Loss-of-load probability of photovoltaic water pumping systems A. Hadj Arab a,b, * , F. Chenlo b , M. Benghanem c a Centre of Development of Renewable Energies, BP 62, Bouzar eah 16340, Algeria b Departamento de Energ  ıas Renovables––CIEMAT, Avda. Complutense, 22, Madrid 28040, Spain c Institute of Electronics, University of Sciences and Technology Houari Boumediene, BP 32, El-Alia, Bab-Ezzouar 16111, Algiers, Algeria Received 10 June 2003; received in revised form 27 October 2003; accepted 16 January 2004 Communicated by: Associate Editor Arturo Morales-Acevedo Abstract This paper presents a method for estimating the loss-of-load probability (LLP) of a photovoltaic water pumping system. The study has been carried out for a constant profile, using a tank with a two day autonomy capacity and two pumping heads applied to a centrifugal pump. The method developed in this paper gives a simple tool for LLP cal- culation. The procedure can also be used to draw LLP maps with normalised parameters using long term observed or generated sequences of meteorological data. This technique gives a generalised and practical graphical tool for systems sizing. Some examples from Algeria are used. But the method can be applied to any geographical area. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Loss-of-load probability; PV pumping; Simulation 1. Introduction Water pumping is an important factor in the devel- opment of rural and remote areas in developing coun- tries. In this case, photovoltaic (PV) energy is much more suitable for the application. This is because solar radiation is generally high in arid zone locations where the water is most needed. The particular system investigated in this paper is a solar pumping system consisting of a photovoltaic array, a direct current (DC) motor and a pump. Pumping water into a storage tank during high insolation periods can conveniently solve the problem of availability of photovoltaic systems in this case. In theory this is an almost ideal application of photovoltaic cells and has been the subject of many research papers (Posorski, 1996; Hadj Arab, 1999; Hsiao and Blevins, 1984; Langridge et al., 1996). In order to minimise capital costs, it is necessary to match the load characteristics with the PV array char- acteristic. This can be achieved either by including a maximum power point tracker in the system or by appropriate selection of the motor constants, based on optimising the system output as an optimal combination of parallel and series cells (Koner, 1995). Obviously simulation would be beneficial for design of such systems, as it would allow a range of system parameters to be varied. Many authors have used the loss-of-load probability (LLP) technique in order to optimise the PV systems (Morgan et al., 1997; Muselli et al., 1999). In this paper we present as a case study a method- ology applied to water pumping systems operating in different sites in Algeria. Various sizing configurations have been simulated and the iso-satisfaction curves have been determined. * Corresponding author. Address: Departamento de En- erg  ıas Renovables––CIEMAT, Avda. Complutense, 22, Madrid 28040, Spain. Tel.: +34-91-3466744; fax: +34-213-21-901654. E-mail address: hadjarab@hotmail.com (A. Hadj Arab). 0038-092X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.solener.2004.01.006 Solar Energy 76 (2004) 713–723 www.elsevier.com/locate/solener