Optimisation and Implementation of Water Heater in Home Energy Management System

摘要

The purpose of this thesis is to analyze the water heater as an electric space heating in home energy management system using the newly installed water heater system in microgrid laboratory. The rise of decentralized power production from renewable energy sources and uncertainty in weather forecast induce the need to have controllable thermal loads such as water heater. This thesis focused on finding the time and water temperature relationship experimentally and integrating the water heater system to home energy management system.In the microgrid laboratory, a water heater system, consisting of a 1.8 kW water heater that has a capacity of 29 liters, two Pt500 resistance thermometers, an energy meter that displays water temperatures and volumetric flow rate, an air cooling system, a water pump and minimal hoses, is used to emulate real-life residential space heating behavior. A number of experiments are conducted to measure the water temperatures during heating and cooling period. The relationship between time and temperature is approximated using Least Squares Fitting method. The time to heat the water from 20.8oC to 55oC is around 70 minutes while the cooling time is around 8 hours.With those approximated solutions, the accuracy is further verified by alternating the heating and cooling sequences in different amount of time, such as 10 minutes, 15 minutes 20 minutes and 30 minutes. The comparison between calculated and measured water temperatures confirms that it is possible to calculate the water temperature based on the approximated solutions.The water temperatures are then extrapolated to 80oC for heating to find out the heat demand the air cooling system is able to provide. The integration of the approximated solution to the production following algorithm or HEMS shows that a redesign of HEMS is necessary in order to include water temperature as a new input for the algorithm. Furthermore, the communication of the water heater system to an external device using M- Bus communication protocol is documented.