**6. Conclusions**

This paper outlines the research activities carried out to define the configuration of new testbeds for the experimental characterisation of coloured BIPV technologies. The investigation of BIPV technology is an interdisciplinary activity that calls for heterogeneous expertise, having the BIPV modules multifunctional features related to the aesthetic and technological integration in building envelope and to energy integration both in the building systems and in the electric grid. Being BIPV applications tailored on the building envelopes, the modules and the mounting systems require a specific design. This high level of customisation constitutes the strength and the uniqueness of BIPV products but also a limit, since it hinders the series production of the modules and, thus, it limits their cost reduction. Furthermore, the customisation of coloured BIPV modules that completely hide the PV cells from the view and their expansion on the market would contribute in enhancing the social acceptance of PV in sensitive areas, where the PV technologies have been often considered anaesthetic, and thus unacceptable, by users and architects. Therefore, there is the need to overcome the technical, social and economic barriers to reach a larger scale of BIPV applications and thus improve their economic profitability. The first issue to deal with is the definition of the concept of *integration*, which needs to find a unique expression within BIPV literature and standards. The definition of the criteria that set the application of BIPV in architecturally sensitive areas need especially to be revised. In fact, the existing guidelines refer mainly to PV systems applied on the building envelope (BAPV), without considering the actual potential of the modern coloured BIPV technologies that can "disappear" from the view. Secondly, it is important to better investigate the wide range of available technologies for coloured BIPV, with regards to the electrical behaviour of a large variety of coloured modules. This variety results in a fragmented market scenario where several customisation options are now available. Nonetheless, the customisation process could lead to modifications in the electrical behaviour of the module, due to the presence of one or more coloured layers which cause the reflection or absorption of a portion of the solar spectrum (in the visible range) that would otherwise be converted into electricity, causing a reduction in the modules' yield.

Therefore, to deeply investigate this behaviour, experimental assessment is needed both at STC and under real operating conditions on final assembled BIPV modules. For this reason, we selected two BIPV modules to be tested in EURAC Research's indoor and outdoor facilities. Indoor tests are already completed with satisfactory results and will support outdoor experiment analysis. Besides the technical assessment, real scale BIPV testbeds are useful to test different solution for the mounting systems and to understand the risks related to the installation of BIPV modules. Testbeds are also important because they could show different stakeholders the new and concrete aesthetic and technical possibilities of BIPV systems, improving the users' trust on aesthetic integration, the market penetration and the economic profitability. In fact, BIPV products could sensibly expand the envelope surfaces available for PV installation. As a result, BIPV could lead to a shift in the energy paradigm for buildings that would no longer be a mere energy consumer in the local electric grid, but could indeed provide load flexibility by producing, storing and selling electricity to the grid according to mutual needs. To achieve the objectives of deeper market penetration and higher economic profitability of BIPV applications, further test activities will be carried out in these facilities. In fact, several BIPV systems (including PV modules, substructures and energy systems) will be integrated in both the outdoor roof and façade testbed, with the aim of testing and comparing them with respect to the three integration aspects of aesthetic, technology and energy, since all these aspects are of fundamental importance to enhance the application of BIPV technologies in the built environment.

**Author Contributions:** Conceptualisation, M.P., E.L. and L.M.; methodology, M.P.; investigation, M.P., E.L., L.M. and A.A.; resources, M.P. and M.L.; writing—original draft preparation, M.P. and E.L.; writing—review and editing, M.P., E.L., L.M., A.A. and F.C.; visualisation, M.P.; and project administration, L.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research leading to these results received funding from the Institute for Renewable Energy of Eurac Research, within the project "*BIPV UPpeal*". In addition, this research was co-financed by the European Union, European Regional Development Fund, the Italian Government, the Swiss Confederation and Cantons, as part of the Interreg V-A Italy-Switzerland Cooperation Program, within the context of the "*BIPV meets History*! project (grant No. 603882), for the definition of criteria and products for BIPV integration in architecturally sensitive areas. Furthermore, the research received funding from the Program EFRE/FESR Provincia autonoma di Bolzano-Alto Adige 2014–2020, under Project number FESR1042, "*Studio dell'integrazione di reti elettriche e termiche con la flessibilità energetica degli edifici–INTEGRIDS*", for the purchasing of the inverter, connection and distribution boxes. Finally, it has received funding from the Program EFRE/FESR Provincia autonoma di Bolzano-Alto Adige 2014–2020, under Project number FESR1128, "Use of Industry 4.0 and Internet of Things logics in the photovoltaic sector—PV 4.0", for the purchasing of PT100 temperature sensors.

**Acknowledgments:** We acknowledge David Moser and Alexandra Troi for the revision and the useful suggestions on the paper structure; Gazmend Luzi for the data provided on PV cells; and Ilaria Alberti for the revision of English text.

**Conflicts of Interest:** The authors declare no conflict of interest.
