Study On Preparation And Heat Storage Performances Of Glauber's Salt-Based Composites Phase Change Materials In Qinghai-Tibet Plateau's Solar Greenhouse

Energy and environment around the sustainable development world today is one of the most pressing question.Qinghai-tibet plateau solar energy resources are rich,and at the same time the weather of It is cold for most of the year.So greenhouse heating night is difficult to sustain crop growth.The traditional heating mode need to consume a large amount of fossil fuel energy,produced a large number of environmental pollution such as greenhouse gases at the same time.Efficient energy saving solar greenhouse in cold condition in the Tibetan area,can effectively overcome the bad and changeable weather,solve the problem of anti-season vegetables production,in order to meet the needs of local people.There are remarkable economic and social benefits.Herein,to use clean solar energy storage phase change materials as the greenhouse environment control mode,has become the new target of greenhouse engineering technical field.Glauber's salt?Na₂SO₄·10H₂O?based composite phase change energy storage materials?composite PCMs?were prepared by physical blending method.To effectively control phase change melting temperature point in the near 25 ? and maintaining high phase change melting enthalpy,adding melting point regulator agents?nucleation agents and thickening agents.Thermal properties were measured by differential scanning calorimetry?DSC,NETZSCH 200F3?.The thermal cycling tests were carried out in an oven?Themo SCIENTIFIC HAAKE A 40?by heating and cooling the sample.Thermal conductivities were determined by Transient Plane Source?TPS?method?Hot Disk,TPS 2200?.In order to obtain shape-stabilized PCMs,expanded graphite as the carrier,the thermal conductivity expanded graphite/Na₂SO₄·10H₂O composite phase change energy storage materials?EG/SCNa?were prepared by vacuum adsorption method.So as to study the thermal conductivity performance of PCMs,we chose grapheme?GNPs?as the heat-removing agent,and analyze the thermal conductivity of the composite PCMs taking the effective medium theory.The results show that when adding the mass of borax 4 %,supercooling ofPCMs almost disappear;adding CMC 1.5 %,phase separation not exist;adding graphite powder 1 %,thermal conductivity significantly improve.Latent heat of PCMs was measured by DSC is 127 kJ/kg.After 300 times phase cycle changing,PCMs still can keep well performance,which is suitable for greenhouse to keep warm in cold climate.PCMs in greenhouse temperature test results show that when the mass of phase change materials for 25 kg,35 kg and 45 kg,the lowest greenhouse temperature increased 1?,3.6? and 4.4? before sunrise in the morning.Gypsum back wall of PCMs greenhouse temperature test results show that the temperature in noon decreased 1.1 ?,2.2 ? and 3.0 ? and in the morning before sunrise increased0.4?,2.4? and 4.0? comparing with contrasted greenhouse.We can conclude that the adding of this phase change materials can obviously increase the greenhouse inside and back wall lowest temperature,and it is suitable for solar greenhouse heating application in extreme cold climate environment.