Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
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Optimal Operation Methods of the Seasonal Solar Borehole Thermal Energy Storage System for Heating of a Greenhouse

온실난방을 위한 태양열 지중 계간축열시스템의 최적 운전 방안

  • Kim, Wonuk (Green Building Research Center, Department of Living and Built Environment Research, Korea Institute of Civil Engineering and Building Technology (KICT)) ;
  • Kim, Yong-Ki (Green Building Research Center, Department of Living and Built Environment Research, Korea Institute of Civil Engineering and Building Technology (KICT))
  • 김원욱 (한국건설기술연구원 국민생활연구본부 녹색건축연구센터) ;
  • 김용기 (한국건설기술연구원 국민생활연구본부 녹색건축연구센터)
  • Received : 2018.11.19
  • Accepted : 2019.01.04
  • Published : 2019.01.31
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Abstract

Solar energy is one of the most abundant renewable energy sources on Earth but there are restrictions on the use of solar thermal energy due to the time-discrepancy between the solar-rich season and heating demand. In Europe and Canada, a seasonal solar thermal energy storage (SSTES), which stores the abundant solar heat in the summer and uses the heat for the winter heating load, is used. Recently, SSTES has been introduced in Korea and empirical studies are actively underway. In this study, a $2,000m^2$ flat plate type solar collector and $20,000m^2$ of borehole thermal energy storage (BTES) were studied for a greenhouse in Hwaseong City, which has a heating load of 2,164 GJ/year. To predict the dynamic performance of the system over time, it was simulated using the TRNSYS 18 program, and the solar fraction of the system with the control conditions was investigated. As a result, the solar BTES system proposed in this study showed an average solar fraction of approximately 60% for 5 years when differential temperature control was applied to both collecting solar thermal energy and discharging BTES. The proposed system simplified the configuration and control method of the solar BTES system and secured its performance.

태양열은 지구에서 가장 풍부한 재생에너지 중의 하나이지만, 일반적으로 태양열이 풍부한 계절과 열부하가 큰 계절이 서로 달라 사용에 제한이 있다. 유럽과 캐나다에서는 하절기의 풍부한 태양열을 저장하고 그 열을 동절기 난방부하에 활용하여 에너지를 절감하는 태양열 계간축열시스템을 활용하고 있다. 최근 물탱크방식 및 지중축열방식의 태양열 계간축열시스템이 국내에 소개되어 실증연구가 활발히 진행 중이다. 본 연구에서는 연간 2,164 GJ의 난방부하를 가진 경기도 화성시의 유리온실 1개동에 $2,000m^2$의 평판형 태양열 집열기, $20,000m^2$의 지중 계간축열조를 사용하고 단기축열조를 사용하지 않는 보어홀 방식의 태양열 지중 계간축열시스템을 모델링하여, 운전제어조건에 따른 태양열 이용률을 평가하였다. 시간에 따른 태양열 지중 계간축열시스템의 동적성능예측을 위하여 TRNSYS 18 프로그램을 이용하여 시뮬레이션 하였다. 결과적으로 본 연구에서 제안한 태양열 지중 계간축열시스템은 태양열 집열과 지중 계간축열조 방열에 각각 차온 제어 하였을 때, 5년간 평균 약 60%의 태양열 이용률을 나타내었다. 본 연구에서 제안된 시스템은 태양열 지중 계간축열시스템의 구성과 제어방법을 단순화하고 성능을 확보하였다.

Keywords

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Fig. 1. TRNSYS model of the BTES system

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Fig. 2. Weather data in Suwon-Si, Korea, 2013 (a) Hourly outdoor air temperature (b) Hourly global horizontal radiation

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Fig. 3. Hourly heating use of the glass green house in 2013

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Fig. 4. Hourly heating use patterns of the glass green house and the apartment house

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Fig. 5. Simulation cases for parameter analysis

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Fig. 6. Contour plots of solar fraction in heating of 1st year with dTLOAD and dTSOLAR

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Fig. 7. Contour plots of solar fraction in heating of 2nd year with dTLOAD and dTSOLAR

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Fig. 8. Contour plots of solar fraction in heating of 3rd year with dTLOAD and dTSOLAR

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Fig. 9. Contour plots of solar fraction in heating of 4th year with dTLOAD and dTSOLAR

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Fig. 10. Contour plots of solar fraction in heating of 5th year with dTLOAD and dTSOLAR

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Fig. 11. Contour plots of average solar fraction in heating of 5 years with dTLOAD and dTSOLAR

Table 1. Specification of BTES

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Table 2. Operating modes of the solar BTES system

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