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The transient thermal behaviour of a ventilated solar honeycomb (SHC) façade element was investigated with the help of numerical simulations. Therefore two three-dimensional CFD models were used to consider a SHC façade element with and without attached PV cells at the exterior glass pane. Beside a natural convective flow model also a radiation model with two wavebands was implemented to enable the differentiation between short-wave solar radiation and long-wave thermal radiation. In a laboratory experiment temperatures in the ventilation cavity and the heat flux at the rear wall of the SHC façade were monitored and compared to simulation results. The experiment using a solar simulation device was carried out for one façade element with PV cells at the exterior glass pane and for one façade element without PV cells. The time-step size for the transient simulations was dramatically reduced after the determination of the maximum time-step size, which finally enabled the analysis of the thermal behaviour over a prolonged period (one day or longer) within reasonable simulation durations. Moreover, the impact of the SHC’s material properties on the dynamic thermal behaviour was analysed with the three-dimensional CFD-model. Differences in heating rate, heat flux and temperatures were determined and compared by using five different materials instead of the cellulose honeycomb. Finally this study obtained the impact of hourly changing external climate conditions on the thermal behaviour of a single 1 × 1 m SHC façade element using climate data from a cold winter’s day and a hot summer’s day which were measured in Graz, Austria. [ABSTRACT FROM AUTHOR]

The thermal behaviour and air flow characteristic for a solar honeycomb (SHC) façade element at different PV cell configurations was analysed in order to evaluate the thermal and ventilation performance as well as the electrical output. The base construction of this façade prototype inherited from the base façade element “GAP-Skin”, which is a development of the company “Gap 3 solutions GmbH”. The aim was to find a PV cell configuration which shows the best ratio between the thermal behaviour of the SHC façade and the electrical output of the PV array. Three-dimensional CFD simulations were performed and compared with measurement data from a laboratory experiment. In order to do this, a test stand was built with a 1 × 1 m SHC façade element and a solar simulator. The CFD models contained a detailed radiation model to take solar and thermal radiation into account. The numerical results from the developed models correlated well to a large extent with the measured data. Furthermore, this study obtained the thermal behaviour of the SHC façade element in summer and winter climate conditions in the temperate zone, considering different solar absorption characteristics of the SHC at different solar angles. [ABSTRACT FROM AUTHOR]

This study determines thermal behaviour and airflow characteristics inside multifunctional façade elements. The façade elements investigated were designed in course of the research project “Multifunctional Plug & Play Facade” [1] . The integration of energy converting systems in a façade construction causes higher temperatures on the backside of the collectors impacting subjacent layers and the interior. Due to periphery openings, heat can partly be transferred to the exterior by the effects of natural ventilation. With the help of ‘steady state’ 3D Computational Fluid Dynamics (CFD) models of three different façade elements were investigated and compared. In particular this study presents a detailed analysis of airflow and the thermal behaviour of a photovoltaic module (PV), a solar thermal collector (ST) as well as a transparent single layer glass panel used as impact pane (TR) all integrated into the façade construction. Despite high temperatures in the solar thermal collector the lowest air temperatures inside the cavity were detected for the ST façade. The ventilation effects of the side openings were clearly identified in all façades. The numerical model includes the effects of heat transfer, buoyancy, radiation and the impact of solar radiation. Data from on-site measurement did largely match with the simulations’ outcome. [ABSTRACT FROM AUTHOR]