Thermal performance evaluation of solar combisystems using a global approach

M. Albaric1*, J. Nowag and P. Papillon1

1 CEA, LITEN, INES 50 avenue du Lac Leman, 73377 Le Bourget du Lac, France.
* Corresponding Author, mickael. albaric@cea. fr

Abstract

Solar energy of today’s solar combisystems provides nearly 20 to 50 % of the total heat demand of a modern standard single family house, depending on climatic conditions. The European market offers a huge variety of solar combisystems and up to now no uniform standard exists that can prove the thermal performances of systems. The system design with its control algorithms plays a very important role and has to be considered carefully. It is obvious that the performance of solar combisystems can vary with different climate conditions and varying building typologies. The focus of this work lays on the choice of the weather data for a 12 test days which allows an annual prediction of the auxiliary energy used. They have to be chosen from a reference weather data for a specific climate zone. Solar irradiation and ambient temperatures should closely correspond to the curves of an annual weather cycle.

Keywords: Solar CombiSystem, performance evaluation, global approach, test lab

1. Introduction

Although the European solar thermal market for single and multifamily houses offers today many efficient and reliable products, there is still a high need in system optimization. It is particularly the case for solar combisystems, used for space heating and domestic hot water preparation, in which many individual designs with different control strategies entered the market during the last two decades. For a long time, it has been difficult to determine an accurate performance rating for those systems, and even more difficult to compare them, because there were no common definitions of terms or standard test procedures for that type of system. For the establishment of that fast increasing market and a sustainable further development, the existence of uniform standards, recognized by the whole solar industry, is very important.

To contribute to the national and European research needs, the French National Institute for Solar Energy ‘Institut National de l’Energie Solaire’ (INES) is setting up a new test facility in its laboratories. The objective is to develop a methodology for a 12-day performance test, which allows an annual prediction of the auxiliary energy used and therefore a statement on the energy savings during one year.

2. The context

Several methods have been developed that are briefly described below.