Research on climatically active solar facades with the integration of the advanced material solutions

abstract

English

Recent research and development in the façade engineering field highlights the need of comprehensive system solutions and advanced materials. The real performance of these materials and façade systems is very relevant issue as they can contribute towards the European energy and environment policies: e.g. the implementation of nearly-Zero Energy Buildings (nZEB) required by the Energy Performance of Buildings Directive (EPBD). The development and implementation of novel façade concepts needs to be accompanied by applying of appropriate simulation and experimental methods. These methods are involved in performance prediction of the façade concepts. Presented research focuses on verification of thermal, energy and life cycle performance of advanced materials implemented in modular solar façade concept. The concept is based on sensible use of (renewable) solar energy to reduce the heating and cooling demand of buildings. The concept investigates integration of transparent insulation materials (TIMs) in opaque building façades in a way similar to more common “Trombe wall” systems. For this purpose the TIMs are combined with spectrally selective layers (non-selective absorber nSA and selective absorber SA types), enhanced with optical raster and heat accumulation layers based on latent thermal energy storage (basically PCMs). The proposed concept was tested at laboratory materials´ level, then full scale both in a climate chamber and real climate conditions. Currently there are two ongoing full scale outdoor tests in Brno (Czechia; see Figure) and Bratislava (Slovakia). Several variants of façade structures incorporating TIMs are tested there in real climate. The tested variants include different types of TIMs (with cavities parallel or perpendicular to the surface) as well as varying composition of the structure (see Figure). Especially the influence of various polycarbonate-based TIMs (with different thermal and optical parameters representing different number of chambers and geometry) on the overall performance of the façade is studied in detail. In general, polycarbonate systems are similar in thermal performance to standard glazing systems. However, recent technological advances in polycarbonate production may have opened ways for new integrations. In these aspects, the presented research pursues utilization of solar transmittance of the material in multi-layer façade concepts. At the thermal energy storage level, the usefulness of PCMs in heat accumulation layers is considered. The reason is that PCM layer adjacent to the ventilated air cavity could influence temperature response of the facade concept and further increase its efficiency. The data measured during the full scale tests include typically: whole temperature profiles, heat fluxes, and total solar transmittance. Measuring total solar transmittance and evaluating the amount of solar radiation penetrating through the multi-wall structure of the TIMs presented a particular challenge. A specific methodical approach is applied in this relation to provide accurate data, especially in real climate conditions. Although there are many specific issues to take into account, such as inclined angular dependence, fluctuations of solar irradiation and overall solar distribution as well as cardinal point aspect, the using of solar transmittance estimating by real outdoor measurements is involved, where the sun is the source of energy. This corresponds to long-term measurements at full scale vertical level in order to demonstrate year-round progress of the total solar transmittance and passive solar gains. Depending on climate conditions the measured values of total solar transmittance (both in laboratory and real climate) differ by tens of percent. Finally, the extensive measurements provide real performance data that are used to verify the computer energy and CFD simulations and optimize the design of the final façade concept.

Transparent Insulation Materials (TIMs), Phase Change Materials (PCMs), Optical and thermal performance, Building energy simulation, Full-scale testing

ČEKON, M.; SLÁVIK, R.; STRUHALA, K.; ČURPEK, J.

24. 1. 2018

ne-xt facades – Adaptive Facade Network

Munich

58

59

2

http://tu1403.eu/wp-content/uploads/COST-Next_proceeding_high_res.pdf