Dynamic Simulation of a Micro-CHP Facility: A Case Study

Combined heating and power (CHP) systems are becoming increasingly popular because of their increased power reliability, thermal efficiency, and reduction of emissions. As with CHP systems, micro-CHP (micro-Cooling, Heating, and Power) system consists of power cogeneration system and thermally-activated components such as absorption chillers, water tanks, boilers, and air handling units. Although much work have been done on using steady-state models that follow load profiles to demonstrate the economic advantage of CHP systems, there has not been much work using dynamic simulation of CHP systems which include the transient response of the building along with the rest of the CHP components. This paper presents the results from the dynamic simulation of the micro-CHP system used to model the test facility at Mississippi State University (MSU) and discusses some important issues that were considered in obtaining a dynamic model. TRNSYS, a dynamic simulation program, is used as a simulation engine to evaluate the performance of the micro-CHP system with respect to transient heating, cooling, and electric power demand of the test facility. Details of the building model include geometric and material information, internal heat generation following the equipment and occupancy schedules, local weather information, and estimated infiltration of the test facility. The building model is connected to dynamic models of the power cogeneration system and thermally-activated components. In the test facility, a four-cylinder internal combustion engine with a 15-kW generator is operated to generate electric and thermal energy, and a 10-ton absorption chiller is used for space cooling.