PV in glazed facades Thermal indoor climate Søren Østergaard Jensen Industry and Energy Teknologisk Institut

PV in glazed facades

First some theory 2 and 3 D heat losses directly transmitted solar radiation absorption convection long wave radiation infiltration conduction reflection

Simple theory heat loss – U-value [W/m 2 K] directly transmitted light and solar energy indirectly transmitted solar energy absorbed solar energy reflected solar energy solar radiation

n transmittance for light – τ-value n incoming solar energy – g-value n heat loss – U-value Parameters in the simple theory

n PV-cells have impact on the g-value n PV-cells haven’t impact on the U-value n the U-value has impact on the g-value Parameters in the simple theory

n 1 pane of clear glass 0.85 n 2 panes of clear glass 0.75 n 3 panes of clear glass 0.65 n 2 panes clear glass with low-e coating n Windows with solar screening Examples of g-values g-value

n The PV cells are mounted in the external pane of a low-e n window with Argon between the two glass n Product opening g-value light trans- n area mittance n Würth WSS0007 8% n Würth WSS % n Würth WSS % n MSK / Suntech MST-44T101OU10% n MSK / Suntech MST-50T051OU 4% n Interpane – reference panel31% n U-value: 1.2 W/m 2 K Windows with PV-cells

n The PV cells are mounted in the external pane of a traditional n window with air between the two glass n Product opening g-value light trans- n area mittance n Würth WSS0007 8% n Würth WSS % n Würth WSS % n MSK / Suntech MST-44T101OU10% n MSK / Suntech MST-50T051OU 4% n Interpane – reference panel31% n U-value: 2.8 W/m 2 K Windows with PV-cells

Example: small office building Heated floor area: 650 m 2 Window area: 31 % of heated floor area

Cold down fall

U-value Window: 1,5 W/m²K Wall: 0,2-0,4 W/m²K ”Cold down fall”

Solar shading

g-value Nu 0.17 Suncool 0.32 Float 0.65

PowerShades