Development and characterization of an FK photovoltaic concentrator for maximum conversion efficiency Pablo Zamora a , Maikel Hernández b , Juan Vilaplana b , Pablo Benítez a,b , Rubén Mohedano b , Juan C. Miñano a,b a Technical University of Madrid (UPM), Campus de Montegancedo 28223 Madrid, Spain b LPI-LLC, 2400 Lincoln Ave., Altadena, CA 91001, USA ABSTRACT The outdoor measurements of a single-cell concentrator PV module reaching a regressed 35.6% efficiency and a maximum peak efficiency of 36.0% (both corrected @T cell =25ºC) are presented. This is the result of the joint effort by LPI and Solar Junction to demonstrate the potential of combining their respective state-of-the-art concentrator optics and solar cells. The LPI concentrator used is an FK, which is an advanced nonimaging concentrator using 4-channel Köhler homogenization, with a primary Fresnel lens and a refractive secondary made of glass. Solar Junction’s cell is a triple- junction solar cell with the A-SLAM TM architecture using dilute-nitrides. Keywords: Fresnel lens, nonimaging, concentrator, photovoltaic, solar energy, Köhler integration 1. INTRODUCTION High concentration photovoltaics (HCPV) is a promising option to further reduce the solar electricity costs thanks to the continuous increases in efficiency of the triple junction cell technology at very high concentration levels. The present world record in the HCPV concentration range is 44.0% (recently surpassed by Japanese manufacturer Sharp with 44.4%, but for much lower concentration levels, 302x [1]), achieved by a Solar Junction’s cell with its A-SLAM TM lattice matched architecture and operating at 947x concentration [2]. This efficiency nearly doubles that of the best commercial 1-sun silicon solar cells, and there is a clear path for further efficiency improvements by increasing the number of junctions. However, to take full advantage of this high efficiency, these cells must be combined with concentrator optics that provide the required high concentration with a high optical efficiency and sufficient tolerances (reflected in the concentrator acceptance angle) to keep the cost low and the efficiency high at the real world array level. Additionally, the concentrator must also provide good spatial homogeneity of the cell illumination for the three junctions, which is an aspect that has been underestimated until recently [3]. In the last few years a new photovoltaic concentrator, called the FK, has been proposed by LPI to provide the state-of- the-art optical performance [4]. It is comprised of a four-fold symmetrical Fresnel lens and a four-fold secondary lens attached to the cell which, acting together, produce Köhler homogenization through its four separate channels. This device is able to provide simultaneously high optical efficiency, high concentration, excellent spatial and spectral uniformity and high acceptance angle. The high performance of the FK has been demonstrated by means of experimental measurements [5]. During the past few months, LPI and Solar Junction have been collaborating to design and manufacture a proof of concept prototype to demonstrate that very high module efficiencies can be obtained by combining Solar Junction’s cells with LPI’s optics, and that this can be achieved with both, very high concentration and high acceptance angle, features of crucial interest in the cost effectiveness of CPV systems. The first results of the complete prototype will be detailed along the text.