Chapter 2 Malaysias Weather Data Building Energy Efficiency
Technical Guideline for Passive Design (Draft 1) CKTang
Page2of30ForewordThis document is produced as part of Component 4,
Building Sector Energy Efficiency
Program(BSEEP)byCKTang([email protected])andNicChin([email protected]).The
views expressed in this document, which has been produced without
formal editing, are thoseof the authors and do not necessarily
reflect the views of neither JKR nor UNDP. Comments andopinions
from readers are encouraged and please email it to either
[email protected]
[email protected]:www.facebook.com/bseepc4CKTangJune6,2012
Page3of30Table of Contents 2
MalaysiasWeatherData(3rdDraft)...............................................................................................52.1
Introduction............................................................................................................................52.2
Sourceofweatherdata...........................................................................................................52.3
LocationandSunPath............................................................................................................62.4
DryBulbTemperature............................................................................................................82.4.1
DesignPotential..............................................................................................................82.4.2
DesignRisk......................................................................................................................92.4.3
ChartsandTableofRawData.........................................................................................92.5
WetBulbTemperature.........................................................................................................102.5.1
DesignPotential............................................................................................................102.5.2
DesignRisk....................................................................................................................102.5.3
ChartsandTableofRawData.......................................................................................112.6
HumidityRatio(MoistureContent)......................................................................................122.6.1
DesignPotential............................................................................................................122.6.2
DesignRisk....................................................................................................................122.6.3
ChartsandTableofRawData.......................................................................................132.7
DewPointTemperature........................................................................................................142.7.1
DesignPotential............................................................................................................142.7.2
DesignRisk....................................................................................................................142.7.3
ChartsandTableofRawData.......................................................................................152.8
RelativeHumidity..................................................................................................................162.8.1
DesignPotential............................................................................................................162.8.2
DesignRisk....................................................................................................................162.8.3
ChartsandTableofRawData.......................................................................................172.9
HorizontalGlobalRadiation..................................................................................................182.9.1
ChartsandTableofRawData.......................................................................................182.10
DiffuseSolarRadiation..........................................................................................................192.10.1
ChartsandTableofRawData.......................................................................................192.11
DirectSolarRadiation...........................................................................................................202.11.1
ChartsandTableofRawData.......................................................................................202.12
ComparisonofGlobal,DirectandDiffuseRadiation............................................................212.12.1
DesignPotential............................................................................................................21Page4of302.12.2
DesignRisk....................................................................................................................212.12.3
ChartsandTableofRawData.......................................................................................222.13
CloudCover(Oktas)..............................................................................................................222.13.1
DesignPotential............................................................................................................232.13.2
DesignRisk....................................................................................................................232.13.3
ChartsandTableofRawData.......................................................................................232.14
EffectiveSkyTemperature....................................................................................................242.14.1
DesignPotential............................................................................................................242.14.2
DesignRisk....................................................................................................................252.14.3
ChartsandTableofRawData.......................................................................................252.15
GroundTemperature............................................................................................................262.15.1
DesignPotential............................................................................................................262.15.2
DesignRisk....................................................................................................................262.16
WindSpeed...........................................................................................................................272.16.1
DesignPotential............................................................................................................272.16.2
DesignRisk....................................................................................................................272.16.3
ChartsandTableofRawData.......................................................................................282.17
WindDirection&HoursofAirTemperaturebelow29C.....................................................292.17.1
DesignPotential............................................................................................................292.17.2
DesignRisk....................................................................................................................292.17.3
WindChartsofAirTemperatureBelow29C...............................................................30Page5of302Malaysias
Weather Data2.1Introduction
AclearunderstandingofMalaysiasweatherdataenablesdesignertodesignbuildingthatresponseto
the climate instead of against it. The climate in Malaysia is
fairly consistent daily for the
entireyear;thereforeitisusefultogetanoverviewofanaveragedayperformanceandthemaximumandminimum
hourly weather data for a full year. This chapter provides
information on dry
bulbtemperature,wetbulbtemperature,relativehumidity,humidityratio(moisturecontent),dewpointtemperature,
global radiation, direct radiation, diffuse radiation, cloud cover
and wind speed &direction, effective sky temperature and ground
temperature. Charts are provided for ease ofunderstanding the data
and table of raw cross tabulation data made using pivot table
function inExcel is also provided for users who wish to make use of
these data for more indepth analysis ontheirown.2.2Source of
weather data The hourly weather data of Kuala Lumpur used in this
chapter was based ona Test Reference Year(TRY)1 weather data
developed in University Teknologi Malaysia (UiTM) under DANCED
(DanishInternationalAssistant)projectforEnergySimulationsforBuildingsinMalaysia.TheTRYisbasedon21years(1975to1995)ofweatherdatafromtheMalaysianMeteorologicalStationinSubang,KlangValley,Selangor.ThehourlyweatherdatathatwereobtainedfromthisstationisasshowninTablebelow.Table2.1:WeatherdatacollectedinSubangSubangMeteorologicalStation(KlangValley,Selangor,Malaysia)Longitude:101deg33'Latitude:3deg7'Parameters(hourly2)
UnitsCloudcover [oktas]Drybulbtemperature [C]Wetbulbtemperature
[C]Relativehumidity [%]Globalsolarradiation [100*MJ/m]Sunshinehours
[hours]Winddirection [deg.]Windspeed [m/s]
ATestReferenceyear(TRY)consistsofweatherdataforagivenlocation.InorderfortheTRYtoberepresentativeoftheclimateitwasconstructedonthebasisofatleast10yearsweatherdata.TheTRY
is made up from actual monthly data (not average values) that are
picked after having beensubjectedtodifferenttypesofanalysis.It
should be noted that typical energy simulation program require 2
extra data that were notcollected by the Malaysian Meteorological
Service, namely the direct and diffuse radiation. The1 Reimann, G.
(2000) Energy Simulations for Buildings in Malaysia, Test Reference
Year, 18-25.2 The values are integrated over a period of one hour,
but the exact time interval has not been specified.
Page6of30missing radiation data was calculated for the TRY via Erbs
Estimation Model from the
horizontalglobalsolarradiation.Althoughnotperfect,theTRYiscurrentlytheonlyknownsetofweatherdataforenergysimulationthat
was compiled based on statistical analysis and it has been used in
many energy simulations ofvarious buildings in Malaysia with
satisfactory results. This weather data was also used for
thedevelopment of the constants in the Overall Thermal Transmission
Value (OTTV) equation found
intheMalaysiaStandard(MS)1525(2007),EnergyEfficiencyinNonResidentialBuilding.2.3Location
and SunPath
Theglobalpositionandsolarnoonofsix(6)citiesinMalaysiaprovidedinTable2.2.Table2.2:GlobalPositioningandSolarNoonof6CitiesinMalaysiaLocations
Latitude(N) Longitude(E) SolarNoon1.KualaLumpur(Subang) 3.12 101.55
13:112.Penang 5.30 100.27 13:163.JohorBharu 1.48 103.73
13:024.KotaBharu 6.17 102.28 13:085.Kuching 1.48 110.33
12:366.KotaKinabalu 5.93 116.05
12:13SunPathdiagramfor6locationsaboveispresentedinthissectionandshowedthatthesunpositionisalmostthesameforallsix(6)locations,exceptforthehourofthesolarnoon.Solarnoon(whenthesunisatitshighestpoint)is13:11inKualaLumpur,whileinKotaKinabaluitis1hourearlierat12:13.The
sun path is generally eastwest with the sun approximately 25 to the
north during
summersolsticeand25tothesouthduringwintersolsticeforalllocationsinMalaysia.Thesunpathdiagramisausefultooltohelpinthedesignofexternalshadingdevices.Thesunpathdiagramisusedtoestimatesunangleatvarioustimeofdayandyear,allowingarchitectstodesignshadingdevicestoblockorallowdirectsunlightatwhatevertimeorday.
Page7of30Chart2.1:SunpathofKualaLumpur
Chart2.2:SunpathofPenangChart2.3:SunpathofJohorBharu
Chart2.4:SunpathofKotaBharuChart2.5:SunpathofKuching
Chart2.6:SunpathofKotaKinabaluPage8of30Chart2.7:LargeSunpathofKualaLumpur2.4Dry
Bulb Temperature The daily average, maximum and minimum dry bulb
temperature is provided by the chart in thissection. The standard
deviation is more than 2C from 2pm to 6pm indicating that the
afternoonhourshaveahigherchangeoftemperaturefromdaytoday;whileinthehoursofmidnightto7am,thestandarddeviationofthedrybulbtemperatureislessthan1C,indicatingafairlyconsistentandpredictabledrybulbtemperaturefrommidnighttoearlymorninghours.Theaveragedrybulbtemperatureofthewholeyear(includingdayandnight)is26.9C.The
average peak dry bulb temperature is just below 32C at the hour of
1pm to 2pm, while
themaximumdrybulbtemperatureoftheTRYis35.6Cat3pm.The average low
dry bulb temperature is 23.7C at 6am in the morning; while the
lowest dry
bulbtemperatureoftheTRYis20.6at7aminthemorning.2.4.1DESIGN
POTENTIAL The understanding of the dry bulb temperature allows a
clear appreciation of when naturalventilation will work and when it
is not likely to work. In addition, data center designers can
alsomakeuseofthisknowledgetoprovidenaturalventilationtothecomputerserverwheneverpossibletosavesignificantamountofairconditioningenergy.Page9of302.4.2DESIGN
RISK TheTRYis21yearsofweatherdatain
SubangAirportfromyear1975to1995.During theseyears,the Subang
Airport location is fairly well surrounded by greeneries. The peak
dry bulb
temperatureincitiesisexpectedtobehigherduetourbanheatislandeffect.2.4.3CHARTS
AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev. 1:00:00
AM24.622.527.00.9 2:00:00 AM24.322.026.80.9 3:00:00
AM24.121.826.50.9 4:00:00 AM23.921.526.30.9 5:00:00
AM23.821.026.20.9 6:00:00 AM23.720.826.00.9 7:00:00
AM23.820.626.30.9 8:00:00 AM25.222.128.51.1 9:00:00
AM27.322.830.81.4 10:00:00 AM29.023.732.41.5 11:00:00
AM30.123.833.41.5 12:00:00 PM30.923.934.01.7 1:00:00
PM31.322.334.81.9 2:00:00 PM31.324.135.22.1 3:00:00
PM30.723.435.62.5 4:00:00 PM29.823.234.82.6 5:00:00
PM28.923.433.82.4 6:00:00 PM28.023.433.02.1 7:00:00
PM26.923.330.41.7 8:00:00 PM26.223.029.81.4
20222426283032343612:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMDegreeCelciusDryBulbTemperatureAverage
Minimum MaximumPage10of309:00:00 PM25.722.828.81.2 10:00:00
PM25.422.828.61.1 11:00:00 PM25.022.828.11.0 12:00:00
AM24.822.528.00.9 2.5Wet Bulb Temperature The wet bulb temperature
is fairly consistent between day and night and throughout the year.
Theaverage peak of the wet bulb temperature is 25.4C at 2pm, while
the maximum wet
bulbtemperatureintheTRYis28.4Cat2pm.Theaveragelowofwetbulbtemperatureis23.1Cat6am,andthebottomwetbulbtemperatureintheTRYis19.9Cat7aminthemorning.2.5.1DESIGN
POTENTIAL
Thewetbulbtemperatureisagoodindicatorofthepotentialofdirectevaporativecoolingstrategy.If
the direct evaporative cooling system is 100% efficient, the lowest
air temperature of aevaporative cooling system achievable is the
wet bulb temperature. The efficiency of directevaporative cooling
devices depends on the system water droplet size, wetted surface
area and
airspeedandhasefficiencyupto90%3.Duringdaytime,thedrybulbtemperatureissignificantlyhigherthan
wet bulb temperature; therefore, evaporative cooler will work well.
However, during nighttime, the dry bulb temperature is very close
to the wet bulb temperature, the effectiveness ofevaporative
cooling is reduced significantly, i.e. the reduction of air
temperature is very small
withtheuseofevaporativecooling,evenat90%efficiency.Thewetbulbtemperatureisalsoaveryimportantfactorforsizingandpredictingtheperformanceofcoolingtower.Thelowerthewetbulbtemperature,thebetteristheperformanceofthecoolingtower.Ashraerecommendsdesigninganapproachtemperatureofthecoolingtowertobe5.5Ctothewetbulbtemperature.Thelowerthecondenserwatertemperatureasitexitsfromthecoolingtower,
the more efficient it is for the performance of the chiller. Based
on the TRY data, it will bebest to run the chiller early in the
morning, when the wet bulb temperature is lowest, to
gainmaximumefficiencyfromthechiller.Unfortunatelymostbuildingsareoccupiedfrom8amonwardsand
the use of thermal storage solutions will normally introduce
further inefficiencies that
maynegateanyefficiencygainedbyrunningthechillersystemintheearlymorninghours.2.5.2DESIGN
RISK
Thewetbulbtemperatureisnotaffectedmuchbyurbanheatislandeffect.Therefore,thewetbulbtemperatureprovidedbytheTRYisreliabletobeused.3
http://www.wescorhvac.com/Evaporative%20cooling%20white%20paper.htm
Page11of302.5.3CHARTS AND TABLE OF RAW DATA
HoursAverageMinimumMaximum Std Dev. 1:00:00 AM23.821.926.00.7
2:00:00 AM23.621.525.80.7 3:00:00 AM23.521.325.40.8 4:00:00
AM23.320.925.40.8 5:00:00 AM23.220.725.20.8 6:00:00
AM23.120.125.00.8 7:00:00 AM23.219.925.20.8 8:00:00
AM23.921.125.90.8 9:00:00 AM24.521.926.50.8 10:00:00
AM24.822.326.90.9 11:00:00 AM25.022.126.90.9 12:00:00
PM25.222.627.20.8 1:00:00 PM25.322.227.40.9 2:00:00
PM25.422.528.41.0 3:00:00 PM25.322.427.81.0 4:00:00
PM25.222.427.81.0 5:00:00 PM25.022.427.50.9 6:00:00
PM24.821.927.30.9 7:00:00 PM24.722.626.90.8 8:00:00
PM24.522.226.70.8 9:00:00 PM24.422.126.30.8 10:00:00
PM24.222.026.40.8 11:00:00 PM24.121.926.30.7 12:00:00
AM23.922.026.00.8
1820222426283012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMDegreeCelciusWetBulbTemperatureAverage
Minimum MaximumPage12of302.6Humidity Ratio (Moisture Content) The
humidity ratio or moisture content of the TRY weather data is
fairly consistent throughout
theyear.TheaveragemoisturecontentintheTRYis18.3g/kgandisconsistentdayornight.Daytodayfluctuationishighestat2pmintheafternoonwithapeakstandarddeviationof1.6g/kg.2.6.1DESIGN
POTENTIAL
Thehumidityratiogiveusinformationabouthowmuchwaterisinonekilogramofair,therefore,itgives
a potential water quantity that can be squeezed out from the air.
The following
knownmethodologiesforsqueezingwateroutfromtheairare:Coldsurfacesthatarebelowthedewpointtemperature.Desiccantmaterialthatabsorbmoisturefromtheair.A
clear understanding of humidity ratio (moisture content) provides a
very useful method
forengineerstoestimatetheamountoflatentloadandcondensationratethatthesystemneedtobedesignedfor.Forexample,thehumidityratioprovidesanindicationofamountofwaterthatneedsto
be extracted from the outdoor air to supply airconditioned air at
11C and 100% relativehumidity (approximately 8.2 g/kg) at the
cooling coil (offcoil condition). As the average moisturecontent of
outdoor air in Malaysia is 18.3 g/kg, an average extraction of 10.1
gram of water
fromeachkilogramofoutdoorairisrequiredtoprovideasupplyofairconditionedairat11Cand100%relativehumidity.ThisvalueprovidesanapproximationofcondensationrateoftypicalcoolingcoilinMalaysianairhandlingunitsduetointakeoffreshair.2.6.2DESIGN
RISK Water features and greeneries would increase the moisture
content in the air.
Duringphotosynthesisprocess,greeneriesexpelmoisturefromleavestoprovideevaporativecoolingtotheenvironment.Therefore,itisnotnecessarytruethatplacingfreshairintakeductneartogreeneries(totakeincoolerair)willyieldlowerenergyusebecauseitmayhavehighermoisturecontentinit.
Page13of302.6.3CHARTS AND TABLE OF RAW DATA HoursAverage
MinimumMaximumStd Dev. 1:00:00 AM18.415.021.30.9 2:00:00
AM18.214.620.80.9 3:00:00 AM18.114.820.50.9 4:00:00
AM17.915.320.50.9 5:00:00 AM17.815.020.30.9 6:00:00
AM17.714.420.00.9
1214161820222412:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMg/kgMoistureContentAverage
Minimum
Maximum0.0%0.0%0.2%0.8%2.6%9.1%25.4%36.2%20.0%5.0%0.7%0.1%0.0%0.0%0%5%10%15%20%25%30%35%40%%ofHoursinaYearMoistureContent(g/kg)MoistureContentPage14of307:00:00
AM17.814.220.00.9 8:00:00 AM18.314.820.71.0 9:00:00
AM18.315.121.11.1 10:00:00 AM18.113.821.01.2 11:00:00
AM17.913.720.71.3 12:00:00 PM17.913.521.01.3 1:00:00
PM17.913.221.21.4 2:00:00 PM18.013.023.71.6 3:00:00
PM18.213.221.61.5 4:00:00 PM18.413.922.21.5 5:00:00
PM18.414.422.61.3 6:00:00 PM18.615.122.61.2 7:00:00
PM18.815.121.71.1 8:00:00 PM18.814.921.71.0 9:00:00
PM18.815.021.41.0 10:00:00 PM18.715.121.20.9 11:00:00
PM18.715.021.20.9 12:00:00 AM18.515.120.90.9 2.7Dew Point
Temperature The dew point temperature is directly linked to the
moisture content in the air. However, the dewpoint temperature has
the advantage of providing us information on the condensation risk
due
toexposuretooutdoorair.Anysurfacetemperaturethatisbelowthedewpointtemperaturewillhavecondensationonit.TheaveragedewpointtemperatureintheTRYis23.4Candisfairlyconsistentdayornightandthroughouttheyear.Thepeakstandarddeviationofthedewpointtemperatureis1.5Cat2pmintheafternoon.More
than 70% of the hours, the dew point temperature is below 24C and
more than 95% of
thehoursthedewpointtemperatureisbelow25C.2.7.1DESIGN POTENTIAL
Thedewpointtemperatureprovidesanindicationwhencondensationwilloccur.Aslongassurfacetemperatureiskeptabovethedewpointtemperature,therewillbenocondensation.Forexample,ifasurfacetemperature
exposedtooutdoorairiskeptabove25C,therisk ofcondensationislessthan
5% and above 26C, the risk of condensation is less than 0.5%. This
provides a possibility
toprovideradiantcoolingtooutdoorarea(e.g.alfrescodinning,etc.)wherethesurfacetemperaturecan
be kept above the dew point temperature to avoid condensation while
minimizing
energyconsumptiontocooloccupantsinanoutdoorspace.2.7.2DESIGN RISK
If there are water features, greeneries and cooking done
(evaporation of water) within the space,the moisture content in the
air may increase and causes the dew point temperature to increase
aswell.Therefore,condensationmayoccurathighersurfacetemperatureduetothesemicroclimaticconditions.Page15of302.7.3CHARTS
AND TABLE OF RAW DATA HoursAverage MinimumMaximumStd Dev. 1:00:00
AM23.520.325.90.8 2:00:00 AM23.419.825.50.8 3:00:00
AM23.220.125.30.8 4:00:00 AM23.120.625.30.8 5:00:00
AM23.020.325.10.8 6:00:00 AM22.919.624.90.8
1719212325272912:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMDegreeCelciusDewPointTemperatureAverage
Minimum Maximum0.0% 0.0% 0.1%0.5%1.9%7.0%22.7%41.0%22.5%4.0%0.3%
0.0%
0.0%0%5%10%15%20%25%30%35%40%45%%ofHoursinaYearDewPointTemperature(degreeCelcius)DewPointTemperaturePage16of307:00:00
AM22.919.424.90.8 8:00:00 AM23.420.125.40.8 9:00:00
AM23.420.425.71.0 10:00:00 AM23.219.025.71.1 11:00:00
AM23.018.825.41.2 12:00:00 PM23.018.625.71.2 1:00:00
PM23.018.325.81.3 2:00:00 PM23.118.027.71.5 3:00:00
PM23.318.326.11.4 4:00:00 PM23.419.126.61.4 5:00:00
PM23.519.626.91.2 6:00:00 PM23.720.426.91.0 7:00:00
PM23.820.426.20.9 8:00:00 PM23.920.226.20.9 9:00:00
PM23.920.326.00.8 10:00:00 PM23.820.425.80.8 11:00:00
PM23.720.325.80.8 12:00:00 AM23.620.425.60.8 2.8Relative
HumidityRelativehumidityisameasureoftheamountofwater(moisture)inairascomparedtothemaximumamountofwatertheaircanabsorb,expressedinpercentage.Itisnotadirectindicatorofhowmuchwaterisintheair,asprovidedbythehumidityratio(moisturecontent)ordewpointtemperature.Thedrybulbtemperaturedeterminesthemaximummoisturetheaircanabsorb;therefore,relativehumidityisdirectlylinkedtoboththehumidityratio(moisturecontent)aswellasdrybulbtemperature,expressedinpercentageofmoistureintheair.Duetothereasonthatmoisturecontentintheairisfairlyconstantdayornight,thechangesofrelativehumidityisstronglyrelatedtothedrybulbtemperatureoftheair.Duringnighttimeandearlymorninghourswhenthedrybulbtemperatureislow;therelativehumidityisveryhigh(between90%to100%relativehumidity).Howeverduringdaytimehourswhenthedrybulbtemperatureishigh;therelativehumidityhasanaveragelowof62%.2.8.1DESIGN
POTENTIAL A low relative humidity is an indication of how well
evaporative cooling will work. The lower therelative humidity, the
easier it is for water to evaporate to reduce the dry bulb air
temperature. Atvery high relative humidity level, 90% or more, very
small amount of water will be able to beevaporated.2.8.2DESIGN RISK
Relativehumidityisafactorofbothdrybulbtemperatureandmoisturecontent.Itisnotpossibletocompute
energy change when provided with relative humidity alone. For
example, how muchenergy will it take to reduce relative humidity of
90% to 50%? It would not be possible to give ananswer to such a
question. However, it will be possible to compute the energy change
if thequestionisrephrasedintohowmuch
energywillittaketoreducerelativehumidityof90%at25Ctoarelativehumidityof50%at23C.Relativehumidityisusefulasanindicatorofmoistureintheaironlywhenprovidedwiththedrybulbtemperature.Page17of302.8.3CHARTS
AND TABLE OF RAW DATA HoursAverage MinimumMaximumStd Dev. 1:00:00
AM93.9731003.7 2:00:00 AM94.5721003.5 3:00:00 AM94.8751003.2
4:00:00 AM95.1811003.1 5:00:00 AM95.4841002.8 6:00:00
AM95.4851002.8 7:00:00 AM95.0821002.9 8:00:00 AM89.9751004.2
9:00:00 AM79.662987.0 10:00:00 AM71.650967.8 11:00:00 AM66.247977.9
12:00:00 PM63.644958.3 1:00:00 PM62.042998.9 2:00:00 PM62.7409710.7
3:00:00 PM66.0409712.0 4:00:00 PM70.0409713.0 5:00:00
PM73.6479812.3 6:00:00 PM78.3519910.7 7:00:00 PM83.758988.6 8:00:00
PM87.262986.8 9:00:00 PM89.669995.5 10:00:00 PM91.273984.8 11:00:00
PM92.672994.2 12:00:00 AM93.3731004.0
3540455055606570758085909510010512:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMpercentage(%)RelativeHumidityAverage
Minimum MaximumPage18of302.9Horizontal Global Radiation
Theaverageglobalradiationisalmostaperfectsymmetrybetweenthemorninghoursandafternoonhourswithpeakclosetosolarnoon.Theaveragepeakis636W/mat1pmwhiletheabsolutepeakintheTRYis1077W/mat2pm,westernsun.Theabsolutepeakofsolarradiationisalmostdoubleoftheaveragepeak.Thisindicatesthattherearedayswherethecloudscoverarelow,allowingdirectsolarradiationtocausehighsolargaininbuildings.Howeveronaverage,thecloudcoverintropicalclimateprovidesgoodprotectiontoreducetheimpactofdirectsolarradiation.TheTRYdataalsoshowedthatitispossibleatanytimeofdayforthesolarradiationtobereducedclosetozero,mostlikelycausedbyheavyraincloudcovers.2.9.1CHARTS
AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev. 1:00:00
AM0.00.00.00.0 2:00:00 AM0.00.00.00.0 3:00:00 AM0.00.00.00.0
4:00:00 AM0.00.00.00.0 5:00:00 AM0.00.00.00.0 6:00:00
AM0.00.00.00.0 7:00:00 AM7.70.029.25.7 8:00:00 AM87.50.0259.142.4
9:00:00 AM253.60.0516.290.7 10:00:00 AM429.00.0692.8125.4 11:00:00
AM565.738.9844.3143.2 12:00:00 PM631.0120.81006.4161.3 1:00:00
PM635.9161.11003.7173.8 2:00:00 PM589.236.11076.5186.7
02004006008001000120012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMwatt/m2GlobalRadiationAverage
Minimum MaximumPage19of303:00:00 PM474.623.7958.0189.3 4:00:00
PM335.20.0759.7169.7 5:00:00 PM205.70.0532.7122.8 6:00:00
PM93.20.0254.162.4 7:00:00 PM20.00.067.716.7 8:00:00
PM0.70.011.11.7 9:00:00 PM0.00.00.00.0 10:00:00 PM0.00.00.00.0
11:00:00 PM0.00.00.00.0 12:00:00 AM0.00.00.00.0 2.10 Diffuse Solar
Radiation
Theaveragepeakdiffuseradiationis356W/mat1pm,whiletheabsolutepeakdiffuseradiationis460W/malsoat1pm.Thestandarddeviationisgenerallylow,withthehighestat80W/mat4pmintheafternoon.2.10.1
CHARTS AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev.
1:00:00 AM0.00.00.00.0 2:00:00 AM0.00.00.00.0 3:00:00
AM0.00.00.00.0 4:00:00 AM0.00.00.00.0 5:00:00 AM0.00.00.00.0
6:00:00 AM0.00.00.00.0 7:00:00 AM7.70.029.25.7 8:00:00
AM62.80.0116.120.7 9:00:00 AM153.80.0227.138.8 10:00:00
AM231.40.0316.250.8 11:00:00 AM290.438.7386.158.0 12:00:00
PM334.4119.7434.062.9
05010015020025030035040045050012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMwatt/m2DiffuseRadiationAverage
Minimum MaximumPage20of301:00:00 PM356.2158.9459.762.5 2:00:00
PM344.136.0453.369.8 3:00:00 PM298.423.6415.978.8 4:00:00
PM228.10.0350.180.4 5:00:00 PM152.30.0272.569.8 6:00:00
PM76.10.0163.341.4 7:00:00 PM18.80.057.114.6 8:00:00
PM0.70.011.11.7 9:00:00 PM0.00.00.00.0 10:00:00 PM0.00.00.00.0
11:00:00 PM0.00.00.00.0 12:00:00 AM0.00.00.00.0 2.11 Direct Solar
Radiation
Theaveragepeakdirectradiationis297W/mat12noon,whiletheabsolutepeakdirectradiationis865W/mat2pmintheafternoon.Theabsolutepeakdirectsolarradiationisalmost3higherthantheaveragepeakdirectsolarradiation.Thestandarddeviationisratherhigh,withthehighestat194W/mat2pmintheafternoon.AllthesedataindicatesthatthereisasignificantdifferencebetweentheaverageandtheabsolutepeakdirectradiationintheTRY.Itisalsoquiteclearfromthedirectradiationchartthattheaveragedirectradiationishigherinthemorninghoursthantheafternoonhours.However,theabsolutepeakdirectsolarradiationoccursintheafternoonhour.2.11.1
CHARTS AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev.
1:00:00 AM0.00.00.00.0 2:00:00 AM0.00.00.00.0
0100200300400500600700800900100012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMwatt/m2DirectRadiationAverage
Minimum MaximumPage21of303:00:00 AM0.00.00.00.0 4:00:00
AM0.00.00.00.0 5:00:00 AM0.00.00.00.0 6:00:00 AM0.00.00.00.0
7:00:00 AM0.00.00.00.0 8:00:00 AM24.70.0203.238.2 9:00:00
AM99.80.0433.197.1 10:00:00 AM197.60.0572.2146.1 11:00:00
AM275.20.2677.7171.1 12:00:00 PM296.71.2840.6190.6 1:00:00
PM279.72.3821.7193.0 2:00:00 PM245.10.1864.5194.2 3:00:00
PM176.20.0792.2169.6 4:00:00 PM107.00.0621.7125.4 5:00:00
PM53.40.0401.076.0 6:00:00 PM17.20.0160.831.4 7:00:00
PM1.20.030.64.0 8:00:00 PM0.00.00.00.0 9:00:00 PM0.00.00.00.0
10:00:00 PM0.00.00.00.0 11:00:00 PM0.00.00.00.0 12:00:00
AM0.00.00.00.0 2.12 Comparison of Global, Direct and Diffuse
Radiation Placing the average global, direct and diffuse radiation
in the same chart provides a distinctunderstanding that the average
direct solar radiation is more intense in the morning while
theaveragediffuseradiationismoreintenseintheafternoonhours.2.12.1
DESIGN POTENTIAL
Itisimportanttoshadethewesternfaadefromdirectsolarradiationtoreducepeakcoolingloadinbuildings.Thepeakcoolingloadinbuildingdeterminesthesizeofairconditioningequipmenttobeprovided.Howeverforenergyefficiency,theplotofaveragesolarradiationsshowedthatitismoreimportant
to shade the eastern faade from direct solar radiation to reduce
annual energyconsumptioninbuilding.2.12.2 DESIGN RISK
ThedirectanddiffuseradiationintheTRYisnotameasuredvaluebutcomputedfromthemeasuredhorizontal
global radiation using via Erbs Estimation Model. However, the
result generally
agreeswithdailyobservationofsolarradiationinthisclimate.Thetropicalclimatethatitrainsmoreoftenin
the afternoon than in the morning provided the skies with an
averagely heavier cloud covers
intheafternoonthaninthemorning.Page22of302.12.3 CHARTS AND TABLE OF
RAW DATA 2.13 Cloud Cover (Oktas)
ThecloudcoverintheTRYismeasuredinOktasunit.OktasisdefinedbytheWorldMeteorologicalOrganizationasprovidedbythetablebelow4.OktasDefinitionCategory
0Sky clearFine 11/8 of sky covered or less, but not zeroFine 22/8
of sky coveredFine 33/8 of sky coveredPartly Cloudy 44/8 of sky
coveredPartly Cloudy 55/8 of sky coveredPartly Cloudy 66/8 of sky
coveredCloudy 77/8 of sky covered or more, but not 8/8Cloudy 88/8
of sky completely covered, no breaksOvercast
ThecloudcoverisgenerallyhighintheTRYandisreflectiveofatropicalclimate.TheaveragecloudcoverhasanOktasof6.8inMalaysiaandisfairlyconsistentdayandnightandthroughouttheyear.ThemaximumcloudcoverhasthemaximumOktasof8andcanoccursatanytimeofday.Howeverthe
minimum Oktas 0 is recorded by the TRY happening at 6am and 7am in
the early morning
andtheminimumcloudcoverintheafternoonisatleast1Oktashigherthaninthemorning,indicatingthatminimumcloudcoverisheavierintheafternoonthaninthemorning.4
http://worldweather.wmo.int/oktas.htm
010020030040050060070012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMwatt/m2AverageRadiationGlobal
Direct
DiffusePage23of30Thestandarddeviationishigherinthemorningascomparedtotheafternoon,indicatingthatthereisalargerdaytodayvariationofcloudcoverinthemorningascomparedtotheafternoon.Inotherwords,
in the afternoon, the sky is consistently heavy with cloud where
else, in the morning; thecloudcovermaysometimesbelow.2.13.1 DESIGN
POTENTIAL High Oktas numbers indicate heavy cloud cover in
Malaysias climate. It also means that duringdaytime, Malaysian sky
is normally bright because the sky will be illuminated by the
clouds
asopposedtoclearblueskies.Heavycloudscoveralsohindersradiationheattransferbetweenobjectsonthegroundwiththesky.In
general the lower the Oktas number, the better it is for the sky to
cool objects on the groundsurface.2.13.2 DESIGN RISK Oktas
measurement is done manually by meteorologists. They would take a
look at the sky
anddecidehowmanyeightoftheskyiscoveredbyclouds.2.13.3 CHARTS AND
TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev. 1:00:00
AM6.84.08.0 0.52:00:00 AM6.83.08.0 0.63:00:00 AM6.84.08.0
0.64:00:00 AM6.84.08.0 0.65:00:00 AM6.84.08.0 0.66:00:00
AM6.90.08.0
0.601234567812:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMOktasCloudCoverAverage
Minimum MaximumPage24of307:00:00 AM6.90.08.0 0.68:00:00 AM6.84.08.0
0.69:00:00 AM6.74.08.0 0.710:00:00 AM6.74.08.0 0.711:00:00
AM6.84.08.0 0.612:00:00 PM6.84.08.0 0.51:00:00 PM6.94.08.0
0.42:00:00 PM6.94.08.0 0.43:00:00 PM6.95.08.0 0.44:00:00
PM6.95.08.0 0.45:00:00 PM6.95.08.0 0.56:00:00 PM7.05.08.0
0.47:00:00 PM7.05.08.0 0.48:00:00 PM6.95.08.0 0.59:00:00
PM6.94.08.0 0.510:00:00 PM6.84.08.0 0.611:00:00 PM6.84.08.0
0.612:00:00 AM6.94.08.0 0.52.14 Effective Sky Temperature
Itisusefultoprovidetheeffectiveskytemperatureinthischapterbecauseitprovidesanindicationof
the possibility of using the sky to cool building passively. The
effectiveness of radiation heatexchange between objects on the
ground surface with the sky is defined by the effective
skytemperature.TheeffectiveskytemperatureisnotprovidedbytheTRYbutisestimatedfromthedrybulb
temperature, dew point temperature and cloud cover using equations
provided by Clark andBlanplied5.The estimated average effective sky
temperature in TRY is 18C. It is higher during daytime and islower
during night time. The average lowest effective sky temperature is
14.6C at 7am in themorning.Whiletheabsolutelowesteffectivesky
temperaturewasestimated
tobe9.5Cat8aminthemorning.Althoughthedaytimeaverageeffectiveskytemperatureisinthelow20sC,thedirectanddiffusesolarradiationduringdaytimeisprovidingmuchmoreheatthantheskyisremoving.On
average, the effective sky temperature is below 20C from the hours
of 6pm to 11am.
Theaveragelowesteffectiveskytemperatureisapproximately15Cat6aminthemorning.2.14.1
DESIGN POTENTIAL
Thelowertheeffectiveskytemperatureis,thebetteritisfortheskytoabsorbheat(cooling)fromobjects
on the ground. Therefore, as long as a surface is shielded from
direct radiation or does
notabsorbsolarradiation(asinproductswithveryhighsolarreflectivity)orduringnighttime(nosolarradiation),theskycanbeusedasameanofheatrejectionorcoolingsource.Roof
system that can block heat gain during day time and rejects heat
during night time willpotentially be effective means of cooling a
building. Buildings that are primary used during nighttime such as
residential homes will benefit significantly from such roof design.
Movable roof5Gene Clark and M. Blanpied, 1979. The Effect of IR
Transparent Windscreens on Net Nocturnal Cooling from Horizontal
Surfaces, Proceedings of the 4th National Passive Solar Conference,
Kansas City, MO.
Page25of30insulation,coolroofpaintsthatrejectssolarradiationduringdaytimewhilehavinghighemissivitytorejectheatandetc.maybeinterestingsolutionsforresidentialhomes.2.14.2
DESIGN RISK
Anaverageeffectiveskytemperatureabove20Cduringdaytimeisnotconsideredtobeefficienttocoolobjectsontheground.Therefore,usingtheskytocoolobjectsonthegroundwillonlybeusefulduringnighttimewhentheeffectiveskytemperatureisreducedbelow20C.Incountrieswherethecloud
cover is low and ambient air temperature is moderate, it is
possible for the sky to
provideconsistenteffectiveskytemperaturebelow10C(insomeplaces,evenbelow0C,makingitpossibleto
make ice with the night sky6). The high effective sky temperature
found in this climate is
largelyduetothehighmoisturecontentintheairandtheheavycloudcover.2.14.3
CHARTS AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev.
1:00:00 AM16.2012.720.1 1.32:00:00 AM15.8912.719.5 1.33:00:00
AM15.5511.719.2 1.34:00:00 AM15.2411.518.8 1.35:00:00
AM14.9810.918.5 1.46:00:00 AM14.7410.418.1 1.47:00:00
AM14.569.617.9 1.48:00:00 AM14.759.518.4 1.49:00:00 AM16.4311.620.3
1.510:00:00 AM18.5112.922.3 1.76 "Lesson 1: History Of
Refrigeration, Version 1 ME". Indian Institute of Technology
Kharagpur. Archived from the original on 2011-11-06.
5101520253012:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMmeter/secondEffectiveSkyTemperatureAverage
Minimum MaximumPage26of3011:00:00 AM19.9714.623.9 1.712:00:00
PM20.9315.124.4 1.71:00:00 PM21.6615.025.4 1.82:00:00
PM22.1012.726.0 1.93:00:00 PM22.1715.026.6 2.14:00:00
PM21.7213.926.7 2.45:00:00 PM20.9413.626.7 2.56:00:00
PM20.1213.925.1 2.47:00:00 PM19.3313.224.1 2.18:00:00
PM18.4214.222.2 1.89:00:00 PM17.7813.722.0 1.710:00:00
PM17.3113.321.4 1.511:00:00 PM16.8913.421.3 1.412:00:00
AM16.5313.220.7 1.32.15 Ground Temperature
ThegroundtemperaturewascomputedfromtheTRYusingKasudasequation7at1meterdepth.Itwas
computed that the soil temperature is constant at 26.9C for the
entire year. Furtherinvestigation using Kasudas equation showed
that at any depths greater 0.5 meter, the
groundtemperaturewillbeconstantat26.9C.It is also important to note
that groundwater temperature will also be at the same temperature
astheground(soil)temperature.2.15.1 DESIGN POTENTIAL There exist
designs that channel air intake into building through an
underground chamber to
precooltheairbeforeenteringthebuilding.However,thisstrategywillworkwellinthisclimateduringdaytime
when the outdoor air temperature is higher than the soil
temperature. However,
duringnighttime,theoutdoorairtemperatureislowerthanthesoiltemperature;channelingnightairintotheundergroundchamberwillheatuptheairinsteadofcoolingitdown.Inshort,thisstrategywillworkwellwithofficetypeofbuildingwherethebuildingisoccupiedduringdaytime;however,itwillnotworkwellforresidentialhomesbecausethehomesarenormallyoccupiedduringnighttime.TheTRYhasanaveragewetbulbtemperatureof24.3Candtypicaldesignofcoolingtowercallsforan
approach temperature of 5.5C higher than the wet bulb temperature,
providing an average of29.8C return water temperature to the
chiller. The groundwater temperature is estimated to
be26.9C;thereforeitisapproximately3Ccolderthanthewaterfromthecoolingtower.Colderwaterfor
the condensing side of the chiller will improve the efficiency of
chiller significantly. Water fromdeep lakes would also be good
potential for such opportunity to improve efficiency of the
chillerbecausethetemperatureofwaterindeeplakeswillalsofollowsthegroundtemperature.2.15.2
DESIGN RISK
TheKasudasequationdoesnotaccountforrainfallonthesoil,aswaterfromthesoilwillevaporateat
the wet bulb temperature, the surface of the soil may be cooler on
average for climate such asMalaysia where it rains fairly often and
consistently throughout the year. The effect of rainfall is7Kasuda,
T., and Archenbach, P.R. 1965. Earth Temperature and Thermal
Diffusivity at Selected Stations in the United States, ASHRAE
Transactions, Vol. 71, Part 1.Page27of30expected to be minimal on
the ground temperature. However, actual measurement of
onsitegroundtemperatureishighlyrecommended.Inaddition,furtherstudiesarerecommendedtoensurethatthecolderdaytimeairachievedviaanunderground
chamber can be achieved without increasing the moisture content of
the air.
Anincreaseinmoisturecontentwillincreaseenergyconsumptionoftheairconditioningsystem.Excessive
groundwater harvesting without adequate recharge will cause soil
properties todeteriorate and may cause ground to sink. Moreover,
pumping water over long distances will alsoincrease the water
temperature due to frictional losses and conduction gain through
the
pipes,whichmaycausethepredicted3Ccolderwatertemperaturenottobeachieved.2.16
Wind Speed
TheaveragewindspeedintheTRYshowedthatwindspeedislow(lessthan0.5m/s)fromthehoursof8pmto8am.Thewindspeedstartstoincreaseat8amandhasanaveragepeakof3.5m/sat3pmin
the afternoon. The hourly maximum wind speed showed that it is
possible to have high windspeed any time of the day, with the
lowest chance of high wind speed is 8 am in the morning.
Thedataalsoshowedthatitisalsopossibletozerowindspeedatanytimeoftheday.2.16.1
DESIGN POTENTIAL It is important to note that the peak average wind
speed occurs at the same time of high dry
bulbtemperature.Inaddition,whenthedrybulbtemperatureislow,theaveragewindspeedisalsolow.This
indicates that building designed with crossventilation at all hours
will on average bring morehot air than cool air into the building.
As the wind speed data showed that high wind speed canoccur at any
time, it is also possible for cross ventilation to bring cool air
to benefit the
buildingoccupants,therefore,crossventilationdesignneedtoconsiderthehoursoccupantmakeuseofthespaceandalsothepossibilitytodiverthotwindawayfromoccupantsduringcertainhours/conditionofthedayanddivertcoolairtowardsoccupantduringcertainhours/conditionoftheday.Operablewindow,
where the building occupant has control over when cross ventilation
is used is highlyrecommended.2.16.2 DESIGN RISK Wind speed and wind
direction data should be further checked against other year data to
ensurethat the data in TRY is reflective of the actual situation.
The selected months of TRY data waspredominantly selected based on
the dry bulb temperature, global horizontal solar radiation
andhumidity ratio. Therefore, it is recommended for academicians
and researchers to investigate
thewinddatafurthertoconfirmthebehaviorofwindspeedandwinddirectionaccordingtothehourofdayanddayoftheyear.Page28of302.16.3
CHARTS AND TABLE OF RAW DATA HoursAverageMinimumMaximumStd Dev.
1:00:00 AM0.440.06.40.9 2:00:00 AM0.460.05.40.9 3:00:00
AM0.450.07.00.9 4:00:00 AM0.480.06.01.0 5:00:00 AM0.480.07.01.0
6:00:00 AM0.470.07.60.9 7:00:00 AM0.540.05.30.9 8:00:00
AM0.850.04.11.0 9:00:00 AM1.440.05.01.2 10:00:00 AM2.150.06.51.4
11:00:00 AM2.460.06.91.4 12:00:00 PM2.770.37.01.4 1:00:00
PM3.050.06.61.4 2:00:00 PM3.360.07.11.5 3:00:00 PM3.500.07.01.5
4:00:00 PM3.300.07.01.5 5:00:00 PM2.580.05.81.5 6:00:00
PM1.690.07.01.3 7:00:00 PM0.940.05.41.0 8:00:00 PM0.560.05.30.8
9:00:00 PM0.470.05.60.8 10:00:00 PM0.430.04.70.8 11:00:00
PM0.380.07.20.8 12:00:00 AM0.460.05.20.9
012345678912:00:00AM3:00:00AM6:00:00AM9:00:00AM12:00:00PM3:00:00PM6:00:00PM9:00:00PM12:00:00AMmeter/secondWindSpeedAverage
Minimum MaximumPage29of302.17 Wind Direction & Hours of Air
Temperature below 29C Base on Ashrae 55, thermal adaptive comfort
model for natural ventilation, an
operativetemperatureof29CinMalaysiasclimatewillprovide80%populationsatisfactionrate8.Harvestingnatural
ventilation with air temperature above 29C will only heat up the
environment
providinguncomfortablesettingtothebuildingoccupants;therefore,naturalventilationshouldaimtoharvestthecoldwindthatisbelow29C.Thissectionprovidesinformationonwhichdirectionwindbelow29CisnormallycomingfromandwhatistherighthourinadaytoharvestcoldwindinMalaysia.Detailed
analysis of the TRY of its wind direction and dry bulb air
temperature yields that
asignificant37.5%ofthehoursinthewholeyear,thedrybulb(wind)temperatureisbelow29C.Theoccurrenceofcoldwindislargelyduringthehoursoflateeveningtomidmorning.Chartsprovidedin
this section showed that colder wind comes from the North (946
hours, 29%), NorthWest
(593hours,18%),East(430hours,13%),South(326hours,10%),SouthEast(297hours,9%),SouthWest(249hours,8%),NorthEast(248hours,8%)andlastlyWest(196hours,6%).Inshort,colderwindisprimary
from north and northwest (combined to provide 47% of total cold
wind available), thenfollowedbyeastandsouth.Cold wind from the
north and northwest normally occurs during late afternoon (~5pm)
until
latemorning(~9am).Whilecoldwindfromtheeastmainlyoccursinthemorninghoursof8amto9am.Coldwindfromthesouthislowbutisconsistentthroughouttheday.2.17.1
DESIGN POTENTIAL Capturing wind from the north and northwest should
be the primary objective to use naturalventilation to cool the
environment. Cool wind is primary available from the hours of 5pm
to 9am.When the air temperature is high during noon time, it will
not be comfortable to harvest naturalventilation. Ideally the
building occupants should have control over the natural ventilation
byproviding ability to the building occupants to close windows or
doors, to divert wind away fromoccupied space when the wind is hot
and to allow wind towards occupied space when the wind iscold.
Motorized louvers with temperature sensors may also be used to
provide this diversion
ofnaturalventilationwithoutrequiringmanualintervention.2.17.2
DESIGN RISK Wind speed and wind direction data should be further
checked against other year data to ensurethat the data in TRY is a
true reflection of the actual situation. The selected months of TRY
werepredominantly selected based on the dry bulb temperature,
global horizontal solar radiation andhumidity ratio. Therefore, it
is recommended for academicians and researchers to investigate
thewinddatafurthertoconfirmthebehaviorofwindspeedandwinddirectionaccordingtothehourofdayanddayoftheyear.8
Ashrae 55 Page30of302.17.3 WIND CHARTS OF AIR TEMPERATURE BELOW 29C
_______________________________EndofChapter2____________________________________020040060080010001200NorthNorthEastEastSouthEastSouthSouthWestWestNorthWestHoursofWindDirectioninTRYAllTemperature
