研究目的
To theoretically study and optimize the energy and exergy efficiencies of a solar greenhouse integrated with PV/T collectors and an earth-air heat exchanger, and to evaluate their heating/cooling potentials.
研究成果
The integration of EAHE significantly improves temperature stability in greenhouses, reducing fluctuations by 46% in summer and 58% in winter, while PV/Ts are primarily effective for electricity generation with minimal heating contribution. Optimization revealed that only the length of buried pipes has a distinct optimum value (around 38 m), and the model showed good agreement with experimental data, confirming its reliability for energy and exergy assessments in solar greenhouses.
研究不足
The study is theoretical and relies on validation with existing experimental data, which may not capture all real-world variations. The model assumes certain simplifications, such as ideal heat transfer and constant soil temperature, which could affect accuracy. Optimization results are specific to the climatic conditions and parameters considered, and may not be generalizable. The heating potential of PV/Ts was found to be negligible, limiting their application to electricity generation only.
1：Experimental Design and Method Selection:
The study involved theoretical modeling and validation against experimental data from literature. A comprehensive thermal model was developed for the greenhouse, PV/T collectors, and EAHE, incorporating energy and exergy analyses. Optimization was performed using MATLAB to maximize energy and exergy efficiencies.
2：Sample Selection and Data Sources:
The model was validated using experimental data from Nayak and Tiwari (2008), with design parameters such as greenhouse floor area of 24 m2, buried pipe length of 39 m, and PV area of 9.68 m2. Climatic data for summer and winter days were extracted from the same reference.
3：68 m2. Climatic data for summer and winter days were extracted from the same reference.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: The system included a greenhouse with a plastic cover, brick north wall, exhaust fans, polymer pipes for EAHE (length 39 m, diameter 0.6 m), PV/T collectors (area 6.5×1.62 m2, inclination 45°), blower (capacity 0.15 kW), and fans for air circulation. Materials involved solar cells, Tedlar, insulation, and plants.
4：6 m), PV/T collectors (area 5×62 m2, inclination 45°), blower (capacity 15 kW), and fans for air circulation. Materials involved solar cells, Tedlar, insulation, and plants.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The theoretical model calculated temperatures of greenhouse air, plants, solar cells, and Tedlar back surface based on energy balances. Validation was done by comparing simulated temperatures with experimental data. Optimization involved varying parameters like number of PV modules, air flow rates, pipe length, and plant mass to find maximum efficiencies.
5：Data Analysis Methods:
Root Mean Square Deviation (RMSD) and coefficient of correlation (r) were used for validation. Energy and exergy efficiencies were calculated using derived equations, and optimization was performed with constraints in MATLAB.
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