Preliminary experimental analysis of a small-scale prototype SWRO desalination plant, designed for continuous adjustment of its energy consumption to the widely varying power generated by a stand-alone wind turbine

Abstract

Given the significant water-energy problems associated with many remote and arid areas of the planet, most studies, projects and developments of installations for the production of fresh water using desalination technologies powered by renewable energy sources have focussed on small-scale stand-alone systems. The most commonly used energy sources have been solar photovoltaic and wind and the most widely applied desalination technology that of reverse osmosis (RO). Most of the systems use batteries as a means of mass energy storage and the RO plants normally operate at constant pressure and flow rate. This paper presents a small-scale prototype SWRO (seawater reverse osmosis) desalination plant designed to continuously adapt its energy consumption to the variable power supplied by a wind turbine (WT), dispensing with mass energy storage in batteries and proposing the use of a supercapacitor bank as a dynamic regulation system. A description is given of the tests performed to date with the SWRO desalination plant connected to the conventional grid while controlling the number of pressure vessels that are connected/disconnected to/from the system and regulating their operating pressures and flow rates (within predetermined admissible limits) to maintain a constant permeate recovery rate and adapt the energy consumption of the plant to a widely varying simulated wind energy supply.One of the most important conclusions that can be drawn from the studies undertaken is the feasibility of adapting the consumption of the prototype of the SWRO desalination plant to widely varying WT-generated power. Despite using various time interval lengths in which it was assumed that the WT output power remained constant, a perfect fit was not obtained between the theoretical WT-generated power and the power consumed by the SWRO desalination plant, nor was it possible to maintain a constant permeate recovery rate at each instant.