NUMERICAL SIMULATION OF WIND ACTION ON A SOLAR PANELS ARRAY FOR DIFFERENT WIND DIRECTIONS

Transcription

1 BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Pulict de Universitte Tehnică Gheorghe Aschi din Işi Tomul LIX (LXIII), Fsc. 4, 2013 Secţi CONSTRUCŢII. ARHITECTURĂ NUMERICAL SIMULATION OF WIND ACTION ON A SOLAR PANELS ARRAY FOR DIFFERENT WIND DIRECTIONS BY GEORGETA BĂETU *, CARMEN-ELENA TELEMAN, ELENA AXINTE nd VICTORIA-ELENA ROŞCA Received: July 16, 2013 Accepted for puliction: July 31, 2013 Gheorghe Aschi Technicl University of Işi Fculty of Civil Engineering nd Building Services Astrct. Wind ctions determines the most importnt lod in the design of the support systems of the solr pnels, wherever they re locted - on flt or pitched roofs or t the ground level. The gol of simultions of the interction etween wind nd the solr pnels y Computtionl Fluid Dynmics (CFD) is to estimte the complex wind flow nd pressures tht ct upon their surfce. In the study presented herein, the wind pressure cting on 12 solr pnels is simulted. The solr pnels re plced in regulr rry, mounted t ground level nd tilted t 30º. Five wind directions (0º, 30º, 45º, 135º, 180º) hve een nlyzed with the computer code ANSYS 12 CFX. Key words: wind ction; solr pnels; wind ngle of ttck; numericl simultions; pressure distriution. 1. Introduction Determintion of wind forces on the support systems of solr pnels is the suject of mny reserch studies. The ehviour of solr rrys immersed in erodynmic field, hs mde the suject of severl studies in the wind tunnel with tmospheric oundry lyer nd numericl simultions, using specilized softwre in computtionl fluid flow. In the lst decde numerous studies were * Corresponding uthor: e-mil: get_vsies@yhoo.com

2 10 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc performed in order to determine the pressure distriutions nd the size of wind forces on solr pnels locted on flt nd pitched roofs, uilding envelope or t ground level. Design of the nchor systems must e done so tht the extreme vlues of wind will not ffect the integrity of the solr pnels. The min prolem in design of the nchor systems is to determine the correct uplift forces s well s the pressure field, in order to find solutions to reduce them. For solr pnels locted t ground level (Fig. 1), the ssessment of the wind lods proves to e n esier tsk thn for pnels instlled on the roof top. Air flow is influenced y the presence of solr pnels nd the terrin roughness. Fig. 1 Solr pnels plced t ground level: in solr rry configurtion ( in consecutive rows ( In order to determine the verge wind speed nd the velocity profile, the influence of orogrphy nd roughness fctors specific for the terrin type, is fundmentl. Prticulrly in urn nd suurn res where the turulence of the wind is incresed ecuse of the incresed roughness of the oundry lyer it is importnt to find how it influences the interction etween the ir flow field nd the structures immersed in it. According to roughness conditions (different types of vegettion nd uilt res) the Romnin stndrd SR EN :2006 divide the terrin in five ctegories of exposure (Tle 1). At the ground level, the ir flow disturnce is not only consequence of solr pnels presence, ut it is lso influenced y loction (open field, ordering re or neighouring uildings) nd terrin topogrphy (SR EN /2006). The intensity of wind loding depends on the solr pnels rry (consecutive rows or isolted solr rrys), the incidence of wind nd the distnce etween the rows of pnels. It is known tht wind speed decrese on the lower prt of the tmospheric oundry lyer (Fig. 2), ut in the sme time the turulence intensity is fr incresed. In the cse of extreme winds, dmges my occur to the nchor systems of solr pnels.

3 Bul. Inst. Polit. Işi, t. LIX (LXIII), f. 4, Tle 1 Terrin Ctegories nd the Corresponding Roughness Length (SR EN :2006) Fig. 2 Profile of wind velocity nd turulnce in tmospheric oundry lyer. The Romnin code for the design of uildings to wind ctions scrcely gives informtion for the evlution of the wind lods on the solr pnels. The method of evlution of the wind pressures in this code tht my e extended nd pplied for the solr pnels is tht which offer guidnce for wind lods on on mono-pitched cnopies. According to SR EN wind force cting on

4 12 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc structure is determined sed on either glol force coefficients, c f, or locl pressure coefficients, c p. Glol force coefficients nd locl pressure coefficients, tke into ccount the comined effects of wind cting on the upper nd lower surfces of the cnopies for ll the wind directions (Fig. 3). Fig. 3 Loction of the ppliction point of the glol wind force cting on monopitch cnopies (SR EN /2006). Both of the fces of the solr pnel re sujected to wind pressures, the finl force eing otined from vectoril sum, the locl pressure coefficients for the norml component of wind force hving the sme significnce s of the resultnt of wind ction on these fces: cp =± cns ± cni, (1) where: c ns is the pressure coefficient on the in-wind surfce of the pnel nd c ni the pressure coefficient on the rer of the pnel (Fig. 4). c Fig. 4 Scheme of free stnding pnel in the ir flow (, c Rdu et l., 1986); nd the resulting movement due to flow seprtion (Bitsumlk et l. 2010). According with the sunlight conditions in Romni, solr pnels should e plced t ngles situted etween 30º nd 40º from the ground level. Scientific literture recommends tht solr pnels should e fcing the south

5 Bul. Inst. Polit. Işi, t. LIX (LXIII), f. 4, direction with smll devitions to south-est nd south-west. This study ims to determine the lods produced y wind ction on solr pnels rry, for different ngles of ttck nd the simultion consisted in wind cting upon group of 12 solr pnels plced in perpendiculr rows of 4x3 rry, plced t the ground level. 2. CFD Simultion Cses The numericl simultion ws developed using ANSYS 12 CFX code. The solr rry is immersed in the computtionl domin (Fig. 6, where it my e oserved the minimum dimensions respecting the specifictions from the literture). Five different incident ngles were considered, listed in Tle 2. The solr rry hs sq.m nd it consists in 12 solr pnels (Fig. 5 ). The rry is lifted t 0.6m height from the ground level. The dimensions of the solr pnels re: m length, m width nd m thick. Tle 2. CFD Simultion Cses Cse Pnel type Pnel inclintion Angle of ttck 1 Arryed 30º 0º 2 Arryed 30º 30º 3 Arryed 30º 45º 4 Arryed 30º 135º 5 Arryed 30º 180º Fig. 5 Pressure points distriution on the surfce of the solr rry. The pressure distriution ws evluted for the entire rry nd lso for every individul solr pnel. On the surfce of the rry, the pressure is mesured in 144 points for ech fce, ligned in 9 rows (Fig. 5 ), nd the resultnt pressure hs lso een clculted.

6 14 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc During the numericl simultion session, the wind speed considered ws 18 m/s nd the turulence intensity 10% for the ll five nlyzed cses. The pressures vlues on oth fces of the exposed solr pnels rry were registered. Fig. 6 Computtionl domin (Frnke et l., 2004) nd the ngles of the wind ction. 3. Results nd discussions For ll the nlyzed cses glol nlysis ws run in order to determine the verged pressure on the solr rry nd locl nlysis to identify the criticl pnels (sujected to the gretest wind pressures) of solr rry. The ngle of wind ction producing the lrgest lods ws singled out y compring the results Cse 1: Angle of wind ction t 0º The highest pressures occur on surfce of pnels 9, 10, 11 nd 12, plced on the top of the solr rry (Fig. 7). Pnel numer 2 is sujected to the smllest

7 Bul. Inst. Polit. Işi, t. LIX (LXIII), f. 4, c d Fig. 7 Pressure distriution on inwind fce () nd on rer fce () of the solr pnels, velocity contour (c) nd velocity vectors (d) for the ngle of ction of 0⁰. negtive men pressure vlue, 23.7 P nd the pnel numer 12 is sujected to the gretest negtive men pressure vlue, P (Fig. 8). The men pressure on the totl surfce of solr rry is P. Fig. 8 Men pressure on the solr pnels in rry Cse 2: Angle of Wind Action 30º When the wind ngle is t 30º, the left prt of the solr rry is more loded thn right one (Fig. 9). Like in the previous cse, pressure vlues re negtive on entire solr pnels rry with men vlue of P.

8 16 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc c d Fig. 9 Pressure distriution on the upper fce () nd the underside fce () of the solr rry, velocity contour (c) nd velocity vectors (d) for wind ngle ction of 30⁰. The pnel numer 9 is sujected to the smllest men negtive pressure vlue, P, followed y pnel 10 with men suction of P. On the pnel numer 3 the smllest vlue of men suction, P (Fig. 10). Fig. 10 Men pressure on the solr pnels in rry Cse 3: Wind Angle of Action 45º As in the previously nlyzed cses, over the entire surfce of the solr rry negtive pressure hve een found (Fig. 11). The men pressure otined for the solr pnels rry is P. The suction vlues in the left side re c d

9 Bul. Inst. Polit. Işi, t. LIX (LXIII), f. 4, Fig. 11 Pressure distriution on the upper fce () nd the underside fce () of solr rry, velocity contour (c) nd velocity vectors (d) for n ngle of wind ction 45⁰. up to 45% higher tht the vlues of the right one. Pnel numer 1 is the most strongly ffected y the men negtive pressure vlues, P. The smlles vlues re registered on pnel numer 4, the men negtive pressure eing 69.1 P (Fig. 12). Fig. 12 Men pressure on pnels of solr rry Cse 4: Wind Angle of Action 135⁰ For n ttck ngle of 135º, the men pressure on solr pnels hve oth positive nd negtive vlues. The negtive vlues re registered on the pnels plced t the extremities of the rry, while the pressures on centrl pnels re

10 18 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc c d Fig. 13 Pressure distriution on the upper fce () nd the underside fce () of solr rry, velocity contour (c) nd velocity vectors (d) for n ngle of wind ction 135⁰. positive (Figs.13 nd 14). The men pressure on solr rry surfce is 62.8 P. Pnel numer 12 hs the highest men negtive pressure ( ), nd pnel numer 7 hs the lowest positive pressure (16.253P). Fig. 14 Averged pressure on: pnels in rry; solr rry surfce Cse 5: Wind Angle of Action 180⁰ The men pressure mesured on solr rry surfce hs negtive vlue ( 39.7 P). The pnel numer 1 is sujected to the smllest vlue of men negtive pressure of P. The pnel numer 6 is sujected to the

11 Bul. Inst. Polit. Işi, t. LIX (LXIII), f. 4, c d Fig. 15 Pressure distriution on the upper fce () nd the underside fce () of solr rry, velocity contour (c) nd velocity vectors (d) for n ngle of wind ction 180⁰. smllest vlues, the men positive pressure eing 1.77 P. The resultnt pressures on ottom nd lterl sides of solr rry re negtive, while in the centrl zone positive pressures were registered (Figs. 15 nd 16). Fig. 16 Men pressure vlues on the pnels of solr rry surfce. 5. Conclusions From ll the nlyzed cses it hs een pointed out tht wind direction hs mjor influence on the pressure distriution on solr rry. Suction vlues re greter for wind directions of 30º, 45º, 60º nd 135º, due to the the incident flow which cretes conicl vortices on surfce of solr rry. These vortices mnifest symmetriclly in pirs, one on ech edge of solr rry, nd in the center of ech vortex n re of high suctions occurrs. The otined results for ech nlyzed cse where used to mke comprison etween men pressures developed on ech pnel of the solr rry. A glol nlysis ws performed; the men pressure ws compred for ech considered ttck ngle. The iggest suctions pper for ttck ngle of 45º respectively 30º.

12 20 Georget Băetu, Crmen-Elen Telemn, Elen Axinte nd Victori-Elen Roşc REFERENCES Bitsumlk G.T., Dgnew A.K., Erwin J., Evlution of Wind Lods on Solr Pnel Modules Using CFD. The Fifth Internt. Symp.on Comput. Wind Engng. (CWE2010), Chpel Hill, North Cliforni, USA, My 23-27, Frnke J. et l., Recommendtions of the Use CFD in Wind Engineering. Proc. of the Internt. Conf. on Urn Wind Engng. nd Build. Aerodynmics, Belgium, Rdu A., Axinte E.,Wind Forces on Structures Supporting Solr Collectors. J. of Wind Engng. A. Ind. Aerodynmics, 32, 89, (1989). Văsieş G., Axinte E., Telemn E.C., Numericl Simultion of Wind Action on Solr Pnel Plced on Flt Roofs with nd Without Prpet. Bul. Inst. Politehnic, Işi, s. Constr. Arhitect., LVIII (LXII), 1, (2012). Văsieş G. Contriuţii l studiul cţiunii vântului în contextul dezvoltării durile. Ph. D. Diss., Univ. Tehnică Gheorghe Aschi, Işi, Văsieş G., Axinte E., Romil C., Rdu A., Numericl Simultion of Wind Action on Solr Pnels Inclined with 30º nd Different Wind Directions. Proc. of the 10th Intent. Symp. Comput. Civil Engng., 2012 New Computtionl Concepts in Civil Engineering, Işi, Romni, My 25, Edit. Soc. Acd. Mtei Teiu Botez, * * * Eurocode 1: Actions on Structures. Generl Actions.Prt 1-4: Wind Actions. SR EN /2006. SIMULAREA NUMERICĂ A ACŢIUNII VÂNTULUI ASUPRA UNEI MATRICE SOLARE (Rezumt) Acţiune vântului reprezintă principl cţiune cre determină proiectre sistemelor de susţinere, indiferent de mplsment pe clădiri cu coperişuri tersă su în pntă su l nivelul solului. Pentru determinre presiunii vântului pe pnourile solre se folosesc progrme de simulre numerică curgerii fluidelor (CFD). În cdrul lucrării, modelre numerică s- relizt cu progrmul ANSYS 12 CFX şi implict studiul presiunii vântului, pentru cinci unghiuri de tc (0º, 30º, 45º, 135º, 180º), pe o reţe formtă din 12 pnouri solre mplste l nivelul solului, unghiul de înclinre cestei fiind de 30º.