Position #164 – Multichanneling Optics: Applications to Concentrating Photovoltaics

Host institution
ES - Universidad Politecnica de Madrid
Lab or research department name
Cedint (Centro de Domotica Integral – Research Centre for Smart Buildings and Energy Efficiency)
Electronic Engineering, Telecommunications
Sub-domain or keywords
Photovoltaic energy, Concentration, CPV, multichannel optics.
Type of mobility
Duration (months)
18 (to be divided in 2)

High Concentration Photovoltaics (>500x) is being pushed up to the range of 2000X by the recent advances in 3 and 4 junction solar cells whose high efficiency (>40%) is only usable if the cell is combined with an optical concentrator so the cell cost contribution to the total is diminished. Owing to the nature of these cells (which are formed by several subcells series connected with tunnel junctions), the illumination on the cell must be spectrally balanced and spatially uniform for any incidence angle of the sun within the acceptance angle of the concentrator. Additionally, the concentrator must have the highest possible acceptance angle because this parameter affects to the manufacturing tolerance of all the optical components of the system, including assembling, tracking, optical form factor tolerances and even surface roughness of the optical surfaces. Acceptance angle and concentration are competing aspects in an optical design. The so called Acceptance-Concentration product CAP has a fundamental physical upperbound. Combining all the optical requirements (high concentration, high acceptance, high spectral irradiance uniformity on the cell, and of course, a high optical efficiency) with a low cost is not a simple task. Inexpensive Optics could be approximated by few optical parts (we limit the design to 2 optical surfaces). Then, all the optical requirements must be achieved by an optical device containing only two optical surfaces (which in general are refractive).
The best candidate for such optical concentrator is the Fresnel Kohler array. This device is formed by parallel optical channels each one of them containing a Kohler configuration. Unlike conventional optical arrays, the optics of each channel is in general different. Recently a 9 channels Fresnel Kohler array has been proposed for CPV. The work to be developed will go deeply into this solution and will explore solutions with more than 9 channels as well as solutions combining multichanneling with strategies for increasing the overall efficiency such as sky splitting (Optics Express, Vol. 22, Issue S1, pp. A28-A34 (2014) http://dx.doi.org/10.1364/OE.22.000A28). The work will also study multichanneling for image formation.

From January 2016
Maximum available positions
Fluent English. Spanish is desirable although is not necessary (in case of ignorance of this language, willingness to learn it will be considered positive). Degree in Physics, Maths or Engineering is required.
Juan C. Miñano <jc.minano@upm.es>