Experimental Study On Low-Temperature Grain Storage With Solar Cooling

Grain is one of the basic backbones for every country, and grain storage is necessary to ensure their security in grain supply. Low-temperature grain storage is one of the most promising technologies in grain storage. Nowadays, the development and utilization of low-temperature grain storage in our country is not satisfying. The importance of low-temperature grain storage is not so well understood, and the existing technologies have not met the requirements of high quality, high benefits, low energy consuming and low pollution, including: grain storage under natural low temperature, mechanical ventilation in winter using natural cold source and mechanical refrigeration with a grain cooler. There are great needs for novel low-temperature grain storage technologies. Solar energy is the energy which is clean, environment friendly and renewable. Solar cooling has the advantages that its cooling power and cooling demand can match well both with time and location. There have been some utilizations and researches in solar driven adsorption refrigeration, but it has not been reported that using solar adsorption chiller in low-temperature grain storage, which is right the research of this paper. The main research work of this paper can be summarized as following:(1) The grain temperature distribution in a grain bin all over one year was investigated, based on which four types of feasible ventilation mode for low-temperature grain storage with solar cooling were brought out. The grain bin was located in Jiangsu Province, where the solar irradiation is at the moderate level of China.(2) From 2004 to 2006, three sets of low-temperature grain storage system with solar cooling were built in three grain bins respectively. They were: low-temperature grain storage system with solar cooling plus circulating ventilation in an air insulation layer, low-temperature grain storage system with solar cooling plus internal circulating ventilation in the top layer and the area close to the wall under the sealing film, and low-temperature grain storage system with solar cooling plus internal and bidirectional circulating ventilation in the top layer under the sealing film. Among them, the system built in 2006 is the main research point of this paper.(3) The experimental study in this paper was mainly carried out on the system built in 2006, including: analysis of performances of the solar adsorption refrigeration subsystemand matching between its components; the low-temperature grain storage system was tested in practice, from which the effect of grain storage was investigated. The utilization of cold core of the grain bin and the ventilation mode were also discussed.(4) The performances and effects in grain storage of the three systems from 2004 to 2006 were compared, in order to find the system with the best performances and effects in grain storage, to be the basis of the following advanced study in the future. The experimental study carried out in 2004-2006 indicated that using the above three low-temperature grain storage systems with solar cooling can delay or restrain the going up of the temperature in the top layer and the area close to the wall of the experimental bins in some degrees during hot months, compared to their reference bins. Among them, the low-temperature grain storage system with solar cooling plus internal circulating ventilation in the top layer and the area close to the wall under the film, gave out the best performances. If the system starts to work before the temperature of the top layer goes beyond 15-20℃, it is quite probable to reach the goal of quasi-low-temperature grain storage.