Variable-speed drives in photovoltaic pumping systems for irrigation in Brazil L. Roberto Valer a,⇑ , Teddy A. Melendez a , M. Cristina Fedrizzi a , R. Zilles a , Albemerc M. de Moraes b a Instituto de Energia e Ambiente, Universidade de São Paulo, Av. Prof. Luciano Gualberto 1289, CEP 05508-010 São Paulo, SP, Brazil b Programa de Pós-graduação em Energia – Universidade Federal do ABC, Av. dos Estados, 5001, CEP 09210-580 Santo André, SP, Brazil article info Article history: Received 20 April 2015 Revised 28 January 2016 Accepted 11 March 2016 Keywords: Photovoltaic pumping systems Variable-speed drive Productive use of energy abstract Thanks to recent technological advances and the falling price of photovoltaic modules, photovoltaic pumping systems (PVPSs) are more competitive for use in irrigation, especially in remote areas where other power sources are unreliable or unavailable. Nevertheless, several issues remain regarding the pur- chase, maintenance and replacement of PVPS components. One alternative for traditional PVPS configu- rations is the use of a variable-speed drive (VSD). The performance of this type of configuration was tested both at a pumping test facility and in the field at a variety of sites. The application of a variable-speed drive can enable the use of locally-manufactured pumps which are not necessarily designed specifically for photovoltaic applications, thus facilitating their replacement and maintenance. Furthermore, VSDs also enable the operation of pumps in power ranges higher than most commercial photovoltaic pumps. VSDs can thus potentially further improve the economic competitiveness of a PVPS, as shown by Life Cycle Cost analysis comparing a conventional (PVPS-C) and a variable-speed drive pumping system (PVPS-VSD). This paper examines these as well as other technical and economic aspects of the application of variable-speed drives for irrigation in Brazil. Ó 2016 Elsevier Ltd. All rights reserved. Introduction Access to energy is a catalyst for human development. In many rural locations where various barriers inhibit connection to the electricity grid and/or fossil fuel supply, solar home systems (SHSs) are used as a competitive alternative which to satisfy basic com- munication and lighting needs. Photovoltaic pumping systems (PVPSs) have also been employed for several years in such regions in order to facilitate access to drinking water, as well as for crop irrigation and animal husbandry. A report published by the World Bank has revealed that nearly 86% of the world’s population depends on rural agriculture for their livelihoods [1]. However, thousands of people live in places which are unsuitable for such activities due to having limited access to water and markets. Water scarcity has major consequences for human development, including limiting agricultural production, particularly in regions with low or irregular rainfall. Due to drought and the risk of losing production, many small farmers choose not to produce certain types of long-cycle crops (e.g. fruit trees) despite their high market value. One area that exemplifies this problem is the Brazilian semi- arid zone. Covering an area larger than Spain and Germany together, this region is characterised by poor rainfall distribution, with short and irregular periods occurring throughout the year (mean annual rainfall is less than 800 mm). As a consequence of high daily solar irradiation (around 6 kWh/m 2 ) and high tempera- tures (mean annual temperatures around 27 °C), the region also experiences a high rate of water evaporation (2000 mm/year). The combined effect of these factors is water scarcity during most of the year, which in turn results in most productive activities in the region being highly dependent on the existence of water infras- tructure (wells, dams, pipelines, etc.), or water supplied via water trucks or pumping systems. The use of photovoltaic pumping systems for irrigation can reduce this water limitation due to the complementarity between solar resource and crop irrigation needs. Periods of the greatest water demand coincide with those of highest solar irradiation and moreover, the regions with the greatest water needs are also those with the highest amount of available solar resources. Although modern photovoltaic pumping systems are now eco- nomically feasible [2–5], as happens when a new technology is introduced there are several issues that must be accounted for dur- ing project planning and design [6–8]. A recent research [9] that http://dx.doi.org/10.1016/j.seta.2016.03.003 2213-1388/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +55 11 30912657. E-mail addresses: robvaler@usp.br, robvaler@gmail.com (L.R. Valer). Sustainable Energy Technologies and Assessments 15 (2016) 20–26 Contents lists available at ScienceDirect Sustainable Energy Technologies and Assessments journal homepage: www.elsevier.com/locate/seta