Development And Design Of Full Functionalized Controller For Solar Water Heating System

Today, the energy and environment problem has been a hot issue in the world. The use of fossil energy has caused the environmental pollution and ecological damage on the earth. Solar energy is a kind of renewable clean energy. As the strength of people's environmental awareness and energy conservation awareness, solar energy has drawn increasing attentions. In the applications of solar energy, the technique of solar water heater is the most mature one in China. The productivity of solar water heater in our country has been the largest in the world.In this paper, the solar water heating system which can collect more heat by using forced circulation is more convenience to use. After the analysis of the characteristics of the solar water heating system, the paper conducted software and hardware designs for the controller to realize the full functionalized control for the water heating system. The ATmegal6 microcontroller was used as the core of the controller to achieve the following functions.(1) Temperature difference control of the heat collect pump:according to the difference between the temperature measured by DS18B20 of the water in the solar energy collectors and in the hot water tank, the MCU decides to start or stop the heat collect pump. This control mode can improve the heat collect efficiency and simply the controller system.(2) Time control of the heat collect pump:users can set the start and stop time of the heat collect pump. During this period, the pump would have been in working all the time.(3) Control of the water supply pump:water flow sensors that are used to detect the signals of using water, can achieve the control of water supply pump which can provide suitable water supply pressure.(4) Control of the temperature and level of water in the hot water tank:both of the control of temperature and water level are optimized, so the solar water heating system can guarantee the temperature and level of water in the tank. At the same time the controller can set time to start the electric heater.(5) Control of the antifreeze protection:the temperature of the water in the heat collect system is measured. When the temperature is too low, the heat collect pump will be set up to force the hot water in the tank into the heat collect system. In this way, the safety of the heat collect system is ensured in the winter.(6) Control of the high temperature protection:to avoid the explosion caused by cold shock of the tube, only in a specific period of time after the initialization of the controller the heat collect pump is aloud to start for the first time. To achieve the purpose above, after the initialization the controller need to read the local clock first, and then starts the time mode by automatically setting the start and stop time of the heat collect pump.(7) Key operations and the display of LCM:through key operations, users can set local time of the controller, set the time parameters, and also can add water or temperature to the hot water tank. The controller used LCM to display the controlling information including real-time clock, time parameters, working mode of the heat collect system, temperature and level of water in the hot water tank and the users'selection of manual functions.