J. Metzger*, T. Matuska and B. Sourek

CTU in Prague, Dept. of Environmental Engineering, Faculty of Mechanical Engineering, Technicka 4, 166 07 Prague 6, Czech Republic

* Corresponding Author, iuliane. metzger@fs. cvut. cz

Abstract

Energetic behaviour of solar combisystems equipped by solar flat-plate collectors with different grade of evacuation in various collector-envelope configurations operating to different types of heating systems has been investigated through computer simulations. Performance of given solar combisystem configurations and influence of collectors on the building performance (winter gains and summer loads) have been investigated. The simulation results underline the high performance of solar collectors with low heat loss and advantageous direct integration of solar collectors into the building faqade compared to separate installations (higher solar fractions, lower stagnation time). Solar collectors thermally coupled with low-energy building envelope do not affect the indoor environment dramatically when applied in usual design parameters even for high-performance vacuum collector case.

Keywords: solar collector, solar combisystem, building integration, evacuated collector

1. Introduction

Progressing tendency in low-energy and passive housing has increased the demand for solar combisystems for domestic hot water preparation (DHW) and space heating (SH). Following the European strategy [1] which now fully promotes the solar thermal heating and cooling sector and aims towards the standard of a ‘Solar Active House’ (heating and cooling demand is covered to 100 % by solar thermal energy) high potentials for solar combisystems are offered to meet this demand. Additionally, together with low-energy housing, an interest for solar collector integration into the building envelope has arisen to meet not only the technical advantages (lower heat loss of collectors, passive heat gains in winter) but even aesthetical and architectural demands. Moreover, the integration of solar collectors into the building envelope instead of separate installation represents transition from the concept of envelope considered as a heat loss to advanced multifunction envelope being both building construction and source of renewable heat (energy active envelope). Constructional building integration of solar collectors lying in the replacement of building envelope construction by the solar collector seems to be a challenging issue crucible for future development and spreading of solar technologies.

In preceding studies [2-4] solar DHW systems and combisystems with envelope integrated flat- plate collectors have been investigated from the point of system performance (solar gains, solar fraction, stagnation level) and building behaviour (winter heat gains, summer loads). Extensive parametric simulation analysis of solar combisystems presented in the paper has been performed to take solar flat-plate collectors with different grade of evacuation in various collector-envelope configurations operating to different types of heating systems into consideration.

2. Model description

Parametric analysis has targeted the energetic behaviour of solar combisystems for domestic hot water and space heating in a low-energy house with three types of heating systems (air heating, radiators, radiant heating) and three levels of pressure inside solar flat-plate collectors (atmospheric, subatmospheric evacuated to 1 kPa and vacuum with 1 Pa) and different types of collector installation (separate installation at slope 45°, integration into 45°sloped roof and integration into vertical facade).