Thermally Activated BuildingSystems (TABS)
Lecture "Building Control and Automation", part "Building Automation"
Author: Dr. Conrad GählerRevision: 1.0, 18-Mai-2015
Rev 1.0, 18-Mai-2015Page 3 / 18 Dr. Conrad Gähler
BuildingAutomation
Thermally Activated Building Systems (TABS)D: Thermoaktive Bauteilsysteme (TABS)
Principle• TABS are large-area systems for heat and cool transfer• They may be integrated in the building structure or attached to it
(D: aufgesetzt)• The systems use the concrete core of the buildings, usually the floor slabs,
for climatisation• Room heating and cooling is achieved either by means of TABS alone, or
with additional systems (e.g. radiators)
Rev 1.0, 18-Mai-2015Page 4 / 18 Dr. Conrad Gähler
BuildingAutomation
Thermally Activated Building Systems (TABS)Advantages
Exploiting natural energy resources• Small temperature differences between flow and room temperaturesà energy efficient solutions are possible(heating with high COP; free cooling)
“Self-control effect”• Small temperature differences (TFlow-TR) offer comparatively moderate
potential for overheating
Using the big thermal storage of TABS• The big thermal storage capacity of TABS makes it possible to separate in
time heat/cold demand and heat/cold preparation.• ð energy-efficient solutions, e.g.
• free cooling at night• intermittent operation of the heating circuit pumps• accommodating solar thermal energy• heating with heat pump when electricity is cheap
Rev 1.0, 18-Mai-2015Page 5 / 18 Dr. Conrad Gähler
BuildingAutomation
Thermally Activated Building Systems (TABS)Restrictions
Restricted freedom for constructions of floors and ceilings (D: Decken-und Bodenaufbauten)
• Close thermal coupling between TABS and room air is requiredà Conflicts with hollow floors, abgehängten Decken, acoustic isolation, …
No arbitrary requirements to thermal comfort• A rise of TR during the day must be accepted
Demanding HVAC planning process• Knowledge of building usage required• Acceptance of the 2 above-mentioned points must be secured• Integrated Planning of the HVAC system and its control (dynamic sizing)
Conventional control strategies are not sufficient• Conventional control strategies, in particular for TR control, do not work
satisfactorily• TABS has a very high thermal inertia• Tricky changeover between heating and cooling operation
Rev 1.0, 18-Mai-2015Page 6 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI / KTI research project “TABS Control”
Project duration• 2004 – 2008
Partners
• Energiesysteme/Haustechnik
• ZIG Zentrum für Integrierte Gebäudetechnik
• Building Technologies
Rev 1.0, 18-Mai-2015Page 7 / 18 Dr. Conrad Gähler
BuildingAutomation
TABS plant with control:Structure
§ Separation in consumer, distribution andproduction of heat and cold
§ Separation of consumer (rooms) in zones(typically 2-3 zones per building)
§ Separation of the control task in zonecontrol, control of heat/cold distributionand control of heat/cold production
Rev 1.0, 18-Mai-2015Page 8 / 18 Dr. Conrad Gähler
BuildingAutomation
TABS plant with control:Zone control
A simple way of zone control:Outside air temperature compensatedflow temperature control
Cooling curve
Heating curve
Hea
ting
limit
Coo
ling
limit
Heating orOff
Heating or CoolingOr Off
Coolingor Off
Outside temp.
Zone flow temp.setpoint
TFlow is confined to liebetween heating andcooling curves:• TRet<HCrvà Heating• TRet>CCrvà Cooling• Else neither; but pump may
be on for balancing heatbetween different rooms /zones
Rev 1.0, 18-Mai-2015Page 9 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, project results:Unknown-but-bounded (UBB) approach forparameterization of heating / cooling curve
Principle• TABS / TABS control cannot compensate for variations in internal heat load at short
notice• Heat loads cannot be predicted exactly, but upper and lower bounds for their (daily)
average can be assumed• Based on this, parameterize
• the heating curve such that TR does not go below TRSpH (e.g.21°C) in case wherethe internal het gains are at the lower bound
• the cooling curve such that TR does not exceed TRSpC (e.g.25°C) in case wherethe internal heat gains are at the upper bound
• Only feasible if tolerance band is sufficiently wide and uncertainty of loads is sufficientlysmall!
Rev 1.0, 18-Mai-2015Page 10 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, project results:Unknown-but-bounded (UBB) approach forparameterization of heating / cooling curve
Principle1. For the lower bound of the heat gain progression it is
computed by means of simulation what is the minimal liftto TR that it causes in the course of a day when cyclicallyapplied (every day for a long time).
2. Then from the lowest TR lift an “equivalent lower heat gainbound” is computed that would cause the same minimalTR lift for the whole day
3. The heating curve is parameterized such that TR nevergoes below TRSpH assuming that the heat gainsconstantly equal the “equivalent lower heat gain bound”
4. For the upper bound of the heat gain progression themaximal TR lift is computed
5. From the highest lift, the “equivalent upper heat gainbound” is computed
6. The cooling curve is parameterized such that TR neverexceeds TRSpC with “equivalent upper heat gain bound”
Especially for office buildings, this procedure must be carriedout for a weekly (instead of daily) period, including weekends.
0
5
10
15
20
25
30
35
0 6 12 18 24
hour of day [h]
heat
gain
boun
ds[W
/m2 ]
lower bound
upper bound
0
1
2
3
4
5
0 6 12 18 24
hour of day [h]
Room
tempe
ratu
reinc
rease
[K]
lower bound
upper bound
2.6
K
2 14 5
Heat
gain
boun
ds[W
/m2 ]
Roo
mte
mpe
ratu
rein
crea
se[K
]
Hour of day [h]
Hour of day [h]
Rev 1.0, 18-Mai-2015Page 11 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, project results:The modular TABS-Control zone control
… extension of the TO-compensated flow temp. control
oaJSpH,rJ
SpC,rJ
rJFB,SpH,rJ
FB,SpC,rJSpH,swJ
SpC,swJPWM,SpH,swJ
PWM,SpC,swJoaJ
Sp,swJ
swJ
sw,MaxJ
sw,MinJ swJ
12 3 4
• Basic modules: 1 “Heating/ cooling curve” and4 “Sequence Control”
• Optional for improving comfort: Module 2 “TRcontrol” (TR control on day-to-day basis)
• Optional for improving energy efficiency:Module 3 “Intermittent operation”à Research question: How well does coolingwith 24h cycling work? (à Profit from low TO atnight and use of free cooling when possible!)
Rev 1.0, 18-Mai-2015Page 12 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, module for intermittentoperation: 1. Modelling
swJf,lR
cJ
rJ
oaJ
tR
auxg qq && +0,1sR
1,1sR
2,1sR
1n,1sR
1,2sR
2,2sR
2n,2sR
0,2sR
0,iwR
1,iWR
2,iWR
niW,iWR
rJ
rC
1,1sC
2,1sC
1n,1sC
1,2sC
2,2sC
2n,2sC
1,iWC
2,iWC
niW,iWC
0,1uR
1,1uR
2,1uR
1n,1uR
1,2uR
2,2uR
2n,2uR
0,2uR
1,1uC
2,1uC
1n,1uC
1,2uC
2,2uC
2n,2uC
Finite Element MethodHigh order modelFirst order model
R~swJ
f,lRtR
rJoaJ
cJ
auxg qq && +
sC
Sim
plifi
catio
nValidation
Laboratory / reality
Sim
plifi
catio
n
Simplification
Rev 1.0, 18-Mai-2015Page 13 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, module for intermittent operation:2. Design / simulation using Closed- Loop Model inSimulink
High order model
Control incl.pulse width modulation
based on first order model
Weather data(measurements),
internal heat gains
Rev 1.0, 18-Mai-2015Page 14 / 18 Dr. Conrad Gähler
BuildingAutomation
Implementation / definition HMI
CTI project “TABS-Control”, module for intermittent operation:3. Implementation of control functionality
Parameter Value(example)
Period of heatingPWM operation
4 h
Period of coolingPWM operation
24 h
Period of unknownPWM operation
4 h
Maximum correctionof flow temperaturesetpoint
1.5 K
Minimal purgeoperation time
20 min
Minimal pumpswitch-on time
1 min
Minimal pumpswitch-off time
1 min
PWM thermalresistance ratio
40 %
Rev 1.0, 18-Mai-2015Page 15 / 18 Dr. Conrad Gähler
BuildingAutomation
Lab tests in TABS test room, Siemens HVAC Laboratory
CTI project “TABS-Control”, module for intermittent operation:4. Lab tests: HVAC Lab
Test room from outside
Test room from inside
Heat loads = simulated persons
Rev 1.0, 18-Mai-2015Page 16 / 18 Dr. Conrad Gähler
BuildingAutomation
CTI project “TABS-Control”, module for intermittent operation:Lab test: Cooling in 24 hours PWM operation
Room temperature androom temperature setpoint range
Temperature in weather zone
Purge operation (= pump onbut no heat removal from water circuit)
Flow temp., return temp.and flow temp. setpoint rangePump command
Heat gains
Weekend withreduced thermal load
End time of night cooling is computed usinga model such that TR remains withintolerance band on the next day
Rev 1.0, 18-Mai-2015Page 17 / 18 Dr. Conrad Gähler
BuildingAutomation
Download from: www.faktor.ch/?page=tabs
HauptresultateKombination Raumtyp: 1
Wärmegewinnschrankenprofil: 1
RaumtemperatursollwerteOberer Raumtemperatursollwert J r,SpC 24.5 °C ZusatzsystemUnterer Raumtemperatursollwert J r,SpH 21 °C TypAuslegungstemperaturen Min. Breite VorlauftemperatursollwertbandAuslegungaussentemperatur Kühlfall J oa,DsC 30 °C für TABS (falls Zusatzsystem) 0.5 KAuslegungaussentemperatur Heizfall J oa,DsH -10 °C
Zulässige Abweichungen vom Komfortbereich Mo Di Mi Do Fr Sa So WocheZulässige Überschreitungen bei oberer Wärmegewinnschranke 0 0 0 0 0 0 0 Kh 0 KhZulässige Unterschreitungen bei unterer Wärmegewinnschranke 0 0 0 0 0 0 0 Kh 0 Kh
Äquivalente WärmegewinnschrankeschrankenObere äquivalente Wärmegewinnschranke q g,eub 18.4 18.4 18.4 18.4 18.4 8.6 8.6 W/m2 18.3 W/m2
Untere äquivalente Wärmegewinnschranke q g,elb 4.3 4.3 4.3 4.3 4.3 1.1 1.1 W/m2 1.8 W/m2
Kühlkurve TABSKühlgrenze: Vorlauftemperatursollwert J sw,SpLmC 23.1 23.1 23.1 23.1 23.1 23.9 23.9 °C 22.7 °CKühlgrenze: Aussentemperatur J oa,LmC -5.8 -5.8 -5.8 -5.8 -5.8 9.8 9.8 °C -2.1 °CAuslegung Kühlen: Vorlauftemperatursollwert J sw,SpC,Ds 19.2 19.2 19.2 19.2 19.2 21.7 21.7 °C 19.2 °CAuslegung Kühlen: Rücklauftemperatur J rw,C,Ds 20.4 20.4 20.4 20.4 20.4 22.4 22.4 °C 20.5 °CHeizkurve TABSHeizgrenze: Vorlauftemperatursollwert J sw,SpLmH 21.7 21.7 21.7 21.7 21.7 21.0 21.0 °C 21.8 °CHeizgrenze: Aussentemperatur J oa,LmH 4.8 4.8 4.8 4.8 4.8 18.2 18.2 °C 9.1 °CAuslegung Heizen: Vorlauftemperatursollwert J sw,SpH,Ds 23.3 23.3 23.3 23.3 23.3 24.1 24.1 °C 23.9 °CAuslegung Heizen: Rücklauftemperatur J rw,H,Ds 22.7 22.7 22.7 22.7 22.7 23.2 23.2 °C 23.1 °C
Breite Vorlauftemperatursollwertband TABSVorlauftemperaturdifferenz Kühlkurve-Heizkurve DJ sw,Sp 0.3 0.3 0.3 0.3 0.3 2.0 2.0 K -0.3 KMin. Breite Raumtemperatursollwertband (ohne Zusatzsystem)Minimale Raumtemperatursollwertbreite (DJ sw,Sp =0 ) DJ r,SpMin 3.3 3.3 3.3 3.3 3.3 1.7 1.7 K 3.8 KWärmegewinnschrankeunsicherheitMax. zulässige Wärmegewinnspanne (ohne Zusatzsystem) D q g,Max 15.2 15.2 15.2 15.2 15.2 15.2 15.2 W/m2 15.2 W/m2
Effektive äquivalente Wärmegewinnspanne D q g,eq 14.1 14.1 14.1 14.1 14.1 7.5 7.5 W/m2 16.5 W/m2
Relative Wärmegewinnspanne r q 0.9 0.9 0.9 0.9 0.9 0.5 0.5 - 1.1 -Kann Komfort auch ohne Zusatzsystem eingehalten werden? ü ü ü ü ü ü ü û
Rücklauftemperaturdifferenz für obere Wärmegewinnschranke DJ rw,ub 0.28 0.28 0.28 0.28 0.28 0.11 0.11 K 0.5 K
Leistungsbedarf TABSMax. Kühlleistungsbedarf (Auslegungaussentemperatur) q w,DsC,ub -17.1 -17.1 -17.1 -17.1 -17.1 -9.4 -9.4 W/m2 -17.0 W/m2
Max. Heizleistungsbedarf (Auslegungaussentemperatur) q w,DsH,lb 7.5 7.5 7.5 7.5 7.5 12.0 12.0 W/m2 11.1 W/m2
Leistungsbedarf ZusatzsystemMax. Kühlleistungsbedarf (Auslegungaussentemperatur) q aux,DsC,ub 0.0 0.0 0.0 0.0 0.0 0.0 0.0 W/m2 0.0 W/m2
Max. Heizleistungsbedarf (Auslegungaussentemperatur) q aux,DsH,lb 0.0 0.0 0.0 0.0 0.0 0.0 0.0 W/m2 0.0 W/m2
Parameter Gebäudeautomationssystem DesigoSiemens Building TechnologiesHeizsollwert nominale Raumtemperatur SpHTRNom 21 °C 21 °CKühlsollwert nominale Raumtemperatur SpCTRNom 24.5 °C 24.5 °CAussentemperatur für nominale Heizgrenze TOaHLmNom 4.8 °C 9.1 °CAussentemperatur für nominale Kühlgrenze TOaCLmNom -5.8 °C -2.1 °CAuslegungsaussentemperatur Heizen TOaDsgnH -10 °C -10 °CHeizsollwert Vorlauftemp. für die Auslegungsaussentemperatur SpHTFlDs 23.3 °C 23.9 °CAussentemperatur oben für Heizen TOaHiH 4.8 °C 9.1 °CHeizsollwert Vorlauftemp. für obere Aussentemperatur SpTFlHi 21.7 °C 21.8 °CDelta Sollwert nominale Vorlauftemperatur DSpTFlNom 0.27 K -0.34 KDelta Heizsollwert Vorlauftemperatur DSpHTFl 0.0 0.0 0.0 0.0 0.8 0.8 KDelta Kühlsollwert Vorlauftemperatur DSpCTFl 0.0 0.0 0.0 0.0 2.5 2.5 K
Taktbetriebsparameter RthRatio 38.0%
Kein Zusatzsystem
ganze WocheAuswertung für Einzeltage
Heiz/Kühlkurve für ganze Woche
18
19
20
21
22
23
24
25
26
27
28
-15 -10 -5 0 5 10 15 20 25 30 35
Aussentemperatur [°C]
Vor
lauf
tem
pera
turs
ollw
ert[
°C]
Heizkurve
Kühlkurve
Heizgrenze
Kühlgrenze
Berechnung starten(alte Werte werden überschrieben)
Berechnete Werte löschen
Heiz/Kühlkurve für Montag / Sonntag
18
19
20
21
22
23
24
25
26
27
28
-15 -10 -5 0 5 10 15 20 25 30 35
Aussentemperatur [°C]
Vorl
aufte
mpe
ratu
rsol
lwer
t[°C
]
Heizkurve MontagKühlkurve MontagHeizgrenze MontagKühlgrenze MontagHeizkurve SonntagKühlkurve SonntagHeizgrenze SonntagKühlgrenze Sonntag
CTI project “TABS-Control”, project results:Planning tool TABSDesign
Rev 1.0, 18-Mai-2015Page 18 / 18 Dr. Conrad Gähler
BuildingAutomation
Handbuch TABS Control - Steuerungund Regelung von TABS (publishedMarch 2009)
Available from Faktor-Verlag:www.faktor.ch
Further publications (selection)
• “Control of Thermally Activated Building Systems”,CLIMA 2007 Helsinki
• “Integrated Design of Thermally Activated BuildingSystemsAnd of Their Control",CLIMA 2007 Helsinki
• “Effect of the Hydraulic Piping Topology on EnergyDemand and Comfort in Buildings with TABS”,CLIMA 2007 Helsinki
• “Control of Thermally Activated Building Systems”,Applied Energy 2008
• “Control of Thermally Activated Building Systems inintermittent operation with pulse width modulation”,Applied Energy 2009
CTI project “TABS-Control”, project results:Handbook “TABS Control”
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