Energy and Buildings 65 (2013) 137–145 Contents lists available at ScienceDirect Energy and Buildings j ourna l ho me page: www.elsevier.com/locate/enbuild Visual comfort assessment of smart photovoltachromic windows Alessandro Cannavale a,1 , Francesco Fiorito b,∗,1 , Debora Resta c , Giuseppe Gigli a,d,e a Center for Biomolecular Nanotechnologies@UniLe, Istituto Italiano di Tecnologia, via Barsanti, 73010 Arnesano, (Le), Italy b The University of Sydney, Faculty of Architecture, Design & Planning, 148 City Road, 2006 Sydney, Australia c Independent Engineering Professional, Italy d NNL – National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano 16, 73100 Lecce, Italy e Dipartimento di Matematica e Fisica “E. De Giorgi”, Universita’ del Salento, Via per Arnesano, 73100 Lecce, Italy a r t i c l e i n f o Article history: Received 30 January 2013 Received in revised form 7 May 2013 Accepted 9 June 2013 Keywords: Photovoltachromic Building integration Photoelectrochromic Visual comfort Solar control Transparent building envelope a b s t r a c t An experimental study of photovoltachromic (PVCC) devices for dynamic solar control in buildings is presented. The fabricated devices underwent a complete opto-eletctrical characterization and the results obtained were employed as an input for the simulation of building integrated multifunctional windows. This multidisciplinary activity aims at achieving relevant feedbacks from the simulation of real large area devices in order to adjust and even direct further experimental efforts, before reaching the production phase. Devices having different electrochromic capacitances were used and the optical measurements became useful inputs for the simulation task. Simulation’s results turned into feedbacks concerning the modulation of the transmittance spectra, the colour of bleached devices, the scale-up of PVCCs. Devices used in the current work showed a power peak of 4.22 mW/cm 2 at the maximum power point and a smart modulation of optical transmittance of 50.16% (at 700 nm). Simulations of natural light penetration in office buildings showed that the integration of PVCCs in traditional windows could dramatically increase indoor visual comfort. An increase of the average UDI for a typical room up to 71.8% and a decrease of intolerable glare levels (DGP higher than 0.45) down to 12% were the major benefits of the substitution of traditional clear glasses with integrated PVCCs. © 2013 Elsevier B.V. All rights reserved. 1. Introduction 1.1. Smart electrochromic windows: integration strategies and comfort issues In recent years several research activities have been directed towards smart materials and devices, in order to achieve a dynamic solar control in transparent building envelopes (often referred to as “smart windows” or “switchable glazing”) [1,2]. A large number of studies are currently in progress about electrochromic windows [3]. Such devices astonishingly enhance the energy performances of windows with respect to conventional shading and solar control devices, with several other fallouts: reduction of cooling, heat- ing and ventilation loads, and a considerable reduction of artificial lighting due to a correct use of daylighting as a source of illumina- tion [4]. An interesting paper by Azens et al. [5] has investigated the energy savings obtained by using electrochromic glazing eventually showing how smart windows are able to yield energy efficiency as ∗ Corresponding author. Tel.: +61 2 9351 5601; fax: +61 2 9351 3031. E-mail addresses: francesco.fiorito@sydney.edu.au, f.fiorito78@gmail.com (F. Fiorito). 1 These authors contributed equally to the work. well as comfort for the users of the building, using daylighting as an efficient source of illumination, even outperforming photovoltaic fac ¸ ades in terms of energy savings. However in many applications of smart windows an efficient strategy for solar control contrasts with the requirement of a visual perception of external environment, due a substantial reduction of the visual transmittance of Electrochromic (EC) windows. The main issue of building integration of EC devices, which still remains open, is the necessity of the adoption of advanced control strategies, in order to automatically balance thermal and visual comfort parameters according to the fluctuation of inci- dent solar irradiance. Detailed assessment of control strategies of EC windows operational parameters [6–9] showed how switch- ing settings could dramatically change indoor comfort levels and energy consumptions. As a matter of fact, energy consump- tion variations related to different control strategies based on indoor lighting levels, time-schedule control, or more complex fuzzy logics, have considerable deviations (24% for winter heat- ing, 39% for summer cooling, 20% for winter electricity and even 63% for summer electricity), always with the same bound- ary conditions [7]. Furthermore, local thermal discomfort is also noticeable in EC windows, as the portion of solar radiation not used for daylight purposes is absorbed and re-irradiated by the glass. 0378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.enbuild.2013.06.019