# #23.4

Magnetrons and power supplies have some efficiency potential. n Improved magnetron efficiency • All magnetrons within the test sample for which DOE was able to obtain specifications had a conversion efficiency between 71 and 72 percent. • One supplier has announced a magnetron with a stated efficiency of 75 percent, allegedly capable of saving 45.4kWh over a 5.4 year life of an MWO vs. a 71-percent magnetron. n Improved magnetron power supply efficiency • Standard magnetron power supplies utilize a simple, heavy, microwave oven transformer (MOT), along with a high-voltage capacitor, and 1 or 2 high-voltage diode(s). Few cost-effective improvement opportunities appear to remain. • Inverter-based power supplies rectify input power and then create frequencies and voltages of choice with an Insulated Gate Bipolar Transistor (IGBT). A much smaller transformer then produces the filament voltages. Inverter power supplies allegedly have 2 

### percent higher efficiency than standard magnetron power supplies. nControl board power supply efficiency • Could potentially be made more efficient with more modern power supply designs. • Triacs and other solid state switching gear could reduce power supply requirements. • But can these technologies operate reliably within a microwave oven environment? • Lastly, displays and cooking sensors consume more power than control board. 153

# #23.4

Cost-efficiency analysis from updated 1996 TSD is confirmed.

• DOE estimates a standard MOT can be improved from about 93% to 96% -- about 3%; inverter power supplies offer 2% efficiency increase. 1: Baseline + More Power supplies i Cost estimates for MOTs indicate comparable costs as for the updated Efficient can mprove

MWO efficiency 1996 TSD; inverter power supplies are expected to be more costly. Power Supply by 2.9%. • Control board power supplies contribute minimally to overall efficiency, and there is a question of applicability of high efficiency designs. 2: Level 1 + Improved fans All MWOs studied utilized comparable fans and fan motors. More Efficient Fan increase MWO

efficiency 0.23% The small power consumption of these components offers limited opportunity for overall efficiency impact. • Magnetron Magnetrons studied for which data is available had efficiencies efficiencies ranging from 71 - 72% ranged from 70 - 3: Level 2 + 73% Only one proprietary approach identified to achieve higher efficiency More Efficient (75%), so this level cannot be considered. Magnetron Improved

magnetron efficiency Since most magnetrons are manufactured in-house , no data is increases MWO available to suggest a different cost than the updated 1996 analysis. efficiency 0.9% • No MWOs studied contained reflective surfaces 4: Level 3 + Reflective r Reflective Surfaces m rove MWO c No data is available to determine a different cost and efficiency eff iency 0.50% improvement than the updated 1996 analysis. 154

## 1 

## Cost-Efficiency Validation Test Procedure Evaluation
4 

## Standby Power Conclusions 

# #23.4

155

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Cooking Efficiency Test Procedure Comparison n Fundamentally, the two test procedures are very similar: • Cool water outside test vessel to 10°C below room temperature, then pour/weigh 1 kg into the test vessel. ' Cooking efficiency test is run at 100 percent of MWO output. 

### • Heat water sample to room temperature and record time and input power during heating. n Current DOE Efficiency Test (IEC 705-1988 and Amendment 2-1993) • Excludes filament heating power requirements • Has tighter ambient temperature requirements (+/- 2°C vs. +/- 5°C) • Has tighter final temperature requirements (Tambient +/- VC vs. 20 +/- 2°C) 

### n Current IEC Test Procedure (IEC 60705-2006) • Test supplanted IEC705; IEC considers IEC705 obsolete. • Energy consumption measurement includes filament heat-up time, which lowers efficiency by 1-2 percent. • Requires rounding output power to nearest 50W and efficiency to the nearest whole number, which more than triples the range of efficiency and power output calculations compared to IEC705. • Test procedure does not specify how to determine the filament heat-up time, which creates uncertainty in the power output calculations. • Test procedure does not specify the requirements for accuracy of temperature and time measurements. 156

# #23.4

Based on limited testing, the data from IEC705 -1988 and Amendment 2 - 1993 is more consistent. nThree tests per MWO , 12 MWOs tested n Rounding of output power per IEC60705 roughly quadruples test -to-test variability.
Test to Test Efficiency Range (%) Test Unit Rated Power IEC 705- Rounded Raw IEC

output(W) 1988 IEC 60705 60705 DOE 1 700 1.46 3.57 0.56 DOE 6 800 0.06 3.45 0.96 DOE 5 800 0.4 3.33 0.70 DOES 900 0.48 5.00 1.66 DO E22 1,100 0.71 3.57 0.50 DOE19 1,100 0.47 3.45 0.20 DOE15 1,100 0.77 3.39 0.53 DOE21 1,100 0.21 1.67 0.76 D O E2 7 1,200 1.07 1.67 1.05 DOE29 1,200 0.92 0.00 0.87 DOE30 1,250 0.67 1.79 0.82 DOE32 1,300 1.24 5.17 2.14 1 6 5 ®IEC 60705 Non-Rounded Test-to-Test Results Range ®IEC 60705 Rounded Test-to-Test Results Range

9 22 19 15 21 27 29 30 32

DOE Test Unit #
157

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DOE methodology for IEC 705 improves test accuracy.

AHAM Data 63
62
61
60

59 58 -}
57
56
55
54 650 750 850 950 1,050 1,150 1,250 Measured Output Power (W) 63 62 -
61
60 59 58 -1
57
56 d 55 d 

## DOE Data

12 f



# 1* I P®

54 600 700 800 900 1,000 1,100 1,200 Measured Output (W) 

### 1'l

158

## 1 2 Cost-Efficiency Validation Test Procedure Evaluation Standby Power 

## Conclusions 

# #23.4

159

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DOE and AHAM standby power measurements are similar. nAverage standby power ranged from 1W to 5.75W (9 to 46kWh per year). nControl boards had very similar topologies. • All used unregulated followed by regulated power supplies. n Displays appear to be a primary driver for higher standby power consumption. • MWOs equipped with Vacuum-Fluorescent Displays (VFDs) and cooking sensors tend to use the most power (up to 5.5W). • Large, sophisticated Liquid Crystal Displays (LCDs) with backlighting and cooking sensors consume 2-4 W. • Light Emitting Diodes (LEDs) and non-backlit LCDs consume the least standby power. n Cooking sensors may also impose a significant constant standby power load. • The actual load depends on the cooking sensor technology, and ranges from 1-2.5W. • However, separating effects of cooking sensors from other factors can be difficult. 

### n Controllers and their power supplies could potentially be more efficient. • Even MWOs with non-backlit LCDs consume more than 1W in standby mode.

160

# Standby power depends on multiple factors:

n Display technology, size and sophistication , brightness and contrast nCooking sensors and inverter systems also influence results.

5.5 5.0 ^ 4.5

1.5 - LED A a VFD ♦ VFD, CS n LCD q LCD, B •LCD, B, CS OLCD, B, CS, I

A • $ 0 0 0 °D [9 0 8 0• o 1.0 1.5 2.0 2.5 3.0

Display size (in2) Legend: LED = Light Emitting Diode VFD = Vacuum Fluorescent Display LCD = Liquid Crystal Display B = Backlighting CS = Cooking Sensor I = Inverter Drive 

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161

# The DOE and AHAM standby power data correlate well.

6.0 

### n However, the AHAM data only noted the presence of cooking sensors.

5.5 d 5.0 ^

2.0 d 1.5 ^ 1.0650 O

O 750 A

+ 

## s • i
+ + A 0 

# I O 0 850 950 1050 1150 Rated Power Output (W) 7 O

1250 1350 O LED

AVFD AVFD, CS n LCD q LCD, B •LCD, B, CS OLCD, B, CS, I +AHAM -ARAM, CS 

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162

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In DOE tests, LED displays had significant standby power variation due to changes in display time over the course of the test.

2.0 1.8-I

1.0 1
0.8-- 0.5 1.0 1.5 2.0 2.5 Display Size (in2) 163

# Display types and features impact achievable standby

power levels.

Effect of Backlighting

LED, No LCD, No LCD, No LCD, with LCD with Sensor Sensor Sensor, Sensor, Sensor, Backlit Backlit Backlit, Inverter 

# •

VFD, with Sensor 

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164

# #23.4

Further standby power testing observations... n LCD and VFD displays had nearly constant power draws regardless of time diplayed. nSome VFDs could be turned off, but standby power only decreased by 0.1- 0.25W. nStandby power is very sensitive to voltage fluctuations. nCooking sensors are constantly "on". 

# ... and potential improvement opportunities: nCooking sensors that can turn "off" when not in use n Displays that can turn off or dim their illumination • The test procedure credits this. 

### n More efficient power supplies and controllers • Triac/solid state relay control of loads instead of electromechanical relays • Switching power supplies instead of unregulated + regulated power supplies
165

## Cost-Efficiency Validation Test Procedure Evaluation Standby Power Conclusions 

# #23.4

166

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Conclusions n The approach of updating the 1996 TSD cost -efficiency curves has been validated. • The current AHAM data submittal demonstrates a similar range of efficiency as the data in the 1996 TSD. • There is still a lack of correlation between efficiency and either cavity size or output power. • For design options that impact efficiency, the efficiency and cost increments are still valid. 

### n The IEC test method currently referenced by the DOE test procedure should be retained. • IEC 705-1988 and Amendment 2-1993 appears to be a more consistent cooking efficiency testing method than the current IEC 60705-2006. • Improvements which could be specified in the DOE test procedure include: 

### - Increasing the water sample weight to 2kg (better test vessel coating, longer run time) - Requiring the test vessel to be insulated from surfaces and hands outside of the MWO n IEC 62301-2005 could be incorporated by reference to the DOE test procedure to measure standby power, ideally with the following qualifications: • Remove start time ambiguity by requiring MWO clock to be set to 12:00 AM to begin test • Require test be run for 12 hours to capture display variability with time 167

# #23.4

Specific issues for which DOE seeks comment: n The retention of the superseded IEC MWO test method in the DOE test procedure n Suggested amendments to the DOE test procedure to improve efficiency 

### measurements n Any data or studies of cooking sensors and their effect on energy efficiency and 

### annual energy consumption n The consumer utility of an inverter -based magnetron power supply and efficiency data regarding standard MOT versus inverter power supplies W n Any comparative studies regarding unit-to -unit cooking efficiencies; i.e. cooking

efficiency tests that note the efficiency variability among large samples of MWOs due to random component effects n Data or studies regarding the cooking efficiency of magnetrons when run at different output levels n Cost data for different display types and components affecting standby power n The potential amendments to the DOE test procedure to incorporate an MWO c standby power metric as outlined previously 

### cis a n The consumer utility of the various display technologies discussed P 

### n Data on whether cooking sensors exist that do not req r7 we 8

# #23.4

Energy Conservation Standards for Residential Dishwashers , Dehumidifiers , Cooking Products and

Commercial Clothes Washers ANOPR Public Meeting 

# Closing Building Technologies Program Office of Energy Efficiency and Renewable Energy

U.S. Department of Energy December 13, 2007

# #23.4

The Energy Policy and Conservation Act (EPCA) directs DOE to consider seven factors when setting energy conservation standards 'nalysis 1. Economic impact on consumers and Life-cycle cost analysis manufacturers Manufacturer impacts analysis 2. Lifetime operating cost savings Life-cycle cost analysis 3. Total projected energy savings National impact analysis 4. Impact on utility or performance Screening analysis 

### Engineering analysis 5. Impact of any lessening of Manufacturer impacts analysis competition 6. Need for national energy National impact analysis 

### conservation 7. Other factors the Secretary Environmental assessment considers relevant Utility impact analysis Employment impact analysis 170

# #23.4
How to Submit Comments... n Public Meeting - oral comments will be captured in the transcript and become part of the public record. n Written comments - ANOPR comment period open until January 29, 2008 Reference docket #: EE-2006-STD-0127 and/or RIN #: 1904-AB49 Email: appliance. rulemakincL(c_ee.doe.gov Mail: Ms. Brenda Edwards-Jones

U.S. Department of Energy Building Technologies Program, Mail stop EE-2J ANOPR for Residential Dishwashers, Dehumidifiers, Cooking Products and Commercial Clothes Washers EE-2006-STD-0127 1000 Independence Avenue, SW Washington DC, 20585-0121 Courier: Ms. Brenda Edwards-Jones

U.S. Department of Energy Building Technologies Program, 1J-018 1000 Independence Avenue, SW Washington DC, 20585-0121 171