Holographic lenses for building integrated concentrating photovoltaics Daniel Chemisana a,⇑ ,M a Victoria Collados b , Manuel Quintanilla b , Jesús Atencia b a Universidad de Lleida, Applied Physics Section of the Environmental Sciences Department, Escuela Politécnica Superior, Jaume II 69, 25001 Lleida, Spain b Universidad de Zaragoza, Applied Physics Department, Instituto de Investigación en Ingeniería de Aragón (I3A), Facultad de Ciencias, Pedro Cerbuna 12, 50009 Zaragoza, Spain highlights  A holographic solar concentrator has been designed, constructed and characterised.  The system configuration is suitable for building integration.  The holographic lens diffracts in the bandwidth to which the cell is more sensitive.  The system prevents the cell overheating.  The use of the holographic element increases the electrical efficiency of the system. article info Article history: Received 19 February 2013 Received in revised form 11 April 2013 Accepted 12 April 2013 Available online 11 May 2013 Keywords: Holographic lens Solar concentration Photovoltaics Building integration Spectral behaviour abstract A volume transmission phase holographic element was designed and constructed to perform as a build- ing integrated photovoltaic concentrator. The holographic lens diffracts light in the spectral bandwidth to which the cell presents the highest sensitivity with a concentration factor of 3.6X. In this way, the cell is protected from overheating because the infrared for which the solar cell is not sensitive is not concen- trated. In addition, based on the asymmetric angular selectivity of the volume hologram and based on the linear concentration, only single-axis tracking is needed. The use of the holographic element increases the efficiency of the PV cell by 3% and the fill factor by 8%. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The development and implementation of Concentrating Photo- voltaic (CPV) systems allows the reduction of the number of solar cells, which are the element with the higher environmental and economic cost. Besides, under concentration, the generation of electrons within the PV cells is more efficient than for the case of the conventional PV cells (without concentration). On the other hand, the concentrating PV cells exhibit an over- heating condition and thereby need refrigeration in order to keep their efficiency at high level. Furthermore, for concentration factors higher than 4, tracking systems are also needed. These two pecu- liarities can be partially compensated by using holographic optical elements. Holographic PV Concentrators (HCPV) were proposed for the first time in the 80s and they offer several benefits, compared to conventional optical elements, such as light weight, low cost fabrication and versatility (the same element can perform different functions). Among the different types of holograms, the properties of vol- ume phase transmission holograms have been studied in terms of their use as solar concentrators [1–4]. As transmission elements, they have the potential to be implemented in building structures as they act and appear as windows. Volume phase transmission holograms achieve high efficiency; they can reach 100% efficiency for a selected wavelength, although their efficiency could be lower if several holograms are multiplexed. However, they exhibit two main characteristics that affect their performance as solar concen- trators: the angular and the chromatic selectivity. Due to the chromatic selectivity, hologram diffraction efficiency depends on wavelength. This could be a disadvantage, because only a limited range of the spectrum is concentrated onto the PV cell. This range can be greater by multiplexing several holograms in the same plate, each one acting on different ranges of the solar spectrum. On the other hand, the response of the PV cells also de- pends on the wavelength. For example, usually Si or GaAs cells have not sensitivity for wavelengths above 1200 nm. The energy of the solar spectrum which is associated with these wavelengths overheats the cells and thus their efficiency decreases. The holo- gram can be designed to be efficient at the spectral range in which 0306-2619/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apenergy.2013.04.049 ⇑ Corresponding author. Tel.: +34 973003711; fax: +34 973003575. E-mail address: daniel.chemisana@macs.udl.cat (D. Chemisana). Applied Energy 110 (2013) 227–235 Contents lists available at SciVerse ScienceDirect Applied Energy journal homepage: www.elsevier.com/locate/apenergy