THERMAL-ELECTRIC MODELLING FOR INVESTIGATING AND EXPLAINING CVR IMPACTS ON AIR-CONDITIONING AND REFRIGERATION LOADS

Abstract

It has been suggested in literature and in industry that by reducing the incoming voltage at distribution feeder head or at commercial facilities (e.g., large grocery stores), significant electricity savings can be achieved. Such programs are normally called Conservation Voltage Reduction or CVR programs. The evidence for such assertions is primarily provided in terms of empirical energy consumption data before and after the introduction of the CVR programs. However, such data-based analysis does not explain the physics behind the reduction in energy consumption because of CVR. Electrical-thermal simulations that use high fidelity electrical and thermal models of a commercial facility, and the cooling equipment can explain the physics behind energy reduction because of a CVR program. These simulations can also quantify the sensitivity of energy reduction to differences in motors used and buildings’ construction without expensive and time-consuming data collection and analysis. The objective of the research presented in this dissertation was to develop a thermal-electric model of cooling processes using MATLAB’s SIMSCAPE toolbox that can be customized to consider different types of air conditioning and refrigeration systems, different building construction, different ambient weather conditions, and different building usage patterns to estimate the differences in electricity consumption with and without CVR. Simulation results show that while the coefficient of performance of cooling systems increase with reduction in compressor speed, the change in compressor speed under up to 10% voltage reduction from rated value is not significant (1.314%).