Theoretical development and experimental validation of a thermal model comparing different greenhouse covering materials
Bibliographic record
Abstract
• Heat load of a gothic greenhouse could be simulated with a quasi-steady state model. • Energy efficiency in greenhouse depends on the covering material. • Heat for dehumidification represents a large part of the heating load. This study compared greenhouse covering materials for small to mid-scale greenhouse producers in cold regions. Small gothic greenhouses commonly use polyethylene, resulting in significant plastic waste due to the need for replacement every 3 to 5 years. To address this issue while minimizing heating loads, new covering materials with improved durability and energy efficiency created from recycled products (e.g., polymethyl methacrylate) are being developed. Potential energy savings should be assessed since their spectral and thermal properties may positively impact both solar gains and heat transfer. A comparison between conventional (e.g., polyethylene) and alternative covering materials (e.g., polycarbonate and polymethyl methacrylate) was then carried out through numerical modeling written in Python This model takes detailed parameters into account: crops, construction and covering materials, greenhouse configurations, and localization. It uses hourly weather data including temperature, humidity, atmospheric pressure, cloud cover, wind speed, and solar irradiance. The model calculates heat losses and gains through the roof, walls, perimeter, and ground, considering longwave and shortwave radiation, conduction, convection, infiltration, and energy sinks and sources induced by plant evapotranspiration or environmental control systems. Results indicated that the model effectively predicts the heating of a double polyethylene-covered greenhouse located in the province of Quebec, Canada. The simulation of the same greenhouse covered with a polymethyl methacrylate revealed that heat loads can be reduced by 8.5 %. The thermal analysis also showed that, heat used in ventilation for dehumidification could represent 29 % of all energy consumption. This study enlightens several ways to improve sustainability of the greenhouse industry regarding energy consumption and plastic waste.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 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 | 0.001 |
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".