Strategic optimization of borehole heat exchanger field for seasonal geothermal heating and cooling

Ground source heat pump (GSHP) systems are becoming popular in space heating and cooling applications. Despite this fact, in most countries, the role of this energy is not as important as it should be nowadays according to its capabilities for energy generation without CO2 emissions, mainly due to the lack of technical knowledge about GSHP performance. The analysis of the physical processes that take part in the geothermal exchanges is necessary to allow the optimal exploitation of the geothermal resources. For all the above, an experimental geothermal device was built in the laboratory to control the phenomena that take place in a borehole heat exchanger (BHE). A 1-m high single-U heat exchanger was inserted in the center of a polyethylene container which also included granular material (surrounding ground) and the grouting material. Temperature sensors were situated in different positions of the experimental setup. Physical processes are evaluated to finally validate the model. Numerous applications can be developed from the experimental BHE. In this research, the determination of the thermal conductivity of the material used as medium was carried out. Results of this parameter were also compared with the ones obtained from the use of the KD2 Pro device.

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Optimization of geothermal interaction of a double U-tube borehole heat exchanger for space heating and cooling applications using Taguchi method and utility concept

Geothermics ◽

10.1016/j.geothermics.2019.101723 ◽

2020 ◽

Vol 83 ◽

pp. 101723 ◽

Cited By ~ 7

Author(s):

Satish Kumar ◽

K. Murugesan

Keyword(s):

Heat Exchanger ◽

Taguchi Method ◽

Space Heating ◽

Borehole Heat Exchanger ◽

Utility Concept ◽

Heating And Cooling

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Measurements and Design Calculations for a Deep Coaxial Borehole Heat Exchanger in Aachen, Germany

International Journal of Geophysics ◽

10.1155/2013/916541 ◽

2013 ◽

Vol 2013 ◽

pp. 1-14 ◽

Cited By ~ 19

Author(s):

Lydia Dijkshoorn ◽

Simon Speer ◽

Renate Pechnig

Keyword(s):

Heat Exchanger ◽

Maximum Temperature ◽

Deep Borehole ◽

Borehole Heat Exchanger ◽

Heating And Cooling ◽

Climatic Control ◽

Short Period ◽

Design Calculations ◽

The University ◽

The City

This study aims at evaluating the feasibility of an installation for space heating and cooling the building of the university in the center of the city Aachen, Germany, with a 2500 m deep coaxial borehole heat exchanger (BHE). Direct heating the building in winter requires temperatures of 40°C. In summer, cooling the university building uses a climatic control adsorption unit, which requires a temperature of minimum 55°C. The drilled rocks of the 2500 m deep borehole have extremely low permeabilities and porosities less than 1%. Their thermal conductivity varies between 2.2 W/(m·K) and 8.9 W/(m·K). The high values are related to the quartzite sandstones. The maximum temperature in the borehole is 85°C at 2500 m depth, which corresponds to a mean specific heat flow of 85 mW/m2–90 mW/m2. Results indicate that for a short period, the borehole may deliver the required temperature. But after a 20-year period of operation, temperatures are too low to drive the adsorption unit for cooling. In winter, however, the borehole heat exchanger may still supply the building with sufficient heat, with temperatures varying between 25 and 55°C and a circulation flow rate of 10 m3/h at maximum.

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Design and Development of an Additively Manufactured Geothermal Heat Exchanger for Improved Efficiency and Easy Installation

Volume 2B: Advanced Manufacturing ◽

10.1115/imece2020-23288 ◽

2020 ◽

Author(s):

Takele Gemeda ◽

Sandy Estrada ◽

Wondwosen Demisse ◽

Lei Wang ◽

Jiajun Xu

Keyword(s):

Additive Manufacturing ◽

Heat Exchanger ◽

Constant Temperature ◽

Energy Systems ◽

The United States ◽

Geothermal System ◽

Geothermal Systems ◽

Geothermal Heating ◽

Heating And Cooling ◽

System Energy

Abstract Effective system energy management and cooling is critical for a range of increasingly complex systems and missions. Various industries and agencies seek technologies to use energy more efficiently in various applications, and thereby increase system energy efficiencies in future advanced energy systems. There has been an increasing interest in exploiting the use of additive manufacturing in developing nontraditional energy conversion schemes. Meanwhile, wind power and solar power systems have become part of common knowledge and conversation over the past few years. While these provide excellent sustainable options of energy production, geothermal energy systems are just as efficient and economical. Solar and wind energy collectors are also site specific. On the other hand, the geothermal systems do not take up buildable ground level space nor are they location or climate specific. The earth has a generally constant temperature throughout the year which can be used in geothermal systems to benefit all sites. If all geothermal resources were combined, enough energy would be produced to provide all of the electricity needs in the United States. However, conventional geothermal system requires the relatively complex installation process and can potentially be cost prohibitive to many potential users. In this study, an additively manufactured heat exchanger was designed and developed to resolve that issue. The heat exchanger can be integrated with a conventional geothermal heating and cooling system for improved efficiency and easy installation. A customized geothermal heating and cooling loop was designed and developed for testing the efficiency of the heat exchanger. Within this proposed system, this additive manufactured heat exchanger is designed and fabricated to improve it efficiency and easy installation with minimal tools needed. This new design eliminates the need of excavation of the soil and installation of long tubes as conventionally required for geothermal system. This new heat exchanger was designed using CREO software and fabricated using an EOS M280 direct metal laser sintering system at University of the District of Columbia. It is then integrated with a heat pump to exchange heat between a constant temperature of water bath circulator and a water heat sink. A prototype system was designed and constructed, which allowed the direct assessment of its performance. The performance of the heat exchanger is studied using COMSOL software to assess its heat transfer performance. The results have shown a significant improvement in its efficiency. It has shown the promising application of metal additive manufacturing technique in improving the efficiency of existing energy harvesting applications.

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