| The combination of solar energy and building air conditioning is one of the main ways to achieve low-carbon development under the background of carbon peak and carbon neutrality.Using distributed solar photovoltaic power generation to drive steam compression air source heat pump refrigeration and heating can effectively solve the problem of high energy consumption of building air conditioning,which can avoid the power shortage in the peak of electricity consumption.It also provides timely consumption for distributed photovoltaic power generation and reduce the impact on the power grid.The cold and heat load of cold and heat source equipment in air-conditioned building varies significantly with regions and seasons,and the performance of photovoltaic power generation also has the characteristics of instantaneity,day and night alternation and seasonal variation.Therefore,in the research of solar photovoltaic air conditioning system,whether the distributed photovoltaic energy matches the load and the demand of cold and heat load,whether the fluctuating photovoltaic energy supply can drive and ensure the stable and efficient operation of variable frequency compressor,how to effectively store cold/heat and continuously supply to meet the demand of building cold and heat load are the key problems to be solved.Based on the cold and hot homologous energy storage air conditioning heat pump system which driven by the photovoltaic power generation in this thesis,we use solar energy resources to realize effective photovoltaic refrigeration/heating and combine with ice storage/water heat storage,to realize cold storage/heat storage instead of electricity storage.This thesis focuses on the scientific issues such as photovoltaic direct-drive air source heat pump technology,the cooperative operation mechanism of cooling/heating storage and air conditioning energy consumption,the matching relationship between real operating environment and system energy efficiency,and the balance between system seasonality and annual utilization efficiency.The matching relationship among the cold,hot and electric of the solar distributed photovoltaic energy storage air conditioning system is given.The research work carried out and the main conclusions obtained are as follows:(1)Based on the parameters of meteorological conditions in typical meteorological years,the characteristics of hourly cooling and heating load demand in selected building air-conditioning rooms throughout the year were analyzed.A distributed photovoltaic direct-drive air-source heat pump cold/heat storage air-conditioning system with a capacity of 3P was proposed and designed.The experimental platform was constructed,and the rationality and stability of the system design were studied.The theoretical design parameters of the system and the basis for component selection were obtained,and the system performance evaluation index was given.(2)The dynamic characteristics of distributed photovoltaic direct-drive energy storage air-conditioning system were experimentally studied.The system adopted a single-stage closed-loop constant voltage-frequency ratio disturbance control strategy to ensure the AC compressor variable frequency adaptive control for tracking the maximum power of the photovoltaic array.The best power operation dynamic matching among the solar energy,photovoltaic power generation and the compressor was achieved under different irradiance conditions.The starting frequency of the variable frequency compressor was as low as 13 Hz,corresponding to the solar irradiation of 143 W/m~2.The utilization efficiency of the system was broadened in the low radiation range.Through the combination of maximum power tracking and frequency conversion control strategy,the stable operation of distributed photovoltaic energy driven variable frequency compressor was realized.(3)The operating characteristics and performance of the distributed photovoltaic direct-drive ice storage/heat storage air conditioning system for refrigeration and cold storage and heating and heat storage were studied.In the refrigeration and cold storage mode,the maximum ice production of the parallel copper coil evaporator was202.4 kg,the ice thickness was more than 15 cm,the energy efficiency of the refrigeration unit was relatively low,about 1.96,and the COP of the solar refrigeration system was 0.204.The energy efficiency ratio and system COP of the refrigeration unit in the refrigeration and cooling mode were 28.2%and 44.1%higher than those in the refrigeration firstly then cooling mode.Under the heating and heating mode,the heating capacity of the heat pump with the casing heat exchanger condenser was 32.67 k Wh,the COP of the solar heating system was 0.328,and the energy efficiency ratio was 2.7.For photovoltaic-driven heating and cooling systems,timely energy consumption was the most favorable way to improve system energy efficiency.The energy efficiency of refrigeration/heating simultaneous cooling/heating mode was obviously better than that of cold storage/heat storage mode.(4)Based on the self-designed cold and heat homologous parallel copper coil evaporator(condenser),the mathematical model of energy conversion and storage components was established.The TRNSYS transient system simulation software was used to model and simulate the photovoltaic grid-connected energy storage air conditioning system.The parameters such as photovoltaic output characteristics,heat pump performance and temperature dynamic change in the system were tested and compared with the model simulation results.The maximum error of each parameter was within 10%,which verifies the reliability of the established model.The model was used to simulate and analyze the energy distribution characteristics between sunlight-electricity-cold-heat of photovoltaic grid-connected energy storage air conditioning system.The results showed that the annual average COP was 0.24,and the annual average EER of heat pump unit was 2.16.The system was used in mild climate areas(such as Kunming),under the premise of only considering the same temperature in the cooling season and the heating season,the design temperature of19°C air conditioning room was a more reasonable choice.(5)In order to verify the applicability of the PV grid-connected energy storage air conditioning system under different time domain conditions,the comprehensive performance of the system under four different typical climate zones of Beijing(cold area),Nanjing(hot summer and cold winter area),Sanya(hot summer and warm winter area)and Kunming(mild area)were compared and analyzed by using the established model.The results showed that system had a higher energy efficiency coefficient,a higher system utilization rate and a higher unit performance coefficient in areas with greater demand for cooling and heating.The system had better performance in Nanjing(hot summer and cold winter area)and Beijing(cold area)with large demand for cooling and heating.Through the related research on the distributed photovoltaic energy storage air conditioning heat pump system carried out in this thesis,the limitation of the intermittent solar irradiation on the working cycle of the photovoltaic energy supply system was overcome.From the distributed photovoltaic source end(the PV power generation)driving the compressor of the power load end(refrigeration and heating),to the energy storage end(cold and heat storage)and lastly the thermal load end(cold and heat utilization),all of the energy efficient coordination was realized.And the annual utilization efficiency of solar energy was improved.Research suggestions on the theoretical design and application scenarios of the system were given.The research work carried out provided a new idea for the synergistic utilization of solar energy and energy storage air conditioning,and also provided theoretical basis and experimental reference for the application of photovoltaic energy storage air conditioning. |
PDF Full Text Request