(640e) Optimal Design and Operation of Flexible Energy Polygeneration Systems

Energy polygeneration systems with multiple feed stocks and multiple products in a single plant have economic advantages over conventional single-product systems and are of increasing interest to the energy industry. Most current research on polygeneration systems design focuses on the design of static (fixed capacity) systems under assumed annual average product prices. However, product prices can fluctuate significantly seasonally or even daily (e.g., the power price in the daytime is usually much higher than at night). The profitability of the polygeneration system can potentially be increased if some operational flexibility is introduced, such as adjusting the product mix dynamically in response to changing market prices. The major challenge of this flexible design is the determination of the optimal trade-off between flexibility and capital cost because higher flexibility typically implies both higher product revenues and larger equipment sizes.

In this work, we present a two-stage optimization formulation for flexible energy polygeneration systems that simultaneously optimizes design decision variables (e.g., equipment sizes) and operational decision variables (e.g., production rate schedules) in several different market scenarios to achieve the best expected economic performance. Using GAMS, we determine that for most of market scenarios, flexible polygeneration systems achieved higher expected net present values (NPV) than static polygeneration systems. Furthermore, even higher expected NPVs could be obtained with increases in flexibility.