A framework for HVAC control at a tertiary institution

Abstract

Most utility's and electricity resellers stimulate changes in their load shape through various demand side management activities. The most common way of altering their load shape is through the implementation of different tariff structures. The thesis investigates the effect of combining hot water load control with heating ventilation and air-conditioning load control to reduce the electricity costs due to a demand tariff that is a direct result of demand side management. The entire study is focused on the demand tariff of the University of Pretoria. Although the study was done on the University of Pretoria the methods developed are universal and can be implemented in any situation where hot water load control and heating ventilation and air-conditioning load control are to be combined. The study presents a detailed literature study on the current developments in the field of hot water and heating ventilation and air-conditioning load control. No current work could be found in which the two control methods are combined. Models were developed for controlling the electricity load and for determining the savings. The heating ventilation and air-conditioning load's and the hot water load's uncontrolled load models respectively had a mean absolute percentage errors of 3.83% and 3.2%. The forecasting method used to determine the available energy for pre-cooling and the start time of shedding had a mean absolute error of 3.2%. A case study of the University of Pretoria was done. The effect of using only hot water load control is presented. The case study was expanded to include structural thermal energy storage and then water thermal energy storage. This expansion was done using the HV AC system in combination with the hot water load control system. With an only 10.3% contribution to the university's maximum demand, the hot water load control reduced the university's electricity account (energy + demand) by 5.44%. The heating ventilation and air conditioning load contribute to 6% of the university's maximum demand. With the structural thermal energy storage using the heating ventilation and air conditioning system, the savings increased to 6.12%. With the addition of a 750m3 water thermal energy storage tank to the heating ventilation and air-conditioning system, the savings increased to 7.14%.