Study On The Energy Conversion Transfer Mechanism And Refrigeration Characteristics Of Ice Storage Air-conditioning System Driven By Distributed Photovoltaic Energy

For the strong instantaneous and intermittent of solar irradiance,in the utilization of solar energy,whether it is solar photovoltaic and solar thermal energy,the energy storage devices are essential.In photovoltaic refrigeration field,the battery is used for the energy storage device.But the investment and maintenance of battery is high,which hindered the development of photovoltaic refrigeration.Therefore,the new energy storage technology or combined other means of energy storage should be adopted to store energy instead of battery,which are the key and difficult in the PV refrigeration research.In order to solve the energy storage problem,the ice storage was adopted to store energy instead of battery in the ice storage air-conditioning driven by distributed photovoltaic energy system in this paper.The theoretical model was developed to analyze the energy conversion and transfer among the system components and the experimental study was carried out.The main research work includes the following aspects.?1?The dynamic ice storage air-conditioning driven by Distributed Photovoltaic Energy System?DPES?was set up and the experimental test work has been carried out to verify the correctness of the energy transfer model.The results showed that the calculated results were in good agreement with the measured.The model could be used to calculated the characteristic parameters in photovoltaic refrigeration field.The experiment and theoretical analysis research on the energy conversion transfer characteristics and refrigeration performance have been done.The results revealed that the ice quantity was 21.89kg under the 22.17MJ/m² solar cumulative irradiation.The ice produced by the electricity converted from photovoltaic was 14.45kg,which accounted for 66.03%of the total ice quantity.So the ice storage could be used to stored energy in PV refrigeration instead of battery.?2?A 1.5 HP immersion type static ice storage air-conditioning system driven by DPES was designed and constructed.And then the theoretical analysis and experimental test research work has been carried out.After the optimization of the ice making mode,the system can stably work continually for three days,which are three typical weather conditions?sunny,cloudy and overcast with light rain?.The efficiency of the refrigerator,fan coil and the whole system were improved to 0.5019,85.41%and 7.65%,respectively.From the analysis results of system energy conversion and transfer,the mismatch problem between the load and the inverter capacity was existed.When the inverter capacity was optimized to 1.11-1.17 times of the load,the efficiency of the inverter was improved to more than 90%.The system performance affecting parameters were analyzed by theoretical calculation and experimental test.The recommended values of the relevant parameters of the system were given to improve system performance and match the energy among the components.In ice making process,the best recommended range of the evaporator temperature and refrigerant flow were 260K²65K and 0.006kg/s⁰.008kg/s,respectively.The best ice thickness is about 35mm and the super-cooled should be controlled within 5K for in the evaporator immersion static making process.?3?the 3HP static ice storage air-conditioning directly driven by DPES was designed and established.The experimental test and characteristic analysis of ice storage replacing battery storage solar energy were investigated.The experimental results showed that the?COP?_solar-ref of the refrigerator directly driven by DPES was0.1729,which was better than solar adsorption refrigeration device.When the air-conditioning worked on the model of out of the box,the system efficiency was31.25%,which was on the same level with the single effect solar absorption refrigeration system.From the analysis results,the output performance of the PV arrays could be improved by 15%when the maximum power tracking?MPPT?controller was adopted.The control strategy of the frequency conversion and the control logic of the matching relation between the MPPT of the PV arrays and frequency conversion compressor were studied.From the test results,when the solar irradiance was low to 80W/m²,the compressor operated stably and continually with17Hz frequency and 841.4r/min speed.Here,the directly driving function was not affected by the intermittent of the solar irradiance.When the energy supply and energy demand between the DPES and refrigerator was optimized to 1.38:1,the?COP?_solar-ref of refrigerator directly driven by DPES was improved from 0.1960 to0.2351 and the system efficiency increased from 16.74%to 20.08%also.When the system worked on the model of out of the box,the system efficiency wa improeved by2.37%.?4?The 2kW dynamic refrigeration by refrigerant direct injection air-conditioning was established and the mechanism of high efficient dynamic ice making by refrigerant direct injunction in the water was researched.The results showed that in the process of refrigerant direct injunction in the water,the refrigerant contact with water adequately and the cold of refrigerant can be exchanged with no thermal resistance.So the cold can be absorbed completely.The system refrigeration efficiency can be greatly improved.The experimental test results revealed that the system COP reached 4.20,which was 153.00%more than that of evaporator immersion static ice making system,which had a 1.66 static ice making COP.So if the dynamic ice making by refrigerant direct injunction in the water can be applied in ice storage air-conditioning directly driven by DPES,the super-cooled problem of static ice making will be effectively solved.?5?By DPES were compared and analyzed.By the optimization of the ice making mode,system structure,energy matching among the system components and the energy control strategy,the energy efficiency of the ice storage air-conditioning directly driven by DPES was greatly improved,which was 60%higher than that of solar adsorption refrigeration system and photovoltaic refrigerator.Working under model of out of box,the system efficiency was 32%,which performance was better than single effect lithium bromide absorption refrigeration air conditioning system driven by solar parabolic trough concentration.The ice storage air-conditioning directly driven by DPES had nearly the same refrigeration performance of photovoltaic air-conditioning.And then,the economic value of the ice storage air-conditioning directly driven by DPES was analyzed take the examples of engineering application projects.The analysis results revealed that the payback period of the project of ice storage air-conditioning directly driven by DPES is between 4.5years and 8 years.