Optical characterisation and optimisation of a static Window

Optical characterisation and optimisation of a static Window

Integrated Concentrating Photovoltaic system

Nazmi Sellami ⇑,Tapas K.Mallick ⇑

Mechanical Engineering Department,School of Engineering &Physical Sciences,Heriot-Watt University,Edinburgh Riccarton EH144AS,UK

Received 27March 2012;received in revised form 31October 2012;accepted 17February 2013

Available online 22March 2013

Communicated by:Associate Editor Ursula Eicker

Abstract

In this work,three different geometrical properties have been considered to develop a new solar concentrator design for Window Inte-grated Concentrating Photovoltaic (WICPV).They are (i)elliptical entry aperture;(ii)hyperbolic profile section and (iii)square exit aperture.Due to the increasing demands for stationary solar concentrators for building integrated photovoltaic (BIPV),this new design focuses on the use as a stationary solar concentrator.The complete optical analysis of the concentrator is carried out via 3-D ray trace technique.The analysis is based on all necessary design parameters,i.e.,elliptical entry axis,concentrator height and the exit aperture geometry,in order to obtain the optimal overall optical performance of the new 3-D solar concentrator.Four different geometrical low concentration ratios were investigated:4Â,6Â,8Âand 10Â.Results of the computer simulation show that the designed concentrator of 4Âconcentration ratio gives the higher optical efficiency of 68%compared to the other low concentration ratios.The 6Â,however,gives a higher optical concentration ratio,despite having a lower optical efficiency (55%)than the 4Â.A prototype of the designed concen-trator was manufactured and tested under indoors conditions.The experimental results have shown an agreement by a difference of 5%with the simulation results.These results highlight how different factors need to be taken into consideration when carrying out opti-misation studies.Overall,the proposed concentrator looks promising with sound results to confirm its performance and validate it as a stationary solar concentrator and thereby promote its use in WICPV.Ó2013Elsevier Ltd.All rights reserved.

Keywords:CPV;BIPV;Optics;Low concentration;Ray trace;Solar energy

1.Introduction

PV applications for buildings began appearing in the 1970s.Photovoltaic modules were connected to,or mounted on buildings that were usually in remote areas without access to an electric power grid.Nowadays,solar panels for building integrated photovoltaics (BIPV)are increasingly being incorporated into the construction of new buildings as a principal or supplementary source of electrical power.PV cells can also be integrated into

windows maintaining the transparency which constitutes the main property of the glass facades (Wong et al.,2008).In order to improve the efficiency of PV,concentrating photovoltaics (CPV)systems have been developed;they can reduce the costs of solar electricity.Furthermore,solar concentrators are used to focus sun rays in a smaller area;therefore,the area of the solar panel is reduced thus bring-ing down the costs of the system.

All CPV systems have a concentrating optics and a solar rge efforts in the CPV research have focused on improving the performance of the photovoltaic solar cells (Cole et al.,2010).The solar cells have reached a peak level of development and commercial availability,however,

0038-092X/$-see front matter Ó2013Elsevier Ltd.All rights reserved./10.1016/j.solener.2013.02.012

⇑Corresponding authors.Tel.:+447900647293(N.Sellami).

E-mail addresses:solarnaz@ (N.Sellami),t.mallick@ (T.K.Mallick).

/locate/solener

Available online at

Solar Energy 91(2013)

273–282