Impact of controlled ventilation systems on energy consumption in mediterranean school buildings

Impac o Con olled Ven ila ion Sys ems on Ene gy Consump ion in Medi e anean School Buildings Samuel Domíngueza, Jesica Fe nández-Agüe ab,* and Miguel Ángel Campanoc Ins i u e o A chi ec u e and Building Science, 2 Reina Me cedes A enue, Se ille 41012, Spain a[email p o ec ed], b[email p o ec ed], c[email p o ec ed] *Co esponding au ho Keywo ds: Ene gy E iciency, The mal Com o , Ene gy Consump ion, school buildings Abs ac . Cu en s anda ds o indoo ai quali y (IAQ) in non- esiden ial buildings demand high ai enewal a es wi h di e en il a ion s ages and cons an low. Cu en ly, new school buildings mus inco po a e mechanical en ila ion sys ems which modi y adi ional hea ing ins alla ions in o de o comply wi h he equi emen s o indoo ai quali y and ene gy e iciency. This s udy analyses he echnical and ene gy ou comes in ol ed in a school building when changing om a adi ional cen al hea ing sys em wi h adia o s, o an HV sys em which ul ils he cu en egula o y amewo k. 1. In oduc ion The in oduc ion o new Eu opean en ila ion s anda ds (UNE-EN 13779:2008 [1]) o non- esiden ial buildings, has in ol ed a e y signi ican inc ease in he ou side ai a es used o he en ila ion o buildings, and in he il a ion equi emen s. The case o school buildings is o special signi icance due o he sensi i i y o he occupan s o he deg ada ion o indoo ai quali y, which has been linked o ai ela ed diso de s among occupan s [2], and he high occupa ion densi y and la ge annual ope a ion ime. This has obliged a change om adi ional hea ing sys ems o new Mixed o All-Ai ype sys ems which can ul il he equi emen s. Annual ene gy consump ion is expec ed o inc ease as highe le els o IAQ a e ob ained in school buildings, whils a emp ing o add ess he ene gy e iciency- he mal com o -indoo ai quali y dilemma [3,4,5]. The aim o his s udy is o assess he ene gy impac , in a s anda d ep esen a i e cen e, when e ol ing om a adi ional hea ing sys em wi hou con olled en ila ion (based only on na u al in il a ion and manual ope a ion o he openings, o a mo e complex Hea ing and Ven ila ion sys em, analysing he expec ed inc eases in he consump ion o he building and iden i ying he mos sui able sys em in e ms o ene gy e iciency. 2. Me hodology 2.1 School Building Case s udy The s udy was ca ied ou on an exis ing school building which ep esen s he base model o school cons uc ion in he Medi e anean a ea. The model was analysed using ene gy simula ions, ob aining he beha iou o he hea ing sys em and associa ed ene gy consump ions o his ini ial model, and o he models wi h HVAC sys ems [6] de eloped o comply wi h he equi emen s o ai quali y and hea ing in he building. 2012 In e na ional Con e ence on Powe and Ene gy Sys ems Lec u e No es in In o ma ion Technology, Vol.13 978-1-61275-011-8/10/$25.00 ©2012 IERI ICPES2012 327 The ene gy simula ion models we e ca ied ou using he DOE 2.2 engine h ough he CALENER-GT in e ace, he o icial Spanish ce i ica ion so wa e, ob aining he ini ial and inal ene gy consump ion and associa ed CO2 emissions o he building, enabling p ecise da a o be ob ained on annual, mon hly, and hou ly consump ion. The s udy objec was a 5 yea old, h ee s o y S a e school building (Fig. 1) and isola ed om o he buildings. I was la gely ep esen a i e o he ypology and cons uc i e de ini ion ound in he egional a ea, and was buil unde he Spanish enac men o Di ec i e 2002/91/EC [7]. Table 1 shows he he mal en elope. Figu e 1. Case s udy simula ions Table 1. Cha ac e iza ion o he he mal en elope Building elemen s U (W/m2K) Facades Double b ick mason y walls, 3cm plas ic insula ion 0.65 Openings 6+12+6 double glazing, aluminium ame 3.4 Roo s Conc e e amewo k, g a e co e , 6cm plas ic insula ion 0.41 In e nal walls Ligh b ick mason y walls, no insula ion - Ini ially, condi ions o he ope a ional alues o occupancy, ligh ing, hea ing, en ila ion and ai - igh ness we e es ablished acco ding o he o icial ime able. The occupancy schedule conside ed, a ied, depending on whe he i was a weekday o weekend. The building was conside ed o be unoccupied om 1 July o 31 Augus . The hea ing sys em wo ks om 20 No embe o 31 Ma ch ( aking in o accoun Ch is mas holidays), om 8:00 am o 12:00 pm ( aking in o accoun a educed se ice o he adminis a ion a ea om 16:00 o 18:00h). The en ila ion sys em mus be unning he whole ime he school is open due o he p esence o occupan s and he need o IAQ con ol (8:00 o 15:00 h. and educed occupancy om 16:00 o 18:00h). In compliance wi h na ional egula ions, a se empe a u e o 21°C was conside ed du ing he hea ing pe iod (no cooling sys em was en isaged). Despi e he Class I ca ego y conside ed as a design objec i e, he eal beha iou wi hou mechanical en ila ion shows a poo quali y indoo en i onmen , wi h CO2 le els o mo e han 1,000 ppm abo e he ou side ai le el in mos o he classes, which equa es o an IAQ le el IDA4 in S anda d EN-ISO 7730[8] . In he e olu ion models, whe e he supply o ou doo ai is con olled, he s udy conside ed a supply a e o 12.5 l/s pe occupan (Class I/IDA2 indoo ai quali y as a design objec i e), which mus ensu e a CO2 concen a ion below 600 ppm abo e he ou doo ai le el, as pe EN-ISO 15251[9]. 328 Table 2. Clima e alues in Huel a. Pe iod: 1971-2000 A e age mon hly Jan Feb Ma Ap May Jun Jul Aug Sep Oc No Dec Day empe a u e (°C) 11, 4 12,7 14,6 16 18,8 22,2 25,4 25,5 23,5 19,4 15,3 12,6 Maximum day empe a u e (°C) 16, 3 17,6 20,3 21,4 24,1 27,8 31,6 31,8 29,3 24,7 20,2 17 Minimum day empe a u e (°C) 6,6 7,7 9 10,7 13,4 16,6 19,2 19,3 17,7 14,2 10,4 8,1 Hou s o sunshine 170 170 223 246 303 339 372 347 277 211 173 148 2.2 Sys ems Analysed The analysis o he o iginal sys em o he building allowed he ene gy consump ion baseline o be es ablished. I is a adi ional hea ing sys em, wi h adia o s and a cen al diesel boile (H-RO), and lacks en ila ion con ol. In his case i may be conside ed ha indoo en ila ion is p o ided by he con inuous in il a ion h ough he he mal en elope and he olun a y opening o windows by he use . Field obse a ions indica e an app oxima e alue o one indoo ai olume enewal pe hou ; in his case, he ou doo ai is no subjec ed o any il a ion p ocess, wi h no gua an ee o any ou doo ai cleaning. The e is no p e-hea ing, which leads o signi ican he mal g adien s inside he class oom ( e ical and ho izon al). Al e na i e sys ems a e p oposed [10] which p o ide ea ed and con olled ou doo ai , all o hem ensu ing a minimum low o ou doo ai , a il a ion p ocess and p e-hea ing, and when possible, he use o hea eco e y. The sys ems conside ed a e as ollows:  Cen al Hea ing wi h dis ibu ed adia o s and Neu al Ai Mechanical Ven ila ion(HV:R+NMV): adia o s sol e he local hea ing loads, Ai Handling Uni s a e p o ided o supply esh ai a indoo condi ions, his sys em p o ides hea eco e y capaci y wi h high ene gy e iciency and uses a educed numbe o ans. Easie mois u e con ol i equi ed.  Cen al Hea ing wi h dis ibu ed adia o s and Passi e Mechanical Ven ila ion (HV:R+PMV): adia o s sol e he local hea ing loads and he en ila ion load, Ai Handling Uni s supply esh ai a ex e nal condi ions wi h no hea ing ea men . Fil e and an sys ems inc ease in numbe  Cen al All-Ai Sys em (HV-AIS): Cen al boile dis ibu es ho wa e o he Ai Handling Uni s dis ibu ed hough he building acco ding o he con igu a ion o he he mal a eas o he All-Ai cons an low sys em. The AHU´s p o ide he mal and en ila ion. I he low o he ou doo ai supply exceeds he he mal needs, he VAV does no unc ion.  Cen al All-Ai Sys em (HV-AISPT): Cen al boile dis ibu es ho wa e o he Ai Handling Uni s wi h local pos - ea men o he ai , adap ing i o a mul i-zone sys em. The AHU´s p o ide he mal ea men and en ila ion. The low o he ou doo supply emains ixed and he he mal load o he class ooms is adjus ed h ough he wa e pos -hea ing se s, which allows indi idual he mal con ol o each oom.  Cen al Ai -Wa e Sys em wi h neu al ou doo ai (HV-AWSN): A majo pa he ea u es o his sys em a e common o hose desc ibed abo e o HV:R+NMV ins alla ion, an-coil uni s a e used ins ead o adia o s, assuming he local hea ing loads, he Ai Handling Uni s supply esh ai a indoo condi ions. Excep o he i s sys em, hose p oposed allow he e olu ion o ai condi ioning sys ems (HVAC), which may be conside ed as a u u e s ep o p o ide all yea ound indoo en i onmen al con ol. In o de o ob ain a mo e simila compa ison scena io o he di e en sys ems, he he mal gene a ion is common o al, a con en ional diesel wa e boile wi h a 93% pe o mance, adjus ing he he mal ou pu o he indi idual powe equi emen . 329 3. Discussion and Resul s As di e en ene gy sou ces a e p esen in he models, he annual ene gy demand was con e ed o p ima y ene gy which allowed he ca bon dioxide emission uni s o be calcula ed. Table 3. Coe icien s o ene gy inpu s. Coe icien s o ene gy inpu s Final Ene gy Emissions o CO2 Elec ici y Gasoil Elec ici y Gasoil P ima y Ene gy 2,603 1,085 1,689 0,311 Decision-making o he in e en ion s a egy was ca ied ou guided by he ene gy assessmen o he building, bo h o i s o iginal condi ion and o he al e na i es, wi h a compa a i e analysis being es ablished o measu e he p edic ed ene gy consump ion. As expec ed he e was a subs an ial inc ease in annual ene gy consump ion and a ise in he associa ed CO2 emissions. Those sys ems ha mee he cu en equi emen s o indoo ai quali y, inc ease he inal annual ene gy consump ion by be ween 2.16 o 3.82 imes; he pos -hea ing o Fan Coil solu ions being hose which consume a smalle amoun o bo h inal and p ima y ene gy in he B4 clima e zone, bu ne e heless is double ha o he ini ial sys em H: OR. Figu e 2. Ene gy consump ion o di e en sys ems The mos ema kable aspec is he signi ican inc ease in ene gy consump ion associa ed wi h ai anspo in he building (mainly due o he ope a ion o he ans and he load losses in he il e s), especially in he HV-AIS sys em, assuming an inc ease in CO2 emissions o an o de o h ee o i e and a hal imes he ini ial le el. This badly a ec s he en i onmen al impac o he ope a ion o he building , and in ol es an impo an inc ease in he ope a ing budge o he building, due o highe cos o elec ici y e sus diesel uel. 330 Figu e 3. CO2 emissions o di e en sys ems 4. Conclusions The main conclusion o his s udy is ha he adi ional design c i e ia o he hea ing sys em should be modi ied o mee he equi emen s o indoo ai quali y associa ed wi h school use, wi hou eso ing o all yea ound ai condi ioning. All he sys ems wi h pos hea ing uni s o he mixed ype sys ems a e app op ia e, p o iding con olled ai en ila ion and hea ing capaci y. In he mixed sys ems, he an coil ype is he mos app op ia e, bu he simpli ied e sion ha inco po a es AHU´s o he adi ional adia o s may be conside ed as he simples solu ion ha allows e o i ing exis ing acili ies wi hou such an excessi e consump ion in compa ison wi h o he hypo heses. Special ca e mus be aken du ing he ins alla ion design p ocess o con ol ene gy e iciency aspec s, in o de o minimize high consump ion, bu no o he de imen o he indoo ai quali y. Re e ences [1] EN 13779:2008. Ven ila ion o non- esiden ial buildings. Pe o mance equi emen s o en ila ion and oom-condi ioning sys ems. B uxelles: CEN, 2008. [2] C.W. Baye ,. S.A C ow,. and J. Fische , Causes o Indoo Ai Quali y P oblems in Schools: Summa y o Scien i ic Resea ch, Columbia, MO, SEMCO, Inc.2000 [3] R. Becke , I. Goldbe ge , M. Paciuk, Imp o ing ene gy pe o mance o school buildings while ensu ing indoo ai quali y en ila ion, Building and En i onmen , ol. 42, pp. 3261-3276, 2007. [4] Eley Associa es, A chi ec u al Ene gy Co po a ion, & Accoun ing O ice, M. Imp o ing Indoo En i omen al Quali y and Ene gy Pe o mance o Cali o nia K-12 Schools1-1-17, 2003. [5] P. Wa gocki and D. P. Wyon. E ec s o HVAC on S uden Pe o mance. E ec s o HVAC on S uden Pe o mance, ASHRAE Jou nal 7, 2006. [6] J. Jalas, K. Ka jalainen and P. Kima , Indoo Ai and Ene gy Economy in school buildings. P oceedings o Heal hy Buildings 2000, ol. 4, 273 [7] Di ec i e 2002/91/EC o he Eu opean Pa liamen and o he Council o 16 Decembe 2002 on he ene gy pe o mance o buildings. 331 [8] ISO 7730:2005 E gonomics o he he mal en i onmen -- Analy ical de e mina ion and in e p e a ion o he mal com o using calcula ion o he PMV and PPD indices and local he mal com o c i e ia. [9] EN 15251:2007 Indoo en i onmen al inpu pa ame e s o design and assessmen o ene gy pe o mance o buildings add essing indoo ai quali y, he mal en i onmen , ligh ing and acous ics. [10] W. G ondzik and R. Fu s , HVAC Componen s and Sys ems, Vi al Sings Cu iculum Ma e ials P ojec . h p://a ch.ced.be keley.edu/ i alsigns/ es/downloads/ p/h ac/h ac-sml_op .pd 332