energy and cost analysis of commercial hvac equipment
TRANSCRIPT
University of Tennessee, KnoxvilleTrace: Tennessee Research and CreativeExchange
Masters Theses Graduate School
3-1979
Energy and Cost Analysis of Commercial HVACEquipment: Offices and HospitalsRobert E. Lyman Jr.University of Tennessee - Knoxville
This Thesis is brought to you for free and open access by the Graduate School at Trace: Tennessee Research and Creative Exchange. It has beenaccepted for inclusion in Masters Theses by an authorized administrator of Trace: Tennessee Research and Creative Exchange. For more information,please contact [email protected].
Recommended CitationLyman, Robert E. Jr., "Energy and Cost Analysis of Commercial HVAC Equipment: Offices and Hospitals. " Master's Thesis,University of Tennessee, 1979.https://trace.tennessee.edu/utk_gradthes/3129
To the Graduate Council:
I am submitting herewith a thesis written by Robert E. Lyman Jr. entitled "Energy and Cost Analysis ofCommercial HVAC Equipment: Offices and Hospitals." I have examined the final electronic copy of thisthesis for form and content and recommend that it be accepted in partial fulfillment of the requirementsfor the degree of Master of Science, with a major in Mechanical Engineering.
William S. Johnson, Major Professor
We have read this thesis and recommend its acceptance:
J.F. Bailey, James A. Eiler
Accepted for the Council:Dixie L. Thompson
Vice Provost and Dean of the Graduate School
(Original signatures are on file with official student records.)
../ !
To the Graduate Council:
I am submitting herewith a thesis written by Robert E. Lyman, Jr. entitled "Energy and Cost Analysis of Commercial INAC Equipment: Offices and Hospitals." I recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Mechanical Engineering.
We have read this thesis and recommend its acceptance:
Accepted for the Council:
Vice Chancellor Graduate Studies and Research
5
ENERGY AND COST ANALYSIS OF COMMERC IAL HVAC EQU IPMENT :
OFF ICES AND HOSP ITALS
A Thes i s
Pres ented for the
Master of Science
Degree
The Univers ity of Tennes see, Knoxv ille
Robert E. Lyman, Jr.
March 19 79
ACKNOWLE DGMENTS
The author wi shes to expre s s h i s s incere apprec iat ion to·h i s
facu l ty advi sor , Dr . W . S . Johns on , and h i s project supervi sor , Jerry
Jack son , for their guidanc e and cons truct ive comments throughout thi s
project . He i s grateful t o Eric Hirst for h i s as s i s tance i n preparing
this report . He great l y appreciates the cooperation o f the s taff at
Oak Ridge Nat ional Laboratory . Re s e arch performed at the Oak Ridge
National Laboratory was spon sored by the Department of Energy under
contract with Union Carb ide Corporat ion .
i i
ABST RACT
A study was made to det ermine annua l ene rgy us e in s eve ra l
typ i c a l h e at in g , vent i lat ing , and ai r condit ioning ( HVAC) s ystems for
two comme rc i a l bui l din g type s : offi ces an d hospi t a l s . Th e s t udy was
part of a program at Oak Ri dge N at i on a l Laborat ory to deve l op a mode l
to pre dict ene rgy us e in the comme rci a l s e ct or o f t h e Un i t e d St at e s .
Th is s tudy's object ive i s t o de fin e re l at i onship s b etween ene rgy us e
and cap i t a l cos t for comme rci a l HVAC syst ems .
The NECAP c omput e r pro gram was us ed to ana ly ze t h e HVAC syst ems'
energy us e . Both p re - embargo an d current ene rgy e ffi cient HVAC
system de s i gns were mode l e d with seve ra l ene rgy cons ervat ion opt i ons
cons ide re d for e ach. Th e s e opt ions inc l uded e conomi z e r cyc l e s , e xhaus t
ai r h e at rec ove ry , imp rov e d c ont rol s , doub l e bundle e xch ange rs , imp rove d
equipment e ffi ci en ci es , part i a l sol ar h e at in g , an Annua l Cyc l e Energy
Sys t em ( ACES) h e at s t orage system and a tot a l ene rgy system (ons ite
e l e ct ric ity gene rat ion with was t e h e at re covery) . Bui l din g mode ls us e d
correspond t o nat i on al averages for fl oor sp ace an d const ruct ion .
Resu lts show that us e of exhaus t a i r he at re cove ry in th e
ori ginal des i gn of a bui l din g can provi de savin gs in b oth fi rs t c ost
and ene rgy use . S avin gs depend upon weathe r (pre dominant s avings are
in he at in g ene rgy ) and vent i l at i on rat e s . Re sults a l s o show that
us e of e l e c t ri c res i s t an ce heat app roximat e l y doub l es primary ene rgy us e
when comp are d to a s imi l ar sys tem us in g gas or oi l h eat . The us e o f gas
for coo l in g can in crease primary ene rgy us e by 40% ove r a s imi l ar s ystem
us in g e l ect ri c i ty for c ool in g .
i i i
i v
The "base" o ffi ce bui l ding had a dual duct syst em with gas heat and
electric coo l in g . Annual HVAC energy us e was 326 , 000 B t u per s quare
foot ( primary , or as mined, energy) with approximat ely 2.3 Btu requi red
t o meet each Btu of s pace conditionin g demand . An al ysis showed that
heat in g consumed 53% of the energy , c oo l in g 3 7%, and fans 10%. By
retrofitt ing thi s sys tem with exhaust ai r heat recovery , imp roved cont rol s
and a doub l e bundle exchanger, a 49% decreas e in energy us e could b e
obt ained with a payout o f les s than three years . If an energy effi ci ent
variab le vol ume ducting system was us ed in the ori ginal cons truction , a
44% reduction cou l d b e ach iev ed with a payout o f l es s than one year .
Simi l ar resu lt s were fotmd for the "bas e" hospit al with a s ing l e
z one/ fan coi l s ystem us ing gas h eat and elect ri c coo l in g . Annual HVAC
energy us e was 42 3, 0 00 Bt u per s quare foot with approximat ely 1. 8 Btu
required t o meet each Btu of demand . . An al y s is showed th at h eat ing
consumed 5 7%, coo l in g 36%, and fans 7% . By retrofitting with exh aus t
air h eat recovery , a 14% decreas e in energy us e cou l d b e achieved with a
payout o f les s than four years .
Energy us e est imat es developed in t his study are cons ist ent with
n at ion al energy use averages . The "bas e" o ffic e energy us e was 32%
higher than the nat ional average and th e b est energy cons ervat ion cas e
was 55% lower . The "bas e" hospital energy us e was 12% h igh er th an th e
nat ional average and th e b es t energy cons ervat ion cas e was 47% lower.
One reason for the higher energy us e fo r the b as e cas es in this study
was the exc lus ion o f vari at ions in operat in g strat egies (such as night
s etb ack and re duced vent il at i on durin g nono ccupied h ours ) .
TABLE OF CONTENTS
SECT ION
I. . INTRODUCT ION
Commerci al Eriergy Cons umpt ion Bui l ding Mo dels . . . . . . . Norma li zed Energy Use Fact or Weather Dat a . . . . . . . .
I I . HVAC SYSTEMS AND ENERGY CONSERVATION MEASURES
Heat ing and Cooling E quipment . . . . . . Duct ing Sys tems for the Office Bui l ding Duct i ng Sys tems for the Hos pit al . Energy Cons ervat ion Measures .
Economi zer cycle . . . . . . . . . . Exhaus t ai r heat recovery Res et cont rol s . . . . . . . Imp roved equipment effi ciencies Doub l e bundle exchangers . . . . . So l ar heat ing . . . . ACES system . . . . . To tal energy sys tem
III. ENERGY USE ANALYSIS
Computer Simu l ation Manua l Calculat ions . . . .
So lar heat ing Double bund le exchangers . Exhaus t ai r heat recovery Chi l l er efficiencies . Bo i l er effici enci es ACES system . . . . .
IV. ENERGY USE IMPACTS, CAP ITAL COSTS, AND PAYOUTS .
Energy Use Versus Fue l Combinat ion . Office Bui l ding HVAC Energy Us e
Econo mi zer cycle . . . . . . . . Exhaus t air heat recovery Res et cont ro l s (dua l duct only) Imp roved chi l ler effici ency Doub l e bundle exchangers . . . . . Sol ar heat ing ACE S system . . . . . .
v
PAGE
1
2 3 5 6
7
7 8
15 16 16 17 20 20 21 21 2 3 25
2 7
2 7 28 28 29 31 31 31 32
33
3 4 3 7 3 7 43 43 44 44 45 45
SECTION
vi
Tot al ene rgy syst em . . . . . . . . . . . . . Comb inat i ons o f cons ervat ion measures . . . .
Office Bui l di ng, HVAC Capit al Cos t s and Payout s Hospit a l HVAC Energy Use . . . . . . . Ho spit al HVAC Capit al Cost and Payouts Comp ari s on with Other St udies . . . . .
V. CONCLUSIONS .
Co nclus i ons on the Cons ervat i on Me asures Analyzed . Limit ations o f This Report and Recomme ndat i ons for
Furthe r Study . . . . .
REFE RENCES
APPENDICES
A. SAMPLE CALCULATIONS .
B. HVAC ENERGY.USE TABLES . .
C. HVAC ENERGY USE, CAPITAL COSTS AND PAYOUT .TABLES
VITA
PAGE
45 46 46 56 56 56
66
66
6 7
69
72
73
7 7
83
90
TABLE
1 .
2.
3 .
LIST OF TAB LES
Buil ding Mode l D e s cript ions . .
HVAC Ene rgy Use for a Dual Duct System in a Typ i ca l O ffi ce Bui lding b y Fue l Type . . . . . . . . .
HVAC Annua l Ene rgy Us e by Duct in g Sys t em and Bui l ding Type fo r G as He at ing and E l e ct ri c Coo ling . . . . . .
PAGE
5
34
3 7
4 . HVAC Ene rgy Us e , Capit al Costs and P ayout s o f Du al Duct in 40 , 500 ft 2 Offi ce . • . . . . . . . . . . . . . . . 49
5. Payout.vs . Fue l Comb in at i on for Cons ervat ion Me asure s in 40 ,500 ft2 .O ffice with Dua l Du ct . . . . . . . . . . 5 1
6. HVAC Ene rgy Use , Cap i t a l Costs and P ayout s for 100 , 0 00 ft 2
Hosp it al_with Sin g l e Zone/ Fan Co i l . . . . . . . . . . . 58
7. · Payout vs . Fue l Comb in at i on for HVAC Energy Cons e rvat i on Me asures in 100 , 0 0 0 ft � Hosp it al with Sing le Z one/ Fan Co i 1 . • . . . . . . . . . . • . . . • . . . . . . . 5 9
8. Comp aris on o f Energy Us e P redi ct e d an d "M ac ros copi c" Ave r age Energy Us e . . . . . . . . . . . . .
9 . Comp ari s on o f Ene rgy Use P red i ct e d and Energy Us e
6 3
Averages from Bui l ding Surveys . . . . . . . 6 4
10 . Comp aris on o f Offi ce HVAC Ene rgy Us e P re di ct e d with Th at in the Ran d Study . . . . . . . . . . . . . . . . . . 65
A- 1 . Resul t s o f S amp l e Cal cul at ion of So l ar Heating Sys tem Performan ce in Offi c e wi th Dua l Duct us ing E RDA Faci l i t i e s So l ar Des ign Manual . . . . . . . . . . .
A-2 . Samp l e Cal cu l at i on of Per formance o f Exh aus t Air He at Re cove ry in Hospit al . . . . . .
A-3 . Samp le C a l culat i on o f ACES Pe rfo rman ce
74
75
76
B-1. HVAC Energy Us e o f Dua l Duct in 40 , 5 0 0 ft 2 O ffi ce Bui l din g 78
B-2 . HVAC Ene rgy Us e of S in g l e Zone/F an Coi l in 4 0 , 5 0 0 ft 2
Of fice Bui l ding . . . . . . . . . . . . . . . . . . . . . 79
vi i
vii i
TABLE PAGE
B-3. HVAC Energy Use of VAV i n 40 , 500 ft 2 Office Bui lding . . . . 80
B - 4. HVAC Energy Use of Single Zone/VAV in 100, 000 ft 2 Hos pi t a l . 81
B-5. HVAC Ener gy Us e of Single Zone/Fan Co i l in 100, 000 ft 2 Hos pit al . . . . . . . • . . • . . • . . . . . . . 82
C-1. HVAC Energy Use, Capit al Cost and Payo uts of Single Zone/ Fan Co i l in 40, 500 ft 2 Office Bui l ding . . . . . . . . . 84
C-2. HVAC Ener� Use, Capit al Cost and Payouts of VAV in 40, 500 ft Office Bui lding . • . . . . . . . . . 85
C-3. HVAC Energy Use, Capit al Cost and Payouts of Sing�e Z one/VAV in 100, 000 ft 2 Hos pit a l . . . . • . . . . . . • . . . • . . 86
C-4. Payout vs. Fuel Combinat i on fo r Cons ervat ion Measures for
C-5.
C-6.
Sing le Zone/F an Coi l in 40 , 500 ft 2 Offi ce Bui l ding • · . . . . 87
Payout vs. Fuel Combinat i on for Cons ervat i on Measures for VAV in 40, 500 ft 2 Office Bui l ding . . . . . . . . . . . 88
Payout vs. Fuel Combi nat i on for Co nservat i on Measures fo r Single Zone/VAV in 100, 000 ft 2 Ho spi t a l . . . . . . 89
LIST OF FIGURES
FIGU RE PAGE
1 . Dual Duct System Schemat i c . . 10
2. Single Zone System Schemat i c . 12
3 . Four-Pipe Fan Coil System Schemat i c 13
4 . Vari able Ai r Volume (VAV) System Schemat i c . 14
5 . Schemat ic of Exhaust Ai r Heat Recove ry Exchange r -Sensible Type , wi th Typi cal Wint e r Temperatures Shown . . . . . 19
6. Sch emat ics o f Chille rs with and with out Double Bundle Exchangers . . . . . . . . • . . . . . . . 2 2
7. Schemat ic o f ACES System 2 4
8 . Month ly Energy Avai lable from Doub le Bun dle Exch anger in Dual Duct Syst em in 40 , 500 ft 2 O ffice . . . . . . . 30
9 . HVAC Annual Energy Use in a 40 , 500 ft 2 Offi ce Buildin g by Fuel Type and System Type . . . . . . . . . . . . . . 35
10 . HVAC Annual Energy Use in a 10 0 , 000 ft 2 Hospit al by Fuel Type and Syst em Type . . . • . . . . . . . . . . . 36
1 1 . Monthly Heat in g and Coolin g Ene rgy Demand for Dual Duct Syst em in 40 , 5 00 ft 2 Offi ce . . . . . . . • . 38
12 .
13 .
14 .
15 .
Monthly He ating and Coolin g Energy Demand for Single Zone/ Fan Co i l Syst em in 40 , 500 ft 2 Offi ce . . . . .
Monthly He at in g and Co olin g Energy Demand fo r VAV Syst em in 40 , 50 0 ft 2 Office . . . . . . . . .
Monthly He atin g and Co olin g Energy Demand for Single Zone/ Fan Co il Syst em in 10 0�0 00 ft 2 Hospit al . . . •
Monthly He ating and Cooling Energy Demand fo r Single Zone /VAV Syst em in 10 0 , 000 ft 2 Hospit al . . • . . .
ix
. . . . 39
. . . . 40
4 1
42
X
F I GURE
1 6 . HVAC Energy U s e for En ergy Cons erv at ion Me asures in Dual Duct Sys t em in 4 0, 5 0 0 ft 2 Offic e Bui l d ing with Gas He at
PAGE
and E l ectric Coo l ing . . . . . . . . . . . . . . . 4 7
1 7 . HVAC Ene rgy Us e for En ergy Cons ervat ion Me asures in Dua l Duct � Sin g le Zone/ F an Coi l, and VAV Systems in 40, 5 00 ft Office Bui l ding w ith Gas Heat and E l ect ri c Coo l in g . . . . . . . . • . . . . 4 8
1 8 . HVAC Ene rgy Us e vs . Cap i t al Cos t for Four Fue l Comb inat i ons in 4 0 , 5 0Q_ft 2 O ffic e Bui l ding with Dua l Duct Sys tem . . . . 5 2
19 . HVAC Energy Use vs . Cap i t a l Co s t for Gas He at an d E l ect ri c Coo l ing in O ffice with Dua l Duct . . . . . . . . 5 3
20. HVAC Ene rgy U s e vs . Cap i t a l Cos t for Gas Heat ing and E lect r ic Coo l ing in O ffice with Sing l e Zon e / Fan Co i l 5 4
21. HVAC Ene rgy Use vs . Cap i t a l Cos t for Gas He atin g and Elect ric Coo l ing in O ffice with VAV 5 5
22. HVAC Ene rgy Us e fo r Cons ervat ion Meas ures i n 1 00, 0 00 ft 2
Hospi t al wi th Gas He at and E l ect ric Cool ing . . 5 7
23. HVAC Ene rgy Us e vs . HVAC Cap i t a l Cos t for Gas He at i ng an d E lect ric Coo l in g in Hos pi t a l with Sing le Zon e / Fan Coi l . . . . . . . . . . . . . . . . . . . . . . . 60
24. HVAC Ene rgy Use vs . HVAC Cap i t al Cos t for Gas He at ing an d E lect ric Coo l in g in Hos pi t al wi th Single Zone/ VAV 6 1
DE FINITIONS
ACES -Th e Annua l Cyc l e Ene rgy System is a heat storage system current l y unde r deve lopment by ORNL.
ASHRAE -Ame rican So ciety o f Heatin g, Re frige ratin g and Air-conditioning En gineers .
COP -Coe fficient of Pe rformance is the rat io o f us e ful coo l ing (or he atin g) e ffe ct t o the work in put .
DOE -U.S . Department of Ene rgy .
HVAC -Heatin g, Ventil atin g and Air-conditionin g .
MBH -Thous and Btu pe r hour.
NECAP -NASA's Ene rgy-Co s t Analys is Program is th e comput er program us ed in the ene rgy an alys is of this study .
ORNL-Oak Ridge National Laboratory .
VAV - Variab le air vo lume ductin g system.
xi
I. INTRODUCTION
The purpos e of this study was t o evaluat e the energy and cost
impact s of energy cons ervin g des igns in heat in g, vent ilating, and air
conditionin g (HVAC) syst ems in commerc ia l buil dings . Previous ly de fined
buildin g mode l s which are repre s ent at ive o f the c urrent comme rcial
buil din g stock we re us e d with HVAC systems typical in the se buildin g
type s . The results of this study wil l be used as input t o the commercial
energy mode l1 deve l ope d at Oak Ridge Nat ional Laborat ory (ORNL) .
This sect ion des cribes the restrict ions the ene rgy mode l's
requirement s (s e ct or wide s ignificance ) had on the study . The buil din g
mode l s and weather data used are a l s o des c ribed .
Sect ion II describes the HVAC systems us e d with e ach buil ding mode l
and the ene rgy conservat ion me asures considered. Seve ral opt ions such
as s o l ar heat ing, economizer cyc les, e xh aust air heat recovery, t ot al
energy systems , ACES heat storage systems, and e quipment ·e fficien cy
improvements were an alyz ed.
Se ct ion III des cribes the methods and as sumptions us ed in the ene rgy
analysis o f the HVAC syst ems . The NECAP compute r program was used as
the primary t oo l to de fine annual energy us e . In addit ion, manua l
calculat ions we re made to inc lude measure s not in corporate d in the NECAP
program .
Sect ion IV des cribes the impact o f the energy conservat ion me asures
on annual energy us e and the capit al cos t s of the c onservat ion me asure s .
Savin gs o f as much as 66% were found for s ome systems . Some of the best
1
2
alternat ives had payout s o f less than one year if in corporated in the
original de s ign of the buildin g. The bes t alternat ives for e xisting
buil din gs had s imil ar payouts .
Se ct ion V cont ains the con c lusions of this study and re commendations
for furthe r study . In genera l , the re are s ever al att ract ive conse rvation
measures fo r each buil din g and syst em type wh ich can be made with
favorable payout s .
Commercial Energy Consumpt ion
In 1975 , the commercia l s e ct or c ons umed 9.38 x 101 5 Btu, 13.3% o f
the t ot al energy consume d by the nat ion . A rec ent report us e d in
deve lopment o f the ORNL ene rgy demand mode l 2 s e gre gat e d the commercial
buildin g stock int o t en buil ding type s and deve lope d estimat es o f t ot al
floor space and energy us e for each buil ding type . Result s of that
report show that 7 1% of commercia l energy con s umpt ion was in four
buil ding types -Office , Hos pit al , Ret ail -Wholes ale , an d Educ ation . No
othe r buil din g type acc ounted for more than 7% of t otal energy use .
Space condit ionin g (heat in g and coolin g) is a large percent age of the
-energy us e in e ach of these four buil din g type s and repres ents 65% of
t otal c omme rcia l cons umption .
C l ear ly, energy us e in HVAC systems in the se four commercia l
buil ding types ·is a maj or force in det ermining commercial energy
cons umpt ion. Eva luat ion has been completed on two of the buil din g
types -office an d hos pital -an d is the subj ect of this report .
3
The ene rgy mode l predict s energy us e in the commercial s e ctor of the
Unit ed States in res pons e to e conomic , regulat ory , and t echnical fact ors .
This study de fines the re l at ionship between energy s avings an d capital
costs in comme rcia l HVAC systems for equipment changes . Ene rgy
con s ervat ion me asure s that wou ld be cons ide re d operat ional changes (night
set b ack, chan ges in ventil ation rat es , and lighting re duct ion) and
buildin g enve lope changes (insulation incre ases , and window double
glazin g or siz e re duct ion ) were not cons idered . Both of the se type
opt ions were inve stigated in a study by W. S . Johns on and F. E . Pierce . 3
No att empt at life cyc le costing or other economic evaluat ion (other
than simple pay outs *) was made in the cours e of this study as the
ec onomic method of equipment choice is one of the energy mode l fun ct ions .
The energy mo de l requires that the buil dings mo de le d be "represen-
t ative " of the current building s tock and that the HVAC sys tems mode led
be typical of: (1) syst ems instal led re cent ly, (2 ) th os e inst a l led
current ly, and (3 ) thos e t e chnic a l ly pos s ib l e if there are favorab le
economic or regu l at ory c onditions . In addit ion , s in ce c l imat e has a
maj or e ffe ct on energy consumpt ion in HVAC syst ems , a method must be
us ed wh ich acc ount s for this e ffe ct .
Buildin g Mode ls
The choice of buildin g mode ls to be us e d in this study was made
previous ly in anothe r study by W . S. Johns on an d F . E . Pierce . 3 Their
* Payout pe riod is the time require d for operat ing s avings t o pay
for a capit al c os t impr ovement .
4
results were atso input to the energy model and defined the energy
conservation potentials and costs in the building shell and operating
schedule. A typical office and hospital were defined in detail in their
study and were the basis for this study. Descriptions of the office and
hospital are given in Table 1. These models were chosen to be near the
average of the current building stock and should be good estimates of the
aggregate average energy use. The literal extension of this study's
energy use factors to building sizes other than those analyzed should
be avoided due to the sensitivity of energy use to building size. However,
the extension of the energy use factors on a percentage basis should
yield reasonable results for a large range of building sizes.
Table 1. Building model descriptions
Floor Spac� - ftz
Number of Floors Dimensions - ft Height - ft Roof Area - ft 2
Wall Area - ft2
Window Area - ft2
· Wall "U" Value - Btu/hr- o F-ft2
Roof "U" Value - Btu/hr-o F-ft2
Lighting -Watts per ft2
Occupancy - People Hours/day Days/week
Ventilation Rate - Cubic Feet/Minute
Thermostat Setting -Winter (°F) Sununer (°F)
Office
40,500 Three 90 X 150 36 13,500 12,096 5,184 0. 24 0.14 3 258 9 5
10,000
Hospital
100,000 Four 100 X 250 52 25,000 2 7, 300 9,100 0.24 0.14 3-5 646 24 7
42,000 (Core) 16,200 (Perimeter) 72° 76°
5
The 19 72 ASHRAE Handbook of Fundament al s� was us ed as the b as i s for
the rmos t at s et t in gs an d ven t i l at ion rat e s s ince the majori ty of the
exi s t ing buil din g stock was bu i l t in the p re -emb ar go e ra .
No rma l i z e d Ene rgy Use Factor
The ene rgy mo de l is nat i onal in scop e and requi res that the e ffe ct
of weathe r on ene r gy us e be cons ide red . How eve r , t i me l i mi t at ions
re s t ri ct ed this s tudy to one l oc at i on . In an at t e mpt to compens at e for
the e ffe ct of weathe r on ene rgy use , a "no rma l i z e d " en e rgy use fac to r
was int roduced t o al low extrapo l at i on of re su lts of th i s st udy t o
seve ra l ge o graph i cal are as . The fa ct o r was de fin e d as:
NORMAL I ZED ENE RGY US E ACE + AHE + AOE
=
(DCL * COD) + (DHL * HOD)
wh e re
ACE = Annua l Co o l ing Ene rgy- Btu/ ft 2 ,
AHE = Annual He atin g Ene rgy- Bt u/ ft 2 ,
AOE = Annua l Othe r Ene rgy ( F ans , Cont ro l s ) - Bt u/ ft 2 ,
DCL = Des i gn Coolin g Load - Bt u/ ft 2-Co o l in g De gree D ay ,
COD = Coo l in g De gree Days (bas ed on 6 5 ° F) ,
DHL = De s i gn He at in g Lo ad -. Bt u/ ft 2 -He at in g De gree Day an d
HOD = He at ing Degree Days (bas e d on 65 ° F) .
Annua l ene r gy us e fo r he at in g , coo l ing and fans i s c a l culat e d by NECAP
and is conve rt e d to a square foot b as i s fo r us e in the norma li z e d energy
us e factor . NECAP also cal cul ates the de s i gn h e at ing and c oo l ing l o ads
6
for th e buil din g includin g vent il at i on , l i ght in g, pe opl e an d sol ar lo ads
as appl i c abl e . Loads are conve rt e d to a h eat l o s s (o r gain) pe r s quare
foot and de g re e day bas i s for us e in the no rmal i z e d ene rgy use factor .
Th e n o rmal i z e d energy us e fact or is th e rat io o f th e ene rgy
suppl i e d t o th e h e at in g , cool ing and ai r h andling equipment t o th e ene rgy
act ually demande d to s at is fy space condit ioning lo ads . Th is mi ght b e
con s i de re d th e inve rs e o f th e e ffi c i ency o f a syst e m . For e xample , it
woul d be e xpe ct e d th at an ene rgy e ffi ci ent system will b e abl e t o app roach
1 Btu of ene rgy us e for each Btu o f demand . From th is inve rs e o f
e ffi c i ency , th e ene rgy us e can b e est imat e d b y th e ene rgy model for a
* given geo graph i c al are a i f the de gre e days are kn own .
W e ath e r Dat a
Th e weather d at a used in th is study was an h ourly w eath er t ape for
Kansas City , Mi s s ouri, for 19 55 . K ans as City was ch os en b ecaus e its
h eat in g an d cool ing de gree day s fall n e ar th e ave rage fo r th e n at i on as
a wh ol e . As was th e c as e w ith th e buil dings mo del ed , th e ch of ce o f
we ath e r dat a t o b e us ed was made p reviously i n the Joh n s on and P i e rce
study . De s i gn c onditi ons for K ans as C ity a re 6°F in w int e r ( 46 8 5 heat ing
de gree day s ) an d 9 6°F dry bulb with 74°F wet bulb in summe r ( 1 9 35 cool ing
de gree days ) .
* No analys i s was done t o con fi rm th at th i s method d oe s accurat el y
est i mat e ene rgy us e for di ffe rent areas . How eve r , e st i mat in g ene rgy us e with th e de gree days as a bas i s h as not b een un common an d intuit ively appe ars r e asonabl e . More accurate manual meth ods are avail abl e, but th e i r compl exity an d length excl ude th em from con s i de rat i on in th i s case .
I I . HVAC SYSTEMS AND ENERGY CONSERVATI ON MEASURES
Two criteria were used in sel ect ion of the HVAC sys tems:. ( 1 ) the
energy types current l y in use for heating and coo l ing must be inc luded ,
and (2) sys tems mus t be inc luded which are representative of the r ecent
pas t , the pre sent , and the near future .
Heat ing and Coo l ing Equipment
The energy types cons idered for heating were gas , o i l , and
e l ectric ity . Heat ing equipment for each of these energies was modeled
for both bui l ding type s . Typical effici enc ies were cho sen from
manufacturer's bul l etins and current l iterature . 5 The base ( s t eady
st at e ) e ffic ien cies use d in this report were:
Energy Type
Gas O i l E l ectri c ity
E fficiency
80% 83%
100%
The energy types cons idered for coo l ing were e l ectric ity and gas .
Although district steam i s ava i l ab l e in s evera l c i ties for coo l ing , the
percentage of total commercial f loor space cool ed by this method is not
s igni fi cant national l y . Coo l ing equipment for both energies was modeled
for each bui ld ing type . Single effect absorption chi l l ers were modeled
for gas coo l ing . For e l ectric cool ing equipment , two types of compres sors
were mode led . A reciprocat ing compres sor would be exp ected for smal l er
s i ze s (<200 tons) and was mod e l ed for the office bui lding . A centri fuga l
compres sor wou ld be expect ed for l arger s i zes and was mode l ed for the
hospit a l . These di fferent compres sors were chos en becaus e sma l l er
7
8
coo l ing equipment has predominant ly been reciprocat ing whil e larger
equipment has favored centrifugal compres sors. Sales of coo l ing
equipment were o btained from the Bureau of the Census Current Indus trial
Report s . 6 Sal es for 1975 were typical and are recapped as fo l l ows:
197 5 Sal e s -Chil l ers
Compressor type
5 -50 tons 50-200 tons Over 200 tons
Reciprocating
4 , 000 5 , 000
Centrifugal
2 5 0 7 50
3, 200
C l early the reciprocating compres sor dominates smal l er equipment s al es .
Bas e efficiencie s typical of 197 7 for coo l ing equipment were as fo l l ows:
Reciprocating (E l ectric) C entrifugal (E l ectric) Absorption (Gas F ired)
COP (Bas is ASHRAE 90-75 7)
3.2 3. 8 0 . 65
A load estimat e by the NECAP program for the office and hospital
gave the s izes for the heating and coo l ing equipment as fo l l ows :
Buil ding
Office Ho spital
Heating
160 0 MBH 6800 MBH
Ducting Sys t ems for the Office Building
Coo l ing
130 Tons 500 Tons
Three ducting s ys t ems were analyzed in the office buil ding . One
system is repres entative of the high energy us e sys tems typical when
energy prices were not as high . This sys t em maximizes comfort at the
9
expense of energy use. The two other syst ems are representat ive of
current energy consc ious design and approach energy conservat ion from
two direct ions . One syst em suppli es a const ant volume of air and var ies
temperature in response to load. The other syst em suppli es constant
temperature air and varies the air volume in response to load.
A const ant volume dual duct syst em was taken as the base case in
the office building . The system has excellent comfort control through
prec ise control of temperature and humidity in every zone. The pr ecise
control is gained at a high energy cost by heat ing air to a const ant
temperature in one duc t and cooling air to a const ant temperature in
another. The streams are mixed at each room to meet room condi tions.
Energy use may be as hi gh under "light load" condi tions as under full
load. See Figur e 1 for a schemat ic of the dual duct. Due to its
popularity in the past , it was felt that the dual duct system would be
a prime candidat e for energy conservat ion based on number of inst alla
t ions.
Other popular hi gh energy use systems are the constant volume reheat
system and mult izone syst em . These syst ems have comfort control
ab ilit ies and high energy use similar to the dual duc t. Due to the
similarities of these systems, only the dual duct was analyzed.
The second system analyzed for the office building was the single
zone/ fan coil syst em . This syst em suppli es a const ant volume of air
and varies air temperature to meet the zone lo ad. Separat e duc ting
syst ems are used in the core areas and in the perimeter areas. The
core area is served by a single zone syst em wit h face and by-pass
OUTSIDE I . •
AIR
HEATING COIL
ORNL- OWG 78-9862
MIXING BOX
COOLING COIL r1-l--T1--t-�---l ct � lei) I I I I
EXH!,UST I· t 1... RETURN AIR I ZONE I I ZONE 2 I AIR I L __ , __ _i _____ l __
F igure 1 . Dual duc t sys tem s chemat ic .
,_. 0
1 1
dampers . See F igure 2 for a schematic of the sing l e zone sys t em. In
operat ion , the supply air t emperature respond s to load in two modes .
In the first mode , the thermo stat contro l s the output of the heating
or coo l ing coil directly. The s econd mode is used when dehumidific ation
is needed coincidental ly with low coo l ing loads . In this mode , a
fraction of the air is diverted around the coo l ing coil and the rest
is coo l ed and dehumidified by the coo l ing coil . In this way , there is
no excess coo l ing but some dehumidificat ion is achieved . This mode can
be a comfort disadvantage as energy use rul es over dehumidification. I f
any compromis e is required , humidity contro l suffers . The perimet er
areas are s erved by a four pipe fan coil system as sho wn in Figur e 3.
Fan coil s respond to load changes by modu l ating the flow of chil l ed or
hot water through the coil s . The humidity contro l of this sys tem is at
t imes poor becaus e the thermos tat sys tem fo l l ows the dry bu l b temperature
onl y . N o mechanism is provided for dehumidification a t l o w coo l ing
loads .
The third sys t em analyzed was a variabl e air vo lume (VAV) system
which supplies constant temperature air and varies air suppl y vo lume
in re sponse to load . See Figure 4 for a system s ch ematic . As with
the s ingl e zone/ fan coil sys t em , the humidity contro l is not as precis e
as the dual duct sys tem . Operation at l o w coo l ing l oads resul t s in a
smal l vo lume of cool air suppl ied . This smal l vo lume oft en cannot
provide the dehumidification required . However , coo l ing energy use is
minimiz ed at al l operat ing points as on ly the vo lume of air required to
meet the s ensibl e load is cond it ioned . In an attempt to minimiz e
OUTSIDE ----�·� t----�r-----r--.....f
AIR
RETURN AIR
Fi gure 2. S ingl e zone system schematic .
ORN L DWG 78-9863
--� I I
CORE ZONE I I
L_ __ __ _j
...... N
CHILLED WATER RETURN
CHILLED WATER SUPPLY
AIR
/ OUTSIDE I JJI WALL
I I I I I I I
O R N L DWG 78-9864
PERIMETER ZO NE
HOT WATER RETURN HOT WATER SUPPLY
FAN
Fi gure 3 . Four-p ipe fan co i l sys tem s chemati c .
....... (.N
ORNL DWG 78-9865
SUPPLY AIR TEMPERATURE HELD CONSTANT.
OUTSIDE
_. I I .. , I AIR
EXHAUST
� AIR
SUPPLY
FAN
I I I REHEAT J I I REHEAT
RETURN AIR
· · COIL
--, I (T
ZONE , I I
------,,.- - .1_ - -
NOTE: PERIMETER ZONES HAVE HYDRONIC BASEBOARD HEATING.
F i gure 4 . Variab l e air vo lume (VAV) sys tem schemat ic .
COIL
-,---1
ZONE 2 I I
_ _L __
....... �
15
heat ing energy use , hydron ic (hot wat er ) base board heat ing in the
perimet er areas was incorporated as the primary heat source rather than
reheat on the supply air. This measure was taken to use the variable
volume syst em to its best advantage. If reheat had been used as the
primary heat source , during the heat ing season air would be cooled at
the central unit and then heated at each perimeter zone. This situat ion
will result in exc essive heat ing energy use.
Ducting Syst ems for the Hospit al
Two duct ing systems were analyzed in the hospital. The systems
analyzed did not offer as much conservat ion potent ial in themselves as
the syst ems modeled in the office building. This re sult was primar ily
due to the fact that hospitals have historically been such large energy
users that energy conservation has to some ext ent been incorporated in
the orig inal desi gn. There are several factors which contr ibut e to
hospitals ' high energy use: ( 1 ) maj or areas require extremely hi gh
rates of vent ilat ion, ( 2 ) most of the hospital is occupied 24 hours a
day, (3) apprec iable areas ar e used for food preparat ion and laundry
facilities which are large HVAC energy users , and (4) closer control
of condi ti ons is required in several areas.
A constant volume single zone syst em with face and bypass dampers
was chosen for the core area operat ing rooms, laundry and cafeteria .
This syst em was chosen for these ar eas because they require 100% fresh
air and this syst em has low energy use for large fresh air volumes.
Wi th 100% fresh air used in this syst em, most of the humidity control
16
prob l ems are avoided because the out s ide air humidity i s norma l l y l ow
when amb ient t emperatures cause low coo l ing loads . This core HVAC
sys tem was used with the two per ime ter duct ing syst ems modeled .
The first per imeter system analyzed used four pipe fan coi l s to
s erve the adminis trat ive offices and pat ient rooms . The s econd perimeter
syst em analyzed was a VAV sys tem . Sinc e both systems are s imi lar to
those mod e l ed in the o ffice bui ldin g, they are not described again .
Energy Cons ervat ion Measure s
The energy conservat ion options cons idered for both bui lding types
covered two areas - air s ide cons ervat ion (attempting to reduce energy
use by reduc ing l oad s seen by sys tem) and heating/ coo l ing equipment
cons ervation . The air s ide cons ervat ion measures cons idered inc lude
economizer cycl e s , reset contro l s (dual duct only) , and exhaust air
heat recovery with the duc t ing systems described earl ier . The heating/
coo l ing opt ions cons idered inc lude improved equipment effi cienc y , doub l e
bundl e exchangers , partia l solar heat ing , a heat s torage system , and
a tota l energy syst em (ons ite e l ectri city generation with waste heat
recovery) . Electric air to air heat pumps were not considered b ecause
of the l ack of equipment in the commercial (>50 tons) s i ze range .
A short description of the energy cons ervat ion measures fo l l ows .
Economi zer cyc l e . An economi z er cyc l e was added to lower coo l ing
energy use . The economi zer cyc l e uses out s ide air for "free" cool ing
when the ambient temperature i s l ower than the return air t emperature .
Thi s cyc l e cons erves energy when there are cor e areas which require
17
coo l ing year round . Two economi zer cyc l es wer e mode l ed . One system
s enses amb i ent temperature only and the other s enses enthalpy . The
enthal py sens ing economi zer offers the add ed advantage of responding to
both s ensib l e and l at ent heat (or ambi ent enthal py) . In areas with
high humidity at night , the entha l py s ensor prevent s the use of high
humidity air whi ch wil l requ ire more coo l ing than the return air . The
app l ication of this cyc l e to the hospital core areas would be inappro -
priat e as they r equire 100% outside air . In addition , the appl ication
of thi s cyc l e to a fan coi l i s unl ike ly , as each fan coi l would require
its own inl et , motori zed damper , and contro l s .
Exhaust air heat recovery . Exhaust air heat recovery rec l aims
heat from the exhaus t air and supp l i e s this heat to the fresh air
brought in for vent i l at ion . In the winter , the fre sh air i s heated and
in the summer , the vent i l at ion a ir i s precooled .
Two types o f exhaust air heat recovery wer e mod e l ed . The fir s t
i s a s ens ib l e heat only heat exchanger . S ens i b l e only exchangers can
s egregat e the two air s treams comp lete l y and are the type cons idered
for the hospi tal becaus e of hea l th reasons . Typical s ens ib l e only heat
exchangers are flat p late, heat p ipe , run around and rotary exchangers .
The range of e ffectiveness expected i s from 40% to 80% , with
effect iveness defined as
18
where
T1 = temperature of out side air entering exchanger,
T2 = temperature of outside air leaving exchanger, and
T3 = temperature of exhaust air entering exchanger.
An effectiveness of 70% was used in modelin g the sensib le only
exchanger. See Figure 5 for a schematic of the exchanger with typical
winter temperatures shown. The second exchanger modeled was a latent
and sensible or enthalpy heat exchanger. Since this type exchanger
allows cross cont act of the two air streams, it was not considered for
the hospital. Typical of this type are the hygroscopic rotary and
multiple tower dessicant type exchangers. Expect ed effectiveness would
be in the range of 5 5 - 7 0% , with effectiveness defined as
where
X1 = enthalpy of out side air entering exchanger,
X2 = enthalpy of out side air leaving exchanger, and
X3 = enthalpy of exhaust air entering exchanger.
An effectiveness of 60% was used in modeling the enthalpy heat exchanger
in the office building.
The addition of exhaust air heat recovery in the original design
can be an advantage. With heat recovery, the heating and cooling
equipment sizes are smaller due to the reduced design heating and
cooling loads.
OUTSIDE AIR -.. T = 42 ° F I
HEAT EXCHANGER
- .--T4 = 51.9°F
..
! =
.. T2 = 65.1° F -
EXHAUST AIR T3 = 75°F
( T1 - T 2) (T1 -T3)
""'I' ,.v
< ,;" '
...... �-' ""'r-.
v ( r--
ORNL DWG 78-9866
...-- ..--
-... � -
....__ -HEATING COOLING
· COIL COIL I\ I\ I \ I \
( 75 ° F)
RETURN --AIR DU CT (75
Fi gure 5. Schemat ic of exhaust air heat re covery exchanger- s ensib l e type, with typical wint er temperature s shown .
0 )
....... �
20
Re s et contro l s . Res et contro l of the temperature of the air
supplied was an opt ion ana lyzed for the dua l duct system on ly . The s e
contro l s periodical l y re s et the hot air temperature to j ust meet the
l argest heating demand and res et the cold air temperature to j ust meet
the largest coo l ing demand . To a l arge degree , this e l iminat ed the high
energy use of the dual duct at "l ight-l oad" conditions . This option was
not considered for the s ing l e zone/ fan coil sys tem becaus e that system
incorporated this contro l original l y . The VAV achieved the s ame effect
by varying the supply air volume whil e ho l ding temperature constant .
Improved equipment efficiencie s. Chil l er efficiencies were improved
by increasing heat transfer areas and by improving compre ssor efficiency.
The s e improvements were combined in three cas e s which were repres entat ive
of chil l er efficiencies avail ab l e in the recent past , the pres ent and
the near future . The efficiencies used for the present and future cas es
are those given in ASHRAE Standard 90-7 5 for 197 7 and 1980:
Case
Recent Past Pres ent (1977) Near Future (1980)
Chil l er E fficiency (COP)
Reciprocating
2 .9 3. 2 3 . 4
C entrifugal
3. 4 3.8 4 . 0
The recent past case s hould be repres entative of the maj ority of
machines current ly in use . The pres ent case should be representative
of the chil lers current ly being instal l ed . The future case s hou ld be
representative of the improvement in effic iency that wil l be on the
2 1
market in 1980 . �1ajor improvement s in efficiency beyond the 1980 case
are not expected un l e s s a major breakt hrough in chil l er design is made.
Heating equipment efficiency improvement through the addit ion of
economiz ers or combustion air preheaters was not modeled . Although
common in industrial app l ications , very fe w boil ers (in building s ervice)
have been instal l ed wit h these heat recovery devices . There are t wo
reas ons for their being omitted . The first is the low ut il ization of
the s e devices due to the l oad variations norma l in building service .
Very l ong payout s (%2 0 years) can be expected for this cas e. The s econd
reason is the l o w l oading that is common to buil ding s ervice wil l cause
either heat recovery device to operate be low the flue gas dew point .
Operat ion bel o w the dew point can caus e corro s ion severe enough to
drastical l y shorten the heat recovery device l ife .
Doubl e bundl e exchangers . The addit ion of a doubl e bund l e exchanger
to the chil l ers al lows the heat normal ly reject ed to the atmo s phere by
the chil l ers t o be appl ied to the heat ing load . See Figure 6 for
schematics of a chil l er with and without doubl e bundl e exchang er. The
"doubl e bundl e" refers to the two conden?ers , one to supp l y heat ed water
to the heating sys tem and the other to reject excess heat to the
atmosphere through the coo l ing tower . Typica l l y, heat ed water wou ld
be supp l ied at 105°F , making it suitabl e for us e at the heating coil
but unsuitabl e for bas e board heating .
Solar heating . A flat p l ate co l lector water bas ed s o l ar heating
system was mode l ed . A non s e l ective doubl e-gl azed co l l ector was u s ed
CHILLED WATER
RETURN (54°)
CHILLED WATER
SUPPLY (44°)
EXPANSION
EVAPORATOR VA LV E
CONDENSER
ORNL-OWG 78-9867
HEAT REJECTED TO
COOLING TOW ER
HE AT SUPPLIED TO HEATING
SYSTEM
CHILLER WITH DOUBLE BUNDLE E XCHANGER
EX PANS
CHILLED WATER
EVAP ORATOR VALV�ON
RE TURN (54o)
CHILLED WATER
SUPPLY (44°) COMPRESSOR
HEAT REJECTED TO
COOLING TOWER
CHILLER WITHOUT DOUBLE BUNDLE EXCHANGER
Figure 6 . Schemat ics of ch i l l ers wi th and wi thout doub le bund le exchangers .
N N
2 3
to co l le ct so lar energy . The system was de signed t o supp ly heate d wate r
to the heating syst em a t 115°F , making it s uitabl e f o r us e a t t h e heating
coil but not for bas eboard heat ing . Col l e ct o r area for the o ffice was
50 00 s quare feet and a storage capacity o f 10 , 000 ga l l ons was as sumed.
Col l ecto r are a for the hos pit al was 10 , 000 s quare feet with a stora ge
capacity of 2 0 , 00 0 ga l l ons . Th e sys tems were s ize d t o s upp lement the
exist in g heat in g system rather than to be th e s o l e h eat ing source . The
systems are es timated to provide 15-30% o f h eat ing re quirement s . In
addition , the col l ectors were as sumed t o face due s outh and t o have a
fixe d t ilt .
ACES system . ACES is the acronym for th e Annua l Cycle Energy
System current ly unde r de ve l opment by ORNL. ACES was inc lude d in this
study to provide some insight into the minimum achievable ene rgy us e.
The sys tem is s til l under de ve l opment and no comme rcial buil ding s ystems
are in us e t oday (demons tration p roje ct s have begun) . The ACES has the
ability to s ignificant ly re duce annual HVAC ene rgy use .
ACES is a heat s torage system which s eek s t o lower ene rgy us e by
balancing the buil ding h eating and c oo l ing loads o ver an annua l cyc le .
During the winte r, a heat pump op erates t o h eat the buil ding . The heat
pump's source of he at is the wat er s torage which is gradual l y t urned to
ic e in the cours e of the winte r . During th e summer , the ice is us ed
direct l y to coo l the buil din g . I n es sen ce , t h e ene rgy us ed to heat the
buil din g is ut il ized again t o coo l it when the ice is me lte d . See
Figure 7 for a s chematic o f the sys tem.
COOLING COIL
·�
,.... .....
.._,..... �·
-.....L:"
T HEATING
COIL
� w ten >en u <{ > :X:
I I I I I I
CHILLED WATER RETURN
HOT WATER TO HVAC SYSTEM
� �
...
--... �
HEAT PUMP
�-
ORNL OWG 78-9868
...
,, � ......
INSULATED I __ ___ ___. -- ---'-- --- ---' I I I I
ICE/WATER
c
G CHILLED WATER -TO HVAC SYSTEM --
Figure 7 . Sch ematic of ACES system.
STORAGE
N �
2 5
For th e ideal AC ES appli cation , th e annual h eat ing and cool ing loads
would balance . I n real ity , th i s cas e can onl y be appro ach ed , so an
aux il iary means of mak ing /melt ing ice must be provided to equal i z e th e
year to year imbal ance . I n th e South , wh ere cool ing loads predominat e ,
an out s ide conden ser coil for th e heat pump to mak e add ed ice would b e
included. I n th e North , wh ere heat ing l oads predominat e , a sol ar
coll ect ion system to melt exc es s ice would be exp e ct ed . By v irtue of
th e ic e storage of th e syst em , both o f the s e aux il i ary mean s o f h eat ing/
cool ing could operate mor e effici entl y th an would normall y be th e case .
For extra cool i ng , th e heat pump could be operated at n ight at cool er
amb i ent t emperatures . For extra h eat ing , th e sol ar coll ectors would b e
u s e d to melt exc e s s ice and could coll ect energy at clo s e to 32° with
very h igh coll e ct or effici ency .
Th is ACES suppl i ed h eat ed wat er at 1 0 5° wh ich i s suitabl e for
heat ing co il use but unsuitabl e for bas e bo ard h eating . Th i s did not
all ow th i s ACES to be us ed with th e VAV syst em anal y zed in th i s study .
However , ACES can b e des igned to supply energy at virtually any
t emp erature us eabl e in HVAC syst ems . Some penalty in COP i s incurred
as supply t emperature increas es .
Total energy syst em . A total energy syst em with d i e s el driven
ele ctric generators and wast e h eat recovery was mod el e d . Th e generators
wer e s i z ed and op erated t o provide all build ing el ectricity . Wa st e heat
avail abl e from el ectricity generat ion wa s recovered to prov ide e ith er
d irect h eat ing or cool ing through ab sorpt ion ch ill ers . Aux il iary boil ers
26
were included to supply the heat requi re d in excess of that available
from the en gine generators. In the past, the use of these systems has
been limited bec ause o f high capital cost s, reli ab ility prob lems, and
in creased operat in g st aff requi rements. Tot al energy systems are
currently avai lable whi ch can inst ant aneously convert 70 -80% o f the
higher heat ing value o f input fuel to elect ricity and useful heat .
Cumulat ive system effi cien cy may be lower due to the mi smat ching of
elect ric al and the rmal load pro files. Economies of sc ale favor large r
generators (>500 Kw) , however, small ( 100 _Kw) generators are availab le.
I I I . ENERGY USE ANALYS IS
Comput er Simul ation
NASA's Energy and Cost Analysis Program (NECAP)8 computer program
was used to ana lyze the annual energy use of each of the HVAC sys tems
mode l ed . The program calculates buil ding thermal loads and resul ting
HVAC sys tem performanc e on·an hour ly bas is and sums energy use on an
annua l basis. The program has found widespread acceptance as one o f
s evera l repres entative HVAC energy model ing programs . NECAP o ffers
numerous opt ions for heat ing/coo l ing equipment and for duct in g syst ems .
Where pos s ible , the s e options were us ed in t his ana lysis . In some cas e s ,
the program did not offer the capabil ity required and manual estimat ions
were made .
The NECAP program performs a detail ed hour-by-hour ana lysis of the
annual energy use of a particul ar HVAC sys t em . I n the interest of time
and money , one maj or simp l ifying assumpt ion was made in the devel opment
of the buil ding model s . Since the run t ime of the program is direct ly
proportional to the number of zones specified for the building mode l ,
both building models were divided into on ly five zones . Four were
p erimeter zones and one was a core zone . Each zone extended the height
of t he buil ding . The zone furnis hings ' weight was increased to compens at e
for the thermal inertia of the int ervening fl oors . The error introduced
through this s impl ification would be expected to be consistent across
the various opt ions cons idered and should not be s ignificant as heat
trans fer through thes e floors shou ld be sma l l .
27
28
E ach HVAC system was mode l ed and run for a ye ar in the p ro gram t o
obtain annual en e rgy us e . The he at ing and coo l in g fue l types were varied
t o obt ain energy use dat a for four fue l comb inat i ons in each HVAC system .
E l e ct ri c heat with gas coo l ing and oil he at with g as coo l in g we re
con s i dere d un l ike ly comb inat i ons and were ignore d .
Manual Calcu l at ions
Manual c a l culat ions were require d to supp lement the NECAP s imu l at i ons
in several cases : (a) s o l ar heat in g, (b) doub le bundl e exchangers ,
(c) exh aust ai r he at re covery , (d) variat i on in ch i l ler e ffic ienci e s ,
(e ) vari at i on in boi ler e fficiencies due t o fue l type , an d ( f) ACES he at
storage syst em . A short des cript i on of each calcu l at ion method fo l lows ,
and s amp l e ca lculat i ons are in Appendix A.
So lar heat in g . The s o lar heat ing syst em was s imul at e d us ing the
ERDA Fac i l it ie s So lar Des i gn Manua l . 9 From loc al s olar dat a, bui l din g
loads ( from NECAP) , and c o l lect or s iz e , system pe rformance on a monthly
and annual b as i s was pre di ct e d . The s o l ar dat a , bui l ding l oads , an d
co l lector si ze were combined on a month ly bas is t o make a rat io o f s o lar
ene rgy avai l ab l e t o bui l din g load . With this ratio , a chart was ent e red
whi ch gave a monthl y fract i on of h eat ing load met . Th e monthly heat ing
loads met were comb ine d to estimat e the tot al h eat ing avai l ab l e fo r the
year . This method was also deve l oped us ing the NECAP pro gram w ith a
s impl i fie d bui l ding mode l comb ined with expe riment al pe rformance data
fo r sol ar co l l ect o rs . 9
29
Doub l e bundle exchangers . The performance of the doub l e bundle
exchan ger was avai l ab l e in the NECAP program as part of an ene rgy
conservation sys tem . However, th e program di d not a l l ow evaluat ion o f
exchan ge r pe rformance alone . A s imp l e manual method was us ed t o est imat e
doub l e bund le exchan ge r pe rforman ce .
The doub l e bundle exchange r applies th e h eat re j ect e d by the
chi l l er to the h eat ing load (when pos s ib l e ) . Heat re j ected is the
coo l in g load p l us the ene rgy adde d by th e comp re s so r . Th is ene rgy mus t
be us ed immedi at e ly unl ess some thermal storage has b een provide d .
Therma l sto rage was not in clude d in th is option , but a thermal sto rage
system was mode le d with the ACES s ystem . The ene rgy us eful for heat ing
at any given t ime would be limited to either th e h eat ing or coo l in g
lo ad, whi chever is smal l e r . In other words , th e us e ful energy during
summer months would be limi ted to the sma l l h eat ing l o ads typi ca l o f
this s eason and the us eful ene rgy during winter month s woul d b e limited
to the sma l l coo l ing l o ads typical of this seas on . Th e us e ful ene rgy
for he at ing on an annual bas is would b e a summat i on o f thes e us e ful
ene rgie s . See Figure 8 for a graphi cal rep res ent at i on o f annual us eful
en ergy . The metho d us ed to est imat e the annual us e ful ene rgy for heat ing
was to sum the month ly minimum of the heat ing and cool ing loads . Some
correct i on was made to the fa l l and spring months t o a l l ow for the fact
that heat in g loads would pe ak at ni ght and coo l ing lo ads woul d peak
durin g the day wi th neithe r cumu l at ive load b eing indi cat ive o f the
monthly tot al us e fu l h e at . The correct i on was bas ed on the examin ati on
of typi cal fal l and sprin g days which gave an estimate o f the us e ful heat .
900
; 8 00 CD CD 0
� 700 z 0 �
' V) ..J 600 0 0
� 0 500 z <( � w 0 >- 4 00 C) a: w z w
C) 300 z ..J 0 0 0
200
1 00
0
· £:. H E AT I N G
0 COO L I N G
c H E AT REJ ECTED FROM COOL I N G EQU I P M E NT
30
t27//ZJ1 US E A BLE H E ATING
J
ENERGY
F M A M J
M O N T H
J
O R N L OWG 7 8 - 9 8 7 7
A S 0 N D
Figure 8 . Month ly e11e rgy avai lab l e from doub le bund le exchanger in dual duct sys tem in 40 , 500 ft 2 o ffice .
31
Exhaust air heat recovery. . Exhaust air heat recovery o f both
sensib le and entha lpy types were simulated with manual calculations.
The performance was approximat ed usin g a temperat ure bin method
suggested by Bowen. 1 0 The performance of the heat recovery equipment
was calcu l ated for each 5 ° temperat ure bin and summed on an annua l basis
weighed by the hours o f occurrence of each bin. Hours of occurrence
were from the Air Fo rce. 1 1
Chil ler efficiencies. The effect on energy use of variations in
chil l er efficiencies was ca lcul ated manua l l y. The equipment chan ges to
the chil lers to achieve the efficiency improvements were assumed
evol utionary , bein g increases in heat t ransfer surfaces and compresso r
efficiency improvements. The basic chil ler performance curve did not
change in shape but the COP increased by a const ant percent age across
the curve , al l owin g the use o f a simp le ratio to approximate the
differen ce in annua l energy use.
Boiler efficiencies . The effect of fuel type on boiler efficiency
and annual energy use was ca lculated manual ly. The NECAP program
assumes 80% efficiency for both oil and gas heatin g equipment. No
correction was required for the gas heatin g equipment . The oil heatin g
consumption predicted by NECAP was co rrected b y the rat io o f 80 /83.
Firetube boilers are typical ly used in building heating service. The
efficiency of these type boil ers remains essentia l l y const ant from rated
conditions down to 20 - 30% of rated lo ad. Al so , modul ating burne rs wil l
typical ly b e used. These burners foll ow the heating load closel y and
32
allow approximately const ant steady st ate operation rather than on -off
cycling . Since the boilers studied in this report have a dynamic
efficien cy which approaches the rated steady st ate efficien cy, no
co rrection to rated efficiency such as a seasonal performance fact or
was made .
ACES Syst em
The performance of the ACES system was estimated usin g heat pump
performance as given by the system originat or in literature . 1 2 Since
the heat pump operates between fixed temperatures, the COP should remain
constant throughout the yea r . Heating energy use was estimated using
a constant COP of 3 . 5 . Energy use for coolin g was that required to pump the
cold water from t he sto rage bin to the coil and back . Tot al ice buildup
was estimated by summin g net monthly loads . Bin heat gain was assumed
t o be 3% of the bin sto rage for the month. The storage volume was
estimated usin g the ratio of ice t o water in the bin that was used in a
current commercial buildin g ACE S demonst ration pro j ect . 1 3 See Appendix
A for a sample calculation .
IV. ENERGY USE IMPACTS, CAPITAL COSTS, AND PAYOUTS
The energy impacts of the conservation measures were analyzed as
outlined in the previous sections. The capit al costs were estimated
using cost estimating manuals 1 � - 1 7 and manufacturers ' estimates. Where
possible, the cost estimating manuals were used to arrive at estimates
that would have market wide significance. These estimating manuals are
based on historical building costs and are often used as the basis for
conceptual estimates. Their value lies in their ability to provide a
reasonable basis for comparison by the builder of several alternatives
at the conceptual design stage without requiring detailed design and
cost analysis.
The capital cost of a particular energy conservation measure may
differ when considered as an original design option and when considered
as a retro fit option. For instance, the addition of a double bundle
exchanger at the design st age will only cost 6 5 % as much as a retro fit
application . The increased cost of the retro fit is due to the higher
field installation cost ; a double bundle exchanger included at the
design stage is largely factory installed.
Payouts estimated were simple payouts. No attempt was made at life
cycle costing or other economic evaluation. Capital costs were estimated
fo r 1 9 76 and payouts we re calculated usin g typical energy costs
for that year, as shown below. 1 8
33
E l ect ricity Gas Oi l
34
1 9 76 Typi cal Uti l ity Cos ts ( In 19 75 -$ )
$9 . 09/ 1 0 6 Btu ( 3 . 1 ¢/kwh) $ 1 . 38 / 1 0 6 Btu $2 . 4 1 / 1 0 6 Btu
Energy Use Versus Fue l Comb inat i on
A summary o f energy us e by fue l combin at ion in the o ffi ce bui l din g
us ing a dua l duct system i s given in Tab le 2 . Simi l ar ene rgy us e t ab le s
were obt ained for t h e other duct in g syst ems mo de led and are shown
graph ical ly in Figures 9 and 10 . See Appen dix B fo r a mo re comp lete
list ing . Throughout thi s report , ene rgy is convert e d on a p rimary (or
as mined) b as is . The conve rs ion fact or fo r e le ct ri city i s 1 1 , 500 Btu
per ki l owat t -hour de livere d . This fact or in c ludes powe r p l ant generat ion
and t ransmis s i on los ses . No c onve rs i on fact ors we re app lied to gas and
oi l .
Tab le 2 . HVAC ene rgy use for a dua l duct system in a typ i cal office bui lding by fue l type
He at ing/Cool ing Fue l
Gas / E lect ri c Oi l / E l ectric E le ct ri c/E l ectric Gas / Gas
Annual Energy Us e (Btu/ ft 2 -yr)
32 6 , 000 320 , 000 59 7 , 000 449 , 000
No rma l i z e d Energy Us e
2 . 3 1 2 . 26 4 . 2 2 3 . 1 7
The difference s found in energy us e due to the duct ing con figurat ion
we re s igni ficant in the o ffice bui l din g an d minor in the hospita l . For
examp le , in the o ffice bui lding , the di ffe rence between the dual duct an d
the variab le vo lume syst ems was almost SO% , whe reas the di ffe ren ce in
the hospit a l duct ing systems was less than 5% . A summary o f energy
0" '< 1-1') c:: (t) 'T.I ....... �·
OQ M C:: '< 1-i '"d (t) (t) I.O 0 � o.. :I: Ul < 0 '< ::> Ul n c
)> ("'t (t) p:l r 3 ::s
0 ::s M C c '< p:l
() '"d ..... -t (t) (t) ::s (t) 1-i
OQ '< CJ) c:: "Tl z Ul )> G) (t)
z r fTI �·
() N ::s p:l Q o
r z � rn 0
' .. U1 0 0 1-1') ("'t
N
0 1-1')
< 1-1') �· )> (') < (t) 0" c �· ....... 0. �· ::s
OQ
HVAC ANNUAL EN E RGY USE ( BTU / FT 2 )
0 1\) "" � (JI 0 0 0 0
0 p 0 p _o b 0 b 0 0 0 0 0 0 0 0 0 0 0 0
GAS HEAT / ELECTRIC COOLI NG J OIL I ELECTRIC I
ELECT RIC/ ELECTRIC
GAS/ GAS I GAS/ELECTRIC J OIL /ELECT R IC 1
ELECTR IC / ELECT R IC J GAS / GAS J
GAS / ELECT R I C 1 OIL / E LECT R IC l
ELECT RIC I ELECTRIC I GAS / GAS J
0) 0
_o 0 0 0
I
0 %1 z r-0 � (i)
� (J) I
cD (J) en U)
t.N U1
800,000 -
700,000 -
600,000 -
w C/) :::>
500,000 >--
(!) 0::: w -Z N w �
LL 400,000 _J ' � :::> => t-Z m z -
�
� () 300,000 � � > :I:
200,000 f-
100,000 f-
0 .
36
!""--
-
......-�
(!) z -_J 0 0 () () 0::: () .,_ 0::: () .,_ w () () _J 0::: w w .,_ _J C/) ....... () w � ....... .,_ w () (!) <X _J 0: ....... w w C/) :I: ....... .,_ <X
_J () (!) C/) LLJ <X 0 _J (!) LLJ
SINGLE ZONE I FANCOIL
O R N L OWG 78 - 9 8 70
-
�
,.....--�
() 0::: .,_ ()
() () w - - _J 0::: 0::: w C/) .,_ .,_ .......
<X () (!) () () w ....... w _J _J 0::: C/) w w .,_ <X ....... ....... () (!) C/) _J w <X _J (!) 0 LLJ
SINGLE ZON E / VAV
Fi gure 10 . HVAC annua l ene rgy use in a 100 , 0 00 ft 2 hosp it al by fue l type and sys tem type .
3 7
use by bui lding and ducting system types is given in Table 3 . To
further il lustrate the differences in energy use due so lely to the
ducting system, the monthly heating and cooling demands at the coils
for the five HVAC systems modeled are shown in Figures 1 1 through 15 .
Tab le 3. HVAC annua l energy use by ducting system and building type for gas heating and e lectric cooling
Annual Energy Use
Norma lized Building Type Ducting System Btu/Sq . Ft. Energy Use
Office Dua l Duct 326 ' 000 2 . 3 1 Office Fan coil & Single Zone 2 1 1 , 000 1 . 49 Office Variab le Volume 1 84 , 000 1.30 Hospital Fancoil & Single Zone 423 ,000 1 . 8 1 Hospital Variab le Volume
& Sing le Zone 408 , 000 1 . 75
Office Building HVAC Energy Use
Economizer cycle. Surprisingly, addition of the economizer cycle
increased tota l energy use in al l the systems analyzed because heating
energy use increased more than coo ling energy use decreased . This was
because the cycle contro ls attempted to meet the system cold air
temperature even when ful l heating was required . If the economizer
contro ls were improved with a feedback circuit to provide coo ling on ly
when cooling was the predominant load, it is expected that tota l energy
use would decrease . The NECAP program did not a l low the ana lysis of
this improvement. However, it is estimated that the improved economizer
800
X .,_ z 0 700 � ...... (/) _, 0 0 f- 600 c:l 0 z c:l � 500 w 0 >- ::> (!) .,_ a:: CD w Z U) w 0 400 (!) z :J 0 0 300 0 0 z c:l (!) z 200 .,_ c:l w X
100
H E AT ING ---6--COOL ING --<>---
' J F M A
3 8
M J MONTH
ORNL OWG 78 - 9 872
J A s 0 N D
Figure 1 1 . Monthl y heat ing and cool ing ene rgy demand fo r dual duct system in 4 0 , 5 0 0 ft 2 office .
80 0
:t: t-z 700 0 � ' en ..J 0 600 0
t-<t 0 z <t 500 � w 0 :::> >- t-<!) m
a:: U> 400 w 0 z -w <!) z ..J 300 0 0 0 0 z <t <!) 200 z t-<t w :t:
100
0
H E AT I N G --6-COO L I N G -o--
F M A M
39
J
MON T H
J A s
O R N L OWG 7 8 - 9 8 7 3
0 N D
Fi gure 12 . Monthly he at ing and coo l ing energy demand for sing l e zone/ fan coi l system i n 40 , 500 ft 2 offi ce .
:X: ... z 0 � ' (J) _J 0 u
... �
0 z � � w 0
>-:::» (.!)
a: t-w til z
CDO w
(.!) z _J 0 0 u
0 z �
(9 z t-� w :X:
800
700
600
500
400
300
200
1 00
t
0
J
40
O R N L OWG 7 8 - 9 8 7 4
F M A M J J A s 0 N D
MO N T H
Figure 1 3 . Monthly heating and cooling energy demand for VAV system in 40, 500 ft2 office .
:I: t-z 0 � ...... (/) _J 0 (.) t-c:t 0 z c:t � � t-LIJ (D 0 � w (!) Q a: LIJ z LIJ (!) z _J 0 0 (.) 0 z c:t (!) z t-<t w :I:
3,000
2,000
1 ,000
0 J F M A
4 1
M J J MONT H
A s
O R N L OWG 7 8 - 9 8 75
0 N D
Fi gure 14 . Month ly he at ing an d coo l ing ene rgy demand for s ing l e zone/ fan c o i l sys tem i n 1 0 0 , 000 ft 2 hospit al .
:X: � z 0 � 3 , 0 00 ...... C/) ...J 0 0 � <( 0 z <( � w 0 2 ,000 >- :;) (!) � 0:: CD w z
<Do w "'-!" (!) z
...J 0 0 0 0 1 , 0 0 0 z <( (!) z � <( w :I:
0
� o--o
J F M A
42
HEA T I NG
COOLING
M J J MONT H
O R N L OWG 78 - 9 8 76
A s 0 N D
F i gure 15 . Month ly heating and coo l ing ene rgy demand fo r s i ng l e zone/VAV sy stem in 100 , 000 ft2 hospital .
43
cycle could approach the cooling savings predicted by NECAP with no
penalty in heat in g. Therefore , coolin g energy savin gs for the three
HVAC syst ems would be
1-NAC System
Dual Duct Sin gle Zone/ F an Coil VAV
Coolin g Energy Savings
3 . 6% 0 . 8%
1 1 . 9 %
Tot al Energy
Savin gs
1 . 3 % 0 . 3 % 4 . 5 %
As expected, the VAV system which cools all the air year roun d , showed
the largest decrease . Two economizer cycle sensing modes - enthalpy
and temperature - were modele d . The di fferen ce in tot al energy use
of the two was minimal, never mo re than 0 . 7% of t ot al energy use .
Exhaust air heat recovery . This opt i on resulted in energy savin gs
for the dual duct and sin gle z one/ fan coil systems o f 4 . 9 % and 6 . 5 %
respectively. The primary savings were in heating energy use with li ttle
effect on cooling energy use . Exhaust ai r heat recovery with the VAV
system increased energy use . For the dua l duct and single z one/ fan coil
syst ems the in creased temperatures from the heat recovery exchanger
helped reduce the heatin g lo ad. Fo r the VAV system , the highe r tempera-
tures negated much of the " free " coolin g available in wint er an d increased
coolin g energy . use .
Reset cont rols (dual duct only) . The addition o f imp roved c ont rols
in the dual duct system result ed in a signi ficant energy savings o f
2 7 . 0 % . The cont rols decreased energy use o f the system under "light
44
lo ad" conditions by decreasin g the hot and cold deck t emperat ure
difference . Coo ling energy use was reduced 42 . 2% , while heatin g energy
use was reduced 21 . 2 % .
Improved chiller efficiency. Imp rovin g the chiller efficiency from
present to expect ed 1980 efficiencies reduced energy use in all cases.
The reduction varied from 1 . 2 % for the single z one/ fan coil system t o
2 . 2 % for the dual duct system . As other energy conservation options
were combined with imp roved chiller efficiency, the total energy savings
due to efficiency improvement decreased, but the percentage reduction
of coolin g ene rgy use remained constant. Comparison o f past chiller
efficiencies with present ones, sho wed the past efficiency case consumin g
3 . 9 % more energy in the dual duct system.· For the sin gle z one/ fan coil
and the VAV systems, the past efficiency case consumed 2 . 2 % and 2 . 7%
mo re energy. (Because o f the small chan ge in energy use due t o the
increase in chi ller efficiency, these points were not shown on the
graphs that foll ow . )
Double bundle exchan gers. Double bundle · exchangers reduced energy
use in all the systems as shown below.
HVAC System
Dual Duct Sin gle Zone/ Fan Coil VAV
Heating Energy Savings
49 . 2 % 7 . 3 %
2 1 . 3%
Tot al Energy
Savings
26 . 8% 3 . 9 %
1 1 . 5 %
45
Reexamin ation of Figures 11 , 12 , and 13 (p ages 3 8 -40 ) , in light of
the useab le energy fo r heatin g as shown in Fi gure 8 (page 30) , gives
some insight into the di fferences in heatin g energy s aved . The dua l
duct has the largest area under the curves whi le the sin gle zone/ fan
coi l has the smal l est .
So l ar heat in g . So l ar heat reduced the heatin g energy use in the
three systems by 1 3 . 4 % to 20 . 0% and tot a l energy us e by 6 . 9% to 10 . 5 % .
The systems with larger summer heatin g loads showed l arger reductions.
ACES system . The ACES system showed the largest potential for
energy savin gs of the conservation measures analyzed. When used
with exhaust air heat recovery in the dual duct and sin gle zone/ fan coil
systems, reductions in energy use o f 64 . 9 % and 66 . 2% were achieved.
Tot al energy system. The addition of a t ot a l energy system
increased energy use in the dua l duct and VAV systems when considered
alone . When used in combin ation with exhaust air heat recovery and
reset cont rols in the dual duct , a 5 1 . 6 % reduction in t ot a l energy use
was realized . The tot al energy system seemed t o be incomp at ib le with
the VAV system due to the inefficiency of it s ab s orption coo ling in
meetin g the VAV ' s large proportion of cooling loads . In the single zone/
fan coi l system, a total energy system reduced energy use by 8 . 2% . In
combination with exhaus t air heat recovery , the system reduced energy
use by 15 . 9 % . Tot al energy systems were second only to ACES in potential
46
fo r tot al energy conservation. In combin ation with other energy
conservation opt ions, tot al energy systems achieved a reduction to 42 . 7 %
of base energy use in the single zone/ fan coil system.
Combinations o f conservation measures. Det ailed b reak downs of
energy use int o heatin g , cooling, and fan energy use are given in
Appendix B. Re l ative tot al energy use (with gas heat an d electric
coo lin g ) of the energy conservation measures an aly zed is shown graphically
in Figures 16 an d 17 for the three HVAC systems.
Office Buildin g, HVAC Capit al Costs and Payouts
A breakdown of energy use, capital costs and payouts is given in
Tab l e 4 for the dual duct system in the office buil din g with gas heat
and el ectric coo ling. Due to the differen ces in cost for gas and
el ect ricity, the combin ation with the l ower energy use may not always be
less expensive to operate. For examp le, the addition o f exhaust air
heat reco very reduces energy use 4 . 9% and operating costs by $6 30 ; the
addition of improved chiller efficien cy reduces energy use 2 . 2 % and
operatin g costs by $ 860 . Also, the c apit al cos t estimat ed fo r imp roved
chill er efficien cy is the increment al cost fo r improvement rather
than total machine cost.
The use of oil or el ect ricity for heating energy would signi ficant ly
shorten the expected payouts of heatin g energy conservation measures due
to the higher cost o f these two fuels. Fo r examp le , if ACES with heat
recovery and reset controls is considered as a sub stitute for an oil
D U A L D U C T B A S E
ECONO M I Z E R
E X HA UST A I R H E AT R E COVERY
R E S E T CONT ROL S
I M P R . C H I L L E R EF F .
DOU BLE B U N DL E
S O L A R H E A T
AC E S
T OTAL E N E R G Y SYST E M
E C O N O MI Z E R a R E S E T CONT ROL
H E AT R E C . a R E SET CONT ROL
R E SE T C O N T R O L a DOU B L E BDL .
R E S E T CON T R O L a SOL AR
R E SE T , H E AT REC a A C E S
RESET, HEAT R E C 8 SOLAR
RESET , H EAT R EC 8 TOTAL EN ERGY R ESET, HEAT REC , SOLAR 8 TOTAL ENE RGY
RE SET, H E AT REC a DOU B L E BDL
4 7
I 0 20%
ORNL OWG 7 8 - 9 8 7 8
1 100 .0
I 98. 7
1 95 . 1
I 73.0
I 97.8 l 73. 2
l 89.5
J 57 .8
] 104 .3 I 7 1 .6
J 57 .6
J 68 . 2
J 65 . 5
I 35. 1
I 5 1 .4
1 4 8 .4
I 4 2 .7
J 50.6 I I I I
40 % 60% 80 % 100 % R E L A T I V E ANNU A L E N E RGY USE
Fi gure 16 . HVAC ene rgy us e for en ergy con s e rvat i on me asure s in dual duct system in 40 , 5 0 0 ft 2 offi ce bui ldin g with gas he at and e l e ct ri c cool in g . (Base ene rgy us e i s 326 , 0 00 Bt u/ ft . 2 -y r . )
48
ORN L OWG 78 - 9879
D U A L DUCT
B A S E 1 100 .0
S I N GL E ZONE - FAN C O I L 1 64 .5
ECONOM I Z E R 1 64 . 2
EXHAUST A I R H E AT R E C . 1 58 .0
I M PR . C H I L L E R E F F . ) 63. 3
DOU B L E B U N DLE 1 60 .6
SOL A R H E AT 1 57.6
TOTAL E N E RGY ] 56.3
HEAT REC. 8 D O U B L E BDL . I 54 .2
H E AT REC. 8 SOLAR I 5 1 . 8
HEAT R EC . 8 ACES 1 33 . 8
H E AT R EC. 8 T OTAL E NE RGY 1 4 8 .6
V AV 1 56. 3
ECONOM I Z E R I 5 2 . 1
DOUBLE B U N DL E 1 4 4 .7
S O L A R H E AT ] 4 8.0
T OTAL E N E RGY l 60.7
V A R I A B L E SP E E D FAN I 52 .9
VA R. SP. FAN 8 DOUBLE BDL l 4 1 .3
V A R . SP. F A N 8 SOL A R 1 4 4 .6
I M P R . C H I LL E R E F F. I 54 . 7 I I I I I
0 20% 40% 60 % 80 % 100% R E L AT I V E A N N U A L E N E RGY U SE
Figure 1 7 . HVAC energy use for energy conservat ion me asures in dua l duct , s ing l e zone/ fan co i l , and VAV syst ems in 40 , 500 ft 2 offi ce bui lding with gas he at and e l ectric coo l ing . (Base ene rgy use is 326 , 000 Bt u/ ft . 2 -yr. )
Tab le 4 . HVAC energy us e , cap i t a l cost and payouts of dual duc t in 4 0 , 5 0 0 ft 2 offi c e
G a s Heating HVAC E l ectr ic Coo l ing Energy U s e
1 . Bas e 1 0 0 %a
3 . E xhaust Air Heat Recov ery 9 5 . 1 % 4 . Re s e t Contro l s 7 3 . 0 % 5 . Improved Ch i l l er E ffi c i ency 9 7 . 8% 6 . Doub l e Bund l e 73 . 2 % 7 . So l ar Heat 89 . 5% 8 . AC ES 5 7 . 8 % 9 . To t a l En ergy · 1 0 4 . 7 %
1 0 . E conom i z er & 4 7 1 . 6% 1 1 . 3 & 4 5 7 . 6% 1 2 . 4 & 6 6 8 . 2 % 1 3 . 4 & 7 65 . 5 % 1 4 . 3 , 4 & 8 35 . 1 % 1 5 . 3 , 4 & 7 5 1 . 4% 16 . 3 , 4 & 9 4 8 . 4% 1 7 . 3 , 4 & 6 5 0 . 6 %
aBas e ene rgy use is 326, 0 0 0 Btu/ ft 2 -y r .
bBase cap it al cos.t i s $ 2 70 , 0 0 0 .
aHi gh e r operat ing c os t .
Cap i t a l Cost
1 0 0 . 0%b
1 0 4 . 7% 1 0 0 . 6% 1 0 1 . 1 % 1 0 5 . 8% 1 7 2 . 9% 4 7 0 . 3% 1 5 4 . 8% 1 0 1 . 9 % 1 0 5 . 3% 1 0 6 . 5 % 1 7 3 . 5 % 4 2 2 . 9% 1 7 8 . 2% 1 60 . 1 % 1 1 1 . 4%
Retro fi t Payout (years)
N/A 2 0 . 0
0 . 2 3 . 5 2 . 9
9 3 . 5 1 56 . 0
a 0 . 6 1 . 3 1 . 9
2 0 . 1 5 7 . 0 1 6 . 9 1 3 . 4
2 . 4
Or ig inal D e s i gn Payout (years)
0 . 0
1 . 7
0 . 0 1 . 1
1 5 . 2 1 1 . 7
� 1.0
s o
heating/elect ric c ooling system , the ann ual savings increase so that
the payout period decreases to 38 . 9 years . With the same ACE S
compared to an elect ric heatin g and cooling case , t he annual savin gs
increase to give a payout period o f 15 . 1 years . Payout versus fuel
combination is given in Tab le 5 fo r the dual duct .
See Appendix C for tables o f capit al costs and payouts versus fuel
co mbination for the VAV and single zone/ fan coil systems . Cu rves o f
energy use versus capit al cost- are given in Figure 1 8 for the four fuel
combin ations in the dual duct system in the office building . Cu rves of
energy use versus capi tal cost are given in Figures 19 , 2 0 , and 21 for
the dual duct , sin gle zone/ fan coil and VAV syst ems with gas heat and
elect ric coolin g . These curves show that it is relatively inexpensive
to reach a relative energy use level o f 41% t o 54% in th e systems . The
VAV can reach the 41% level with a 10% increase in cost , with the dual
duct and sin gle z one/ fan coils able to reach the 5 1 % and 54% levels
with increases of cost of 1 1 % and 8% . Beyond these plateaus , large
investments are required for minimal energy reduct ions. As would be
expected, these plateaus are in the range where the no rmal ized energy
use fact or is app ro ximately one . ( In other words , app roximat ely one Btu
inp ut by HVAC is required to satisfy each Btu of demand. )
Also o f interest on these figures is the dashed curve representing
the energy use -to -cost relationship for a building being designed . When
exhaust air heat recovery is included in the design , the savings from
reduced heat in g and cooling _ equipment si zes is more than the cost of
the heat recovery exchanger . The effect o f this net savin gs is t o lower
capital cost for the same energy use or to offset the curve to the le ft .
Tab l e 5 . Payout v s . fue l comb inat i on for conservat i on me asures in 4 0 , 5 0 0 ft 2 offi c e with dua l duct
Re t rofit Payout (Ye ars )
E l ectric Gas Heat O i l Heat Heat
& & & E l ectric E l e ctri c E l ectric C o o l ing Coo l ing C o o l ing
3 . Exhaus t Air Heat Re cove ry 2 0 . 0 7 . 8 2 . 1 4 . Res et Contro l s 0 . 2 0 . 2 0 . 1 5 . Imp rov ed Chi l l e r E ffi c i ency 3 . 5 3 . 5 3 . 5 6 . Doub l e Bund l e 2 . 9 1 . 7 0 . 6 7 . So l ar Heat 9 3 . 3 5 4 . 6 1 8 . 8 8 . ACE S 1 5 6 . 0 7 1 . 6 2 0 . 5 9 . Tot al Ene rgy a a 4 . 2
1 0 . Econom i z e r & 4 0 . 6 0 . 5 0 . 3 1 1 . 3 & 4 1 . 3 0 . 9 0 . 4 1 2 . 4 & 6 1 . 9 1 . 5 0 . 8 1 3 . 4 & 7 2 0 . 1 1 5 . 9 8 . 0 1 4 . 3 ' 4 ' & 6 2 . 4 1 . 8 0 . 8 1 5 . 3 ' 4 & 7 1 6 . 9 1 2 . 2 5 . 3 1 6 . 3 , 4 & 8 5 7 . 0 38 . 2 1 5 . 1 1 7 . 3 , 4 & 9 1 3 . 9 8 . 3 3 . 0 1 8 . 3 ' 4 ' 7 & 9 2 5 . 2 1 6 . 6 6 . 4
--aH i gher op erat ing cost .
Gas Heat & ·
Gas Coo l ing
2 0 . 0 0 . 2
N/A 93 . 3
1 3 6 . 0 a Ul
0 . 6 ......
1 . 2 N/A
1 9 . 3 N/A
1 6 . 4 5 3 . 8 1 2 . 4 2 3 . 9
LLI (J) ::> >-(!) a: LLI z LLI 0 4 > z
180 %
1 6 0 %
140 %
120-,.o COOL ING FOR MORE D E T A I L
__ _ ON G A S H E AT I N G --A N D E L ECT R IC COOLING
O R N L OWG 78 - 98 7 1
100% � - - -
GAS HEAT I NG AND1SEE F I G U RE 19
8 0 %
60%
40%
20%
0
OIL H E AT WIT H I E L EC T R I C COOLING
I EL ECTRIC HEATING
A N D COOL I N G
100 °/o 120 % 140% 160% 1 8 0 % 200 % 220% 240% 260 % 280 % 300% 320 % 340 % 360 % 380% 400%
HVAC CAPITAL COST
F i gure 18 . HVAC energy us e vs . capital co st fo r four fue l comb inat ions in 4 0 , 500 ft 2 offi ce bui lding with dual duct sys tem . (Bas e energy use is 326 , 000 Btu/ ft 2 -yr . and base capit al cost i s $ 2 70 , 000 . )
(/1 N
w en :::> >(.!) a: w z w u < > X
9
O R N L-DWG 78- 9 8 6 1 R 3
- - --e I • 5
3A ' I • 3
11r; RETROFIT
CU R V E
I 6A
4 . � . 6 l \e-2 ,4
I I I I
I - B AS E , D U AL D U C T
2 - E C O N O M I Z E R
3- E X H A U ST A I R H E AT R ECOVE RY
4- R E S E T C O N T R OLS
5 - I M P R O V E D C H I L L E R E F F I C I E N CY
6- DOU B L E BU N D L E
7- SOL A R
8 - AC E S
9- TOT A L E N E RGY
A- O R I G I N A L D E S I G N , I N C L U D E S
C R E D I T F O R R E D U C E D EQ U I P M E N T
S I Z E S .
• 7
• 4,7
T 3A ,4 � 3,4
RIG�\ I � 3 4 6 3 A ,4 ,9 • 3,4,7 ��*,. 3A ,4,6A •.......;.• ,
J 3 4 9 OJRVE 1 ........_ - - - - - - - - - - - - - - - ::.JL�.a.. , , j I
I I I I
3,4,8 ( 4 2 0 "lo)
1 00 % 1 1 0 % 1 2 0 °/o 1 30% 1 4 0 °/o 1 50,.o 1 60 % 1 70% 1 80 o/o
HVAC C A P I TAL COS T
Figure 19 . HVAC energy us e vs . cap i tal cost for gas heat and e l ectric cool ing in o ffi ce with dual duct . ( Base ene rgy us e is 3 2 6 , 000 Btu/ ft 2 -yr . and b as e cap it al cost is $2 70 , 000 . )
1 9 0 °..4
lJ1 (J..l
liJ Cl) :::> > C) 0:::: liJ z liJ u <( > X
O R N L- OWG 78 - 9 8 8 0R
t OO � 1-- - - - - - - - e BA SE , DUAL DUCT
90 �
8 0 �
7 0 �
60 ,_
50 %
40 %
• • 2
Sf 6A 3A \• e 6
1 B A S E , S I NG L E ZON E FANCOI L
2 ECONOMI Z E R . 3 E X H AU ST A IR H E AT RE COVERY
4 RESET CONTROLS
5 I M PROVED CH ILLE R E F FICIE NCY 6 DOUBL E BUN DLE
7 SOL A R 8 AC E S 9 TOTAL EN E RGY A OR I G I N A L DE S I G N , I N CLU DES
C R E D I T FOR R E DUCE D EQU I PM E NT S I Z E S
e 9 e 1 •,
·
� I . .
R E TROF I T CU R V E
3A ,7 e e 3, 7
. '•� c 3 9
3A ,6A e _- - ;- - � - - · -
·-·
---------J I L ORI G I NA L DE S I GN 3A,9 I C U R V E
I I I I I
3, 8 ( 440 �0 )
90 � 1 00 "o 1 10 "0 1 20 � 1 30 � 140�o
HVAC CAP I TAL COST
1 50 "o 160�
F i gure 20 . HVAC en ergy u s e vs . cap i t a l c o s t for gas heat i ng and e l ectric coo ling in o ffi ce with s in g l e zone/ fan co i l .
1 70 �
( Bas e energy us e i s 3 2 6 , 000. Btu/ ft 2 -y r . and b as e cap i t al cost i s $ 2 70 , 000 . )
(J1 �
O R N L - DWG 7 8 - 9 8 8 t
tOO % t- - -- 0 BASE , DUAL DUCT
9 0 %
UJ 80 -yo U) ::::> >-t::) ffi 70 cro z UJ
� 5; 6 0 -yo
50 %
4 0 -,o
.3 t
-��0 $ 2
6 0 0 2 6 t O
t B A S E , VAV 2 E C O N O M I Z E R 3 E X H AU S T A I R H E AT RE COVE R Y 4 R ESET CONTROLS 5 I M P R O V E D C H I L L E D 6 DO U B L E B U N DL E
7 SOL A R
8 A C E S
9 TOT A L E N E RGY
tO V A R I A B L E S P E E D FA N A O R I G I N A L DESIGN , I NCLU DES
C R E DI T FOR R E DU C E D EQU I PM ENT SI ZES
0 9
0 7
6 A ,,0
e ' • c RETROFI T CURVE
1 6A 1 0 0.... - -r - m
• 6,t0 � O R I G I NA L D E S I G N CU RVE o
. 2 ,7 ,t o I I
t OO % t f O «ro t 2 0 cro f 3 0 % t40 % t 50 ,. t 6 0 % H VA C C A P I TAL C O S T
t 7 0 % f 8 0 ,.
Figure 2 1 . HVAC energy use vs . capital cost for gas he at ing and e lect ri c coo lin g in offi ce with VAV . ( Base ene rgy use is 326 , 000 Btu/ ft 2 -yr . and base capit al cost i s $2 70 , 000 . ACES was not analyzed in this syst em . )
VJ t.l,
56
Ho spital HVAC Ene r gy Us e
The impact o f the conse rvation me asure s on hospita l ene rgy us e is
given in Fi gure 22 in a format s i mi l ar to th at on o ffi ce energy us e .
Th e large venti l ation rate s and lon ge r op e rat in g ho urs ch an ged th e
e ffects of th e conservation me as ure s on ene rgy us e in s e ve ral cas e s .
As a ru le , the l arge p e rc entage re ducti ons pos s ib l e in th e o ffi ce we re
not ach i e ve d in the hosp ita l . Howeve r , the total ene r gy us e re ducti ons
pos s ib l e we re about equa l in both bui l din g type s , b e in g app roxi mate ly
200 , 0 00 Btu/ ft2 y r .
Hospit a l HVAC Capita l Cost and Payouts
A b re akdown of ene rgy us e , cap ita l c os ts an d pay outs is given in
Tab l e 6 for the s in g l e zon e /fan coi l system in th e hospital with g as
he at and e l ectri c coo l in g . The e ffe ct on p ay out o f fue l c ombinati on
is detai l e d in Tab l e 7 . Fi gure s 2 3 an d 2 4 are the en ergy us e versus
c ap ita l c ost curves for the two HVAC systems ana ly z e d in the hospital .
App en di ces B an d C contain a detai l e d b reak down of ene rgy us e for
b oth HVAC systems , a tab l e o f ene rgy us e , cap ital cos ts an d p ayouts for
the s in gl e zone -VAV sys te m , an d a tab l e detai l in g the e f fe ct o f fue l
c ombination on pay out for the s in gl e zone -VAV syste m .
Compari s on with Othe r Studies
The re sults of thi s HVAC ene rgy us e study are c ons i s tent with
avai l ab l e ene rgy us e ave rage s an d anothe r HVAC ene rgy us e s tudy .
HVAC ene rgy us e ave ra ge s are avai l ab l e in two forms :
5 1 N G L E ZO NE - FA N C O I L
BAS E
E X H A U ST AI R H E AT R EC.
I M P R . C H I L L E R E F F.
DOU B L E B U N D L E
S O L A R H E AT
AC E S ( W/ H E AT R E C )
TOTA L E N E R GY SYST E M
HEAT REC. AND DOUBLE BDL
HEAT REC. AND TOTAL ENERGY
t£AT REC, SOLAR AND TOTAL ENERGY S I N G L E Z O N E - VAV
E X H A U ST A I R H E AT R EC .
I M P R . C H I L L E R E F F .
D O U B L E BU N D LE
S O L A R H E AT
TOT A L E N E R G Y SYSTEM
H EAT REC.AND DOOBLE BDL.
HEAT REC. AND TOTAL ENERG
H EAT REC, SOLAR AKJ TOTAL
...
ENERGY
5 7
I I
l 47 . 2
O R N L- D W G 7 8 - 9 8 8 2
1 100.0
I 86 .3
I 9 8 . 1
I 94 . 3
I 9 4 . 8
I 80. 8
I 83 .9
l 6 3 .5
l 6 1 .0
I 9 6 .5
J 8 2 .9 I 9 4 . 7
I 8 9 .4
I 9 1 . 2
1 7 8 . 2
J 7 8 .6
l 6 4 . 4
l 6 0.9
I l I 6 0 cyo 1 00 %
R ELATIVE AN NUAL ENERGY USE
Figure 2 2 . HVAC ene rgy us e for conservat i on me asures in 1 00 , 000 ft 2 hospital with gas heat and e l e ct ric cool ing . (Base ene rgy us e i s 4 2 3 , 000 Btu/ ft2 -yr . )
Table 6 . HVAC energy us e , capital co sts and payout s for 1 00 , 000 ft2 hospit al with single z one/fan coil
Gas Heat HVAC Elect ric Coolin g Energy Use
1 . Bas e 1 0 0%a
2 . Exhaust Air Heat Recovery 86 . 3 % 3 . Imp roved Chi ller Efficiency 98 . 1 % 4 . Double Bundle 94 . 3% 5 . Solar Heat 94 . 8% 6 . ACES & 2 47 . 2 % 7 . Total Energy 80 . 8 % 8 . 2 & 4 83 . 9 % 9 . 2 & 7 63 . 5 %
1 0 . 2 ' 5 & 7 6 1 . 0%
aBase energy use is 42 3 , 0 00 Btu/ ft 2 -yr . bBas e capital cost is $ 1 , 1 19 , 0 00 .
cHigher operating cost .
Cap it al Cost
100� 1 0 2 . 7% 100 . 8% 105 . 9% 1 35 . 1 % 499 . 3% 1 37 . 6% 108 . 6% 140 . 3% 1 75 . 4%
Retrofit Payout
(Years )
N/A 3 . 3 4 . 0
1 8 . 3 1 1 7 . 6 144 . 5
c 9 . 1
23 . 6 38 . 4
Original Des i gn Payout
(Years)
0 . 0
9 . 2
0 . 0
U'1 00
T abl e 7 . Payout v s . fuel comb inat i on for HVAC energy con s ervat ion measure s in 1 0 0 , 000 ft 2 hospit al w ith s ingl e z one/ fan coil
. Ret ro fit Payout (Ye ars )
El ect ri c G as Heat Oil Heat Heat
& & & El ectric El ectric El ectric Cool ing Cool ing Cool ing
1 . B as e N/A N/A N/A 2 . E xhaust Air Heat Recovery 3 . 3 2 . 0 0 . 8 3 . Improved Chill er E ffi c i ency 4 . 0 4 . 0 4 . 0 4 . Doubl e Bundl e 1 8 . 3 1 0 . 9 3 . 9 5 . S ol ar 1 1 7 . 6 7 0 . 1 25 . 5 6 . ACE S & 2 1 1 4 . 5 80 . 1 2 7 . 4 7 . T ot al Energy a 1 7 . 0 3 . 2 8 . 2 & 4 9 . 1 5 . 6 2 . 1 9 . 2 & 7 2 3 . 6 1 0 . 3 3 . 0
1 0 . 2 ' 5 & 7 3 8 . 4 1 8 . 0 5 . 5 -
�i gher op erat ing cost .
Gas Heat &
G as Cool ing
N/A 3 . 4
1 1 7 . 6 1 84 . 2
a U'1 '-0
36 . 3 5 5 . 2
L&J (/) ::> >C) a: L&J z L&J 0 <l > X
t O - - -· B A S E
1 .. 3 !\ e 4
2A I • 1 e 2 \t1- 2A\ e 2 , 4 "'4A
- , ' ' ' ' ' ......
. 5
e 7
O R N L - D W G 7 8 - 9 8 8 3R
t B A S E
2 E X H A U ST A I R H E AT R E C O V ERY
3 I M P R O V E D C H I L L E R EF F IC I E N CY
4 DOU B LE B U N D L E
5 SOL A R H E AT
6 AC E S
7 T OTAL E N E R GY
A O R I G I N A L DE S I G N , I N C LU DE S C R E D I T F O R R E D U C E D EQ U I P M ENT
S I Z ES
......_, � RETRa=1T CURVE
....... ..........._ _ ?� 2 7
t OO 'Yo t tO'Yo
- ��7-'L_ • ....;,:::-::::::::-:::=-=--.----- 2, 5, 7 'oRKiNic- - - - == • -----1 DESIGN CU RVE
t 2 0'Yo 1 30% 1 40% 150% H VAC C A P I TA L COST
t 60%
2 , 6 ( 500 �o}
t 70% teo %
Figure 2 3 . HVAC energy us e vs . HVAC cap i t al co st for gas heat ing and el ect ric coo l ing in hospital with s ingl e zone/ fan co i l . ( B as e ene rgy us e i s 42 3 , 000 Btu/ ft 2 -yr . and b as e cap i t a l c ost is $ 1 , 1 19 , 0 00 . )
(]\ 0
w en :::> > (!) a::: w z w 0 ct > :X:
ORN L- DWG 78- 9884R
- - - -e - BA S E , S I N G L E ZON E I FAN CO I L
l� I BA S E
! • 4 • 5
2 - E X H. AI R H E AT RECOV ERY 3 - I M PR. CH I LL E R EFFICI E N CY 4 - DOU BLE B U N DLE 5- SO L A R H E AT 1 TOTAL EN ERGY
2 I ' eJ 2
2A'-' � 4� 1 '1, t ' ',
1000/e
', �ETROFIT CURVE
/" ............ ___
• 1
A - OR I G I N A L DES I G N , I N C L U D E S C R E D I T FOR R EDUCE D . EO U I P M E N T S I Z E S .
\. � --ORIGINAL -----.::-c�":"':��.._.-------
DE S I G N C U RVE 2A, 7
1 1 <:1/o 1 20% 130cyo 1 40% 1 5 0%
H VAC CAPI TAL COST
1 60'Yo 1 70% 1 8 0%
F i gure 24 . HVAC ene rgy us e vs . HVAC cap i t a l cos t for g a s heat ing and e l e ctric co o l i ng in hos p i t a l wi th s ing l e zone/VAV . ( Bas e ene rgy us e is 42 3 , 000 Bt u/ ft 2 -yr . an d b as e capi t a l cost i s $ 1 , 1 19 , 0 00 . )
0\ ......
62
(1) "macroscopic" averages such as those developed by Jackson
and Johnson, 2 which are derived from tot al building type energy use
divided by tot al buildin g type floor space and (2 ) "micr oscopic" averages
developed from surveys of actual buildings, such as those done by Hitt man
Associat es1 9 in Baltimore and Sysk a & Hennessy and Tishman Research
Co rporat ion2 0 in New Yo rk City . The other HVAC energy use study was
done by Rand Corporation 21 and covered several of the conservation
measures considered in this study .
Comparison with "macroscopic" energy use averages for 19 75 shows
that the "base " energy use figures for the o ffice and hospit al are
higher than the national averages (see Table 8) . Since the "b ase" energy
use figures were developed as represent ative of pre -embargo design and
operation, their higher energy use would be expected. The energy use of
the best energy conservin g case was signi ficantly lower than the n ational
average for b oth buildin g types . For the o ffice buildin g , the nation al
ave rage falls between the expect ed energy use for the dual duct
(p re -embargo design ) and that for the VAV and sin gle z one/ fan coil
systems. Als o, operational_ chan ges such as night se tb ack of thermost ats
will lower energy use . Fo r the hospit al, the nation al average en ergy
use is less than expected for the HVAC syst ems analyzed. However, the
nation al average for hospit als is in the ran ge of energy use at t ain able
by addin g a double bundle exchanger or exh aust air heat recovery or by
night setb ack. From these comparisons , it wo uld appear that the energy
uses developed in this st udy agree with the st atistical average o f
nat ional energy use .
63
Tab l e 8 . Comp ari son o f ene rgy us e predi ct e d an d "macros copi c " av e rag e ene rgy us e
Predict e d ' 'Macros c opi c' ' Ene rgy Av e rage
Us e Energy Use 2
Bui l din g (Btu/ Ft 2 -yr) (Btu/ Ft 2 -yr) D i f feren ce
Office Base 32 6 , 000 2 4 7 , 0 00 + 3 2 % Best Conservat ion 1 10 , 000 2 4 7 , 000 - 5 5 %
Ho spit al B as e 423 , 000 3 76 , 000 + 12 Be st Conse rv at ion 199 , 0 00 3 76 , 000 - 4 7 %
Simi l ar re s u lt s are foun d i n co mpari sons w i t h "mi crosc opic" ene rgy
us e ave rages . Tab le 9 det ai ls the c omp ari son of ene rgy use in o ffi ce
bui l din gs deve loped in th i s st udy and the ave ra ge s re su lt in g from
bui ldin g surveys . O f the bu i l din gs surveye d , many in corporat e d ope rat ion a l
ch an ge s wh ich we re not cons i de re d i n th is report . As expe ct e d ,
the "b as e " dua l duc t pred icts h i gher ene rgy u s e than found i n th e surveys ,
and the dua l duct wi th con s e rvat ion me aus re s an d the VAV b oth predict
le s s ene rgy us e th an found in the surveys . Another re as on fo r the l ow
ener gy use foun d in the surveys is the l e s s th an 100% penet rat ion �80 % )
o f cent ral a i r condit i on in g . Howeve r, the lower coo l in g ene rgy u s e
due t o ro om a i r con dit ion e rs i s somewh at o ffs et b y t h e us e o f ab s o rpt i on
coo lin g in the two are as su rveye d .
6 4
Table 9 . Comparison o f ene rgy · use predicted an d en ergy use averages from building surveys
HVAC System
A . Office - Dual Duct B. Office - Dual Duct with
Exhaust Ai r He at Recove ry Reset Cont rols and Double Bundle
C. Offi ce - VAV
Average Ene rgy Use
Corre cted a Energy Use Hittman
( Btu/ Ft 2 -yr) . (Baltimore )
1 73 , 000
9 7 , 000 106 , 000
125 , 000
Tishman -Sysk a & Hennessy
(New York City)
1 1 2 , 000
ac . o rre ct 1ons are : ( 1 ) Ele ct ricity conve rted at 341 3 Bt u/kwh . (2 ) Energy for li ghts is included . ( 3 ) Ni ght se tb ack of the rmost ats is include d. (4 ) He at ing is base d on dist ri ct st eam he at ing
( 100% onsite e fficiency) .
In the Rand Study, the office bui ldin g mo deled was 20 st ories tall
wit h 360 , 0 00 square feet of floo r sp ace comp are d to the three -story
40 , 5 00 square foot office analy zed in this rep ort . This di ffe ren ce in
building si ze can be expected to affect the ene rgy use predicted due
to the di fference in the rat io of buildin g shell are a to floor are a.
The rat i o fo r the Rand bui ldin g is app roximat ely S O % o f that for the
bui l din g analyzed in this repo rt . The net e ffe ct of this smalle r rat i o
i s to lower the t ot al ene rgy use pe r square foot . ( Incre ases in cooling
ene rgy use will be more than offset by decre ases in he at ing ene rgy use . )
With this ene rgy use di ffe rence in min d, the results of this study agree
we ll with the ene rgy uses pre di cted by Rand, as shown in Table 10 .
65
Tab le 1 0 . Comp aris on o f offi ce HVAC en ergy us e p re di cte d with that in the Rand St udy2 1
Co rre cte d Ene rgy Us e a Rand
HVAC Sys tem (Btu/ Ft 2 -yr) Ene rgy Use Di ffe rence
Dua l Duct 2 9 8 , 5 00 2 3 7 , 5 0 0 VAV 2 2 3 , 900 19 2 ' 800 VAV - Abs o rpt i on 30 3 , 1 20 2 32 , 2 00 VAV - Heat Re covery &
2 1 2 , 9 7 0b
E conomi z e r 1 7 5 , 600 VAV - E l e ct ri c He at 324 , 690 252 ' 800
aCorre ct ions to be c on s i s tent with Rand St udy are : ( 1 ) E le ct ri c ity c onve rt e d at 10 , 0 00 Btu/kwh . ( 2 ) Lightin g ene rgy us e is in c l ude d . ( 3) L i gh t in g leve l co rrect e d to 2 . 7 wat t s / ft 2 • (4 ) Venti l at i on ai r re duc e d app roxi mate ly S O % . (5 ) Heat in g and c oo l in g ene rgy us e corre ct e d for lower
l i ghting leve l .
bEconomi z e r on ly .
2 6 % 1 6 % 3 1 %
2 1 % 2 8 %
V . CONC LU S I ONS
C onc lus i ons on the Cons e rvation Me as ure s An alyz e d
Re s u l t s sh ow th at exhaus t ai r he at re cove ry c an i n many cas e s reduce
both fi rs t co st and annua l ene rgy use wh en in co rporat e d in th e ori gin a l
de s i gn o f a bui l din g . Savin gs are de t e rmin ed by we athe r an d vent i l at i on
rat e . Fi rs t co s t s avin gs are due to th e re duction in h e at ing an d coo l i ng
equipment c os t s b ein g l arge r than the cos t incre as e o f th e e xch an ge r .
As de s i gn condition s become more seve re , l arge r cos t s avin gs are
re a l i z e d . Cos t s avin gs are also di re ct l y propo rt ional to vent i l ation
rat e . As vent i l at i on rat e de creas e s , fi rs t cos t savin gs are re duc e d
and may dis app e ar . Ene rgy savin gs are pre dominant ly de t e rmined b y
he at in g requi re ment s , with l arge r ann ual heat in g lo ads y i e l ding l arge r
s avin gs . Ene rgy savings are a l so proport i onal t o ven t i l at i on rat e .
Re sult s show that th e re are seve ra l "re t rofi t " cons ervat ion me as ures
wh i ch c an s i gni fi cant ly reduce HVAC ene rgy us e in e xi stin g offi ce
bui l din gs with pre - emb argo HVAC sys tems . I f thes e me as ure s in c l ude
res e t cont rol s , doub l e bun d le e xchan ge rs , and e xhaust ai r h e at re cove ry ,
a 49 % reduct ion in ene rgy us e can b e e xpect e d . Us in g current p ri ces fo r
gas (he at in g) and e l e ct ri ci ty ( cool in g) , th e s e me as ures show at t ract ive
payouts of three ye ars or l e s s . In HVAC sys t e ms of more re cent des ign ,
the addition of doub l e bundle e xchan ge rs an d e xhaus t ai r heat recove ry
can re duce ene rgy us e by 1 5 % . Th e payout s fo r the s e me asure s were not
as at t ract ive , ranging from five t o twenty ye ars .
66
67
In the maj ority of offi ce bui ldin gs designed in fut ure years, the
j ust i fi cat i on of conservat i on measures wi l l be made against the cost of
el ectricity for he ating and coo ling . Proj ect ions of future commerci al
energy use by Jackson et al . 1 show that total gas and oi l use wi l l remain
essent ial ly constant and that any in crease in commerci al energy use wil l
be in el ect ricity. With payo uts est ab l ished on this basis , doub le bundle
exchan gers and exhaust ai r heat recovery show very short payouts.
Several other opt ions such as tot al energy systems , AC ES and so l ar
heat in g have payouts which also may be j ust i fiab l e for the longer term
wi th l i fe cycle cost in g . The addi tion of these opt ions can reduce energy
use to 35% o f base energy use .
In the hospit al, the addi tion o f exhaust ai r heat recovery can
reduce energy use by 14 % . Based on current prices for gas heat ing
and el ectric coo l ing, this option can show a payout of three to four
years . For new desi gn opt ions, as ment i oned ab ove , payouts wi l l be
est imated us ing el ectri city as the fuel fo r heat in g and coo l ing . On
this basis, the addi tion of exhaust air heat reco very and doub le bundle
exchan gers can reduce energy use by 16 % with a payout of two years. The
addition o f heat recovery and a tot al energy system can reduce energy use
by 36% with a payout of less than four years . ACES and so l ar heat ing
have payouts whi ch may be j ust i fiable wi th li fe cycl e cost ing for
reduct ions in energy use of up to 5 3% .
Limitations of This Report and Recommendat ions for Further Study
The in ab i l i ty to an a lyze soph is ticated cont rol s and the consi derat ion
of on ly the effects of HVAC equipment vari ations pl ace some limit at i ons
68
on the usefulness o f this s tudy . Air- t o- air heat pumps were not
cons ide red . Howeve r , t he ir impact on the comme rcial mark et to dat e
has b een minima l and the ir omi s s i on shou l d not b e s ign i fi c ant . (No heat
pumps l arger than 50 tons are ava i l ab l e current ly . ) I t i s not expect ed
that the heat pump w i l l capture a s i gn i fi cant share o f the commerc ial
market in the futur e except in very smal l bui l d ings with sma l l unit s .
Severa l sophi s t i cated cont rol syst ems are current l y avai l ab l e wh ich
offer ene rgy cons erva t ion pot ent i al . The s e s yst ems range in comp l exity
from chi l l er op erat ion optimi zat ion syst ems to total bui l d ing energy
manag ement syst ems . Payouts o f two to three years on opt imi zat ion
syst ems are not uncommon for mu l t ip l e chi l l er instal l at ions . S inc e
the s e opt imi z at ion syst ems requ ire an i terative s o l ut ion each hour , they
were not inc luded due to l ack of t ime . The total bui ld ing energy
manag ement systems operate s imi l arl y , onl y on a l arger scal e .
The interr e l at ion o f the HVAC equipment , operat ing s chedu l e and
bui ld ing shel l shou ld not be ignored . Although ana l ys i s of the effect s
o f onl y equipment var iat ion s on energy use i s enl i ghtening , i t i s not a
comp l et e p i cture o f the con s erv at ion opt ions open to the bui l d ing owner .
I n many cas es , changes in operat ing s chedu l e can dras t i ca l l y affect the
energy saving s of equipment mod ifications . For ins tance , the add i t ion
of night s etback can negat e the energy savings of an econom i z er cyc l e .
To get the comp l e te picture , the net effect s o f al l thre e o f the s e
variat ions mus t be cons idered . Based on this s tudy , worthwhi l e future
s tudy coul d be done on contro l syst ems and the r e l a t ions of HVAC
equipment , opera t ing s ch edu l e and bui ld ing she l l .
REFERENCES
LIST OF RE FE RENCES
1 . J . R . J ack son , S . Cohn , J . Cope , and W . S . J ohnson , The Commer cia l Demand for Ene�gy : A Disagg� gated Approach, Oak Ri dge , Tennes see , Oak Ri dge Nat i ona l L aborat o ry , ORNL/CON - 1 5 , Apri l l9 78 .
2 . J . R . Jack s on an d W . S . Johns on , Corrme raia l Energy Use : A Disaggre gation by Fue l , Bui lding Type, and End Use , Oak Ri dge , Tennes see , Oak Ridge N at i onal Laborat ory , ORNL/CON - 1 4 , Feb ruary 19 7 8 .
3 . W . S . J ohn s on and F . E . P i e rce � Energy and Cos t Ana lysis of Comme�cia l Bui lding She l l Ch�aa teris tics and Operatin g Sc hedu le s, O ak Ri dge , Tenne s s ee , Oak Ridge Nat ion al Lab orat ory , t o be pub l ish ed .
4 . ASHRAE Handbook - 19 ?2, New Yo rk , New York , Ame ri c an Soci ety of H� at in g, Re fri ge rat in g and Ai r- Condi t i oning En gine e rs , Inc . , 1 9 72 ( an d l at e r vo l ume s ) .
5 . Eb rahim Farahan , Centra l Heating - Package Boi lers , Oak Ri dge , Tenne s s e e , Oak Ri dge N at ion a l Laborato ry , ANL/CES/TE -6 , May 1 9 7 7 .
6 . Bureau o f Census , Cu��nt Industria l Reports - Air Condi tioning and Refrige�ation Equipment - 19 ?5, Wash in gt on , D . C . , U . S . Depart ment of Comme rce , MA- 3 5 M , 1 9 7 5 .
7. ASHRAE Standa�d 90- ?5, New Yo rk , New York , Ame ri can Society o f He at ing, Re fri ge ratin g and Ai r-Condit i onin g Engineers , In c . , 1 9 7 5 .
8 . NECAP - NASA 's Ene�gy-Cost Ana lysis Pro gram, Part I - Us er ' s Manua l and Part I I - En gine e rin g Manua l , R . H . Hennin ge r , Ed . , NASA C R - 2 5 9 0 , Part s I and I I , Sept e mb e r 19 75 .
9 . ERDA Faci li ties So lar De sign Manua l, Los Al amos , New Me xi co , Los Al amos Scient i fi c Labo rat ory , ERDA- 7 7 - 65 , August 1 9 77 .
10 . Kenne rd L . Bow en , "Ene rgy Re cove ry from Exhaust Ai r , " ASHRAE Jou�a l, Apri l 19 74 .
1 1 . Ai� Force Manua l 88-8, Chap t e r 6 , "Engine e rin g We ath er Dat a , " AFM 88- 8 , June 19 76 .
12 . H . C . Fi s cher, " l ee & Wate r , Annua l Cyc l e Ene rgy Sys tem Offe rs S avin gs in He at in g, Co o l in g , " PE Magaz ine , June 19 76 .
13 . ERDA-SINB Ca Zcu Zation Book, Jenk int own , Pennsyl van i a , Rob e rt G . We rden & As so ci at e s , I nc . , 19 7 7 .
70
7 1
14 . Bui lding Cons truc tion Cos t Data 19 753 Duxbury , Mas sachus etts , Rob ert S . Means Company , Inc . , 19 74 .
15 . 1 9 75 Dodge Manua l for Bui lding Cons truction Pricing and Scheduling3 New York , New York , McGraw -Hi l l Informat ion Sy stems Company , 19 75 .
16 . A . M . Khashab , Heating3 Venti lating and Air-Condi tioning Sys tems Estimating Manua l3 New York , New York , McGraw -Hi l l Book Company , 19 7 7 .
1 7 . Design Cos t Fi le 1 9 76 Composi te Prices3 New York , New Yo rk , McKee Be rge r-Mansueto , Inc . , 19 76 .
18 . J . R . Jackson , pe rs onal communicat i on , O ak Ri dge , Tennes see , Oak Ridge Nat ional Laborato ry , Feb ruary 19 78 .
19 . Physical . Cha�cteristics 3 Energy Consumpti on and Re lated Ins titutional Factors in the Comme rcia l Sector3 Columb i a , Mary l and , Hi ttman As s oc i ates , Inc . , Octob er 1 9 75 .
20 . Energy Conservation in Exis ting Office Bui ldings 3 New York , New York , Syska & Henne ssy , and Tishman Res earch Corp�rat ion , 1 9 7 7 .
2 1 . Richard G . Salter, Rob ert L . Petrusch e l l and Kath leen A . Wo l f , Energy Conservation in Nonresidentia l Bui ldings 3 Santa Monica, Cal i forni a� The Rand Corpo ration , Octob er 19 76 .
Re ferences o f gene ra l int ere st - ICES Techno logy Ev aluat i ons
Charles L . Segas er, Heat Recovery Equipment for Engines, Oak Ridge , Tennes s ee , O ak Ri dge Nat iona l Lab orat ory , ANL/CES/TE 7 7 -4 , Apri l 19 7 7 .
J . E . Chri st i an , Centra l Coo ling - Absorpti ve Chi l lers3 Oak Ridge , Tenne ssee , Oak Ridge Nat ion al Lab orat ory , ANL/CES/TE 7 7 -8 , Augus t 1 9 7 7 .
J . E . Chris t i an , unitary Water-to-Air Heat Pumps, Oak Ri dge , Tennessee , Oak Ridge Nat i onal Lab orat ory , ANL/CES/TE 7 7 -9 .
J . E . Chris t i an , unitary Air-to-Air Heat Pumps3 Oak Ri dge , Tenness ee ; O ak Ri dge Nat i onal Laborat ory AN L/CES/TE 7 7 - 10 .
APPEND I CES
APPEND IX A
SAMP LE CALCULAT IONS
-....J .+:>-
Tab l e A- 1 . Resu l t s of samp l e c a l c u l a t ion of so l ar heat ing sys t em performance in office with dua l duc t u s ing ERDA Fac i l i t i e s S o l ar Des ign Manual 9
Space heat ing ( 1 0 6 B t u )
So l a r I n so l a t i on/MO - S Fc
( 1 0 1 Btu)
SLB R/SF ( 1 0- " ) c
C o l l ec t o r Area ( S Fc
)
Month l y SBLR Mont h l y Frac t i o n by So l a r
Month l y C o l l ec t ed Energy
Annual Frac t i on by So l ar
Annua l Heat i n g Energy
SF = C o l l ec t o r area - ft 2 • c
J 4 24 . 6
3 9 . 0
. 9 1 9
5 0 0 0 Sf<' . 460
. 1 67
7 0 . 9
F M A
406 . 8 2 99 . 5 77 . 6
44 . 0 46 . 8 4 7 . 8
1 . 08 2 1 . 56 3 6 . 160
. 5 4 1 . 78 1 3 . 080
. 1 96 . 28 3 . 8 2 0
79 . 7 84 . 8 6 3 . 6
S L B R = Ra t i o o f s o l ar inso l a t ion to bui l d ing heat ing l oad .
Month
M J J A s 4 1 . 2 24 . 1 0 7 . 0 26 . 6
56 . 8 5 5 . 3 5 3 . 1 5 3 . 2 5 0 . 0
1 3 . 790 2 2 . 946 0 76 . 0 1 8 . 797
6 . 895 1 1 . 4 7 3 0 38 . 0 9 . 399
. 98 2 0 . 999 0 1 . 000 . 996
4 0 . 5 24 . 1 0 7 . 0 26 . 5
0 1 20 . 8
7 1 . 8
5 . 944
2 . 972
. 808
9 7 . 6
N D To t ;,� !
3 3 1 . 7 454 . 9 2 , 2 1 4 . 7
46 . 2 45 . 2 609 1 . 393 0 . 994
0 . 697 0 . 49 7
. 25 2 . 1 80
8 3 . 6 8 1 . 9 660 . 2
. 298
2 0 , 380 1Hu/ ft 7
Tab l e A- 2 . Samp l e calculat ion of performance o f exhaust air heat recovery in hospitala
B in T 1
1 05 / 1 0 9 1 0 7 1 00 / 1 04 1 0 2
95/99 97 90/94 92 85/89 87 80/84 8 2 75/79 7 7 70/74 72 65 /69 67 60/64 62 55/59 5 7 50/54 52 45/49 47 40/44 42 Below 39 37
T2
84 . 9 8 2 . 4 80 . 9 79 . 4 77 . 9 76 . 4 74 . 9 73 . 4 7 1 . 9 70 . 4 6 8 . 9 67 . 4 65 . 9 64 . 4 62 . 9
aExhaus t Air : Tdb - 74° .
�T
- 2 3 . 1 - 1 9 . 6 - 1 6 . 1 - 1 2 . 5
- 9 . 1 -5 . 6 - 2 . 1
1 . 4 4 . 9 8 . 4
1 1 . 9 1 5 . 4 1 8 . 9 2 2 . 4 25 . 9
�Qb MBTUH
- 1 , 048 - 8 89 - 7 30 - 5 6 7 - 4 1 3 - 2 54
- 95 64
2 2 2 3 8 1 540 699 8 5 7
1 , 0 1 6 1 , 1 75
Occup . Hrs .
3 2 0 75
155 2 34 2 8 0 2 5 2 225 1 95 1 8 4 1 7 7 1 8 1 1 9 2 1 8 7 5 6 0
�Q-Occ . MBTU
- 3 , 1 0 0 - 1 7 , 800 - 5 4 , 800 - 8 7 , 900 - 96 , 600 - 7 1 , 1 00 - 23 , 900 + 1 4 , 400
43 , 300 70 , 100 95 , 600
1 26 , 500 164 , 5 00 1 90 , 000 658 , 000
Unocc . Hrs .
8 3
1 7 64
1 64 348 499 5 36 5 4 1 424 398 373 3 89 435
1 , 648
�Q-Unocc . MBTU
- 1 , 000 - 2 , 700
- 1 2 , 400 -36 , 300 -67 , 700 - 8 8 , 40 0 - 4 7 , 400
34 , 300 105 , 5 00 1 6 1 , 500 2 1 4 , 900 260 , 700 333 , 4 00 442 , 000
1 , 936 , 400
& = T1 - T2 /T 1 - T3 , where T 1 i s outs ide air temperature , T2 is out s ide air after exchanger and T3 is exhaust air (See Fig . 5) .
T2 = T1 - . 7 (T l - T3 ) = . 3T l + 5 1 . 8 . As sume 70° is change -over temperature when unoccupied and 50° when occupied .
b�Q = (CFM) (C ) (�T) p Net Coo l ing Saving s
�Q Occ . hrs . (Sum cool ing hours above 5 0 ° ) + �Q Unocc . hrs . (Sum cool ing hours above 70 ° ) - 5 , 300 - 2 2 1 , 600 = - 2 26 , 900 MBTU ( 2 , 300 Btu/Sf-yr)
Net Heat ing Savings �Q Occ . hrs . (Sum heat ing hours below 50° ) + �Q Unocc. hrs . (Sum heat ing hours below 70 ° ) 1 , 0 1 2 , 500 + 3 , 454 , 400 = 4 , 4 66 , 900 MBTU (55 , 840 Btu/Sf-yr)
'-l Ul
Mon t h
Nov . Dec . Jan . Feb . Mar . Ap r . May Jun e Ju l y Aug . S ep t . O c t .
To t a l
Tab l e A- 3 . Samp l e ca l cu l at i on o f ACE S per formance
O ffi ce - Dua l Duct - E xh . Air Ht . Rec . & Reset Contro l s
Heat E x t rac t ed N e t Heat ing from St orage Coo l i ng Mont h l y Cumu l at ive
Load 1 0 6 B t u Load Load Load ( 1 0 6 B t u ) ( . 8 3 3 o f l -I. L . ) ( 1 0 6 Btu) ( 1 0 6 B tu) ( 1 0 6 B t u )
33 1 . 7 - 2 76 . 4 5 1 . 3 - 2 2 5 . 1 2 2 5 . 1 4 5 4 . 9 - 3 78 . 8 34 . 4 - 344 . 4 - 5 6 2 . 7 4 2 4 . 6 - 35 3 . 8 3 2 . 6 - 3 2 1 . 2 - 86 7 . 0 4 0 6 . 8 - 3 3 9 . 0 3 0 . 4 - 3 08 . 6 - 1 , 1 49 . 6 29 9 . 5 - 24 9 . 6 6 8 . 5 - 1 8 1 . 1 - 1 , 2 96 . 2
7 7 . 6 - 64 . 7 1 3 0 . 6 65 . 9 - 1 , 1 9 1 . 4 4 1 . 2 - 34 . 3 1 5 7 . 0 1 2 2 . 7 - 1 , 0 3 3 . 0 2 4 . 1 - 2 0 . 1 2 0 7 . 1 1 8 7 . 0 - 8 1 5 . 0
0 . 0 0 . 0 39 8 . 8 398 . 8 39 1 . 7 7 . 0 - 5 . 8 3 5 5 . 8 3 5 0 . 0 - 2 9 . 9
2 6 . 6 - 2 2 . 2 2 34 . 4 2 1 2 . 2 + 1 8 3 . 1 1 2 0 . 8 - 1 0 0 . 7 1 2 0 . 0 1 9 . 3 + 2 0 2 . 4
2 , 2 1 4 . 7 - 1 , 845 . 4 1 , 8 0 0 . 9
C a l cu l at e S t o rage Vo l ume
Max . Ice Bui l dup = 1 , 2 9 6 . 2 x 1 0 6 Btu x 1 4
!bB t u
= 9 . 00 1 x 1 0 6 l b o f i c e
Vo l ume = 9 . 0 0 1 x 1 0 6 l b x 3;t�
b = 243 , 300 ft 3 ( as sumes 37 l b i c e / ft 3 )
Annua l Ene rgy Us e
Heat ing @ cor o f 3 . 5 = 2 , 4 5 8 X 1 0 6 ��u X 3�
5 X 1;4��0 = 2 , 3 66 X 1 0 6 ��u
St orage Los s e s 1 0 6 B tu
( 3 �ii o f Cum . )
6 . 8 1 6 . 9 2 6 . 0 34 . 5 38 . 9 3 5 . 7 3 1 . 0 24 . 5 1 1 . 8
0 . 9 -
Coo l i ng @ Pump i n g C o s t = l OHP x . 74 6 Kw x 8 7 6 01 1r x 1 1 , 5 0 0 x 34 1 3 B tu _
6 B t u Hp Yr 34 1 3 Kw - h r - 7 5 1 . 5 x 1 0
Y r
To t a l HVAC Ene rgy U s e = 2 • 366 x 1 0 6 + 7 5 1 . 5 x 1 0 6 + 1 , 5 2 0 x 1 0 6 * Btu 4 0 , 5 0 0
= 1 1 4 , 5 1 0 S f
* Fan energy us c .
-....] 0\
APPEND I X B
HVAC ENERGY USE TABLES
"'-J 00
Table B - 1 . HVAC energy us e o f dual duct in 40 , 5 00 ft 2 o ffi ce bui lding
G as Heat and Electric Cooling
1 . Bas e 2 . Economi z er 3 . Exhaust Air Heat Recovery 4 . Re s et Control s 5 . Improved Chi ller E fficiency 6 . Doub l e Bundl e 7 . Solar Heat 8 . ACES 9 . Total Energy
10 . 2 & 4 1 1 . 3 & 4 1 2 . 4 & 6 1 3 . 4 & 7 14 . 3 , 4 & 6 15 . 3 ' 4 & 7 16 . 3 ' 4 & 8 1 7 . 3 , 4 & 9 1 8 . 3 ' 4 ' 7 & 9
Heat ing Energy
Us e a:
1 7 2 , 000
1 5 0 , 000 1 36 , 000 1 7 2 , 000
85 , 000 138 , 000 1 3 8 , 000
136 , 000 8 1 , 0 00
120 , 000 1 1 1 , 000
64 , 000 6 1 , 000 5 8 , 000
C ooling Energy
U s eb
1 22 , 000
1 2 2 , 000 70 , 000
1 15 , 000 1 2 2 , 000 1 2 2 , 000
1 9 , 000
66 , 000 69 , 000 70 , 000 70 , 000 69 , 000 69 , 000 19 , 000
Fan Energy
U s e
( Btu/ ft 2 -yr) 32 , 000
38 , 000 32 , 000 32 , 000 32 , 000 32 , 000 3 2 , 000
32 , 000 38 , 000 32 , 000 32 , 000 38 , 000 38 , 000 38 , 000
Total Energy
U s e
326 , 000
3 1 0 , 000 238 , 000 319 , 000 239 , 000 292 , 000 189 , 000 340 , 000 234 , 0 00 1 8 8 , 000 223 , 000 2 14 , 000 1 7 1 , 0 00 168 , 000 1 1 5 , 000 158 , 000 139 , 330
Normali z ed Energy
U s e F actorc
2 . 3 1
2 . 1 9 1 . 68 2 . 2 5 1 . 6 7 2 . 06 1 . 3 3 2 . 4 1 1 . 65 1 . 3 3 1 . 5 7 1 . 5 1 1 . 1 9 1 . 1 8 0 . 8 1 1 . 1 2 0 . 9 8
aTo approximate heat ing energy us e for en ergy other than gas , mult ip l y by . 964 for oil and 2 . 5 72 for e l ectricity .
bTo approx imat e coo l ing energy us e for gas cooling , mult ip ly by 1 . 943 . cFactor i s defined as rat io of actua l energy us e for heat ing and coo l ing to energy demanded
to meet l oads.
Tab l e B - 2 . HVAC energy us e o f s ing l e z one/fan coi l in 40 , 5 00 ft 2 o ffice bui l d ing
Normal i z ed
G as Heat and E l e ctric Coo l ing
Heat ing Energll
U s e
C oo l ing Fan Energb Energy
U s e Us e
Total Energy Energy U s e
U s e Factor a
- - - - - - - - - - - - - - - - - - - - - - - - ( Btu/ ft 2 - yr) - - - - - - - - - - - - - - - - - - - - - - - -
1 . B a s e 1 0 9 , 000 69 , 000 3 2 , 00 0 2 1 0 , 000 1 . 4 8 2 . Economi z e r 1 0 9 , 000 68 , 000 32 , 000 2 09 , 000 1 . 4 8 3 . Exh aust Air Heat Recovery 8 3 , 0 0 0 68 , 0 00 38 , 0 0 0 1 8 9 , 0 0 0 1 . 34 4 . I mproved C h i l l er Effi c i ency 1 0 9 , 000 65 , 000 3 2 , 0 0 0 206 , 000 1 . 4 6 5 . Doub l e Bund l e 9 7 , 000 69 , 000 3 2 , 00 0 1 98 , 00 0 1 . 40 6 . So l ar Heat 8 7 , 0 00 6 9 , 000 32 , 000 1 8 8 , 000 1 . 3 3 7 . AC ES (w/ 3 ) 5 7 , 0 00 2 1 , 0 00 3 2 , 000 1 1 0 , 0 00 0 . 7 8 8 . Total Energy 1 8 4 , 000 1 . 3 0 9 . 3 & 5 7 1 , 00 0 68 , 000 3 8 , 000 1 7 7 , 00 0 1 . 2 5
1 0 . 3 & 6 63 , 000 68 , 00 0 38 , 000 1 6 9 , 000 1 . 1 9 1 1 . 3 & 8 1 5 9 , 000 1 . 1 2 1 2 . 3 ' 6 & 8 1 3 8 , 000 0 . 9 8
aTo approximate heat ing energy u s e for energy other than gas , mu l t ip l y by . 9 64 for o i l and 2 . 5 72 for e l ectri city .
bTo approximat e coo l ing energy u s e for gas cool ing , mul t ip l y by 1 . 943 .
aFactor i s d efined as rat io of actua l energy u s e for heat ing and coo l ing to energy demanded to meet l o ads .
-...J 1.0
Table B - 3 . HVAC energy us e o f VAV in 40 , 5 0 0 ft 2 offi ce bui lding
Normal i z ed Heat ing Coo l ing Fan Total Energy
Gas Heat and Energy Energb Energy Energy Us e E l e ctric Coo l ing Us ea Us e Us e Us e FactorC
- - - - - - - - - - - - - - - - - - - - - - - - - (Btu/ft 2 -yr) - - - - - - - - - - - - - - - - - - - - - - -
1 · Bas e 85 , 0 00 86 , 000 1 3 , 000 1 8 4 , 000 1 . 3 0 2 . Economi z er
d 85 , 00 0 7 1 , 000 1 3 , 000 1 6 9 , 000 1 . 1 9
3 . Exhaus t Air Heat Recovery - - - - -4 . Improved Ch i l l er Efficiency 85 , 0 0 0 8 1 , 00 0 1 3 , 000 1 7 9 , 000 1 . 2 6 5 . Doub l e Bund le 48 , 000 86 , 000 1 3 , 000 1 4 7 , 0 0 0 1 . 0 4 6 . So l ar Heat 5 8 , 0 00 86 , 000 1 3 , 0 00 1 5 7 , 00 0 1 . 1 1 7 . Total Energy - - - 1 9 8 , 000 1 . 4 0 8 . Vari ab l e Sp eed Fan 85 , 0 00 86 , 000 2 , 000 1 7 3 , 000 1 . 2 2 9 . 2 & 5 63 , 000 7 1 , 0 00 1 3 , 000 1 4 7 , 000 1 . 0 4
1 0 . 5 & 8 4 8 , 00 0 86 , 000 2 , 0 00 1 2 6 , 00 0 0 . 8 9 � 1 1 . 6 & 8 5 8 , 0 00 8 6 , 000 2 , 0 00 1 3 6 , 000 0 . 96 1 2 . 2 , 5 & 8 65 , 000 7 1 , 00 0 2 , 0 00 1 3 8 , 000 0 . 9 6 1 3 . 2 , 6 & 8 5 8 , 0 00 7 1 , 00 0 2 , 0 00 1 3 1 , 00 0 0 . 9 3 1 4 . 2 & 6 5 8 , 0 00 7 1 , 000 1 3 , 000 1 4 2 , 00 0 1 . 0 0
aTo approximat e heat ing energy us e for energy other than gas , mu l t ipl y by . 9 64 for o i l and 2 . 5 7 2 for e l ectricity .
bTo approximat e coo l ing energy us e for gas coo l ing , mul tip ly by 1 . 9 4 3 .
aFactor i s de fined as rat io of actua l energy use for heat ing and cool ing to energy demanded to meet load s .
d Heat recovery increased energy us e when amb ient temp erature was between l 0 ° F and 7 5 ° F .
Tab l e B - 4 . HVAC energy us e of s ing l e zone /VAV in 100 , 000 ft 2 hospital
G as Heat and E l e ctric Coo l ing
Heat ing Energti Use
Coo l ing Energ
h Use
Fan Total Energy Energy
Us e Use
Normal i z ed Energy
Us e F actor0
- - - - - - - - - - - - - - - - - - - - - - - - - (Btu/ ft 2 -yr) - - - - - - - - - - - - - - - - - - - - - - -
1 . Base 230 , 000 157 , 000 2 1 , 000 408 , 000 1 . 75 2 . Exhaust Air Heat Recovery 1 74 , 000 152 , 000 24 , 000 350 , 000 1 . 5 0 3 . Improved Ch il l er Efficiency 230 , 000 149 , 000 2 1 , 000 400 , 000 1 . 7 1 4 . Doub l e Bund le 200 , 000 157 , 000 2 1 , 000 378 , 000 1 . 62 5 . So l ar Heat 208 , 000 1 5 7 , 000 2 1 , 000 386 , 000 1 . 65 6 . Total Energy 330 , 000 1 . 4 1 7 . Variab le Sp eed Fan 230 , 000 1 5 7 , 000 16 , 000 403 , 000 1 . 73 8 . 2 & 4 1 5 7 , 000 1 5 2 , 000 24 , 000 333 , 000 1 . 4 3 9 . 2 & 6 272 , 000 1 . 1 6
10 . 2 , 5 & 6 25 7 , 000 1 . 1 0
aTo approx imat e heat ing energy us e for energy other than gas , mul t iply by . 9 64 for o i l and 2 . 5 7 2 for e l ectric ity .
bTo approximate cool ing energy us e for gas cool ing , mu l t ip l y by 1 . 943 .
°Factor is defined as rat io of actua l energy use for heat ing and coo l ing to energy demanded to meet loads .
00 1--'
T ab l e B- 5 . HVAC en ergy us e o f s ing l e z one/ fan coi l in 1 0 0 , 000 ft 2 hosp i t a l
G as Heat and E l ectric Coo l ing
Heat ing Ene rgy
U s e a
Coo l ing Energb
Us e
Fan Tot a l Energy Energy
Us e Use Us e
Norma l i z ed Energy
U s e F actorc
- - - - - - - - - - - - - - - - - - - - - - - - ( B tu/ ft 2 - yr) - - - - - - - - - - - - - - - - - - - - - - - - -
1 . Bas e 243 , 000 1 4 9 , 000 31 , 000 4 2 3 , 000 1 . 8 1 2 . E xhaust A i r Heat Recovery 1 8 7 , 0 00 1 4 4 , 000 34 , 000 365 , 00 0 1 . 5 6 3 . Improved Chi l l er E ffic i ency 2 4 3 , 0 0 0 1 4 1 , 0 00 3 1 , 0 00 4 1 5 , 00 0 1 . 78 4 . Doub l e Bund l e 2 1 9 , 0 0 0 1 4 9 , 000 3 1 , 0 00 3 9 9 , 000 1 . 7 1 5 . So l ar Heat 2 2 1 , 0 00 1 4 9 , 000 3 1 , 0 00 4 0 1 , 000 . 1 . 7 2 6 . ACES (W/ 2 ) 1 1 2 , 0 00 5 3 , 0 00 34 , 000 1 9 9 , 000 0 . 8 5 7 . Tot a l Energy 342 , 000 1 . 46 8 . 2 & 4 1 7 7 , 0 00 1 44 , 000 34 , 000 35 5 , 000 1 . 5 2 9 . 2 & 7 2 6 9 , 0 0 0 1 . 1 5
1 0 . 2 ' 5 & 7 2 5 8 , 00 0 1 . 1 0
aTo approx imat e heat ing energy use for energy other than gas , mul tiply by . 964 for o i l and 2 . 5 7 2 for el ect ricity .
bTo approximate coo l ing energy u s e for gas coo l ing , mul t ip l y by 1 . 943 .
cFactor i s defined as ratio o f actual energy use for heat ing and coo l ing to en ergy demanded to meet l o ad s .
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APPEND I X C
HVAC ENERGY USE , CAP I TAL COSTS
AND PAYOUT TAB LES
00 �
Tab l e C - 1 . HVAC energy us e , capital cost and payout s of s ing l e zone/ fan c o i l in 40 , 5 00 ft 2 office bui l d ing
Gas Heat and HVAC Retro fit Payout E l ectric Coo l ing Energy U s e Capital Cost (years)
1 . Bas e 64 . 5%a 89 . 9%b N/A 2 . Economi z er 64 . 2% 9 1 . 2% 34 . 5 3 . Exhaus t Air Heat Recovery 5 8 . 0% 9 2 . 2% 6 . 3 4 . Improved Chi l l er E fficiency 6 3 . 3% 9 1 . 0% 7 . 5 5 . Doub l e Bund l e 60 . 6% 9 5 . 7% 2 2 . 3 6 . So l ar Heat 5 7 . 6% 1 72 . 9% 1 5 1 . 1 7 . ACES (with 3) 33 . 8% 439 . 6% 1 6 3 . 5 8 . Total Energy 56 . 3% 1 5 4 . 8% 369 . 3 9 . 3 & 5 54 . 2% 9 8 . 0% 1 2 . 9
1 0 . 3 & 6 5 1 . 8% 1 75 . 2% 92 . 1 1 1 . 3 & 8 48 . 6% 1 57 . 1 % 48 . 1
. 1 2 . 3 , 6 & 8 42 . 5% 2 3 0 . 0% 8 7 . 5
aBas e ene rgy us e is 326 , 000 Btu/ ft 2 -yr .
bBas e capit al cost is $2 70 , 000 .
Original D e s i gn Payout (years)
0 . 0
1 4 . 3
3 . 5
Tab l e C - 2 . HVAC energy, use , capital co s t and payout s of VAV in 40 , 500 ft 2 office bui lding
Gas Heat and E l ectric Cool ing
1 . Bas e 2 . E conomi z er 3 . · Improved Chi l l er E fficiency 4 . Doub l e Bund l e 5 . So l ar Heat 6 . Tota l Energy 7 . Vari ab l e Spe ed Fan 8 . 2 & 4 9 . 4 & 7
1 0 . 5 & 7 1 1 . 2 , 4 & 7 1 3 . 2 , 5 & 7
HVAC Energy U s e
5 6 . 3%a 5 2 . 1 % 54 . 7% 44 . 7% 48 . 0% 60 . 7% 5 2 . 9% 45 . 1 % 4 1 . 3% 44 . 6% 42 . 3% 40 . 4%
aBas e ene rgy use is 32 6 , 000 Btu/ ft 2 -yr .
bBase capital cost i s $2 70 , 000 .
cHighe r ope rat ing c ost .
Capital Cost
1 0 3 . 3%b
1 04 . 6% 1 04 . 4% 1 0 9 . 1 % 1 73 . 8% 1 5 8 . 1 % 1 0 5 . 2% 1 1 0 . 4% 1 1 0 . 6% 1 75 . 7% 1 1 1 . 9% 1 7 7 . 0%
Retro fit Payout (years)
N/A 1 . 9 6 . 0 6 . 8
1 1 5 . 5
c 3 . 8 6 . 1 5 . 7
69 . 4 5 . 6
43 . 6
Original Design Payout (year s )
4 . 3
4 . 5 4 . 2
4 . 4 00 tn
Tab l e C - 3 . HVAC energy use , capital cost and payouts o f singl e z one/VAV in 100 , 000 ft 2 hospit al
Gas Heat and HVAC E l e ctric Coo l ing Energy Use
1 . Bas e 96 . 5%a
2 . Exhaust Air Heat Recovery 82 . 8% 3 . _ Improved Chi 1 1 er E fficiency 94 . 6% 4 . Doub l e Bund l e 89 . 4% 5 . So l ar Heat 9 1 . 3% 6 . Total Energy 7 8 . 1% 7 . Variab l e Spe ed Fan 9 5 . 3% 8 . 2 & 4 7 8 . 8% 9 . 2 & 6 64 . 4%
1 0 . 2 , 5 & 6 60 . 8%
aBase ene rgy us e is 42 3 , 000 Bt u/ ft 2 -yr .
bBase c apit al cost is $ 1 , 1 19 , 000 .
cHi ghe r ope rat ing c ost .
Capital Cost
96 . 4%b 99 . 1 % 9 7 . 3%
1 0 2 . 3% 1 3 1 . 5 % 1 34 . 0%
97 . 1 % 1 0 5 . 0% 1 36 . 7% 1 7 1 . 8 %
Retrofit Payout (years)
N/A 3 . 4 4 . 1
14 . 5 1 1 5 . 6
c 4 . 8 8 . 3
28 . 9 4 3 . 3
Original Design Payout (years)
0 . 0
7 . 7
0 . 0
00 Q\
Tab l e C- 4 . Payout vs . fue l combination for cons ervation measures for sing l e zone/ fan coi l in 40 , 500 ft 2 office bui lding
Payout (Years)
E l ectric Gas Heat O i l Heat Heat
& & & E l ectri c E l ectric E l ectric Cool ing Coo l ing Coo l ing
2 . E conomi z er 34 . 5 34 . 5 34 . 5 3 . Exhaus t Air Heat Recovery 6 . 3 3 . 0 0 . 9 4 . Improved Chi l l er E fficiency 7 . 5 7 . 5 7 . 5 5 . Doub l e Bund l e 2 2 . 3 . 1 3 . 0 4 . 3 6 . So l ar Heat 15 1 . 1 85 . 4 2 9 . 3 7 . ACES 163 . 5 8 7 . 2 2 9 . 0 8 . Tota l Energy Sys tem 369 . 3 2 7 . 9 26 . 4 9 . 3 & 5 1 2 . 9 6 . 4 2 . 0
1 0 . 3 & 6 9 2 . 1 48 . 3 1 5 . 3 1 1 . 3 & 8 48 . 1 1 9 . 0 5 . 3 1 2 . 3 , 6 & 8 8 7 . 5 39 . 4 1 1 . 7
-aHigher operat ing co st .
Gas Heat &
Gas Coo l ing
34 . 5 6 . 3
1 5 1 . 1 2 7 7 . 4
a 00 -.....]
9 2 . 1 1 7 1 . 1 206 . 1
Tab l e C - 5 . Payout vs . fue l comb inat ion for cons ervation measures for VAV in 40 , 5 0 0 ft 2 offic e bui l ding
Payout (Years )
E l ectric Gas Heat Oi l Heat Heat
& & & E l ectri c E l ectric E l ectric Coo l ing Coo l ing Coo l ing
2 . Economi z er 1 . 9 1 . 9 1 . 9 4 . Improved Chi l l er E.fficiency 6 . 0 6 . 0 6 . 0 5 . Doub l e Bund l e 6 . 8 4 . 0 1 . 4 6 . S o l ar Heat 1 1 5 . 5 68 . 6 23 . 4 7 . Tota l Energy System a 147 . 7 8 . 0 8 . Vari ab l e Speed F ans 3 . 8 3 . 8 3 . 8 9 . 2 & 5 6 . 1 4 . 7 2 . 2
1 0 . 2 & 6 5 8 . 8 4 3 . 8 1 9 . 8 1 1 . 5 & 8 5 . 7 4 . 0 1 . 6 1 2 . 6 & 8 69 . 4 49 . 6 2 1 . 0 1 3 . 2 , 5 & 8 5 . 6 4 . 7 2 . 6 1 4 . 2 , 6 & 8 4 3 . 6 34 . 9 1 8 . 0
-aHigher operating cos t .
Gas Heat &
Gas Coo l ing
1 . 8
1 1 5 . 5 a
3 . 8 - 00
5 7 . 1 (XI
69 . 4
42 . 7
Tab l e C -6 . Payout vs . fue l combination for cons ervat ion measures for s ing l e zone/VAV in 100 , 000 ft 2 ho spital
2 . Exhaus t Air Heat Recovery 3 . Improved Chi l l er E ffi ciency_ 4 . Doub l e Bundl e 5 . S o l ar Heat 7 . Total Energy 8 . 2 & 4 9 . 2 & 7
1 0 . 2 ' 5 & 7 1 1 . Variab l e Speed F ans
aH . h · 1g er operat1ng cost .
Gas Heat &
E l ectric Coo l ing
3 . 4 4 . 1
1 4 . 5 1 1 5 . 6
a 8 . 3
2 8 . 9 4 3 . 3
4 . 8
Payout (Years )
E l e ctric Oil Heat Heat
& & E l ectric E l ectric Coo l ing Cool ing
2 . 0 0 . 8 4 . 1 4 . 1 8 . 4 3 . 1
67 . 3 2 4 . 5 16 . 7 3 . 3
4 . 9 1 . 8 1 1 . 1 3 . 1 1 9 . 0 5 . 7
4 . 8 4 . 8
Gas Heat &
Gas Coo l ing
3 . 5
1 1 5 . 6 a
64 . 0 00
7 8 . 6 1.0
4 . 8
VITA
Robe rt Edward Lyman, Jr . , was born in Birmin gham, Al ab ama, on
March 22 , 195 1 . He att ended pub l i c scho o l s in that city and in Knoxvi l l e ,
Tenne ssee . He was graduate d from Farragut Hi gh Schoo l in May 1969 . In
June 1969 he ent e re d the Univers ity o f Tennes s ee and receive d a Bachelor
o f Scien ce de gree in Mechanical Enginee ring in June 19 74 . He also
comp l eted a co -op program , as part of his de gree , workin g for Great Dane
Trai l e rs , In c . , in Savann ah , Geo rgia , in the Res earch and Deve lopment
Group .
In July 1974 he b egan emp loyment with Texaco , Inc . , in Hous ton ,
Texas , as a ut i l ities enginee r in the en gineering dep artment . In that
capacity , he parti cipated in the de s ign an d cons t ruct i on o f me chani cal
syst ems in new refineries and pet ro chemi ca l p l ant s .
In June 19 7 7 he reques t e d an d re ce ive d an educ at ional leave o f
abs en ce . He ent e re d the Graduate Schoo l at the Unive rs ity o f Tenne s see
and received th e Mas ter of Science de gree in mechanical enginee ring in
March 19 79 . His g raduate studies were support ed by a Graduat e Re s e arch
As sistant ship with the Ene rgy Divi s ion o f Oak Ri dge Nat ional Lab oratory .
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