Research On Optimal Scheduling Of Solar-air Source Heat Pump Hot Water System

With the rapid development of the industry,solar-air source heat pump hot water projects have gradually become the mainstream in large and medium-sized hot water projects.However,most of these projectsc still use simple logic control strategy,and the coefficient of performance(COP)is low.The key to maximize energy saving and stable heating supply is to improve the utilization rate of solar energy.In order to solve this problem,this article takes a hot water supply project as the object and researches on its optimal scheduling.The main work is as follows.(1)Establish the overall model of the system according to the operating process and principle of the solar-air source heat pump hot water system.The models of the process units,such as the tank unit,collector unit and heat pump unit in the system are built.The unknown parameters in the model were identified by operating data based on actual engineering case.The sliding translation model was used to analyze the water consumption data,and the water consumption prediction model was obtained.The mean absolute percentage error(MAPE)was 6.39%.The forecast models of sunny irradiance in different seasons were obtained based on the local irradiance data.The MAPE was between 6.7% and 8.53%.It was analyzed that the influence of ambient temperature and heat pump inlet water temperature on the operation.The fitting determination coefficient R-square of COP and power were above 0.99.Researching on operation cost optimal scheduling with impact of heat pump's COP and low tariff time changes based on the above models.(2)An adaptive genetic algorithm was proposed to solve the optimal problem of the hot water supply system under two common working conditions,sunny and rainy,and the optimized results are compared with the existing operation.The comparison results show that the hot water supplying is stabler and the operating efficiency has been improved greatly on scheduling optimization.On sunny days,the solar guarantee rate of the optimized scheduling plan has increased by 15.2%,and the heat pump COP has been increased from 2.8 to 3.39,which reduces the heat pump's unnecessary operating time to reduce system's operating cost.On the other side,when on rainy days,the optimized dispatching plan improves the water storage performance at low tariff time.Although the power consumption has increased,the operating costs have decreased by 5.6%.Then,a study on the optimization of heat pump unit using electric heating for defrosting in winter frost environment is carried out.Frost and defrost coefficients are used to evaluate the performance of the heat pump defrost mode.The study found that the ambient temperature and humidity are important factors affecting the heat pump's frosting speed.The frost and defrost coefficient of the heat pump is 0.85 during all-day operation,and the average COP of the heat pump is 1.24 when in defrost mode.Operating cost has fallen by 15.6% on the winter sunny days by optimal scheduling.(3)The problem of rescheduling under two types of sudden interference events were researched: weather change and heat pump unit failure.Whether it was rescheduled depends on the severity of emergencies.In order to ensure the stable operation of the system,a rolling time-domain optimization technique is used to solve a multi-objective optimization model based on operating costs and deviations.The results show that the rescheduling plan can allocate the running time of the heat pump reasonably with less changes to the pre-scheduling plan and ensure the stability of hot water supply.