Modelling the water-energy-nexus to assist the design of economic and regulatory support instruments towards sustainability

Due to climate change, an increasing number of countries face stress on their renewable water resources. On the other hand, energy systems that reduce dependency on fossil fuels and help transition to green systems, cause problems that need to being dealt with, such as the inherent fluctuation of renewable energy resources and its resulting instability. Redesigning the water and energy sectors in such countries is unavoidable - offering both opportunities and threats for the future. The country chosen as case study, Iran, is facing acute stress on fresh-water resources and its energy system mostly relies on fossil fuel. This study considers the role of water-energy-nexus in designing technical aspect of a future system with a higher share of renewable energy supplies and lower excess water extraction. The excess water extraction refers to the difference between the amount of water extraction and outlet from the underground and surface water resources, and the amount of water returns to these resources. A supply-demand model is developed in order to design a system with both renewable resource technologies and water desalination technologies in water and energy sectors. The key point of this research is that synergies and technical effects of modeling water and energy sectors are studied as both integrated and separated models on the technical shape of the system. The synergy term in this study is defined as an outcome which is achievable with less cost or complexity when the linkages among systems are considered.