Design and operation optimization of organic Rankine cycle coupled trigeneration systems

The utilization of organic Rankine cycle (ORC) technology is increasing rapidly due to its adaptability to various low-grade heat sources. This paper examines the economic and environmental performances of different trigeneration systems integrated with ORC unit based on different low/medium-temperature heat sources. By coupling the ORC unit to combined cooling, heating and power (CCHP) plant, solar collector and biomass boiler, three systems, namely, CCHP-ORC, Solar-ORC as well as Biomass-ORC are proposed. In order to realize the best performance of each integrated system, a mixed integer linear programming (MILP) model is developed to deduce the optimal system combination and corresponding operation strategies, from different preferences. As an illustrative example, the above three integrated systems have been assumed to cover the energy demands of two typical commercial buildings: hotel and office for a calendar year. Comparative analysis among the proposed three systems is implemented considering both economic and environmental objectives. The simulation results indicate that the Solar-ORC system has the best economic performance, whereas the Biomass-ORC system enjoys the best environmental benefit. In addition, the potential environmental benefits of the ORC unit are recognized be higher than the economic ones.