Mock-up experimental study on the performance of a combined cooling-domestic hot water-ground source heat pump system

Abstract

A ground source heat pump (GSHP) delivers heat from a condenser to the ground when it operates with cooling mode. However, the ground temperature increases when the GSHP system operates for a long time. The increased ground temperature can deteriorate the GSHP’s coefficient of performance (COP). To maintain the balance between the ground temperature and COP, the condensation heat from the cooling GSHP can be used for other heating systems before it is transferred to the ground. This study proposes a combined GSHP system connecting a three RT cooling GSHP with a 1.5 RT domestic hot water (DHW) heat pump, and the performance of the system was evaluated through mock-up experiments. In the combined GSHP system, the condensation heat of the cooling system was used as the heat source of the DHW system. Therefore, the ground temperature could be reduced, and the performances of both the GSHP cooler and DHW heater pump could be enhanced. Mock-up experiments for performance evaluation were conducted with cooling-only, DHW-only, and cooling-DHW operational modes. The results showed that cooling-DHW operation slowed down the change in heat source temperature. In comparison with those of the cooling-only and DWH-only heat pumps, the COPs of the cooling heat pump and DHW heat pump of the combined system were increased by 12.93% and 15.47%, respectively. Moreover, the total COP of the cooling-DHW combined GSHP system increased by 4.4% and 29.55% in comparison with those of the cooling-only GSHP and DHW-only GSHP systems, respectively.

Practical application

A combined GSHP system was proposed by connecting a GSHP for space cooling with a heat pump for DHW to mitigate the ground temperature changes due to the long-term operation of the GSHP system. The combined system reuses the condensation heat generated by the cooling heat pump as the heat source of the DHW heat pump for ensuring the system performance and building energy saving. Therefore, this system is suitable for buildings with large energy use and heavy hot water demand, especially in summer, such as hospital and hotel buildings.

Keywords

Ground source heat pump domestic hot water system fan coil unit heat compensation unit

Get full access to this article

View all access options for this article.

References

Bai

Zhang

, et al. Research on the design and application of capillary heat exchangers for heat pumps in coastal areas. Build Serv Eng Res Technol 2021; 42(3): 333–348.

Kummert

Bernier

. Sub-hourly simulation of residential ground coupled heat pump systems. Build Serv Eng Res Technol 2008; 29(1): 27–44.

Sarbu

Sebarchievici

. General review of ground-source heat pump systems for heating and cooling of buildings. Energy Build 2014; 70: 441–454.

Bertsch

Groll

. Two-stage air-source heat pump for residential heating and cooling applications in northern U.S. climates. Int J Refrig 2008; 31(7): 1282–1292.

Hakkaki-Fard

Aidoun

Ouzzane

. Applying refrigerant mixtures with thermal glide in cold climate air-source heat pumps. Appl Therm Eng 2014; 62(2): 714–722.

Pérez-Lombard

Ortiz

Pout

. A review on buildings energy consumption information. Energy Build 2008; 40: 394–397.

Wang

, et al. An integrated predictive model of the long-term performance of ground source heat pump (GSHP) systems. Energy Build 2008; 159: 309–318.

Underwood

Spitler

. Analysis of vertical ground loop heat exchangers applied to buildings in the UK. Build Serv Eng Res Technol 2007; 28(2): 133–159.

You

Yang

. Feasibility of ground source heat pump using spiral coil energy piles with seepage for hotels in cold regions. Energy Convers Manage 2020; 205: 112466.

10.

İnallı

Esen

. Experimental thermal performance evaluation of a horizontal ground-source heat pump system. Appl Therm Eng 2004; 24: 2219–2232.

11.

Tarnawski

Leong

Momose

, et al. Analysis of ground source heat pumps with horizontal ground heat exchangers for northern Japan. Renew Energy 2009; 34(1): 127–134.

12.

Benli

. A performance comparison between a horizontal source and a vertical source heat pump system for a green house heating in the mild climate Elazig, Turkey. Appl Therm Eng 2013; 50(1): 197–206.

13.

Hou

Taherian

. A predictive TRNSYS model for long-term operation of a hybrid ground source heat pump system with innovative horizontal buried pipe type. Renew Energy 2020; 151: 1045–1054.

14.

Zhang

, et al. Structure optimization design of ground heat exchanger by topology method to mitigate the geothermal imbalance. Appl Therm Eng 2020; 170: 115023.

15.

Choi

Ooka

Nam

. Impact of long-term operation of ground-source heat pump on subsurface thermal state in urban areas. Sustain Cities Soc 2018; 38: 429–438.

16.

Dong

Wang

, et al. Long term coupled simulation for ground source heat pump and underground heat exchangers. Energy Build 2015; 106: 13–22.

17.

Zeng

Zhang

Deng

, et al. Optimization and performance comparison of combined cooling, heating and power/ground source heat pump/photovoltaic/solar thermal system under different load ratio for two operation strategies. Energy Convers Manage 2020; 208: 112579.

18.

Lee

Lam

. Application of variable-speed ground-source heat pumps to displacement ventilation systems for use in sub-tropical regions. Build Serv Eng Res Technol 2014; 35(6): 671–681.

19.

Bina

Fuji

Tsuya

, et al. Comparative study of hybrid ground source heat pump in cooling and heating dominant climates. Energy Convers Manage 2022; 252: 115122.

20.

Zhang

, et al. Hybrid ground source heat pump system for overcoming soil thermal imbalance: a review. Sustain Energy Technol Assess 2021; 44: 101098.

21.

Ozgener

Hepbasli

. Exergoeconomic analysis of a solar assisted ground-source heat pump greenhouse heating system. Appl Therm Eng 2005; 25(10): 1459–1471.

22.

Rad

Fung

Leong

. Feasibility of combined solar thermal and ground source heat pump systems in cold climate Canada. Energy Build 2013; 61: 224–232.

23.

Kim

Choi

Cho

. Performance analysis of hybrid solar-geothermal CO₂ heat pump system for residential heating. Renew Energy 2013; 50: 596–604.

24.

Baek

Jeong

Yoon

, et al. The development and performance analysis of compact type solar thermal/ground coupled heat pump hybrid system for heating cooling and hot water. J Korean Sol Energy Soc 2012; 32: 59–67.

25.

Wang

Fung

, et al. Performance prediction of a hybrid solar ground-source heat pump system. Energy Build 2012; 47: 600–611.

26.

Nam

Gao

Yoon

, et al. Study on the of a ground source heat pump system assisted by solar thermal storage. Energies 2015; 8(12): 13378–13394.

27.

Weeratunge

Aditya

Dunstall

, et al. Feasibility and performance analysis of hybrid ground source heat pump systems in fourteen cities. Energy 2021; 234: 121254.

28.

Biglarian

Saidi

Abbaspour

. Economic and environmental assessment of a solar-assisted ground source heat pump system in a heating-dominated climate. Int J Environ Sci Technol 2019; 15: 3091–3098.

29.

Sakellariou

Axaopoulos

Wright

. Energy and economic evaluation of a solar assisted ground source heat pump system for a north Mediterranean city. Energy Build 2021; 231: 110640.

30.

Liu

, et al. Performance and feasibility study of hybrid ground source heat pump system assisted with cooling tower for one office building based on one Shanghai case. Energy 2019; 173: 28–37.

31.

Park

Lee

Kim

, et al. Performance optimization of a hybrid ground source heat pump with the parallel configuration of a ground heat exchanger and a supplemental heat rejecter in the cooling mode. Int J Refrig 2012; 35(6): 1537–1546.

32.

You

Shi

Wang

, et al. A new ground-coupled heat pump system integrated with a multi-mode air-source heat compensator to eliminate thermal imbalance in cold regions. Energy Build 2015; 107: 103–112.

33.

You

Wang

, et al. Performance analysis of hybrid ground-coupled heat pump system with multi-function. Energy Convers Manag 2015; 92: 47–59.

34.

Zhang

. Integrated optimization study of hot water supply system with multi-heat-source for the public bath based on PVT heat pump and water source heat pump. Appl Therm Eng 2020; 176: 115146.

35.

Choi

Kim

Son

, et al. Experimental study on the performance of heat pump water heating system coupled with air type PV/T collector. Appl Therm Eng 2020; 178: 115427.

36.

Son

. Performance analysis of a R744 and R404A cascade refrigeration system with internal heat exchanger. J Korean Soc Power Syst Eng 2012; 16: 38–43.

37.

Jang

Choi

. Study on the performance of a cascade heat pump with two-stage water heating process. Soc Geother Energy Eng Korea 2016; 12(4): 27–32.

38.

Yrjölä

Laaksonen

. Domestic hot water production with ground source heat pump in apartment buildings. Energies 2015; 8(8): 8447–8466.

39.

. Energy demand for hot water supply for indoor environments: problems and perspectives. Indoor Built Environ 2014; 24(1): 5–10.

40.

Zhang

Gudmundsson

Thorsen

, et al. Optimization of China’s centralized domestic hot water system by applying danish elements. Energy Procedia 2014; 51: 2833–2840.

41.

Pomianowski

Johra

Marszal-Pomianowska

, et al. Sustainable and energy-efficient domestic hot water systems: a review. Renew Sust Energ Rev 2020; 128: 109900.

42.

Kim

Yim

Lee

. Analytical study on changes in domestic hot water use caused by COVID-19 pandemic. Energy 2021; 231: 120915.

43.

Fuentes

Arce

Salom

. A review of domestic hot water consumption profiles for application in system and buildings energy performance analysis. Renew Sust Energ Rev 2018; 81: 1530–1547.

44.

Park

Chung

. Building load models for hotels in Korea. J Korean Solar Energy Soc 2009; 29: 48–57.

45.

Park

Chung

. Comparison of energy demand characteristics for hotel, hospital, and office buildings in Korea. Korean J Air Cond Refrig Eng 2009; 21: 553–558.

46.

Park

. Geothermal energy. In: Facility engineering handbook. 4th ed. Seoul: Society of Air-Conditioning and Refrigerating Engineers of Korea, 2018, Volume 3, 4.231.

47.

National Geography Information Institute . The National Atlas of Korea II 2020. https://nationalatlas.ngii.go.kr/pages/page_2302.php (2020, accessed 18 October 2022).