Prototype fabrication and experimental investigation of a conjugate refractive reflective homogeniser in a cassegrain concentrator
Elsevier for International Solar Energy Society
© 2016 The Author(s). Published by Elsevier Ltd. Open Access funded by Engineering and Physical Sciences Research Council under a Creative Commons license: https://creativecommons.org/licenses/by/4.0/
The conjugate refractive reflective homogeniser (CRRH) is experimentally tested within a cassegrain concentrator of geometrical concentration ratio 500× and its power output compared to the theoretical predictions of a 7.76% increase. I–V traces are taken at various angles of incidence and experimental results showed a maximum of 4.5% increase in power output using the CRRH instead of its purely refractive counterpart. The CRRH utilises both total internal reflection (TIR) within its core refractive medium (sylguard) and an outer reflective film (with an air gap between) to direct more rays towards the receiver. The reflective film captures scattered refracted light which is caused by non-ideal surface finishes of the refractive medium. The CRRH prototype utilises a 3D printed support which is thermally tested, withstanding temperatures of up to 60 °C but deforming at > 100 °C. A maximum temperature of 226.3 °C was reached within the closed system at the focal spot of the concentrated light. The material properties are presented, in particular the transmittance of sylguard 184 is shown to be dependent on thickness but not significantly on temperature. Utilising both TIR and standard reflection can be applied to other geometries other than the homogeniser presented here. This could be a simple but effective method to increase the power of many concentrator photovoltaics.
This work was partly funded by the Newton Bhabha PhD Placement fund and partly by DST, India (Ref No: DST/SEED/INDO-UK/002/2011) and EPSRC, UK, (Ref No: EP/J000345/1) through the BioCPV project. Authors acknowledge all funding agencies for the support.
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.
Vol. 142, pp. 97 - 108