Optimization Frameworks for the Design, Synthesis, Supply Chain, and Strategic Planning of Novel Hybrid Energy Processes

Abstract

Increasing demand for transportation fuels in the United States and efforts to reduce reliance on petroleum imports put pressure on the development of domestic energy sources such as coal, biomass, and natural gas. Coal and natural gas have lower costs than biomass, but biomass can reduce the greenhouse gas emissions during cultivation. Hybrid energy systems that synergistically combine these feedstocks can yield competitive economic and environmental performance with petroleum-based processes. This research develops frameworks for the design, synthesis, supply chain, and strategic planning of novel hybrid energy systems using mathematical modeling and optimization approaches. The developed process thermochemically converts coal, biomass, and natural gas to gasoline, diesel, and kerosene (CBGTL). The optimization framework is developed on two levels, the design of a stand-alone refinery and the identification of an optimal supply chain network. The conceptual design of the CBGTL process is first simulated, integrated and economically evaluated. In a process synthesis framework, the design is expanded into a superstructure that includes multiple technologies and the topology is optimized to give the lowest overall cost of fuel production. Simultaneous heat, power, and water integration is incorporated into the model and a rigorous deterministic global optimization strategy is applied to guarantee valid lower and upper bounds on the optimal solution.

Given the individually optimized refineries, a supply chain framework is developed to identify the optimal locations and capacities for the refineries with respect to the the feedstocks, demand, water resources, electricity requirement, and CO2 sequestration profiles, to replace petroleum fuels in the United States. The framework can be applied to single feedstock energy supply chains, adapted for a ranking methodology, and solved for various geographical scopes. A multi period strategic planning model is also developed for the supply chain problem. On both the single plant and supply chain level, solutions from the models elucidate economic and environmental trade-offs between multiple scenarios. Results suggest that high quality fuels from domestic sources can be produced in an economically competitive manner compared to petroleum fuels, with better environmental performances (i.e., lower life cycle emissions) when biomass is included.