Research On Performance And Optimization Strategy Of The Cooling System Driven By Small Off-grid Wind Turbine

Battery banks are used as a buffer and storage unit for small off-grid wind power system,which is necessary for stabilize the fluctuation and intermittent of wind power.However,battery banks are accounting for about 50% of the total cost of off-grid systems,which has led to high unit investment costs for small off-grid wind power systems.In order to solve the energy storage problem of systems,this paper proposed a cold-storage system drive by small off-grid wind power to replace partial battery to store wind power with cold energy storage.In this paper,the following research works is carried out to improve the wind-to-cold conversion efficiency:(1)A cold-storage system driven by small off-grid wind power was constructed.The structure and operation principle of the system are introduced in detail,and the selection of the main components of the system was determined based on the characteristics of local wind resources.Besides,a theoretical model of energy transfer for the main components of the system is established,which provides a theoretical basis and calculation basis for subsequent experimental analysis.(2)By experimental comparisons the system operating characteristics operating characteristics under FCCM and SCM modes,the feasibility of using wind power cooling to replace part of the battery’s energy storage has been verified。Based on the low experimental wind speed conditions,when the system is operating in FCCM mode,the compressor and battery are operated in parallel.The results showed that both the load equivalent impedance and the effect of battery clamping can be effectively reduce.Furthermore,the system conversion efficiency of wind-to-cold is 52.0%,which higher than 41.0% in SCM mode;Based on the high experimental wind speed conditions,when the system operates in FCCM mode,the power dissipation capacity of the load can be improved and the risk of wind turbine speed overload is reduced。The result show that the system conversion efficiency of wind-to-cold is 51.4%,which is higher than 38.1% in SCM mode.(3)The wind power cooling performance of the system under different wind speeds and battery charged states was experimentally.The experimental results show that the wind power and the power demand of the compressor was matched when the experimental average wind speed is 4.46 m / s.under the experimental conditions,the battery energy ratio of the system is the lowest and the wind-to-cold conversion efficiency of the system is the highest at this time,which is 0.67 and 52.0% respectively.Besides,the results showed that the system can stable operation when the battery is in a working state,under the experimental conditions.In this state,the refrigeration efficiency of the compressor and the wind-to-cold conversion efficiency are 2.33 and 50% respectively,which are both higher than 2.11 and 41.33 in the state of battery power lack.Therefore,the key factor to improve the system’s wind-to-cold conversion efficiency is to improve the matching between wind power and compressor power,which can improve the effective wind energy utilization rate of the system and reduce the storage capacity of the battery.(4)A control algorithm that uses PMW pulse width modulation technology to change the operating power of the compressor is proposed to track the change of wind power.The effectiveness of the control algorithm has been verified by conducting comparative experiments on wind power refrigeration before and after the control algorithm is adopted.On one hand,the comparative experimental results show that the wind-to-cold conversion efficiency of the system is 41.89% after the system is optimized by the control algorithm,which is 19.8% higher than before the control algorithm is used。Furthermore,the matching between the compressor power and the wind power is improved,which reduces the energy loss of the system load and improves the wind power conversion efficiency of the system;On the other hand,after the control algorithm was used,the battery energy storage capacity required by the system under the experimental conditions was 24.8 kJ,which was 43.9% reduced compared to before the control algorithm used.Therefore,the wind-to-cold conversion efficiency of the system is improved and the energy storage cost of the system is reduced after the control algorithm is adopted.