Solar Powered Desalination Could Bring a Revolution in Irrigation

Scientia Professor David Waite with the third generation MCDI that was built by CTET in China.

While conventional CDI uses mains power, UNSW researchers have developed prototypes powered by solar energy.

Scientia Professor David Waite with the third generation MCDI that was built by CTET in China.

Agriculture relies heavily on groundwater and this source of water is rapidly becoming increasingly saline across the world, making it non-viable for agricultural purposes.

To combat this issue and make fresh water readily available to the farming sector irrespective of the quality of the local groundwater supply, University of New South Wales’ (UNSW) Global Water Institute (GWI) is developing an innovative, solar-powered version of a desalination technology called Capacitive Deionisation (CDI).

The technology has significant potential to revolutionize irrigation and ensure that the world can continue to meet its growing food production demands and, in doing so, protect it against food shortage during drought. CDI removes salt from brackish water by passing water through a stack of electrode pairs with positive ions such as sodium attracted to the cathode and negative ions such as chloride attracted to the anode. When a voltage is applied across the electrodes, a desalted stream of water is produced.

While conventional CDI uses mains power, UNSW researchers have developed prototypes powered by solar energy. These solar-powered CDI units are an energy-efficient alternative with low operating voltage and the possibility of energy recovery, making it ideal for brackish water desalination, especially in remote locations where mains power may not be available. The units are also really easy to maintain, which makes the technology even more suited for use in remote-off grid communities.

The idea for the project was born when Ratan Tata visited UNSW to receive an honorary doctorate and challenged researchers to help find ways to provide clean water for Indian villages. Scientia Professor David Waite from the School of Civil and Environmental Engineering accepted the challenge and, with support from Professor John Fletcher from the School of Electrical Engineering and Telecommunications, constructed the first solar-powered prototype.

Second and third generation units, in which energy usage was reduced by recovering a portion of the energy used, have been constructed with funding from an ARC Linkage grant with industry support by Goldwind Environmental Technologies, a Beijing-based company that is the largest manufacturer of wind turbines and is now expanding into the development of water technologies.

“For this project, we innovated in both the mode of operation of the established technology of membrane capacitive deionization (MCDI) and the use of solar energy combined with energy recovery to power the device,” said Professor Waite, Executive Director of UNSW Centre of Transformational Environmental Technologies (CTET).

Professor Waite says that providing dependable water supply options to the agriculture industry that are cost-effective, can function independently of the electricity grid and do not carry a significant environmental burden is essential for Australia’s and for the World’s future food security.