Thermal Analysis of Naturally Ventilated BIPV systems
Date Issued
November 2017
Author(s)
Advisor
Abstract
The aim of this study is to investigate the thermal behaviour of naturally ventilated BIPV systems. This
study focuses on the systems with natural ventilation because it is believed that there is a good
potential to improve their performance with design configurations, in order to provide sufficient
ventilation to circulate the air and avoid the use of a fan with extra cost, noise and maintenance
requirements. The ultimate goal is to estimate the convective heat transfer coefficients in all sections
of a BIPV system.
An extensive experimental analysis is carried out in outdoor environmental conditions and in indoor
controlled conditions with the use of a solar simulator. It was pointed out that the air exits the duct at
around 10ºC hotter than it enters and for this reason the PV’s temperature increases from the bottom
to the top. Regarding the inclination angles tested, it is observed that the system develops higher
temperature when is inclined at 30º and less when is placed vertically (90º). Subsequently, an analysis
of the natural convection is carried out using fundamental convection equations and as a result, two
correlations for the estimation of the convective heat transfer coefficients (CHTC) are extracted for the
first time. These can be applied to estimate the CHTC in the air gap between the PV panels and the
outer skin of the building, in double skin BIPV systems, for windy and no windy conditions. Afterwards,
a 3D computational fluid dynamic (CFD) model was built in COMSOL Multiphysics and it is validated
with the experimental results. The general conclusion is that the experimental results were in a good
agreement with the simulation results.
Additionally, based on the measured temperature distribution of the system from the experimental
procedures, energy and exergy analyses are carried out and the correlations for the estimation of the
energy and exergy efficiencies are presented for the first time for a naturally ventilated BIPV system.
The energy efficiency of the system is estimated to be up to 26.5‐33.5% while the exergy efficiency is
estimated to be between 13‐16%.
Finally, the gained knowledge is applied to a real BIPV demonstration system. A building simulation
model is carried out to predict the temperature of the PV panels and the energy production of the
system for one year. A good agreement is observed between the calculated and measured data.
study focuses on the systems with natural ventilation because it is believed that there is a good
potential to improve their performance with design configurations, in order to provide sufficient
ventilation to circulate the air and avoid the use of a fan with extra cost, noise and maintenance
requirements. The ultimate goal is to estimate the convective heat transfer coefficients in all sections
of a BIPV system.
An extensive experimental analysis is carried out in outdoor environmental conditions and in indoor
controlled conditions with the use of a solar simulator. It was pointed out that the air exits the duct at
around 10ºC hotter than it enters and for this reason the PV’s temperature increases from the bottom
to the top. Regarding the inclination angles tested, it is observed that the system develops higher
temperature when is inclined at 30º and less when is placed vertically (90º). Subsequently, an analysis
of the natural convection is carried out using fundamental convection equations and as a result, two
correlations for the estimation of the convective heat transfer coefficients (CHTC) are extracted for the
first time. These can be applied to estimate the CHTC in the air gap between the PV panels and the
outer skin of the building, in double skin BIPV systems, for windy and no windy conditions. Afterwards,
a 3D computational fluid dynamic (CFD) model was built in COMSOL Multiphysics and it is validated
with the experimental results. The general conclusion is that the experimental results were in a good
agreement with the simulation results.
Additionally, based on the measured temperature distribution of the system from the experimental
procedures, energy and exergy analyses are carried out and the correlations for the estimation of the
energy and exergy efficiencies are presented for the first time for a naturally ventilated BIPV system.
The energy efficiency of the system is estimated to be up to 26.5‐33.5% while the exergy efficiency is
estimated to be between 13‐16%.
Finally, the gained knowledge is applied to a real BIPV demonstration system. A building simulation
model is carried out to predict the temperature of the PV panels and the energy production of the
system for one year. A good agreement is observed between the calculated and measured data.
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