Experience from PV system performence including comparison of on-roof and façade systems. (Case study on BIPV systems.)

Transcription

1 Expeience fom PV system pefomence including compaison of on-oof and façade systems. (Case study on BIPV systems.) Vitezslav Benda CTU Pague, Faculty of Electical Engineeing

2 Intelligent enegy management in the household Zeo enegy house cannot opeate without PV system

3 PV systems may be integated into building constuction PV system output powe depens on Iadiance Opeating tempeatue

4 ε v ϕ α β P ad ε h ) ( )cos ( cos ) ( ) ( sin 1 t t t B h v t ε ε ϕ = dt t t W h v t SS SR u ) ( )cos ( cos ) ( sin 1 ε ε ϕ = S J V Z , ,5

5 Radiation aiving on PV module Clea sky Cloudy sky inceases potion of diffuse adiation Reality:

6 In the yea 2001, a 3kW p demonstation, on-gid connected photovoltaic system has been built at the Czech Technical Univesity in Pague on the oof of the Faculty of Electical Engineeing.

7 Installed peak powe: 3320 W p Total module aea: 26 m 2 Numbe of modules: 30 (3 fields of 10) Latitude: N Altitude: 205 m

8 PV field Tilt angle Module type P m (W p ) 1 45 RADIX vaiable RADIX RADIX Paametes of individual PV fields Invetes: Fonius Sunice Mini

9 Enegy poduced by individual PV fields in peiod fom Januay 2002 to May 2009

10 A compaison of estimated and measued enegy poduction in peiod fom Januay 2002 to May 2007

11 Compaison of on-oof and façade PV field in the yea 2006

12 The module efficiency depends on iadiance and sola cell opeating tempeatue Both fill facto and efficiency decease with tempeatue FF T < 0 η < 0 T 1 At cystalline silicon cells % K η T η

13 Tempeatue dependece of enegy convesion efficiency Efficiency (%) 15,0 14,0 13,0 12,0 11,0 10,0 Tempeatue Efficiency 35,0 30,0 25,0 20,0 15,0 10,0 5,0 0,0 PV field tempeatue ( C) 9,0 Febuay Mach Apil May June July August Septembe Octobe Novembe -5,0 This gives the efficiency decease of about 0.6% pe 1K, which is highe than supposed decease of cell efficiency (about 0.4% pe 1K). It means that an incease of losses with inceasing tempeatue in othe pats of system cannot be neglected.

14 August Januay

15 PV modules ubbe sealing Cell opeating tempeatue hadened glass EVA thca thcaf = thcaf thcaf d + thcab thcab 1 T = T + c a d = λ thca G f b = + thcab λ f h f b hb Module tempeatue T mod can be measued on the ea of the module + 1 ab Al fame back coveing foil (tedla) PV cells T c = T mod + T G G SCT

16 Influence of tempeatue Open cicuit voltage V OC depends on the cell tempeatue T c T c Geff = Tm + * G T Tempeatue of the back suface T m vw T G [ T exp( bv T ] eff m = Ta + * 1 W ) + G is the wind velocity 2

17 The cell tempeatue incese depends on the ambient temeatue, the iadiance and the wind speed w thcab d b = λ b + 1 h b thcaf d f = λ f + 1 h f h k = A k ( w) 3/ 4

18 Tempeatue distibution ove the PV field aeas 45 90

19 Tempeatue distibution ove the PV field aeas 30 (oof) The module tempeatue distibution is position sensitive

20 The cell opeating tempeatue in the case of building integation The building suface should be themally isolated Placing PV modules diectly on the themally isolated suface esults in one-side cooling and consequently, in a highe opeating tempeatue thcaf d T = T + c 1 a thca G d ab 1 thca = thcaf thcaf >> + f b = + thcab thcab = + thcaf thca thcaf λ f h f λ b hb thcab thcab Cooling the back suface of PV modules is vey impotant

21 Non-unifom tempeatue distibution on a backventilated PV façade south-west oiented, 3 independent PV fields (E1, E2, E3), 2 sepaated pats 176 c-si PV modules Solatec SI W p / 24 V, kw p in total, m mm wide natually ventilated ai gap between PV modules and insulated wall - geomety of the PV facade - - photo of the PV facade -

22 Tempeatue distibution daily peak tempeatues at (30 min afte iadiance peak) ambient conditions (G ho =675 W/m 2, G in-plane =644 W/m 2, amb. temp C) the tempeatue distibution is highly non-unifom along the height

23 The sting is opeating at MPP I = I mp Expeimentally found I mp pactically independent on tempeatue n P mp = Imp Vmp( Ti ) = nimpvmp( TAV ) i=1 T AV is aveage cell tempeatue in the sting

24 Stings in paallel It is impossible to opeate both in paallel connected cells (stings) of diffeent tempeatues in maximal powe points (MPP) at the same time The efficiency decease due to in paallel connection of cells with diffeent tempeatue was about 0.15% pe C in compaison with cells opeated on the same (aveage) tempeatue

25 Measued vs. calculated pofiles of convesion efficiency and DC output powe fo the façade PV field in the peiod of the highest tempeatue non-unifomity. η conv = η STC. (1 + γ(t cell T cell,stc )) η conv = η STC. (1 + αi(t cell T cell,stc ).( 1 + c 1. ln(g/g STC ) + + c 2. (ln(g/g STC )) 2 + β V (T cell T cell,stc )) 16% 14% DC output powe Efficiency (%) 12% 10% 8% 6% 4% convesion efficiency DC output powe (W) 2% 500 0% Euopean Summe Time (hous) EFF measued EFF calc - simple EFF calc - Huld P measued P calc - simple P calc - Huld

26 100 mm wide natually ventilated ai gap between PV modules and the oof themal isolation

27 Conclusions Facade PV system applications can poduce about 66% of electical enegy poduced by the oof (45 tilted) one Efficiency of PV systems is stongly influenced by tempeatue PV field constuctions should allow an effective cooling of PV modules In paallel should be connected the module stings with the same aveage tempeatue