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Research Article

Analysis of Test Operations Effect of Open-Closed Loops Complex Geothermal System Combined with Groundwater Well

지하수정호 결합 복합지열시스템의 시범운영 효과분석

Jae-Yong Song1
,
Ki-Joon Kim2
,
Geun-Chun Lee3
,
Gyo-Cheol Jeong4*
송 재용1
,
김 기준2
,
이 근춘3
,
정 교철4*
1SanHa Construction Co., Ltd., Director
2SanHa Engineering & Construction Co., Ltd., Executive Director
3SanHa Engineering & Construction Co., Ltd., Deputy General Manager
4Dept. of Earth and Environmental Sciences, Andong National University, Professor
1산하토건 주식회사, 상무
2주식회사 산하이앤씨, 전무
3주식회사 산하이앤씨, 차장
4안동대학교 지구환경과학과, 교수
* Corresponding Author
30 September 2018. pp. 475-488
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Abstract

This study evaluates geothermal system efficiency in terms of input power and heat exchange volume on the heat-source and load sides, by applying a combined open-closed type loop system comprising a geothermal system and a groundwater well to a cultivation site. In addition, this study analyzes the effects of heating and cooling for a complex geothermal system, by evaluating the temperatures of an external site and a cultivation site during operation. During cooling operations the heat exchange volume on the heat source side, average 90.0kW/h for an open type system with an input of 235L/minute groundwater, and 40.1kW/h for a closed type system with an input of 85L/minute circulating water, for a total average heat exchange volume of 130.1kW/h. The actual heat exchange volume delivered on the load side averages 110.4kW/h. The average EER by analysis of the geothermal system's cooling efficiency is 5.63. During heating operation analysis, the heat exchange volume on the heat source side, average 60.4kW/h in an open type system with an input of 266L/minute groundwater, and 22.4kW/h in closed type system with an input of 86L/minute circulating water, for a total average heat exchange volume of 82.9kW/h. The actual heat exchange volume delivered on the load side averages 112.0kW/h in our analysis. The average COP determined by analysis of the geothermal system's heating efficiency is 3.92. Aa a result of the tradeoff between the outside temperature and the inside temperature of the production facility and comparing the facility design with a combined well and open-closed loops geothermal(CWG) system, we determine that the 30RT-volume CWG system temperature are lower by 3.4°C, 6.8°C, 10.1°C and 13.4°C for ouside temperature is of 20°C, 25°C, 30°C and 35°C, respectively. Based on these results, a summer cooling effect of about 10°C is expected relative to a facility without a CWG system as the outside temperature is generally ≥30°C. Our results suggest that a complex geothermal system provides improvement under a variety of conditions even when heating conditions in winter are considered. Thus It is expected that the heating-cooling tradeoffs of complex geothermal system are improved by using water screen.

Keywords
geothermal
groundwater
open loop
closed loop
CWG system
complex geothermal system

본 연구에서는 지하수 관정을 활용하고 밀폐형-개방형이 결합된 복합지열시스템(CWG 시스템)을 시설재배지에 적용하여 열원측 및 부하측의 열교환량과 투입된 전력량 대비 효율을 평가하였다. 또한, 운전 과정에서의 외기온도 및 시설재배지 온도를 평가하여 복합지열시스템 적용 시의 냉난방 효과를 분석하였다. 냉방운전시 열원측 열교환량 평가결과, 약 235 L/min의 지하수가 유입되는 개방형에서 평균 90.0 kW/h, 약 85 L/min의 순환수가 유동하는 밀폐형에서 40.1 kW/h의 열교환량이 발생하였으며, 전체 열교환량은 평균 130.1 kW/h로 분석되었다. 부하측에서 실질적으로 전달되는 열교환량은 평균 110.4kW/h로 평가되었다. 복합지열시스템의 냉방효율을 분석한 결과, 평균 EER는 5.63으로 분석되었다. 난방운전 시 열원측 열교환량 평가결과, 약 266 L/min의 지하수가 유입되는 개방형에서 평균 60.4 kW/h, 약 86 L/min의 순환수가 유동하는 밀폐형에서 22.4 kW/h의 열교환량이 발생하였으며, 전체 열교환량은 평균 82.9 kW/h로 분석되었다. 부하측에서 실질적으로 전달되는 열교환량은 평균 112.0 kW/h로 평가되었다. 복합지열시스템의 난방효율을 분석한 결과, 평균 COP는 3.92로 분석되었다. 외기온도와 CWG 시스템을 적용한 시설하우스 및 비교 시설하우스 내부온도와의 상관관계를 분석한 결과 30RT 용량의 CWG 시스템 하우스가 비교 하우스에 비해 외기온도 20°C인 경우 3.4°C, 외기온도 25°C인 경우 6.8°C, 외기온도 30°C인 경우 10.1°C, 외기온도 35°C인 경우 13.4°C의 온도가 저감되는 것으로 평가되었다. 이러한 결과를 볼 때, 본 시스템을 적용할 경우 일반적으로 외기온도가 30°C 이상을 보이는 여름철에 CWG 시스템을 적용하지 않은 시설재배지에 비해 약 10°C 이상의 냉방효과가 나타낼 수 있을 것으로 판단된다. 이와 같은 결과는 시설재배지의 복합지열시스템 설계에 활용될 수 있고, 다양한 조건에서의 시험성과와 종합하여 복합지열시스템의 냉난방 효과에 대한 보다 명확한 규명이 가능할 것으로 판단된다.

키워드
지열
지하수
밀폐형
개방형
CWG시스템
복합지열시스템
References
1
Geothermal Energy Education Center, 2010, Geothermal System Design, Geon Ki Won Book Publishing, 189-193.
2
Kim, Y., Park H., Han, H., 2009, Study on the utilization of renewable energy for agriculture, Korea Rural Economic Institute.
3
Korea National College of Agriculture and Fisheries, 2015, Chapter 3 Location Condition of the Garden, Retrieved from https://www.af.ac.kr/planweb/board/list.9is.
4
Park, Y., Song, J.Y., Lee, G.C., Kim, K.J., Mok, J.K., Park, Y.C., 2017. Performance Analysis of Ground Heat Exchanger in Combined Well and Open-Closed Loops Geothermal (CWG) System, Korean Society of Soil and Groundwater Environment, 22(5), 23-29.
5
Rural Development Administration, 2008, Horticulture Energy Saving Guidebook to overcome high oil prices, Rural Development Administration Agricultural Engineering Research Center.
6
Song, J.Y., Lee, G.C., Jeong, G.C., Park, N., 2018. Experimental Study on heat Exchange Efficiency of Combined Well & Open-Closed Loops Geothermal System, Architectural Institute of Korea, 34(5), 43-50.
Information
  • Publisher :Korean Society of Engineering Geology
  • Publisher(Ko) :대한지질공학회
  • Journal Title :The Journal of Engineering Geology
  • Journal Title(Ko) :지질공학
  • Volume : 28
  • No :3
  • Pages :475-488
  • Received Date : 2018-08-14
  • Revised Date : 2018-08-28
  • Accepted Date : 2018-09-04
  • DOI :https://doi.org/10.9720/kseg.2018.3.475
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