Hybrid thermal seasonal storage and solar assisted geothermal heat pump systems for greenhouses

Ataei, Abtin;Hemmatabady, Hoofar;Nobakht, Seyed Yahya

  • Received : 2015.09.29
  • Accepted : 2016.02.05
  • Published : 2016.03.25


In this research, optimum design of the combined solar collector, geothermal heat pump and thermal seasonal storage system for heating and cooling a sample greenhouse is studied. In order to optimize the system from technical point of view some new control strategies and functions resulting from important TRNSYS output diagrams are presented. Temperatures of ground, rock bed storage, outlet ground heat exchanger fluid and entering fluid to the evaporator specify our strategies. Optimal heat storage is done with maximum efficiency and minimum loss. Mean seasonal heating and cooling COPs of 4.92 and 7.14 are achieved in series mode as there is no need to start the heat pump sometimes. Furthermore, optimal parallel operation of the storage and the heat pump is studied by applying the same control strategies. Although the aforementioned system has higher mean seasonal heating and cooling COPs (4.96 and 7.18 respectively) and lower initial cost, it requires higher amounts of auxiliary energy either. Soil temperature around ground heat exchanger will also increase up to $1.5^{\circ}C$ after 2 years of operation as a result of seasonal storage. At the end, the optimum combined system is chosen by trade-off between technical and economic issues.


heating COP;cooling COP;thermal storage;TRNSYS;heat pump;control strategies;parallel;series


  1. Banks, D. (2012), An Introduction to Thermogeology: Ground Source Heating and Cooling, John Wiley & Sons, USA
  2. Benli, H. (2011), "Energetic performance analysis of a ground-source heat pump system with latent heat storage for a greenhouse heating", Energy Convers. Manage., 52(1), 581-589.
  3. Dincer, I. and Rosen, M. (2002), Thermal Energy Storage: Systems and Applications, John Wiley & Sons, USA.
  4. Girard, A., Gago, E.J., Muneer, T. and Caceres, G. (2015), "Higher ground source heat pump COP in a residential building through the use of solar thermal collectors", Renew. Energy, 80, 26-39.
  5. Hellstrom, G. (1989), Duct Ground Heat Storage Model, Manual for Computer Code, University of Lund, Sweden.
  6. Hesaraki, A., Holmberg, S. and Haghighat, F. (2015), "Seasonal thermal energy storage with heat pumps and low temperatures in building projects-A comparative review", Renew. Sustain. Energy Rev., 43, 1199-1213.
  7. Hughes, P., Klein, S. and Close, D. (1976), "Packed bed thermal storage models for solar air heating and cooling systems", J. Heat Transf., 98(2), 336-338.
  8. Kavanaugh, S.P. and Rafferty, K.D. (1997), "Ground-source heat pumps: design of geothermal systems for commercial and institutional buildings", American Society of Heating, Refrigerating and Air-Conditioning Engineers.
  9. Kalogirou, S.A. (2013), Solar Energy Engineering: Processes and Systems, Academic Press, USA.
  10. Kusuda, T. and Achenbach, P.R. (1965), "Earth temperature and thermal diffusivity at selected stations in the United States", DTIC Document, National Standards Gaithersburg Bureau of MD.
  11. Marx, R., Bauer, D. and Drueck, H. (2014), "Energy efficient integration of heat pumps into solar district heating systems with seasonal thermal energy storage", Energy Procedia, 57, 2706-21715.
  12. McKinney, D. and Savitsky, A. (2003), Basic Optimization Models for Water and Energy Management, The University of Texas at Austin, USA.
  13. Mehrpooya, M., Hemmatabady, H. and Ahmadi, M.H. (2015), "Optimization of performance of combined solar collector-geothermal heat pump systems to supply thermal load needed for heating greenhouses", Energy Convers. Manage., 97, 382-392.
  14. Novo, A.V., Bayon, J.R., Castro-Fresno, D. and Rodriguez-Hernandez., J. (2010), "Review of seasonal heat storage in large basins: Water tanks and gravel-water pits", Appl. Energy, 87(2), 390-397.
  15. Omer, A.M. (2008), "Ground-source heat pumps systems and applications", Renew. Sustain. Energy Rev., 12(2), 344-371.
  16. Ozgener, O. and Ozgener, L. (2015), "Modeling of driveway as a solar collector for improving efficiency of solar assisted geothermal heat pump system: a case study", Renew. Sustain. Energy Rev., 46, 210-217.
  17. Smith, P.R. (2011), "Planning and installing solar thermal systems", Arch. Sci. Rev., 54(11), 86-87.
  18. Thumann, A. and Mehta, D.P. (2001), Handbook of Energy Engineering, The Fairmont Press, Inc, USA.
  19. Terziotti, L., Sweet, M. and McLeskey, J. (2012), "Modeling seasonal solar thermal energy storage in a large urban residential building using TRNSYS 16", Energy Build., 45, 28-31.
  20. University of Wisconsin-Madison, Solar Energy Laboratory and Klein, S.A. (1979), TRNSYS, a transient system simulation program. Solar Energy Laborataory, University of Wisconsin-Madison, USA.
  21. Wang, H. and Qi, C. (2008), "Performance study of underground thermal storage in a solar-ground coupled heat pump system for residential buildings", Energy Build., 40(7), 1278-1286.
  22. Wang, X., Zheng, M., Zhang, W., Zhang, S. and Yang, T. (2010), "Experimental study of a solar-assisted ground-coupled heat pump system with solar seasonal thermal storage in severe cold areas", Energy Build., 42(11), 2104-2110.
  23. Yoon, S. and Lee, S.R. (2015), "Life cycle cost analysis and smart operation mode of ground source heat pump system", Smart Struct. Syst., 16(4), 743-758.
  24. Sayigh, A. (2012), Solar Energy Engineering, Elsevier, The Netherlands

Cited by

  1. Performance analysis of a soil-based thermal energy storage system using solar-driven air-source heat pump for Danish buildings sector vol.114, 2017,
  2. Impact of hybrid system in polyester production vol.4, pp.1, 2017,