#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.

n Control 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

EE-2006-STD-0127 COMMENT 23.4
#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

EE-2006-STD-0127 COMMENT 23.4
1 Cost-Efficiency Validation

Test Procedure Evaluation

4

Standby Power

Conclusions

#23.4

155

EE-2006-STD-0127 COMMENT 23.4
#23.4

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

EE-2006-STD-0127 COMMENT 23.4
#23.4

Based on limited testing, the data from IEC705 -1988 and

Amendment 2 - 1993 is more consistent.

n Three 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

EE-2006-STD-0127 COMMENT 23.4
#23.4

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

EE-2006-STD-0127 COMMENT 23.4
1

2

Cost-Efficiency Validation

Test Procedure Evaluation

Standby Power

Conclusions

#23.4

159

EE-2006-STD-0127 COMMENT 23.4
#23.4

DOE and AHAM standby power measurements are similar.

nAverage standby power ranged from 1W to 5.75W (9 to 46kWh per year).

n Control 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

EE-2006-STD-0127 COMMENT 23.4
Standby power depends on multiple factors:

n Display technology, size and sophistication , brightness and contrast

n Cooking 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

#23.4

161

EE-2006-STD-0127 COMMENT 23.4
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 ^

1.0

650

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

#23.4

162

EE-2006-STD-0127 COMMENT 23.4
#23.4

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

EE-2006-STD-0127 COMMENT 23.4
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

#23.4

164

EE-2006-STD-0127 COMMENT 23.4
#23.4

Further standby power testing observations...

n LCD and VFD displays had nearly constant power draws regardless of time

diplayed.

n Some VFDs could be turned off, but standby power only decreased by 0.1-

0.25W.

n Standby power is very sensitive to voltage fluctuations.

n Cooking sensors are constantly "on".

... and potential improvement opportunities:

n Cooking 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

EE-2006-STD-0127 COMMENT 23.4
Cost-Efficiency Validation

Test Procedure Evaluation

Standby Power

Conclusions

#23.4

166

EE-2006-STD-0127 COMMENT 23.4
#23.4

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

EE-2006-STD-0127 COMMENT 23.4
#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

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

EE-2006-STD-0127 COMMENT 23.4
#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

EE-2006-STD-0127 COMMENT 23.4
#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

EE-2006-STD-0127 COMMENT 23.4
#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

EE-2006-STD-0127 COMMENT 23.4