Optimisation of an hvac system for energy saving and thermal comfort in a university classroom

In university classrooms with air conditioning systems, as well as in conference rooms, thermo-hygrometric and air quality requests must deal with high energy consumption of the plant system. The whole plant management is sometimes critical due to the particular conditions of use of the rooms where the ventilation rate demand and thermal loads may change consistently during daily occupation. In this work an existing HVAC system unit is analyzed, serving two classrooms with a single zone distribution. The HVAC system is set to work with an external air supply at a constant rate, and includes air treatment sections with heating, cooling and vapour humidification. Experimental measurements of both thermal comfort parameters and real operating conditions of the HVAC unit gave information about critical aspects of the whole building-plant system design and management. In this work an energy dynamic simulation of the building-plant system using Energy-Plus software has been realized. After a proper calibration of the model based on experimental measurements, a dynamic simulation is used to carry out plant management strategies (e.g. free cooling, variable set points for intermediate occupational condition, mixing of the external air with recycled air, etc.) that combine energy savings with better indoor comfort. Several design alternatives are modelled through Energy-Plus to predict energy performance improvements associated with a different set of HVAC system configuration. Simulation results indicate up to 60% energy savings.