7B

- i APPENDIX 7B. ENERGY USE IN COMMER ICAL APPLICATIONS

TABLE OF CO NTENTS

7B

- 1 INTRODUCTION

................................ ................................ ................................ ......... 7B

- 1

7B

- 2 ANSI/ASHRAE STANDARD FOR THERMAL COMFORT

................................ ..... 7B

- 1

7B

- 3 NATIONAL SOLAR RADIA TION DATA

................................ ................................ . 7B

- 2

7B

- 4 EQUATIONS AND CALCUL ATIONS

................................ ................................ ....... 7B

- 8

LIST OF TABLES

Table 7B

- 3.1 Weather Stations Classified as Desert

................................ ......................... 7B

- 6

Table 7B

- 4.1 Regression Equations

................................ ................................ ................... 7B

- 9

Table 7B

- 4.2 Building Types and Abbreviations

................................ ............................ 7B

- 10

Table 7B

- 4.3 Building Schedules and Abbreviations

................................ ...................... 7B

- 10

Table 7B

- 4.4 Equations for Portable AC Operating Hours by Building Type and

Schedule, Non

- Desert Locations

................................ ............................... 7B

- 11

Table 7B

- 4.5 Equations for Portable AC Operating Hour by Building Type and

Schedule, Desert Locations

................................ ................................ ........ 7B

- 12

Table 7B

- 4.6 CBECS 2003 Building Codes Matched to Building Types in Portable

AC Equations

................................ ................................ ............................. 7B

- 13

LIST OF FIGURES

Figure 7B

- 2.1 ANSI/SHRAE Standard 55

- 2004: Thermal Environmental Conditions

for Human Occupancy

................................ ................................ ................. 7B

- 1 Figure 7B

- 3.1 National Solar Radiation Database Stations

................................ ................ 7B

- 3 Figure 7B

- 3.2 Hours that Exceeded ASHRAE Standard 55 Comfort Zone in Palm

Springs CA, 1991

................................ ................................ ......................... 7B

- 5 Figure 7B

- 3.3 Hours that Exceeded ASHRAE Standard 55Comfort Zone Compared

to CLDD

................................ ................................ ................................ ....... 7B

- 6 Figure 7B

- 3.4 Hours that Exceeded ASHRAE Standard 55 Comfort Zone versus

CLDD Highlighting Various Regions

................................ ......................... 7B

- 8 Figure 7B

- 4.1 Hours that Exceeded ANSI/ASHRAE Standard 55 Comfort Zone as a

Function of Cooling Degree

- Days, Continental United States

.................... 7B

- 97B

- 1 APPENDIX 7B. ENERGY USE IN COMMERICAL APPLICATIONS

7B

- 1 IN TRODUCTION

This appendix describes the method the U.S. Department of Energy (DOE) use d to
calculate the energy use of portable air conditioners (ACs) installed in commercial applications

. DOE applied data regarding local cooling degree

- days to the commercial buildings it sampled from the Energy Information Administration's 2003 Commercial Buildings Energ y Consumption

Surve y (CBECS)

. 1 DOE calculated the annual operating hours for portable ACs in each sampled commercial building by establishing a relationship between cooling degree

- days and operating hours for various combinations of building type and build ing schedule. DOE focused on buildings that have no central air conditioning, as reported in the 2003 CBECS.

7B

- 2 ANSI/ASHRAE STANDARD FOR THERMAL COMFORT

DOE assumed that a portable AC is operated when outdoor air conditions exceed the

comfort zone described by ANSI/ASHRAE Standard 55

- 2004

, Thermal Environmental Conditions for Human Occupancy (see F igure 7 B

- 2.1 )

. 2

Figure 7B

- 2.1 ANSI/SHRAE Standard 55

- 2004: Thermal

Environmental Conditions for Human Occupancy

ANSI/ASHRAE Standard 55 is based on the following assum ptions.

 M etabolic rates of occupants are 1.1 met ( occupants are engaged in near

- sedentary physical activity)

.7B

- 2

 Occupants are wearing 0.5 clo of clothing insulation, a level typical of clothing worn

when the outdoor environment is warm

.

 A ir speeds are not g reater than 0.20 m/s (40 ft/min)

.

 H umidity is at or near the upper recommended limit, and the humidity ratio is 0.012

.

The range of operative temperatures presented in Figure 7B

- 2.1 reflects an assumed 80

- percent rate of occupant acceptance. That percentage reflects a 10

- percent dissatisfaction criterion for a general (whole

- body) thermal comfort index based on a combination of two indexes. Predicted mean vote (PMV) is an index that predicts the mean value of the votes of a large group of persons o n a seven

- point thermal sensation scale. The predicted percentage of dissatisfied (PPD) index establishes a quantitative prediction of the percentage of people

dissatisfied with the thermal environment determined from PMV. The overall index is termed the

P MV

- PPD index. An additional average 10

- percent rate of dissatisfaction may occur from local (partial

- body) thermal discomfort. A portable air conditioner is assumed to operate if outdoor conditions exceed the outdoor comfort zone, as defined by a W (humidi ty ratio) greater than
0.012, or a T (temperature) that exceeds Tcomf for that humidity ratio. Tcomf is given by the following equation.

where W is the humidity ratio of outdoor conditions for a given hour.

To estimate how often outdoor conditions exceed ANSI/SHRAE Standard 55

- 2004 (OH55) , DOE used the following equation.

OH55 = (a * CDD) + b

Where:

OH55 = average annual hours when outdoor air conditions exceed the ASHRAE

Standard 55 comfort zone,

CDD = the number of annual cooling degree

- days (65 °F) for a given location, and

a and b = linear fit parameters.

7B

- 3 NATIONAL SOLAR RADIA TION DATA

To estimate portable air conditioner (AC) operation and energy use in buildings from the CBECS sample, DOE used da ta on cooling degree

- days (CDDs) from the National Solar Radiation Database (NSRDB) for 1991

– 2005

. 3 The 1991

– 2005 NSRDB , which is an update of

the 1961

– 1990 NSRDB data base

, is an hourly ground

- based data base of solar and meteorological fields for 1

, 454 NSR DB stations . The data , which provide a complete 15

- year period of record for 858 sites

. The NSRDB stations are divided into three classes (see Figure 7B

3.1 ).7B

- 3 Figure 7B

- 3.1 National Solar Radiation Database Stations

NSRDB stations are assigned a U.S. Air Force class number as follows:

 Class I stations have a complete period of record for solar and key meteorological

fields (all hours for 1991

– 2005) and have the highest

- quality solar of modeled data (221 sites).

 Class II stations have a complete period of record but significant periods o f interpolated, filled, or otherwise lower

- quality input data for the solar models (637 sites).

 Class III stations have some gaps in the period of record but at least 3 years of data that might be useful for some applications (596 sites).

The NSRDB datab ase has complete fields for measured hourly dry bulb temperature, dew point temperature, relative humidity, and atmospheric pressure for all class I and class II stations.

DOE used data from the dry bulb temperature, relative humidity, and atmospheric pres sure fields

t o calculate the humidity ratio for each operating hour for every commercial building in DOE's sample

. DOE calculated t he humidity ratio ( W ) using procedures from ASHRAE 's 2005

Handbook

–Fundamentals

. a T he process utilizes dry bulb temperature, relative humidity, and

a Chapter 6 in the 2005 ASHRAE Handbook is titled Psychrometrics. Under the section on " Numerical Calculation of Moist Air Properties, " Situation 3 describes the process for calculating humidity ratio ( W ) from dry bulb temperature, relative humidity, and pressure.7B

- 4

pressure . The saturation pressure for the dry bulb temperature is calculated using the following equation

.

Where :

C8 =

- 5.8002206 E+03

, C9 = 1.3914993 E+00

, C10 =

- 4.8640239 E

- 02

, C11 = 4.1764768 E

- 05

, C12 =

- 1.4452093 E

- 08

, C13 = 6.5459673 E+00

, Pws = saturation pressure, Pa , and T = absolute temperature, K = °C + 273.15

The partial pressure ( Pw ) of the water vapor is the saturation pressure multiplied by the relative humidity :

The humidity ratio, W

, is defined as the ratio of the mass of water vapor to the mass of dry air contained in a given air sample. The ratio can be calculated from the pressure and the partial pressure of the water vapor as:

By comparing the conditions for a given hour in a specific geographic l ocation against

the criteria established in ANSI/ASHRAE Standard 55

- 2004 , we can determine whether a portable air conditioner would have operated during that hour. Figure 7B

- 3.2 shows the 2,281

hours in 1991 that exceeded the comfort zone for Palm Springs , CA

.7B

- 5 Figure 7B

- 3.2 Hours that Exceeded ASHRAE Standard 55

C omfort Z one in Palm Springs CA

, 1991

Figure 7B

- 3.3 shows hours that exceeded the ANSI/ASHRAE Standard 55

- 2004 comfort

zone compared to CLDD for 15 years (1991

– 2005) for all NSRDB class 1 and c lass II stations.7B

- 6 Figure 7B

- 3.3 Hours that Exceeded ASHRAE Standard

55 C omfort Z one Compared to CLDD

The lower branch of data points (outlined in red in Figure 7B

- 3.3 ) reflects low

- desert

locations , where h umidity is not a factor that affects comfort. After examining the data, DOE

classified the following sites as desert.

Table 7B

- 3.1 Weather Stations Classified as Desert

Station S tate

Davis Monthan Air Force Base AZ Deer Valley/Phoenix AZ Douglas Bisbee

- Douglas Int'l

. Airport AZ Kingman ( AMOS* ) AZ

Luke Air Force Base AZ Phoenix Sky Harbor Int ' l

. Airport AZ

Scottsdale Muni Airport? AZ

Tucson Int ' l

. Airport AZ

Yuma Int ' l

. Airport AZ

Yuma Marine Corps Air Station AZ

Bakersfield Meadows Field CA Blythe Riverside Co Airport CA

China Lake Naval Air Station CA Daggett Barstow

- Daggett Airport CA

Edwards Air Force Base CA Imperial CA

Lancaster Gen

. Wm

. Fox Field CA7B

- 7 Station S tate Needles Airport CA Palm Springs Int ' l

. Airport CA Palm Springs Thermal Airport CA Palmdale Airport CA Twentynine Palms CA Carlsbad Cavern City Air Term inal NM Deming Muni [ Airport] NM

Holloman Air Force Base NM

Las Cruces Intl [ Airport] NM

Roswell Industrial Air Park NM

Truth or Consequences Muni [ Airport] NM Las Vegas Mccarran Int ' l

. [ Airport] NV Mercury Desert Rock Airport [S URFRAD † ] NV

Nellis Air Force Base NV

El Paso Int'l. [ Airport ] [U T ‡ ] TX Saint George ( AWOS § ) UT

* AMOS = Automated Meteorological Observing System

† SURFRAD = Surface Radiation Network

‡ UT = University of T e xas??

§ AWOS = Automated Weather Observing System

Figure 7B

- 3.4 shows NSRDB data points highlighting desert and tropical sites. The uppermost points represent data from stations in Hawaii, Guam

, and the Caribbean.7B

- 8 Figure 7B

- 3.4 Hours that Exceed ed ASHRAE Standard 55

C omfort Z one v ersus CLDD Highlighting Various

R egions

7B

- 4 EQUATIONS AND CALCUL ATIONS

DOE removed the sites in Hawaii, Guam, and the Caribbean islands from consideration because their conditions of high humidity likely would call for use of a portable dehumid ifier rather than a portable AC. After removing the sites in Hawaii, Guam, and the Caribbean islands from DOE's set of data for commercial buildings

, DOE performed regressions to predict the hours per year that exceed ASHRAE Standard 55 from the number of cooling degree

- days for each year. The data points and regression lines are shown in Figure 7B

- 4.1 for all hours of the

year. The figure reflects 15 years' worth of data from 842 sites in the continental United States.7B

- 9 Figure 7B

- 4.1 Hours that Exceed ed ANSI/ASHRAE Standard 55

Comfort Zone as a Function of Cooling Degree

Days , Continental United States

The regression equations used to derive the average annual number of hours when

outdoor air conditions exceed ASHRAE Standard 55 comfort zone ( OH55) are shown in Table

7B

- 4.1

.

Table 7B

- 4.1 Regression Equations Region E quation R 2 No. of

S ites

Non

- desert OH55 = 2.759 x CLDD + 127.99 0.9224 809

Desert OH55 = 1.153 x CLDD + 574.04 0.8714 33

The number of annual hours that exceed the ASHRAE Standard 55 comfort zone in a given geographic location will differ depending on building schedule, which refers to the period(s) when a building is open. Thus, DOE performed the regression for various combinations of building type and schedule, yielding somewhat different equations for each combination. The building types included are: assembly, education, food service, office, retail, and warehouse. For each building type, DOE estimated operating hours for building schedules that included : (1) open 24 hours a day and seven days a week; (2) open business hours Monday throu gh Friday; (3) open business hours Monday through Saturday; (4) open business hours Monday through Friday and Sunday; (5) open business hours all week. The building types and schedule abbrev iations are

shown in Table 7B

- 4.2 and Table 7B

- 4.3

. DOE assumed that if the occupancy rate was greater

t han 20 percent of full occupancy, a portable AC would operate when outdoor air conditions

exceeded the ASHRAE standard 55 comfort zone.7B

- 10

Table 7B

- 4.2 Building T ype s and A bbreviation s Building Type Abbreviation Assembly ASM

Education EDU

Food service FDS Lodging LOD

Medical MED

Office OFF

Outdoor OUT

Retail RET

Warehouse WHS

Table 7B

- 4.3 Building S chedules and A bbreviation s

Building Schedule Abbreviation

24 hours per day, 7 days per week 247 Business hours, Monday

– Friday M

- F Business hours, Monday

– Friday and Saturday and Sunday ALL

The equations for predict ing the hours per year a portable AC would operate for various

commercial building types and schedules for non

- desert locations are shown in Table 7B

- 4.4

.7B

- 11

Table 7B

- 4.4 Equations for Portable AC O p erating H our s b y B uilding T ype and

S chedule , Non

- Desert Locations

Building Type Times

Open Equation R 2

ALL 247 ROH55 = 2.759 x CLDD + 127.99 0.9224

OUT M_F ROH55 = 1.974 x CLDD + 93.29 0.9458

OUT ALL ROH55 = 2.759 x CLDD + 127.99 0.9430

ASM M_F ROH55 = 0.751 x CLDD + 119.67 0.9458

ASM ALL ROH55 = 1.396 x CLDD + 169.18 0.9430

EDU M_F ROH55 = 1.001 x CLDD + 117.11 0.9412

EDU ALL ROH55 = 1.398 x CLDD + 163.52 0.9424

FDS M_F ROH55 = 1.243 x CLDD + 112.91 0.9354

FDS ALL ROH55 = 1.510 x CLDD + 166.44 0.9408

LOD M_F ROH55 = 1.471 x CLDD + 17.11 0.9428

LOD ALL ROH55 = 2.206 x CLDD + 40.94 0.9408

MED M_F ROH55 = 1.001 x CLDD + 128.06 0.9428

MED ALL ROH55 = 1.151 x CLD D + 148.72 0.9408

OFF M_F ROH55 = 0.918 x CLDD + 119.76 0.9428

OFF ALL ROH55 = 1.510 x CLDD + 166.44 0.9408

RET M_F ROH55 = 0.751 x CLDD + 119.67 0.9458

RET ALL ROH55 = 1.281 x CLDD + 170.57 0.9450

WHS M_F ROH55 = 0.836 x CLDD + 109.17 0.9422

WHS ALL ROH55 = 1.514 x CLDD + 178.06 0.9419

[The top (highlighted) row of the table pertains to any building type that operate on a 24/7 schedule, because the occupancy rate will exceed 20 percent at all times

. The analysis does not account for differences in building operation schedules on holidays.

The equations for predict ing the hours per year a portable AC would operate for various building types and schedules for desert locations are shown in Table 7B

- 4.5

.7B

- 12

Table 7B

- 4.5 Equations for Portable AC O perating H our b y B uilding T ype and

S chedule

, Desert Locations

Buildin g Type Times

Open Equation R 2

ALL 247 ROH55 = 1.153 x CLDD + 574.04 0.9224

OUT M_F ROH55 = 1.974 x CLDD + 93.29 0.8353

OUT ALL ROH55 = 2.759 x CLDD + 127.99 0.8925

ASM M_F ROH55 = 0.289 x CLDD + 546.12 0.8353

ASM ALL ROH55 = 0.600 x CLDD + 721.20 0.8925

EDU M_F ROH55 = 0.409 x CLDD + 532.56 0.8723

EDU ALL ROH55 = 0.572 x CLDD + 741.06 0.8794

FDS M_F ROH55 = 0.553 x CLDD + 449.33 0.8914

FDS ALL ROH55 = 0.663 x CLDD + 690.02 0.8985

LOD M_F ROH55 = 0.642 x CLDD + 40.06 0.8260

LOD ALL ROH55 = 0.951 x CLDD + 157.74 0.8985

MED M_F ROH55 = 0.402 x CLDD + 603.12 0.8260

MED ALL ROH55 = 0. 458 x CLDD + 706.19 0.8985

OFF M_F ROH55 = 0.353 x CLDD + 573.23 0.8260

OFF ALL ROH55 = 0.663 x CLDD + 690.02 0.8985

RET M_F ROH55 = 0.289 x CLDD + 546.12 0.8353

RET ALL ROH55 = 0.534 x CLDD + 749.00 0.8813

WHS M_F ROH55 = 0.317 x CLDD + 524.97 0.8087

WHS ALL ROH55 = 0.612 x CLDD + 837.58 0.8682

To estimate the operating hours for portable ACs in each building

in the CBECS 2003 sample that has a portable AC , DOE identified the building type and schedule using information provided by CBECS, then applied the appropriate equation (non

desert or desert) combined with the number of cooling degree

- days for the location of the building. DOE adjusted the results by applying a scaling factor to account for the difference between the number of building operating hours that were assumed when deriving the equations and the actual building operating hours reported by CBECS 2003

. Table 7B

- 4.6 shows the CBECS building codes matched to the building types in the regression equations.7B

- 13

Table 7B

- 4.6 CBECS 2003 Building Code s Match ed to Building Types in Portable AC

Equation s CBECS

2003 PBA

Code * Definition Building Type

Match CBECS 2003

Buildings with

Portable ACs %

1 Vacant Not Applicable

2 Office OFF 8. 8

4 Laboratory MED 0. 0

5 Nonrefrigerated warehouse WHS 14

. 3

6 Food sales RET 5

. 5

7 Public order and safety OFF 8

. 8

8 Outpatient health care MED 0. 0

11 Refrigerated warehouse WHS 0.0

12 Religious worship ASM 7 .7

13 Public assembly ASM 7

. 7

14 Education EDU 12. 1

15 Food service FDS 2

. 2

16 Inpatient health care MED 0. 0

17 Nursing MED 2

. 2

18 Lodging LOD 1

. 1

23 Strip shopping mall RET 0.0

24 Enclosed mall RET 0.0

25 Retail other than mall RET 1. 1

26 Service RET 24

. 2

91 Other OFF 4

. 4

* PBA = Principal building activity

.

The approach described here provides a best guess of the operating hours for a portable

AC in a particular CBECS building. O perating hours are affected by some factors not included in the analysis, however, such as interior heat gains from equipment or people and solar gains. To develop a distribution of the number of operating hours for each sa mple building, DOE added an error band to the value derived using the regression equation. The error band includes values that

are ±10 percent from the regression line for the appropriate building type and schedule

combination.

The operating hours for po rtable ACs in commercial buildings were estimated based on the cooling climate in 2003. To match the 115

- year average CDD values, DOE decreased the operating hours estimated for commercial applications by 2 percent on average.7B

- 14

REFER ENCES

1 U.S. Department of Energy

– Energy Information Administration. Commercial Buildings Energy Consumption Survey. 2003. (Last accessed September 8, 2014.)

< http://www.eia.gov/consumption/commercial/data/2003/ >
2 American National Standards Institute and American Society of Heating, R efrigeration

, and Air

- Conditioning Engineers, Inc. ANSI/ASHRAE 55

- 2004 Thermal Environmental Conditions for Human Occupancy

. 2 004.

3 National Renewable Energy Laboratory

. National Solar Radiation Database : 1991

– 2005 Update: User’s Manual

. May 2007. Technical Report NREL/TP

- 581

- 41364

. (Last accessed September 12 , 2014.) < http://www.nrel.gov/docs/fy07osti/41364.pdf >