Feasibility Study of the Amoreiras Tower-3 HVAC System

Guilherme Leiteguilhermeleite@tecnico.ulisboa.pt

Instituto Superior Tecnico, Universidade de Lisboa, Portugal

June 2017

Abstract

The Amoreiras Tower-3 has an HVAC system installed that was sized to guarantee thermal comfortto all the building occupants. However, 52% of the unit owners continue to use autonomous air-conditioning systems. As some structural changes on the building areas have been made that led toincreased head losses, it is not currently possible to guarantee that the HVAC has the capacity to ensurethermal comfort to all building occupants.

The large number of equipments installed on the building’s roof is the cause of numerous problems.Therefore, the Administration proposed the replacement of the equipments with the use of the HVACsystem to the unit owners.

In this context, a feasibility study was carried out. The following items are included:

• Study of the HVAC system capacity: comparison of the HVAC power determined using the valuesof water and air flows measurements with the thermal loads obtained from the building’s energysimulation;

• Economic feasibility study, which is composed by the definition of the unit owners savings and theAdministration’s additional cost, in order to determine the value that should be charged to theunit owners.

It was proved that the HVAC system has the capacity to guarantee thermal comfort for the building’soccupants. It was also possible to conclude that the approval of the Administration’s proposal by theunit owners is advantageous for both parties, as long as the value that the Administration charges theunit owners for the HVAC system use falls within the range of [0, 1078 ; 0, 2906]e/kWh, considering apayback time of five years.

Keywords: Building energy simulation; HVAC; EnergyPlus; DOE-2.2

1. Introduction

The Amoreiras Tower 3 building has an HVAC sys-tem installed, responsible for ensuring the thermalcomfort of about 1000 workers that use the build-ing daily, however 52% of the unit owners continueto use autonomous air-conditioning systems whichcauses an underutilization of the HVAC system.

The capacity of hot and cold water productionwas sized to meet all the building areas needs.However some works on the building areas that in-creased head losses have been made, and it is notguaranteed that the HVAC has capacity to ensurethermal comfort for all the building’s occupants. Inthis context, it is necessary to conduct a study onthe HVAC’s system capacity.

The large number of units installed on the build-

ing roof cause circulation problems for the main-tenance staff and in emergency cases, loss of thebuilding’s roof structural integrity and do not allowpipeline and waterproofing maintenance to be done.For this reason the Administration suggested theunit owners to replace their equipments and startusing the HVAC system.

The Administration charges the unit owners thathave equipments on the buildings roof for the spaceusage. Therefore, the abandonment of the air-conditioning systems, although necessary, will re-duce the Administrations revenues. Furthermore,the increase in the number of users of the HVACsystem will result in an increase in the building’senergy bill. In this regard, it was suggested tothe Administration the conduction of an economicfeasability study that would allow an estimation of

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a value to be charged to the unit owners for theHVAC system usage.

In order for the Administration to be able to con-trol the owner’s energy consumptions it is funda-mental to install energy meters in the building. Inthis respect, it was proposed the preparation of abudget for the energy meters installation.

1.1. Objectives

The present work has two main objectives:The first one consists on making a study of the

HVAC system capacity. This objective is divided inother two:

• Determination of the HVAC heating and cool-ing power;

• Determination of the building thermal loads.

The second one consists on doing an economicfeasibility study of the HVAC system. This objec-tive is divided in other three:

• Determination of the space owners savings dueto the replacement of their air-conditioningsystems for the HVAC system;

• Determination of the Administration’s addi-tional cost;

• Determination of the value that should becharged by the Administration to the spaceowners.

2. State of the art

In the national legislation on the thermal behaviourof buildings, the regulation applied to the buildingin study is the RECS 1. This regulation establishesthe rules of construction, maintenance and design ofcommercial buildings. In the field of HVAC systemssizing and determination of building energy con-sumptions, this regulation establishes that is neces-sary to perform an energy simulation using a soft-ware accredited by the ANSI/ASHRAE Standard140. This standard is responsible for validating en-ergy simulation programs in order to minimize thedifferences between the results obtained in energysimulations performed in different programmes.

In order to properly size an HVAC system for aparticular building is necessary to accurately knowthe amount of energy that is necessary to remove (oradd) in order to guarantee the occupants’ thermalcomfort. This leads to the definition of heating andcooling loads.

After the analysis of the chapter Non ResidentialCooling and Heating Load Calculation Procedures ofthe ASHRAE Handbook [1] is possible to highlightfive load calculation methods:

1Regulation on the energy performance of commercialbuildings

• Heat Balance Method (HB);

• Radiant Time Series Method (RTS);

• Transfer Functions Method (TFM);

• Total Equivalent Temperature Diferen-tial/Time Averaging (TEDT/TA);

• Cooling Load Temperature differenceMethod with Solar Cooling Load Factors(CLTD/CLF).

The HB is the main method for thermal load cal-culation, being the most accurate. All the othermethods are simplifications of this one.

In the process of thermal loads calculation for asingle room is necessary to consider a very largenumber of variables and their contributions. Theamount of work involved in counting all these pa-rameters is so big, that only resorting to computerprograms is possible to have results within an ac-ceptable time period.

The energy simulation programs use the methodspresented for calculating the building thermal loads.

From the ANSI/ASHRAE Standard 140 were se-lected the following energy simulation engines:

• DOE-2.2;

• EnergyPlus;

and the following graphical user interface (GUI):

• eQuest;

• Autodesk Revit/Green Building studio;

• DesignBuilder;

• OpenStudio:

• Archsim.

The GUI provide easier building modelling anddata entry for the energy simulation engines. Thefirst two GUI introduced use DOE-2.2 to performenergy simulations, which uses the RTS method.The other three GUI use EnergyPlus, which usesthe HB method.

3. Building Energy Simulation Software Se-lection

It was decided to perform an energy simulation ofthe building using the two energy simulation en-gines presented. This way is possible to compareand discuss the results obtained, allowing a bettervalidation and interpretation of the results.

Due to the high complexity of the case studybuilding it was decided to use a GUI for each energysimulation engine.

In order to choose a GUI for each engine, eachone of these was tested and several scientific articlesrelated were analysed.

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3.1. DOE-2.2 GUI selection

In order to choose a GUI for DOE-2.2 a compar-ison was made between eQuest and Autodesk Re-vit/Green Building studio.

Both GUI have good accuracy but the eQuest re-quires a more detailed data entry and technicallyoriented [3]. Although eQuest allows simple build-ing modelling, the innovative Building InformationModelling Technology (BIM) makes this processeven easier. Besides that, Revit/GBS allies to thiscapability the ability to export the model createdto other programs like EnergyPlus and eQuest [?].On the contrary eQuest does not have this capabil-ity. For these reasons it was decided to choose theRevit/GBS GUI.

3.2. EnergyPlus GUI selection

In order to choose a GUI for EnergyPlus a compar-ison was between DesignBuilder, OpenStudio andArchsim.

The EnergyPlus GUI selection was not possible toachieve through a simple analysis since this did notallow to properly differentiate the programs. There-fore, an evaluation of each GUI presented was made,oriented to the work objectives.

With the objective of organising the informa-tion of the scientific articles ([4],[8],[2],[7]) and the-ses ([6]) on the basis of which the comparison wasmade, seven different criteria were defined:

• Modelling;• Usability;• Functioning;• Intelligence;• Interoperability;• Accuracy;• Accessibility.

The criteria Modelling is related to buildingmodelling and thermal zone defining.

The criteria Usability refers to the user-friendliness and support material availability.

The criteria Functioning refers to the phases af-ter the building modelling and includes the programorganization, data-entry, availability of templatesand parameter setting.

The criteria Intelligence is related to the pro-gram output capabilities, library dimension, anduser guidance throughout the energy simulation.

The criteria Interoperability refers to the im-port and export capabilities.

The criteria Accuracy refers to the proximityof the results obtained in the program and the re-sults obtained in the experimental tests created forthe energy simulation programs validation, done ac-cording to the Standard ANSI/ASHRAE 140.

The criteria Accessibility refers to the availabil-ity of institutional, educational and temporary li-censes.

3.3. Results

The results of the comparison between the threeGUI selected are present in the radar charts of Fig-ure 1.

(a) DesignBuilder (b) OpenStudio (c) Archsim

Figure 1: Results of the comparison between theEnergyPlus’ GUI

It was chosen the GUI that presented a betterbalance between the seven criteria. Accordingly, itwas decided to use the DesignBuilder to performthe energy simulation of the Amoreiras Tower-3.

4. Case Study

The Amoreiras Tower-3 is an office building built in1986, with an area of 19950m2, classified as a bigservice building. It has an average ceiling height of3, 23m and is occupied daily by around 1000 people.

The building is located in the city of Lisbon andthe building facades are oriented to North, South,East and West and there are no buildings in thesurrounding area that cause shadowing. The build-ing facade facing the Avenida Duarte Pacheco isapproximately oriented to West and the facade fac-ing the Tierno Galvan street is approximately ori-ented to South. The building has 18 floors abovethe ground and four floors below the ground.

The configuration of the building is the following:

• 2nd to 17th floor, space intended for offices;• 0 to 1st floor, lobby and shopping area fo the

Amoreiras’ Mall;• -4 to -1 floor, parking space;• Common Spaces;• Roof.

The floors above the ground have an area of ap-proximately 1285m2 with the exception of the 13thand 17th floors that are located below and abovethe transition of the two ”bodies” of the building,and have an area of 936m2. The 17th floor has anarea of 1024m2 area due to the existence of privateuse balconies.

Only the floors between the 2nd and 17th floorsare heated and cooled. According to the roofoccupation list the group of units that use au-tonomous air-conditioning systems has a total area

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of 10427m2, representing 52% of the total buildingarea.

The HVAC system installed in the building ter-race has a Chiller that produces cold water with acooling power of 1082kW and a Heat Pump thatproduces both hot and cold water with a coolingand heating power of 650kW and 642, 3kW , respec-tively. It also has four Air Handling Units (AHU)that have cooling and heating coils that receive15, 3l/s and 16l/s of cold and hot water, respec-tively, provided by the Chiller and the Heat Pump.

In Table 1 are shown the values of the waterflows obtained from the building’s water networkdiagram. The cold water flow is composed by thesum of the water flow from the Chiller and the HeatPump when it is on cooling mode.

Table 1: Hot and cold water flows nominal values

Floor Hot water [l/s] Cold water [l/s]17 0,844 2,87

15 to 16 0,74 4,08214 0,892 4,12813 0,62 2,80212 0,892 4,128

9 to 11 0,74 4,0822 to 8 0,728 4,147

From the analysis of the building’s electricity billsof the year 2016, the annual consumptions of thebuilding organized in four different groups were ob-tained (Table 2) and also the annual energy con-sumption of the Heat Pump and Chiller (Figure 2).

Table 2: Amoreiras Tower-3 Energy Consumptionsdistribution

Annual Energy Consumption

[kWh/year]

Heat Pump 375116

Chiller 147421

Fire detection

system12448

Others 178493

5. Implementation

In order to determine if the HVAC system has thecapability to ensure the building occupants thermalcomfort in the case of every space of the buildingbeing climatized by the HVAC system, was decidedto conduct a study on the HVAC system capacity.

Since on a first analysis the replacement of theautonomous air-conditioning systems for the use ofthe HVAC system seemed to generate economic sav-ings for the owners and an additional cost for the

Figure 2: Chiller and Heat Pump energy consump-tions in 2016

Administration it was decided to do an economicfeasibility study in order to determine an appropri-ate value to be charged by the Administration tothe owners for the use of the HVAC system.

5.1. Case-study units selection

In order to conduct the intended studies, it was im-perative to have access to the building units’ plansand electricity bills. Since it was not easy to find aunit that fitted these needs it was considered rea-sonable to select two different building units to useas a case-study. These units needed to have thesame solar orientation, room area, and constructionmaterials, but one had to use the HVAC system andthe other an autonomous air-conditioning system.

According to the requirements established wereselected the two following building units:

• Unit A, uses an autonomous HVAC system;

• Unit B, uses the building HVAC system;

Unit A is localized on the 9th floor and Unit Bis on the 10th. Both units occupy approximatelyhalf of each floor, with an area of 540m2 and areoriented mainly to the Southeast.

5.2. HVAC System Capability Study

The methodology used on the HVAC system capa-bility study is presented on the diagram of Figure3.

Figure 3: Methodology of the HVAC System Capa-bility Study

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To verify that the system is capable of guaran-teeing the building occupants’ thermal comfort, theHVAC system heating and cooling power suppliedto the building and to the case-study rooms wascompared to the thermal loads determined in theenergy simulations.

The heating and cooling power of the HVAC sys-tem is determined in function of the hot and coldwater flows and the air flows from the AHU. Sincethe renewal of the HVAC system in 2013 there werenot made measurements that proved that the val-ues of the building water network could still be used.In this regard the water and air flows supplied tothe case-study units were measured using the equip-ment provided by the Energy Laboratory of Insti-tuto Superior Tecnico.

5.3. Economic Feasibility Study

The methodology used on the Economic FeasibilityStudy is presented on the diagram of Figure 4.

Figure 4: Methodology of the Economic FeasibilityStudy

By abandoning their autonomous air-conditioning systems and start using the building’sHVAC system, the owners will immediately savethe energy consumption regarding the air con-ditioning of their rooms. In addition, to all theowners that have air conditioning systems installedin the building’s roof is charged a monthly rent forthe space usage.

To determine the energy savings for the own-ers that replace the autonomous systems with theHVAC system of the building, the case-study units’electricity bills were analysed and compared. Theseelectricity bills were provided by the units’ ownersand corresponded to the period between the 23rdof March and the 6th of December of 2016.

5.4. Energy Simulation

The energy simulation was performed in the twoprograms selected in Chapter 3. The methodol-ogy and objectives of the energy simulation are pre-sented in Figure 5.

On Revit/GBS the energy simulation was startedby modelling the building and then entering the

Figure 5: Methodology of the Economic FeasibilityStudy

data corresponding to the energy simulation mainparameters:

• Construction type;• Localization;• Infiltration class;• Thermal zone configurations;• Room configurations;

For the city of Lisbon both programs use theweather data from the Avenida Almirante GagoCoutinho weather station, which contributes to theproximity between the results. In this programthere are no templates available, compelling theuser to manually enter all the data. In the Re-vit/GBS’s library are included occupation, light-ning and equipment schedules, but when comparedwith the information provided by the Administra-tion, it was concluded that these were not themost appropriate for the case-study. In this regardspecific schedules for the case-study building weremade (Figure 6).

(a) Occupation (b) Lightning (c) Equipment

Figure 6: Amoreiras Tower-3 schedules on Re-vit/GBS

Thereafter the HVAC system of the building wasdefined. Among the few options available, a fourtube fan coil system was selected, powered by aheating and cooling unit, which is very similar tothe real case. However, this mode of definition doesnot allow to detail the HVAC system, making thecalculations possibly less accurate for other HVACsystem cases.

In DesignBuilder there are several templatesavailable for different building types, saving the usertime on the data entry process. There were alsoincluded in the program’s library occupation, light-ning and equipment schedules specific for the pre-vious regulation regarding buildings thermal per-formance, the RSECE. These schedules were very

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similar to the schedules created specifically for thebuilding in study for the Revit/GBS program. Forthis reason they were used in the energy simulation.

In the description of the HVAC system in De-signBuilder, there are three different levels of detailavailable.

The Simple modeling mode only requires for theuser to select the type of HVAC system and the pro-gram provides all the corresponding data automat-ically. However, it was not found a template thatproperly characterized the building’s HVAC system.Since the Autodesk Revit/GBS program does notallow to characterize the HVAC system with detail,it was decided to use the capabilities of this pro-gram to obtain a system as close to the existing oneas possible. For this reason it was used the mostdetailed HVAC modelling mode. In each thermalzone (Figure 7) was introduced: a variable air vol-ume control system that regulates the air flow en-tering the room, provided by the UTAN; a four tubefan coil that receives hot and cold water from theHeat Pump and Chiller, respectively; an air extrac-tor connected to the UTAN. This system (Figure 8)is very similar to the real one.

Figure 7: Average air velocity in the AHU

Figure 8: Building’s HVAC system on Design-Builder

6. Results and Discussion

6.1. HVAC system power

Units A and B occupy approximately half the areaof the 9th and 10th floor, respectively, receiving

0, 37l/s of hot water and 1, 929l/s of cold water,according to the building’s water network diagram.

The values obtained in the measurements of thewater flows were compared with the nominal valueson Table 3.

Table 3: Comparison between the water flow mea-surements and the nominal values

Unit A Unit B Nominal value

Hot water [l/s] 0,189 0,188 0,37

Cold water [l/s] 0,773 0,762 1,929

From the analysis of Table 3, it can be concludedthat the values obtained are considerably lower thanthe nominal values. This was expected since theyare the maximum values for which the system wasdesigned. In addition, the measurements were car-ried out in March, when the heating needed is muchlower than in other months. The small value of coldwater flow is justified by the occasional need of cool-ing.

The results of air flow measurements were com-pared with the nominal values in Table 4.

Table 4: AHU’s air flow

Velocity

[m/s]

Measured flow

[m3/h]

Nominal flow

[m3/h]

AHU 1 3,32 17928 18000

AHU 2 3,29 17766 18000

AHU 3 3,33 17982 18000

AHU 4 3,31 17874 18000

With the results obtained previously it was de-termined the total power supplied by the HVACsystem to each case-study rooms (Table 5).

Table 5: Total cooling and heating power suppliedto the case-study rooms

PowerCase-study units

[kW ]

HVAC

[kW ]

Heating - water 9, 31

Heating - AHU 8, 4

Heating - Total 17, 71 642, 3

Cooling - water 48, 33

Cooling - AHU 6, 92

Cooling - Total 55, 25 1732

The heating and cooling power values providedby the AHU to the case-study rooms have the sameorder of magnitude as the power supplied by thewater network, thus being validated.

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6.2. Energy Simulation

The energy simulation on the Revit/GBS deter-mined that the building uses 785706kWh of elec-tricity in air conditioning (Figure 9). On a firstanalysis this value seems reasonable, because it isin the same order of magnitude as the current realconsumption of the HVAC system. The value ob-tained is larger than the real one, which is expectedsince the HVAC is only used currently by less thanhalf the unit owners.

Figure 9: Annual Energy Consumption

In Figure 10 is shown the annual evolution of thebuilding’s thermal loads.

(a) Heating (b) Cooling

Figure 10: Annual distribution of the building ther-mal loads

The values for the thermal loads obtained inthe energy simulation performed by Revit/GBS areshown in Tables 6 and 7.

In Figure 11 is shown the building’s annual CO2

emissions. There is no fuel consumption in the case-study building, therefore the value of the building’sannual CO2 emissions is 543 tons.

In DesignBuilder the building’s annual energyconsumption is around 765000kWh (Figure 12),which is very close to the value obtained in Re-vit/GBS.

The values for the thermal loads obtained in theenergy simulation performed by DesignBuilder areshown in Tables 6 and 7.

In Figure 13 is shown the annual evolution ofthe building’s CO2 emissions determined by Design-Builder. According to this program the buildingproduces 567 tons of CO2 per year.

Figure 11: Building’s annual CO2 emissions (Re-vit/GBS)

Figure 12: Annual evolution of energy consump-tions

Figure 13: Annual evolution of the building’s CO2

emissions (DesignBuilder)

According to a study on the CO2 emissions ofair conditioning systems [5], an equipment responsi-ble for air conditioning an area with 36, 85m2 emits1, 368 tons of CO2. Extrapolating this value to thebuilding under study, the annual emission of CO2

by air conditioning systems would be around 740tons. Thereby, it can be stated that the use of a cen-tralized HVAC system in Amoreiras Tower 3 wouldallow a saving of 185, 6 tons of CO2 in comparisonwith the use of several autonomous air conditioningsystems.

Comparing the values of the HVAC’s heating andcooling power with the values of the thermal loadsobtained in the energy simulations (Tables 6 and 7)it was concluded that the HVAC system has capac-ity to ensure thermal comfort to all building occu-pants.

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Table 6: Comparison of the HVAC’s heating powersupplied to the case-study unit and building withthe heating loads

HVAC’s heating

power [kW]

Heating loads

[kW]

Revit/GBS DesignB.

Case-study

room17,71 10,77 14,35

Building 642,3 605,82 481,96

Table 7: Comparison of the HVAC’s cooling powersupplied to the case-study unit and building withthe cooling loads

HVAC’s cooling

power [kW]

Cooling loads

[kW]

Revit/GBS DesignB.

Case-study

room55,25 54,12 52,03

Building 1732 1478 1547,85

6.3. Unit owners savings

The determination of the energy savings is calcu-lated by three different methods: direct analysisof the consumption of electric energy, degree-daysmethod and energy simulation.

Through the analysis of the case-study units’electricity bills was drawn the graphic of Figure 14that allows to identify the difference of consump-tions between a room that uses an autonomousair-conditioning system and another that uses theHVAC system.

Figure 14: Case-study units energy consumptions

From the graphic of Figure 14 it was determinedthat Unit A presents a mean consumption in theheating and cooling periods of 1502, 3kWh/monthand 1773, 5kWh/month, respectively. Unit Bpresents an average consumption in the heatingand cooling periods of 1143, 2kWh/month and1333, 9kWh/month, respectively. It was verifiedthat Unit A consumes 359kWh/month more thanUnit B in the heating period and 439, 6kWh/monthmore in the cooling period. As the energy consump-tion of Unit B is independent of the HVAC system’susage, it was considered that the average value ofthese consumptions corresponds to the units’ con-sumptions not intended for air conditioning.

In Figures 15 and 16 is shown the relation be-tween degree-days and the case-study units elec-tric energy consumptions. As expected, the UnitA’s energy consumptions increase with the degreedays. Unit B’s consumptions are not affected bythe degree days variation, since this unit does notuse electric energy to condition the air.

(a) Unit B (b) Unit A

Figure 15: Relation between the case-study unitsconsumptions and degree days on the heating pe-riod

(a) Unit B (b) Unit A

Figure 16: Relation between the case-study unitsconsumptions and degree days on the cooling period

Revit / GBS presents only the energy consump-tions of the building, not specifying the unit’s con-sumptions. For this reason, in the determination ofthe unit owners’ savings this program was not used.DesignBuilder presents, in addition to the consump-tion of the building, the consumption of every build-ing’s unit. Using the data obtained in the energysimulation it was determined the annual electricalconsumption of the case-study unit for air condi-tioning, which corresponds to the energy savingsthat the unit owners will have in case of abandon-ing the autonomous system and use the building’sHVAC system.

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The results of all three methods are organised inTable 8.

Table 8: Energy saving for unit owners determina-tion methods

Air-conditioning

[kWh/month]

Others

[kWh/month]

Direct analysis 399,3 1238,55

Degree-days 322,65 1387,22

Energy simulation 421,83 -

From the analysis of Table 8 it was possible toverify that the values obtained in the different meth-ods are in the same order of magnitude and veryclose. Since the value of the direct analysis corre-sponds approximately to the average value of thethree methods, it was decided to use this value inthe following calculations.

In order to obtain the value of the economicsavings resulting from the substitution of the air-conditioning systems by the building’s HVAC sys-tem, the average energy price was calculated. Inthis sense, for each case-study unit were calculatedthe costs of the energy consumption and dividedby the values of the energy consumptions previ-ously determined. Thereby, was obtained the av-erage price paid per kWh consumed was obtained:0, 1247 e/kWh.

The amount saved on the roof space rent is shownin Table 9.

Table 9: Roof space renting

case-study

room

Area

[m2]nr. of devices

rent

[e/month]

room A 9,4 3 457,12

The results obtained previously are organized inTable 10. It is concluded that the unit owners havea total saving of 507, 12e/month.

Table 10: Determination of the unit owners eco-nomic savings

Energy savings Terrace rent Total

[kWh/month] [e/month] [e/month] [e/month]

400 50 457,12 507,12

6.4. Additional cost to the Administration

The additional cost to the Administration is ob-tained from the sum of the following parts:

• Decrease in revenues generated by the roofspace rental;

• Installation of energy meters;• Increase in energy consumption.

In order to determine the cost of the energy me-ters installation in the building, was prepared abudget based on information provided by the com-pany responsible for the renewal of the HVAC sys-tem in 2013. Was obtained the value of 28743, 65e.

The average value of the building’s annual energyconsumption obtained in the two energy simulationsis 776000kWh/year. As the current building’s en-ergy consumption is 522537kWh/year, the increasein energy consumption will be of 243770kWh/year.

Using the value of the average price paid per kWhconsumed (0, 1247e/kWh) obtained previously, theadditional cost to the Administration resulting fromthe increase in energy consumption was determined:30398e/year.

It was thus determined that in the event thatthe unit owners join the Administration’s proposal,it is necessary for the Administration to spend28743, 65e at the beginning of the process to in-stall the energy meters, and will have an additionalannual cost of 76919, 4e.

6.5. Economic feasibility study

Assuming a five year return period in the initial in-vestment for the installation of energy meters, therewill be an annual value of 5749e that the Adminis-tration has to receive in order to settle the invest-ment. Adding up to this value the annual energyconsumption and decrease of profits will lead to anannual value of 82667e. This value is the break-even point, that corresponds to 4,14e/m2.

This way it is possible to conclude that the Ad-ministration can select a value between the rangeof values: [0,1078 ; 0,2906]e/kWh to charge theowners for the HVAC system use.

7. Conclusions

In the HVAC’s capability study was concluded thatsince the power of heating and cooling provided bythe HVAC system exceeds the thermal loads deter-mined in the energy simulations, this system hasthe capability to ensure the thermal comfort of allthe building’s occupants.

Moreover, the proximity between the values ofthe thermal loads and the HVAC system power,lead to the conclusion that this system is well de-signed for this building.

In the economic feasibility study was determinedthe range of values between which the Administra-tion can select the value to charge the owners forthe use of the HVAC system in order to make the re-placement of the autonomous air-conditioning sys-

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tems for the use of HVAC system beneficial to bothparties

In the energy simulations were obtained consis-tent results with the actual values of the HVAC’spower and energy consumption, as well as the en-ergy consumption of the building and the case-study rooms.

It was concluded that the exclusive use of a cen-tralized HVAC system in the Amoreiras Tower 3would produce a significantly lower amount of CO2

than the use of several autonomous air-conditioningsystems, thus generating an environmental im-provement.

7.1. Future Work

It is concluded that in the future the Administra-tion should install energy meters in the building andselect a value to be charged to the owners within therange of values given. The autonomous air condi-tioning systems should be replaced by the build-ing’s HVAC system which was confirmed to havecapacity to ensure thermal comfort to all building’soccupants.

Since the scenario initially found in the Amor-eiras Tower-3 is common to many other build-ings, both commercial and residential, the feasibil-ity study presented can be applied to many othercases, contributing to a reduction of energy con-sumption and environmental improvement

Aknowledgements

I would like to express my sincere gratitude to mySupervisor Prof. Carlos Silva, who immediately ac-cepted the guidance of this work and never doubtedof its success. A special thanks to the Amor-eiras Tower-3 Administration for providing the doc-uments and data essential for the work execution.

Moreover, I would like to acknowledge Dr. LuisGomes and Eng. Alejandro Martins for providingthe electricity bills necessary for this work imple-mentation. I would also want to thank Eng. RuiPereira and Eng. Joao Patricio from the Sustain-able Campus project, for the support given on themeasurements, and Eng. Joana Pedro for her sup-port and availability. Last but not least a specialthanks to my family for being the ones who mostsupported me and kept me motivated during thistime and to all my friends, especially to my col-leagues Francisco Fernandes and Antonio Henriquesfor always helping me when necessary.

References

[1] ASHRAE. Chapter 29: Nonresidential Coolingand Heating Load Calculation Procedures. InASHRAE Handbook Fundamentals, pages 29.1–29.39. 2001.

[2] S. Attia, L. Beltran, A. D. Herde, and J. Hensen.Architect Friendly: A Comparison of ten dif-ferent building performance simulation tools.pages 204–211, 2009.

[3] D. B. Crawley, J. W. Hand, M. Kummert,and B. T. Griffith. Contrasting the capabili-ties of building energy performance simulationprograms. (July), 2005.

[4] D. Documentation. DesignBuilder EnergyPlusSimulation Documentation. 2016.

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