周 升,張 義,程瑞鋒,楊其長(zhǎng),方 慧,周 波,盧 威,張 芳
(1.中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)環(huán)境與可持續(xù)發(fā)展研究所,北京100081;2.農(nóng)業(yè)部設(shè)施農(nóng)業(yè)節(jié)能與廢棄物處理重點(diǎn)實(shí)驗(yàn)室,北京100081)
大跨度主動(dòng)蓄能型溫室溫濕環(huán)境監(jiān)測(cè)及節(jié)能保溫性能評(píng)價(jià)
周 升,張 義,程瑞鋒,楊其長(zhǎng)※,方 慧,周 波,盧 威,張 芳
(1.中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)環(huán)境與可持續(xù)發(fā)展研究所,北京100081;2.農(nóng)業(yè)部設(shè)施農(nóng)業(yè)節(jié)能與廢棄物處理重點(diǎn)實(shí)驗(yàn)室,北京100081)
針對(duì)日光溫室土地利用率低,單體小不能進(jìn)行立體栽培果樹(shù)種植,不利于機(jī)械化操作等問(wèn)題。該文提出一種大跨度主動(dòng)蓄能型溫室,該溫室南北走向,雙屋面拱形鋼骨架結(jié)構(gòu),并采用主動(dòng)蓄放熱系統(tǒng)進(jìn)行能量的蓄積與釋放。該試驗(yàn)以傳統(tǒng)磚墻日光溫室作為對(duì)照,對(duì)大跨度主動(dòng)蓄能型溫室室內(nèi)外溫濕度以及主動(dòng)蓄放熱系統(tǒng)的能量收支進(jìn)行分析,并對(duì)比2種溫室的建造成本,綜合分析了試驗(yàn)溫室保溫節(jié)能效果及經(jīng)濟(jì)效益。結(jié)果表明:大跨度主動(dòng)蓄能型溫室土地利用率高達(dá)87.4%。溫室夜間平均氣溫高于10℃,無(wú)極端低溫,晴天夜間平均氣溫比對(duì)照溫室高1.5~3.1℃,比室外高13.9~19.3℃;陰天夜間平均氣溫比對(duì)照溫室高1.2~2.8℃,比室外高12.5~18.9℃。夜間室內(nèi)相對(duì)濕度平均比對(duì)照溫室低7%~10%。主動(dòng)蓄放熱系統(tǒng)性能系數(shù)COP(coefficient of performance)為3.4~4.2,平均每天能耗0.013 kWh/m2,與傳統(tǒng)燃煤鍋爐加溫系統(tǒng)相比,平均節(jié)能率為47%。大跨度主動(dòng)蓄能型溫室建造成本每平米307.2元,比傳統(tǒng)磚墻日光溫室低144.5元。大跨度主動(dòng)蓄能型溫室是一種土地利用率高,單體大,保溫性能良好,能進(jìn)行冬季果菜生產(chǎn)的新型溫室類(lèi)型,且投入少,綜合其經(jīng)濟(jì)環(huán)境效益,值得推廣應(yīng)用。
溫室;溫度;環(huán)境調(diào)控;土地利用率;大跨度;主動(dòng)蓄放熱系統(tǒng);相對(duì)濕度;日光溫室
周 升,張 義,程瑞鋒,楊其長(zhǎng),方 慧,周 波,盧 威,張 芳.大跨度主動(dòng)蓄能型溫室溫濕環(huán)境監(jiān)測(cè)及節(jié)能保溫性能評(píng)價(jià)[J].農(nóng)業(yè)工程學(xué)報(bào),2016,32(6):218-225.doi:10.11975/j.issn.1002-6819.2016.06.030 http://www.tcsae.org
Zhou Sheng,Zhang Yi,Cheng Ruifeng,Yang Qichang,Fang Hui,Zhou Bo,Lu Wei,Zhang Fang.Evaluation on heat preservation effects in micro-environment of large-scale greenhouse with active heat storage system[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2016,32(6):218-225.(in Chinese with English abstract) doi:10.11975/j. issn.1002-6819.2016.06.030 http://www.tcsae.org
日光溫室是中國(guó)北方地區(qū)冬季作物生產(chǎn)的主要設(shè)施,近年來(lái)發(fā)展迅速,面積已達(dá)100.1萬(wàn)hm2[1]。日光溫室最顯著的特點(diǎn)是具有北墻結(jié)構(gòu),白天蓄集熱量,夜間釋放熱量進(jìn)行溫室增溫[2-5]。但日光溫室冬季存在極端溫度,正午存在極端高溫,夜間存在極端低溫[6-7]。相鄰日光溫室為避免前后遮陽(yáng),間距通常為脊高的2~2.5倍,以及部分厚土墻結(jié)構(gòu),導(dǎo)致土地利用率低,僅有30%~45%[8]?,F(xiàn)有日光溫室單體小,不利于機(jī)械化操作,勞動(dòng)強(qiáng)度大[9-11]。因此如何提高日光溫室土地利用率,為機(jī)械化操作提供足夠空間將是未來(lái)日光溫室發(fā)展的迫切任務(wù)。
遼沈型日光溫室系列,在提高圍護(hù)結(jié)構(gòu)保溫性的同時(shí),不斷增大溫室跨度[12-15]。但由于溫室后坡及北墻遮擋陽(yáng)光,間距無(wú)法縮小,土地利用率仍不高。下沉式大跨度大棚型溫室,連棟型日光溫室,以及南方新型溫室大棚、連棟塑料溫室等[16-18],大大提高了土地利用率,但是冬季室內(nèi)溫度偏低,無(wú)法進(jìn)行茄果類(lèi)作物生產(chǎn)。
為進(jìn)一步提高溫室土地利用率,增大溫室空間以便于機(jī)械化操作,同時(shí)使溫室具有良好的蓄熱保溫性能,在前人研究的基礎(chǔ)上,作者設(shè)計(jì)了一種大跨度主動(dòng)蓄能型溫室。有效蓄積進(jìn)入溫室的能量并用于夜晚加溫是解決蔬菜越冬生產(chǎn)的關(guān)鍵,本研究采用主動(dòng)蓄放熱系統(tǒng)進(jìn)行溫室內(nèi)太陽(yáng)輻射能的收集與利用,白天利用循環(huán)的流體介質(zhì)不斷將到達(dá)集熱板表面的太陽(yáng)輻射能吸收并蓄積起來(lái),夜晚再通過(guò)流體的循環(huán)流動(dòng)釋放熱量,熱能蓄積釋放的效率成倍提升,溫室溫度環(huán)境可調(diào)控水平顯著提升[19-20]。
本試驗(yàn)?zāi)康氖翘骄看罂缍戎鲃?dòng)蓄能型溫室冬季的綜合使用性能,以期為中國(guó)溫室設(shè)計(jì)提供新的思路,為推廣提供理論依據(jù)。
1.1 試驗(yàn)溫室設(shè)計(jì)
試驗(yàn)在北京市順義區(qū)大孫各莊鎮(zhèn)中國(guó)農(nóng)業(yè)科學(xué)院試驗(yàn)基地進(jìn)行(緯度40°13′N(xiāo),經(jīng)度116°65′E)。2014年12月5日至2015年2月5日對(duì)大跨度主動(dòng)蓄能型溫室(試驗(yàn)溫室)和日光溫室(對(duì)照溫室)的室內(nèi)溫濕度進(jìn)行測(cè)量。大跨度主動(dòng)蓄能型溫室采用拱型鋼骨架結(jié)構(gòu),單層PO(polyolefin)薄膜覆蓋,厚度0.08 mm。試驗(yàn)溫室長(zhǎng)60 m,跨度20 m,脊高4.5 m,有立柱,強(qiáng)度滿足北京地區(qū)恒載荷、雪載荷、南風(fēng)載荷和北風(fēng)載荷4種不利載荷組合的承壓要求。試驗(yàn)溫室下沉0.5 m,基礎(chǔ)四周有厚10 cm的聚苯板保溫層進(jìn)行保溫,以提高溫室冬季保溫,夏季隔熱的能力[21];北墻結(jié)構(gòu):內(nèi)層厚24 cm的紅磚與外層厚10 cm的聚苯板,更好地發(fā)揮墻體保溫蓄熱能力[22-23];南墻為中空PC(polycarbonate)陽(yáng)光板,厚度1 cm,采用透明材料可有效減少南墻遮光。對(duì)照溫室為傳統(tǒng)日光溫室,東西走向,長(zhǎng)度60 m,跨度8 m,脊高3.8 m;北墻結(jié)構(gòu):內(nèi)層厚12 cm紅磚,中間厚10 cm聚苯板,外層厚24 cm紅磚。試驗(yàn)溫室單體體積相比于日光溫室增大3倍以上,室內(nèi)氣候穩(wěn)定,抵御外界不利天氣的能力提高。試驗(yàn)溫室南北走向,東西相鄰兩棟溫室間距僅2 m,綜合考慮溫室墻體占地等因素,其土地利用率[8]仍高達(dá)87.4%,相比于傳統(tǒng)日光溫室的30%~45%,提高一倍以上。具有可移動(dòng)的內(nèi)保溫幕(綴鋁膜)與外保溫被(綜合傳熱系數(shù)為1.2 W/(m2.K))系統(tǒng),保溫性能良好,且卷放全自動(dòng)控制,內(nèi)保溫幕室內(nèi)凈高3.5 m。試驗(yàn)溫室雙坡面結(jié)構(gòu),使白天日光最大限度射入,夜間內(nèi)保溫幕和外保溫被展開(kāi),盡可能減少熱量散失。圖1為試驗(yàn)溫室和對(duì)照溫室的示意圖。
測(cè)試期間試驗(yàn)溫室內(nèi)保溫幕和外保溫被的揭開(kāi)與覆蓋模式:8:30揭開(kāi)東屋面保溫被和內(nèi)保溫幕,為防止冬季早晨溫室溫度下降過(guò)快,9:30再揭開(kāi)西屋面保溫被;15:30覆蓋溫室東屋面保溫被,為增加進(jìn)光量,16:30覆蓋西屋面保溫被和內(nèi)保溫幕。對(duì)照日光溫室8:30揭開(kāi)保溫被,16:30覆蓋保溫被。根據(jù)天氣狀況,揭放時(shí)間有小幅度調(diào)整。大跨度主動(dòng)蓄能型溫室和對(duì)照日光溫室均采用地膜覆蓋,采用袋式基質(zhì)栽培方式,種植作物為番茄(品種:大豐收,solanum lycopersicum),2014年11月30日定值,株距33 cm,因人工操作需求,行距為0.6和1 m相間排列,栽培密度6株/m2。
圖1 大跨度主動(dòng)蓄能型試驗(yàn)溫室和對(duì)照日光溫室示意圖Fig.1 Schematic diagram of experimental large-scale greenhouse with active heat storage system and Chinese solar greenhouse
1.2 主動(dòng)蓄放熱系統(tǒng)設(shè)計(jì)
主動(dòng)蓄放熱系統(tǒng)應(yīng)用于大跨度主動(dòng)蓄能型溫室,該系統(tǒng)白天收集多余的太陽(yáng)輻射熱能,夜間釋放能量用于溫室加溫。
1.2.1 系統(tǒng)組成
系統(tǒng)分3個(gè)部分,如圖2所示:1)主動(dòng)蓄放熱系統(tǒng)集放熱板,由2層厚0.15 mm的黑色塑料膜及厚20 mm的聚苯保溫板組成;2)地下蓄熱水池,2個(gè)水池有效蓄水體積均為8 m3,位于溫室中間部位。2個(gè)水池先后進(jìn)行熱量的蓄積,以實(shí)現(xiàn)低溫水循環(huán)吸收太陽(yáng)輻射熱,進(jìn)而提高系統(tǒng)集熱效率;夜間先后進(jìn)行循環(huán)放熱,以實(shí)現(xiàn)高溫水循環(huán)放熱,增大水溫與室溫溫差,提高放熱效率。蓄熱水池主體材料為厚15 cm的普通黏土磚墻,外表面緊貼10 cm厚聚苯板,內(nèi)表面涂抹厚0.3 cm防滲水泥砂漿,水池為地下式,留有直徑為0.6 m的工作井,不影響地上種植(如圖3);3)2臺(tái)1.5 kW的循環(huán)水泵及循環(huán)管路。
圖2 主動(dòng)蓄放熱系統(tǒng)構(gòu)成圖Fig.2 Schematic diagram of active heat storage and release system
圖3 蓄熱水池示意圖Fig.3 Schematic diagram of heat storage water tank
50塊主動(dòng)蓄放熱系統(tǒng)集放熱板(長(zhǎng)2 m,寬1.35 m),朝南安裝在大跨度主動(dòng)蓄能型溫室中,如圖4所示:1)9塊垂直安裝在北墻,底部距離地面0.4 m;2)6塊垂直安裝在南墻里側(cè),底部距地面1 m;3)在溫室南北向中部,從西向東依次安裝6塊,傾角為55°;4)26塊安裝在距溫室立柱東西兩側(cè)5 m處,從北向南依次安裝,間距3.75 m,傾角55°,保證集熱板冬季最大限度接受太陽(yáng)能[24-25],綜合考慮前后集放熱板不遮陰以及標(biāo)準(zhǔn)管件用料最省等因素來(lái)確定安裝角度和間距。冬至日正午光照最強(qiáng)時(shí),由于集放熱板的遮擋,試驗(yàn)溫室地面面積的15%處于陰影之中,即集放熱板的間距部分,為充分利用這部分空間,在集放熱板的間距空地處,使用基質(zhì)種植低矮喜陰葉菜。
圖4 主動(dòng)蓄放熱系統(tǒng)裝置Fig.4 Active heat storage and release system
1.2.2 系統(tǒng)運(yùn)行模式
主動(dòng)蓄放熱系統(tǒng)的控制原則:在集熱階段根據(jù)循環(huán)水溫適時(shí)切換蓄熱水池,保證水溫始終低于室溫,達(dá)到較高的集熱效率;在放熱階段根據(jù)循環(huán)水溫適時(shí)切換蓄熱水池,保證水池可以提供足夠的熱量,進(jìn)行空氣增溫。
因此根據(jù)蓄熱水池水溫,采用時(shí)間、室溫和水溫協(xié)同控制的方法,系統(tǒng)運(yùn)行分為以下3個(gè)階段:
1)9:30當(dāng)內(nèi)保溫幕和外保溫被完全揭開(kāi)后,開(kāi)啟循環(huán)水泵,運(yùn)行主動(dòng)蓄放熱系統(tǒng),循環(huán)水池1中水進(jìn)行蓄熱。
2)當(dāng)水池1中水溫大于22℃時(shí),循環(huán)水池2中水進(jìn)行蓄熱;16:30內(nèi)保溫幕與外保溫被覆蓋后,停止運(yùn)行主動(dòng)蓄放熱系統(tǒng)。
3)夜間當(dāng)室內(nèi)氣溫低于10℃時(shí),運(yùn)行主動(dòng)蓄放熱系統(tǒng)進(jìn)行增溫,先循環(huán)水池1中水進(jìn)行增溫;當(dāng)水池1中水溫低于16℃時(shí),切換水池2中水進(jìn)行循環(huán)放熱增溫;當(dāng)水池2中水溫低于16℃時(shí),關(guān)閉主動(dòng)蓄放熱系統(tǒng)。
1.3 測(cè)點(diǎn)布置與試驗(yàn)儀器
大跨度主動(dòng)蓄能型試驗(yàn)溫室室內(nèi)溫濕度測(cè)點(diǎn)布置:距北墻30 m處,東西向截面布置5個(gè)測(cè)點(diǎn)(如圖5所示)。在試驗(yàn)溫室中部沿南北向過(guò)道,距離北墻9、30、51 m處分別布置3個(gè)測(cè)點(diǎn),測(cè)點(diǎn)距地面高度1.5 m。室外距離溫室西側(cè)5 m,距地面2 m處,布置1個(gè)溫濕度測(cè)點(diǎn)。在兩個(gè)蓄熱水池的幾何中心各布置一個(gè)溫度測(cè)點(diǎn)。水泵耗電量采用電表讀取。
對(duì)照日光溫室室內(nèi)布置兩個(gè)溫濕度測(cè)點(diǎn):測(cè)點(diǎn)分別距東側(cè)山墻20、40 m,距北墻3 m,距地面1.5 m。所有溫濕度測(cè)點(diǎn)均裝有自然通風(fēng)防輻射罩。
圖5 距北墻30m處東西向截面上溫濕度測(cè)點(diǎn)分布Fig.5 Locations of temperature/RH sensors in cross section at distance of 30 m from north wall
選用美國(guó)文森公司生產(chǎn)的HOBO儀器進(jìn)行溫室內(nèi)外的空氣溫濕度測(cè)量,溫度測(cè)試精度±0.2℃,濕度測(cè)試精度± 2.5%,并做防輻射處理。水溫測(cè)量選用T型熱電偶作為溫度傳感器,精度為±0.2℃,數(shù)據(jù)采集儀選用美國(guó)坎貝爾公司生產(chǎn)的CR1000,用于自動(dòng)記錄各傳感器采集的數(shù)值,數(shù)據(jù)采集間隔為10 min。
1.4 系統(tǒng)節(jié)能效果分析
主動(dòng)蓄放熱系統(tǒng)白天收集的熱量Qs和夜間放出的熱量Qr,kJ。按照下式計(jì)算[19]:
式中ρw為水的密度,取1.0×103kg/m3;Cw為水的比熱容,取4.2 kJ/(kg.℃);ΔT1,s、ΔT2,s,ΔT1,r、ΔT2,r,分別為系統(tǒng)白天集熱階段、系統(tǒng)夜間放熱階段蓄水池Ⅰ、Ⅱ水溫變化,℃;V1、V2分別為蓄水池Ⅰ、Ⅱ?qū)嶋H蓄水量,m3。
為進(jìn)一步分析主動(dòng)蓄放熱系統(tǒng)的節(jié)能率,筆者定義主動(dòng)蓄放熱系統(tǒng)的性能系數(shù)為 COP(coefficient of performance),即是夜間系統(tǒng)的放熱量Qr與Ewp之比[26]:
式中Ewp為主動(dòng)蓄放熱系統(tǒng)夜間放熱階段循環(huán)水泵的耗電量,kJ。
節(jié)能率[27]的計(jì)算:在計(jì)算主動(dòng)蓄放熱系統(tǒng)加溫與燃煤鍋爐加溫的節(jié)能率時(shí),可以將主動(dòng)蓄放熱系統(tǒng)水泵的耗電量折算為標(biāo)準(zhǔn)煤,根據(jù)主動(dòng)蓄放熱系統(tǒng)加溫獲得的熱量折算為采用燃煤鍋爐加溫所需的標(biāo)準(zhǔn)煤,再將兩者進(jìn)行對(duì)比。
溫室獲得的熱量Qr若為燃煤鍋爐獲得,則用燃煤鍋爐時(shí)消耗的標(biāo)準(zhǔn)煤通過(guò)下式計(jì)算:
式中QH為標(biāo)準(zhǔn)煤熱值,取29 260 kJ/kg;ηg為燃煤鍋爐效率,取0.7;ηw為官網(wǎng)輸送效率,取0.95。
主動(dòng)蓄放熱系統(tǒng)水泵消耗電能Ewp轉(zhuǎn)化為標(biāo)準(zhǔn)煤,則計(jì)算公式為:
式中ηd為火力發(fā)電廠的效率,取0.35;ηp為輸配電效率,取0.95。
則主動(dòng)蓄放熱系統(tǒng)與燃煤鍋爐相比的節(jié)能率η,通過(guò)下式計(jì)算:
試驗(yàn)選取2015年1月17日-2015年1月20日連續(xù)3 d的數(shù)據(jù)進(jìn)行分析。為便于分析大跨度主動(dòng)蓄能型溫室環(huán)境及保溫性能規(guī)律,本文將08:30-次日08:30作為一個(gè)周期。第一天為晴天高溫(1月17日-18日),第二天為多云低溫(1月18日-19日),第三天為晴天低溫(1月19日-20日),是北京冬季的典型天氣。
2.1 不同天氣狀況下大跨度主動(dòng)蓄能型溫室溫濕環(huán)境分析
2.1.1 不同天氣狀況下大跨度主動(dòng)蓄能型溫室和日光溫室室溫比較
圖6為1月17日到1月20日大跨度主動(dòng)蓄能型試驗(yàn)溫室與對(duì)照日光溫室室內(nèi)外溫度變化曲線。白天正午當(dāng)對(duì)照日光溫室溫度高于30℃時(shí),需人工開(kāi)啟溫室頂部通風(fēng)口進(jìn)行通風(fēng)降溫。而大跨度主動(dòng)蓄能型溫室白天無(wú)需通風(fēng)降溫。盡管對(duì)照日光溫室采取通風(fēng)措施,白天正午其極端高溫仍比大跨度主動(dòng)蓄能型溫室高3~5℃。在圖6(b)中可以看出2棟溫室在早上10點(diǎn)左右室溫才逐漸上升,主要由于第二天為多云天氣,早上保溫被的揭開(kāi)時(shí)間推遲。同樣的現(xiàn)象可以在圖7(b)中看到,室溫上升比另外2天滯后。前半夜大跨度主動(dòng)蓄能型溫室未開(kāi)啟主動(dòng)蓄放熱系統(tǒng)之前,其室溫和對(duì)照日光溫室基本一致,當(dāng)運(yùn)行主動(dòng)蓄放熱系統(tǒng)時(shí),大跨度主動(dòng)蓄能型溫室室溫緩慢上升并趨于穩(wěn)定,而對(duì)照日光溫室溫度逐漸下降。18日、19日、20日早上揭開(kāi)內(nèi)保溫幕和外保溫被時(shí),大跨度主動(dòng)蓄能型溫室室溫分別為10.3、9.5、10.4℃,日光溫室室溫為7.7、6.7、7.5℃,溫差分別為2.6、2.8、2.9℃。且不管是晴天或多云,大跨度主動(dòng)蓄能型溫室夜間室內(nèi)溫度均維持在10℃以上,室內(nèi)外溫差可達(dá)到19.3℃。晴天(如圖6a,6c)大跨度主動(dòng)蓄能型溫室夜間室溫平均比日光溫室高1.5~3.1℃,比室外高13.9~19.3℃;陰天(如圖6b)室溫平均比日光溫室高1.2~2.8℃,比室外高12.5~18.9℃。可見(jiàn)大跨度主動(dòng)蓄能型溫室相比于傳統(tǒng)磚墻日光溫室,室內(nèi)氣候穩(wěn)定,無(wú)極端高溫與低溫,保溫性能良好。
圖6 不同天氣狀況下試驗(yàn)溫室與對(duì)照溫室室內(nèi)溫度以及室外溫度比較Fig.6 Air temperature comparison in experimental greenhouse,reference greenhouse and outside under different weather conditions
2.1.2 不同天氣狀況下大跨度主動(dòng)蓄能型溫室南北向溫度分布
圖7為1月17日至1月20日試驗(yàn)溫室南北方向溫度分布情況。早上8:30揭開(kāi)保溫被至14:30時(shí),溫室南部和北部升溫較中部快,比中部高0.5~3.3℃,主要由于南部為PC中空陽(yáng)光板,且溫室南北走向,太陽(yáng)光通過(guò)南部陽(yáng)光板照射溫室的入射角小,北部后墻會(huì)吸收太陽(yáng)能并向室內(nèi)釋放熱量。北部與南部在正午12點(diǎn)之前差別不大,但在正午時(shí)刻也較南部低2.5℃左右,陰天溫度差異較晴天小。14:30至16:30南北向溫度無(wú)明顯差異,16:30覆蓋內(nèi)保溫幕和外保溫被后,夜間北部溫度較南部和中部平均低0.9℃。夜間南北向溫差僅為0.9℃,溫室長(zhǎng)度60 m,溫度梯度較小,夜間室內(nèi)南北向溫度分布均勻。
圖7 不同天氣狀況下大跨度主動(dòng)蓄能型試驗(yàn)溫室南北向溫度分布Fig.7 Air temperature distribution of experimental greenhouse in south-north direction under different weather conditions
2.1.3 不同天氣狀況下大跨度主動(dòng)蓄能型溫室與日光溫室相對(duì)濕度比較
圖8為大跨度主動(dòng)蓄能型試驗(yàn)溫室與對(duì)照日光溫室室內(nèi)相對(duì)濕度對(duì)比曲線,在圖8(b)中可以看出2棟溫室在早上10點(diǎn)左右相對(duì)濕度才逐漸下降,主要由于第二天為多云天氣,早上保溫被的揭開(kāi)時(shí)間推遲。大跨度主動(dòng)蓄能型溫室和日光溫室白天相對(duì)濕度基本一致,當(dāng)內(nèi)保溫幕與外保溫被覆蓋后,2溫室相對(duì)濕度迅速上升,但大跨度主動(dòng)蓄能型溫室夜間相對(duì)濕度比日光溫室平均低7%~10%。大跨度主動(dòng)蓄能型溫室和對(duì)照日光溫室作物種植密度均為6株/m2,均定植于2014年11月30日。其相對(duì)濕度低的主要原因是大跨度主動(dòng)蓄能型溫室夜間溫度相比于日光溫室高3℃左右,而且溫室單體大,從而導(dǎo)致試驗(yàn)溫室相對(duì)濕度相比于日光溫室降低10%,這對(duì)減少作物病蟲(chóng)害,降低發(fā)病率,對(duì)提高產(chǎn)量有重要影響[28-29]。
圖8 不同天氣狀況下試驗(yàn)溫室與對(duì)照溫室室內(nèi)相對(duì)濕度比較Fig.8 Relative humidity comparison between experimental and reference greenhouses under different weather conditions
2.2 主動(dòng)蓄放熱系統(tǒng)能量分析
主動(dòng)蓄放熱系統(tǒng)白天收集的熱量、晚上釋放的熱量、系統(tǒng)COP值(根據(jù)公式3)和節(jié)能率η(根據(jù)公式4-6)如表1所示。1月18日為多云,白天太陽(yáng)輻射較弱,主動(dòng)蓄放熱系統(tǒng)蓄熱量較少,但是夜間系統(tǒng)放熱量大于白天集熱量,這說(shuō)明前期能量的蓄積可用于陰天能量不足的供給,而晴天夜間放熱量均小于白天集熱量。試驗(yàn)結(jié)果表明,系統(tǒng)放熱量取決于白天集熱量,同時(shí)受制于夜間室內(nèi)氣溫,室溫與循環(huán)水溫的溫差越大,放熱量越多。主動(dòng)蓄放熱系統(tǒng)運(yùn)行時(shí)平均COP在3.4~4.2之間,平均每天能耗0.013 kWh/m2,且相比于燃煤鍋爐加溫系統(tǒng),平均節(jié)能率為47%,節(jié)能效果顯著。
表1 主動(dòng)蓄放熱系統(tǒng)的性能參數(shù)Table 1 Performance parameters of active heat storage and release system
2.3 大跨度主動(dòng)蓄能型溫室與日光溫室建造成本分析
經(jīng)統(tǒng)計(jì)分析,大跨度主動(dòng)蓄能型溫室和日光溫室的建造工料和人工成本如表2所示。大跨度主動(dòng)蓄能型溫室每平方米建造費(fèi)用為307.2元,日光溫室每平方米的建造成本為451.7元。可見(jiàn)大跨度主動(dòng)蓄能型溫室在單位平方米的建造成本上比日光溫室減少144.5元。日光溫室土建和磚墻部分投資較多,因?yàn)榇罂缍戎鲃?dòng)蓄能型溫室北墻面積小且用磚少。其他部分投資,大跨度主動(dòng)蓄能型溫室均比日光溫室多,但大跨度主動(dòng)蓄能型溫室種植面積為日光溫室的2.5倍以上。
大跨度主動(dòng)蓄能型溫室和日光溫室均采用地膜覆蓋,使用基質(zhì)栽培番茄,種植密度均為6株/m2。日光溫室南側(cè)受屋面骨架高度限制,日光溫室內(nèi)部南側(cè)有1.5 m空地不能種植作物,也不能作為走廊。而大跨度主動(dòng)蓄能型溫室距東西側(cè)1 m處,高度為2.5 m,可進(jìn)行作物種植,亦可作為走廊。因此從生產(chǎn)效益來(lái)看,大跨度主動(dòng)蓄能型溫室作物種植面積大,室內(nèi)氣候穩(wěn)定,冬季夜間溫度比日光溫室平均高3℃左右,夜間室溫維持在10℃以上,相對(duì)濕度比日光溫室低約10%,更適宜作物生長(zhǎng),發(fā)病率減少,收益更好。
表2 大跨度主動(dòng)蓄能型溫室與日光溫室的建造工料與人工成本預(yù)算Table 2 Budget of materials and labor costs of experimental and reference greenhouses
本試驗(yàn)設(shè)計(jì)的大跨度主動(dòng)蓄能型溫室,解決了日光溫室土地利用率低和空間狹小,不便蔬菜立體化栽培、不能種植果樹(shù)等高大作物以及不利于機(jī)械化操作等問(wèn)題。室內(nèi)氣候穩(wěn)定,保溫蓄熱性能良好,節(jié)能高效,可實(shí)現(xiàn)冬季果菜類(lèi)作物生產(chǎn)。內(nèi)保溫幕、外保溫被以及上下通風(fēng)口的靈活管理,更好地實(shí)現(xiàn)不同季節(jié)的生產(chǎn)要求。
試驗(yàn)結(jié)果表明:1)大跨度主動(dòng)蓄能型溫室土地利用率高達(dá)87.4%,節(jié)約土地資源;2)大跨度主動(dòng)蓄能型溫室無(wú)論在晴天還是陰天,夜間平均室溫均能維持在10℃以上,無(wú)極端低溫。且室內(nèi)溫度分布均勻,室內(nèi)外溫差可達(dá)19.3℃,溫室保溫性能較好。夜間室內(nèi)相對(duì)濕度平均比日光溫室低7%~10%,無(wú)高濕現(xiàn)象;3)大跨度主動(dòng)蓄能型溫室建造成本每平米307.2元,比傳統(tǒng)磚墻日光溫室低144.5元;4)無(wú)論晴天和陰天,主動(dòng)蓄放熱系統(tǒng)平均COP均能維持在3.4~4.2,平均每天加溫能耗0.013 kWh/m2,相比于傳統(tǒng)燃煤鍋爐加溫系統(tǒng),平均節(jié)能率為47%,節(jié)能顯著。因此,綜合成本、保溫性能、經(jīng)濟(jì)環(huán)境效益,大跨度主動(dòng)蓄能型溫室值得推廣和大面積應(yīng)用。
在下一步研究中,將重點(diǎn)考慮大跨度主動(dòng)蓄能型溫室夏季室內(nèi)降溫問(wèn)題,分析作物長(zhǎng)勢(shì)、產(chǎn)量等作物狀況,從而使大跨度主動(dòng)蓄能型溫室實(shí)現(xiàn)全年生產(chǎn),再進(jìn)一步提高資源利用效率。
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Evaluation on heat preservation effects in micro-environment of large-scale greenhouse with active heat storage system
Zhou Sheng,Zhang Yi,Cheng Ruifeng,Yang Qichang※,Fang Hui,Zhou Bo,Lu Wei,Zhang Fang
(1.Institute of Environment and Sustainable Development in Agriculture,Chinese Academy of Agricultural Sciences,Beijing 100081,China; 2.Key Labatory of Energy Conservation and Waste Management of Agricultural Structures,Ministry of Agriculture,Beijing 100081,China)
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 2 rows 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(xiāo),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 was 0.013 kWh/m2during 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/m2lower 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.
greenhouses;temperature;environmental regulations;land utilization efficiency;large scale;active heat storage and release system;relative humidity;Chinese solar greenhouse
10.11975/j.issn.1002-6819.2016.06.030
S625.2,S625.4
A
1002-6819(2016)-06-0218-08
2015-09-09
2016-01-22
國(guó)家科技支撐計(jì)劃(2014BAD08B02);公益性行業(yè)(農(nóng)業(yè))科研專(zhuān)項(xiàng)(201203002);基本科研業(yè)務(wù)費(fèi)(BSRF201405);國(guó)家自然科學(xué)基金項(xiàng)目(51508560)
周 升(1991-),江蘇徐州人,主要從事設(shè)施農(nóng)業(yè)環(huán)境工程方面研究。北京 中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)環(huán)境與可持續(xù)發(fā)展研究所,100081。Email:1208915734@qq.com
※通信作者:楊其長(zhǎng)(1963-),安徽無(wú)為人,博士,研究員,博士生導(dǎo)師,主要從事設(shè)施園藝環(huán)境工程研究。北京 中國(guó)農(nóng)業(yè)科學(xué)院農(nóng)業(yè)環(huán)境與可持續(xù)發(fā)展研究所,100081。Email:yangq@ieda.org.cn
農(nóng)業(yè)工程學(xué)報(bào)2016年6期