Contribution of Solar Thermal Systems to building energy. performance – comparison of Portuguese methodology with European

Standard EN 15316 (part 4-3)

Maria Joao Carvalho ^ and Ana Neves 1

1 INETI, Department of Renewable Energies, Campus do Lumiar do INETI, 1649-038 Lisbon, Portugal
* Corresponding Author, mioao. carvalho@ineti. pt

Abstract

In the frame of European Directive for Energy Performance in Buildings, EU Directive 2002/91/CE, Portugal produced legislation transposing the EU Directive and imposing the usage of thermal solar systems for hot water preparation. The energy necessary for the preparation of hot water constitutes one of the terms for evaluation of energy performance of the building. The calculation methodology is incorporated in a software tool developed by INETI and called SolTerm. At the end of 2007, CEN also published a set of standards, EN 15316, covering “Heating systems in buildings and methodologies for calculation of system energy requirements and system efficiencies”. In this set of standards, part 4-3 is dedicated to Thermal Solar Systems and introduces a calculation methodology for determination of the energy delivered by a thermal solar system. The present work compares the results of both methodologies and shows that the difference between the two methodologies is mainly dependent on collector efficiency parameters, due to the limits of application of the methodology of EN 15316, based on f-chart method.

Keywords: thermal solar systems, hot water preparation, heat delivered, building energy performance.

1. Introduction

In the frame of European Directive for Energy Performance in Buildings (EPBD), EU Directive 2002/91/CE, Portugal produced legislation transposing the EU Directive. This legislation went in force in April 2006 and included a Solar Thermal Obligation. This obligation is present in the new Portuguese Thermal Performance Building Code (RCCTE) [1], imposing the usage of thermal solar systems for hot water preparation if there are favourable conditions of exposure (if the roof or cover runs between SE and SW without significant obstructions) in a base of 1m2 per person (that can be reduced up to 50%, in certain conditions).

In the Portuguese legislation, the energy necessary for the preparation of hot water constitutes one of the terms for evaluation of energy performance of the building, as well as, the heating and cooling loads of the building.

This term takes into account the positive contribution of the use of a thermal solar system for hot water preparation. To take this into account it was necessary to establish a calculation methodology for the energy delivered by the thermal solar system. This methodology is incorporated in a software tool developed by INETI and called SolTerm [2].

At the end of 2007, CEN also published a set of standards, EN 15316 [3], covering “Heating systems in buildings and methodologies for calculation of system energy requirements and system

efficiencies”. In this set of standards, part 4-3 is dedicated to thermal solar systems and introduces a calculation methodology for determination of the energy delivered by the solar system.

The present work compares the results of both methodologies and establishes the conditions in which it is possible to consider that they give an equivalent input to the calculation of energy needed for hot water preparation and the energy performance of the building.

In Section 2, a short description of both calculation methodologies is presented. Section 3. highlights the specific aspects of the Portuguese legislation that are relevant for the calculation of the energy contribution of the thermal solar system to the building energy performance. The results of calculations made for different situations are presented in section 4. Final conclusions are presented in section 5.

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