Experimental evaluation of the reliability of the adhesive joint in a 3rd-generation-solar-cell-integrated glass block

Glass block is a building product that has been widely used since the mid-1800s for the construction of natural light capturing technical elements and, in the last decades, of translucent building envelopes. In a framework of increased quality requirements in terms of energy saving and environmental sustainability, innovations have been introduced to its standard configuration, including the integration of 3rd generation solar cells within the glass block, in order to improve its performance and make it capable of producing clean energy. Indeed, one of the two constituting glass shells has been integrated with a pre-assembled photovoltaic module and then bonded to a plastic “thermal belt” allowing the assembly with the other shell. These patented technological innovations are being prototyped by SBskin. Smart Building Skin s.r.l., academic spin-off of the University of Palermo, and need to be verified in terms of the durability of the product as a whole and of its sub-components, according to EU Regulation 305:2011. The aim of this paper is to explain the methodological approach of the study and the first results of the tests carried out to evaluate some of the durability requirements: inherent and critical reliability. After developing the test program to evaluate the possible dimensional variations of the glass block and its sub-components due to temperature and/or relative humidity variations and possible chemical-physical incompatibilities between the materials constituting the system, the experimental assessment of the behaviour of the different materials constituting the thermal belt and of the various types of sealants was carried out. For each type of material and sealant, the determination of tensile lap-shear strength of rigid-to-rigid bonded assemblies was carried out in accordance with ISO 4587:2003. The samples were subjected to the aging protocol of ASTM C 719-93:2005, based on pre-treatment phase in the climatic chamber and UV radiation tests in Solarbox. The first test results demonstrate that the best response is provided by the polypropylene compound mixed with mica solution. Further tests are in progress to evaluate the behaviour of other materials in order to characterize the bonding between the shells and the thermal belt.