Design and development of an automatic solar water heater controller

In a solar water heating system, the most frequently met difficulty is to obtain the hot water at a required temperature continuously due to variation in the incident solar radiation over a day or even in the different seasons of the year. This work deals with the designing of a control mechanism based on the sensed temperatures, along with the water flow rates from the two systems, primary (hot water source) and secondary (cold water source), which are continuously monitored. This mechanism proposes a solution to the problem of obtaining warm water at a desired temperature and fulfilling the temperature specific activities as it estimates the amount of cold water to be supplied from the secondary source. Further, the energy consumption can also be reduced by implementing a hybrid mode (using a solar water heater and an electric heater), where the water will be preheated by the solar water heater. As a result, the electricity expenses of the electric heater can be curtailed.