Study on a fan coil unit and chiller by an intelligent control method with a stepless variable speed driving technology

Abstract

An energy saving method by variable air volume (VAV) and variable refrigerant volume (VRV) was proposed for application to the air conditioning system. According to the changes in thermal load, an intelligent control method with a stepless variable speed driving technology was also applied to the Fan-coil unit (FCU) and Air Cooled Packaged Water Chiller Unit (ACH), in order to achieve the optimized adjustment of air volume and refrigerant volume in real-time.A Brushless DC (BLDC) motor was used to regulate the air volume of FCU, and to control the percentage of output speed per 1%, in order to achieve the flexibility of adjusting the air volume of FCU. In the ACH part, the controller of ACH is to detect the returning air temperature to control the on and off state of ACH. In this study we propose the Stepless variable frequency and variable refrigerant (SVFVR) technique, mainly using a plug-in device attached to the ACH.The experimental results show that the measured long-term accumulated energy consumption of FCU was decreased from 4.5582 kWh to 2.888 kWh (the comparison between AC and BLDC motors), and the measured long-term accumulated energy consumption of ACH was decreased from 41.3 kWh (without SVFVR) down to 26.64 kWh (with SVFVR). The energy saving rate was calculated at 36.6% (energy saving rate for using BLDC) and 35.5% (energy saving rate for using SVFVR), respectively, to verify the energy efficiency of using the proposed stepless variable speed driving technology in FCU and ACH.