PASSIVE USE OF SOLAR ENERGY IN DOUBLE SKIN FACADES FOR REDUCTION OF COOLING LOADS

Transcription

1 PSSIVE USE OF SOLR ENERGY IN DOUBLE SKIN FCDES FOR REDUCTION OF COOLING LODS naolj Borodnec Jurg Zem lekej Prozumen Rga Techncal Unvery P. o.box 526, LV-00, Rga, Lava BSTRCT The paper preen mehod how he olar energy can be ued for mprovemen of energy effcency of large publc buldng whou ung echncal equpmen uch a olar collecor, olar panel and ec. The paper devoed o he analy of pobly for conrucon of double kn facade wh changeable hermal performance for mnmzaon of energy conumpon by ar condonng yem. I decrbe he poble for opmzaon of hermal characerc of double kn facade n order o mprove buldng energy performance by maxmal ue of olar radaon ncludng alo he ho ummer day wh nenve olar radaon when uually hadng devce preven olar radaon. The paper gve mahemacal model for regulaon of elemen of double kn facade dependng on oudoor ar parameer and level of olar radaon. I propoe conrucve uggeon o creae buldng whoe wall, roof and glaed urface have changeable hermal characerc and mehodology of conrol for eparae elemen. KEYWORDS Conrolled hermal reance, energy performance, olar energy, double kn facade. INTRODUCTION Snce 970e he U-value of buldng envelope ha reached reaonable mnmum: 0. W/(m 2 K) for wall, roof (9) and 0.8 W/(m 2 K) for wndow (0). The prncple of olar geomery are well decrbed and effcenly ued n buldng degn age (). he momen here ex varou echncal decon of facade, whch gve he poble o mprove performance ung olar energy (8). The double facade have he man role n creaon of energy effcen publc and offce buldng. Reearch (8) how he nfluence of dfferen echncal decon of double kn facade on reducon of room coolng load. In addon daa (4) how ha ummer venlaon hrough a double facade wll ncreae room coolng load even more and hould no be recommended. The udy (6) how ha exceve ncreae n emperaure n he pace beween he facade kn n ummer ha a number of dadvanage uch a affecng he comfor of he occupan due o he ho radaon comng from he neror kn. There are alo exng approache (5) o ue he buldng envelope wh changeable hermal reance for ngh coolng. Thee mehod propoe o reduce hermal reance durng he ngh n order o cool down pace. The reducon of hermal reance acheved by ung moveable par of buldng envelope uch a roof conrucon and ac floor. ll before menoned ude are focued on ue of double facade for maxmal reducon of hea gan n ummer perod and ue of olar energy for heang durng he prng and auumn. Thee mehod uually are ued ogeher wh pave heang and pave coolng raege a well a wh acve heang and coolng mehod. So a can be concluded he radonally energy effcen buldng are uppoed o have maxmally hgh hermal and olar reance of buldng envelope. Bu n pracce hgh hermal reance only needed n colde wner day n counre wh cold clmae or n ho ummer day. lo he daa (3) propoe dea ha he buldng envelope needed only o preven from ran, nec or o gve he nmacy and no needed from he pon of

2 energy effcency, a doe no have o form he held agan he hea or vapour flow. In oher day, buldng wh full ar condonng would have o have dfferen propere of buldng envelope, ncludng alo hadng devce ha could allow hea flow n boh drecon (2). The paper preen nnovave mehod how he ncreae of hea gan can reduce oal energy conumpon by full ar-condonng yem. The double kn facade can be effcenly ued for regulaon of buldng envelope hermal and olar reance a dp.max H=QT/L 7a X=G/L H.mn. Xmax Xmn H.max. 2. RESERCH METHODS Reearch mehod baed on analy of neracon beween clmae, HVC yem workng regme and hermal propere of buldng envelope. For he olar radaon here no common parameer for characerzaon of he buldng envelope ably o re he nfluence of olar radaon. Bu h propery of buldng envelope may be hown a reance o olar radaon R R. The reance o olar radaon: R I R =, m 2 K/W () R I Where: Φ R hea flow from olar radaon comng o he ouer de of buldng envelope, W; Φ I he olar radaon hea flow ha ge nde, W. If here are hea ource n he nde pace and oude ar emperaure e lower han nde ar emperaure, o enure conan nde ar emperaure he buldng envelope hea loe ha o be equal o he nernal hea gan. In ha cae he hermal reance of buldng envelope rucure ha o be: e R T =, m 2 K/W (2) where: area of buldng envelope rucure, m 2 ; Φ hea gan, W. In order o evaluae he poenal of pave olar energy for reducon of coolng load, whch can be aborbed by exernal buldng envelope, he reearch baed on HVC workng regme durng he year (2, 3). Fg. : The upply ar parameer and man regulaon regme of HVC on pychomerc char - n he zone he oudoor ar parameer mach requred upplyng ar parameer o he heang devce and ar humdfer are wched off; - n he 2 nd zone he ar heaed by he convecor ll he mnmal requred emperaure Smn f φ Smn... φ Smax or ll maxmal relave humdy φ Smax f Smn... Smax ; - n he 3 rd zone he ar heaed by he convecor ll enhalpy H Smn and hen mourzed ll φ Smax ; - n he 4 h zone he ar only mourzed ll he comfor zone upper level ll φ Smn f θ Smn... θ Smax or ll θ Smax f φ Smn... φ Smax ; - n he 5 h zone he ar mourzed ll moure conen x Smn and hen addonally heaed by oher heang devce ll θ Smn ; - n he 6 h zone he ar heaed by he wall mouned convecor wh nake ar upply ll he maxmal poble emperaure Tmax ; mourzed ll moure conen x Smn and hen addonally heaed by oher heang devce ll θ Smn. - n he 7 h zone he ar cooled ll comfor zone mnmal emperaure, θ Smn or le n cae, when nernal hea gan are oo hgh; - n he 8 h zone ar cooled ll X Smn or ll X Smax and hen addonally heaed by heang devce ll θ Smn. - In he 9 h zone ar cooled ll X Smn and hen mxed wh oudoor ar ung bypa. 3. SPECIFICS OF HVC WORKING REGIMES IN SUMMER TIME There are four man emperaure ha are uually ued o evaluae he ar condonng workng parameer: emperaure of oude ar e, 0 C; emperaure of nde ar (workng zone), 0 C; emperaure of upply ar, 0 C; emperaure of exhau ar ex, 0 C. 2

3 hea gan, Q The emperaure of upply ar and exhau ar are he mo mporan for creaon of opmal ndoor ar parameer and enurng of HVC energy effcency. The ypcal offce buldng ha he hea and moure producon (ΔQ>0, ΔG>0) durng he ummer me. So he upplyng ar pang hrough he workng zone amlae he hea and moure and he emperaure and moure conen of exhau ar re. Fgure 2 how he proce n room wh normal olar radaon and hermal reance. In general he capacy of ar condonng yem n dew pon regme could be calculaed ung he followng equaon: Q H H kwh (5) oal coolng heang, where: H c energy conumpon for oudoor ar coolng, kwh; H h energy conumpon for uppled ar heang, kwh. O c E - exhau ar B S - upply ar I - workng zone C D E C D E moure producon, d x, mg/m Fg. 2: Proce n room wh normal olar radaon and hermal reance 3 - dcomfor zone Fg. 3: Typcal ar condonng workng regme ( dew pon regme ) The drecon of proce of change of ar parameer can be decrbed a followng (ar exchange rae 0 <n<): Q 0 (3) G x x m (4) ex x ex x where:, x emperaure and moure conen n he work area;, x - n upply ar; e, x e - n exhau ar. Double kn facade can be ued n nnovave way n ho ummer perod, when he oude ar emperaure hgher han nde ar emperaure and/or when olar radaon acve enough. In ha workng regme afer he coolng of oudoor ar (proce -B-C) he heang devce hea up upply ar ll mnmal requred emperaure (C-D) and nernal hea gan furher hea ar ll comfor zone (D-E) (Fg. 4). lo poble o mourze ar ( - C ) and hen heang devce hea up upply ar ll mnmal requred emperaure (C -D ) and nernal hea gan furher hea ar ll comfor zone (D -E ). can be een from above menoned fgure, olar energy hrough he double kn facade can be ued n order o reduce heang load ung olar radaon and hea ranfer from oude ar o nde hough he buldng envelope n order o hea up oudoor ar ll mnmal requred upplyng ar emperaure. Dcomfor zone mean ha he capacy of arcondonng yem no enough o enure requred parameer of ndoor ar. For ha purpoe neceary o reduce hermal performance of buldng envelope and reance o olar radaon. In ha cae he proce n room D-E and D -E can be exended. In cae when exernal hea gan could be ued for upply ar heang he energy conumpon of ar condonng yem for ar heang wll be equal o exernal hea gan: H Q e. h. g (6) Change of ar parameer n room wh normal and reduced olar radaon and hermal reance are hown n Fgure 4. 3

4 hea gan, Q O c Δ normal Δ reduced RR and RT reduced RR and RT normal I - workng zone m=0.75 S4' S4 S3 S' I E2 E3 E E4 S m=0.5 S2 moure producon, G x, mg/m 3 S3' S2' Fg. 4: Proce n room wh normal and reduced olar radaon and hermal reance The emperaure of upply ar can be gnfcanly lowered n cae of reduced hermal and/or olar performance of buldng exernal envelope. Thu he requred energy conumpon for uppled ar heang H can be reduced. In pracce parameer of upply ar vare n allowed lm: emperaure and relave humdy. Parameer of upply ar n 2-dmenon model (emperaure and relave humdy) can be expreed by he followng equaon: ( ) ( ) ( ) ( ) (7) h Fg. 5: Dependence beween parameer of upplyng ar and ar exchange rae n cae of buldng envelope wh regulaed hermodynamc parameer In order o keep conan and x, neceary o change he locaon of upply ar parameer S. Border area of upply ar parameer depend on ar exchange rae. For example, f m = 0.5, S vare on fgure S S 2 S 3 S 4, when m = 0.75, hen S 'S 2 'S 3 'S 4. Schemac proce n room hown n Fgure 5. x x Q e. h. g Snce and are conan under all value, equaon 7 can be modfed a follow: ( ) ( ) ( ) (8) The change of upply ar parameer n cae of dfferen ar exchange rae are hown n Fgure 5. The reducon of upply ar emperaure compenaed by hea gan Fg. 5: Schemac proce n room The exng udy (3) how ha opmal dfference beween he upply and exhau ar emperaure : 6 0 C 9 0 C for ndural buldng; 4 0 C 0 0 C for ale area; up o 4 0 C for pace for celng hegh more han 3m. 4

5 The choen upply ar emperaure hould nure no only he energy effcency bu alo human comfor. The general value whch characerze he human comfor level draf rae. The draf rae could be calculaed ung he daa n exng andard (). The dfference beween he upply and exhau ar emperaure can be reduced below he daa (3) n cae of reducon of ar velocy n workng area and opmal plannng of pace floor. The reducon of ar velocy n workng area can be acheved by ung appropraed ype of dffuer. Fg.6: Poble regulaon of hermal reance by changng ar velocy n ar gap Prelmnary dffuer eng reul have hown ha he mo opmal are dffuer wh plan and perforaed face plae. T = 8 K plan dffuer performed very good reul wh repec o human hermal comfor. Dffuer wh perforaed face plae are recommended when warmer ar uppled or a low-mpule upply condon. 4. OPTIML THERML ND SOLR RESISTNCE OF DOUBLE SKIN FCDE FOR REDUCTION OF COOLING LODS On he ba on equaon he neceary opmal hermal performance of buldng envelope for ummer workng regme of HVC yem can be calculaed accordng o: If If > hen R = e T < e hen R T e * e * R T canno be negave hould be 0 If e hen R T = e 0* 0 In cae of ummer workng regme he followng neracon can be ued n order o fnd opmal hermal reance of buldng envelope: { (9) (0) () Fg.7: Regulaon of olar reance ung exernal hadng Comparng o he oher echncal decon decrbed above, conrolled buldng envelope provde he pobly o reduce energy conumpon boh n he wnerme and n he ummerme. The mple mehod for regulaon of hermal performance of envelope o change nulaon propere of ar layer. lhough uch way of regulaon of hermal performance of buldng no deal, could be regarded a he fr ep n creaon of a new generaon of buldng envelope, whch provde poble for reducon of energy conumpon ung olar energy. In addon o mehod preened by daa (5) alo he prncple of TOMBLE wall (7, 2) can be adoped for ue of olar hea gan for reducon of buldng coolng load. he momen one of he poble o regulae hermal performance of buldng envelope applyng of dfferen modfcaon of double-kn facade (3). 5. RESULTS If here are hea ource n he nde pace and oude ar emperaure e lower han nde ar emperaure, o enure conan nde ar emperaure he buldng envelope hea loe ha o be equal o he nernal hea gan. In ha cae he hermal reance of buldng envelope rucure ha o be: 5

6 If n he ame uaon wh nernal hea gan (Φ>0) oude ar emperaure hgher han nernal ar emperaure, hermal reance of rucure ha o be a bg a poble ( ), bu n cae when = e, he value of hermal reance doe no maer and may have any value. The mlar analy of oher poble uaon gve an algorhm of change and opmal value of hermal reance and reance o olar radaon. In pracce he choce of he regulaon mode depend on he level of echncal developmen and economc conderaon. Some of he regulaon decon, uch a huer or olar reflecor, are known for generaon. They are n complance wh he model decrbed n he paper bu hey were known long before and whou. On he oher hand he gven algorhm how all poble drecon of echncal developmen n order o mnmze annual hea conumpon of buldng. Buldng envelope wh changeable hermal reance, olar radaon reance gve he pobly o reduce energy conumpon by econd heaer and o reduce coolng load. 6. REFERENCES conrucon // Energy and Buldng, vol. 43, 20, p (8) Henonen J.,Vuolle M. The performance mulaon of double-kn facade n offce buldng wh hybrd venlaon yem. Helnk Unvery of Technology, Deparmen of Mechancal Engneerng, Laboraory of Heang, Venlang and r-condonng, NNUL REPORT 2003, p (9)hp:// ulaon_pave_houe.hml (cceed March 09, 202) (0)hp:// ndow_u.hm(cceed March 09, 202) () Narenda K. Banal, Gerd Hauer, Geno Mnke. Pave Buldng Degn: a hand book of naural clmac conrol. - Elever Scence, 994, p (2) Sadnen S., Madala S., Boehm R. Pave buldng energy avng: revew of buldng envelope componen // Renewable and Suanable Energy Revew, vol.5, 20, p (3) Todorovc B. Pa, Preen and Fuure Buldng envelope- human body hermal behavor a fnal goal. Proc. 6 h Inernaonal Conference Energy for Buldng Lhuana, 2004, p (4) Бондарь,Е.С., Гордиенко,А.С., Михайлов, В.А., Нимич. Г.В. Автоматизация систем вентиляции и кондиционирования воздуха. Киев Аванпосм-прим, с. () SHRE SHRE Sandard , Thermal Envronmenal Condon for Human Occupancy. lana: mercan Socey of Heang, Refrgerang, and r-condonng Engneer, Inc. (2) Borodņec., Gaujēna B., Krēlņš. Opmzaon of energy conumpon by ar-condonng yem by mplemenaon of buldng envelope wh conrolled hermal reance// Proceedng of 0h REHV World Congre CLIM 200, nalya, Turkey, 9 2 May, 200. p 5. (3) Braukn U.,Borodņec., Krēlņš., Conrolled Buldng Envelope for Energy Sorage // Proceedng of h Inernaonal Conference on Thermal Energy Sorage, Sweden, Sockholm, June, p (4) Ecker U., Fux V., Bauer U., Me L., Infeld D. Facade and ummer performance of buldng // Energy and Buldng, vol. 40, 2008, p (5) Gvon B. Pave and Low Energy Coolng of buldng. Van Nor and Renhold, 994. p (6) Graa E., Herde. Naural venlaon n a double kn facade// Energy and Buldng, vol. 36, 2004, p (7) Haanan.., Hokam E.M., Mallck T.K. Effec of olar orage wall on he pave olar heang 6