| With the development of solar thermal utilization and heat pump technology, the technology of solar energy heating hot water becomes the focus of research and development in energy field gradually. Parallel solar-assisted heat pump water heater (PSAHP) is widely applied in large and medium scale hot water engineer owing to the virtue of energy -saving, non-pollution and safety. In China, solar-assisted heat pump water heater teachnology is in the development of early stage and the control mode is a simple logical control. So, it is a key problem that how to exploit the advanced control technology to ensure maximum energy -saving and heating steady. This paper concentrates on the intellectual control system of PSAHP. Based on the comprehensive analysis of the influence factors of energy utilization, a new intelligent control strategy is designed on the basis of BP neural networks. The main work was summarized as follows:The influence factors of energy utilization are analyzed theoretically, and a new improving energy utilization control strategy is proposed. The relationship between the quantity of solar radiation and temperature-rise of water is tested, and the threshold of solar radiation quantity to start heat pump water heater is decided; Experimental study was carried out to investigate the impact of ambient temperature and power consumption, running time, energy utilization. The higher ambient temperature results in the lower power consumption, running time, and the higher energy utilization. The results of experiments agree with the theoretical analysis.The energy utilization prediction model of PSAHP based on BP neural networks was set up, which can predict the running time and energy utilization according to the varieties of the quantity of solar radiation, ambient temperature and initial temperature of water. Considering the infection of defrosting, a fuzzy system is built to correct the results. Then a simulation on model is run by MATLAB, the predicted results are successful.According to the characteristic of PSAHP, the software of intelligent control system is designed based on the original controller. The PC software programmed by VB6.0, including BP neural networks algorithm, fuzzy correction system, communication between PC and S7-200 PLC and data storage. Procedure made by STEP-7 are designed under the means of block-based design. The results show that 20% of energy utilization have been improved by using the system, which realize energy-saving in the true sense. |
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