| Work Detail |
A team of UK researchers has developed a new design technique for photovoltaic thermal air collectors. The new parameters make it possible to obtain devices with lower photovoltaic module temperatures and higher efficiencies.
A group of researchers led by the University of Exeter (United Kingdom) has devised new design parameters for photovoltaic-thermal (PVT) air collectors taking into account the effect of modifying the depth and velocity of the duct.
PVT air collectors use air as a transfer medium to take heat from the back of the PV panel unit. Compared to FVT water collectors, these devices are cheaper to produce and maintain and, in theory, can be used in any climate. Its performance, however, depends on design elements such as the technology of the photovoltaic modules, the internal structures of the heat collecting space or the shape of the air duct, among others.
The scientists explained that the depth of the duct has a significant effect on the performance of PVT air collectors, as it directly influences the airflow behavior. “As the depth of the duct increases, the temperature of the photovoltaic cells increases,” they stated. “Duct depth has a negative relationship with duct velocity. “Due to this, the heat transfer coefficient depreciates, which limits the heat extraction of the photovoltaic cells.”
Using computational fluid dynamics (CFD) methods, the research group studied the performance of an air-based FVT system, which included two 75 W PV modules with a 0.05 m deep air duct, and compared it with that of a reference system without the air duct.
“The photovoltaic module consists of five layers: a glass/tedlar bottom, two layers of EVA, a layer of photovoltaic cells and a glass cover,” explain the researchers, noting that each module contains 36 solar cells. “The glass cover has a transmissivity of 0.95, which maximizes the amount of solar radiation that can pass through it to reach the photovoltaic cells, while also providing some protection to the panel.”
Through their analysis, the researchers discovered that the air duct “greatly” reduces the temperature of the photovoltaic panel, specifically the temperature of the photovoltaic module without the duct was 77.9ºC, while that of the panel with the duct It was only 53.3 ºC. “The air flowing under the panels extracts the heat generated by the cells,” they explained. “This led to a 13.67% increase in electrical efficiency, highlighting the impact of the air duct.”
The new design methodology is described in the study “ Performance evaluation of a solar photovoltaic-thermal (PV/T) air collector system ”, published in Energy Conversion and Management : “This work has provided high-quality simulation results to develop design parameters and improve efficiency, as this was identified as a gap in the literature initially,” the scientists said.
Researchers from the Technical University of Liberec (Czech Republic) also participated in the research group. |
