Analysis of coaxial borehole heat exchanger for geothermal heat and power
Bibliographic record
Abstract
Decarbonization of heat and electricity generation through geothermal energy is increasing, thanks to its universal availability and base load capacity. Although geothermal energy has several advantages compared to other renewable energy sources, more research is necessary to understand the fluid flow and heat transfer processes in diverse geological formations. These geological formations can be complex due to the variability of rock/soil properties, fluid presence, and fluid movement. Heat exchangers employed in such systems can reach thousands of meters, posing challenges for field-test experiments. In addition, mathematical modeling of such systems is a challenging task. This dissertation is based on two geothermal projects; one focused on power generation and the other on heating. Both projects employ either a coaxial borehole heat exchanger (a single coaxial borehole) or a system of coaxial borehole heat exchangers. For geothermal power, a field-test experiment is carried out in a high-temperature resource well with a thermal gradient of 0.4°C/m. Experimental results are analyzed and rock properties are measured. In addition, a numerical model is developed to replicate the 500-meter deep field-test experiment. The developed numerical model is validated with the experimental data and is used to understand the subsurface behavior of the geothermal reservoir. Additionally, the performance of the heat exchanger under the complex geological formation, accounting for the presence of subsurface fluid flow, is evaluated. For geothermal heating, a numerical model is developed to study the heat transfer characteristics of a solar-geothermal heating system. The developed numerical model solves the heat and mass transfer process in a rectangular array of 450 coaxial boreholes. It also accounts for energy generation in solar thermal collectors and thermal demand on buildings. The numerical model is used to study energy injection into boreholes, energy extraction from boreholes, thermal interactions between boreholes, thermal losses from the system, and the performance of the solar-geothermal heating system. The results showed that subsurface fluid flow has a significant impact on the energy output from geothermal systems. Solar-geothermal heating systems have good potential to decarbonize space and water heating applications in Canada.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".