Design and Control Analysis of an Automatic Active Domestic Solar Water Heating System

Solar water heating technology has become one of the most attractive methods of heating water in residential and public buildings with numerous benefits. This study presents the design technique for an automatic active domestic solar water heating system (ADSWHS) to satisfy the hot water demand for a residence in Wum (10.43 degrees E, 6.23 degrees N) with a daily hot water demand of 500 litres supplied at 70 degrees C, using flat plate solar collectors and an arduino microcontroller. The solar data used in this analysis were obtained from Photovoltaic Geographical Information System (PVGIS) and the method used is the active direct roof mounted solar water heating. The system design process consist of evaluating the optimum collector tilt angle, the thermal analysis of the flat plate collector and hot water storage tank and finally modelling a low cost automatic controller for the system using a microcontroller in the Proteus software. The optimum annual average solar radiation on the tilted solar collector was obtained following the calculation of the conversion ratios of the direct, diffuse and reflected radiations. At annual time scale, the optimum tilt angle (beta) that maximizes the collected radiation was 11 degrees and the corresponding optimum average irradiance of 432 W/m(2) was obtained. The analytical results presented for the performance of the heater indicate that the system operates at an annual thermal efficiency of 55.49%. The control system simulation results indicate that the system uses 4.5kWh and 2.075kWh of energy to run the pump and the auxiliary heater respectively and produces 26.187kWh of energy to heat up the cold water from 25 degrees C to 70 degrees C for a single day.