thermal aspects of photovoltaic/thermal solar collectors
DESCRIPTION
Thermal Aspects of Photovoltaic/Thermal Solar Collectors. Tim Anderson Deparment of Engineering University of Waikato. Solar Energy and NZ. New Zealand land mass conservatively collects 1.4x10 21 J per year - PowerPoint PPT PresentationTRANSCRIPT
Thermal Aspects ofPhotovoltaic/Thermal Solar
Collectors
Tim Anderson
Deparment of Engineering
University of Waikato
Solar Energy and NZSolar Energy and NZ
New Zealand land mass conservatively collects 1.4x1021 J per year
An average house rooftop of 150m2
collects 2.2x108 Wh per year ie. 20 to 30 times the house’s total requirements.
Hamilton receives ~5000 MJ/m2/year
Existing Solar Technologies
Solar Thermal Photovoltaics
Source: www.solahart.com.au Source: www.bpsolar.com
What is a Photovoltaic/Thermal Solar Collector
Solar Thermal + Photovoltaics = PVT
+ =
PVT Collectors
Photovoltaic and solar thermal in a single device: Cogeneration of heat and power
PV-cell efficiency decreases with increasing temperature
Efficiency of PV cells increased by active cooling
Area dedicated to solar energy devices can be reduced
PVT Air Heating
Simple Cheap Cavity formed behind a PV panel Provides reasonable air heatingProvides reasonable air heating
Insulation
PV Module
Air
PVT Water Heating Systems
Could look very similar to a “standard” solar thermal collector
Simple Typically better efficiencies than air heating Suitable for heating over wide range of temperatures
Cover
Insulation
Water Tube
PV Module
Market for PVT Systems
Solar thermal collector market in Australia and New Zealand was growing at a rate of 19% per annum
Market for photovoltaic solar collectors has experienced a very high rate of growth during the last decade
PVT systems could meet the entire European PV quota while also providing 30% of the solar thermal target
Largest market is the domestic sector
Short to medium term PVT will find “niche market” applications
Source:International Energy Agency (Photovoltaic Power Systems Programme), 2005, Trends in
Photovoltaic Applications - Survey report of selected IEA countries between 1992 and 2004, Report
IEA-PVPS T1-14:2005
University of Waikato PVT Research
University of Waikato is conducting research into Building Integrated Photovoltaic/Thermal (BIPVT) collectors
BIPVT is the use of PVT as building elements such as roofing or façade
Compromise between thermal, electrical and building needs
Thermal and electrical performance of a typical BIPVT collector has been modelled, using a modified Hottel-Whillier method (i.e. as a standard flat plate solar collector)
BIPVT Implementation
Unglazed BIPVTUnglazed BIPVT Glazed BIPVTGlazed BIPVT Standard roofing profileStandard roofing profile Standard roofing materialsStandard roofing materials
BIPVT Unglazed
BIPVT Unglazed
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08(Tin-Ta)/G"
The
rmal
Effi
cien
cy
1m/s
2m/s
4m/s
8m/s
BIPVT Cooling Passage Width
BIPVT Cooling Passage Width
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
(Tin-Ta)/G"
The
rmal
Effi
cien
cy
20mm wide
50mm wide
100mm wide
150mm wide
BIPVT Flowrate
BIPVT Flowrate
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08(Tin-Ta)/G"
The
rmal
Effi
cien
cy
10L/s
6L/s
4L/s
2L/s
BIPVT Material
BIPVT Material
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08(Tin-Ta)/G"
The
rmal
Eff
icie
ncy
Steel
Aluminium
Copper
Stainless Steel
BIPVT Packing Factor
BIPVT Packing Factor
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
(Tin-Ta)/G"
The
rmal
Effi
cien
cy
20%
40%
60%
80%
100%
BIPVT Cell to Absorber HTC
BIPVT Cell to Absorber HTC
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08(Tin-Ta)/G"
The
rmal
Effi
cien
cy
45
90
135
180
BIPVT Transmittance-Absorptance Product
BIPVT Transmittance-Absorptance Product
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
(Tin-Ta)/G"
The
rmal
Effi
cien
cy
0.86
0.82
0.78
0.74
BIPVT Insulation Thickness
BIPVT Insulation Thickness
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08(Tin-Ta)/G"
The
rmal
Eff
icie
ncy
100mm of static air
100mm
70mm
40mm
10mm
What does it all mean?
TMY can be used for long term simulation TMY can be used for long term simulation of solar energy devices such as PVTof solar energy devices such as PVT
PVT modelling used for design PVT modelling used for design modifications – empirical validation in modifications – empirical validation in progressprogress
Modelling shows that to improve the Modelling shows that to improve the BIPVT collector we could: use less PV BIPVT collector we could: use less PV cells, try to improve PV cell optical cells, try to improve PV cell optical efficiency, reduce insulationefficiency, reduce insulation
Where to from here?
Long term modelling of BIPVTLong term modelling of BIPVT Empirical validation of design modelEmpirical validation of design model Develop correlation to predict heat loss Develop correlation to predict heat loss
from BIPVT due to natural convection in from BIPVT due to natural convection in attic space behind collector (Experimental attic space behind collector (Experimental and CFD)and CFD)