Employing chemical processes as grid-level energy storage devices : demand response and frequency regulation

Reliable operation of the electric grid which comprises of instantaneously matching electricity demand and supply is a tier one security concern and has received increased attention in recent years. This is a challenging task as both electricity demand and supply are characterized by variability and uncertainty; the volatility on the supply end originating from increased integration of renewable energy in power generation. Electricity demand typically peaks in the late afternoons whereas wind and solar generation peak in the early mornings and mid-day respectively. To reconcile this electricity supply and demand mismatch, energy storage is employed for storing excess power generated during off-peak demand periods. Correspondingly, stored power is discharged during peak electricity demand hours. Electricity storage is however presently expensive and current grid storage devices are insufficient to ensure reliable electric grid operation. Standby generators with fast ramp rates which are generally more expensive to run are also employed when needed. A solution to this problem involves motivating end-users of electricity to modify their demand patterns in manner that enhances grid stability. This activity, referred to as demand response (DR) can help relieve the strain on the grid by tailoring end-user power consumption to match the time varying supply of electricity. Chemical industries that are power-intensive can provide valuable DR as they represent localized grid loads with end products that are generally easier and cheaper to store compared to electricity. These industries can ramp production during off-peak power demand hours storing excess product and reduce production rates when power demand peaks while depleting inventory to meet any required product demand. However, the operation of chemical industries are subject to strict constraints including; economic (e.g., reliable product delivery), feasibility (e.g., limits on process variables) or safety concerns. Additionally, the dynamics of chemical processes are typically described by high-order non-linear models and ramp rates and capacity limits alone, which are typically employed on the grid side to manage demand response activities, are not sufficient to characterize the transient nature of chemical processes. In this dissertation, we employ modeling techniques and production scheduling to evaluate the provision of demand response by chemical industries in highly volatile electricity markets. We develop and illustrate the use of suitable dynamic models to represent the chemical plant operation while providing fast-paced DR. As fast DR contribute significantly to the solution pool available for handling power grid contingencies, this study will aid the smoother deployment of industrial chemical loads as grid support devices while ensuring safe and feasible operation of the chemical plant.Chemical Engineerin