space heating systems

Energy and Buildings 72 (2014) 398410

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Energy and Buildings

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A framework to monitor the integrated multi-sousystems to improve the design of the control syst

Xinming aidia Department o , Alberb Department o nada

a r t i c l

Article history:Received 8 JulReceived in reAccepted 23 D

Keywords:Renewable enGround sourceEnergy savingCOP improvemEnhanced con

high courcerch stem eat r

ce hem thntegrHR sa rescien

ndings, adjustments in the design of the heating system controls are proposed to enhance systemefciency.

2014 Elsevier B.V. All rights reserved.

1. Introdu

1.1. Ground

Geothericantly lowApproximathe sun [2]in diverse wreadily, theremains conclassied bwell as fortemperaturmoderate tperatures ([5,6]. The ruses low te

AbbreviatiDWHR, drain wassisted grounhigh-density p

CorresponE-mail add

0378-7788/$ http://dx.doi.oction

source heat pump system

mal heat is an efcient source of energy with signif-er CO2 emissions than conventional fossil fuels [1].tely 47% of ground thermal energy is absorbed from. This thermal energy stored in the ground manifestsays. While the earth surfaces temperature uctuates

ground temperature at shallow depth (below 9 m)stant for years [1,3,4]. Furthermore, geothermal energy

y source temperature is used for power production as cooling and heating systems. Geothermal sources ofe above 150 C are used for power production, whileemperatures (between 90 C and 150 C) and low tem-below 90 C) are suitable for space heating or coolingesidential facility used as a case study in this researchmperature sources for space heating [7] in the form

ons: GSHP, ground source heat pump; GHE, ground heat exchanger;ater heat recovery; SHTS, solar heat transfer station; SAGSHP, solar-

d source heat pump system; COP, coefcient of performance; HDPE,oly-ethylene.ding author. Tel.: +1 780 492 3002.ress: [email protected] (M. Gul).

of a geothermal heating system using a ground source heat pump(GSHP) system.

A ground source heat pump comprises three main elements:a ground heat exchanger (GHE), a heat pump, and a distributionsystem [8,9]. The GHE, which is the main component, uses shallowground as its energy source and a water/glycol mixture as the trans-port medium. The underground temperature, it should be noted, iswarmer than the outside air temperature in winter, but cooler thanthe outside air temperature in the summer. The mixed uid owsthrough buried piping, storing heat, and releasing it into the soilunder the building site. A low-power circulating pump circulatesthe uid. In winter, a GSHP system can extract heat from shallowground to provide energy for space heating. In summer, the sys-tem is reversed to transfer heat out of the building using the coolerground as a heat sink [10,11].

GHEs can be further congured as either open-loop or closed-loop [11]. Open-loop exchangers use surface or underground watersources as a direct heat source. Normally, this operation can becompleted at a lower cost and with less loss during heat transferthan closed-loop. However, spatial constraints limit usage of theopen loop, and the water present in the system usually causescorrosion over time [12]. The closed loop, on the other hand, circu-lates water through pipes that can be installed either vertically orhorizontally. The vertical closed loop is widely used since it is notlimited by surface area. However, in this system, initial excavationcosts are generally high [13]. In the research described in this

see front matter 2014 Elsevier B.V. All rights reserved.rg/10.1016/j.enbuild.2013.12.049 Lia, Mustafa Gula,, Tanzia Sharmina, Ioanis Nikolf Civil and Environmental Engineering, University of Alberta, 9105 116th St, Edmontonf Computing Science, 2-21 Athabasca Hall, University of Alberta, Edmonton, Alberta, Ca

e i n f o

y 2013vised form 21 October 2013ecember 2013

ergy heat pump

enttrol system

a b s t r a c t

Building space heating contributes to sources. Usage of renewable energy sThis paper presents an empirical reseaformance of an integrated heating syseld, solar energy, and drain water hto address are: (1) the ground sourheating system causing heat loss frocold-climate regions. The proposed iwhich is supported by solar and DWThe framework is validated through tem is installed to evaluate the coef/ locate /enbui ld

rce space heatingem

sb, Mohamed Al-Husseina

ta, Canada

onsumption of energy using primarily non-renewable energys is constrained by high initial costs and long-term payback.tudy to evaluate the design of the control system and the per-utilizing renewable energy sources by means of a geothermalecovery (DWHR) system. Two main challenges we attemptat pump (GSHP) system is designed to function only as ae geothermal eld and (2) high heating load is required inated space heating system uses mainly geothermal energy,ystems to recover the heat loss from the geothermal eld.idential building under occupancy where, a monitoring sys-t of performance of the space heating system. Based on the

X. Li et al. / Energy and Buildings 72 (2014) 398410 399

Nomenclature

Q C M T V RmRvTReturnTSupplyt Ra Avg(E) W%

paper, closeto the given

GSHP hasystem. Therefrigeratioraises the teto drive theinvolved is aless primaryful CO2 emisa coefcienformance osource heatsuch as air-

As oppoand coolingin cold-climload is mucidentied twpumps in coing load, antemperaturbe guaranteation couldthe undergrCOP of the use of a largConsequentwill supply

Bakirci atical GSHPsThey foundexchanger (bined with of the heatet al. have cating that effectively ing demandoperate witformance oconditions, eld affect ttems. The 1982 [23]. Iidea of stor

In cold regions, the performance of the GSHP can be improved byutilizing solar energy, which is referred as a solar-assisted groundsource heat pump system (SAGSHP). For such systems, solar energy

can be installed on the source side of heat pump to increaseet temn be

the s. Wition peruild

l heahan

COP, a reula

tinuoComr spaargine re

cold-er co

wit its ust sa

thatater

d on is the

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coldt tem

ter, o sou is at of s

can spar

reco wat

extrse ut col, thieducneds, nThermal Energy, kilojoules (kJ)Specic Heat (kJ/kgC)Mass of uid within a period of time (kg)Temperature difference (C)Density of uid (kg/m3)Volume of uid (m3)Mass ow rate of uid (kg/hr)Volume ow rate of uid (m3/hr)Temperature of return pipe (C)Temperature of supply pipe (C)Serving time or operation time (hrs)sun radiation historical information (kWh/m2/day)Average efciency factorEnergy wasted percentage

d-loop GHEs are utilized in an occupied building due space limitations.s two other components: a heat pump and a distribution

heat pump is operated based on a vapor-compressionn cycle [14]. During this cycle, the pump effectivelymperature of the ground source using electrical power

compressor [15]. The lifespan of the mechanical partspproximately 50 years [16]. Since heat pumps consume

energy than conventional heating system, fewer harm-sions are produced in the process [17,18]. In this regard,t of performance (COP) is used to evaluate the per-f heat pumps. According to previous research, ground

pumps have a higher COP than regular heat pumps,source heat pumps [19,20].sed to specic hot-climate regions where the heating

systems require almost equivalent loads all year round,ate regions larger GHEs are required since the heatingh greater than the cooling load [21]. Roth, similarly, haso major challenges related to use of conventional heat

ld regions: that the heating load is greater than the cool-d that heating capacity and COP decrease as the outsidee drops [22]. Since the cooling load in summer cannoted to offset the heating load in winter, long-term oper-

result in an irreversible decrease in the temperature ofound eld and end up with a heat loss. In this case, theheat pump could also be markedly reduced. However,er GHE is constrained by initial cost and space size [23].ly, the use of an efciently designed integrated systemenergy in a manner which ensures energy savings.nd Colak have investigated the performance of ver-

systemthe inltion caloss ofregionutilizasoil temto the bdentiawas ensystemregionSYS simof conChina. tem foby a mthe samin the weathperformagainsand cocludedis a greexertepaper

1.2. Ob

In aambienin winenergyenergyponen[26]. Itmer asenergya drainDWHRand reupreheastudiesand a ris desigural ga during Turkeys coldest seasons (Jan.Feb., 2010). that the use of a superheating and sub-cooling heatSHCHE) can improve COP by 0.10.2. Solar energy com-a GSHP system, which serves to increase the efciency

pump, is also widely used in cold regions [18]. Zhaisummarized the integrated approaches of GSHP, indi-integrating a GSHP system with a solar thermal systemprovides thermal energy to buildings for which heat-s signicantly exceed cooling demands, and is able toh a high COP of 3.5, which is much better than the per-f a traditional GSHP system [21]. However, the climatebuilding functions, and thermal balance of the groundhe design of such renewable energy-based heating sys-rst solar-assisted GSHP was recommended by Metz int was Penrod, in an earlier study, who established theing solar energy in the ground [23,24].

Fort McMurground. Thpreset temp

As discuGSHP systefor both heause of GSHrequired, wpaper, an inin a residenheating is aintegrated assist the Ghighly efc

Since cocially whenperature of heat pumps. Meanwhile its energy produc-directly sent to the ground eld to compensate the heateld and recover the eld back to the balance in coldth the assistance of solar energy, this comprehensivenot only offsets the deciency of GSHPs by facilitatingature eld recovery, but also provides intermittent heating [10,25]. Bakirci et al., in a study of cold-climate resi-ting in Erzurum, Turkey, found that the COP of a SAGSHPced to the range of 3.03.4, while the overall heating

was 2.73.0 [26]. Investigating a similar cold-climatesearch group from Hong Kong, China, has utilized TRN-tion software to forecast the performance for 20 yearsus operation under the climatic conditions of Beijing,pared to a conventional GSHP system, a SAGSHP sys-ce heating and domestic hot water improves efciency

of 26.3% [27]. However, results from another study bysearch group simulating the performance of a SAGSHPclimate region of Harbin, China, which has comparablenditions to Fort McMurray, Canada, showed SAGSHP toth a lower efciency of 2.84. As such, they recommendedtilization in extreme weather in the interest of energy

ving [28]. Using the same software, Niu et al. have con- system efciency decreases more rapidly when there

difference between the heating load and cooling loadthe GSHP [29]. The case that is being addressed in this

special condition when only heating load is required.

ve and scope

-climate region such as Fort McMurray, with very lowperature and relatively low underground temperaturenly an optimal integration of a number of renewable

rces can lead to efcient energy production [30]. Solar clean and renewable resource, and an essential com-ustainable energy for space heating and water heating

either as direct heating energy or be stored in sum-e energy and drawn upon by the geothermal eld forvery. Another energy source used in this case study iser heat recovery (DWHR) system, due to the fact thatacts heat from wastewater, and in this way can collectp to half of the energy in the wastewater and utilize it tod water travelling to the water heater. Based on previouss translates to heating cost savings of up to 40% [2,31],tion in greenhouse gas emissions. In this project DWHR

to also increase the efciency of the GSHP system. Nat-ally, is widely used as an energy source, particularly inray, which has considerable natural gas reserves under-is source is used to fuel boilers, which heat uid to aerature to be circulated throughout the building.

ssed above, most of the existing research with respect toms has investigated cases where these systems are usedting and cooling. This paper, however, investigates theP in a cold-climate region where only heating load ishich introduces additional challenges. Therefore, in thistegrated heating system is proposed and implementedtial building under occupancy in Fort McMurray, where

major contributor to total energy consumption. For thissystem, solar, and drain water heat recovery (DWHR)SHP system in combination with natural gas, which is aient resource.ld weather challenges the use of the GSHP system, espe-

it is not designed as a cooling system to recover heat

400 X. Li et al. / Energy and Buildings 72 (2014) 398410

ng-te

from buildiexplore thebased monpresented bsis on dataMay), wherBased on ththe efcienthus to impoperating ccold-climatif an enhansystem assimeans to pis also expeby reducingeral framewnoted that nthe scope o

2. Propose

2.1. Case st

This paping source-buildings inPlaza [32]McMurray, project hasing, high efbased on a struction cohas been ccuit loops diameter ofing. 1.91 cminstalled insAt this junc

ojectling st a lag in me t

the -burnt.

opos

therergyy if t

to Gl eneFig. 1. Project building management layout and lo

ngs in summer, the rst objective of this research is to integrated heating system performance using sensor-itoring (data collection and data analysis). Analysis isased on the early data collected with particular empha-

over the transition from winter to summer (March e the impact of seasonality can be readily appreciated.e analysis results, suggestions are made to improve

cy of the system. The second objective of this study isrove the COPs of each heating system, minimizing theost, and satisfying the large heating demands typical ofe regions by developing a better control system. Thus,ced control system is developed and utilized, a GSHPsted by solar and DWHR can be considered an effectiverovide energy in cold-climate regions. This frameworkcted to reduce the potential environmental footprint

greenhouse gas emissions. Fig. 1 illustrates the gen-

this pras coo(2) thaheatinovercobolsterral gasprojec

2.2. Pr

GeoThis enfriendlrelatedannuaork of the project and research direction; (it should beot all of the components presented in Fig. 1 fall within

f this paper).

d methodology implementation

udy introduction

er describes in detail the monitoring of integrated heat-assisted GSHP systems for space heating in residential

a cold-climate region. The project, Stony Mountain, comprises two residential buildings located in FortAlberta, Canada (564335N 1112249W). The entire

been designed based on the principles of energy sav-ciency, and low operational cost, and has been builtmodular construction approach in order to reduce con-st and cycle time. One of the two residential buildingshosen for this research. Ten geothermal vertical cir-with 8 boreholes at a depth of 91.44 m (300 ft) and

12.7 cm (5 in) per circuit are installed under the build- (3/4-in) high-density poly-ethylene (HDPE) pipes areide the borehole to transport 13.6% methanol with heat.ture it is important to note two challenges regarding

tem in winthe energy an exampleexpected ovearth whendecreases. is transferrthe availabrange remaoccasional sUnlike typicnot designenecessary tperature ofon the geothe expecteuctuates uFig. 3(a), if the energy due to the cthe GSHP sy

To addrgrated to srm research direction.

: (1) that GSHP systems are not designed to functionystems to recover heat from buildings in summer, andrge amount of energy is consumed for building spaceFort McMurray due to extreme dry-cold weather. Tohese challenges, an integrated system is proposed toGSHP system, including solar heating and DWHR. Natu-ing boilers are another main heating contributor in this

ed methodology

mal energy is a sustainable and renewable resource. source is cost-effective, reliable, and environmentally-he system is properly designed. The primary challengeSHP systems is the task of maintaining a balance in

rgy. Normally, the GHE works both as a heating sys-

ter and a cooling system in summer in order to makeabsorbed equivalent to that rejected. Fig. 2(a) depicts

of the available thermal energy variance in the GHEer one year. The geothermal loop extracts heat from the

it is in heating mode in winter and the energy in the eldDuring summer, the eld temperature rises as energyed back into the ground. Fig. 2(b) demonstrates howle thermal energy in the eld uctuates while the waveins relatively consistent throughout the year, (despitelight decreases observed), if the GHE works efciently.al practice, the GSHP system in Stony Mountain Plaza isd as a cooling system in summer, since heating is morehan cooling for the given climate. In this case, the tem-

the GHE decreases gradually, exerting a negative impactthermal systems efciency. Fig. 3 demonstrates howd GHE temperature from the available thermal energynder these conditions. As shown by the dashed line inthe heating mode is active during the winter months,decreases, followed by only a slight increase in summerharacteristics of the earths surface. Thus, as years pass,stem may decline in effectiveness, as shown in Fig. 3(b).ess this challenge, solar and DWHR systems are inte-upport the GSHP system. The solar energy system


Fig. 2. GHE energy expected distribution by using GSHP for heating and cooling.

Fig. 3. GHE energy expected distribution by using integrated heating system.

directly injects its produced energy to GHE while the recycledheat from drain water increases the inlet temperature of the heatpumps and indirectly injects its energy to the GHE. Energy fromboth solar and intermittent drain water can therefore be collectedto recover tapproach isterm maint(b), where tin the abovedrain waterprovides sigdent GSHP is expectedwithin the cability. Theof the integ

3. Experimental design of the building heating monitoringsystem

Based on the previous analysis, the buildings under investiga-e designed to be served by integrated systems, includingrmal, solar energy, DWHR, and conventional electric or nat-as. F-side

totaildinllectencre. Theainagper lhe heat lost in the underground eld. The aim of this to use the integrated heating system to achieve long-enance of the GSHP system, illustrated in Fig. 3(a) andhe solid lines represent the targeted values. As advanced

discussion, combining the GSHP system with solar, and systems extends the lifetime of the GSHP system andnicantly more thermal energy than can an indepen-heating system. Coordinating these four main systems

to be energy-efcient and to provide thermal energyonstraints of budget, space, and energy resource avail-

following sections provide a more detailed discussionrated heating system for this project.

tion argeotheural gsourcewith athe buthe corectly ipumpsthe drlel copFig. 4. Heating system schematic with monitoring deig. 4 depicts the heating system schematic. On the of the heat pumps, the system provides solar panelsl surface area of 28.7 sq. m mounted on the roof ofg. Solar energy system circulates 13.6% methanol withd energy to recover the heat to the GHEs and indi-

ase the entering temperature of the water-to-water heat DWHR system, including eleven stacks that recyclee heat from seventy apartment units through paral-oops, increases the temperature from the GHE to thesign for case study.


rol alg

heat pumpsthe source-thermal enrenewable gas-burningbuilding wheach loop ibined, the tset point w

Fig. 4 illTwelve temusage sensocal room fogeneration addition, oing pipes asmeters, whbeen installbuilding pe

3.1. Origina

Each syTo be morestorage tanWhen the osystem heabased on vatemperaturnatural gas-boilers 1 anwhen the tset points opanels, the GHE loop wtemperaturalso considetion, the DWthe recovershows the rithm, whic

ne an hea

eachs, anr data

uatio

enerivedg sysal enc hepacie theal th

is de

M Fig. 5. Original heating system cont

, and indirectly recovers the heat to the GHE. Gatheringside energy, heat pumps powered by electricity produceergy with an expected COP of 2.8. In addition to theseenergy sources and purchased electric power, natural

boilers are utilized to provide additional heat to theen needed. The driving power to operate the pumps in

s supplied by electricity. Once these systems are com-emperature of the water storage tank is increased to ahich satises occupant requirements.ustrates the monitoring design with sensors locations.perature sensors, ten status sensors, and six powerrs have been designed and installed in the mechani-

r the purpose of monitoring the performance of energyfrom each heating system and the COP of heat pumps. Inw rate samples have been measured on the correspond-

well. Electrical meters, energy meters, and water usageich correlate to the heating system analysis, have alsoed in twelve out of seventy apartment units to monitorrformance [33].

with oof eachchangesavingfurthe

3.2. Eq

Theare deheatinTherma speciheat cato raisThe totwhich

Q = C l heating system control algorithm

stem is designed to collaborate under precise rules. specic, the outside temperature and the hot waterk set point temperature control the heating mode.utside temperature decreases below 15 C, the GSHP

ting mode turns on and four heat pumps start to workrious set point tank temperatures. When the outsidee falls below 20 C, the GSHPs switch off while twoburning boilers turn on. Heat pumps 1, 2, 3, and 4 andd 2 begin to heat water and transfer it to the water tankemperature of the water tank falls below the specicf 4447 C and 6371 C, respectively. As for the solarsolar heat transfer system is switched on to bolster thehen the temperature in the GHE loop falls below thee in the monitored solar panels. Freeze protection isred in order to protect the pipe from freezing. In addi-HR system is activated whenever water drains, and

ed heat is recycled to preheat water in the tank. Fig. 5owchart of the original heating system control algo-h species how the systems connect and collaborate

M = V

Q = C M = C

The COPcalculating consumed,

COP of He

277.78/

Productenergy prodnatural gas

Productio

(Energyorithm.

other. However, in reality, based on the performanceting system in the winter months, recommendations to

set point have been proposed in the interest of energyd further suggestions are still anticipated following

calibration analysis in the next few years of this study.

ns and calculations based on the collected data

rgy production and COP for the heat pump equations in order to estimate the energy generation from eachtem and to evaluate the performance of the heat pumps.ergy loss or gain (Q) in the pipes can be calculated usingat equationEq. (1). It should be noted that the specic

ty (C) in Eq. (1) is dened as the amount of heat required temperature of the unit mass of a substance by 1 C.ermal energy loss or gain is calculated satisfying Eq. (3),rived from Eqs. (1) and (2).

T (1)(2)

T = C Rm t (TSupply TReturn) Rv t (TSupply TReturn) (3)

represents the thermal efciency for power cycles bythe ratio of the heating output over the electrical energysatisfying Eq. (4).

at Pump = (Energy production from heat pump (GJ))(Heat pump power consumption (Kwh)) (4)

ion cost as discussed in this paper refers to the totaluction cost of the system. It is used for electricity and

production cost comparison.

n Cost = (Energy source unit cost ($)) source quantity)/(Energy production (GJ)) (5)


Table 1Circulating uid, corresponding sensors, and multipliers for each system (Legends refer to Fig.4).

System Fluid (%) Supply temp (C) Return temp (C) Flow rate (L/min) Specic heat (KJ/Kg. C) Density (Kg/M3)

Solar energy system 13.6 Methanol T5 T4 Flow3 4.00 971.68DWHR system 13.6 Methanol T12 T13 Flow6 4.00 971.68GSHP 15 Glycol T3 T1 Flow5 3.90 1016.98Boilers 15 Glycol T14, T15 T1 Flow4 3.90 1016.98

4. System performance and analysis

The designed sensors were installed in the mechanical roomon March 15, 2013 for the purpose of monitoring the performanceof energy generation from each heating system, as well as theCOPs. Data is being collected by the data management system andtransferred to the University of Alberta server at 20 s intervals. Byanalyzing the data obtained from monitoring, the production andefciency of the individual systems as well as of the integrated sys-tem can be ascertained. As a result of this research, valuable systemperformance patterns, user interface, and enhanced control systemcan be obtained by which engineers can make further adjustmentsto heating system designs. What remains of this section outlinesthe heating resources and system production analysis based on thedata collected during the period, March 15 to June 6, 2013. Circulat-ing uid, colisted in Tabin the moni

4.1. Solar p

Ten solabeen instalSolar paneltested unitcirculating energy to thon the secogenerated fitoring the secondary l

The solamonitored the reportea decreasinwinter to spand spring,early morni

outside temperature is below 2 C for freeze protection. As a result,10 to 20% of energy from the heating loop has been wasted by thesolar energy system at night in winter due to this freeze protection.Additionally, since the circulating pumps continued to operate,they led to further electricity wastage. The corresponding COP ofthe solar energy system increased from 7 to 30 corresponding toseasonally increasing temperatures, as summarized in Table 2. Thesolar energy system also performed with less efciency in winterthan it did in spring or summer.

In order to improve the COP of the solar energy system,more effective control of operation design can be used to makeadjustments to the existing solar energy system. Based on thisobservation, the solar loop circulating pump should run when thetemperature of the solar supply pipe is higher than the temperatureof the return pipe. In addition, the concentration of Tyfocor-L uid

olar be mear ets sa

readperaside ril), n th

can bjust

l cos systler videual on arologrom tage-baserese

ar enrresponding sensors and multipliers for each system arele 1. Legends in T and Flow in Table 1 are explainedtor design (Fig. 4) with the locations of sensors.

anels

r panels with a total area of 28.7 square meters haveled on the roof of the building to collect solar energy.s connect to a SHTS, which is a preinstalled and leak-

with integrated heat exchanger and Tyfocor-L uidthrough a primary loop. The SHTS transmits thermale underground eld through supply and return pipes

ndary loop with 13.6% methanol. The amount of energyrom the solar energy system can be estimated by mon-temperatures of the supply and return pipes on theoop.r energy system production is calculated by usingdata on a weekly basis, as presented in Fig. 6. Duringd time period, SHTS generated increasing energy withg proportion of wasted energy as the transition fromring and summer occurs. In general during the winter

the SHTS has been wasting energy at night and in theng because it is required to run every 20 min when the

in the sshould

A clpresenweeklycient oof outand Apbetweewaste This adationaenergythe coocan pro

Annbased Meteorates fpercensensorage repthe solFig. 6. Solar energy system production and energyprimary loop may be increased meanwhile, adjustmentsade to decrease the set point for freeze protection.nergy production pattern is observable in Fig. 7, whichmple solar energy production performance based onings every Friday during the reported period. The ef-ting period expands corresponding to the overall risetemperature from March to May. In winter (Marchlow solar heating system production is encounterede hours of 6 p.m. and 10 a.m. During this period, energye circumvented by avoiding running the primary loop.ment can save a considerable amount in annual oper-ts and make an improvement in the COP of the solarem by 1 to 2. In addition, during spring nights, due touid coming from the GHE loop, the solar energy system

a small amount of energy to recover the GHE.solar energy production estimation model is creatednnual sun radiation information from NASA Surfacey and Solar Energy [34] and the heat productionmeasurement for April and May, 2013. Energy wasted

and average efciency factor are considered in thisd monitoring and estimation. Energy wasted percent-nts the energy wasted due to the freeze protection ofergy system, which is the ratio of negative production to wasted (2013).

404 X. Li et al. / Energy and Buildings 72 (2014) 398410Ta

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the total energy production in a month. Efciency factor illustratesthe energy collected by the solar panels over the sun radiation,which is the ratio of positive production to sun radiation informa-tion. Assumptions have been made to estimate the energy wastedpercentagefactor is cal2013.

Q = Ra A

Thereforcan be estisolar panelin the correfrom the so50 GJ, peakproduction

4.2. Drain w

The builfrom the drpipe is entDWHR systto the ambito a main hloop pipes, from the drloop, and ttotal energadding up tstack whichtwo-bedrootemperaturply and retto 0.7 GJ inin Table 1.

In additiafter measufrom the enof a one-beda two-bedron the ratioof the seven6, 2013), thDWHR is bduction fro7.5 GJ. Theby the fracthot water, afrom the apyear, whichwill also remthe DWHR

The COPcirculating heat loop arecycled hethe circulatsystem. It istemperaturTo achieveconsumptiobetween threaches 0.31620 rang for the other ten months, while the average efciencyculated as 40% from the measurement of April and May,

vg(E) A t(1 + W%) (6)

e, the energy production from the other ten monthsmated by Eq. (6), where A represents the total area ofs, 28.7 m2 in this case, while t is the number of dayssponding month. Fig. 8 shows the monthly productionlar energy system, with an annual production of up to

monthly production of 8 GJ in June, and low monthly of less than 1 GJ in December.

ater heat recovery

ding includes eleven DWHR stacks which recycle heatain water from the 70 apartment units. Each drain waterwined with coil which contains circulating uid. Theems are wrapped with insulation to prevent energy lossent environment, and each heat recovery unit connectseat loop. By monitoring the drain water pipes and heatdata regarding the amount of thermal energy recycledain water pipe, thermal energy transferred to the heathe efciency of the heat transfer can be obtained. They savings from this system can thus be estimated byhe heat recovered from each unit. A particular DWHR

connects to four one-bedroom apartments and fourm apartments has been chosen for monitoring, ande sensors have been installed on corresponding sup-urn pipes. This DWHR stack alone could result in 0.5

weekly recycled energy based on the multipliers given

on, the average water usage per apartment is calculatedring water usage from twelve out of seventy apartmentsd of December, 2011.The average daily hot water usageroom apartment has been determined to be 100 l, while

oom can be expected to use up to 120 l per day. Based of water usage from one stack to the total water usagety apartments in the testing period (March 15 to Junee corresponding system energy recycled by the eleveneen appraised. Fig. 9 indicates the weekly energy pro-m the eleven DWHR systems, which range from 5.5 to

efciency of the DWHR system, which is determinedion between heat recycled and power energy used forpproximately stabilizes at 60%. The weekly water usageartments is found to be relatively constant through the

entails that the heat recycled from the DWHR systemain the same. In this case, the annual production from

can be estimated to be 350 GJ. of the DWHR system ranges from 6 to 8. Since thepumps on each unit and the pump on the main DWHRre always on, they waste energy and electricity. If theat cannot exceed the electricity energy usage to powering pump, it is not worthwhile to operate the DWHR

suggested that the DWHR system be controlled by thee difference between the supply and the return pipe.

energy production which is triple the rate of powern, each DWHR system has to run when the differencee supply and return pipes on the energy collection loop5 C. In this case, the COP of DWHR can increase to thee, with a 58% reduction in energy production. To attain


a higher COdifference bcollection loincrease toproduction.provide heenhance theFig. 7. Solar energy system production performance (sample data fo

Fig. 8. Solar energy system production prediction based on

Fig. 9. DWHR system energy production

P, each DWHR system runs when the temperatureetween the supply and return pipes on the energyop reaches 1.37 C, in which case the COP of DWHR can

the 2832 range, with a 2330% reduction in energy However, the purpose of utilizing DWHR is not toat to the building directly, but recover the GHE and

efciency of the GSHPs, i.e., a small amount of energy

injected to COP of 162

4.3. Ground

Eighty umately 90 mr Friday over the reported period).

annual sun radiation [34].

(2013).

the GHE can bolster GHE energy recovery. Therefore, a0 is adequate for this project, given in Table 2.

source heat pumps

nderground geothermal loops at a depth of approxi- serve as heat exchangers under the building. Four


ide te

uctio

water-to-wsystems anof the buildlating pipe solar heatinwater storapipe and r15 C but athe assumepump durinreported peas given inrelates to tportional tois calculateof weekly from heat expected, wpump.

The lowload tempeing to the loshould be mdensers on or by modithe heatingwhich is dimendationsof 3.23.3 afour heat putwo heat pmaintain th

irs ws.Fig. 10. Heat pump energy production vs. outs

Fig. 11. Geothermal GHE energy prod

ater heat pumps, which gather heat from the DWHRd solar heating system, are located in the basement

two pamonthing. On the source side of the heat pumps, a circu-connects to the geothermal GHE, DWHR systems, andg system. On the load side of the heat pumps, thege tank links to the heat pumps through the supplyeturn pipe. When the outside temperature is belowbove 20 C, heat pumps are ready to operate. Withd ow rate of 170 liters per minute (L/min) per heatg the testing period, heat pumps generated during theriod 182.8 GJ as output based on the measurement,

Fig. 10. The production from heat pumps apparentlyhe heating load requirements, and is inversely pro-

outside temperature. The total COP of heat pumpsd as approximately 2.6 by using the measurementenergy production and electricity consumption datapumps in Eq. (4). This COP value, 2.6, is lower thanith an average production rate of 3.0 MJ/min per heat

entering source temperature (EST) and high enteringrature (ELT) of the heat pumps are the main factors lead-w COP. To increase the COP of heat pumps, adjustmentsade either by adding more solar panels or large con-

the source side of the heat pumps to increase the EST,fying the set point of the tank temperature based on

load requirement in each specic outside temperature,scussed in section 5, to reduce the ELT. These recom-

can improve the COP of the heat pumps to the rangeccording to heat pump performance data. Furthermore,mps are currently in active mode, while generally onlyumps are required for heating in winter. In order toe heat pumps, the four heat pumps can be grouped into

4.4. Ground

The outplus the pothe energyin Fig. 11. spring andtures, whicHowever, itproductionannual datathe geotheif the amousummer isin winter, adjustmentfurther. Whwill yield m

Based on6, 2013), thsource sidement and cand GHE drpumps, resproductioncontrast to tem producthe apartmafter a longmperature (2013).

n (2013).

hich alternate operation, switching active every three heat exchanger

put energy of the heat pump equals the source inputwer usage of the heat pumps. From this methodology,

generated from GHE can be estimated, as illustratedClearly, the production of the GHE decreases in the

summer seasons with the warmer outside tempera-h is in accord with the previous theoretical analysis.

is inaccurate to predict the performance of GHE energy based on a few months results. Once comprehensive

is obtained, reliable forecasting of the performance ofrmal heating system will be carried out. For instance,nt of energy injected to the underground eld during

much greater than the amount of energy producedthe GHE will not decline in effectiveness; otherwise,s must be made before system performance declinesat is apparent is that a longer time period of monitoringore accurate results.

the rst twelve weeks of monitoring (March 15 to Junee energy production of each renewable source from

of heat pump (Fig. 12) is obtained from the measure-alculations. The solar energy system, DWHR system,ew 15, 71 and 14% of source-side production for heatpectively. To be more specic, the solar energy system

varies with the sun radiation from week-to-week inthe consistency of energy recycling that the DWHR sys-es because of the fairly stable weekly water usage ofents; the GHE energy production will be further deriveder period of monitoring.


n the

able

4.5. Boiler l

Boilers aheating mixculating thaused as an exception, gnatural gas for boilers processes abasement totant role wthe occupannatural gasthan electri

Followinsuring the tpipes, the tobtained. Eperatures omeasured, boilers werMarch, withwhich doub

A compaural gas is mheat pumpsaverage proature is aboof heat wheaverage proproduction Within the

ed ued bl gasFig. 12. Heat energy production from each renewable source o

Fig. 13. Energy production percentages between renew

oop

re used for generating heat for residential purposes byed uid (15% glycol) to a preset temperature and cir-

producprovidnaturat uid throughout the building. Natural gas is widelyimportant energy resource, and Fort McMurray is noiven that this particular geographic area has sufcientreserves underground. Natural gas is utilized as the fuelto heat the water, which can then be used for variousnd heating applications. Two boilers are installed in the

provide heat to the building. The boilers play an impor-hen the GSHP cannot satisfy the heat requirements ofts. When the outside temperature is lower than 20 C,

is selected as a more cost-effective heating resourcecity (used to power the heat pumps).g the same principles as given in other systems, by mea-emperature difference and ow rate on the circulatinghermal energy generated from the boilers can also beach boiler works with a ow rate of 303 L/min. Tem-f the supply and return pipes for boilers 1 and 2 arerespectively. The production results indicate that thee more active at the beginning of the testing period in

an average production rate of 5.5 MJ/min per boiler,les the production rate of the heat pump.rison between the paid resources of electricity and nat-ade according to the given energy production from the

and boilers. Heat pumps are found to operate with anduction rate of 3.0 MJ/min when the outside temper-ve 20 C, and the boilers operate as the sole sourcen the temperature falls below this threshold, with anduction rate of 5.5 MJ/min. Fig. 13 shows the energypercentage between renewable and paid resources.

se twelve weeks of monitoring, renewable resources

5. Heating

Space heof seventy ato obtain awas found tload is requone-bedroobased on mto April, 20are includeing consumconsumptioconsume uapproximatincluding emechanical

From thtoring systeentire buildinvestigatetemperaturIt illustratetemperaturperature isline, whichenhanced hing to this e source side of heat pumps (2013).

and paid resources (2013).

p to 55% of energy, while the other 45% of energy wasy the paid resources, comprising electricity (32%), and

(13%). consumption

ating energy usage meters were installed in twelve outpartment units at the end of December, 2011 in ordernnual heating consumption for the coming years. Ithat heating load is required in winter while no coolingired in summer. The average heating consumption ofm and two-bedroom units every hour was calculatedonitoring data in the testing period from May, 201213. 43 one-bedroom and 27 two-bedroom apartmentsd in this building. Therefore, the entire building heat-ption in every hour and the entire building heatingn per year are estimated. The entire building couldp to 500 GJ per year, with the peak monthly load ofely 110 GJ in December, as illustrated in Fig. 14, notnergy consumption from the basement, where only

equipment is located.e above analysis and data collection from the moni-m, the estimation of required hourly heating load foring and the data collection of outside temperature ared, with the relationship plotted in Fig. 15 with outsidee on the x-axis and hourly heating load on the y-axis.s the hourly heating requirement in relation to outsidee. No heating load is required when the outside tem-

above 15 C. A clear pattern is identied by the trend subsequently leads to the polynomial in Eq. (7). Theeating system control algorithm can be adjusted accord-quation, dening a lower set point for the water storage


tank based ture change

Load(T) = 2

where LoadT shows theFig. 14. Monthly building heating load vs. outsid

Fig. 15. Building heating loads vs. outside te

Fig. 16. Proposed heating system control a

on the load demand associated with outside tempera-s.

106T3 + 9 105T2 0.0044T + 0.0423 (7)

shows the hourly heating load requirement in GJ and outside temperature in C.

6. Conclus

This papprising a ssource-sidedrives the then storede temperature.

mperature.

lgorithm.

ion

er has investigated an integrated heating system com-olar energy system, DWHR system, and GHE as the

renewable resources for the heat pump. Electricityheat pump and produces the required heat, which is

in water storage tanks. The integrated heating system


operates in such a way that solar and DWHR assist the GSHP sys-tems. Boilers work as auxiliary heaters in winter, generating heatby burning natural gas. The heating system performance has beeninvestigated using the weekly energy production and COPs of eachheating syscontrol systwhich can ienergy savibeen drawncollected us

1. The propthe perfotion resuto enginheating s

2. Annual p50 GJ witmation. Tvaries thpeak proshow thacan be avproposed

3. The DWHwhich isThe annu350 GJ. Ti.e., it rec

4. The COPtively, wmonitoribe avoidenhance

5. With lonbe causeor even nGSHP. GSbetter-deimpleme

6. The COP assisted it is desigMcMurrament for

7. Recommtem by mgiven in highlightsumptionsystem a

Ostensibperformancmore accurbeen obtainGHE and cothe GHE wittion for thethe efcienyears. The psystem andengineers son cold-clim

Acknowledgements

This research work has been developed within the scope ofthe Stony Mountain Plaza project in Fort McMurray, Alberta,

. It isrta. rs: Cnt anering

Devll of

w, St

nces

l-Khothermooper(2011rnatiop Rea Staoope79..H. Ragraterm. E.H. Ratem foi, T. Snitorildingstainab

Choi, on ban, Z.lied rural Rps, G

ural Rhangethermt Pumtherms, 201anks,, BlackKulcarperat329rnatiot Pum

Wood grouidentiakirche pe100ang,

und-sim, J.

actua schoo. Zhaigraterg. Reoth, 09).. Metzs, Solang, Podel

. Radund s13) 22akircirce hergy 36hen, Lt pum11) 18tem generated by the monitoring system. An enhancedem has also been derived from the monitoring system,mprove the COP of the heating system in the interest ofng and high efciency. The following conclusions have

based on the results obtained from the empirical dataing the sensor based monitoring system.

osed monitoring design and calculations can capturermance of the heating system with energy produc-lts and efciency, which provides valuable outcomeseers for adjustment of the current system and futureystem design.roduction from the solar energy system can be up toh 28.7 m2 solar panels based on measurement and esti-he monthly production from the solar energy systemrough the year from less than 1 GJ in December to theduction of 8GJ in June. However, the research resultst there is energy waste during winter nights, whichoided by implementing the enhanced control system

in this study.R system continuously recycles heat from drainage,

approximately consistent for the observed duration.al production for the DWHR system is estimated to behis system can achieve an impressive efciency of 60%,ycles 60% of the thermal energy from the wastewater.s of solar and DWHR system are 20.8 and 7.6, respec-ith the existing control algorithm. From the proposedng and data analysis, unnecessary power usage shoulded when operating renewable resources, which canthe COPs to 22.0 and 16.8, correspondingly.g-term operation of GSHP, low efciency is believed tod by the fact that unbalanced heating and cooling loado cooling load to the GHE decreases the efciency ofHP systems run this risk in cold-climate regions unless asigned integrated system can be widely embraced andnted.of the integrated heating system with solar- and DWHR-GSHPs can achieve a COP in the range of 2.22.6 whenned only for heating in the cold-climate region of Forty. This integrated heating system still needs improve-

the purpose of energy saving.endations are made to enhance the efciency of the sys-aking adjustments to the existing control algorithm,

Fig. 16. The proposed changes in the control system areed. The ideas are to avoid the unnecessary power con-

and energy waste of solar energy system and DWHRnd to increase the COP of heat pump.

ly, twelve weeks of data are not adequate to predict thee of the GHE. A longer period of monitoring will provideate results. Once additional comprehensive data haveed, it will be possible to observe the performance of thempare the energy production and energy recovery fromh annual results, which will result in valuable informa-

design of the GSHP system, as well as for predictingcy of solar- and DWHR-assisted GSHPs in the comingercentage of energy production from the solar energy

DWHR system will also be claried, which will supportubsequent source-side design of the heat pump basedate heating demands.

Canadaof AlbesponsoagemeEngineing andthank aMorro

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[27] X. Chea(20 a multi-disciplinary research project by the UniversityThe authors would like to thank to NSERC and all theormode & Dickson Construction Ltd., Integrated Man-d Realty Ltd., Hydraft Development Services Inc., TLJ

Consultants, BCT Structures, and Wood Buffalo Hous-elopment Corporation. The authors would also like to

the contributors who made this research possible, Davideve Hughes and Gordon White.

ury, J. Bundschuh, M.C.S. Arriaga, Computational modeling of shallowal systems, in: CRC Pres/Balkema, The Netherlands, 2012.man, J. Dieckmann, J. Brodrick, Drain water heat recovery, ASHRAE J.) 5864.nal Ground Source Heat Pump Association, Ground Source Heat

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An Introduction to Thermogeology: Ground Source Heating and Cool-well Publishing Ltd., UK, 2008., D. Goricanec, J. Krope, Economy of exploiting heat from low-ure geothermal sources using a heat pump, Energy Build. 40 (2008).nal Ground Source Heat Pump Association Oklahoma, Ground Sourcep, http://www.igshpa.cn/htdocs/pages.asp?id=12 (April, 2012)., H. Liu, S.B. Riffat, An investigation of the heat pump performancend temperature of a piled foundation heat exchanger system for aal building, Energy 35 (2010) 49324940.i, D. Colak, Effect of a super heating and sub-cooling heat exchangerrformance of a ground source heat pump system, Energy 44 (2012)4.

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A framework to monitor the integrated multi-source space heating systems to improve the design of the control system1 Introduction1.1 Ground source heat pump system1.2 Objective and scope

2 Proposed methodology implementation2.1 Case study introduction2.2 Proposed methodology

3 Experimental design of the building heating monitoring system3.1 Original heating system control algorithm3.2 Equations and calculations based on the collected data

4 System performance and analysis4.1 Solar panels4.2 Drain water heat recovery4.3 Ground source heat pumps4.4 Ground heat exchanger4.5 Boiler loop

5 Heating consumption6 ConclusionAcknowledgementsReferences

space heating systems

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