A Pilot Study on Geothermal Heat Pump (GHP) Use for Cooling Operations, and on GHP Site Selection in Tropical Regions Based on a Case Study in Thailand
Abstract
:1. Introduction
2. Materials and Methods
2.1. Geology and Underground Temperature of Bangkok Area
- -
- The 1st layer has a thickness of up to 20 m and consists mainly of clay with high plasticity and homogeneity.
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- The 2nd layer has an average thickness of 6 m and consists principally of pale brown to yellowish brown sandy clay. It is composed of 60% clay with moderate plasticity and heterogeneity and 40% sand with fine to medium grain sizes, relatively poorly sorted grains, and sub-angular shapes. Mineralogically, it is comprised essentially of quartz with subordinate feldspar and rock fragments.
- -
- The 3rd layer has an average thickness of 15 m and consists of pale brown sand with fine to medium grain sizes, good sorted grains, and sub-angular shapes. It is mostly composed of quartz with subordinate feldspar, rock fragments, and clay minerals.
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- The 4th layer has an average thickness of 9 m and comprises yellowish brown clay with moderate plasticity and a heterogeneous mixture of medium sand and silt.
2.2. System Setting for GHP Experiment
3. Results
3.1. Stratigraphy of Wells for System Setting
3.2. Operation and Data Acquisition
3.3. Electricity Consumption
4. Discussion
4.1. Comparisons between Subsurface Temperatures and Outside Air Temperatures
4.2. Suitable Depth for Heat Exchange Wells
4.3. Factors of Energy Saving
4.3.1. Outside Air Temperatures
4.3.2. Humidity
4.4. Coefficient of Performance (COP)
4.5. Interpretation of the Results and Importance of This Study
5. Conclusions
- (1)
- The suitable depth of GHP piping should be lower than that of the water table (25 to 50 m in eastern Bangkok, 30 to 50 m in the western part of Bangkok, and 25 to 30 m in central Bangkok). However, for the actual site selection other factors must be considered.
- (2)
- The underground temperatures of Bangkok area range between 29 to 31 °C at the depth of 0 to 50 m. These temperatures are 1 to 1.5 °C different depending on the location. Our GHP experiment indicates good electricity saving even when the site is located on a relatively high underground temperature area.
- (3)
- A comparison was made between the GHP and the normal air conditioner (AC) in the same room with similar specifications, and it was found that the electricity consumption was reduced by about 30% when using of the GHP system.
- (4)
- The electricity consumption showed clear a relation to the atmospheric temperature, namely, high electric consumption was recorded in high-temperature days and vice versa. The COP was in the range between 6.7 and 2.3 with an average of 4.38 showed also the same tendency. For humidity, we could not directly show relation with the power consumption of the cooling system.
- (5)
- The inlet and outlet temperature was 34.2 °C and 36.0 °C in April 2015. Even with such high temperatures of the circulating cooling water, the energy saving was very good. It is further recommended that the horizontal-loop GHP system should be compared with the vertical-loop system.
- (6)
- In economic point of view, the installation cost of GHP system was higher than normal air conditioner. There was an advantage of GHP system after operating for 14 years [35].
- (7)
- In the future research, it would be interesting to perform a building model validation for precise prediction of energy saving in building [36].
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Date | Time | Subsurface Temperature (°C) | |||
---|---|---|---|---|---|
8 m | 10 m | 25 m | 50 m | ||
15 May 2014 | 10.00 a.m. | 29.6 | 29.6 | 30.0 | 30.5 |
27 May 2014 | 10.00 a.m | 29.7 | 29.8 | 29.9 | 30.7 |
4 June 2014 | 10.36 a.m. | 29.7 | 29.7 | 29.8 | 30.7 |
10 June 2014 | 10.05 a.m. | 29.8 | 29.7 | 29.9 | 30.7 |
19 June 2014 | 10.00 a.m. | 29.7 | 29.8 | 30.0 | 30.7 |
24 June 2014 | 10.00 a.m. | 29.8 | 29.8 | 30.0 | 30.7 |
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Chokchai, S.; Chotpantarat, S.; Takashima, I.; Uchida, Y.; Widiatmojo, A.; Yasukawa, K.; Charusiri, P. A Pilot Study on Geothermal Heat Pump (GHP) Use for Cooling Operations, and on GHP Site Selection in Tropical Regions Based on a Case Study in Thailand. Energies 2018, 11, 2356. https://doi.org/10.3390/en11092356
Chokchai S, Chotpantarat S, Takashima I, Uchida Y, Widiatmojo A, Yasukawa K, Charusiri P. A Pilot Study on Geothermal Heat Pump (GHP) Use for Cooling Operations, and on GHP Site Selection in Tropical Regions Based on a Case Study in Thailand. Energies. 2018; 11(9):2356. https://doi.org/10.3390/en11092356
Chicago/Turabian StyleChokchai, Sasimook, Srilert Chotpantarat, Isao Takashima, Youhei Uchida, Arif Widiatmojo, Kasumi Yasukawa, and Punya Charusiri. 2018. "A Pilot Study on Geothermal Heat Pump (GHP) Use for Cooling Operations, and on GHP Site Selection in Tropical Regions Based on a Case Study in Thailand" Energies 11, no. 9: 2356. https://doi.org/10.3390/en11092356