Abstract
The European legislative framework asks for massive application of renewable energy source (particularly of photovoltaic systems) in the built environment to face the recent energy crisis, reducing energy demand, environmental emissions, and costs. These policies could generate serious preservations problems for architecturally sensitive areas, such as historical towns, historic buildings, and protected landscapes. Inside them, photovoltaic technologies have several benefits for the built environment related to aesthetic appeal, reliability, modularity, scalability, versatility, low maintenance costs, and peak shaving. The major challenge for their application is the presumed negative impact on heritage value. Thus, the diffusion of these systems in the territory is hindered by a social diffidence on their acceptability due to legislative, cultural, technical, and economic barriers. To support the definition of appropriate policies, and realistic targets, the study presents a complete discussion on policy-related design criteria for integrating photovoltaic systems on cultural heritage. This socio-technical analysis can increase a cleaner and integrated energy production, favoring the energy transition and the mitigation of climate changes, respecting heritage and natural values, and considering current energy needs, and innovative developments of photovoltaic systems. The comparison of relevant research projects, scientific studies, awards, and guidelines describes the state of the art of this topic, also identifying 42 international guidelines on energy efficiency, renewable sources, and solar integration on cultural heritage. International recommendations are categorized to find recurring, and applied design criteria for architectural heritage sites, protected landscapes, historic and traditional buildings, and building extensions. Then, updated criteria, pros, and cons for a possible integration are defined through specific focus groups with the Heritage Authorities. These activities are based on international criteria of architectural conservation. The synopsis of these results shows non-negotiable criteria for heritage-compatible solar applications. Finally, the study presents some policy-relevant implications connected with these design criteria, to define realistic energy targets and scenarios, to prepare strategic policy options (e.g., guidelines, rules, policies, and financial incentives) based on updated criteria, correct targets, and recent innovations, to implement existing energy policies in a correct way, to correctly assess restoration design projects, and to evaluate socio-economic trends of innovative photovoltaics' markets.