D. Faggembauu, M. Soria, A. Oliva and J. Cadafalch

Centre Tecndlogic de Transferencia de Calor (CTTC)

Lab. de Termotecnia i Energetica
Universitat Politecnica de Catalunya (UPC)
labtie@labtie. mmt. upc. es, www. cttc. upc. edu

Building facades have large glazed areas, which are normally combined with opaque zones. In double-skin facades, these opaque areas are located in the inner layer of the double-skin. It is possible to take advantage of these areas by means of integrated collector-storage systems, built in modular form and implemented in the facades. Collected and stored solar energy may be used to contribute to reduce the energy consumption needed to produce domestic hot water or space heating in a building. A numerical study has been carried out in this work by means of an own numerical code which allows the transient simulation of advanced facades. Numerical code was validated by comparison with experimental results obtained from prototypes tested in real outdoor conditions.

Introduction

Building envelopes must combine architectonic requirements with energetic performance in order to allow an optimal thermal behaviour of the building. The use of large transparent areas in the facades of singular buildings is becoming an extended practice in order to keep an uniform outdoor appearance and a transparent and modern image.

Transparent areas combined with opaque zones in multilayered facades is being a sub­ject of continuous development, in this field many researchers have analyzed its thermal optimisation [1], [5] and [3], in combination with transparent insulation [7] and phase change materials [7] and [8].

Facades present a potential utility not only for passive heating and cooling the building but also for allowing an extended energy collection and accumulation of solar energy. This work intends to contribute to this objective by means of the analysis of the thermal performance of liquid-based solar collector-accumulators, built in modular form and installed in the facades as part of the inner layer of a double-skin facade or directly as part of a single skin envelope.

Energy stored in water tanks at the facades may contribute to get a reduction of energy consumption applied to domestic hot water or space heating.

This work presents some conclusions of the results obtained in the framework of a CRAFT European project (ASFIC) [9]. A specific numerical simulation tool, called AGLA [6], for the simulation of the advanced facades has been used. Numerical work has considered a transient and one-dimensional behaviour. Numerical predictions have been compared with experimental measurements taken in real-scale test facade prototypes at outdoor con­ditions. Design aspects as collector areas, storage capacities, selective surfaces and the application of honeycomb type transparent insulation materials (TIM) were numerically in­vestigated for two climatic conditions: Mediterranean and Central-European climates. The results presented in this paper are restringed to the performance of a double skin envelope, with transparent insulation, for both climates. Extended situations were studied within the project.