**2. Aims and Methodology**

This paper investigates the aesthetic and technological integration of hidden coloured PV modules in architecturally sensitive areas. In these areas, there is an increasing debate on the possible integration of PV systems, respecting heritage constraints as well as preserving historic and natural values. Coloured BIPV modules seem the best possibility to favour a balance between conservation and energy issues (Section 4.1). In parallel, these technologies have shown a relatively recent market growth, and their applications are significantly increasing due to their flexibility. Therefore, there is an urgen<sup>t</sup> need to better understand the overall technical performance of these promising products against the real requirements of the built environment, with the purpose of providing better modelling of their behaviour and fostering energy flexibility in buildings [22,23]. Despite the high technological readiness level (TRL) of BIPV systems, it is essential to further investigate their performance and reliability in operational environment to increase the users' trust and boost its market penetration.

One aspect related to the novelty of this research concerns the interdisciplinarity between aesthetic and technical aspects. The first one refers mainly to the work of conservators, designers, heritage and public authorities that need clear criteria for the methodological assessment of BIPV systems in architecturally sensitive areas. The second one refers to engineers, manufactures, supplies, installers and power utilities that need clear data from BIPV experimental assessment. For this reason, the paper is divided in two parts. First, a multidisciplinary methodology for evaluating the aesthetic and technical integration of PV systems in architecturally sensitive area is proposed, referring to the most promising technology (Sections 3 and 4). More precisely, in Section 3, the key concept of integration is discussed, with particular focus on the international guidelines for the application of BIPV in architecturally sensitive areas, which has been crucial to identifying the criteria for ensuring the aesthetic integration of BIPV technologies (Section 3.1). Then, once recognising that the visual integration is fundamental for broader BIPV deployment, and in particular that the geometrical uniformity and the colour of the cells play a key role in this respect, the analysis focuses on the state of the art of the existing technologies for hidden coloured PV modules. To this purpose, a deep technical review of the BIPV technological solutions available on the market is realised (Section 4). On these bases, an evaluation matrix has been developed with the aim of steering the market analysis required to choose the technologies to be tested within the project (Section 4.1). This evaluation process has been used to identify a set of di fferent coloured BIPV technologies for their experimental characterisation. Second, the experimental characterisation of the technical performance specific BIPV modules and their comparison with standard modules under standard weather condition are analysed, with the aim of acquiring useful data for comparing the modules' integration properties and performance (Section 5). To this purpose, a new facility specifically developed for BIPV system has been set up for investigating the aesthetic integration and the energy performances of innovative PV products, focusing on the three integration concepts: (i) technology (i.e., innovative integration substructures); (ii) aesthetic (i.e., appealing PV modules); and (iii) energy integration (i.e., plug and play concepts). The description of the experimental facilities is provided in Section 5.1.1 (outdoor testbeds) and Section 5.1.2 (indoor laboratory). In Section 5.2, the indoor experimental results are presented, while the experimental design of the outdoor testbeds and the first qualitative results of the experimental camping is provided in Section 5.3. Finally, Section 6 presents the conclusions and lesson learnt. These facilities also allow to tackle specific challenges of BIPV to develop better and more performing systems, as well as to show among all the stakeholders involved in the value chain (i.e., manufactures, designers, supplies, installers, national public authorities, local planning authorities, power utilities, owners, final users and financial bodies) the benefits o ffered by these innovative BIPV panels.

This work has been made in the framework of the research project *BIPV UPpeal* that aims at accelerating BIPV market penetration by showing to the main stakeholders the benefit of integrating PV systems in architecturally sensitive areas. This permits to concretely show the new aesthetic and technical possibilities of BIPV systems (e.g., with testbeds, case studies and databases) but also to create a network among the professionals. Otherwise, innovative coloured BIPV technologies are selected to be tested in these testbeds following the evaluation criteria defined in the framework of the EU project *BIPV meets history* that aims at creating a value chain for the use of BIPV in heritages, according to the international guidelines and ad hoc working tables [19].
