Energy efficiency analysis of all-variable chilled water based air-conditioning system

In past several years, due to technology advancements, the costs of variable speed drives have come down sharply allowing the widespread applications of variable speed devices in building air-conditioning systems. This article presents the case study on application level of variable speed drives to the components of the air-conditioning system (VAV system) installed in Vivekanand Lecture Theatre Complex (VLTC) at MNIT Jaipur, India. After incorporating the variable speed drives to the air conditioning system, the proposed case energy performance index has been compared with the standard energy performance indexes of Energy Conservation Building Codes 2017(ECBC, ECBC+ and Super ECBC), developed by the ministry of power and Bureau of Energy Efficiency(BEE), India. The study of Hartman research paper on variable speed chiller plants has been used to learn existing algorithm for developing new operating strategies. Simulations are performed on EnergyPlusV8.8.0 (an energy analysis simulation program) for more than dozens of cases by making the variable a single and multiple combinations of HVAC equipment (AHU, Cooling Tower, Chiller, Pumps). The results show that the application of variable speed drives improved the performance of the air conditioning system substantially. At an average, the energy consumption of all variable chiller plant decreased by 40-45% compared to a constant speed chiller plant. All-variable speed chiller plant operating strategies have been developed based on the tailored specific performance characteristics of variable speed chillers and the variable flow characteristics of condenser pumps and cooling towers. The specific component-wise energy performance improvement after the incorporation of variable drives and ECBC compliance check for the proposed case has been presented in this paper.