Efficiency analysis of flat plate collectors for building facade integration

Abstract

A theoretical approach has been used to evaluate the performance of facade integrated solar collectors based on the physical collector parameters such as absorber plate absorptance, transmittance of the glazed cover plate and insulation thickness. A 1D steady state model, based on the Hottel Whillier Bliss equation, was employed to determine the effect of changing paramete rs to me et facade integration criteria. Buildings account for 40% of the final energy consumption in Europe (1), Over half of this energy use is associated with building heating, cooling and domestic hot water (DHW) demands (2) . This energy is predominantly provided through the burning of fossil fuels, which can be reduced through the implementation of renewable energy systems. Solar thermal systems, for building applications, make use of an area on the building's envelope to install the solar collectors, which in turn, absorb the solar radiation and convert it to useful heat for the building's heating applications. These solar collectors are usually mounted on the roofs of buildings; however, a limited roof area and a high heating load may require the area of the facade to house these collectors (3). Architectural integration barriers can become significant when the facade is used to house the collectors. Solar thermal collectors may be categorised as Unglazed Collectors (UC), glazed Flat Plate Collectors (FPC) or Evacuated Tube Collectors. The FPC is Europe's most popular collector, accounting for 85% of the market share (4). They consist of an absorber plate with a high absorptance and conductivity, insulated at the back using standard insulating wool or foam and insulated at the front through the use of a transparent cover (typically glass) which provides an air gap between the absorber and cover layer. A 1D steady state mathematical model, based on the Hotel Whillier Bliss equation (5), is used to examine the performance of FPC whe re the parameters are altered as appropriate for facade integration.