Simple Methods to Approximate CPC Shape to Preserve Collection Efficiency

Abstract

The compound parabolic concentrator (CPC) is the most efficient reflective geometry to collect light to an exit port. Anyway, to allow its actual use in solar plants or photovoltaic concentration systems, a tradeoff between system efficiency and cost reduction, the two key issues for sunlight exploitation, must be found. In this work, we analyze various methods to model an approximated CPC aimed to be simpler and more cost-effective than the ideal one, as well as to preserve the system efficiency. The manufacturing easiness arises from the use of truncated conic surfaces only, which can be realized by cheap machining techniques. We compare different configurations on the basis of their collection efficiency, evaluated by means of nonsequential ray-tracing software. Moreover, due to the fact that some configurations are beam dependent and for a closer approximation of a real case, the input beam is simulated as nonsymmetric, with a nonconstant irradiance on the CPC internal surface.

Evaluation of Symmetric C-PVT Solar Collector Designs with Vertical Bifacial Receivers

“…In concentrating systems, a trade-off between system efficiency and cost reduction must be found (Jafrancesco et al 2012), which always involves truncation of the reflector before reaching the maximum theoretical concentration. Concentrators consist mainly of two groups when considering the concentrator surface: 2D and 3D collectors.…”

Design and Testing of a Shell-Encapsulated Solar Collector with the Compound Surface Concentrators

“…Substituting the experimental data into (5) gives the daily average efficiency of 51.3% for the 23rd of January and 50.1% for the 25th of January, respectively. The small difference in the efficiencies for these two days may be due to the difference in the average operating temperatures.…”

“…According to (5), the daily average thermal efficiency of the prototype solar collector hot water system on the 22nd of January may be calculated as follows:…”

“…In comparison, Rabl et al [3] had studied combination of nonevacuated solar collectors with compound parabolic concentrators (CPC). Li and Wang [4] have investigated a combined trough parabolic concentrator and evacuated tube solar collector system and measured an efficiency of about 70% at the outlet water temperature of 105 ∘ C. Although the production of CPC optical surfaces can be done only by expensive single-point machining techniques, it is possible to approximate the complex surfaces of the CPC by means of a limited number of simpler shapes without severe efficiency 2 International Journal of Photoenergy losses [5]. Adsten et al [6] have proposed a so-called MaReCo design of solar concentrators for stationary installation.…”

Experimental and computational fluid dynamics investigations of tracking CPC solar collectors

“…The focus of the study was to investigate the location of the hot spots on the absorber. Jafrancesco et al (2012) analyzed various methods to model an approximated CPC with an aim to identify simple and cost-effective methods. In addition to ray tracing modeling, computational fluid dynamics (CFD) was also successfully implemented by researchers in the design optimization of CPCs.…”