DESIGN, THERMAL SIMULATION AND ECONOMIC FEASIBILITY ANALYSIS OF A PLANT FACTORY HOUSED IN A UNDERGROUND MINE DRIFT
Bibliographic record
Abstract
For the growing population all over the world it is necessary to produce sufficient food where controlled environment agriculture would be a potential solution but restricted due to energy intensiveness. Producing vegetables in underground mine tunnels in the underground plant factory (UGPF) could reduce energy consumption of plant factories as it is not affected by surface weather. This study developed a numerical heat transfer model to simulate heat transfer through the surrounding rock envelope using ANSYS Fluent software and the results are used in the thermal simulation to predict heating, ventilation and air conditioning (HVAC) energy load as well as electricity consumption of an UGPF in OpenStudio energy simulation software. A 550 m2 floor UGPF is designed considering the metal mine (Cu, Zn and Au) which is in Flin Flon, Manitoba, Canada (54°46′0″N latitude and 101°52′40″W longitude) in a 100 m tunnel to produce lettuce in 9 tiers, a total cultivation area of 4306.5 m2 with base case of 30℃/24℃ in light/dark period temperature. At the beginning (first day) of operation the UGPF can reduce 0.0748 kW/m2 (kW per unit surface area of rock envelope) of cooling load in light period but after 3 years it is reduced to 0.0195 kW/m2 which is 26.1% of initial value. According to the sensitivity analysis after 3 years of operation, virgin rock temperature of 278 and 298 K will results in heat transfer rate (HTR) increasing by 26.7% and decreasing by 62.5% as compared to the base case (284 K), respectively, indoor air temperature from 293/287 K to 303/297 K (light/dark) will result in 80.8% increasing of HTR, and rock thermal conductivity 1.5 and 3.5 W/m.K will results in HTR decreasing by 26.9% and increasing by 10.7% as compared to the base case, correspondingly. Due to the higher HTR, at the beginning of operation the UGPF can reduce 28.3% of HVAC energy load and gradually decrease it to 8.9% after 3 years of operation as compared to the surface plant factory. Passive ventilation (PV) strategies are used to further reduce the HVAC energy consumption of the UGPF. In Canadian prairies, the cold and dry air is used to remove sensible and latent loads by fan ventilation; heat recovery (HR) was used to pre-heat the fresh air. The additional sensible load is satisfied by the chiller and boiler, the lower relative humidity setpoint is maintained by a humidifier. HVAC control strategies are developed to maximize the passive cooling and dehumidification using PV according to ambient temperature and balance points are calculated (-17.12℃ and 18.97℃ temperature for winter and summer season). Implementing these control strategies of PV and HR results in 74.5% reduction of HVAC electricity consumption as compared to the base case. The PV and HR contributions to chiller and boiler electricity consumption savings by 95.9% and 63%, respectively. Finally, the net present value, internal rate of return, profitability index and simple payback period showed that the project is economically feasible. The simple payback period is 6.7 years.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".