| With the rapid growth of global population and economy,demands of water and energy resources are gradually increasing.Due to the close interactions between water and energy,in order to improve resource utilization efficiency and achieve sustainable socio-economic development,water-energy nexus analysis and management have attracted more and more attentions recently.In this thesis,the interdependent,restrictive and synergistic relationships between water and energy are firstly introduced.The necessity of water-energy nexus planning and management is pointed out.An integrated optimization method has been proposed for planning and management of the regional water-energy nexus system,which entails a Nonlinear Mixed Possibilistic-Flexible Robust Water-Energy Nexus model(PFRWE)and a Reginal Scale Graph Theory-Based Bi-Level Integrated Water Network Planning model(GBWN).Optimal decisions can be obtained for planning construction of water and power plants,production management of water and energy system and pipeline network layout planning.PFRWE model is developed to realize sustainable management of water and energy resource under decision-makers who have different attitude to risk and environment protection.The GBWN model is developed for water pipeline network layout planning with tradeoff between energy saving and cost decreasing.The PFRWE model has improved upon the existing water-energy nexus management methods through incorporation of fuzzy flexible programming,fuzzy possibilistic programming,robust programming and mixed integer nonlinear programming into a general framework.It can deal with not only fuzzy uncertainties in the modeling parameters and the constraints,but also the robustness of the model and the solutions by introducing feasibility robustness and optimality robustness.The GBWN model represents an integrated water network planning method by combining graph theory and bi-level programming to make decisions on reginal-scale water plants construction,user partitions,pipeline layout,and pipe load.It not only has the advantages in dealing with spatial network layout but also can address the bi-level decision making issues.The upper-level management objective is minimizing construction,maintenance and operation costs while the lower-level objective is minimizing electricity consumption during water supply process.The developed PFRWE and GBWN models are applied to regional water-energy nexus planning and management case studies.The PFRWE model is employed to manage water and energy system in Liaoning Province,China.The GBWN model is applied in a hypothetical case to show the results.Through the results,main form of power generation in Liaoning Province is transforming from coal-fired to nuclear power generation.Water resource is mainly surface water.Sea water desalinated plants do not have market advantages due to high energy consumptions and costs.From the perspective of sustainable development and for better reducing the impacts of potential water shortages on the power system,more clean energy power plants and power plants with desalination systems should be built.In order to improve resource utilization efficiency and reduce environmental pollution,it is necessary to develop recycled water.The PFRWE model can effectively balance tradeoffs between economic benefits and eco-environmental protection requirements.As the optimal robustness increases,it will reduce the economic risks,resource consumptions and total profits of the water-energy system;as feasible robustness increases,the decisions will be more conducive to environmental protection and resource conservation,but has disadvantages on the increase of total profits.The results of GBWN model show that only intermediate water plants are planned for construction,and the pipe network will be symmetrically distributed under only economic objective.The construction and maintenance costs of pipe networks and water plants are low,but electricity consumptions are high.The solutions from the GBWN model are not conducive to the long-term social development.That’s since the city has a high altitude in the south and a low altitude in the north,and the water plants on both sides will be constructed under only energy objective for better using the gravitational potential energy to supply water.However,the solution may be rejected be upper-level decision maker due to dissatisfaction with total cost.The GBWN model can better balance the needs of economic efficiency and energy saving in the process of water network design and planning,and improve energy efficiency within the tolerance of upper-level decision-makers.The solutions will improve the overall satisfaction of two-level decision-makers and save resources under the premise of saving economic costs.The PFRWE and GBWN models are helpful to improve the resource utilization efficiency of the regional water-energy nexus for socio-economic development by providing optimal decisions on water-energy system construction,production management and pipeline network layout. |
