Optical tests for sunlight concentrators

Solar concentrators have been studied and experimented within our researches on renewable energies. Our laboratory has developed fibre-coupled collectors, CPV systems and optical systems coupled to various devices. These sunlight concentrators are designed to be applied in thermal sector, internal illumination or photovoltaic field. The optical characterisation of manufactured collectors represents a crucial aspect of this work. Some tests compare the measured values of optical characteristics to the nominal values simulated in the optical project. Other optical measurements verify the homogeneity of collector production, comparing the optical features among the different samples corresponding to the same optical project. Our laboratory has developed measurement configurations and procedures to characterise concentrators of reduced size (max diameter/diagonal 240mm). The solar collectors under test can have various shape, dimensions and collection characteristics. Consequently each image presents different light levels and uniformity features, which require the use of suitable hardware and procedures. The paper illustrates instrumentation, optical set-up and methodology, considering the point of view of the researcher realising the measurements. The optical test allow determining image plane analysis, angle dependence, collection efficiency and spot size.