Journal of the Korean Society for Geothermal and Hydrothermal Energy (한국지열·수열에너지학회논문집)

Korean Society for Geothermal and Hydrothermal Energy (한국지열·수열에너지학회)
권호 표지
DOI QR코드

DOI QR Code

Preliminary Analysis of Long-Term Performance of Borefield Connected to Hybrid Sources

하이브리드 열원이 연결된 보어필드 장기 성능의 기초적 분석

  • Young-Joon Park (Graduate School, Department of Architectural Engineering Inha University) ;
  • Eui-Jong Kim (Department of Architectural Engineering Inha University)
  • Received : 2024.05.21
  • Accepted : 2024.06.28
  • Published : 2024.09.01
Download PDF
⟨ Previous Next ⟩

Abstract

In this study, the performance of a ground heat exchanger (GHE) for domestic hot water loads was evaluated using an FLS (Finite Line Source) model with various configurations. The evaluation compared two scenarios: using the GHE alone and using a hybrid system combining the GHE with solar thermal modules, operated in both group and individual modes. The results indicated a continuous decrease in ground temperature when only the GHE was used. However, in the group/individual operation modes, the ground temperature showed a slight decrease but maintained a more stable level. Over a long-term operation of 20 years, the hybrid group/individual operation with solar thermal modules showed that the average temperature of the fluid discharged from the GHE was approximately 0.7℃ higher than when only the GHE was used. Providing a higher temperature fluid on the heat source side suggests the potential to improve the COP (Coefficient of Performance) of the heat pump. Moreover, the proposed hybrid group/individual operation mode demonstrated the ability to mitigate ground temperature imbalances caused by load imbalances, and confirmed the possibility of reducing the number of GHE installations by half, thereby lowering initial investment costs. In conclusion, the simulation verified that the group/individual operation mode utilizing hybrid heat sources is an effective alternative for enhancing the performance and cost-efficiency of ground source heat pump systems.

Keywords

References

  1. Nam, Y. J. and Chae, H. B., 2013, Prediction of the heat exchange rate for a horizontal ground heat pump system using a ground heat transfer simulation, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 25, No. 6, pp. 297-302. https://doi.org/10.6110/KJACR.2013.25.6.297
  2. Rybach, L. and Sanner, B., 2000, Ground source heat pump systems, The European Experience, Vol. 21, No. 1, pp. 16-26.
  3. Pambou, C. H. K., Raymond, J., Miranda, M. M., and Giordano, N., 2022, Estimation of in situ heat capacity and thermal diffusivity from undisturbed ground temperature profile measured in ground heat exchangers, Geosciences, Vol. 12, No. 5, pp. 180. https://doi.org/10.3390/geosciences12050180
  4. Sohn, B. H. and Choi, J. M., 2012, Performance prediction of geothermal heat pump (GHP) system with energy piles using simulation approach, Korean Journal of Air-Conditioning and Refrigeration Engineering, Vol. 24 No. 2, pp. 155-163. https://doi.org/10.6110/KJACR.2012.24.2.155
  5. Luo, J., Rohn, J., Bayer, M., Priess, A., Wilkmann, L., and Xiang, W., 2015, Heating and cooling performance analysis of a ground source heat pump system in southern germany, Geothermics, Vol. 53, pp. 57-66. https://doi.org/10.1016/j.geothermics.2014.04.004
  6. Yavuzturk, C. and Spitler, J. D., 2000, Comparative study of operating and control strategies for hybrid ground source heat pump systems using a short time step simulation model, Ashrae Transactions, Vol. 106, pp. 192.
  7. Xu, L., Pu, L., Zhang, S., and Li, Y., 2021, Hybrid ground source heat pump system for overcoming soil thermal imbalance : A review, Sustainable Energy Technologies and Assessments, Vol. 44, pp. 101098. https://doi.org/10.1016/j.seta.2021.101098
  8. Bae, S.M., 2022, Performance prediction method of integrated system using photovoltaic-thermal and ground source heat pump, Ph. D. Thesis, Pusan University.
  9. Park, S.H., 2023, Design and operating strategy of a Novel hybrid ground source heat pump system, Ph. D. Thesis, Inha University.
  10. Baek, S. H., Yeo, M. S., and Kim, K. W., 2017, Effects of the geothermal load on the ground temperature recovery in a ground heat exchanger, Energy and buildings, Vol. 136, pp. 63-72. https://doi.org/10.1016/j.enbuild.2016.11.056
  11. Bae, S. M. and Nam, Y. J., 2022, Economic and environmental analysis of ground source heat pump system according to operation methods, Geothermics, Vol. 101, pp. 102373. https://doi.org/10.1016/j.geothermics.2022.102373
  12. Bayer, P., de Paly, M., and Beck, M., 2014, Strategic optimization of borehole heat exchanger field for seasonal geothermal heating and cooling, Applied Energy, Vol. 136, pp. 445-453. https://doi.org/10.1016/j.apenergy.2014.09.029
  13. Yu, M., Zhang, K., Cao, X., Hu, A., Cui, P., and Fang, Z., 2016, Zoning operation of multiple borehole ground heat exchangers to alleviate the ground thermal accumulation caused by unbalanced seasonal loads. Energy and Buildings, Vol. 110, pp. 345-352. https://doi.org/10.1016/j.enbuild.2015.11.022
  14. Zeng, H. Y., Diao, N. R., and Fang, Z. H., 2002, A finite line source model for boreholes in geothermal heat exchangers, Heat Transfer-Asian Research : Cosponsored by the Society of Chemical Engineers of Japan and the Heat Transfer Division of ASME, Vol. 31, No. 7. pp. 558-567. https://doi.org/10.1002/htj.10057
  15. Lamarche, L. and Beauchamp, B., 2007, A new contribution to the finite line-source model for geothermal boreholes. Energy and Buildings, Vol. 39, No. 2, pp. 188-198. https://doi.org/10.1016/j.enbuild.2006.06.003
  16. Hellstrom, G., 1989, Ground heat storage: thermal analyses of duct storage systems, Ph. D. Thesis, Lund University.
  17. TRNSYS17, TESS Libs 17-Electrical Library Mathematical Reference, Vol. 03, pp. 38-41.
  18. Bernier, M. A., 2001, Ground-coupled heat pump system simulation/Diseussion, ASHRAE transactions, Vol. 107, pp. 605.
  19. Remund, C. P., 1999, Borehole thermal resistance: laboratory and field studies, ASHRAE transactions, Vol. 105, pp. 439.
  20. Kim, E. J., 2018, TRNSYS g-function generator using a simple boundary condition, Energy and Buildings, Vol. 172, pp. 192-200. https://doi.org/10.1016/j.enbuild.2018.05.014
  21. Yavuzturk, C. and Spitler, J. D., 1999, A short time step response factor model for vertical ground loop heat exchangers, ASHRAE transactions, Vol. 105, No. 2, pp. 475-485.
  22. Fossa, M. and Paietta, E., 2013, Comparison of multiple load aggregation algorithms for annual hourly simulations of geothermal heat pumps, In European Geothermal Congress
  23. ISO 18523-1: 2016, Energy performance of buildings--Schedule and condition of building, zone and space usage for energy calculation-Part 1: Non-residential buildings.