Potential role of renewable energy in water desalination in Australia

With projected increases in population and urbanisation in Australia, the sustainable supply of water and energy over the medium to long term will be an important challenge. In this context, meeting a part of the growing demand for urban water may involve reliance upon desalinated water in the future. Moreover, the feasibility and viability of renewable energy sources for water desalination will be of policy importance, particularly in a potentially low carbon Australian economy. In this article, we analyse the potential applicability of solar and wind energy to provide power for water desalination. In two illustrative examples, we assess the feasibility of supplying 3% of Sydney's projected total water consumption (supplied at an average rate of 24.7 Gl/yr) and 5% of Sydney's projected water consumption (supplied at an average rate of 32.7 Gl/yr) over a 15-yr period (2011-2025) using a photovoltaic (PV) solar powered (130 MW) and a hybrid (PV solar and wind energy) powered (205 MW) reverse osmosis (RO) desalination plants, respectively. In addition to supplying cleaner energy, the renewable energy sources considered in this article have additional cost advantages in the presence of a carbon penalty. For example, at hypothetical carbon penalty rates of $20/tCO 2 and $30/tCO 2, the estimated cost savings-in net present value (NPV) terms assuming a discount rate of 4.2%-of the PV solar (hybrid) plant will amount to around be $18.7 m ($25.2 m) and $28.0 m ($37.9 m), respectively, over the 15-yr period, relative to a situation where the desalination plant is instead being powered by black coal. Under a discount rate of 8.4%, the cost savings of the PV solar (hybrid) plant associated with carbon penalty rates of $20/tCO 2 and $30/tCO 2 are estimated to be around $12.8 m ($17.6 m) and $19.2 m ($26.4 m), respectively, in NPV terms. Our analysis also shows that in addition to providing the required power supply for the illustrative desalination plants, the renewable energy supply sources analysed here would produce excess electricity that could be sold to a nearby grid. Consequently, assuming a wholesale electricity price of $36.74/MWh, the PV solar plant and the hybrid renewable plant are estimated to have the capacity to earn around $63.9 million and $110.0 million in NPV terms, respectively, over the 15-yr period, through excess electricity sales. Under a discount rate of 8.4%, the value of the excess electricity sales of the PV solar plant and the hybrid renewable plant are estimated to be around $54.5 million and $91.7 million, respectively, in NPV terms.