Water distribution and power transmission networks are thought of as separate uncoupled infrastructure systems. In reality, they may be viewed as a single system which may be called the energy-water nexus. In hot and arid climates, this nexus takes on a deeper meaning in terms of the economic dispatch of power, water and cogenerating desalination units.This paper represents a co-optimization framework for the economic dispatch of water and electric power. In particular, an optimization program is provided that minimizes total costs as a function of power and water generation subject to demand, capacity and process constraints. It is distinct from existing literature in that it focuses on the simultaneous optimal operation of all plants within the power and water delivery networks within a generalized mathematical formulation. The optimization was then demonstrated on a hypothetical system composed of four power plants, three cogenerators and one pure water plant. Interesting results were observed suggesting that the cogenerator minimum capacity limits and process constraints can lead to scenarios where cheaper single product plants can be crowded out of the dispatch.The program provides a systematic method of achieving optimal results and can serve as basis for set-points upon which individual plants can implement their optimal control.
Clean energy and water are two essential resources that any society must securely deliver. Their usage raises sustainability issues and questions of nations' resilience in face of global changes and mega-trends such as population growth, global climate change, and economic growth. Recently, attention has been paid to the infrastructure systems for water distribution and power transmission and the coupling between them in what is commonly known as the energy-water nexus. Although numerous policy and regulatory agencies have addressed the subject, rarely is it holistically addressed in terms of an integrated engineering system for its management, planning, and regulation as an interdisciplinary concern. This work specifically addresses the supply side of this integrated engineering system framework. It takes as its subject the real-time optimal flows in power and water networks. Significant background literature is brought to bear on this topic including the emerging co-dispatch of power and water and the more well established optimizations for power and water networks individually. The work presents a mathematical optimization program for the co-dispatch of the two commodities for three types of plants: power generation plants, co-production facilities and water production plants. Production costs are minimized subject to capacity, demand and transmission constraints and demonstrated on an illustrative example of modest size developed from standard test cases. On a practical basis, the program can be applied directly in middle eastern countries where water and power distribution are typically under the responsibility of a single utility. Furthermore, the program provides a systematic method of achieving optimal results and can serve as a basis for set-points upon which individual plants can implement their optimal control. In so doing, it makes a supplyside contribution to the ongoing grand-challenge of improving the sustainability of the energy-water nexus.
Recently, the production and consumption of energy and water resources and their potential coupling in what is often called the energy-water nexus has gained attention as an issue of global concern[1, 2]. Ultimately, a significant amount of water is required to produce energy and vice versa [2, 3]; motivating the need for co-optimization based approaches for the two resources. Recently, one such simultaneous co-optimization method has been contributed for the economic dispatch of networks that include water, power and co-production facilities [4]. That study showed that capacity and process constraints often limit total production cost. This paper seeks to add plant ramping behavior as potentially binding constraints and investigate the impact of water and storage facilities as a technology that can help alleviate binding constraints and lead to more levelized production and cost levels. The paper builds upon the optimization program provided in previous work [4] to develop two optimization programs with and without storage facilities and compares their respective results. Storage facilities are shown to reduce total operating costs and lead to more levelized daily production suggesting that they have an important role to play in the optimization of the energy-water nexus.
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