A wave energy driven RO stand-alone desalination system: initial design and testing

Description/Abstract

Traditional desalination systems have high energy requirements which can be considered as the
limiting factor for their application. Using renewable energy sources for desalination of seawater
and brackish water can help to alleviate water scarcity in those areas with no electricity grid
connection or supply shortages. This paper describes the development of a stand-alone, off-grid
desalination system powered by wave energy. The device is designed to drive a reverse osmosis
(RO) membrane. No electricity is required. The system consists of two main parts; a high pressure
pump (WaveCatcher) that allows generation of a high pressure head from low head differences, and
a wave driven pump to supply the necessary head to the WaveCatcher. The high pressure pump is
designed to produce 6 MPa of pressure which is necessary to drive a RO membrane for desalination
of water. A 1:6 scale physical model was built and tested; pressures of 42 m were achieved from an
initial pressure head of 0.2 m. Delivery of water to the WaveCatcher is to be achieved through the
use of an oscillating water column (OWC) pump. The pump consists of a two-part resonant duct,
which allows resonance control by varying the angle of the output duct. Maximum lift heights of
five times the wave height were reached. The initial experiments showed that the WaveCatcher
can generate the necessary pressure to run the RO membrane for the production of drinking water
without the use of electricity.