SOLAR COLLECTORS. Werner Weiss. AEE - Institute for Sustainable Technologies (AEE INTEC) A-8200 Gleisdorf, Feldgasse 19 AUSTRIA

Transcription

1 SOLAR COLLECTORS Werner Weiss AEE - Institute for Sustainable Technologies (AEE INTEC) A-8200 Gleisdorf, Feldgasse 19 AUSTRIA

2 Conversion of solar radiation energy into other energy forms Source: ENREL

3 TYPES OF COLLECTORS

4 Plastic Absorber

5 Flat plate collectors

6 FLAT-PLATE COLLECTOR Source: IEA SHC Task 33

7 FLAT-PLATE COLLECTOR Transparent cover Insulation Absorber plate Tubes Source: Consolar

8 FLAT-PLATE COLLECTOR transparent cover connection pipe absorber insulation heat transfer medium pipe framework structure

9 ABSORBER - TYPES Meander absorber Harp absorber

10 Manufacturing of a Solar Collector

11 Manufacturing of a Solar Collector Source:GREENoneTEC / ESTIF

12 Manufacturing of a Solar Collector Source:GREENoneTEC / ESTIF

13 Strip absorber

14 Strip Absorber

15 Strip Absorber

16 Local Production in Uganda

17 Thermographic Photographs of Various Absorber Types Source: Treikauskas, Ingolstadt University

18 Absorber Material Aluminum or Copper? 37% 63% Aluminum Copper Source: Sonne, Wind und Wärme, 2009

19 Ultrasonic or Laser Welding? Ultrasonic or Laser? 2% 8% 5% 43% 43% Laser welding Ultrasonic welding Soldering Mechanical Other (Glue, Plasma welding) Source: Sonne, Wind und Wärme, 2009

20 Full Size or Strip Absorber Full Size or Strip Absorber 8% 92% Full Size Absorber Strip Source: Sonne, Wind und Wärme, 2009

21 Absorber Colors Blue or black? 10% 5% 85% Blue Black Chrome Other (AIOx, NiOx, etc.) Source: Sonne, Wind und Wärme, 2009

22 Snake Type or Register Absorber? Snake Type or Register? 11% 38% 44% 7% Snake Double Snake Register Double Register Source: Sonne, Wind und Wärme, 2009

23 CPC - COLLECTOR

24 CPC - COLLECTOR

25 Evacuated Tube Collectors

26 Evacuated Tube Collectors

27 Evacuated Tube Collectors Heatpipe, Vitosol 300 (left) / Direct coupled Sydney Collector (right)

28 Direct flow U-tube with cylindrical absorber Detail Sydney collector

29 Direct flow U-tube with flat absorber Source: Frei, U.: Kollektoren in solarthermischen Systemen, SPF Solartechnik Prüfung Forschung, TriSolar98

30 Lenz Tube Source: SWW 08/20006 S.46

31 Evacuated Tube Collectors Detail Sydney collector

32 Evacuated Tube Collectors

33 Evacuated Tube Collectors Heat Pipe

34 Evacuated Tube Collectors Heat Pipe

35 Heat Pipe Principle Wet Connection

36 Error indication Vacuum present Vacuum faulty

37 Evacuated Tube Collectors

38 THERMOSYPHON SYSTEM - China

39 Evacuated Tube Collectors Source: Consolar

40 Concentrating Collectors

41 Parabolic Trough Collector

42 Working Principle - PTC

43 Tracking of the sun Collector axis oriented north-south

44 Built Examples

45 Process Heat Collectors AEE INTEC and Button Energy 70% 2nd Prototype 2. 2nd 2. Prototype (mit(evacuated evakuiertem glass Hüllrohr) tube) 60% Wirkungsgra ad 50% 40% 30% 20% 1. Prototyp 10% 0% 0,00 0,05 0,10 0,15 0,20 0,25 0,30 (T m -T u )/I DNI in m² K/W

46 PSE AG Germany Fresnel Process Heat Collector Aperture area: 88 m² Working temperature: max. 200 C

47 CONCENTRATING COLLECTORS - CCSTaR Universitat de les Illes Ballears

48 Process Heat Collectors CPC Collector Concentration: 1,8x Efficiency n Air 1 bar Air 0,01 bar Krypton 0,01bar Temperature difference T_Coll_mid - T_Amb [K] LoCo EvaCo (Low concentrating evacuated flat collector), ZAE Bayern

49 COLLECTOR MATERIALS?

50 ABSORBER MATERIALS THERMAL CONDUCTIVITY absorber material thermal conductivity [W/mK] steel 50 aluminium 210 copper 380

51 ABSORBER COATING Selective coating: 0 ε < 0.2, α > 0.9 Partially selective coating: 0.2 ε < 0.5, α > 0.9 Non selective coating: 0.5 ε < 1.0, α > 0.9 Plain copper black paint galvanic coating physical vapour deposition or sputtering

52 ABSORBER COATING Source:Alanod-Sunselect / ESTIF

53 TRANSPARENT COVER MATERIALS cover thickness [mm] weight [kg/m²] solar transmittance Standard glass *) Standard glass, tempered Iron free glass, tempered Antireflective coated glass PMMA, ducted plate PMMA, double ducted plate *) danger of breaking determined by high collector temperatures

54 Collector test

55 TRANSPARENT COVER MATERIALS 4% Reflection Standard Solar Glass 4% Reflection (42) Standard Solar Glass

56 TRANSPARENT COVER MATERIALS Solar glass Solar glass with antireflective coating

57 TRANSPARENT COVER MATERIALS Solar trans smission AR coated Uncoated (42) Incident angle

58 Market Share of Clear and Structured Glass 9% 33% 59% clear glass structured glass AR-glass Source: Sonne, Wind und Wärme, 2009

59 Glass Thickness 30% 70% 3,2 mm 4 mm Source: Sonne, Wind und Wärme, 2009

60 INSULATING MATERIALS insulating material max. allowable temperature [ ] density [kg/m³] conductivity [W/mK] at 20 C Mineral wool > Glass wool > Glass wool > Polyurethane foam < Polystyrol foam <

61 Absorber Manufacturing Processes su ubstance-tosubstance connections non substancetosubstance connections Production Process Deficiencies Spot Welding - not possible with all metals, susceptible to corrosion,... Soft-Soldering Ultrasonic Welding Laser Welding Plasma Welding Splicing Clamping (various designs) - low processing temperature (stagnation!!!), - emission of flux residues, - no continuous substance-to-substance connection, - very high processing temperature, - micro-cracks in welding spots - very high processing temperature, - low processing temperature (stagnation!!!), - low heat conductivity of adhesive, - low heat conductivity of clamping (non uniform contact pressure,..),..

62 FLAT-PLATE COLLECTOR Simple Design Modul Collector Roof Integrated Collector

63 FLAT-PLATE COLLECTOR Advanced Design Module Collector Roof Integrated Collector

64 Physical Processes inside a Flat-Plate Collector reflection on the pane of glass heat loss through the pane of glass reflection on absorber occurrence of solar radiation heat loss through the rear and side walls

65 Losses of a basic Flat-plate Collector Source: Source: Wagner & Co.

66 Characteristic Values of Flat-plate and Evacuated Tube Collectors Qcoll is the energy collected per unit collector area per unit time FR is the collector s heat removal factor τ is the transmittance of the cover α is the shortwave absorptivity of the absorber G is the global incident solar radiation on the collector UL is the overall heat loss coefficient of the collector T is the temperature differential between the heat transfer fluid entering the collector and the ambient temperature outside the collector.

67 Collector Efficiency Curve (t m t a )/G [Km²/W]

68 Collector Efficiency η = Nutzenergie useful energy eingesetzteenergie solar energy η = η 0 a 1 ( tm ta ) ( tm ta )² a2 G G

69 Collector Efficiency s. T-Sol Collector data

70 Collector efficiency curve 0,8 Optical Losses 0,7 eta 0,6 0,5 0,4 Thermal Losses 0,3 Useful Energy 0,2 0, ,04 0,08 0,12 0,16 (TKm-TA) / GT [Km²/W] Stagnation Point

71 Efficiency of different collector types (calc) Evacuated Tube Collector Selective Flat-plate Collector Uncovered Absorber Simple Flat-plate Collector (t m t a )/G [Km²/W]

72 Area Definitions Apertur area

73 Possible Improvements of FPC on aperture are efficiency (based Hermetically sealed collectors with inert gas fillings; operating temperature Double covered flat-plate collectors; C Vacuum flat-plate collectors; and combinations of the above mentioned 1 AR 2 AR 3 AR standard flat-plate collector (T m -T a )/G in Km²/W Source: IEA SHC Task 33

74 Flat plate collectors?

75 Register-Type Absorber pipes (d= 10 mm)

76 Flat plate collectors 12 m²

77 Hydraulic connection of collectors