The essential connection between energy and water, also defined as the energy-water nexus, has been recognized by scientists and policy makers worldwide. Integrated solutions and policies that consider both energy and water aspects into future planning have been developing at a fast pace. In this paper, we review the state of the art of the energy-water nexus, with particular focus on the integration between renewable energy and desalination technologies. We also model the integration of reverse osmosis (RO) desalination and solar photovoltaics in an edge-of-grid coastal town in Western Australia.
The current literature agrees on the sustainable use of renewable energy sources to improve the water-energy nexus in the context of water desalination. Although the integration of solar and wind energy with desalination technologies is a mature and well-proven solution at both small and large scales, the intermittency and fluctuating nature of wind and solar power still constitute the main technical challenge that has limited the diffusion of renewable energy powered desalination on a large scale. Several successful applications of renewable energy powered desalination in remote, off the grid, locations have tackled the issue of power intermittency by the use of batteries and diesel generators. Such systems often couple reverse osmosis desalination with solar photovoltaic energy. Large desalination plants have been successfully connected to wind farms and grid electricity to secure uninterrupted plant operations, thus meeting water targets in large-scale systems. Our review identifies a knowledge gap in the integration of decentralized energy systems, e.g. rooftop solar photovoltaic, with small scale RO desalination. Such configuration would benefit those regional towns that have historically suffered from weak and unreliable connections to the electricity grid, thus helping them secure both their energy and water requirements.
The modelling exercise on a renewable energy powered RO plant in an edge-of-grid town in Western Australia has identified an operating strategy that maximizes the renewable energy fraction and secures the annual supply of water. The system involves operating the RO unit for six months of the year at a daily variable load and integrating solar energy with grid electricity. Careful evaluation of the RO performance under such operating conditions is necessary to ensure a safe and reliable water treatment process.
A niche in the literature of the energy-water nexus has been identified in the integration of rooftop solar photovoltaic, grid electricity and desalination technologies applied in a regional context. A future study will consider the rollout of rooftop solar photovoltaic installations across the whole town, thus enabling the active engagement of the community by integrating the households’ energy demand response patterns to the operations of both rooftop photovoltaics and the desalination unit
