PERFORMANCE OF SOLAR ENERGY DRIVEN FLOOR HEATING SYSTEM GÜNEŞ ENERJİSİ İLE DÖŞEMEDEN ISITMA SİSTEMİNİN PERFORMANS ANALİZİ

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1 Isı Bilimi ve Tekniği Dergisi, 29, 1, 37-44, 2009 J. of Therml Science nd Technology 2009 TIBTD Printed in Turkey ISSN PERFORNCE OF SOLR ENERGY DRIVEN FLOOR HETING SYSTE Cüneyt KURTY *, İbrhim TILGN** nd Ö. Ercn TER *** * Gzi Üniversitesi, ühendislik imrlık Fkültesi imrlık Bölümü ltepe, nkr, kurty@gzi.edu.tr ** Gzi Üniversitesi, ühendislik imrlık Fkültesi kine ühendisliği Bölümü ltepe, nkr, tilgn@gzi.edu.tr *** Gzi Üniversitesi, ühendislik imrlık Fkültesi kine ühendisliği Bölümü ltepe, nkr, oter@gzi.edu.tr (Geliş Trihi: , Kbul Trihi: ) bstrct: Using solr energy n office is heted from the floor nd therml comfort nlysis is performed for nkr conditions. Solr energy is collected by flt-plte collectors in storge tnk. The therml comfort nlysis of the office is performed using Fnger s method. In this method the therml comfort is ffected by environmentl nd individul prmeters; ir velocity, humidity, temperture, rdition temperture, ctivity nd oth resistnce. esurements re tken t 0.2 m, 0.6 m, nd 1.0 m heights beside floor temperture. The experimentl results nd the individul dt re used to clculte the Predicted en Vote (PV) nd Predicted Percentge of Disstisfied (PPD). computer progrm is written in FORTRN to clculte these prmeters using the experimentl, individul dt nd the results re presented s PV digrms. The results indicte tht the therml comfort cn be provided with such heting system. The PV vlues rnge between to Keywords: Solr heting, therml comfort, floor heting GÜNEŞ ENERJİSİ İLE DÖŞEEDEN ISIT SİSTEİNİN PERFORNS NLİZİ Özet: Bu çlışm, güneş enerjisinden yrrlnrk nkr şrtlrınd döşemeden ısıtm sisteminin projelendirilmesi ve ısıl konfor şrtlrının incelenmesini içermektedir. Güneş enerjisi, düzlem plklı kolektörler kullnılrk elde edilmiş ve depolnmıştır. Çlışmd Fnger yöntemi kullnılrk sistemin ısıl konfor şrtlrı deneysel olrk incelenmiştir. Bu yöntemde ısıl konfor şrtlrını etkiyen değişkenler çevresel ve kişisel değişkenler olmk üzere iki n grupt toplnır. ktivite ve giysi değerleri kişisel değişkenler; hv hızı, nem, sıcklık ve ışım sıcklığı çevresel değişkenlerdir. nlizde döşeme sıcklığı, döşemeden 0,2 m, 0,6 m ve 1,0 m yükseklikte çevresel değişkenler ölçülmüştür. Deneysel veriler kullnılrk FORTRN dilinde yzıln bilgisyr progrmı yrdımı ile Önceden belirlenen ortlm oylm (PV) ve önceden belirlenen hoşnutsuzluk ornı (PPD) değerleri hesplnmış ve grfik olrk sunulmuştur. PV değerleri ile rsınd değişmektedir. Sonuçlr deneydeki gibi yöntemle ile ısıl konforun sğlnbileceğini göstermiştir. nhtr Kelimeler: Güneş enerji ile ısıtm, ısıl konfor, döşemeden ısıtm Nomenture DU -Bois surfce re(m 2 ) f the rtio of the surfce re of the othed body to the surfce re of the nude body h c Het trnsfer coefficient (W/m 2 K) I Therml resistnce from skin to outer surfce of the othed body (o) etbolic rte (W) η echnicl efficiency P vpour pressure in mbient ir (mmhg) PV Predicted en Vote PPD Predicted Percentge of Disstisfied T ir temperture ( C) T in Collector inlet temperture ( C) en wter temperture ( C) T m T out T mrt T Collector exit temperture ( C) en rdition temperture ( C) en temperture of outer surfce of othed body ( C) v Reltive ir velocity (m/s) INTRODUCTION It is er tht the humn being should be in therml comfort to study efficiently in their office. In order to estblish fvourble indoor therml environment, humn therml comfort should be evluted. Recently rdint floor heting pplictions hve incresed significntly in Europe, nd new residentil buildings hve floor heting systems. The bsic components of the spce heting systems using floor heting system re 37

2 similr to those of domestic wter heting systems. The floor heting systems, driven by solr energy operte t lower tempertures (tht is less thn 32ºC), nd het trnsfer rte into the spce is by rdition nd convection. (thienitis nd Chen, 2000) Sttri nd Frhnieh, (2006) considered trnsient conduction, convection nd rdition het trnsfer mechnisms, nd nlyzed the therml performnce of rdint systems in buildings by using finite element method. Yeo nd others (2003) investigted the chnges nd recent energy sving potentil of residentil heting in Kore, nd shown tht modern prtment buildings with hot wter rdint floor heting yield less het loss due to the tighter envelope, but lso yield higher energy consumption. Becker nd Pciuk (1993) presented the methodology developed to investigte the vrious effects of different heting ptterns on the overll therml performnce of residences, tht does not receive solr gins. Bouchlghem (1999) developed computer progrm which simultes the therml performnce of the building tking into ccount design vribles relted to the buildings envelope, but lso pplies numericl optimiztion techniques to determine the optimum design vribles. rtinez, et. l. (2005) nlysed the performnce of residentil solr heting system in urci in Spin, nd use the recorded dt to estimte the performnce of the system. Bdrn nd Hmdn (2004) mke theoreticl nd experimentl study for floor heting system using solr collectors. lso they studied similr system using solr ponds under the sme locl conditions. the therml performnce nd comfort conditions produced by five different pssive solr heting strtegies in the United Sttes idwest. This study nlyses the therml comfort in office with floor heting system for nkr. solr heting system is designed nd constructed using flt-plte solr collectors. For winter conditions the therml comfort is performed using the method proposed by Fnger (1970). The floor heting re of the office is bout 23 m 2 nd the flt plte collectors re used nd mounted to the roof of the building with slope of 35. The PV vlues t 0.2 m, 0.6 m nd 1.0 m from the floor nd the men PPD vlues re clculted. The iso-pv curves re drwn for two different o-vlues. Results t different levels re compred nd evluted. EXPERIENTL STUDY The building is locted in nkr, nd the experiments were performed during the winter time of the yer The room is locted to corner of the second floor of the multi-store building. Its windows re looking to the south-est. The spce is intended s n office, nd dimensions of the office re 630 cm x370 cm nd 335 cm height. The wlls of the office re mde of brick nd both side of it re covered by plster. The het loss of the office is clculted s 3.10 kw nd the outer design temperture of nkr is tken s -12ºC. There were three people in the office nd they were sitting during the experiments. Ech experiment took bout 3 hours. This my cuse some devitions from the expected dt. ring the experiments the direct rdition t the dytime is chnged. This ffects the temperture nd therefore the PV vlues. Zhi, et. l., (2007) built solr system cpble of heting, cooling, nturl ventiltion nd hot wter supply in Shnghi. The system contins 140 m 2 solr collector rrys, two dsorption chillers, floor rdition heting pipes, finned tube het exchngers nd hot wter storge tnk of 2.5 m 3. It is used for heting in winter, cooling in summer, nturl ventiltion in spring nd utumn, hot wter supply in ll the yer for 460 m 2 building re. fter 1 yer opertion, it is confirmed tht the solr system contributes bout 65% of the totl energy of the involved spce for the wether conditions of Shnghi. Het is trnsferred from the pipes to the surfce of the floor nd it is trnsferred to the room by convection. tmc, et. l., (2007) investigte the locl differences between body segments cuses by rdint temperture nd nlyzed the interior surfce tempertures for different wll nd ceiling constructions with their effect on therml comfort. Dlmgkidis, et. l., (2007) studied the comfort in buildings with miniml energy consumption. Nicol nd Humprhreys (2007) studied the mximum tempertures in Europen office buildings to void therml discomfort. This work defines comfortble conditions nd the rnge of cceptble temperture. Fernndez nd Gonzlez, 2007 nlysed 38 The floor heting system using solr energy is designed, nd the working prmeters of the system re given in Tble 1. The digrm of the floor heting system is shown in Fig.1. The selective surfce of the collectors ws mde of copper nd pinted with mt blck. Tble 1. Properties of the solr heting system. Properties Zone (Ner the window) Zone B (Ner the door) Wter inlet temperture 50 o C 50 o C Wter exit temperture 40 o C 22 o C Comfort re 8 m 2 12 m 2 Het trnsfer rte 1376 W 624 W Volumetric flow rte 3.7 x 10-5 m 3 /s x 10-5 m 3 /s Floor temperture 35 o C 25 o C Pressure drop 139 mbr 6.5 mbr xil distnce between pipes 10 cm 20 cm Length of pipe 80 m 60 m

3 Figure 1 The schemtic digrm of the floor heting system The hot wter is collected in storge tnk of 0.20 m 3 cpcity nd insulted with the glss wool of 5 cm thickness. The storge tnk works s counter flow het exchnger. n electricl resistnce heter of 2 kw cpcity is used s het source for the conditions t which solr energy is not sufficient. The control pnel is used to compre the wter temperture of the storge tnk nd wter input temperture to keep it bove 5ºC. The hot wter is circulted in 140 m long plstic wter pipe under the floor. Its outer dimeter is bout 16 mm nd 2 mm thick. Plstic combs re used to keep the distnce between the pipes constnt s shown in Fig. 2. Polystren insultion mteril of 3 cm thick nd nylon lyer is used below the pipes. The pipes re covered by 3 cm thick concrete, nd lminte floor mteril is used s finishing lyer. Ner the windows the distnce between the pipes re nrrow s shown in Fig. 2.. This is becuse of the high het losses ner the windows. The occupied zone of the office is divided into 55x55 cm squres s shown in Fig. 2.b. nd totlly there re 50 squres on the floor. esurements re tken t the centre of ech squre for three heights bove the floor level. In order to obtin resonble dt in ll experiments mesurements re tken over the period of 4 min. The ir temperture, the men rdint temperture, the ir velocity nd the reltive humidity re mesured t ech mesuring points. The tnk inlet nd exit tempertures re mesured, nd the men wter temperture in the tnk is clculted by T m = (T in +T out ) /2. The vrition of outer ir temperture, the inlet nd outlet wter tempertures re shown in Fig.3. Fnger (1970) used Predicted en Vote (PV) for the therml comfort nd proposed the following eqution for the PV: () Figure 2. Instlltion of wter pipe nd finishing (b)

4 Figure 3. Environmentl ir temperture, nd solr collector inlet nd collector exit tempertures of the wter. PV = (0.352e [ ( / ) (1 η) (1 η) (34 T ) ) 8 (1 η) p f (44 p [( T ) + 273) ( Tmrt + 273) ] f hc ( T T )] (1) Where hc is the het trnsfer coefficient nd defined s h c = 2.05( T 2.05( T h c = ( T T ) T ) v T ) v v Eqution (2) is used when the ir velocity is less thn 0.1 m/s, nd Eqution (3) is used when the ir velocity is greter thn 0.1 m/s. etbolic rte, mechnicl efficiency nd reltive velocity of the still ir re tken from Fnger (1970) nd given in Tble 2. On the other hnd Predicted Percentge of Disstisfied (PPD) is defined s; ( PV PV 2 ) PPD = e (4) 4 (2) (3) dt for different othing ensembles in winter conditions re tken from Fnger (1970) nd given in Tble 3. Tble 2. etbolic rte of some office work (Fnger,1970) ctivity Reding by sitting etbolic rte (W/m 2 ) echnicl efficiency (η) Reltive Velocity in still ir m/s) ,05 Writing ,05 Computer using ,05 Tble 3. Dt for different othing ensembles to winter conditions for Office Work.(Fnger, 1970) Clothing ensemble I (o) Shirt, trousers, socks, shoes, single ply poplin jcket. For mn; Shirt, trousers, nd jcket. For womn; Shirt, skirt nd jcket Long sleeves cotton shirt, wool socks, shoes, jcket nd vest Clothing ensemble is one of the environmentl fctors which effect the therml comfort. There re two prmeters in the comfort eqution relted with the othing ensemble; these re I, therml resistnce of the othing nd f, the rtio of the surfce re of the othed body to the surfce re of the nude body. The 38 40

5 RESULTS Properties of floor heting system re given in Tble 1. The results of the experiments done on 9th of Februry, 2007 re presented. Vrition of environmentl temperture nd solr het flux with time during the experiments re given in Fig. 4. The drop on the solr het flux fter m. is due to oudy wether. The increse on the environmentl temperture lso stops until t p.m. Figure indictes tht the environmentl conditions were not constnt during the experiments. The verge solr het flux nd verge vlue of environmentl tempertures re lso shown in Fig. 4. The ir tempertures re mesured by thermocouples nd the men rdint temperture is mesured by the globe thermometer. The globe thermometer is constructed by plcing thermocouple to the centre of the sphere. The sphere is pinted by mtt blck pint with high bsorptivity nd then clibrted (Fnger, 1970). The ir velocities re mesured s less thn 0.1 m/s nd the nlogue dt is converted to the digitl dt nd stored in computer. computer progrm is written in FORTRN, nd using the mesured vlues the PV for ech mesuring point t three heights re clculted using Equtions (1) nd (2). For ech loction the PPD vlues re lso determined using Eqution (4) nd their men vlues re given in Tble 4. Tble 4. en PV nd en PPD vlues for different levels. Distnce from the floor en PV Thin I en PV Thick I en PPD Thin I en PPD Thick I 0.2 m m m The floor tempertures re mesured by stndrd type compct infrred thermometer. The iso-tempertures of the floor re mesured nd given in Fig.5. The iso PV vlues t 0.2 m, 0.6m nd 1.0 m re drwn nd given in Figs 6, 7 nd 8 re for thick othes respectively. The thin nd thick othing ensembles re given in Tble 3. CONCLUSIONS The PV-vlues re clculted by using the thin nd thick o-vlues, nd the ctivity level given in Tble 2 nd Tble 3 for the winter conditions respectively Fnger,1970. s shown in Fig.5 the surfce tempertures of the floor ner windows re higher thn the inner regions of the room. This is becuse of the lengths of the pipes re longer ner the windows. Experiments re performed during the noontime nd the comfort conditions re ffected by the direct solr rdition, though the windows. The mximum floor temperture mesured is bout 29.5 C nd it does not exceed the permissible floor temperture shown in Fig. 5. On the figures of iso-pv vlues the drk regions indicte the low PV vlues t which comfort conditions re not provided. ccording to Fnger s method when the PV vlues pproches to zero vlue, the therml comfort is provided. The comprison of Iso- PV lines for thin o-vlues t 0.20m., 0.60 m. nd 1.00m. with Figs. 6, 7 nd 8 indictes tht for the thick othes we hve slightly better comfort conditions thn the thin othes. This is becuse of the difference between the o-vlues nd the rtio of the surfce re of the othed body to the surfce re of the nude body shown in Tble 3. This discussion cn be extended to ll levels. When the othes re thick the comfort conditions re better thn the thin othes t 0.2 m, 0.6 m nd 1.00 m levels. On the other hnd the PV vlues re incresing t high levels, it mens better therml comfort conditions re provided t 1.0 m thn 0.2 m s seen in the Fig. 6 nd Fig. 8 for thick othes. The PV vlues clculted for the office re not homogeneous, nd it chnges between 1.00 to 1.33 for the thick ensemble given in Fig.6 t the level of 0.20 m. The corresponding men PPD vlue is for thick oth s shown in Tble 4. This vlue of PPD indictes tht the therml comfort is not provided t 0.20m. The uncertinty of the PV vlues is clculted s ± 0.04 percent. s indicted in figures given bove the therml field in the office is not uniform. Then, the PV of course will not be the sme over the occupied zone. s n exmple the clculted PV vlues for 0.60 m from the floor level for two different othing ensembles re given in Iso-PV lines for thin o-vlues t 0.60m nd Fig. 7. Comprison of these two figures shows tht the PV vlues of thick othing given in Fig. 10 re higher thn the thin othing. Similr results re obtined for other levels of mesurements given in Iso-PV lines for thin o-vlues t 1.00m nd Iso-PV lines for thick ovlues t 1.00m. (Fig.8) It is impossible to stisfy ll people in lrge group shring collective imte. Even with perfect environmentl system, which cretes bsolutely uniform conditions in the occupied zone, one cn not ttin Predicted Percentge of Disstisfied (PPD) vlue lower thn 5% for similr othed people nd in the sme ctivity. rtinez, et. l., (2005) hs shown tht 20% of the energy required ws provided from solr energy during the months of Jnury nd Februry. In our study bout

6 Figure 4 Vrition of environmentl temperture nd solr het flux during the experiments. 15% of the energy required for office room ws provided from solr energy in Februry Zhi, et. l., (2007) im tht 4470 J/m 2 solr energy for the hot wter supply for the 460 m 2 building re. In our study bout 0.96 kw energy is provided by solr energy for the office of m 2. Bdrn (2004) s shown tht solr collector system requires less opertion nd mintennce work. Our under floor heting system lso requires less opertion nd mintennce work. Sttri nd Frhnieh (2006) s shown tht the type nd thickness of the floor cover is importnt prmeters in the design of floor heting system. In our experimentl study we hve lso observed tht thickness of the floor cover is quite importnt. Consequently t nkr conditions it is not possible to provide therml comfort conditions with thick othing ensemble using solr energy or it is possible by Figure 5. The iso-tempertures of the floor Figure 6. Iso-PV lines for thick o-vlues t 0.20m.

7 Figure 7. Iso-PV lines for thick o-vlues t 0.60m. incresing supplementry het sources. This method of nlysis of the therml comfort is pplicble for different type of spce heting nd cooling systems. On the other hnd, if the occupied zone is divided into smller zones better results could be obtined. REFERENCES thienitis,.k, Chen,Y., The effect of solr rdition on dynmic therml performnce of floor heting system, Solr energy, 69(3), , tmc I, Kynklı O, Yigit., Effects of rdint temperture on therml comfort. Building nd Environment; 42, , Bdrn, Hmdn., Comprtive study for under-floor heting using solr collectors or solr ponds. pplied Energy 77(1), , Becker R. nd Pciuk., Effects of heting ptterns on overll therml performnce of dwellings, Energy nd Buildings, 20(2), , Bouchlghem N., Optimising the design of building envelopes for therml performnce, utomtion In Construction 10), , Dlmgkidis K, Kolokots D, Klitzkis, Stvrkkis G.S.Reinforcement lerning for energy conservtion Figure 8. Iso-PV lines for thick o-vlues t 1.00m. nd comfort in buildings. Building nd Environment, 42, , Fnger,P.O., Therml Comfort, nlysis nd pplictions in Environmentl Engineering, Dnish Technicl Press, Copenhgen, Fernndez-Gonzlez., nlysis of the performnce nd comfort conditions produced by five different pssive solr heting strtegies in the United Sttes idwest. Solr Energy 81, , rtinez PJ, Velzquez, Viedm., Performnce nlysis of solr energy driven heting system, Energy nd Buildings, 37(10), , Nicol F, Humphreys., ximum tempertures in Europen office buildings to void het discomfort. Solr Energy, 81, , Sttri S., Frhnieh B., prmetric study on rdint floor heting system performnce, Renewble Energy, 31, , Yeo. nd others., Historicl chnges nd recent energy sving potentil of residentil heting in Kore, Energy nd Building, 35, , Zhi XQ, Wng RZ, Di YJ, Wu JY, Xu YX, Q. Solr integrted energy system for green building. Energy nd Buildings, 39(8), ,

8 Cüneyt KURTY, He ws born in nkr, He grduted s rchitect from D on He hs.s degree from ETU (ODTÜ)-Fculty of rchitecture on 1985 nd Ph. D. From GZİ University- Deprtment of rchitecture on He hd been Nottinghm University, Fculty of rchitecture, Nottinghm, Englnd, 1996 s Postgrdute student. He is working s ssistnt Prof. t Gzi University, deprtment of rchitecture. He hs reserch bout solr energy, ppliction on renewble energy nd lighting in buildings. He hs severl rtie nd project in Turkey nd brod. İbrhim TILGN, He ws born in Eskişehir, He grduted s echnicl Engineering from D on He hs.s degree nd Ph. D. from GZİ University, deprtment of echnicl Engineering on 1987 nd He is working s ssistnt Prof. t GZİ University, deprtment of rchitecture. He hs reserch bout het trnsfer, thermodynmic, ppliction on renewble energy nd combustion technology. He hs severl rtie nd project in Turkey nd brod. Ö.Ercn TER, He ws born in nkr, He grduted s echnicl Engineering from ETU (ODTÜ) on He hs.s degree nd Ph. D. From Lncster University, UK, Deprtment of echnicl Engineering on 1974 nd He is working s Prof. t Gzi University, deprtment of rchitecture. He hs reserch bout het trnsfer, thermodynmic nd cooling systems. He hs severl rtie nd project in Turkey nd brod