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Journal of the Korean Society of Agricultural Engineers Vol. 52, No. 2, pp. 67~73, March, 2010 적외선열화상분석을통한온실의열손실진단및평가 Heat Loss Audit and Assessment of the Greenhouses Using Infrared Thermal Image Analysis 문종필 * 윤남규 *, 이성현 * 김학주 * 이수장 * 김영화 * Moon, Jong Pil * Yun, Nam Kyu *, Lee, Sung Hyoun * Kim, Hak Joo * Lee Su Jang * Kim, Young-Hwa * ABSTRACT Unlike Urban building, horticultural facilities has a lot of heat loss through plastic or glass covering material which could be much influential to growing plant and consuming energy for heating greenhouse. In many cases, heat loss from a break of cover, a gap of joint sealing, the entrance to greenhouse and windows for ventilation are the main factors considered in calculating the heating load for horticultural facilities. however the normal observation through human eye and digital camera could not recognize where the heat loss occurred. but the infrared thermal image camera with detecting thermal difference could be very effective for noticing heat loss by analyzing infrared thermal image. In this study, greenhouse structure, covering material, internal and external provisions for Horticultural facilities were surveyed in different sites and Infrared thermal camera shooting and image analysis were performed for auditing heat loss from cultivation facilities The results from this study were that unexpected heat loss had been noticed in 7 representative cases of greenhouse such as side wall covered with single or double plastic, and the joint of horizontal thermal curtain, roof without horizontal thermal curtain, entrance to greenhouse, windows for ventilation. the most important factors for keeping heat energy were whether the horizontal thermal curtain with multifold thermal material was installed or not. The internal or external covering using multifold thermal curtain proved to be the most effective ways to keep heat energy from losing through heat transmission, heat radiation. from inside to outside the horticultural facilities. Keywords: Heat loss; Infrared Thermal image analysis; Horticultural facilities; Multifold thermal screen 국제원유가격의고공행진이지속되면서국내유가에도큰영향을미치고있다. 이에따라유류를많이사용하는시설농업의경영비중에서난방비가차지하는비중이 30~40 % 를차지하고있으며, 일부작물은경영비의 50% 이상이난방비로지출됨에따라 (RDA, 2008) 생산비절감과우리농산물의국제경쟁력제고를위해서는무엇보다도난방비의비중을줄이는것이가장시급하다고하겠다. 난방비의비중을줄이기위한근본적인대책으로는바이오매스, 지열, 태양열등의신재생에너지를이용한난방기술을도입하여수입에의존하고있는화석에너지의가격상승에의한난방비부담증가의고리를원천적으로차단할수있는기반 * Corresponding author. Tel.: +82-031-290-1822 Fax: +82-031-290-1840 E-mail address: ecas21@korea.kr 2010 2 24 2010 3 23 2010 3 24 을마련하는것이라할수있다. 그러나이러한신재생에너지의농업적이용은여러가지이유로당장현실화되기에는어려운과제이므로농업시설의난방비를절감하기위한현실적인대책으로는우선농업시설의에너지소비및손실형태를과학적으로조사분석하여농업시설에서소비되는에너지를최소화하기위한에너지이용효율개선방안을제시하는것이시급한과제라고할수있다. 특히, 비닐하우스나축사등농업시설은일반건축물에비해단열과보온력이취약하므로에너지절감을위해서는무엇보다도공급된열의손실경로와그원인을파악하여관리할수있도록방안을제시하는것이무엇보다중요하다. 이러한농업시설에서의에너지진단은에너지이용효율의향상과에너지절감을위해보온및단열성능, 열손실, 난방시스템의효율등을점검하여문제점에대한과학적이고실용적인개선방안을제시하는시설농가의합리적에너지경영을위한기술컨설팅분야로새롭게주목받고있다 (RDA, 2009). 본연구는적외선열화상처리장치를이용하여온실의열손실을진단하고평가하여시설원예의에너지절감과관련된기초자료를제공하고자수행되었다. 67

적외선열화상분석을통한온실의열손실진단및평가 Table 1 Heat transmission coefficient for covering materials (RDA, 2009) 최근적외선열화상카메라를농업분야에서가축의질병진단및화재예방등의목적으로사용하고있으며온실의열손실진단이나열환경및공조시스템의평가를위해이용하는경우는극히일부분을차지하고있다. 본연구에서는농업시설의에너지진단과평가기법의표준화, 농업시설의에너지소비해석프로그램개발, 농업시설의열환경평가를통한에너지컨설팅시스템구축등의일부분으로적외선열화상분석을이용하였다 (Moon et al., 2009; Yun et al., 2009). 연구에사용한적외선열화상카메라는 AVIO TVS-600 모델 (NEC, 일본 ) 로써측정온도범위는 -40~1,100 C이고해상도는 0.15 C 30프레임풀컬러를지원하는장비이다. 열화상촬영이외에도온실의열손실계산과열환경분석을위하여시설규격, 단열및피복재, 환기장치, 난방시스템용량및배치등관련사항들을조사하였다. 온실의열손실손실진단및실태조사는경기화성, 경남창원, 전남곡성, 제주지역을중심으로비닐온실 32 시설유리온실 4 시설을조사하였으며그중 9 시설의측창열화상촬영사진을분석하여산정된열손실량과이론식에의해계산한관류전열손실량을비교하여실측값과이론값사이의상관관계식을도출하였다. 관류전열손실량은온실내부에서복사및대류열전달에의하여피복재내표면에전달된열이전도열전달에의하여피복재를통과한후피복재외표면에서다시복사및대류열전달에의해외기로방출되는열량으로다음과같이계산 (Kim et al., 2002) 하며계산에사용된계수는 Table 1, 2와같다. q t =h t (T s -T d)(1-f r) (1) h t : 관류열전달계수 (kcal m -2 h -1 C -1 ) T s: 난방설정온도 ( C) T d: 설계외기온도 ( C) f r : 보온피복의열절감률우리주위에존재하는모든물체들은모두절대온도영도 (-273 C) 이상의온도를갖고있으며, 각물체에서는그온 Covering material Heat transmission coefficient (kcal m -2 h -1 C -1 ) Single glass 5.0~5.4 Single plastic 5.5~5.8 Double acrylic 2.6~3.0 Double plastic, Single polyethylene 3.4~3.8 Double glass 2.6~3.0 Single glass, Single thermal screen 2.6~3.0 Double plastic, Single thermal screen 1.9~2.1 Table 2 Saving ratio of heat loss for covering materials (Kim et. al., 2002; RDA, 2009) Heat insulating Single covering Double covering Single thermal screen Doble thermal screen External covering Covering material Saving ratio of heat loss (%) Glass Plastic Glass, Pastic - - Glass, PVC film 40 45 PE film 35 40 PVC film 35 40 PE film 30 35 Non-woven fabric 25 30 Alluminum mix film 40 45 Alluminum deposition film 50 55 Multifold thermal screen 55 60, PE film+non-woven fabric 45 45 PVC film+pe film, PVC film+non-woven fabric 50 50 Double PVC film, PVC film + Alluminum 55 55 PE film+alluminum film 65 65 Multifold thermal screen+non-woven fabric (PE film) 70 70 Multifold thermal screen 60 65 도에상응하는열에너지 ( 적외선 ) 를방사하고있다. 물체에서방사되는적외선은열화상카메라광학렌즈를통과하여카메라내부의 Detector 로모아지며 Detector 는적외선을전기신호로변화하고이것을온도에해당하는화상으로표현한다. 즉물체의표면온도를수만개의점으로온도에따라그림처럼표현할수있다. 1800년에 William Herschell이가시스펙트럼의끝인파장측으로부터열효과가큰부분이있음을발견하고, 1835년에 A. Amphere가이것이가시광선과같은광파로되어있음을발표하여현재의적외선에대한기초를구축하게되었으며적외선열화상카메라는일반카메라처럼작동하지 68

문종필윤남규이성현김학주이수장김영화 만영상이일반적인 light 가아닌 infrared energy (heat) 를검출한다. 적외선열화상촬영에의한온실피복특히측창에서의온실외부로의열방출량을다음과같은스테판-볼츠만의복사방출열량계산식에의해산정하였다. Q=σ A (T 1 4 -T 2 4 ) (2) Q = 방출열량 (kcal/h) σ : Stefan-Boltzmann의상수 (= 4.88 10-8 kcal h -1 m 2 K 4 ) A : 전열면적 (m²) T : 온실피복표면절대온도 (K) T : 설계기온절대온도 (K) Fig. 1 External Infrared thermal image-back side heat loss of vinyl house Fig. 1의피복형태는 PO필름 1중피복 (0.1 mm) 이며전후면보온재로부직포를사용하고있으며 Fig. 2는 PE필름 1중피복 (0.1 mm) 과 2층수평커튼으로보온을하고있는온실이다. 두온실은모두전남곡성지역에위치하고있으며, 재배작물은장미로동일하고, 온풍난방으로가온을실시하고있었다. Fig. 1, 2와같이단동및연동형비닐하우스의피복재는얇은 (0.05~0.1 mm) PE필름을사용하는경우가대부분이고내부보온커튼을설치하더라도단열성능이충분하지않은경우가대부분이어서난방시많은열이손실되고있었다. 또한보온커튼이노후되어제봉선등에서단열성능이저하되는문제가관측되었다. 이러한비닐하우스에서는시설의보온성이낮아손실되는열량이막대하므로이중피복을추가설치하고, 알루미늄보온스크린또는다겹보온커튼의설치로시설의보온력을높여야하며, 측면수평보온커튼과수직보온커튼이만나는부분의틈새가발생하지않도록기밀유지에신경을써서시공을하여야한다. Fig. 3은경남창원의국화재배온실로 PE필름으로 2중피복 Fig. 2 External infrared thermal Image-side of vinyl house Fig. 3 External infrared thermal image side of vinyl house (0.1 mm) 을하였고전후면, 측면차광망과다겹보온재로내피피복을한상태이다. 난방은갈탄온수보일러를사용하여 FCU 에의해온실내부를온풍가온하는방식을사용하였다. Fig. 3에서알수있듯이보온커튼이설치되어있더라도실내설정온도가 26 C로높아외기온이낮은경우에는보온커튼 Journal of the Korean Society of Agricultural Engineers, 52(2), 2010. 3 69

적외선열화상분석을통한온실의열손실진단및평가 층전후의온도차가크므로열손실이많이발생하게되며, 특히온실내부지중온도와외부지온의편차가커지면온실둘레를따라지중전도에의한열손실이많이발생한다. 이온실의경우, 측면의단위면적당열손실이 57 kcal m -2 h -1 인것에비해바닥면의단위면적당열손실은 34 kcal m -2 h -1 로실내설정온도가낮은다른온실에비해상대적으로높았고, 전체열손실량에대한비율도 26 % 로상대적으로높았다. 이러한경우에는측창하부의고정피복부분과기초부분의단열재피복및지중매입으로열손실을감소시키고, 작물이심어지지않는통로는부직포등으로피복하여열손실을감소시켜야할것으로판단되었다. Fig. 4. 5는경남창원의파프리카재배유리온실로서 3층수평커튼 ( 알루미늄스크린, 다겹보온커튼, 미니마트 ) 를설치하여보온을실시하였다. 난방은중유온수보일러와방열핀이없는방열관을온실내바닥면에배관하여실시하고있었다. 열화상분석결과전면연동연결부, 서쪽수평커튼일부와지붕면틈새등을통한열손실이상대적으로큰것으로나타났으며온실둘레의하부콘크리트면을통한열손실이발생하고있다. 틈새부위에대한개선과일부손상된부분은보수가필요하며온실둘레의하부콘크리트면을통한열손실은현재상태로는단열보강을하기어려우므로온실내부둘레에다겹보온재등을이용하여지면피복과하부면보온피복을실시하는것이좋을것으로판단되었다. Fig. 6, 7은제주의백합재배유리온실이며전후면과측벽을 PE필름 2겹과부직포로보온피복하였으며상부에는수평커튼대신 PE필름으로보온용내부터널을설치하였다. 난방은경유온수보일러와전기온풍기를이용하고있었다. 식 (1) 에의한열손실량계산결과지붕면의열손실이전체의 79 % 로가장많은양을차지하고있으며, 지붕환기창, 측벽과지붕이만나는부위등에서틈새에의한열손실이크게발생하고측면혹은전후면에압력차에의한공기유입구를설 Fig. 4 External infrared thermal image-front side of glasshouse Fig. 6 External infrared thermal image-roof of glasshouse Fig. 5 External infrared thermal image-concrete base heat loss Fig. 7 External infrared thermal image-side of glasshouse 70

문종필윤남규이성현김학주이수장김영화 치한경우에는그틈새로인한환기열손실또한상대적으로크게발생하고있었다. 이경우단위면적당열손실량비교에서도지붕면이 62 kcal m -2 h -1 로측면보다약 1.4배높아다겹보온커튼혹은알루미늄보온스크린으로수평보온커튼을보강하여지붕면의열손실을 50 % 이상줄이면전체열손량도약 40 % 절감할수있을것으로판단되었다. Fig. 8 Plastic cover break heat loss 그밖에도거의대부분의조사대상온실에서전면하부및전면과측면등피복재의파손으로열손실이발생하고있으며출입구틈새로열손실이많이발생하고있으므로보온커튼과 Fig. 9 Entrance heat loss of vinyl house Fig. 10 Correlation curve data plot facilities No. 1 2 3 4 5 6 7 8 Table 3 Comparison of calculated heat transmission loss and Infrared thermal image heat loss Covering status (0.13mm) (outside: 0.2mm, inside : 0.10mm) 9 Single glass Insulation status (non-woven fabric) (non-woven fabric) (non-woven fabric) Single thermal screen External covering (PE + Alluminum) Triple thermal screen (Alluminum+Multifold thermal +Woven fabric) Calculated heat transmission loss (kcal/ h) Infrared thermal image heat loss (kcal/ h) Outside design temp. Setting temp. 190 55-13.1 C 18 C 162 27-15.5 C 12 C 177 29-15.5 C 12 C 53 0-6.2 C 23 C 48 0-6.2 C 19 C 57 2-6.2 C 26 C 48 0-6.2 C 17 C 168 36-15.5 C 12 C 46 3-6.2 C 22 C Journal of the Korean Society of Agricultural Engineers, 52(2), 2010. 3 71

적외선열화상분석을통한온실의열손실진단및평가 출입구에서의기밀을유지할수있도록보온재등을강화하고틈새를막아열손실을최소화해주어야할것으로판단되었다. 이러한틈새에의한열손실량은전체온실의열손실량에비해 10 % 내외의작은비중을차지하는부분이지만, 온실의막대한난방비를고려할때경영적측면에서결코무시될수없는중요한에너지절감실천사항이라고판단된다. 시설의피복재종류및피복방법에따른단위면적당측창에서의관류전열손실량과열화상촬영에의한방출열량은일정한상관관계 (Fig. 10) 를보이고있으며그상관관계식은다음과같다. 상관관계식 : Y = 49.04 + 4.53X - 0.03X 2 (r = 0.98) 여기서, Y = 관류전열손실량 (kcal m -2 h -1 ), X = 적외선열화상방출열량 (kcal m -2 h -1 ) Table 3에서외기의설계기온은조사온실이위치한지역의위험률 5 % 수준의설계기온을적용하였고, 실내설정온도는조사온실에서실제겨울철난방시야간설정온도를적용하였다. 비교결과, 열화상촬영에의한단위면적당방출열량은동일한부직포수평보온커튼을 2층으로설치하였을때 1중피복이 2중피복보다약 1.5~2.0배정도큰것으로나타났으며다겹보온커튼을 2층으로설치하였을경우또한다겹보온재로외면피복을한경우 1중피복과 2중피복모두방출열량이아주미세한것으로나타났다. 또한, 내부보온재에관계없이온실의열손실을줄이기위해서는피복재를반드시 2중으로설치하는것이필요하다. 또한고온재배를하는작물에있어서는다겹보온커튼을설치하여열손실을최소화하고부직포수평커튼의노후화로인하여열손실이심한온실은가급적다겹보온커튼으로교체하여사용하면열손실을최대한줄이고에너지효율을높일수있다. 원예시설의열손실을효율적으로파악하기위하여적외선열화상카메라를촬영하여가온상태의온실에대해열화상분석을실시하였다. 온실형태, 구조, 피복, 보온상태등에따라열화상분석에의해산정된단위면적당방출열량과난방부하량산정시고려되는관류전열손실량과의상관관계를분석하여회귀식으로제시하였으며촬영된열화상이미지분석을통하여온실에 서의열손실이많이발생되는유형에대한보완대책을제시하였으며그결과는다음과같다. 1. 열화상촬영에의해분석된방출열량을관류전열손실량과의상관관계식을도출하였고추후열화상촬영에의한온실에서의열손실량을추정하는데기초자료로서제시하였다. 2. 1중피복의온실에서는시설의보온성이낮아손실되는열량이막대하므로 2중피복을추가설치하고, 알루미늄보온스크린또는다겹보온커튼의설치로시설의보온력을높여야한다. 3. 유리온실둘레의하부콘크리트면을통한열손실이크며틈새부위에대한개선과일부손상된부분은보수가필요하며온실둘레의하부콘크리트면을통한열손실은온실내부둘레에다겹보온재등을이용하여지면피복과하부면보온피복이필요하다. 4. 수평보온커튼과수직보온커튼이만나는부분의틈새가커서많은열이손실되고있으므로틈새를최대한줄일수있도록하고파손된부분에단열성이높은피복재를사용하여열손실을줄여야한다. 5. 보온이잘되어있는경우라도실내설정온도가높아외기와의기온편차가크면열손실이많이발생하고특히온실기초주변을따라지중전열손실이많으며측면하부의측창아래쪽지상부의열손실이다른부위보다많은것으로나타났다. 측창하부의고정피복부분과기초부분의단열재피복및지중매입으로열손실을감소시키고, 작물이심어지지않는통로는부직포등으로피복하여열손실을감소시켜야한다. 6. 측면상부의수직보온커튼과수평보온커튼이만나는부분에틈이있어열손실이발생하고, 보온커튼의노후되어제봉선부분등의단열성능이저하되어열손실이발생하고있으므로보온커튼측면상부의수평보온커튼과수직보온커튼이만나는부분에따뜻한공기가집중하므로틈이발생하지않도록밀폐하여열손실을줄이고, 측면과전후면가장자리지면에보온재등을깔아지면으로의열손실을줄일필요가있다. 7. 유리온실내부에 PE필름 1층보온터널을설치하였을경우지붕면의열손실이가장많았으며지붕환기창과측벽과만나는부위에서열손실이가장많고다겹보온커튼혹은알루미늄보온스크린으로수평보온커튼을추가설치하여지붕면의열손실을 50 % 이상줄이면전체열손실량도약 40 % 를절감할수있다. 8. 피복재의파손으로열손실이발생하고있으며출입구틈새로다량의열손실이발생하고있으므로신속한피복재의보수및출입구에서의기밀을유지할수있도록보온재등을강화하고틈새를막아열손실을최소화해주어야한다. 72

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