Co-ordination Action for Autonomous Desalination Units ... - ADU-RES

4.3.3 PV-RO plant for brackish water desalination in Brazil
a. Introduction
The PV RO plant was installed in the community of Coite-Pedreiras, in the state of
Ceara, Northeast Region of Brasil in 2000. The selected community has a population
of about 150 families. The main water resource of the village is a well with a salinity
of 1200 ppm TDS. The region is characterized by a high yearly solar potential of
about 2000 kWh m -2 y -1 . The project was financed by the Banco do Nordeste and
CNPq and developed by the DEE-UFC in cooperation with ARCE and CEFET in
Brazil [Paulo Cesar Marques de Carvalho, 2004].
The aim of the project was the investigation of the coupling of the two technologies
Reverse Osmosis and Photovoltaics for brackish water desalination considering two
strategies: the first concerns with the use of a dc motor and secondly the use of a
three-phase induction motor. Through the analysis of the stored data the second
option is chosen as the better alternative.
b. System Description
The plant consists of 20 PV modules of 55W each, totally 1.1kW, 8 batteries of 12V,
100 Ah and a charge controller. The RO unit has a water capacity of 250 l/hr. The
pressure of operation of the RO unit is of about 8 bar working in a recovery ratio of
27%. The plant is equipped with sensors for measuring the followings:
• Global solar radiation
• Ambient temperature
• Module temperature
• Wind speed
• Water flow
• Direct voltage of the PVs and batteries
• Direct current of the PV s and batteries
In the first case, the power from PVs drives only the high-pressure pump of the RO
unit, which is the main load. The grid drives the booster pump. The dc motor used at
the RO unit has a nominal power of 750 W and a nominal voltage of 24 V. The
configuration of the PV-RO system is shown in Figure 14.
WP2 ADU-RES 47