Preparation And Study On The Greenhouse Thermal Storage Wallboard With PCM

With the rapid development of facility agriculture in China, the area of greenhouse hasbeen reached3.5million hectares according to statistics of2011and ranked first in the world.However, in the long-term construction of greenhouse, large brick has been consumed as wallmaterials. Large amount of high-quality clay and energy were consumed by produce of claybricks. Using clay bricks as greenhouse wall materials is not only destruction of arable land,but also increase the country’s energy crisis, high construction costs, long construction periodand pollution of construction trash. In addition, traditional backward technology ofgreenhouse construction can not meet the requirements of the development of solargreenhouse to a modern, industrialized direction and new type of solar greenhouseconstruction technology need to be developed and formulated.In this study, the PCM, made up of Na₂HPO₄·12H₂O and KCl and improved by addinggraphite and sodium silicate was considered as novel energy storage material for greenhouseLHTES application. The combination of20g Na₂HPO₄·12H₂O+1.6gKCl+1.2g sodiumsilicate+0.4g graphite has no supercooling occur and longer exothermic time was good PCMfor LHTES systems. The thermal performance was determined by using DSC analysis, themelting and latent heats of improved PCM were determined as21.7℃and165.9J/grespectively. The stability of improved PCM was also studied by FT-IR spectrum. All infraredabsorption peaks of improved and unimproved PCM are similar. This means that nodegradation in the chemical structure of improved PCM. As a result, the proportion of20gNa₂HPO₄·12H₂O+1.6gKCl+1.2g sodium silicate+0.4g graphite composite PCM can be usedas the effective material for LHTES systems for greenhouse since it has the advantages of itseasy preparation, suitable phase change temperature, high latent heat and good chemicalstability.The heat storage capacity of thermal storage wallboard with14.3Kg m-2is equal toheat storage capacity of240mm brick+100mm polystyrene board+240mm brick by theaccumulation of heat release at the night and latent heat of phase change material. Phasechange thermal storage greenhouse was constructed by thermal storage wallboard and withthe steel skeleton and the performance of temperature, humidity, soil temperature, heat releasewas tested at typical sunny and typical cloudy day. The result show that the temperature ofphase change thermal storage board greenhouse changes very little compare with the brick wall greenhouse, humidity and soil temperature greater than the brick wall greenhouse, theheat release accumulation at night is1.06MJ/m²of thermal storage wallboard, heat releaseaccumulation of brick wall at night is0.92MJ/m².The result of economic analysis and land utilization analysis show the thermal storagewallboard costs higher18yuan/m²than the brick wall in the aspect of material, However, theconstruction of phase change thermal storage board greenhouse changes saves time and effort.In general, the phase change thermal storage board greenhouse has greater advantage overbrick wall greenhouse. In addition, the phase change heat storage greenhouse can be increased2.4to4.8%in land utilization.In this study, thermal storage wallboard was designed according to the theory of phasechange thermal storage. The brick wall can be reduced or replaced the use of the by thermalstorage wallboard combined with the steel skeleton in the construction of greenhouse. Thenew kind of greenhouse also can be used in the non-cultivated areas like the Gobi desert,island, mountain et al. The new type of greenhouse will be able to promote the developmentof greenhouse direction towards to standardization, industrialization and modernization andprovide a scientific basis for the research of the material for solar greenhouse wall andstructure construction technology of greenhouse.