for remote condensing equipment, the EER of any compressor can be determined given the SET and SCT.

5.4.7.3 Component Load Model

The component load is the sum of the heat emitted by each evaporator fan motor and lamps inside the refrigerated volume. This wast e heat must be removed by the compressor.

DOE assu med that all electrica l energy consumed by the evaporator fan motors ends up as heat inside the refrigerated space. In any elect ric motor, irreversibilities in the motor windings, bearings, and other mechanical components convert much of the input electrical energy into heat. The rest of the energy is convert ed to moving air insi de the case. This moving air is slowed by friction and eventually conve rted to heat as well.

DOE assumed that all electri cal energy consumed by lighting components inside the refrigerated space ends up as h eat inside that space. In the ANOPR, DOE assumed that none of the electrical energy consumed by lighting component s outside the refrigerated space ends up as heat inside that space. For the NOPR, DOE is modifying this assumption for Class B machines by attributing a fraction of the electrical energy consumed by lighting components outside the refrigerated space to added heat inside that space. DOE believes that, even though the lighting components are not inside the refrigerated vo lume, they are contained within the machine envelope and contribute some heat through condu ction to the refrigerated space. (Note that having ballasts inside the refrigerated space is not typical of current beverage vending machine designs, but DOE wished to consider the possibility in the model.)

5.4.7.4 Radiation Load Model

The radiation heat lo ad model accounts fo r the gray-body radiation between the warm surfaces of the surrounding environment (the test chamber) and the cold inner surfaces of the refrigerated space through the glass doors of Cla ss A machines. The net radiation is incorporated into the overall U-value of the door calculated by WINDOW 5.2 (see Table 5.4.9 above for the

5-23U-values calculated). Within the W INDOW 5.2 pr ogram, the environmental conditions in the refrigerated volume and the test chamber were sp ecified to match the two test conditions defined in ASHRAE Standard 32.1-2004. See section 5.4.7.5 below for a discussion of the calculation of the comb ined radiation and conduction lo ads for glass doors and other glass.

5.4.7.5 Conduction Load Model

The conduction load model accoun ts for the heat conducted through walls and doors. For solid walls and doors, the conduction load is given by:

Q A T T

h d
k h cond walls room case

o ins

ins i  

  1 1



# 

 Eq. 5.1

where

A walls is the area of the exterior of the refrigerated volume (ft 2 ), h o is the convective film coefficient on the out side of refrigerated volume walls (Btu/h-ft 2 -°F), h i is the convective film coefficient on the inside of refrigerated walls (Btu/h-ft 2 -°F), d ins is the insulation thickness (in), and k ins is the insulation thermal conductivity (Btu-in/h-ft 2 -°F).

Because of its high thermal conductivity, the sh eet metal that encloses the insulation does not have any significant effect on the conduction load, and ther efore was not included in the calculation of conduction load. See Table 5.4.17 above for numerical cons tants pertaining to the conduction model.

For glas s doors, the conduction lo ad is inco rporated into the overall U-factor of the door assembly or glass calculated by WINDOW 5.2 (see Table 5.4.9 above for the U-values calculated). The comb ined radiation and conduc tion load for glass doors and other glass is calculated as:

Eq. 5.2 

#  Q U AT T

glass overall glass room case 

where

U

overall is the overall U-factor, includi ng convection and radiation (Btu/h-ft 2 -°F), and A glass is the area of the glass (ft 2 ).

5.4.7.6 Infiltration Load Model

The infiltration load m odel accounts for the he at that is added to a display case when warm, moist air enters the case (p rimarily through leaks and vend doors). The infiltration load is difficult to model because of the inherent comp lexity of the fluid phe nomena of infiltration. Therefore, DOE used empirical da ta for defrost melt water to back-calculate the infiltration load.

5-24DOE calibrated this approach using input from manufacturers and empirical data for infiltration loads provided by Southern California Edison’s RTTC from beverage ve nding machine testing.

Ambient room air infiltrated into the refrig erated space contributes to the load in two ways: a sensible load in the form of the heat c ontained in the dry air, a nd a latent load in the form of water vapor in the ai r that condenses on cold surf aces. Assuming the amount of condensation on the coil—and thus the amount of defrost melt water—is correlated to the amount of water that enters the case through inf iltration, the defrost melt water mass flow can be used to estimate the mass flow of water that ente rs the case as water vapor in the air. Given the values both for the humidity level in the case and the ambient room air, the mass flow of air that enters the refrigerated ca se can be calculated as:



#     m HR HR CBF

air defrostmelt

room case 

  1 m



#   Eq. 5.3

where

m air is the mass flow of dry air into the case (lbs/hr),

m defrostmelt is the mass flow of defrost melt water (lbs/hr), HR room is the humidity ratio of the ambien t air in the room (dimensionless), HR case is the humidity ratio of the air in side the case (dimensionless), and CBF is the coil bypass factor (dimensionless).

The coil bypass factor is a measure of the fraction of air in the case that is never influenced by the evaporator coil (or a measure of the fraction of air that does not deposit its moisture onto the evaporator coil). This factor allows the infiltration calculation to be correlated to empirical data. Communication with Southern California Edison’s RTTC was used to estimate the evaporator coil bypass factor. As shown in Table 5.4.17 above, the coil bypass factor was estimated to be 17 percent.

Once the air flow rates were calculated, they were entered into DOE’s model. The mass flow of water vapor into the case is the mass flow of air multiplied by the difference of humidity ratios inside and outside the case. Using the ma ss flows of air and water vapor, the infiltration load can be approximated using:

Eq. 5.4 Q mC T T m H air dryair room case vapor v H O inf
,    2

where

Q inf is the infiltration load (Btu/h), C

air

is the specific heat of dry air (Btu/lb-°F),

m vapor is the mass flow of water vapo r into the case (lbs/hr), and Hv ,H2O is the heat of vaporization of water.

5.5 COST-EFFICIENCY CURVES

5-25The result of the engineering analysis is a set of cost-efficiency curves. DO E developed six curves representing the two equipment classe s and three different size machines in each equipment class using the baseline specifica tions and design options described above. The method for developing curves started with determ ining the baseline energy consumption (chosen to be ENERGY STAR Tier 1) and manufacturer production cost . Above the baseline, design options were implemented in order of lowest to highest payback, and only one design option was implemented at each design option level. Design options were implemented until all technologies were at a maximum level.

The six cost-efficiency curves are shown in Figure 5.5.1 through Figure 5.5.6 below and in tabular f orm in Table 5.5.1 through Table 5.5.6 below in the form of DEC versus MSP. More detailed results, in cluding the design options used at each design option level, are provided in appendix B. The cost-efficiency curves were ca lculated at the 75°F te st condition of ASHRAE Standard 32.1-2004.

As stated above, DOE used the cost-efficiency curves from the engineering analysis as an input to the life-cycle cost (LCC) analysis to determine the price of be verage vending machines to the customer (see chapter 8 of the TSD).

5-26$1,000 $1,500 $2,000 $2,500 $3,000 $3,500

0.0 2.0 4.0 6.0 8.0 10.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.1 Cost-Efficiency Curves for the Small-Size Class A Equipment Class

Table 5.5.1 Cost-Efficiency Data for the Small-Size Class A Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 6.10 $1,856.20 2 5.73 $1,868.92 3 5.57 $1,876.79 4 5.47 $1,881.93 5 5.27 $1,893.33 6 3.95 $2,003.03
7 3.73 $2,027.85 8 3.63 $2,043.67 9 3.58 $2,055.07 10 3.33 $2,204.35 11 3.25 $2,971.76

5-27$1,000 $1,500 $2,000 $2,500 $3,000 $3,500 $4,000

0.0 2.0 4.0 6.0 8.0 10.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.2 Cost-Efficiency Curve for the Medium-Size Class A Equipment Class

Table 5.5.2 Cost-Efficiency Data for the Medium-Size Class A Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 6.53 $2,222.07 2 5.97 $2,243.64 3 5.81 $2,251.52 4 5.70 $2,257.59 5 5.51 $2,268.99 6 4.19 $2,378.69
7 3.95 $2,408.68 8 3.83 $2,427.84 9 3.79 $2,439.23 10 3.52 $2,602.29 11 3.43 $3,456.21

5-28$1,000 $1,500 $2,000 $2,500 $3,000 $3,500 $4,000

0.0 2.0 4.0 6.0 8.0 10.0 12.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.3 Cost-Efficiency Curves for the Large-Size Class A Equipment Class

Table 5.5.3 Cost-Efficiency Data for the Large-Size Class A Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 6.75 $2,426.95 2 6.62 $2,433.02 3 6.46 $2,440.90 4 6.21 $2,453.62 5 4.89 $2,563.32 6 4.60 $2,593.31
7 4.46 $2,613.58 8 4.41 $2,624.98 9 4.05 $2,840.85 10 3.94 $3,846.11

5-29$1,000 $1,500 $2,000 $2,500 $3,000 $3,500

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.4 Cost-Efficiency Curve for th e Small-Size Class B Equipment Class

Table 5.5.4 Cost-Efficiency Data for the Small-Size Class B Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 4.96 $1,521.33 2 4.62 $1,544.13 3 4.51 $1,557.72 4 4.31 $1,591.67 5 4.28 $1,603.07 6 3.78 $2,023.72 7 3.69 $2,909.47

5-30$1,000 $1,500 $2,000 $2,500 $3,000 $3,500

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.5 Cost-Efficiency Curve for the Medium-Size Class B Equipment Class

Table 5.5.5 Cost-Efficiency Data for the Medium-Size Class B Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 5.56 $1,716.84 2 5.20 $1,739.63 3 5.12 $1,744.77 4 4.99 $1,760.59 5 4.76 $1,796.01 6 4.72 $1,807.41
7 4.22 $2,228.06 8 4.12 $3,247.02

5-315-32 $1,000 $1,500 $2,000 $2,500 $3,000 $3,500 $4,000

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 Daily Energy Consumption [kWh/day]Manufacturer Selling Price [$]

Figure 5.5.6 Cost-Efficiency Curve for th e Large-Size Class B Equipment Class

Table 5.5.6 Cost-Efficiency Data for the Large-Size Class B Equipment Class

Efficiency

Level Daily Energy Consumption

[kWh/day] Manufacturer Selling Price [$]

1 5.85 $1,779.80 2 5.48 $1,802.60 3 5.33 $1,819.53 4 5.07 $1,854.95 5 5.03 $1,866.35 6 4.52 $2,287.00
7 4.41 $3,439.97

5.6 RESULTS

DOE presents more detailed results and suppor ting data for the engi neering analysis in appendix B of this TSD.** DRAFT **

REFERENCES

1 American Metals Market, http://www.amm.com/.

2 U.S. Department of Labor, Bureau of Labor Statistics, Producer Price Indices
, http://www.bls.gov/ppi/.

3 U.S. Department of Commer ce, Bureau Economic Analysis, Gross Domestic Product Implicit Price Deflator , https://bea.gov/b ea/dn/nipaweb/TableView.asp#Mid.

4 Environmental Protection Agency and U. S. Department of Energy’s ENERGY STAR program, http://www.energystar.gov.

5 Arthur D. Little, Energy Savings Potential for Co mmercial Refrigeration Equipment
, June 1996.

6 Southern California Edison, Next Generation Vending Machine, 2006 ACEEE Summer Study on Energy Efficiency in Buildings.

7 Lawrence Berkley National Laboratory, Window 5.0 , available at http://windows.lbl.gov/software/window/window.html.

8 American National Standards Institute/Ameri can Society of Heati ng, Refrigeration and Air-conditioning Engineers, 2004. Standard 32.1-2004: Methods of Testing for Rating Vending Machine for Bottled, Canne d, and Other Sealed Beverages

.

5-33