A numerical study of adaptive building enclosure systems using solid-solid phase change materials with variable transparency

Buildings currently consume about 40% of all energy use in the US and therefore play an important role in mitigating global greenhouse gas emissions. Passive solar design strategies can be used to limit building heating and cooling demands. Current passive solar design strategies, however, require substantial design effort for each individual project, often require mechanical and electrical control systems, and the approach is also difficult to implement in building retrofit projects. Solid-solid phase change materials (SS-PCM) are currently emerging as alternative materials for thermal energy storage. Here we present an exploratory study on two innovative climate responsive building enclosure systems that employ the transparency change and latent heat storage capacity of SS-PCMs as mechanisms to passively control building temperature. The first system is based on a thin layer of SS-PCM that is placed on top of a highly reflective film to control solar heat gain. The second system uses a layer of SS-PCM foam to store thermal energy and control heat flow. The performance characteristics of the systems are evaluated using finite element modeling techniques. Simulation results shed light on the synergistic interactions between different components of the systems and indicate that both systems can reduce undesirable heat exchange between the building and its environment if designed properly. Recommendations are made regarding various material and system parameters, including the attenuation coefficient of the SS-PCM, system thickness, void ratio and distribution of the void ratio of the SS-PCM foam based system, and phase transition temperature. (C) 2018 Elsevier B.V. All rights reserved.