| Mountain Solar Greenhouse is a new type of solar greenhouse as well as a significantagricultural facility. Located in Yan An city, An Sai county, whose main terrains areMountain and Hill is the most appropriate place for Mountain solar greenhouse. However,further researches are necessary for its best span. If the span of the greenhouse is too small,though the property is improved, it can’t maximuize the land resourse. If it is too large,though the land use capability is enhanced, it will cost more and influence its property andcrop’s growth. Therefore, through the detections of the greenhouse’s temperature, the relativehumidity, the illumination,the fluctuation of ground temperature, the average temperature ofback wall and the heat flux and so on, this thesis makes a research on the influence of span onthe property of Mountain Solar Greenhouse and the heat gain and loss inside the house.The result shows:1.The inside environment of the greenhouse is vulnerable to the influence of outsideclimate environment, and under the same external condition, all parameters present the samechange trend, but the change is a bit different.In terms of light intensity, or the effectiveillumination, the best is10meters, the worst is11meters and9meters is in the middle;Withthe increase of span,the average temperature in the three greenhouse presents a trend ofincreasing first and then declining.10meters’temperature is19.8℃,9meters’ is19.2℃and11metres’ is15.4℃.Therefore, the highest is10m which is0.6℃higher than that of9m and4.4℃higher than that of11m.Under the typical weather condition,the averagetemperature, maximum temperature, minimum temperature of10m are much higher than thatof9m and11m,which shows a good thermal insulation performance.Their relative humidityare74%,70%and81%respectively.10m is lowest, which4%lower than9m and11%lowerthan11m.Comprehensively analysis shows that10m’span has the best illumination intensity,the highest average temperature, the lowest relative humidity, which is the most suitable forcrop’s growth.2. The best indicator of greenhouse utilization is the input-output ratio of the solargreenhouse. As for the net output per unit,10m span is the highest with20.17yuan/m2,9mis in the middle with19.17yuan/m2and11meters is lowest with17.44yuan/m2. In terms ofland utilization, it presents that with the increase of span, the land utilization increases, namely9m <10m <11meters. Therefore,10m span’s mountain land utilization is muchhigher, and has the best economic benefit.3. Greenhouse heat exchange is divided into two parts: heat absorption and heatdissipation.In terms of heat absorption, there are three main ways, namely greenhouse cropfoliar, wall surface and the soil surface.The total heat of them is close to100%. greenhousecrop foliar accounts for45%，Of the total,wall surface accounts for about30%and the restbelongs to the soil surface. In terms of heat dissipation, it mainly includes the heatexchange with the outside world the ventilation of heat and soil heat transfer, among whichthe exchange with the outside world has the largest proportion with about60%, the ventilationof heat accounts for20%and the lowest is soil heat transfer with the rate of10%.The totalheat absorption of the three different span mountain sunlight greenhouse during the dayare:6.60x109J,6.94x109J,7.50x109J.The total heat absorption are:5.34x109J,5.56x109J,6.57x109J.Therefore,the heat storages are:1.26×109J,1.38×109J,0.93×109J.10m is thelargest,0.12×109J higher than9m,and0.45×109J higher than11m.With the increase ofspan,the quantity of the greenhouse heat absorption and heat dissipation increase but with adifferent size of growth and have different heat storages. Comprehensively analysis showsthat10m span mountain sunlight greenhouse heat storage is the largest, and has the best heatstorage performance.4. Through establishing the greenhouse thermal model, calculating the temperaturevalue according to the formula and making comparison between the measured values, therelative error value can be gotten. analying the height of relative error value, the stability ofgreenhouse thermal environment can be estimated. Three solar greenhouse‘srelative errorvalue are:7.1%,5.4%and5.9%, respectively, which indicates that simulated values andmeasured values is highly matched and the thermal environment is relatively stable.5. Comprehensively comparison of performance indicators and regenerative propertieson the three different span mountain sunlight greenhouse comes to a conclusion:10m spanmountain sunlight greenhouse has the best properties and is the most appropriate solargreenhouse type. |
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