The project APOLLON (Multi-APprOach for high efficiency integrated and inteLLigent CONcentrating PV), carried out in the European Seventh Framework Program, has concerned the optimisation and development of Concentrating Photovoltaic (CPV) systems based on refractive and reflective optics. The different technology paths have been followed with an integrated approach, by addressing the research on the whole development chain of the Concentrating Photovoltaic Technology: from the improvement of the Metal-Organic-Chemical-Vapor Deposition (MOCVD) technique, which is used for the growth of semiconductor materials composing the photovoltaic devices, till to the final construction of a prototype concentrating photovoltaic system.

In order to achieve the higher potential for a future commercial exploitation of the CPV technology, the APOLLON Consortium has been formed by aggregating 17 Partners (coming from 8 European countries), joining the two “wings” of technological innovation: the research centres and the industry, fixing the final objective to develop an innovative, high concentration CPV system, with a target cost of 2 Euro/W. Different optics have been developed and compared, from Fresnel and hybrid prismatic/Fresnel to spectrum splitting solutions.

The ultimate product developed in APOLLON has been a concentrating mirror-based photovoltaic system which adopts new tracking strategies based on new Intelligent Concentrator (IC) PV modules, which, at the end of the project development, reached 30 % efficiency (850 W/m2 and 25°C ) with high efficiency InGaP/InGaAs/Ge multi-junction (MJ) solar cells. The new IC PV modules have integrated patent pending sun pointing sensors, which allow tracking the sun with high precision (<0.1° experimental validated), and DC/DC devices with Maximum Power Point algorithm which are able to maximize the production of the electric power generated by each CPV module. Patent pending new optics working at high concentration factor (around 800 X) have also been developed.

The APOLLON Consortium has also investigated new technological route enabling to expand the combination of semiconductor materials to be used in the multi-junction solar device, in particular demonstrating the possibility to deposit in the same MOCVD growth chamber both elements of group IV and elements of groups III and V of the periodic table. Combining III-V and Ge alloys is expected to show further progress in solar cell efficiency surpassing the 45 % value.