Modeling the Energy Yield of The PowerWindow

Abstract

The European Union has established two directives that require both public and private buildings to become
nearly zero energy by 2020. This has increased public interest in and development of building integrated
photovoltiac (BIPV) systems. One such BIPV solution is the PowerWindow by Physee. Even though the PowerWindow
does not produce asmuch power as a traditional rooftop installed photovoltaic solution, it can still
be viewed as a step in the right direction to achieve sustainable development.
This thesis project aims at modelling the energy yield of the PowerWindow by developing a simple framework
with optical, thermal and electrical models. This thesis also evaluates the electrical characteristics of the
PowerWindow under solar simulators. Furthermore, opto-electronic parameter values like current, voltage,
reflectance and so on found through experimentation are used as input to the models. The optical model
deals with a ray tracing approach to find the incident irradiance on the solar cells inside the PowerWindow.
This incident irradiance along with the weather data is used for the development of a thermal model to predict
the temperature of the solar cells using a fluid dynamic approach. To model the electrical characteristics
of the PowerWindow, a one diode equivalent circuit is used. However, the current source is modified to incorporate
the effects of inhomogeneous irradiation on and the temperature of the solar cells.
The results of this work show that the maximum power produced by the PowerWindow, currently manufactured
by Physee, is approximately 3.5 W under a solar simulator. This work also compares the incident
irradiation profiles of all the edges of the PowerWindow, which produce power on different days, orientations
and locations. The effects of shading on the PowerWindow is evaluated in terms of irradiation and is found
to be present only in the summer months in Eindhoven. Furthermore, the daily energy yield calculated for
a typical summer, winter and overcast day in Eindhoven is found to be 13, 5 and 3 Wh. It was concluded
that a west and east facing PowerWindows in Eindhoven produce more energy in the summer and less in
the winter as compared to a south facing PowerWindow. Additionally, the most performance effective circuit
configuration is found to be the one with both blocking and bypass diodes.