Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE credits
PVT collectors are more and more in focus as they combine electricity generation and generation of heat in one single collector. In this thesis a thin film CIGS PV module is used to replace a conventional solar absorber and create an air ventilated PVT collector. The thesis includes the design and construction of the collector, measurement of important performance parameters as well as analysis of the collected data in terms of thermal and electrical performance.
A Solibro CIGS PV module is used as solar absorber and a wooden box is constructed around the module. An electric fan is used to control air flow behind the PV module. Inlet and outlet air temperatures of the collector are measured as well as the temperatures of the backside of the PV module and the opposite wall in the air channel and logged together with irradiance level every ten seconds during a period of one week.
During the measurement period with clear sky conditions quite constant irradiance levels can be measured resulting in a temperature increase between inlet and outlet air temperature of 22 °C. PV module temperatures reached values up to 60 °C while the outlet temperature reached 45 °C. Thermal power reached values above 300 W/m² and efficiency was calculated to 0.33 for high periods with high irradiance (900 W/m).
Infrared images of the collector show that the heat distribution on the PV module was quite uniform which means that also air flow behind the module can be considered uniformly distributed. Only a small area around the air inlet showed slightly lower temperature levels compared to the opposite side at the same level.
Electrical performance was analyzed theoretically by comparing output levels under conditions of forced ventilation and with natural ventilation. The temperature difference achieved by the cooling effect on the module by the forced airflow accounted for an increase of about 6 % of power output. In absolute numbers however the needed power for the fan is higher compared to the gain in electricity output from the 100 Wp PV module.
It can be seen that measured outlet temperatures were slightly delayed compared to corresponding irradiance levels and the temperature changes are less fluctuating thus smoothened compared to the fast changing irradiance values. Pressure drop in the collector is a limiting factor that requires a minimum air gap diameter for a certain airflow.
Using a CIGS PV module is a suitable option to replace a conventional absorber in a solar collector if the benefit from the produced electricity is of use and maximum thermal output is not the major concern. To achieve higher temperatures air flow needs to be decreased which will have a negative impact on the total electricity output.
In terms of using such a collector for solar drying it depends on the prevailing climate conditions if desired temperature levels can be reached. The electricity produced by the PV module could directly be used to power an electric fan and in a further step could open for the option to control air flow and air temperature into the drying chamber.