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

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

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

TYPES OF COLLECTORS

Plastic Absorber

Flat plate collectors

FLAT-PLATE COLLECTOR Source: IEA SHC Task 33

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

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

ABSORBER - TYPES Meander absorber Harp absorber

Manufacturing of a Solar Collector

Manufacturing of a Solar Collector Source:GREENoneTEC / ESTIF

Strip absorber

Strip Absorber

Local Production in Uganda

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

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

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

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

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

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

CPC - COLLECTOR

Evacuated Tube Collectors

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

Direct flow U-tube with cylindrical absorber Detail Sydney collector

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

Lenz Tube Source: SWW 08/20006 S.46

Evacuated Tube Collectors Detail Sydney collector

Evacuated Tube Collectors

Evacuated Tube Collectors Heat Pipe

Heat Pipe Principle Wet Connection

Error indication Vacuum present Vacuum faulty http://www.solardirect.com/

Evacuated Tube Collectors

THERMOSYPHON SYSTEM - China

Evacuated Tube Collectors Source: Consolar

Concentrating Collectors

Parabolic Trough Collector

Working Principle - PTC

Tracking of the sun Collector axis oriented north-south

Built Examples

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

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

CONCENTRATING COLLECTORS - CCSTaR Universitat de les Illes Ballears

Process Heat Collectors CPC Collector Concentration: 1,8x Efficiency n 1.00 0.90 0.80 0.70 0.60 0.50 0.40 0.30 0.20 0.10 0.00 Air 1 bar Air 0,01 bar Krypton 0,01bar 0 20 40 60 80 100 120 140 Temperature difference T_Coll_mid - T_Amb [K] LoCo EvaCo (Low concentrating evacuated flat collector), ZAE Bayern

COLLECTOR MATERIALS?

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

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

ABSORBER COATING Source:Alanod-Sunselect / ESTIF

TRANSPARENT COVER MATERIALS cover thickness [mm] weight [kg/m²] solar transmittance Standard glass *) 4 10 0.84 Standard glass, tempered 4 10 0.84 Iron free glass, tempered 4 10 0.91 Antireflective coated glass 4 10 0.95 PMMA, ducted plate 16 5.0 0.77 PMMA, double ducted plate 16 5.6 0.72 *) danger of breaking determined by high collector temperatures

Collector test

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

TRANSPARENT COVER MATERIALS Solar glass Solar glass with antireflective coating

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

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

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

INSULATING MATERIALS insulating material max. allowable temperature [ ] density [kg/m³] conductivity [W/mK] at 20 C Mineral wool > 200 60-200 0.040 Glass wool > 200 30-100 0.040 Glass wool > 200 130-150 0.048 Polyurethane foam < 130 30-80 0.030 Polystyrol foam < 80 30-50 0.034

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,..),..

FLAT-PLATE COLLECTOR Simple Design Modul Collector Roof Integrated Collector

FLAT-PLATE COLLECTOR Advanced Design Module Collector Roof Integrated Collector

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

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

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.

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

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

Collector Efficiency s. T-Sol Collector data

Collector efficiency curve 0,8 Optical Losses 0,7 eta 0,6 0,5 0,4 Thermal Losses 0,3 Useful Energy 0,2 0,1 0 0 0,04 0,08 0,12 0,16 (TKm-TA) / GT [Km²/W] Stagnation Point

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]

Area Definitions Apertur area

Possible Improvements of FPC on aperture are efficiency (based 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Hermetically sealed collectors with inert gas fillings; operating temperature Double covered flat-plate collectors; 80 120 C Vacuum flat-plate collectors; and combinations of the above mentioned 1 AR 2 AR 3 AR standard flat-plate collector 0 0.05 0.1 0.15 (T m -T a )/G in Km²/W Source: IEA SHC Task 33

Flat plate collectors?

Flat plate collectors 12 m²

Hydraulic connection of collectors