| The solar greenhouse is the main place for winter vegetable planting in northwestern China,and it is the main source of winter vegetable supply.However,the traditional solar greenhouse adopts the form of passive use of solar energy,which makes the internal heat of the solar greenhouse unable to meet the needs of plant growth,so useing solar energy is very necessary to supply heat for solar greenhouses.The solar energy resources in northwestern China are very rich.The annual radiation is large and the sunshine time is long.Therefore,it is very promising and a general trend to actively use solar energy resources to provide heat for solar greenhouses.In order to make full use of the abundant solar energy resources in the northwest region and improve the indoor thermal environment of the solar greenhouse,This project combines the trough collector with the solar greenhouse,and takes the initiative to use solar energy to provide heat for the solar greenhouse.In the early stage,the research group studied the active and passive heat storage wall of the solar greenhouse.This wall can effectively store heat and has a certain width and loadbearing capacity.Based on this structural feature of the solar greenhouse,the subject studied a multi-curved trough concentrated collector applicated the solar greenhouse,the design and experimental research of the trough concentrated collector will be discussed.The main contents are as follows:First of all,Introduce the structural characteristics and heat collecting principle of two trough type concentrated collectors,and use the Tracepro optical simulation software to study the two trough concentrated collectors,and analyze the geometric optical efficiency of different collectors.The structural dimensions of the single-curved trough concentrated collector and the multi-curved trough concentrated collector are selected.Secondly,Analyze the influencing factors and evaluation indexes of the thermal performance of the collector,design performance comparison test research schemes of two kinds of trough concentrated collector,and build two trough concentrated collector performance test benches in Lanzhou area,The thermal performance of two trough concentrated collectors with a length of 2 m was experimentally studied.Thirdly,Different influencing factors of heat collector performance were analyzed,and the influences of air velocity,outdoor temperature,solar irradiance,covered and uncovered plates and length of collector on heat collector performance were studied.Fourthly,The multi-curved trough collector with good heat collecting performance was applied to solar greenhouse in Lanzhou area,and the heat collecting effect of practical engineering application was analyzed and studied.The experimental results show that: First of all,The geometric optical efficiency of the multi-curved trough concentrated collector is higher than the geometric optical efficiency of the single curved trough concentrated collector,which is 8.1% higher.Secondly,When the air flow rate is 4.4m/s,the instantaneous heat collection and instantaneous heat collection efficiency of the two collectors are the highest.The instantaneous heat collection and instantaneous heat collection efficiency of the collector increase with the increase of solar irradiance.The higher the outdoor ambient temperature,the higher the instantaneous collector efficiency of the collector.The average instantaneous heat collecting efficiency of multi-surface troughs with cover plate is higher than that without cover plate,which is 3.1% higher on average.The instantaneous heat collecting efficiency and instantaneous heat collecting efficiency of multi-curved trough collector are always higher than that of single-curved trough collector.Thirdly,In practical applications,the multi-curved grooved concentrating collector can achieve a maximum instantaneous heat collection efficiency of 54%,an average heat collection efficiency of 41.2%,a typical sunny collector daily accumulated heat capacity of 48 MJ to 56 MJ,and a cloudy weather of 30 MJ ~40MJ.The research results provide a reference for the design and experimental study of the multicurved trough concentrating collector in the solar greenhouse in northwestern China.It also provides a new idea for the integration of collectors and solar greenhouses.Making full use of the abundant solar energy in the northwest region to solve the problems of low indoor temperature in solar greenhouses and low heat collection efficiency of solar collectors,and this has contributed to improving the output value of greenhouse crops in winter. |
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