Building Integrated Solar Thermal Systems. Design and Applications Handbook

Abstract

The Renewable Energy Framework Directive sets a target of 20% for renewables by 2020. Buildingsaccount for 40% of the total primary energy requirements in the EU and are responsible for 30% ofgreenhouse gas emissions. Therefore, developing effective energy alternatives for buildings isimperative. Energy in buildings is used primarily for heating and cooling and for the provision of hotwater. One way to reduce the dependence on fossil fuels is by the use of renewable energy sources andsystems. The benefits of solar thermal systems are well known but one area of concern has been theirintegration. Most solar collecting components are mounted on building roofs with no attempt toincorporate them into the building envelope. In many instances they are actually seen as a foreignelement of the building. Many architects, irrespective of the potential benefits, object to this use ofrenewable energy systems (RES) due to this fact alone. It is therefore necessary to develop techniquesthat better integrate solar collectors within the building envelope and/or structures which should bedone in a way that blends into the aesthetic appearance and form of the building architecture in themost cost effective way.The Energy Performance of Buildings Directive (EPBD) requires that RES are actively promoted inoffsetting conventional fossil fuel use in buildings. A better appreciation of solar thermal system (STS)integration will directly support this objective, leading to an increased uptake in the application ofrenewables in buildings. This uptake of RES in buildings is expected to rise dramatically in the next fewyears. This is further augmented by a recast of the Directive which specifies that the buildings in the EUshould be nearly zero energy consumption (residential and commercial buildings by the year 2020 andpublic buildings by 2018, respectively). Meeting building thermal loads will be primarily achievedthrough an extensive use of renewables, following standard building energy saving measures, such asgood insulation or advanced glazing systems. Solar thermal systems are expected to take a leading rolein providing the thermal energy needs, as they can contribute directly to the building heating, coolingand domestic hot water requirements.A solar thermal system (STS) is considered to be building integrated, if a component (in most cases thecollector) is a prerequisite for the integrity of the building’s functionality. If the building integrated STS isdismounted, dismounting includes or affects the adjacent building component which will have to bereplaced partly or totally by a conventional/appropriate building component. This applies mostly to thecase of structurally bonded modules but applies as well to other cases, such as replacing with BISTS oneof the walls in a double wall façade.The scope of this document is to present a review of current STS state of the art technologicaldevelopments published in the area and the most suitable options for building integration RESapplications. The aim of the document is to determine the work carried out in the area of buildingintegration of STS. This will enable an understanding of how this integration is applied so far, which willhelp to identify new ways that this integration will be investigated subsequently. For architects, theapplication of PV and STC (solar thermal collector) systems in buildings must form part of a holisticapproach. A high-quality solar system can provide a substantial part of the building’s energy needs if thebuilding has been designed in the right way. Through a holistic approach, integrating these systems doesnot only mean replacing a conventional building material, but also aesthetically integrating it into the 5design, which is called architectural integration. The integration then takes over other functions of thebuilding’s skin. Mounted on a sloped roof for instance, profiled systems mean that PV or STC modulescan be part of the watertight skin. A distinction can be made between literal integration of thesesystems in the building skin as cladding elements or integrated into the roof or as building componentslike awnings, shading devices etc. (Reijenga and Kaan, 2011). The aim of architectural and buildingintegration of these systems into buildings is to reduce the requirement for land and the costs, inaddition to aesthetics that is generated by the process. This could be the cost of a support structure andthe cost of building elements, such as tiles and cladding elements. It is evident that PV and STC systemsintegrated into buildings give a more elegant look, and it is more efficient to integrate these systemswhen constructing the building, rather than mounting them afterwards. For example they may provide ahigh degree of solar shading for the building itself; this is particularly relevant in warm climates. Usuallythere are three zones for integrating the systems into buildings. These are the roofs, façades andbuilding components like balcony railings, sunshades and sunscreens (Reijenga and Kaan, 2011).Both PV and STC systems can be incorporated into buildings by either superimposition - where thesystem is attached over the existing building envelope, or integration - where the system forms a part ofthe building envelope (Fuentes, 2007)