Use of photovoltaic modules as static solar shadings: Retrofit of a paleontological site in Rome.

The study aims at testing an innovative methodology and workflow for the design of a BIPV (Building Integrated PhotoVoltaics) system. The technology consists in using standard “off the shelf” photovoltaic modules as static shadings. The solution can reduce the occurrence of excess heat in a prefabricated building presenting a huge glass façade on the southern side. The PV modules are set as an array of blades along the glazed façade and the optimization involves the tilt angle and distance between arrays in a parametric design environment. Once the COMBO (Combination Optimized to Meet Building Objectives), defined as the optimal distance between blades and their tilt angle, is found, the impact on the indoor climate is provided by using a whole-building dynamic simulation software. The case study is the paleontological deposit of “La Polledrara di Cecanibbio” located at NW of Rome (Italy) in a rural area. The building model is calibrated using hourly indoor temperature measured on-site. The methodology features two main innovations which improve speed and versatility. The optimization method does not require to run simulation for each parametric combination because it is based on the incoming irradiation on the glazed surface, greatly boosting the speed of the optimization. Given the ideal load profile provided by the simulation of building model, the algorithm searches a COMBO to minimize the solar irradiation during cooling hours and to maximize it during heating hours. The versatility of methodology relies on a ray-tracing procedure (using Radiance based Daysim) to generate the hourly irradiation profiles on the glass. The computational resources required by ray-tracing do not increase much for complex geometries and are therefore a good candidate for BIPV simulation applications. The results on the indoor climate after the proposed refurbishment, considering both thermal comfort of people and conservation in situ of paleontological remains, are shown and discussed.