大跨度主动蓄能型温室温湿环境监测及节能保温性能评价

Evaluation on heat preservation effects in micro-environment of large-scale greenhouse with active heat storage system

针对日光温室土地利用率低,单体小不能进行立体栽培果树种植,不利于机械化操作等问题。该文提出一种大跨度主动蓄能型温室,该温室南北走向,双屋面拱形钢骨架结构,并采用主动蓄放热系统进行能量的蓄积与释放。该试验以传统砖墙日光温室作为对照,对大跨度主动蓄能型温室室内外温湿度以及主动蓄放热系统的能量收支进行分析,并对比2种温室的建造成本,综合分析了试验温室保温节能效果及经济效益。结果表明：大跨度主动蓄能型温室土地利用率高达87.4%。温室夜间平均气温高于10℃,无极端低温,晴天夜间平均气温比对照温室高1.5～3.1℃,比室外高13.9～19.3℃;阴天夜间平均气温比对照温室高1.2～2.8℃,比室外高12.5～18.9℃。夜间室内相对湿度平均比对照温室低7%～10%。主动蓄放热系统性能系数COP（coefficient of performance）为3.4～4.2,平均每天能耗0.013 k Wh/m2,与传统燃煤锅炉加温系统相比,平均节能率为47%。大跨度主动蓄能型温室建造成本每平米307.2元,比传统砖墙日光温室低144.5元。大跨度主动蓄能型温室是一种土地利用率高,单体大,保温性能良好,能进行冬季果菜生产的新型温室类型,且投入少,综合其经济环境效益,值得推广应用。

A Chinese Solar Greenhouse（CSG）, is characterized by a lean-to south-facing roof covered with a removable blanket for nighttime heat preservation and a solid north wall for daytime solar energy storage. However, the land utilization efficiency of the CSG is only 30 %-45 % because of the necessary distance between 2 adjacent greenhouses to prevent shading. Moreover, inner available space of the CSG is usually small, which results in intensive labor and low mechanization. To solve above problems, a new-type large-scale greenhouse with an active heat storage system was designed. The greenhouse was tunnel type, and had wide span with steel frame and south-north orientation.Thus, the necessary distance between 2 adjacent greenhouses was shortened to 2 m from 6-8 m of the traditional CSG. In this case, the land use efficiency of the new type greenhouse was increased to 87. 4 % from 30 %-45 % of the traditional CSG. The greenhouse was designed with a height of 5 m, a length of 60 m and a width of 20 m.Greenhouse indoor ground was 0. 5 m lower than that outdoor to increase available space for plant growth and labor work, and to improve the stability of the micro environment. The north wall built with red bricks and a removable external blanket with total heat transfer coefficient of 1. 2 W /（ m2·K） and an internal thermal screen made of aluminized film were used in the experimental greenhouse. To guarantee daytime solar storage and nighttime heat preservation, the greenhouse employed an active heat storage-release system（ AHS）. The AHS with 50 south-facing collectors was used to collect solar energy by flowing water between 2 sheets of black plastic foil and store heat energy in 2 underground insulated water tanks（ 8 m3each）. During the nighttime, when the air temperature inside the greenhouse was lower than the set-point, the AHS was used to heat the greenhouse by circulating warm water from the tanks. If only one tank was used, its temperature would gradually increase during the day and decrease during the night. With some smaller tanks we could empty or fill the energy in order. The total area of 50 south-facing collectors（ with the length of 2 m and the width of 1. 35 m） was 130 m2. Some collectors were installed vertically against the north wall and south wall, and some were installed with a tilt angle of 55 ° and a distance of 3. 75 m in 2rows from north to south in the greenhouse to collect more solar energy. During the winter about 15 % of the greenhouse floor was shaded by the collectors where the low and scotophil leaf vegetables were planted. There were the large-scale greenhouse（ experimental） and CSG（ reference） located in Beijing（ 40 ° 13 ′ N, 116 ° 65 ′ E）. A reference CSG was 60 m long and 8 m wide with a ridge height of 3. 8 m. The north wall was 2. 3 m high and 0. 46 m thick,and composed of red bricks with 240 mm thickness outside and 120 mm thickness inside, and polystyrene board with 100 mm thickness in the middle. Tomato was used as a model plant in 2 greenhouses. The experiment was conducted from December 5th, 2014 to February 5th, 2015. Indoor air temperature, relative humidity, initial cost of the greenhouse, energy consumption and performance of the AHS were analyzed. The results showed that the land utilization efficiency of the experimental greenhouse could be increased up to 87. 4 %. Average nighttime air temperature in the experimental greenhouse was 1. 5-3. 1 ℃ on sunny day and 1. 2-2. 8 ℃ on cloudy day higher than that in the reference CSG. The average air temperature in the experimental greenhouse was kept above 10 ℃during the whole night. It was 19. 3 ℃ higher than outdoor air temperature. The relative humidity in the experimental greenhouse was 7 %-10 % lower than that in the reference CSG during nighttime. The average COP（ coefficient of performance） of the AHS was 3. 4-4. 2 and the average daily electricity consumption of the AHS was0. 013 k Wh / m2 during both sunny days and cloudy days. Compared with traditional heating methods using fossil fuels, the AHS system achieved 47% energy savings. The initial cost of the experimental greenhouse was 307.2 yuan/m2,which was 144. 5 yuan / m2 lower than the CSG. The above results indicate that the large-scale greenhouse with an active heat storage system can improve land utilization efficiency and heat preservation performance, and decrease greenhouse initial cost and inside relative humidity. Thus, the large-scale greenhouse with an active heat storage system is worthy of popularization and application.