PV in glazed facades Thermal indoor climate Søren Østergaard Jensen Industry and Energy...
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Transcript of PV in glazed facades Thermal indoor climate Søren Østergaard Jensen Industry and Energy...
PV in glazed facadesThermal indoor climate
Søren Østergaard JensenIndustry and EnergyTeknologisk Institut
PV in glazed facades
First some theory
2 and 3 D heat losses
directly transmitted solar radiation
absorption
convection
long wave radiation
infiltrationconduction
reflection
Simple theory
heat loss – U-value [W/m2K]
directly transmitted light and solar energy
indirectly transmitted solar energy
absorbedsolar energyreflected
solar energy
solar radiation
transmittance for light – τ-value incoming solar energy – g-value heat loss – U-value
Parameters in the simple theory
PV-cells have impact on the g-value PV-cells haven’t impact on the U-value the U-value has impact on the g-value
Parameters in the simple theory
1 pane of clear glass 0.85 2 panes of clear glass 0.75 3 panes of clear glass 0.65 2 panes clear glass with low-e coating 0.60-0.65 Windows with solar screening 0.25-0.50
Examples of g-values
g-value
The PV cells are mounted in the external pane of a low-e window with Argon between the two glass
Product opening g-value light trans- area mittance Würth WSS0007 8% 0.13 0.06 Würth WSS0008 21% 0.19 0.15 Würth WSS0009 22% 0.20 0.16 MSK / Suntech MST-44T101OU 10% 0.13 0.07 MSK / Suntech MST-50T051OU 4% 0.11 0.04 Interpane – reference panel 31% 0.23 0.22
U-value: 1.2 W/m2K
Windows with PV-cells
The PV cells are mounted in the external pane of a traditional window with air between the two glass
Product opening g-value light trans- area mittance Würth WSS0007 8% 0.23 0.07 Würth WSS0008 21% 0.30 0.16 Würth WSS0009 22% 0.30 0.17 MSK / Suntech MST-44T101OU 10% 0.23 0.07 MSK / Suntech MST-50T051OU 4% 0.20 0.04 Interpane – reference panel 31% 0.34 0.23
U-value: 2.8 W/m2K
Windows with PV-cells
Example: small office building
Heated floor area: 650 m2
Window area: 31 % of heated floor area
Influence of the g-værdi
0
10
20
30
40
50
60
70
80
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
g-værdi
ener
gy
dem
and
[kW
h/m
2]
0
50
100
150
200
250
300
350
400
ho
urs
cooling demand
heating demand
number of hours above 26 C
Influence of the U-værdi
0
20
40
60
80
100
120
0.5 1 1.5 2 2.5 3 3.5
U-værdi
ener
gy
dem
and
[kW
h/m
2]
0
50
100
150
200
250
300
350
400
450
ho
urs
cooling demand
heating demand
number of hours above 26 C
Cold down fall
U-valueWindow: 1,5 W/m²KWall: 0,2-0,4 W/m²K
”Cold down fall”
Solar shading
Solar shading
g-valueNu 0.17Suncool 0.32Float 0.65
PowerShades