Some aspects of the energy cost linked to the IAQ. Impact of free-cooling and heat recovery in office buildings.

SOME ASPECTS OF THE ENERGY COST LINKED TO THE IAQ. IMPACT OF FREE-COOLING AND HEAT RECOVERY IN OFFICE BUILDINGS. Topic 3: HVAC Applica ions in Comme cial and Communi y Buildings R. Velazquez, S.Al a ez, J.F. Co onel, J. Gue a G upo de Te mo ecnia. Escuela Supe io de Ingenie os. Uni e sidad de Se illa.A da. Reina Me cedes s/n E-41012, Se illa (SPAIN) ABSTRACT Inc easing ai exchange a e o imp o e IAQ may inc ease ene gy consump ion, bu his inc ease may be compensa ed o by s a egies such as ee cooling and hea eco e y. The ame o he p oposed pape is he examina ion o he po en ial a a egional le el ( he Ibe ian peninsula) o he di e en s a egies men ioned abo e in ypical o ice buildings. Based on a se o e e ence building mo phologies, s udies a e conduc ed o e alua e he impac o inc easing ai en ila ion a es o di e en o ien a ions, quali y o he en elope (opaque walls and glazing), ope a ing schedules and indoo se -poin empe a u es. Then, he impac o he inc eased ai en ila ion a es is co ec ed by in oducing he e ec o ee-cooling, ai - o-ai hea eco e y de ices o di e en ypes and inally, he combined e ec o bo h ene gy sa ings s a egies. The esea ch p o ides Maps allowing: 1. To iden i y zones when hea ing o cooling egimes a e dominan , in e ms o bo h, peak load condi ions and ene gy equi emen s. 2. To compa e he expec ed pe o mance o he wo ene gy sa ing s a egies a a ce ain locali y. 3. To compa e he po en ial bene i o applying a gi en s a egy a di e en locali ies. 4. To indica e egions o ecommendable applica ion o he s a egies and he expec ed ene gy sa ings achie able. 1. INTRODUCTION AND CONTENTS The ene gy impac o en ila ion mus be concep ually examined a wo di e en le els: •The e ec on he building pe o mance o inc easing ai en ila ion a es in o de o imp o e IAQ. •The po en ial o educing he ene gy impac o inc easing ai exchanges by means o ee- cooling and ai o ai hea eco e y sys ems. F ee-cooling, some imes called en ila ion cooling, is pa icula ly sui ed o la ge o ice buildings whe e high hea loads a e de eloped h ough ligh ing, compu ing and o he elec ical sou ces. Thus, he building o en equi es cooling while he ou doo empe a u es 1 a e lowe ha indoo s. Ven ila ion a es o cooling will no mally be well in excess o ha needed o mee he basic esh ai equi emen s o occupan s. Ven ila ion hea eco e y is he p ocess by which he mal ene gy is eco e ed om exhaus ai o e-use wi hin he building. The s udies ha e been conduc ed based on a se o scena ios ep esen a i e o he scope o he p ojec . Consequen ly, he conclusions achie ed a e only applicable wi hin he ange de ined by he scena ios. The scena ios include loca ions, building mo phologies, building ope a ional and cons uc i e cha ac e is ics and e iciency o he hea eco e y sys ems. A i s le el o speci ic in o ma ion is p o ided o a speci ic building in wo loca ions, Mad id (Spain) and Po o (Po ugal). A second le el o gene alised in o ma ion is p o ided in a se o maps o he Ibe ian peninsula (Spain and Po ugal). This second s ep is aimed o know o wha ex en he conclusions ob ained in he i s le el a e applicable o o he buildings o loca ions. All he in o ma ion was ob ained ia hou ly based compu e simula ion, o which i was necessa y: • The gene a ion o he clima ic da a (Tes Me eo ological Yea s) o 35 di e en loca ions co e ing he di e en clima es o he Ibe ian peninsula. • A de ailed building ene gy analysis ool (PASSPORT PLUS So wa e) o ob ain he he mal load hou by hou , • The de elopmen o speci ic ou ines o cha ac e ise he pe o mance o he ee-cooling, hea eco e y and con en ional cooling coil componen s. • The de elopmen o pos p ocesso s o pe o m he massi e simula ions and analyse he esul s in an au oma ic way. • To compile easily a ailable clima ic da a (mon hly mean alues) o 40 addi ional si es o he Ibe ian peninsula o comple ely co e he geog aphic egion which would be ep esen ed in he maps. • To de elop physical and geog aphical in e pola ion p ocedu es o build up he maps. PASSPORT PLUS has been aken as he basic ool used inside his p ojec o he de ailed he mal building pe o mance. Passpo Plus is a dynamic simula ion so wa e o calcula e he he mal beha iou o mul i-zones and mul i-elemen buildings. This so wa e package has been de eloped in he ame o he Eu opean esea ch p ojec (PASCOOL) EC-JOU- 0013-CT92 o he XII Gene al Di ec o a e o he Eu opean Union. This so wa e is o ally compa ible wi h he simula ion o cooling and hea ing sys ems, and has been well es ed agains esul s om o he p og ams and expe imen al alues. I s in e nal s uc u e makes his p og am e y app op ia ed o he de elopmen and inco po a ion o p e-p ocesso s and pos -p ocesso so wa e speci ic o e e y di e en applica ion. 2 2. REFERENCE CASE A ep esen a i e o ice building has been selec ed. The building has squa e shape wi h 1600 m² (40 x 40 m) o loo a ea in each loo . I will be di ided in 6 di e en zones: sou h, eas , no h, wes , in e nal zone and alse ceiling (see igu e 1). The ex e nal zones (sou h, eas , no h and wes ) ha e an a e age dep h o 6 m; he es o he usable loo is in e nal zone. The alse ceiling will be simula ed as a ee loa ing zone, so ha , all he ene gy esul s he eina e will be e e eed only o he i s i e zones. In he ou acade he pe cen age o glazed a ea is 60 % and 40% he opaque one. The ex e io walls, glazing, loo s and ceilings a e ypical cons uc i e elemen o hese kind o buildings, wi h a medium le el o cons uc i e quali y. • Walls: Double b ick (12 cm), insula ion laye (5 cm), single b ick (7 cm) (U = 0.57 W/m²K) • Glazing: Double glazing 6-6-6 mm, Global sola T ansmi ance = 0.66 (U = 3.4 W/m² K) • Window F ames: Aluminum, low ai igh ness • Roo : Conc e e (3 cm), ai laye and ex uded polys y ene (3 cm), ce amic space be ween gi de s. (U = 0.61 W/m² K) Figu e 1: Scheme o one loo o he building Figu e 2: Scheme o wall and he oo This building will be s udied in wo di e en clima es inside he Ibe ian peninsula: • Po o (Po ugal) 3 La i ude: 41° 08’ N Longi ude: 08° 36’ W Al i ude: 10 m • Mad id (Spain) La i ude: 40° 27’ N Longi ude: 06° 06’ W Al i ude: 650 m Figu e 3: Mad id and Po o geog aphical loca ion. The sensible in e nal gains ha e been conside ed o be 30 W/m² (ligh s, occupa ion and equipmen ), cons an du ing all he wo king hou s. The wo king o occupa ion pe iod is 9- 14 and 16-19 hou s. The in il a ion a e ou o he occupa ion pe iod will be conside ed as 0.5 ai changes pe hou (ach) (2560 m3/h). The occupa ion densi y du ing he wo king pe iod is abou : 1 occupan / 10 m². The size o he ai condi ioning equipmen and he o al supply ai low used by he ai dis ibu ion sys em ha e been calcula ed using he cooling peak load o each zone. I has been assumed ha he i e di e en zones ha e i e di e en ai ea men uni s and i s dis ibu ion sys em. The cooling peak load is o all he cases highe han he hea ing peak load. So, o e e y di e en zone and e e y di e en en ila ion le el, he e will be a di e en cooling peak load and consequen ly a di e en sys em size. 3. BUILDING ENERGY PERFORMANCE 3.1. Building ene gy pe o mance - Re e ence case The ene gy equi emen calcula ions has been pe o med using 26.5 °C as se poin o cooling and 20 °C o hea ing. The equipmen ope a es du ing he wo king pe iod e e y day, being he building unde ee loa ing e olu ion he es o he ime. The e e ence en ila ion a e has been ixed 1 ach (1420 L/s) du ing he wo king pe iod ( o his building, 1 ach is equi alen o 8.9 li e s o ai pe second and occupan ). The supply ai low has been sized using he peak cooling load o he building (wi hou he en ila ion load). Consequen ly, he supply ai low depends on he zone and he clima e. The ollowing able shows he ene gy equi emen s and he peak loads zone by zone and o all he building. 4 Loca ion Zone Sensible cooling equi em. (kW·h/m²) To al1 cooling equi em. (kW·h/m²) Hea ing equi em. (kW·h/m²) Sensible cooling peak (W/m²) Hea ing peak (W/m²) Sou h 117.4 122.3 6.4 116.2 72.2 Eas 117.1 122.8 10.8 162.0 79.9 Mad id No h 72.3 76.7 12.3 97.2 72.3 Wes 116.1 121.5 12.8 152.5 79.9 In e n. 53.4 57.0 3.5 59.2 38.8 Building 81.1 85.5 7.2 98.6 58.2 Sou h 115.3 130.7 2.1 106.4 55.0 Eas 109.0 125.8 3.6 136.9 64.6 Po o No h 64.7 78.9 3.6 88.9 61.0 Wes 107.9 125.8 4.2 148.9 66.2 In e n. 49.5 61.9 0.8 56.9 28.7 Building 75.7 90.1 2.1 91.3 45.9 1To al: (Sensible + La en ) Table 1:Ene gy equi emen s and load peaks o he building placed in Mad id and Po o. I can be obse ed in he p e ious able and in he igu e 4 ha he cooling equi emen s a e much mo e impo an han hea ing o all he zones, bo h in Mad id and Po o ( emembe ha en ila ion e e ence le el is 1 ach). The la en cooling equi emen (To al - Sensible) is much mo e impo an o Po o han o Mad id (Po o has a highe le el o ou doo humidi y). 123456789101112 0 5 10 15 20 25 Load (kw·h/m²) 123456789101112 Mon h Cooling Hea ing Mad id 1 2 3 4 5 6 7 8 9 10 11 12 0 5 10 15 20 25 Load (kw·h/m²) 1 2 3 4 5 6 7 8 9 10 11 12 Mon h Po o Figu e 4: Mon hly ene gy equi emen s (hea ing and cooling) o Mad id and Po o 5 Figu e 4 shows he mon hly building ene gy equi emen s (cooling and hea ing) o he whole building placed in Mad id and in Po o. 0 10 20 30 40 50 60 70 80 90 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Hou W/m² 0 5 10 15 20 25 30 35 40 °C Cooling Load T. Ou doo Mad id 0 20 40 60 80 100 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Hou W/m² 0 5 10 15 20 25 30 35 40 °C Po o Figu e 5: Hou ly cooling load and ou doo d y bulb empe a u e o a ypical summe day in Mad id and Po o Figu e 5 shows he hou ly e olu ion o a ypical summe day, 15 h o July ( his day is no manda o y he cooling peak day). Toge he wi h he cooling load hou ly e olu ion, we ha e g aph he ex e io ambien d y bulb empe a u e. I can be no ed ha he e a e an in e al o ime (14 o 16) whe e he condi ioning equipmen is swi ch o and hus he loads a e ze o. The beha io o he whole building has been calcula ed adding zone loads. The e o e, he building pe o mance is e y closed o he beha io o he in e nal zone, due o he “weigh ” o he in e nal zone wi h espec o he ou e zones. Building ene gy pe o mance - Regional E alua ion Maps showing he egional dis ibu ion o peak loads and ene gy equi emen s ha e been included. Fo he building mo phology de ined be o e, hese maps ep esen a e ages o 6 di e en combina ions o cons uc i e and ope a ional cha ac e is ics de ined as ollows: 6 Va ia ion Walls Windows In e nal Gains (W/m²) 1 Re e ence wall wi hou insula ion Single 30 2 Re e ence wall Double 30 3 Re e ence wall Double & Re lec ing 30 Single 4 20 Re e ence wall wi hou insula ion 5 20 Re e ence wall Double 6 20 Re e ence wall Double & Re lec ing These maps a e no ex apola ion o he e alua ion o he e e ence building, bu ha e been calcula ed wi h he same de ail in he e e ence building. The e e ence wall is he one de ined in he igu e 2. The maps will always ep esen a e ages o he abo e men ioned buildings combina ions. I can be seen ha a egional le el: • Peak cooling is always highe han peak hea ing, al hough bo h a iables a e in he same o de o magni ude. • Cooling equi emen s a e conside able highe han hea ing equi emen s, excep in a small zone in he no hwes o he Ibe ian peninsula whe e hey a e o he same o de . Typically, i can be said han cooling equi emen s a e abou 5 imes bigge han hea ing equi emen s. In syn hesis, o 1 ach, cooling is dominan . Nex maps show he dis ibu ion o he a e age cooling and hea ing ene gy equi emen s o he o ice building simula ed (all o hen wi h a en ila ion a e o 1 ach ) wi hin he Ibe ian Peninsula Cooling (kW·h/m2) Hea ing (kW·h/m2) 35 100 90 25 70 50 10 0 0 Figu e 6:Ibe ian Peninsula maps o he a e age ene gy equi emen s o cooling and hea ing. 7 4. BUILDING ENERGY PERFORMANCE WITH DIFFERENT VENTILATION LEVELS Equi alencies e e ed o he building: ach 1 2 3 4 7.6 8.1 L/(s·occupan ) 8.9 17.8 26.7 35.6 67.6 72.0 L/(s m2) 0.89 1.78 2.67 3.56 6.76 7.20 Figu e 7 ep esen s he mon hly dis ibu ion o he building ( he whole building) sensible ene gy equi emen s wi h di e en en ila ion le els o Mad id. I can be seen ha he cooling equi emen has been concen a ed in he summe mon hs cause he en ila ion ai du ing win e and in e media e mon hs has became he cooling loads in o hea ing loads. 1 3 5 7 9 11 0 5 10 15 20 25 Load (kw·h/m²) 1 3 5 7 9 11 Mon h Cooling Hea ing 1 ach 1 3 5 7 9 11 0 5 10 15 20 25 Load (kw·h/m²) 1 3 5 7 9 11 Mon h Cooling Hea ing 4 ach Figu e 7: Mon hly ene gy equi emen s (hea ing and cooling) o he whole building wi h di e en le els o en ila ion in Mad id. When he en ila ion le els inc ease he o e all alues o ene gy cooling equi emen s emain almos unal e ed. Howe e he ene gy hea ing equi emen s do inc ease signi ican ly wi h he en ila ion le els. Nex igu es show hese e ec o Mad id and Po o. The di e ence be ween o al and sensible cooling a e no so impo an o Mad id, bu is no negligible o Po o. So he high le el o humidi y in Po o is a e y impo an ac o . Mad id 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 0123456789 Ai Changes pe Hou (ach) Ene gy equi emen s (kW·h/m² ) To al cooling Sensible cooling Hea ing Po o 0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0 0123456789 Ai Changes pe Hou (ach) Ene gy equi emen s (kW·h/m² ) To al cooling Sensible cooling Hea ing Figu e 8: Ene gy equi emen s (cooling and hea ing) e olu ion wi h he en ila ion le el o Mad id and Po o The peak cooling and hea ing load inc ease linea ly wi h he en ila ion le el, bu hea ing peak load g ows mo e han cooling one. 8 When he en ila ion a e inc eases, cooling equi emen inc eases o dec eases depending on he loca ions, bu hey do no change in a signi ican way in all he Ibe ian Peninsula. The compa ison wi h he e e ence case show de ia ions o wi hin ± 20% in all cases. This a ia ion, posi i e o nega i e, is due o he p esence o wo combined con adic o y e ec s: he cooling mon hs dec ease bu he cooling equi emen s associa ed o each mon h inc ease. Hea ing equi emen s g ows signi ican ly when he en ila ion a e inc eases. This is due o he inc ease in he numbe o hea ing mon hs. Compa ison be ween cooling and hea ing equi emen s show ha he zones wi h dominance o he cooling dec ease in such a way ha o 4 ach he hea ing and cooling dominance is spli abou 50%, as can be obse ed in he maps o he ollowing igu e Ven ila ion: 1 ach Ven ila ion: 4 ach Figu e 9: Ra io cooling o hea ing ene gy equi emen s o wo le els o en ila ion (1 ach & 4 ach) 9 REFERENCES • J. Cla ke. “Ene gy Simula ion in Building Design”. Adam Hilge L d, B is ol (1985). • J.F. Co onel, S.Al a ez. “De ailed Algo i hms o The mal and op ical pe o mance” in Model De elopmen . Vol 2 Sola Con ol. S. Sciu o ed. Final Repo o PASCOOL Resea ch P ojec . CEC CG 12 B ussels (1995). • J.F. Co onel, S.Al a ez, E. Rod iguez “PASSPORT Plus In e model compa ison” in PASSPORT Plus - Final Repo . S. Al a ez, C.A. Bala as eds. Final Repo o PASCOOL Resea ch P ojec . CEC DG 12, B ussels (1995). • E. Dascalaki, M. San amou is “PASSPORT-Ai Use ’s Manual”. Final Repo o PASCOOL Resea ch P ojec . CEC CG 12 B ussels (1995). • M. G osso “CPCALC-Use Manual”. Final Repo o PASCOOL Resea ch P ojec . CEC CG 12 B ussels (1995). • R. Judko , J.Neyma k. “In e na ional Ene gy Agency Building Ene gy Simula ion Tes (BESTEST) and Diagnos ic Me hod”. NREL Colo ado, a ailable NTIS and DOE, (1995). • P. Rousseau, E. Ma hews. “Needs and T end in In eg a ed Building and HVAC The mal design Tools”. Building and En i onmen , Vol 28,Nº 4 pp. 439-452, (1993). • S. Klein. “TRNSYS- A T ansien Sys em Simula ion P og am”. Uni e si y o Wisconsin - Madison, Enginee ing Expe imen S a ion Repo 38-12 (1988). • G. Wal on. ”The mal Analysis Resea ch P og am - Re e ence Manual”. NBSIR 83-2655, Na ional Bu eau o s anda ds (1983). 16