Solar Divergence Collimators for Optical Characterisation of Solar Components

Abstract

Experimentation and laboratory optical tests on solar components are central aspects of the research on renewable energies. The key element of the proposed testing systems is a solar divergence collimator, which exactly reproduces in laboratory the sunlight divergence, while commercial solar simulators are mainly aimed to replicate intensity and spectrum of the sun. Precise solar divergence reproduction is essential to correctly assess the optical properties and to simulate the operative conditions of a solar collecting device. Optical characterisation and experimentation can give information about production quality and homogeneity; moreover, specific tests can address the serial production of solar components detecting defects type and location. For Concentrating Photovoltaic systems, appropriate tests can analyze solar concentrators of various shapes, dimensions, and collection features. Typically, to characterise a solar component the most important and commonly examined quantities are collection efficiency, image plane analysis, and angle dependence.

Technique for Outdoor Test on Concentrating Photovoltaic Cells

“…The proposed methodology has the advantage of reproducing the real working conditions and the sun trackers allow to mount a custom optical systems (collector with possible secondary optics) to focus sunlight on the photocell, while solar simulators have their own optical system that focuses artificial light on the cell. The laboratory experimentation, using a solar divergence collimator [11], permits a more precise evaluation of the optical characteristics of the components, while solar simulators often have a divergence much larger than the solar rays, being aimed to reproduce the solar intensity.…”

“…Some preliminary measurements are performed in laboratory with the purpose of determining the suitable positions for the cell in order to have an acceptable uniformity of illumination. A schematic view of the laboratory setup used is shown in Figure 2: it is a solar divergence collimator [11]. The optical system, constituted by source system, integrating sphere and mirror, produces a luminous beam with solar divergence of about 240 mm in diameter.…”

“…The solar divergence is hardly reproduced by solar simulators, while measurements with solar trackers [10] consent to replicate the real operative conditions. Alternatively, laboratory tests can be performed using a solar divergence collimator [11] that exactly reproduces the sun's divergence, thus permitting a precise evaluation of optical parameters and optical behavior of solar components. Analogously solar rays, concentrated over a sample, allow to study the optical properties and performance of PV cells or other components applicable to solar installations.…”

Optical Tests on a Curve Fresnel Lens as Secondary Optics for Solar Troughs

“…A solar divergence collimator [13] produces a beam with solar divergence of about 250 mm in diameter, with a high uniformity. Choosing appropriate components and set-up, the value of solar divergence results 0.48 degrees (total angular aperture, 2θ).…”

Light Management in Solar Modules

“…However, the difference to natural sunlight remains considerable, and, in particular, upon flashed operation the unavoidably transient character of the light always restricts the comparability of an efficiency measured with solar simulator to the real one obtained in the field. In the special case of concentrating photovoltaics, it has been reported recently that also the knowledge (and simulation) of the solar divergence is important for correct testing of the concerntrated photovoltaics (CPV) modules [30].…”