A night cooling system for a greenhouse using solar energy

在日本的农业中，大量的电能被消耗在夜间的温室冷却上。本文对太阳能的利用进行了探讨，开发了一种利用太阳能的温室夜间制冷系统。这是一个间歇吸收式制冷系统。太阳能在白天作为溶液浓度差的能量储存，在夜间用于冷却。通过实验验证了该系统的工作原理。根据实验结果计算了热平衡。该系统由蓄热器/散热器、真空罐和蒸发器/冷凝器3个测量部件组成。蓄热器/散热器白天收集太阳热量，晚上将吸收的热量散发出去。该组件采用改进的平板太阳能集热器。真空罐内部被分成3部分。它们是分离器，吸收器和储存器。吸收塔内填充了大量聚丙烯空心小球，增加了蒸汽与液体的接触面积。蒸发器/冷凝器由铜管组成，铜管上附有翅片以增加传热面积。采用水和溴化锂液体作为制冷剂-吸附剂对。实验结果表明，所研制系统的原理是没有问题的。吸收剂在白天被太阳热浓缩。在夜间，冷凝水被蒸发并冷却冷凝器外的水。实验结果总结如下：1。在足够高的温度下收集太阳能以使吸收物再生。吸收性能良好。温度随吸收热的升高是可以接受的。溴化锂没有从溶液中析出。由于传热面积不够，限制了冷凝器的性能。面积应该更大。

In Japanese agriculture, a lot of electric energy is consumed for greenhouse cooling in nighttime. In this study, the utilization of solar energy was discussed, and a night cooling system for a greenhouse using solar energy was developed. That is an intermittent absorption refrigerating system. Solar energy is stored as the energy of concentration differentials of the solutions at daytime, which is used for cooling at nighttime. The experiments ware carried out to confirm the operating principle of the system. From the experimental results the heat balance was calculated.The system consists of 3 measure components, those are a regenerator/radiator, a vacuum tank and a evaporator/condenser. The regenerator/radiator collects solar heat at daytime, and radiates the absorption heat at nighttime. A modified flat plate solar collector was used for the component. The inside of the vacuum tank was separated in 3 parts. Those are a separator, an absorber and a reservoir. The absorber was filled with a lot of small polypropylene hollow-body balls to increase the contact area of vapor and liquid. The evaporator/condenser was made of copper tubes on which fins were attached to increase the area of heat transfer. Water and lithium bromide liquid were used as the refrigerant-absorbent pair. From the results of experiments, it was confirmed that the principle of the developed system had no problem. The absorbent was concentrated by solar heat at daytime. At nighttime the condensed water was vaporized and cooled the water outside of the condenser. The experimental results are summarized as follows,1.Solar heat was collected at a sufficiently high temperature for regenerating the absorbent.2.Performance of absorption was sufficient.3.Temperature rise with the absorption heat was an acceptable level.4.Lithium bromide was not precipitated out of the solution.5.Because the heat transfer area was not enough, performance of the condenser was limited. The area should be larger.