Enabling Distributed Renewable Energy and Chemical Production through Process Systems Engineering

Abstract

New renewable energy technologies offer the promise of preserving a sustainable energy supply for future generations. Coupling chemical production with renewable energy production can help to address many of the challenges associated with the large-scale implementation of renewable energy, including short time scale variability of electricity production, potential mismatch of supply and demand, and energy stranded in areas of low population density. However, such co-production systems necessitate considering chemical production at scales smaller than what is typically seen in today's infrastructure due to the geospatially dispersed nature of renewable energy resources. This small scale production is economically prohibitive due to economies of scale, which promote building large scale facilities whenever possible. These economic challenges motivate the use of process systems engineering to develop decision making frameworks which minimize the costs of building and operating new renewable energy and chemical production systems. The application of process systems engineering methods to systems producing renewable energy and chemicals presented in this thesis centers around three major themes. First, decomposition, an approach which breaks down large optimization problems into smaller, easier to solve subproblems, is used to solve a challenging problem which finds the optimal design of a combined biorefinery and microgrid system. By doing so, hydrogen production is identified as a critical cost bottleneck in the combined system design. A method for automatically finding subproblems for decomposition for a broad class of optimization problems is also presented. Second, a framework is proposed for considering where new facilities should be built within an existing chemical supply chain. Here, policies and market conditions, such as a carbon tax, are identified that can have a strong effect on reducing emissions from ammonia production. Finally, the connection between the optimal design and operation of renewable energy and chemical systems is analyzed. Here, a framework which determines operating strategies which minimize cost is developed, and the optimal operation of a wind-powered ammonia system in different electricity market structures is analyzed. This framework is used to generate correlations between system design and operating cost which are embedded in a design optimization problem to improve solution efficiency.