energ consumption and the potential energy savings in Hellenic office buildings

8/7/2019 energ consumption and the potential energy savings in Hellenic office buildings

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G.N. Spyropoulos, C.A. Balaras / Energy and Buildings 43 (2011) 770778 771

by space heating and other heat uses (73% in 2000 projected to

decrease to 62% in 2030), 16% for electric equipment (projected to

increase to 27% in 2030), 6% for cooling (projected to increase to

9.3% in 2030) and 5% for lighting (projected to further decrease in

2030 as a result of widespread penetration of efficient lighting).

Electrical energy consumption in NR buildings exhibits a constant

increase over the years due to the extensive use of HVAC and office

equipment (especially electronic devices and computers) and is

expected to increase from 42% in 2005 to almost 50% of the total

energy consumption in 2030.

InGreece, thebuildingsector consumed 7.6Mtoeor 35.4%of the

final energy consumption in 2006 compared to 3.8 Mtoe or 26.1%

in 1990 [1]. The Hellenic residential buildings, account for about

25.7% of the total final energy consumption and consume 32.7% of

the total electricity generated in the country and 21.5% of the total

thermal energy [4]. The Hellenic NR buildings account for 9.7% of

the total final energy consumption and consume 29.7% of the total

electricity generated in the country [5].

The need to gain some insight and investigate the potential for

energy conservation in Hellenic office and commercial buildings is

also in line with the ongoing efforts to comply with the European

Directive on the energy performance of buildings EPBD (2002/91)

and its national adaptation as part of the L.3661/19.5.2008 and

the Common Ministerial Decision 5825/9.4.2010 that specifies thetechnical regulation(KENAK). Moreover, the European Directiveon

energy end-use efficiency and energy services (2006/32/EC) neces-

sitates from all EU member states to adopt measures in order to

limit the carbon dioxide emissions as well to achieve an overall

national indicative energy savings target of 9% by 2017.

Most of our knowledge and available data on the energy con-

sumption and the assessment of energy conservation measures is

available for residential buildings, while even fundamental knowl-

edge of the NR building stock and its energy performance is rather

limited [5,6]. Office buildings are classified among the buildings

withthe highest energy consumption.The annual energy consump-

tion in European office buildings varies from 100 to 1000 kWh/m2

of conditioned floor space [7], depending on location, construction,

HVAC and lighting installations, use and type of office equipment,operating schedules, etc. Typical annual total energy consump-

tion in Hellenic office buildingsaverages 187 kWh/m2 [8]. In China,

energyuse rangesfrom 70 to 300 kWh/m2 in large scale (20,000 m2

or more) public NR buildings with centralised HVAC systems [9].

Mostdetaileddata is available forbuildings in theUnitedStates. The

average energyuse intensity in U.S. office buildings is 293kWh/m2

[10]. Detailed information on the energy consumption of represen-

tative U.S.commercial buildingsis collectedby the U.S.Commercial

Buildings Energy Consumption Survey [11]. According to the most

recent published data for 2003, the annual gross energy inten-

sity for office buildings is in the range of 220360 kWh/m2 for

the different US climatic zones. Among the different office sub-

categories, banks and other financial offices are the most energy

intensive averaging 301 kWh/m2

and the highest electricity con-sumptionintensities reachinga median of 239kWh/m2,witha25th

percentile building level electricity intensity of 156 kWh/m2 and a

75th percentile of 318kWh/m2. However, similar data for Euro-

pean buildings is very limited and there has been no published

data on the energy consumption of buildings used in the banking

sector. This paper provides relevant data on the characteristics of

the Hellenic commercial/office buildings used in the banking sec-

toras financial offices and contributes with newdata on the energy

performance for this specific end-use of NR buildings.

2. Methodology

Themethodologyto investigate the energybehaviorof the bank

branches and to collect, classify and process the necessary data,

included the following major steps:

Energy consumption data: Electricity bills or utility records from

39 bank branches throughout the country, over a period of 6

years, were collected and classified. The classification was per-

formed for the different national climatic zones. Practically all

of the bank branches have only electrical energy consumption;

only one branch had also a low thermal energy consumption for

heating. Selection of typical branches: A representative sample of 11 typ-

ical branches was selected for an in depth analysis andstudy. The

criteria for selecting the specific branches included: location for

covering the different national climatic zones, completeness of

available data and similar functions of bank services (for example

similar operating hours). Energy audit: An in-depth investigation of the selected 11 typ-

ical branches included an energy audit to collect the necessary

data, i.e. architectural drawings along with specifications for the

buildings envelope construction, the floor area and volume, all

electromechanical (E/M) installations for the different end-uses

such as the HVAC system, the lighting system, the electrical

equipment, etc. Benchmarking: Based on the collected data and the results of

the analysis, energy related indicators were estimated. These

indicators for the 9 branches include: (a) the energy consump-

tion per unit area (kWh/m2) and (b) the energy consumption

per unit volume (kWh/m3). For the sample of the 11 typical

branches the additional findings include: (a) the breakdown of

final energy consumption, (b) the installed power per unit floor

area (W/m2) for lighting, equipment and HVAC systems and

(c) the energy intensity expressed as energy consumption per

employee (kWh/emp). Energy conservationpotential: Several energy conservationmea-

sures (ECMs) were evaluated for the 11 typical branches. Costeffectivenessof ECMs:The financialevaluation(where appli-

cable) of different ECMs was based on the Simple PayBack Period

(PBP) and the Net Present Value (NPV). Environmental impact: The environmental impact assessment

wasbased on estimatedCO2 emissionsbefore andafter theimple-

mentation of thevariousECMs. Theconversionbetweenelectrical

energy consumption and CO2 emissions was based on specific

national average conversion factors of primary energy consump-

tion for power generation (0.950 kg CO2/kWhel).

Since many of the bank branches often consist of several levels

(ground floor, basement, and mezzanine) it is necessary to clar-

ify some of the assumptions. The energy audits of each branch

revealed that only the working area (ground floor) of each branch

is air-conditioned. Therefore, since the vast majority of both the

equipment and HVAC systems are located on the ground level,

both the unit floor area (m2) and unit volume (m3) in the energy

related indicators (kWh/m2, kWh/m3) refer to the working (air-conditioned) area which can be regarded as representative for the

energy performance of each branch. Since the basement (where

it exists) and the mezzanine (where it exists) are used as ancil-

lary spaces, but both have an installed lighting system, the relative

indicators for lighting refer to the total floor area (ground floor,

basement, mezzanine) of each branch, which usually differs from

the air-conditioning area. The installed power per unit floor area

(W/m2) of the equipment refers to the ground floor area and that

of HVAC refers to the working (air-conditioned) floor area.

3. Energy consumption

Greece is divided in four climatic zones, namely A, B, C and D,

basedon heating degreedays(HDD fora base temperatureof 18

C):


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772 G.N. Spyropoulos, C.A. Balaras / Energy and Buildings 43 (2011) 770778

Table

1

Generalcharacteristicsandenergyconsumptionoftheinvestigated11typicalbankbranches.

Bankbranchcode

Interiorspacesize

D

escriptionofexternalfacadeconstruction(area,m2)

Lengthofext.

marqueesign(m)

Annualenergy

consumption

Groundfloor

Basement

Mezzanine

Transparentelements

Opaqueelements

Area(m2)

Volum

e(m3)

Area(m2)

Area(m2)

(kWh/m2)

(kWh/m3)

A-1

137

425

90

In

sulateddoubleglazing(15)

Insulateddoub

lebrickwall

(61)

a

297.6

96.0

A-2

92

284

25

In


Insulateddoub

lebrickwall&

concretecolum

ns(88)

a

281.2

89.6

A-3

70

231

73

71

Singleglazing10mm(46)

Concretecolum

ns(24)

23

406.6

123.2

B-1

105

436

55

25

In


Concretecolum

ns(25)

16

462.9

111.6

B-2

173

770

68

70


Concretecolum

ns(23)

12

290.3

65.2

B-3

155

581


Concretecolum

ns(26)

11

263.0

70.1

B-4

180

567

In


Insulateddoub

lebrickwall&

concretecolum

ns(68)

21

304.6

96.7

B-5

98

362

71


Concretecolum

ns(29)

17

307.0

83.0

C-1

115

368

105

In


Insulateddoub

lebrickwall&

concretecolum

ns(51)

16

419.5

131.1

C-2

119

375

121

In


Concretecolum

ns(7)

7

461.7

146.6

D-1

95

299

95

In


Concretecolum

ns(6)

6

308.2b

104.2

Average

345.7

101.6

aA-1andA-2brancheshavenoexternalmarqueesignsincetheyarehousedintraditionalbuild

ings(i.e.noexternalsignsareallowed).

b

EnergyconsumptionofD-1includesboththe

electricalenergyconsumption(205.2kWh/m2)andthethermalenergyconsumption(103kWh/m

2).

zone A (6011100 HDD18 C), zone B (11011600 HDD18 C), zone

C (16012200 HDD18 C) and zone D (22012620 HDD18 C). The

investigated 11 typical bank branches are classified in four groups

according to the corresponding four climatic zones where they are

located.The basiccharacteristicsof eachbank branch are presented

in Table 1. The code name of each bank branch first identifies the

climaticzone (A,B, C orD) followedby a sequential numerical value.

For zone A, monthly energy consumption data over a six year

period for 7 branches were collected and analyzed. The average

monthly energy consumption was 25.6 kWh/m2, while the maxi-

mum and minimum values were 39.3kWh/m2 and 14.9kWh/m2,

respectively.On an annualbasis, 50%of thebranches havean energy

consumption lower than 300kWh/m2, while for 34% of them it

ranges between 350 and 407 kWh/m2. The evolution of the aver-

age annual energy consumption per unit floor area over the six

year period is illustrated in Fig. 1 and reached 316kWh/m2 (300 kg

CO2/m2) in 2007.

Following an in-depth analysis of the data from the energy

audit and details of the installed E/M equipment for lighting,

office and electronic equipment, and HVAC systems, it was pos-

sible to estimate the energy consumption breakdown for the

different end-uses. The estimated annual energy consumption for

HVAC ranged between 87.9 and 204.3kWh/m2, while the average

installed power was 53.8W/m2. On average, the HVAC contribu-tion to the total final energy consumption is 49.0% (of which 62.4%

for cooling and 37.6% for heating), lighting follows with 32.5% (of

which 62% for indoor space lighting, 22% for the external marquee

sign and 16% for security night lighting) and office and electronic

equipment corresponds to 18.5%.

The analysis revealed that artificial lighting also contributes

significantly to the total energy consumption mainly due to the

operationof the large external marquee sign with thebanks name.

However, even excluding the use of this sign from the energy

balance, the lighting energy consumption is higher compared to

other office buildings. The estimated annual energy consumption

for lighting ranged between 44.5 and 80.9 kWh/m2 for branch A-3,

which is equipped with a largest external marquee sign (Table 1).

The installed power for artificial lighting was estimated between28W/m2 (forbranchA-1)and36W/m2 (forbranchA-3)or21W/m2

excluding the external marquee sign.

The annual energy consumption for office and electronic equip-

mentranged between 48.8and 70.7kWh/m2. Thedesktop personal

computers and telecommunication equipment are the main end

uses, with an annual energy consumption ranging between 24.0

and 31.6kWh/m2. The automated teller machine (ATM) follows

with an annual energy consumption between 12 kWh/m2 and

23 kWh/m2 mainly due to its continuous operation throughout the

9473 76

100

212230

270296

263279

352

407

199 194 183 191

316293

0

100

200

300

400

500

200720062005200420032002

kWh/m 2

Fig. 1. Evolution of annual energy consumption (kWh/m2) over a six year period

(20022007) of 7 branches in climatic zone A. The numerical values indicate the

minimum, average (square) and maximum energy consumption.


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110137 144 151

220 230

328

404386

336

422

463

214227 221 226

336316

0

100

200

300

400

500

200720062005200420032002

kWh/m2


(20022007) of 18 branches in climatic zone B. The numerical values indicate the


year. The average installed power for office and electronic equip-

ment was 85.5 W/m2.

For zone B, monthly energy consumption data over a six year

period for 18 branches were collected and analyzed. The average

monthly energy consumption was 29.6 kWh/m2, while the max-

imum and minimum values were 59 kWh/m2 and 12.9 kWh/m2,respectively. The evolution of the average annual energy consump-

tion perunit floor area over thesix year periodis illustrated in Fig.2

and reached 336kWhm/m2 (319kg CO2/m2) in2007.On anannual

basis, 33% of the branches have an energy consumption between

200and 300 kWh/m2, 22%between300 and350kWh/m2, whilefor

17% of them it ranges between 400 and 500kWh/m2 (maximum

463kWh/m2).

The energy consumption breakdown for the different end-uses

in the bank branches of zone B was based on an in depth analysis

of 5 branches, where data was available. Again, the HVAC system

is the major energy consumer. On average, the HVAC contribution

to the total final energy consumption is 47.0% (of which 58.8% for

coolingand 41.2% for heating), lightingfollows with37.2%(of which

40%forindoor spacelighting, 49% fortheexternalmarqueesignand11% for security night lighting) and office and electronic equipment

corresponds to 15.8%.

TheHVAC systemcovers both thecooling and the heating needs

of each branch in theclimatic zone B duringthe year. Theestimated

annual energy consumption for HVAC ranged between 107.0 and

250.6 kWh/m2, while the average installed power was 77.8 W/m2.

The percentage for cooling to the total final energy consumption

rangedbetween 18 and 31%and forheating 1821%. Theestimated

annual energy consumption for lighting ranged between 76.0 and

118.7 kWh/m2 for branch B-4, which is equipped with the largest

external marquee sign (Table 1) that represents 49% of the energy

consumption for lighting. The installed power for artificial lighting

was estimated between 28.4 W/m2 (for branch B-2) to 51.9 W/m2

(for branch B-4) or 31.5 W/m2

excluding the external marquee sign.The annual energy consumption for office andelectronic equip-

mentranged between 39.6and 71.0kWh/m2. The desktop personal

computers and telecommunication equipment have an annual

energy consumption between 14.6 and 24.3kWh/m2 and the ATMs

range between 6.8 and 11.0 kWh/m2. The installed power for office

and electronic equipment ranged between 30.9 and 87W/m2 with

an average of 55.6 W/m2.

For zone C, monthly energy consumption data over a six year

period for 10 branches were collected and analyzed. All of the

branches in this sample operate from 07:15 to 15:30, except for

two of them that have an extended daily operation for four more

hours. The average monthly energy consumption was 33 kWh/m2,

while the maximum and minimum values were 45.2 kWh/m2 and

20.8kWh/m2

, respectively. The evolution of the average annual

152153 145145

240 247

315

408 393413

469497

234

302283 290

391

362

0

100

200

300

400

500

600

200720062005200420032002

kWh/m 2


(20022007) of 10 branches in climatic zone C. The numerical values indicate the


energy consumption per unit floor area over the six year period is

illustrated in Fig. 3 and reached 391 kWhm/m2 (371kg CO2/m2) in

2007. On an annual basis, 40% of the branches have an energy con-

sumption between 200 and 300kWh/m2, while for 50% of them it

ranges between 400 and 500kWh/m2.

On average, the HVAC contribution to the total final energyconsumption is 47.5% (of which 42.5% for cooling and 57.5% for

heating), lighting follows with 34.6% (of which 51% for indoor

space lighting, 35% for the external marquee sign and 14% for

security night lighting) and office and electronic equipment cor-

responds to 17.9%. The estimated annual energy consumption for

HVAC rangedbetween 202.0 and216.5kWh/m2, while the average

installed power was 138 W/m2. The estimated annual energy con-

sumption for lighting averaged 77.4 kWh/m2, while the installed

power for artificial lightingwas estimated between 36.8W/m2 (for

branch C-1) and 24 W/m2 (for branch C-2). Excluding the external

marquee sign, the installed power for lighting drops to 26.4 and

19.5W/m2 , respectively.

The annual energy consumption for office and electronic equip-

mentranged between 64.7and 94.3kWh/m2. Thedesktop personalcomputers and telecommunication equipment have an annual

energy consumption between 18.7and 31.1kWh/m2, withan aver-

age installed power of 78.5 W/m2.

Zone D includes the coldest regions of northern Greece. Accord-

ing to this survey, almost all branches located in these regions are

equipped withoil-firedboilers in orderto meettheir heatingneeds.

Consequently, electrical energy consumption is significantly lower

than the corresponding values of branches located in the other cli-

matic zones, for which all HVAC loads are satisfied by electrically

driven equipment, either central or local split unit heat pumps.

However, heat pumps are also installed for cooling in summer

and as a backup or supplementary heating systems in winter. For

zone D, monthly energy consumption data for 4 branches were

collected and analyzed. The average monthly energy consump-tion was 20.5 kWh/m2, while the maximum and minimum values

were 35.5kWh/m2 and 20.5kWh/m2, respectively. Almost all of

the branches have an annual electrical energy consumption of

about 200kWh/m2, with the exception of one branch that reached

335kWh/m2 (Fig. 4). Based on the sample of the 4 branches, the

average CO2 emissions from electrical energy consumption were

estimated to 224 kg/m2.

The total energy consumption for heating and cooling was esti-

mated to 131 kWh/m2 of which 36 kWh/m2 is from electricity and

103kWh/m2 from heating oil (based on one branch where data

for heating energy was available). On average, the HVAC contribu-

tion to the total final energy consumption is 44.2% (of which 12%

for cooling and 88% for heating), lighting follows with 33.0% (of

which 63% for indoor space lighting, 26% for the external marquee


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103123 128

137

176197

242256

208 214

273

335

148166

157 162

236

201

0

100

200

300

400

200720062005200420032002

kWhe/m 2

Fig. 4. Evolution of annual electricalenergy consumption (kWh/m2) overa six year

period(20022007) of 4 branches in climatic zone D. Thenumerical valuesindicate

the minimum, average (square) and maximum energy consumption.

sign and 11% for security night lighting) and office and electronic

equipment with 22.8%. The estimated annual energy consump-

tion for lighting averaged 101 kWh/m2, while the installed power

for artificial lighting was estimated at 25.6 W/m2, which drops to

21.0W/m2

excluding the external marquee sign. The estimatedannual energy consumption for office and electronic equipment

was 70.4kWh/m2. The desktop personal computers and telecom-

munication equipment have an average annual electrical energy

consumption of 18.9 kWh/m2, with an average installed power of

94.2W/m2.

Basedon theavailable datafrom theinvestigated11 typicalbank

branchesand thecalculated breakdown of energy consumptionand

installedpower for thedifferent end-uses,revealedthatthe average

energy use for lighting is: 19% of the final energy consumption for

mainbuilding lighting, 11%for theexternalmarquee signand 5% for

security night lighting. Finally, the breakdown of the various office

and electronic equipment to the final energy consumption is: 9%

for personal computers and telecommunication, 4% for ATMs, 1.2%

for printers and copiers, 1.1% for standby, 1% for refrigerator and

about 0.7% all the other machines and other end-uses.

The energy intensity expressed as the ratio of the annual total

energy consumption to the number of the employees (kWh/emp)

for the different climatic zones, is illustrated in Fig. 5. Since the

number of staff in the investigated bank branches is not the same

and thus the occupancy per unit floor area is not constant, it was

necessarythat the calculations include onlythe brancheswhere the

correspondingdata was available andaccurate. Froma sample of 18

bank branches the annual total energy consumption per employee

varies between 4298kWh/emp and 9650kWh/emp, with an aver-

age value of 6993 kWh/emp.

5971

4298

7849

4874

81548371

9650

4874

6806 6782

8646

4874

0

2000

4000

6000

8000

10000

DCBA

Climatic Zone

kWh/emp

Fig. 5. Energy intensity of the annual energy consumption per employee

(kWh/emp) in the audited bank branches for the different climatic zones.

4. Energy conservation measures

An analysis of the collected data has shown that significant

energy savings can be achieved in the bank branches by the adop-

tion of various energy conservation measures (ECMs) for lighting

and HVAC. Energy consumed by office equipment and appliances

is generally associated with the use of new energy efficient elec-

tric and electronic devices. However, the energy audit revealed

that the vast majority of the bank branches are already equipped

with modern personal computers, printers and copiers. Moreover,

it is difficult to reduce the standby energy consumption for prac-

tical reasons; bank staff revealed that under heavy work pressure

it is not practical to turn on/off the equipment during the work-

inghours. In addition, some office equipmentlike automated teller

machines (ATMs), faxes and digital video recordersDVRs have to be

in standby mode all the time. Therefore, potential energy savings

office and electronic equipment were not considered.

The cost effectiveness analysis of the proposed ECMs is exam-

ined in terms of the costs and the benefits that derive from the

proposed measures when compared to the existing situation each

time. This means that any additional expenses related to extra

labour or materials required for the application of the measures

arenot taken into accountin thecosteffectiveness analysis as these

expenses may differ significantly from one branch to another. Forexample, double glass panes may not fit in all branch frames with

single glasspanes installed, meaning thatlower or higher costs may

be involved each time. Such a financialanalysis wasnot considered.

4.1. ECMs for lighting

Three differentmeasures were examined.The first scenario was

a studyof replacingthe conventional starters (old type electromag-

netic ballasts) in the luminaries with new HF electronic ballasts,

along with the replacement of any incandescent lamps (75W),

wherethey exist,withmore energyefficiency CFLlamps having the

same or better output (lm/W) [12]. The second scenario included

the reduction of the operating hours of the external marquee sign.

Finally, the third scenario included an investigation of the benefitsresultingfromthereductionofthenumberofluminaries.Thecalcu-

lations were performed by simulations using the DIALux advanced

software [13] for a typical branch.

4.1.1. Scenario A: replacement of the old conventional ignition

systems with HF electronic ballasts and the incandescent lamps

with CFL

The artificial lighting system in almost all the bank branches in

the country consists of lighting fixtures with conventional ballasts.

Almost all branches in our investigation use typical 418W T8

and 226 W TCL lighting fixtures along with a small number of

incandescent lamps. A typical and representative sample of bank

branches was examined in this scenario in order to quantify the

results.Theaverage installed power of the lightingsystem wasfound to

be about 34W/m2 which drops to 24.2W/m2 if the external mar-

quee sign is not used. The replacement of incandescent lamps and

the installation of electronic ballasts decreases the installed power

to 28.9W/m2 and 19W/m2 respectively, resulting to an average

reduction of 15% and 22%. The average energy savings and accord-

ingly the CO2 emission reductions resulting from the installation

of electronic ballasts is estimated at about 6.5% (min 4%, max 11%)

and 12% (min 4%, max 19%) of the total final energy consump-

tion which accounts for an average energy savings of 22 kWh/m2

and 29 kWh/m2 with and without the use of the external marquee

sign, respectively. Since there are some bank organizations with-

out lighting external marquee signs consuming so much energy,

the reader is advised to investigate the behavior of lighting system


6/9


in both cases (with and without the external marquee sign being

taken into account).

4.1.2. Scenario B: reducing the operating hours of the external

marquee sign

The use of a large external marquee sign contributes signifi-

cantly to the lighting energy consumption as it operates on an

average of 10h per day throughout the year. The specific sce-

nario investigated the energy savings by reducing the operating

hours to 8 h in winter (from 18:00 to 02:00) and 6.5h in summer

(from 20:30 to 03:00). This measure could be acceptable from the

bank compared to the reduction of the operating hours of night

lighting that are bound to be on throughout the night for secu-

rity reasons. An average reduction of 12% for the lighting energy

demand and about 5% for the total final energy consumption can

be achieved. The potential energy savings for the investigated

11 typical bank branches average 16kWh/m2 (average reduction

in CO2 emissions of about 14.8kg/m2) and annual revenues of

about 359 D.

4.1.3. Scenario C: reducing the number of lighting fixtures

A detailed simulation of a typical bank branch using the

advanced lighting software DIALux revealed that there is a signifi-

cant energy saving potential in lighting by reducing the number of

the installed luminaries in the working areas by an average of 40%

and 36% of the two most commonly used types of luminaries in

bank branches. However, this is the maximum reduction that can

be achieved in order to maintaina minimum illuminance of 400 lux

on the working surface (Fig. 6). In practice, a safety percentage of

+10%shouldbe considered. In ourexample,a representativesample

of a typical bank branch of 150m2 and 3.5 m height was consid-

ered. Thearrayof the installed lightingfixtureswas similar to those

encountered in most typical bank branches. The installed power

for the investigated 11 typical bank branches averages 34 W/m2

(or 24.2 W/m2 if the external marquee sign is not considered) and

after reducing the number of lighting fixtures drops to 26.6 W/m2

(or 17.6 W/m2 if the external marquee sign is not considered), but

stillmaintaining the appropriate illuminance levels. Based on theseresults, for the investigated 11 typical bank branches the average

annual energy consumption for lighting with the existing installa-

tions is 79.9 kWh/m2 (or 46.7 kWh/m2 if theexternalmarquee sign

is not considered) and by reducing the number of luminaries can

reach 63.5 kWh/m2 (or 31.7 kWh/m2 if the external marquee sign

is not considered). Thus, the average savings on the total energy

consumption can reach a maximum of 7% (or 12% if the external

marquee sign is not considered).

4.2. ECMs for HVAC

Energy consumption for HVAC dominates the total energy bal-

ance in all bank branches with the exception of A-3 where the

large length of the external marquee sign makes lighting the dom-

inant energy consuming end-use. A reduction of the cooling and

heating load and the associated energy savings is investigated in

two scenarios. The first scenario examines the adjustment of the

indoor set point temperature in accordance to the recommended

national values for public buildings. The second scenario examines

the potential reduction of the cooling and heating load by improv-

ing the branches thermal envelope by replacing the single pane

windows with insulated double glazing.

4.2.1. Scenario A: adjusting the indoor set point temperature

The energy audit of the 11 typical branches revealed a wide

range of indoor set point temperatures ranging from 22 to 27 C in

winter and 2226 C in summer. Significant energy savings could

be achieved by adjusting the indoor set point temperature to the

recommended indoor temperatures of 20 C in winter and 26 C in

summer in accordance to the national legislation for public build-

ings (Common Ministerial Decision OHJ 6/B/14826/17-6-2008).

The calculations were performed using the simple heating degree

day(HDD) andcooling degree day(CDD) methods, where data was

available. Based on the results, by adjusting the indoor set point

temperature to the recommended values the energy consumption

for HVAC can be reduced by 45% on average, which means average

savings on the total energyconsumption of about18% (56 kWh/m2)

and annual revenues of about 900 D.

4.2.2. Scenario B: installing new insulated double glazing

The energyaudit and the data collected from the archives of the

banks technical department show that a large number of the bank

branches are equipped with insulated double glazed facades. How-

ever,the potentialof energy conservation along withthe associatedcost savings and the abatement of CO2 emissions was examined

for 3 branches of the sample that were identified to have non-

insulated,single glazed facades. The thermal insulationof the walls

was not examined because of their small surface area compared to

the large transparent area. In addition, whenever there are opaque

elements in the external thermal envelope, the walls are usually

Fig. 6. Simulation results of a typical bank branch with illuminance levels using a typical number and layout of installed luminaries (left) and after reducing the number of

luminaries (right).


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y = -0.0178x + 0.5392

y = 0.0178x + 0.2853

0%

10%

20%

30%

40%

50%

60%

8.5 9 9.5 10 10.5 11 11.5 12

Equivalent operation hours of lighting (h)

Lighting Contribution to total Energy [%]HVAC Contribution to total Energy [%]

y = -0.0178x + 0.0651

y = 0.0178x - 0.0653

-10%

-8%

-6%

-4%

-2%

0%

2%

4%

6%

8%

10%

8.5 9 9.5 10 10.5 11 11.5 12

Equivalent operation

hours of lighting (h)

HVAC Deviation from the initial value (48%)Lighting Deviation f rom the initial value (35%)

Fig. 7. Sensitivity analysis of the energy consumption breakdownby changing theequivalentoperating hours of lighting (left) and deviation of HVAC and lighting percentage

contributions from the initial values (right).

covered internally by large office closets and cabinets, thus reduc-

ing large heat losses through the opaque elements. The Uvalue for

single glazing is considered at 6.0 W/m2 K while for an insulated

double glazing (5 mm, 10 mm air vacuum, 5 mm) the Uvalue was

estimated at 3.2 W/m2 K. The calculations were again performed

using the simple HDD and CDD methods. Based on the results, theaverage reduction in HVAC annual energy demand by replacing

single glazing with double glazing can reach 16% and the aver-

age savings on the total energy consumption can reach 5.7% or

18kWh/m2 with annual revenues of about 245 D.

The windows areas ranged from 46 to 63 m2 with an initial cost

of 18482536 D. The cost effectiveness evaluation was based on

theprice difference between the two materials(no insulatedsingle

glazing and insulated double glazing). The NPV calculations were

basedon thecurrentprice of electricity at about 0.11D/kWhwithan

average annual increment of about 7%,with no loans so thediscount

rate was taken equal to an average annual inflation of about 4%.

Since the external facades of the bank branches have a long life

span, the choice of installing insulated double glass panes would

be acceptable for the investigated case studies, with an internalrate of return of 4.66.4%.

5. Discussion

The calculated energy consumption indicators resulted from

processing data from actual electrical energy consumption of 40

bank branches over a period of 6 years. It is, therefore, reasonable

to assume that the available data and results are representative for

the bank branches under investigation. However, since there were

no electricity meters for the differentend uses (lighting, equipment

and HVAC), the breakdown of consumption was estimated by pro-

cessing the available data collected from the energy audits and the

survey results from the occupant questionnaires, as well as from

the interviews with the managers of each branch.

In order to investigate the possible error margins in the contri-

bution of the various end uses to the final energy consumption, a

sensitivity analysis for the breakdown of energy consumption wasimplemented. The constants in this analysis are the final energy

consumption and the installedpower of lightingand equipmentfor

whichit is believed that the possible errorsare of minor importance

as they do not significantly influence the final results. However, the

significant variables that were important in the calculation process

are the operating hours of the lighting systems and the office and

electronic equipment.

To proceed in a sensitivity analysis of the contribution of the

different end uses to the final energy consumption, the case study

considered a typical branch with an average energy consumption

taken as the average value of the sample included in this investi-

gation. The percentage contribution of lighting and equipment are

also taken as the estimated average values of the sample. Accord-

ingly, the equivalent hours of their operation were estimated foreach end-use separately taking into account the average installed

power of lighting and equipment and the average percentages

of their contribution to the total final consumption. Varying the

equivalent operating hours of lighting and office and electronic

equipment one can examine their impact on the final results and

how they alter the contribution of lighting, equipment and conse-

quently HVAC on the total energy consumption balance.

The average energy consumption of the sample was

348kWh/m2 while the corresponding average breakdown of

lighting, equipment and HVAC to the final consumption were 35%,

17%and 48%, respectively. The average installed power for lighting

y = -0.0411x + 0.6083

y = 0.0411x + 0.0411

0%

10%

20%

30%

40%

50%

60%

3.532.521.51

Equivalent operation hours of equipment (h)

HVAC Contribution change to total Energy [%]Equipment Contribution to total Energy [%]

y = -0.0411x + 0.1342

y = 0.0411x - 0.1344

-15%

-10%

-5%

0%

5%

10%

15%

3.532.521.51

Equivalent operation

hours of equipment (h)

HVAC Deviation from the initial value (48%)Equipment Deviation from the initial value (17%)

Fig.8. Sensitivity analysisof theenergy consumption breakdownby changing theequivalent operatinghours of officeequipment (left) and deviation of HVACand equipment

percentage contributions from the initial values (right).


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and equipment was 34 W/m2 and 78 W/m2, while the equivalent

operating hours for lighting and equipment were 10.1 h/day and

2.1 h/day, respectively. Fig. 7 illustrates how the contribution of

HVAC and lighting affects the total energy consumption by consid-

ering a range of possible values for the equivalent operating hours

for lighting. In this case the constant is the energy consumption

of office and electronic equipment, the independent variable is

the equivalent operating hours for lighting, and the dependable

variables are the percentage contributions of HVAC and lighting to

the total energy consumption.

Similarly, Fig. 8 illustrates how the contribution of HVAC and

office and electronic equipment to the total energy consump-

tion is affected by changing the equivalent operating hours of the

equipment. The constant in this case is the energy consumption

for lighting. The independent variable is the equivalent operating

hours of office and electronic equipment, while the dependable

variables are the percentage contributions of HVAC and equipment

to the total energy consumption.

The analysis revealed a maximum deviation of4.7% to +6.0%

forthe contributionof lightingto the final energyconsumption and

a maximum deviation of +6.0 to 4.7 for the HVAC contribution to

the final energy consumption may occur whenthe equivalent oper-

ating hours range between 8.5 h/day and 11.5h/day (initial value

10h).On the other hand, the average equivalent operating hours of

office and electronic equipment were estimated to be 2.1 h/day.

Since, the installed power of office equipment is greater than the

one for lighting, the preceding sensitivity analysis resulted to a

maximum deviation of9% to +11% for the contribution of equip-

ment to the final energyconsumption anda maximum deviationof

+9%to11%in the HVAC contribution to thefinalenergy consump-

tion, when the equivalent operating hours range between 1 h/day

and 3.5 h/day.

The energy consumptionof theexternalmarquee signis another

important parameter thatinfluences the results. Since the collected

data covers a depth of 6 years, an evaluation of the energy con-

sumption duringthis periodwas carried out. In almost allbranches

there is a significant increase of energy consumption from the year2005 to 2006. This is the period when the new external marquee

signs were installed to all branches implementing new bank poli-

cies. Itis apparentthatthe external marquee sign plays a significant

role in the energy consumption of the bank branches with an aver-

age contribution to the total energy consumption of 17%. This is

an important finding if someone would like to examine in gen-

eral the energy consumption in the banking sector especially for

these banks which have no external marquee signs installed. The

increment of the energy consumption during the examined period

also derives from the gradual increase of both the installed power

and the operation hours of equipment, lighting and HVAC units

mainly to meet the bank needs and achieve better conditions of

thermal comfort in many bank offices. Moreover, the expansion of

banks activities to new financial fields and modern products dur-ingthese years, resulted in the intensification of the working hours

and accordingly in the increased use of the energy consumption

sources as well.

6. Conclusions

Energy consumption data from 39 Hellenic bank branches for a

periodof 6 years from allthe climaticzones of the country were col-

lected andanalyzed. An energy auditalongwith anin depthanalysis

fora representative sampleof 11 typical bank brancheswas carried

out in order to investigate the energyconsumptionby the different

enduses along with thepotential of energysaving.Electricityis the

main energy source for almost all branches using heat pumps for

HVAC, except for a small number of branches located at the north-

ern part of the country (zone D) where oil fired boilers are used for

heating.

Analysis of the available data revealed that the annual aver-

age electricity consumption per air conditioned unit floor area is

337kWh/m2 (or 99kWh/m3). Excluding the branches in zone D

wherethermalenergyisalsousedtocoverheatingloads,theannual

average consumption is 348kWh/m2 (101.6 kWh/m3). The aver-

age total energy consumption (including thermal energy) is about

346kWh/m2 (102kWh/m3). Based on the results from the sam-

ple of the 11 typical branches the contribution of final end-uses to

the final energy consumption varies for lighting between 15% and

60% with an average value of 35%, for office and electronic equip-

ment between 13% and 22% with an average value of 17%, and for

HVAC between 22% and 69% with an average value of 48%. It was

revealed that the external marquee sign plays a significant role to

the total lighting load mainly because of its high installed power

and the long hours of operation. Reducing its operating hours may

resultto an average total energysaving of about 5%. Replacingboth

conventional ballasts and the incandescent lamps with HF elec-

tronic ballasts and CFL lamps could result to annual average total

energy savings of about 22 kWh/m2 (or 6.7% savings). This corre-

sponds to 11.7% if the external marquee sign is not considered in

the calculations. The evaluation of ECMs for HVAC revealed thatregulating the indoor set point temperature to meet the recom-

mendedvalues, thetotal final energyconsumption may be reduced

from 15% to 25% which means an annual average reduction in the

total energy consumption of about 56 kWh/m2. However, actual

savings will depend on the deviation of the actual settings from

the recommended values. Replacing single glazing with insulated

double glazing, the potential energy consumption savings average

5.7%. However the cost effectiveness evaluation of this measure is

strongly dependenton many factors and may be a financialburden,

especially compared against other energy conservation measures.

Acknowledgments

The research work was carried out by Mr. G. Spyropoulos, inpartial fulfilment of the requirements for an MSc in Energy at the

Department of Mechanical Engineering, Technological Educational

Institute of Pireaus, Athens, Greece and the School of Engineering

and Physical Sciences, Heriot-Watt University, Edinburgh, UK.

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