Eusiel Rubio-Castro

Optimal design of integrated agricultural water networks

Abstract This paper presents a mathematical programming model for the optimal design of water networks in the agriculture. The proposed model is based on a new superstructure that includes all configurations in terms of use, reuse and regeneration of water in a field constituted by a number of croplands. The model also includes the allocation of pipelines, pumps and storage tanks in different irrigation periods. The objective function consists in maximizing the annual profit that is formed by the economic incomes owing to the crop sell minus the costs for fresh water, fertilizer, storage tanks, treatment units, piping and pumping. The proposed multi-period optimization problem is formulated as a mixed integer non-linear programming formulation, which was applied to a case study to demonstrate the economic, environmental and social benefits that can be obtained.

Solving the heat and mass transfer equations for an evaporative cooling tower through an orthogonal collocation method

Abstract In this paper, the orthogonal collocation technique is utilized to solve the Poppe method equations for heat and mass transfer in counter flowing wet-cooling towers. The six differential equations for unsaturated and supersaturated air from the Poppe method are simplified, yielding three differential equations that use the Heaviside function. The humidity ratio is demonstrated to be a finite power series at a normalized water temperature. The air enthalpy is expressed as a function of the normalized water temperature and the unknown coefficients of the expansion from the humidity ratio. The discrete formulation is solved using the Newton–Raphson method using an explicit Jacobian. The proposed methodology is applied to eight examples, and the results are compared to the results obtained when the governing equations are integrated with the Dormand–Prince method. The results indicate that the accuracy is similar between both techniques. However, the orthogonal collocation requires less CPU time.

Optimization of biofuels production via a water–energy–food nexus framework

Biofuels have emerged as an attractive renewable alternative to satisfy the global energy demands. The large-scale production of biofuels requires the installation of biorefining systems that involve strategic decisions for the logistics and operation in the production of biofuels such asxa0location, feedstock type(s), production capacities and interactions with the surrounding environment. This work proposes an optimization framework for the design of a biorefining system while accounting for the interactions with the surrounding watershed using a material flow analysis technique through the design of an efficient supply chain for the production and distribution of feedstocks, grains and biofuels considering the water and land requirements. The proposed model deals with the uncertainty involved in the project (e.g., prices of feedstocks and products, biofuel demands and precipitation in the watershed). A mixed-integer linear programming model is proposed to simultaneously consider the economic and environmental objectives. A case study located in Mexico is solved for a set of scenarios with the purpose of illustrating the capabilities of the proposed optimization approach. The results show strong trade-offs between the considered objectives and the impact of uncertainties.

Optimal design of water networks for shale gas hydraulic fracturing including economic and environmental criteria

This work proposes an optimization approach for designing efficient water networks for the shale gas production through the recycle and reuse of wastewater streams reducing the freshwater consumption and effluents considering economic and environmental goals. The economic objective function aims to minimize the total annual cost for the water network including the costs associated with storage, treatment and disposal (capital cost) as well as freshwater cost, treatment cost and transportation costs. The environmental objective is addressed to deal with the minimization of the environmental impact associated with the discharged concentration of total dissolved solids in the wastewater streams and the freshwater consumption through an environmental function that represents the benefit for removing pollutants using the eco-indicator 99 methodology. The methodology requires a given scheduling for the completion phases of the target wells to be properly implemented by the available hydraulic fracturing crews during a time horizon. The model formulation is configured to determine the optimal sizes for the equipment involved by the project, particularly the sizes for storage and treatment units are quantified by the optimization process. A case study is solved to evaluate the effectiveness of the proposed optimization approach.Graphical abstract

Optimal design of total integrated residential complexes involving water-energy-waste nexus

This paper presents a multi-objective optimization formulation for enhancing the sustainable development of a residential complex. The approach accounts for the water-energy-waste nexus of the complex and enables various pathways for system integration. For conserving the fresh water demands, the proposed model includes the synthesis of water networks while accounting for wastewater reclamation and recycle and rainwater harvesting. The proposed model also incorporates the optimal design of a residential cogeneration unit to satisfy the demands for electric power and hot water. An absorption refrigeration system is considered to utilize waste heat and provide the needed refrigeration. The emitted carbon dioxide is fed to an algae growth system, which is integrated with the use of reclaimed water. A solid-waste gasification system is considered to provide electric power and heat to the residential complex. The optimization approach accounts for all the interactions of the involved units and for the seasonal variabilities of the system. A case study for a residential complex of Mexico is solved.