An optimal integrated power and water supply planning model considering Water-Energy-Emission nexus

Water and energy are the major factors in the new United Nations Sustainable Development Goals. Sustainable conversion and management in the secure supply of increasing demand for water and electricity is a challenging concern. It is recently complicated due to economic development, population growth, resource depletion, and climate change, which requires a simultaneous progressive planning. Since energy and water systems are instinctively interdependent and mutually interacted (known as nexus), this paper employed an integrated solution-based method. A bottom-up optimization model is developed considering Water-Energy-Emission Nexus approach for both power and water sectors. The model minimizes the economic costs subjected to techno-economic constraints and socio-environmental requirements. An innovative multi-dimensional index called Water-Electricity Nexus Index is presented to assess how water and power sectors are interdependent. The model is applicable for any region and the results for a real case show that the nexus index is increasing remarkably ([7.6, (3.3, 47.7) ] changes to [12.3, (3.7, 55.0) ]) if the current situation continues for both sectors in the Business -As-Usual scenario. It means the two sectors are interweaving more in the coming years, which will make planning and security provisions difficult. The nexus of electricity for water sector increases by about 60 % and although the share of water withdrawal for power sector is 3.7 % in the region, the total water withdrawal is much more (55 % over the life cycle considering virtual water). Hence, several scenarios are defined to depict future transition pathways and optimal strategies considering demands, prices, taxation policy, restrictions, and technological efficiency. The results show that rapid economic growth scenarios are not sustainable transition pathways (i.e. the nexus index changes to [16.1, (20.8, 112.0) ] and [16.1, (20.3, 47.7) ]). Finally, it is concluded that increasing the renewable resource of power generation capacity between 22 and 40 %, improvement of the achievable technological efficiency in power plants from 25 to 50 percent, as well as demand-side management to keep the annual growth rate of electricity and water between 1.5 and 2.5 % and 1.1-1.5 %, imposing the carbon tax (5-75 $ton) and water tax (0.1-2 m3$) are the major drivers to reduce the nexus index. This framework provides significant insights to improve the integrated planning of water and power sectors in the regions for managers and authorities.