J. Cipriano1*, C. Lodi2, D. Chemisana3, G. Houzeaux4, O. Perpinan5

1 CIMNE-BEEGroup, Building Energy and Environment Group. International Centre for Numerical Methods in

Engineering. Dr. Ulles n° 2. 3°. 08224. Terrassa. Spain.

2 University of Lleida (UdL). CIMNE-MACS Clarssroom. Pere de Cabrera s/n. CREA Building. Cappont

Campus. 25001. Lleida. Spain

3University of Lleida (UdL). Solar Energy and Building Physics Group. Pere de Cabrera s/n. CREA Building.

Cappont Campus. 25001. Lleida. Spain

^Barcelona Supercomputing Centre (BSC-CNC)- Department of Computer Applications in e-Science &
Engineering. Nexus II Building. Jordi Girona, 29. 08034 Barcelona. Spain.

5ISOFOTON — Montalban, 9. 28014 Madrid.

Jordi Cipriano, eipriano@,cimne. upc. edu

Abstract

This research aims at developing new standardized typologies of semitransparent double skin fa? ades formed by PV laminates in the outer skin. At present there are many buildings in Europe which incorporate such active fa? ades, but all have been designed as user defined projects and very few accurately evaluate the feasibility of using the heat produced within the air gap. There is actually a lack of effective methodology to allow non-specialist architects to design and evaluate such fa? ades. This research tries to address this situation: the Spanish PV manufacturer ISOFOTON, together with the partners of the PVTBUILDING project: CIMNE, the UdL, PICH — Aguilera, DOMUS and BSC have begun a collaboration to design industrialized modules constituted by an external semitransparent PV layer, a wide air gap and an internal glass layer. This paper describes the results of four stages of a more wide research: a detailed analysis of the existing double skin fa? ades in office buildings and the definition of a family of standard PV modules and ventilated fa? ades; an intensive evaluation of the existing heat transfer relations for asymmetrical heated vertical air channels; the programming of a dynamic transient solver based on TRNSYS and the validation of the codes with the set up of prototypes and the beginning of an experimental campaign.

Keywords: PV/Thermal, ventilated double skin fa? ades, heat recovering

1. Introduction

In recent years many authors have been working in the field of double skin ventilated fa? ades. Since the 1990’s the Joint Research Centre has been carrying out an intensive characterization of PV ventilated fa? ades, with and without ventilated air gaps. Some European funded projects have been actively supporting this work, PASSLINK, PV-HYBRIDPAS and IMPACT [18]. Between 1999 and 2000, the Centre for Applied Research at the University of Applied Sciences Of Stuttgart [7,11] undertook the theoretical analysis and monitoring of the Mataro’s public library building, which had the first PV ventilated fa? ade in Europe. More recently, the treatment of the induced flow and the heat transfer at the air gap and the surfaces of a natural ventilated double skin fa? ade has been progressively refined by Brinkworth [3,4]. Concerning to the mathematical model to define the energy performance
of such fa? ades, sophisticated models for double skin fa? ades were developed by Saelens [15]. Although these detailed studies have lead to an increase in the knowledge of the heat transfer processes, there are still many unclear fields such as: the convective heat transfer coefficients definition; the evaluation of the direct solar radiation absorbed by the solid parts; the evaluation of the mass flow rate in non-developing turbulent flows and, the coupling with the HVAC systems.

Concerning to the dissemination of the PV ventilated fa? ades, many recent newly constructed office buildings have included such devices in their designs; however, the spread of this technology has not occurred at the necessary scale. One of the reasons, we believe, has to do with the lack of standardised designs which forces the designers to select the glass transparent surfaces and the support structures separately from the PV laminates, leading to fitting problems and size incompatibilities.