Study of a BIPV adaptive system combining timber and photovoltaic technologies

The reduction in building energy consumption and CO2 emissions is one of the main goals in the nearly Zero Energy Buildings (nZEB) framework. In this regard, adaptive technologies and materials represent a constantly developing sector and source of innovation. Moreover, these systems are often aimed at collect and convert renewable energy (mainly solar) in order to cover as much as possible the building energy consumption. In this context, the research goal has been the design of a BIPV (Building Integrated PhotoVoltaic) facade system able to change its curvature in relation to the external environmental conditions, orientating itself in order to optimize the energy production without the aid of any mechanical and electrical system. The following aspects have been considered: passive dynamism, lightness, weather resistance, easy maintenance, applicability on a large scale, easy integration in the building envelope, Life Cycle sustainability. The adaptive layer consists of two wooden sheets, one active and one passive, joined together. The response of a hydromorphic material is a function of ΔMC’ (effective moisture content change), that is, the difference in the moisture content in the wood, which in turn depends on the air temperature and Relative Humidity (RH) and it varies in relation to the wood species. Moreover, this response is a function of the dimensional variations of the two wooden layers used to produce the composite self-adjusting flake. The variation in outdoor air RH activates the movement of the wooden flakes, that can therefore change their curvature thanks to the different expansion coefficients of the two wooden slats. To evaluate the performance of the component, three shape configurations for the adaptive flakes have been assumed. For each hypothesis, the flakes have been modelled using the Rhinoceros 5 Software, according to the curvatures taken during the different months of the year. The Rhino models have been imported into Autodesk Ecotect Analysis to calculate the incident solar radiation and to study the self-shadowing effect in the various configurations (considering the climatic conditions of the city of Milano).