Assessment of the Use of Solar Flat Plate Collectors for Solar Thermal Refrig...
BES 702 Technical Report (1)
1. SENECACOLLEGE
SCHOOL OF APPLIED ARTS AND TECHNOLOGY
Free Cooling
And the Earth Rangers Center
TECHNICAL REPORT
Julian Tersigni
Building Environmental Systems
17/6/2015
2. Free Cooling and the Earth Rangers Center
Prepared By: Julian Tersigni
Building Environmental Systems
Air Conditioning and Refrigeration: BES 702
Prepared For: Rafael Raghubir
3. Acknowledgments
I would like to thank my advisor, Rafael Raghubir for his time and guidance in the
completion of this report.
4. Abstract
The Earth RangersCenterisan environmental charitylocatedinVaughan,Ontario.The 60,000 ft2
facilityintegratesinnovative energy/waterconservationandcomfortstrategies.Thisreportdetails
free coolinganditsuse at the Earth RangersCenter(ERC) throughgeothermal technology.
6. 1.0 Introduction
A buildingownerhasanincreasedawarenessof energyconsumptionintheirfacilitywhetherit isa
residential,industrialorcommercial property. Globallythere isconcernoverclimate change andthe
role playedbyenergyconsumption. The sustainabilityof abuildingisanimportantissue asbuildings
consume 40% of the world’stotal energyuse.
1.1 Purpose
Thisreportdescribesthe conceptof free coolinganditssources. A specificexampleof itsuse is
examinedthroughacase studyof the Earth RangersCenter,a centerforshowcasingsustainable
technologies.Inthisfacilityfree coolingisaccomplishedthroughgeothermaltechnology.The
benefitsanddisadvantagesof free coolingisexaminedwhenaccomplishedthroughthistechnology.
2.0 Free Cooling-Whatisit?
Free coolingisa methodtolowerthe temperature inabuildingorspace byusingnaturallycooledair
or waterinsteadof mechanical refrigeration. 1
Withthismethod the systemreplaces achillerin
typical airconditioningsystems while attainingthe same coolingresult. Itcanbe usedforsingle
buildingsordistrictcoolingnetworks.2
Figure 1: Free Cooling Via Strainer Method1
2.1 Sources
Sourcesfor accomplishingfree coolingvarybutprimarilytheyare air, waterand ground. Airat many
elevationscanbe considerablycoolerduringcertainseasonsandtimesof daythanair withinaspace.
By filtering,humidifyingandintroducingcoolerairdirectlyintoaspace,it ispossible toreduce or
exclude the use of refrigerationequipment (Figure 1).A source of coldwaterfrom a local bodyof
watercan be circulatedintoaspace andusedinsteadof undergoingthe traditional methodof
refrigeratingaclosedwaterloopwithachiller. A geothermal system (Figure 2) consistsof aheat
exchange systemburiedbeneaththe groundanda mechanical refrigerationequipmentcomponent.
Whenoperatinginfree coolingmode the chillerforabuildingisbypassedandcirculateschilled
water/glycol fromthe groundintoaspace directlythroughaclosedlooporintocoolingcoils. Inall
7. cases,the industrial coolingsystemswouldonlybe neededwhenthe outsideairorground
temperaturesbecometoohighforfree coolingsystemstobe effective. 1
Figure 2: Free Cooling Via Geothermal Loops
2.2 ProlongedEquipmentLife
As a resultof reducedloadonconventional refrigerationequipment,the lifespanoncoolingsystems
can be significantlyextended.Reductionsincoolingsystemuse (Figure 3) alsomeanreductionsin
powerconsumptionandservice/repairs,loweringthe energyandmaintenance costsforfacility
owners.In reality,free coolingisnot completelyfree.Pumps,fansandotherair/water-handling
equipmentisneededwhich requiresperiodicservice.1
Figure 3: Reduced Load on Refrigeration Equipment Extends Lifespan
8. 3.0 Free Coolingatthe ERC usingGeothermal Tech
The Earth RangersCentre,locatedonthe conservationlandsof the KortrightCenterinVaughan,ON,
was builtin2004 as the base of operationsforEarth Rangers;a children focusedenvironmental
education organization. At60,000 ft2
, the buildingisLEED-Platinumcertifiedandwasbuiltwiththe
mandate to showcase awide-range of sustainable buildingtechnologiesandpracticesone of them
beingitsgeothermal systemwithradiantfloorheating/cooling.3
3.1 InstallationHistory
The geothermal systemconsistsof aseriesof 44 wells,drilleddowninto sand,gravel,glacial till and
finallyintoshale bedrockbeneaththe parkinglot(Figure 5).Priortoinstallation of the entirefieldof
wells,atesthole wasbored,anda thermal conductivitytestwasperformed tostudyheattransfer
(Figure 4). The testhole showedthatthe upper12 metersof the sand layer wasunsaturated
meaningitwouldnot holdor transferthermal energyaswell asif itwere saturated.The watertable
starts 32 metersbelowgroundlevel andwouldbe consideredpartof a highyieldaquifer.Totestthe
conductivityof the ground,andthusits suitabilityforageothermal system,a32mm diameterhigh
densitypolyethylene (HDPE) u-looppipewasinstalledinthe ground.The testshowedthatthe
bedrockimprovedthe thermal conductivityof the site,because the shale hashigherconductivity
than the load.4
Figure 4: Geosource Energy Drill Rigs at the ERC
9. Figure 5: Well Depths and Ground Materials
3.2 SystemSetUp
The geothermal systematthe Earth RangersCentre wasa retrofitinstalledin2010 duringa parking
lotexpansion.ItispoweredbyaCarrier30HXC chillerwithapproximately80tons of nominal heating
capacity.The groundloopbelowthe parkinglotconsistsof 44 vertical boreholesgoingdowntoa
depthof 120 m. The buildingusesaradiantin-floor/slabdistributionsystemforbothheatingand
cooling.Intotal there is22 km of tubingusedinthe radiantheatingandcoolingsystem.Highthermal
mass reducespeakheatingandcoolingdemand.
Whenoperatinginfree coolingmode acirculatorpumpdirectsthe water/glycol mix toaheat
exchangerwhere heatisremovedfromthe secondaryinteriorloop (Figure7).A modulatingvalve
bypassesthe chillerandthe chilledmixture is circulatedthroughthe coolingslabs. Inthismode the
onlyelectrical consumptionisthatconsumedbythe circulatorpumps,whichismuchlessthanthat
consumedbythe chiller,andthe somewhathighertemperaturesavailablewhennotusinga chiller
are fine giventhatthe coolingslabsare regulatedathighertemperaturesanywaysoasto be above
the dewpoint.4
10. Figure 6: Geothermal Manifolds
Figure 7: Geothermal Heat Exchanger with Primary and Secondary Loops and Pumps
4.0 Advantages
Free coolingmode workswell atthe ERC because of itsthermal massand large ceilingareasusedas
heattransfersurfaces.The groundtemperature inthe summermonthsremainslow enoughto
directlycool the ceilingslabswithoutthe use of refrigerationequipment. Inthiscase studya 60,000
ft2
facilitycanbe cooledwithonly 18 horsepowerinpumpingenergy.
Refrigerationequipmentisneededif humiditylevelsare high,andthe ventilationairmustbe
dehumidifiedtoensure comfortable airconditionswithinthe buildingspaces. Todate,the heat
removedfromthe geothermal systeminthe winterhasbeenbalancedbythe heatremovedfromthe
buildinginthe summer.The automationsystemisprogrammedtovaryhow it usesthe fieldto
maintainthisannual balance. 4
11. 5.0 Disadvantages
Since geothermal energyisnotexactlywidelyused the unavailabilityof equipment,staff,
infrastructure, andtrainingpose hindrance tothe installationof geothermal loopsinbuildings. Not
enoughskilledmanpowerandavailabilityof suitablebuildlocationpose seriousprobleminadopting
geothermal energyglobally. Geothermal energyrequires highinstallationcosts aswell requiring
available landandmaterial tobuildwells. Geothermalsitesalsoneedarecharge periodsothat in
summerwhenheatisrejectedintosurroundingearthmaterials Itcancool down again to use forthe
building.Inadditiontothiswellsare inaccessiblebeneath the groundmakingrepairworkdifficult
withthe added riskof damage due to seismicactivityinsome areas. 5
6.0 Conclusion
Sustainabilityinabuildingiscritical asithas a large impact
on global energyuse resultinginimpactsonclimate change.Facilityownersare concernedwith
allocatingmonetaryresourcesappropriatelywithcostssavingtargetsincreasingyear afteryear.Free
coolingisa successful methodof loweringbuildingtemperaturesinabuildingandthusitisa huge
cost/energysavingstool.Sourcesforfree coolingvarywithageothermal systemusingearth
temperaturesforheatexchange.Atthe Earth RangersCenterthe 60,000 ft2
facilitycanbe cooled
withonly18 horsepowerinpumpingenergyresultinginhuge savings.Geothermal energyisnotthe
mostcommon source of accomplishingfree coolingasinstallationcostsare highanda unavailability
of equipment,staff,infrastructure,andtraining hinderitsadoption.
