6. 3 7C 3.

NBSIR 81-2309

Arr Evaluation of Assigning Credit/Debit

to the Energy Factor of Clothes Washers

Based on Water Extraction Performance

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Consumer Product Technology

Washington, D.C. 20234

August 1981

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

NBSIR 81-2309

AIM EVALUATION OF ASSIGNING CREDIT/DEBIT

TO THE ENERGY FACTOR OF CLOTHES WASHERS

BASED ON WATER EXTRACTION PERFORMANCE

C. Denver Lovett

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Consumer Product Technology

Washington, D.C. 20234

August 1981

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

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Table of Contents

Page

I. Introduction , 1 A. Objective . . f 1 B. Background ,

. . < 1 C. Energy Savings 2

D. National Significance of Reducing Moisture Retention , , . , 2

II. Parameters Affecting Moisture Retention . . , f . , , 3

A. Effects of Spin Time 3

B. The Effect of Spin Speed and Load Type 3

C. Cold Water Rinse . . .

. , , . 4

III. Limitations 4

A. Vibrations . ..... 5 B. Wrinkle Performance ...... t ............ , 5 C. Cost Analysis ................ 6

IV. Energy Factor Credit/Debit Analysis . . .... 7 A. Meed for Credit/Debit . « . , 7 B. First Approach to Credit/Debit ............... 7

C. Second Approach to Credit/Debit .............. 8

D. Energy Factor as Affected by Credit/Debit ......... 8

V. Conclusions 10

References 11
/
List of Figures

Page

Figure 1 A Diagrammatic Illustration of Moisture Transfer Between

Clothes Washer and Clothes Dryer 12

Figure 2 Incremental Dryer Efficiency Versus Moisture Retention 13

Figure 3 Water Retention Versus Test Load Weight for Clothes

Washers A, E, fl 14

Figure 4 Clothes Dryer Energy Consumption for Drying Test Loads Spun In

Two Clothes Washers 15

Figure 5 Moisture Retention Versus Spin-Time for Three Clothes Washers. . 16

Figure 6 Clothes Washer H Moisutre Retention Versus Tub Spin Speed ... 17

Figure 7 Clothes Dryer Energy Consumption Versus Initial Moisture

Retention 18

Figure 8 Change in Moisture Retention Rate Versus Spin Speed 19

Figure 9 Evaluation of Wrinkle Hypothesis by Six Judges 20

Figure 10 ‘Credits/Debits to Influence The Energy Efficiency Factors of

Clothes Washers 21

Figure 11 Credits and Debits to Influence The Energy Efficiency Factors

of Clothes Washers 22

Figure 12 Clothes Washer Energy Factor, As Effected by Credits and Debits

for Reduction in Moisture Retention 23

List of Tables

| TABLE 1. Clothes Dryer Incremental Energy Efficiency and Amount of

Water Removed During Each 5 Minute Interval 24

| TABLE 2. Water Retention for Various Clothes Washers with 6 Pound

Test Load 25

TABLE 3. Potential Dryer Energy Savings for Various Moisture Retentions

in a Seven Pound Test Load 26

TABLE 4. Potential Dollar Energy Savings for Various Holding Periods . . 27

, TABLE 5. Machine Capacity and Energy Consumption Data 28

j

1 TABLE 6. Debit/Credit from Figure 11 29

I

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Page

TABLE 7 Energy Factor and Energy Factor Change as a Function of Water

Retention for Two Washers, Using Proposed Credit/Debit Plan 30

APPENDIX A 31
Abstract

To reduce the moisture retention of a clothes load from 65% to 40%, a clothes

dryer uses about 200 times more energy than a clothes washer. Therefore, improving

the clothes washer's water extraction performance can significantly reduce

energy-use of a dryer. For example, a clothes dryer uses about 40% less energy,

when the clothes washer extracts 38% more water from the clothes load. Based on

clothes washer extraction performance, NBS has developed, for the Department of

Energy (DOE), a procedure for assigning credit/debit to the energy factor of a clothes washer. The purpose of this procedure is to provide an incentative for

clothes wash er manufacturers to improve the water extraction performance of washers

Using this procedure, the energy factors for two clothes washers improves by 44%

and 28% respecti vely. This energy factor improvement corresponds to improved water

extraction which reduces the moisture retention of the clothes load from 65% to 40%

One case study shows that dryer energy savings, resulting from reduced moisture

content, justi f ies £$50 incremental cost for improved water extraction performance

for clothes washers.
S' }
I. Introduction

| A. Objective

An integrated approach to appliance energy consumption involves determining

what effect the energy consumption and the performance attributes of one

appliance has on the energy consumption and performance of another appliance.

| Of particular interest in this case is the performance of a clothes washer

j during water extraction (i.e. f spin cycle) and the effect on the clothes dryer

energy consumption. The more water that remains in the clothes load after the

spin cycle, the more energy that must he expended in the drying process. The

ma.ior emphasis of this study is to devise a plan for assigning credits/debits to

the clothes washer for the energy effect on the clothes dryer. This study will

examine the energy cost trade-offs of extracting practical amounts of water

during the spin cycle versus removing excess water by means of thermal energy in

the clothes dryer. In addition, other performance related attributes that may

be adversely affected by increased water extraction using the spin method are

identified.

3. Background

The cost for water extraction by mechanical energy in the clothes washer is

small in comparision with the cost of supplying thermal energy to the clothes

load during the drying cycle in a dryer. Figure 1 shews the moisture transfer

between a washer, a dryer, and the environment , and the corresponding amounts of

energy required for extracting water in the clothes washer and the clothes

dryer. For example, an average value for the machine electrical energy during a

full wash cycle including the spin cycle is about 0.25 kilowatt-hour. If one

assumes that 20^ of the total, machine's electrical energy is used during the

spin cycle, this would amount to only 50 watt-heurs.

Limited test data indicates that the amount of water removed from a

standard 7 lb test load I’ll* during the spin cycle from the "drip wet"

conditions to the "spin ^ry" condition is 9*5 pounds of water. Therefore, the

water extraction during the spin cycle is 190 ihs of water/kWh (- 0.5 lb/. 050

kWh'). This value compares with an average water removal by clothes dryers of

2.07 lbs of water/kWh. This ratio is the average of the incremental dryer ratio

corresponding to moisture retention values between 70^ and 40^ (see Figure 2 and

j Table 1). Therefore, the ratio of water removal during the clothes washer spin

1 cycle to clothes dryer thermal cycle is about 90- Although within certain

ranges of moisture removals, it is 90 times more efficient to extract water

| during the clothes washer spin cycle than during clothes dryer thermal cycle,

there are practical, limitations to the amount of water-, that can be extracted by

means of mechanical energy.

The amount of water removed from a test load -s/aries from clothes washer to

I clothes washer. The test data shown in Table 2 and plotted in Figure 3

Numbers in brackets refer to the references at the end of this repor4-

.

1
indicates that the clothes load moisture retention for different machines varies

from 74# to 50# depending on the temperature of rinse and the weight of clothes

load. For a 7 lb test load this variation in moisture retention amounts to 1 .05

pounds of water (= 0.70 x 7 lbs - 0.55 x 7 lbs''.

If a 7 lb test load spun in a clothes washer resulted in a to# water

retention rather than a 55# moisture retention, the clothes dryer would have to

expend an additional 0.5 kWh (- 1 .05 lbs/2.07 lVkWh'). Therefore, a. clothes

washer resulting- in 55# moisture retention for a 7 lb test load would contribute

significantly in reducing energy required to dry this load. These results are presented to indicate the significant ''variation in the amount of energy reauired

to dry a load when various clothes washers are used to prepare a Toad for the

same clothes dryer.

C. Energy Sa^rlngs

To compare the effect of clothes washer spin performance on the energy

consumption of clothes dryers, it is logical, to select 70# moisture retention

as the baseline case since starting moisture retention for the 7 l.b test load

specified in the clothes dryer test procedure is 70 + 3-5#- Clothes washers

which spin the load to below 70# moisture retention may be considered to achieve

energy savings for the clothes dryer. Conversely, clothes washers which spin

the load to a moisture retention value abo^ 70# may be considered to be wasting

energy in the clothes dryer. Table 3 shows the relationship between moisture

retention and the corresponding computed levels of energy savings for the

clothes dryer. These data indicate, for example, that for a 40# moisture

retention, the possible energy savings in a clothes dryer is 1.0 kWh.

D. National Significance of Reducing Moisture Retention

To establish a base case, assume that all clothes loads have a starting

moisture retention of 65# (weighted average') . If the extraction performance of

clothes washers can be improved such that the weighted average moisture

retention of all clothes loads are 40#. the starting moisture weight of the

clothes load would be reduced by 1.75 lbs (for a 7 lb test load'd A reduction

in wet load weight by 1.75 lbs corresponds to an energy saving for the clothes

dryer of about 0.85 kWh. On a per cycle basis, this 0.85 kWh savings represents

about a 38# savings. It should be noted that this estimated energy savings is

based on an average dryer efficiency of 2.

O'7 lbs of water per kilowatt-hour.

The •'variation in clothes dryer efficiency over certain ranges of moisture

retention is shown in Figure 2. Figure 4 shows the test d ata relating energy

consumption and efficiency of dryer A when the test load is spun to 7C# moisture

retention by washer I and compared to 40# moisture retention when spun in washer

0. On an annual basis, the 0.85 kWh savings per cycle corresponds to an. energy

savings of 354 kWh or a dollar savings of about $20 per year based on 8 cycles

per week and an energy cost of 5*64 ^/kWh. From a national 'dewpoint, the

savings of 354 kWh per dryer would represent a national energy saving of 13 *° x

10- kWh per year (354 kWh/unit x 3q x 10b

units') or about 8 million barrels of

oil equivalent per year.

2
The mechanical energy required to obtain higher water extraction during the

spin cycle is negligible ( about 1^1 in comparison with the potentia.1 thermal

energy savings in the clothes dryer.

II. Parameters Affecting Moisture Retention

The clothes load water retention is affected by:

1. the characteristic of the particular clothes load,

2. the machine operating characteristics, and

3. the rinse water temperature.

The primary characteristics, that affect clothes load water retaining

ability are the weight and composition of the fabric ('cotton, synthetic etc.'1 . For example, a load composed of all cotton fabric tends to retain about twice as much water as a blend of 50$ cotton and 50$ polyester. In general., the percent

water retention decreases with increasing load weight, Figure 3-

The machine parameters which affects moisture retention of the clothes load

are spin speed, spin time, and basket diameter- Only spin speed and spin time

are practical design, options for increasing moisture extraction. Increasing

spin speed offers the greatest potential for improving water extraction.

Increasing spin time is the easiest- design cation to implement, however, it

offers only a modest potential for improving extraction efficiency.

'The temperature of the rinse water that proceeds the final extraction cycle

has a modest ( about 5$'1 effect on the water-retention of the clothes load.

Tests have shown the temperature of the rinse water affects the amount of water

extracted. See Table II. One possibility 'to explain this is that cold water

rinse causes a more viscous water to remain in the clothes load, since co^d

water has a higher surface tension, higher centrifugal forces are required. To

quantify these effects the following test data are presented:

A. Effects of Spin Time

Test results (See Figure 5^ shows that when the spin time of four minutes

is increased by a factor of three, the moisture retention of a standard test

load is reduced by five to ten percentage points- Figure 5 shows the variation

in moisture retention of three clothes washers, A, I, and G-. The moisture

retention of the clothes load spun in machine G- approach 4-0$ after about 12

minutes of spin.

B. The Effect of Spin Speed, and Load Type

Moisture extraction tests were nerformed by using a standard size

household clothes washer which was modified to accept a variable speed drive

motor- This clothes washer had a six minute spin cyc^e, therefore all spin test

were conducted for six minutes. Two types cf test loads were selected to

examine the effects of load composition. One load was a seven-pound standard

3
test load which consisted of a blend fabric of 50?* cotton/50?* polyester and the

other load was a seven pound load which consisted of 100?* cotton fabric.

Figure 6 shows the variation in the posture retention for each test load as the spin speed, was increased from 400 rpm to 900 ran. Each load was

subsequently dried in the same dryer to about 5®* moisture level. Figure 17 shows

the variation in energy use to dry each lead for various va1 ues of initial

moisture retention which corresponds to spin speeds between 400 rpm and °00 rpm.

Figure 7 indicates that for a standard test load the energy used by the dryer

was reduced from 2.42 kWh to 1.28 kWh when the initial moisture retention was

reduced from 77^ respectively to 4CK. This is a 47* reduction in the energy

used hy the dryer.

Figure 6 shows that for the 100* cotton test load, the 400 rpm spin speed

resulted in a 939* moisture retention and the 900 rum spin spee^ resulted in a. 639* moisture retention. These corresponding- retention values can be compared

with 779* and 40?* for the standard test load (with a 50* cotton/500* polyesters )

.

Figure 7, shows that the clothes dryer used 2.96 kWh to dry a 100* cotton load

from a Q3* moisture retention to a 39* final, moisture retention. These results

represent an energy saving of about 28* if tie initial, moisture retention of a

1009* cotton load is 63?* instead of 939*.

Figure 8 is the derivative of the moisture retention ^m»rsus sni.r speed

variation shown in Figure 6. These data show that the water moisture retention

per change in rpm was about 2.5 times greater at 425 rpm than at 375 rpm. At

425 rpm the moisture retention per unit change in rpm was 0.12 nercent per rpm.

Whereas at 875 rpm the moisture retention rate was 0.046 percent per rpm. These

results suggest, as might be expected, that more water is removed at higher spin

speeds and that the more that has been removed, the more difficult it is to

remove the remaining water

.

C. Cold Water Rinse

The effect that cold water rinse has on water extraction was determined

from previous work done at UBS- These test results were presented in a

milestone report titled "The Effect of Water Temperature on Washing Performance"

r2l. Some of these test results are presented in Table 2 and show that the

difference in water retention is typically about five percentage points higher

for cold water rinsing. These data suggest that due to slightly higher initial

moisture retention, an additional small amount of energy is used in the dryer to

remove this additional amount of water *0.35 lbs of water for a standard test

load') corresponding to 5?* higher initial moisture retention. However the energy

saving due to using cold water rinsing as compared with warm water is about 20

times greater than the incremental thermal energy required by the dryer to

remove this additional amount of moisture. .r

III. Limitations

In addition to diminishing returns in terms of the amount of water

extracted for corresponding spin speeds abo^7© a. certain limit, there are

/ 4
additional factors that will limit the spin speed to a specified value,

factors include:

These

i

i

|

| A.

1 . Higher spin speeds pay require pore critical balancing system to

avoid excessive vibration.

2. Higher spin speeds produce larger centrifugal forces which nay cause

no re winkles to remain in the clothes after d lying, and

3* Higher spin speeds nay result in increased cost for drive comnonent

design changes.

Vibrations

During the water extraction test in which the spin speeds were varied fro1'” 400 to QC0 rom, excessive vibration occurred in this clothes washer at 900 rpm.

| Although the vibration which occurred at 900 rpm was objectionable, the moderate

j to slight vibrations that occurred at speeds between 500 rrm to 850 rpm were

acceptable. This qualitative evaluation of machine vibration was based on a

test of the one clothes washer which was modified to accept a variable speed

drive and was conducted on a hard concrete floor. Resonant 'Tibrations for this

1 clothes washer with a test load are not necessarily typical of other clothes

washers and mixed clothes loads. Vibration characteristics are dependent on the

design parameters such as bearing location, weight distribution, and support

stiffness of the particular clothes washer.

B. Wrinkle Performance

Some concern has been expressed that increased spin speeds wou1 d cause more

wrinkles to remain in the clothes. Therefore, tests were conducted to determine

if higher spin speed would cause more wrinkles to remain in the test cloth after

drying.

Two identical permanent press cloth test loads- having- a composition

of 65^ polyester and 35^ cotton were selected. One test load was spun at

400 rpm and the other test load was, spun at 900 rpm. Each test load was

dried sequentially in the same clothes dryer. One group of 12 test cloths

was obtained for evaluation by randomly selecting six test cloths from each

of the dried load- Six participants visually evaluated each of the twelve

test cloths to form two groups - one being more winkled and the other

being less wrinkled.

As shown in Figure 9, sixty percent cf the sorted test cloths confirmed the

I hypothesis that higher spin speeds caused more wrinkles and forty percent

| negated this hypothesis. Three of the test cloths received identical grouping

by all six participants and these identical groups were congruent with the

hypothesis. Each participant expressed difficulty in sorting the twelve test

cloths into two groups of one being more wrinkled than the other. The

conclusion from this test is that, with exception of three test cloths, the

; influence of higher spin speeds on wrinkle performance was only slightly

5
detectable by the six participants. The effects of repeated washings and/or

higher spin speeds were not investigated, nor were actual clothes.

The clothes dryer tends to T'emo -'^ some of the wrinkles that are-, set in. the

clothes during high spin speed water extraction process. Therefore, high spin

speeds are expected to cause sore more wrinkles to remain in the line-dried

clothes as compared with clothes dried in a clothes dryerC. Cost Analysis

Higher water extraction, if done by spinning, ’"ay require a different drive

motor capable of spinning the basket to approximately 800 rpm. Because of

concern for wrinkle performance, some manufacturers may chose to replace current

drive motors with two speed motors. A high speed setting for efficient water

extraction and a lower speed setting recommended for use when wrinkle

performance is of concern. HBS does not have reliable cost estimates for the

various water extraction design options which manufacturers may choose to

implement; however, the incremental, unit costs that are economically justified

by the energy sa-'rings achievable in the clothes dryer can be computed. The

economic feasibility for higher extraction efficiency will be based on the

present value cf the energy savings for various holding periods f 3, 5, 10, 15

years 1

.

Two base cases are presented:

Case 1 is for a change in water retention from 65$ to 40$

Case 1: Retention changes by 25$

Energy savings $20

Discount rate 10$

Holding periods 3,5,10.15 yrs.

Uniform series present value factors 2.48, 3-79, 6.14, 7.60

Average drying efficiency 2.07 lbs of water/kWh

Case 2: is the same as Case 1 except moisture retention is considered to

change from 65$ to 50$. Thus, retention changes by 15$ and the annual energy

savings is £11.60, all other parameters remaining the same.

These data, shown in Table 4, indicate that if the increase in purchase

cost for improved extraction performance (65$ to 40$) is about £50 the annual

energy savings in the clothes dryer will repay fat 10$ discount rate'' this

incremental cost of £50 in about 3 years- However, in Case 2 where the

extraction performance is improved to yield a 15$ reduction in water retention

f65$ to 50$^ it will reauire about 6 years to repay the increase in purchase

cost cf £50. If improved extraction performance can be achieved for about £75,

it will require about 5 years to repqy this increase in purchase cost for Case 1

and 10 years for Case 2. It is questionable whether a payback period as long as

10 years would be generally acceptable. However, since the expected economic

6
life of a clothes washer is about 12 years, it is expected that a 3 to 5 year

payback period would be acceptable.

These two cases give a reasonable indication of the economic feasibility of

increased cost for drive component design changes for a range of achievable

moisture retention an^ acceptable payback periods.

IV. Energy Factor Credit /Debit Analysis

A. Heed for Cred.it/Debit

The intent of the national Energy Policy and Conservation Act is to result

in a program designed to require manufacturers to produce and encourage

consumers to purchase more energy efficient appliances. Assignin'* credits to

clothes washers with superior water extraction performance may provide one

method for manufacturers to improve the efficiency of clothes washers in order

to meet minimum energy efficiency standards. If the credit incentive provided

to the manufacturer is large enough, they may develop innovative ways of

increasing water extraction.

B. First Approach to Credit/Debit

The first approach considered for assigning credits or debits was to

utilize a continuous linear relationship of energy sa^rings with respect to the

percent of moisture retention as summarized in Table 3- A plot of this energy

credit or debit is shown in Figure 10. The effect of any credits or debits is

to change the energy factor by increasing or decreasing the denominator of, the

energy factor. The energy factor specified, in the current test procedure is

defined as useful volume (basket volume') which the clothes can occupy di^n^ed by

the total per cycle energy consumption.

As shown in Table 2, the range of moisture retention for most current

clothes washers is between 74$ and 50*. Therefore, this approach which

prescribes credit or debit according to a continuous linear relationship as shown in Figure 10 would award credit for most existing levels of water

extraction performance without having manufacturers make any design changes to

improve water extraction performance. If no design changes are mabe to enhance

spin performance, the credits assigned to the energy factor will not be

indicative of ary actual dryer energy savings due to a reduced initial moisture

retention. This approach has the following distinct disadvantages:

(1) credits are awarded for existing levels of extraction performance,

(21 such credits would not reflect ary additional energy saved in the

clothes dryer,

(3) awarding credits for existing level of moisture retention, wculf

stifle manufacturers incentive to make design changes to further

improve extraction performance, and
a linear relationship does not impose a very severe penalty for

exceeding the "base moisture content f^O#)

.

C. Second Approach to Credit/Dehit

To c'nercome the disadvantages of the first approach discussed above, it is

proposed that the moisture retention be divided into three ranees. The moisture

values selected for dividing- the spectrum into 3 ranees are 50* and 70* moisture

retention.

1 . No credit nor debit is assigned within the range of 5C# to 70s! moisture retention.

2. Credit is increased linearly with reduction in moisture

retention below 5C#.

3* A constant debit is assigned for moisture retention values

that exceed 7Q#.

The three, ranges for assigning credit and debit are shown in Figure 11 .

A review of available moisture retention data for current clothes washers

show that a few compact clothes washers have moisture retention slightly ^elow

50# which will qualify for a credit. However, some standard clothes washers

have moisture retention just above this value. Being close to this 5C# value or slightly greater than 7C# value pro''rides an. attainable goal which will give

manufacturers the incentive to improve the water extraction efficiency of the

spin cycle. The amount of energy credit or debit is based on the difference in

the pounds of water remaining in the clothes after the spin cycle and the amount

of water corresponding" to a 70# moisture retention (see Tab1 e 3

>! * Figure 11 shows a plot of the amount of energy credit or debit corresponding to 'various

moisture retention levels. The assumption used in determining these

credit/debit values is that each pound of water remaining in the clothes load at

the end of the spin cycle requires about 0.48 kWh of energy consumption in the

clothes dryer to remove the excess water. If a clothes washer spins the clothes

load to QC# moisture retention, an excess of 1 .4 pounds of water remains in the

clothes load as compared with 70# moisture retention- To remove this 1 .4 pounds

of water in the clothes dryer would require about 0.68 kWh. Therefore, a debit

of 0.68 kWh would be given to clothes washers in the form of addition, to the

total per cycle energy consumption, thus reducing the clothes washer energy

factor.

D. Energy Factor as Affected by Credit/Debit

The proposed credit/debit system will only affect the energy factor and not

the annual operating cost. To debit or credit the annual operating cost based

on water extraction performance would mis1 ead the consumer with respect to the

actual operating cost for a representative consumer use cycle. However, if

minimum efficiency standards are set according to the energy factor, the

proposed credit or debit to the energy factor would provide sufficient incentive

to manufacturers to improve the water extraction performance.

8
To apply a credit/debit to the enery factor, the total per cycle enery

consumption would he ad .lusted, hy the kilowatt-hour of credit/debit shown in

Figure 11. To illustrate, let:

= useful capacity, ft5

E^ = total per cycle energy consumption, kWh

R = moisture retention, 4

Prom Figure’ll the energy credit, kWh:

C = 0 for 50 < R < 70

C = 0.68 + 50-R for R < 50

“70“

C = -0.68 for R > 70

The current enery factor, EP, is:

TT

U., EP = and

the ad iusted enery factor would he,

K,

‘ EP =

JATE

fit

( 2 )

where the adjusted total per cycle energy consumption, E^n^,, is:

E

^ATE - C ( 3 )

Therefore, the adjusted enery

EP = yv-c

factor would he

(A)

The following examples for clothes washers A and B are demised to

illustrate the effect that credit and dehit would have on the energy factor.

The data shown in Table 5 for washers A and B and the dehit and credit values

shown in Table 6, are substituted into equations 5 and A to obtain a comparison

of energy factors and percentage chanee fsee Table 7^ as affected by credit and

debit corresponding to various moisture retention.

Figure 12 shows how the energy factor for washers A ?=>nd B are affected by

various moisture retentions. An energy credit or debit for a given moisture

retention has a greater effect on the enemy factor for washer A than for washer

B. Por exam.ple, if the moisture retention for clothes washer A is reduced to

405, a corresponding one kWh credit woul d increase the enery factor f^om 0.85

ft /kWh to 1.19 ft' /kWh which is a 44^ improvement in the enery factor.

/

/ 9
However, if the moisture retention of clothes washer B is reduced to 40*, a

corresponding one kWh credit would increase the energy factor from 0.70 ft' /kWh

to 0.00 fir /kWh which is a 2R* Improvement in the energy factor. The

significance of this example is that the higher the original b?se energy factor

the greater the impact of the dehit/credit plan.

V. Conclusions

For most clothes washers the water retention in a standard 7 lh test load

range between 50* to 70* of dry test load weight. Water extraction during a

spin cycle can he improved by increasing spin speed and/or spin time. However,

increasing spin speed has the greatest effect on reducing moisture retention.

A credit/debit plan has been proposed for providing an incentive for

manufacturers to improve water extraction performance fby increasing spin speed,

spin time etc.''. Using this plan, a reduction in the water retention to 40* by

two representative clothes washers has shown to impro^ the energy factor ^y 447?

and 28*.

Annual energy savings of about .720 per year can be achieved if the water

extraction performance is improved to reduce the moisture retention by 25

percentage points ( 65^ to 40*^ . For a 10* discount rate an^ a 5 year payback

period, a 720 annua] saving will justify an increase in purchase cost up to 750.

However, for 5 year payback period the economic justifiable purchase orice

increase should not exceed $75*

10
References

1. Test Procedure for Clothes Washers, Federal Register, Vol. 42,

No. 188. September 28, 1°77.

2. Toner, S., "The Sffectw® of Water Temperature on Washing Performance,"

Milestone Report, National Bureau of Standards, Washington, D.C., IQ"7?.

/ 11

INCREMENTAL

DRYER

EFFICIENCY

VERSUS

MOISTURE

RETENTION

anvM jo sai

A3N3I3IJJ3 83X110 mN3W3U3NI

13

MOISTURE

RETENTION,

%
WATER RETENTION* VERSUS TEST LOAO WEIGHT

FOR CLOTHESWASHERS Ar Er H

Note:

1. For Washer A and E , test conducted with warm

water rinse

2. Washer H test conducted witfr cold water rinse

FIGURE 3

14
CLOTHES DRYER ENERGY CONSUMPTION* FOR DRYING

TEST LOADS SPUR IN> TWO CLOTHES WASHERS

DRYER A 70% Initial 4% End

WITH moisture moisture

WASHER i retention retention

DRYER A 41.0% Initial 4.0% End H Q<v IrUtfh

1

|

•

WITH moisture moisture

VJ a WV* R If II WASHER & retention retention

1

ENERGY SAVINGS j

1

1

( 1.0 2.0

DRYER ENERGY INPUT, kWh

FIGURE 4

15

/
MOISTURE RETENTION* VERSUS SPIN-TIME

FOR THREE CLOTHES WASHERS

Note: Spin-cycle automatically terminates after

6 minutes for Washer I

5 minutes for washer A

314 minutes for washer G

FIGURE 5

16
CLOTHES

WASHER

H

!

MOISTURE

RETENTION

VERSUS

TUB

SPIN

SPEED

iN33H3d N0I1N313B 3dniS10M

17

TUB

SPIN

SPEED,

RPM
ENERGY

CONSUMPTION

VERSUS

INITIAL

MOISTURE

RETENTION

HMX NOLUWnSNOO A9H3N3

18

INITIAL

MOISTURE

RETENTION,

PERCENT
MOISTURE

RETENTION

PER

RPM

|%/RPM|

CHANGE IN MOISTURE RETENTION RATE VERSUS SPIN SPEED

FIGURE 8

19
EVALUATION

OF

WRINKLE

HYPOTHESIS

BY

SIX

JUUUtS

HYPOTHESIS:

More

wrinkles

when

spun

at

900

RPM

than

at

400

RPM

CMe

CO

Q3WHIJN03 SlS3H10dAH Q31V03N SIS3H10dAH

A3N3n03H3

20
ASSIGNED

ENERGY

DEBITS

-

KWh

ASSIGNED

ENERGY

CREDITS

-

KWh

CREDITS / DEBITS TO INFLUENCE THE ENERGY EFFICIENCY FACTORS

OF CLOTHES WASHERS

figure 10

21
AbblbNtU

ENERGY

DEBITS

-

kWh

ASSIGNED

ENERGY

UNEDII*

-

KWn

i

i

i

i

CREDITS AND DEBITS TO INFLUENCE

THE ENERGY EFFICIENCY FACTORS OF CLOTHES WASHERS

1 1 1 1 1 1 1 1 1

i i i ' i 35 40 45 50 55 60 65 70 75 80 85 90 95 100

% MOISTURE RETENTION

22
ENERGY

FACTOR

CLOTHES WASHER ENERGY FACTOR, AS EFFECTED BY CREDITS

AND DEBITS FOR REDUCTION Itt MOISTURE RETENTION

1

;i FIGURE 12

!

i

i

23
TABLE 1

.

Clothes Dryer Incremental Energy Efficiency and A^unt

of Water Removed During Each 5 Minute Interval

Run Time Incremental

( min' Water Removed

fits)

Cumul ative

Water Removed

(ihs )

Incremental

Energy

Consumed

(kWh)

Incremental

Efficiency

l^s Ho0

''“kWh

c;j 0.820 0.828 0.424 1 .05

10 0.Q05 1 .733 0.421 2.15

15 0.027 2.660 0.424 2.18

20 0.Q16 3-576 O.A15 2.20

25 0.871 4.447 0.423 2.06

30 0.4-64 4.911 0.418 i.n

/ 24
TABLE 2. Water Retention for Various Clothes

Washers with 6 Pound Test Load

Mact ine Water Retention

Warr. Rinse Co?* Rinse

A

B

C

D

E

E*

F

a

H*-*

54 53 . 53 —

50 —

57 61

66 67

69 74

61 67

46 —

62 68

*E —>8.2 round test load 50* cotton,

50# polyester

*-*H —• front loader

25
TABLE 5- Potential Dryer Energy Savings

for Various Moisture Retentions

in a Seven Pound Test Load

* Moisture

Retention

Pounds of

Water Re^ainins

in Clothes

Differential

Water Removable

Below 70^ Level

Energy

Savins*

0?Wh)

100 7.00

qc:J 6.65

QO 6.50

35 5.°5

SO 5-60

75 5.25

70* 4-°0

65 4.55

60 4.20

55 5-85

50 5-50

45 5-13

40 2.80

-2.10 -1.01

-1 .75 -0.85

-1 .40 -0.68

-1 .05 -0.50

-0 70 -0.54

-0.55 -0.17

0 0

0.55 0.1 7

O.vo 0.54

1 .05 0.50

1 .40 0.68

1 .75 0.85

2.10 1 .01

*A11 differential moisture remold and energy savinss are measured

relative to the 7C^ moisture retention 1 e^e1 and 2.0V Ih/kWh.

/ 26
lABLE 4- Potential. Dollar Energy Savings for Various Holding Periods

Periods Annual.

Uniform Series

Present Worth

Present Value

of Annual Energy Barrings

Uote:

Years Savings 8 P’actors Case "! Case ;

3 20 2.48 4Q .60 28.76

5 20 3.7Q 75 . 80 4V.Q8

10 20 6.14 122.80 7].. 22

15 20 7.60 152.00 88.16

For case 2 the present worth energy savings is about

56$ the present worth of the annual energy saving*.

27
TABLE 5- Machine Capacity an-i Energy Consumption Data

Washer A Washer

1

.

Useful Capacity, XL, , ft^ 2.71 3; 12

2. Energy Consumption, E_, Wh 3-27 4.18

ft3

3. Base Energy Factor, EF,-^^ 0.83 o • o

28
TABLE 6. Debit/Credit fron Figure 11

Water

Retention, R

(*)

Credit, C

kWh

Debit, C

kWh

00 0 -0.68

71 0 0.68

50-70 0 0

40.0 0.68 0

40 1 .01 0

29
TABLE

Water

Retention, *

40

4Q.Q

50-70

Base

SO

7. Energy Factor and Energy Factor Change as a

Function of Water Retention for Two Washers, Using

Proposed Credit/Debit Plan. (See Figure 11.'

Energy Factor, EF, and Energy Factor

R Change. EF, “3

n acre h

i Tnrmr^,—f

f3

m EF, 3

~3

PTH - 0

. mi 0

AJJ.

y

1 .IQ 44 0.90 28

1.05 27 0.82 l7

0.83 0 0.70 0

0.6Q -17 0.60 -14

30
APPENDIX A

lest Procedures for Clothes Washers

Federal Register, 7ol. 42, No. 188,

Wednesday, September 28, 1 Q77.

Chapter II, Federal Energy

Administration Part 430—Energy

Conservation Proyran for Appliances

31
Test Procedure Changes

Modify section 2.8.1 to read as follows'

2.8.1 Top-loader clothes washers. The top loader clothes washer shall ^e

tested with a clothes load as described in 2.^.1.

3. 2. 1.2 Moisture retention. Remove and weigh the wet clothes load at the

conpletion of the normal cycle. Determine percent of moisture retention as foil cws:

W - W,

R. moisture retention, = —n x 1.00, m

W = weight of wet load uoon ccmnletior of snin cycle

w

as determined according to 2. 5.1-1, lbs.

V, = bone dry weight of the test ]nad as determine^ accordi rg to 2.7.1.,

b ,,lbs.

4. 7 Ad •'listed total per cycle energy consumption when electrically heate^

water is used. Calculate the ad-'uste^ total per cycle energy consumption

using for electrically heated water, as defined in 4.6, expressed in

kilcwatt^hcurs per cycle.

where:

C = 0.68 -r ) for R < 50

C = 0 for 50 < R < TO

C = -0.68 for R > 70

Change section 450.22, column 5, first paragraph (2'> to read as follows:

' 2

' The energy factor for automatic and semi-automatic clothes

washers shall be the quotient of the cubic foot capacity of the clothes

container as determined in 5*1 of Appenxix J to this suhpart divided by the

clothes washers adjusted total energy consumption per cycle, as determined

in 4.7 and the result being rounded off to the nearest 0.01 cubic foot per

kilowatt-hour

.

/

/ 32
NBS-II4A irev. 2 -ac) U.S. OEPT. OF COMM.

BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

SHEET (See instructions) NBSIR 81-2309 September 1981

4. TITLE ANO SUBTITLE

An Evaluation of Assigning Credit/Debit to the Energy Factor of Clothes

Washers Based on Water Extraction Performance

5. AUTHOR(S)

C. Denver Lovett

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON*, D.C. 20234-

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Department of Energy

1000 Independence Ave.

Washington, D. C. 20585

10. SUPPLEMENTARY NOTES

| Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most si gnificant in formation. If document includes a significant

bibliography or literature survey, mention it here)

To reduce the moisture retention of a clothes load from 65% to 40%, a clothes

dryer uses about 200 times more energy than a clothes washer. Therefore, improving

the clothes washer's water extraction performance can significantly reduce

energy-use of a dryer. For example, a clothes dryer uses about 40% less energy,

when the clothes washer extracts 38% more water from the clothes load. Based on clothes washer extraction performance, NBS has developed, for the Department of

Energy (DOE), a procedure for assigning credit/debit to the energy factor of a clothes washer. The purpose of this procedure is to provide an incentative for

clothes washer manufacturers to improve the water extraction performance of washers.

Using this procedure, the energy factors for two clothes washers improves by 44%

and 28% respecti vely . This energy factor improvement corresponds to improved water

extraction which reduces the moisture retention of the clothes load from 65% to 40%,

One case study shows that dryer energy savings, resulting from reduced moisture

content, justi fies ,$50 incremental cost for improved water extraction performance

for clothes washers.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Clothes washers; clothes dryer; extraction performance; energy savings;

credits/debits; wrinkle performance

13. AVAILABILITY 14. NO. OF

| | Unlimited

|Y ] For Official Distribution. Do Not Release to NTIS

1 | Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

PRINTED PAGES

15. Price

Qj Order From National Technical Information Service (NTIS), Springfield, VA. 22161

/ USCOMM-OC 8O43-P30
. ' I