The system efficiencies of the fagade-integrated solar collectors with green black, blue and white absorbers were measured (Svasand, 2003). The measurements were corrected for the thermal contributions of the system components and the collector efficiency was deduced. As the efficiency curves revealed large uncertainties for very small and large AT/I, Table 4 lists the collector efficiency n for AT/I = 0.03 (Km2)/W, which lays within the typical range of operation of the present collector.

For the green absorber the collector performance in a fagade with and without ventilated cavity is almost equal within the uncertainty. As confirmed by the absorptance measurements (Fig. 8), the efficiency of the green absorbers was very close to the black absorbers.

No measurements were available for the black absorbers in the fagade with ventilated cavity. The large uncertainties for the collector efficiency for the blue and white painted absorbers are caused by the fact that the measurements were carried out late in the year (September, October).