Optimization of a Combined Cooling, Heat, and Power Plant Design for Existing Central Utility Plants

Abstract

Cost and emission savings with load-following capability are essential factors in the design optimization of Combined Cooling, Heating, and Power (CCHP) systems. This thesis presents a methodology for evaluating CCHP system design options for large central utility plants to minimize operating costs and emissions. Central utility plants can be considered the backbone of large campus systems providing critical supplies such as cooling and heating energy. In this strategy, multiple Power Generation Units (PGUs) are considered to meet different load profiles annually to improve system utilization and resilience. The systematic process was applied to a case-study plant and identified the most economically viable CCHP design to minimize the annual total cost, including operation, maintenance, and utility costs, while also addressing redundancy issues. A Pareto frontier of design solutions containing wider total operational capacity is recognized using a mixed integer linear program algorithm. The final results of the case study showed that the CCHP system could achieve 23.8% operational cost savings and 30.2% and 60.7% in CO2 and NOx reductions, respectively. In addition, multiple PGU systems provide two percent additional cost savings compared to a single PGU system while avoiding downtime and increasing energy resilience. A sensitivity analysis indicated that utility cost fluctuation could drastically change the optimal operating cost. An increase in natural gas cost and a decrease in electrical grid cost can make the optimal design infeasible.