Research On The Performance Of Drying System Powered By Solar PV/T Collector And Wind Turbine

Solar thermal technology has prospects for the broad application of drying agricultural and associated products.Solar hot air drying technology can effectively solve storage and transportation problems for agricultural and associated products.To improve comprehensive solar energy utilization efficiency,in this study a solar hot-air drying system,based on a comprehensive solar photovoltaic/thermal（PV/T）utilization collector,was designed and built.The solar PV/T collector could provide the thermal and electrical energy for drying system.Meanwhile,to eliminate the stagnant hot airflow zones and improve drying efficiency and materials’quality,the structure of drying chamber was optimized.On this basis,to improve the utilization ratio of renewable energy in drying system and further solve the problem of insufficient energy supply for solar energy under cloudy and rainy weather and at night,a novel hybrid drying system powered by solar PV/T air collectors and wind turbine was also proposed.In this system,the thermal energy needed for drying procedure was provided by two PV/T air collectors.In addition,the electricity generated by PV/T collectors and wind turbine is used to drive all DC fans to discharge wet air and enhance mass transfer.The main work content and conclusions are as follows:（1）A solar drying system was designed and built to integrate with PV/T air collectors that can provide all of the electric and thermal energy needed for the drying procedure.And the structure of drying chamber was optimized to solve the problem of uneven temperature distribution.The turnips was selected as drying materials to study the enhanced performance of the solar drying system under different drying conditions.In this study,the thermal and electrical characteristics of the solar PV/T air collector（the polycrystalline silicon type and the amorphous silicon type）were comparatively studied.The results showed that seven direct current fans at the air entrance and 12 internal circulation fans on both sides of the drying chamber turned on the solar drying system compared with seven direct current fans at the air drying chamber entrance that turned on the system,which shortens the turnip drying time by 10 hours.The average thermal efficiency,average electrical efficiency,and comprehensive utilization efficiency of the amorphous silicon photovoltaic/thermal collector are 46.8%,5.7%and 54.4%,respectively.The average thermal efficiency,average electrical efficiency,and comprehensive utilization efficiency of the polysilicon photovoltaic/thermal collector are 40.7%,6.8%and 55.4%,respectively.（2）To solve the problem of solar drying discontinuity,a novel hybrid drying system powered by solar PV/T air collectors and wind turbine was proposed and tested based on further optimization of solar PV/T collection drying system.In this study,turnips were still selected as drying samples to study the hybrid dryer performance.The specific energy consumption（SEC）,specific moisture extraction rate（SMER）and drying efficiency of the drying system are determined.The energy and exergy characteristics of the PV/T collector and the performance of the wind turbine are also investigated.Furthermore,the characteristics of the turnip dried with the hybrid dryer are also analysed.The results demonstrated that the electricity provided by the solar and wind energy met the requirements of the drying system for all-day work.The total energy efficiencies of the amorphous silicon PV/T collector for the two days of the drying experiment were 61.4%and 55.2%,and the exergy efficiencies were 9.95%and 9.60%.For the monocrystalline silicon PV/T collector,the total energy efficiencies for the two days were 35.5%and 36.0%,and the exergy efficiencies were 10.22%and 9.31%.The energy efficiency of the wind turbine was21.6%.The SEC and the SMER were 7.5194 k Wh·kg^-1and 0.1330 kg·（k Wh）^-1,respectively,during the turnips drying（28 h）.The drying efficiency ofthe hybrid drying system reached 8.99%.（3）The performance of the drying system was studied.In this study,the drying characteristics of different parts of Panax notoginseng are studied using the hybrid drying system and open sun drying.And the quality of main root,rhizome and fibrous root dried by using the two drying methods are compared and analysed based on colour parameters,microstructure and ginsenoside contents.Furthermore,the structure of the dried Panax notoginseng are also investigated by Fourier transform infrared spectroscopy（FTIR）.The results showed that the drying time using the dryer to dry the main root slices was shortened by 33.3%compared with natural sun drying when the moisture content decreased from the initial value to 13%.For rhizome and fibrous roots,the drying time was shortened by 74.1%and 53.8%,respectively.Meanwhile,the drying quality using the hybrid drying system higher than open sun drying,and the total saponin contents of the main root slices and rhizome were of 9.1%and 12.2%,respectively.（4）Selecting Panax notoginseng as the materials,the economy of the drying system was analyzed.The economic payback period of the system was determined to be 1.03 years.