G. Alvarez+, M. J. Jimenez and M. R. Heras*

*CIEMAT.. Renewable Energy Department. Av. Complutense No. 22. Madrid, Spain.
28040. Tel/Fax: 91 346 6344. Email: mrosario. heras@ciemat. es,
mjose. Jimenez@.ciemat. es

+CENIDET, Mechanical Engineering Department. Prolong. Av. Palmira s/n. Col. Palmira.
Cuernavaca, 62490, Morelos, Mexico. Tel/Fax: +52 777 312-7613.
gaby@cenidet. edu. mx.

ABSTRACT

This paper presents a preliminary study to validate small scale solar test cells for thermal evaluation of building components such as windows and roofs. The description and performance of the scale test cells are described. The validation of the thermal performance was made with the real test cell Passys indirectly by applying the classical averaging method that was initially used for the Passys cells to determine overall heat loss coefficient, UA, and the solar heat gain, gA. The use of this methodology was selected, as a first approach, to evaluate the viability of the study of scale test cells. Our preliminary results indicate that some percentage differences were high for some tests. Therefore, it is necessary to increase the period of time of the measurements of the scale test cells, in order to use dynamic system methods to reduce the percentage differences of UA and gA.

INTRODUCTION

In the decade of 1970 and 1980, the applications of solar energy to buildings were encouraged in order to be more conscious of the conservation of energy. New materials for roofs, walls and windows appeared and the need to have detailed information about the solar thermal performance of the components in buildings was required. Thus, the thermal evaluation to characterised components of buildings using test cells was increasingly used. However, the solar thermal evaluation of components of buildings using small scale solar test cells have had very little attention and might be very valuable tool for an engineer, architect or contractors. The advantages of small scale test cells are their low cost (compared with full scale cells), data can be taken under carefully controlled conditions and they can be moved easily and be located in different places in order to investigate the influence of building materials of a selected region. Around this topic, there has been very few previous studies with small scaled solar test cells. Grimmer et al. in 1979 considered small test cells with some basic elements of passive design for the thermal modelling of passive solar heated building designs. He emphasized the theoretical considerations that have to be made about the modelling of those systems. Werner in 1986 used scaled modules that helped to determine the glazing design for conservation of energy. Mora et al. in 2003 reported a test cell used to characterise the heat transfer and
zonal mass by natural convection. About thermal evaluation of components of buildings, there have been some thermal studies in full scale cells. These cells have been developed in Europe since 1985, Vandaele et al. presented an overview on them in 1993, Hahne and Pfluger reported significant hardware improvements in 1996, and presently these testing capabilities are quite consolidated and the most recent research projects have been focused in improving testing procedures and application of techniques for dynamic data analysis. There have not been reported methodologies of small scale cells to test the components of buildings in warm climates connected with the consumption energy of an air conditioning system.

This paper presents a preliminary study of a small scale solar test cells and a comparison with the thermal performance of full scaled Passys test cells, using the classical average method that was used to characterised the Passys cells at the beginning (ISO 9869, 1994). The use of this methodology was selected, as a first approach, to evaluate the viability of the study of small scale test cells to test components of buildings such as roof and windows. The methodology gives information about the overall heat loss coefficient and the solar heat gain of the small test cell.