Building integrated Concentrating Photovoltaic/Thermal Glazing (COPVTG) systems: experimental campaign and dynamic simulation tool validation

The present paper investigates the electric and thermal performance of an innovative Concentrating Photovoltaic/Thermal Glazing (CoPVTG) system, developed and experimentally evaluated at the Centre for Sustainable Technologies of the University of Ulster (Belfast, UK). The novel smart window is purposely designed to be compatible with traditional façade structures and fenestration framing arrangements, facilitating direct integration into new and retrofit building applications. The device is made of a double-glazing panel whose outside pane is shaped into a series of concentrating lenses in which optical focus several PV cell stripes are located. The glazed concentrating elements are accurately designed to allow the sunlight to enter the building and provide natural daylight when required (winter months) while redirecting it onto the photovoltaic thermal absorbers to generate electricity/heat when solar gains need to be minimised to reduce cooling demands (summer months). Also, aiming at reducing the PV cells' temperature (and thus increasing the PV electric efficiency), a heat recovery system, based on a forced air flux, is adopted. Specifically, two slots, on the lower and upper frames of the window, are made to allow the air to pass through the device. In such a way, the produced hot air can be used for different aims such as space heating or pre-heating purposes, depending on the reached temperature. As a result, the innovative window delivers solar-generated electricity and thermal energy while also reducing the building heat losses (higher U-value with respect to standard windows). Aiming at investigating the innovative device performance under diverse boundary and working conditions, a suitable dynamic simulation tool has been developed in MATLAB environment. Employing the developed dynamic simulation tool, the innovative CoPVTG device performance has been investigated. In addition, two modifications of the original device have been also studied: the CoPVG and the CoPEG. From the carried-out investigations, promising results have been obtained