研究目的
To develop a solid compound parabolic concentrator (CPC) cover for greenhouses to convert excess light into heat, improving light regulation and thermal environment for plant growth.
研究成果
The solid CPC cover effectively regulates light transmittance, reducing it at noon and increasing it during morning and afternoon, leading to more uniform illumination and improved thermal environment in greenhouses. It achieves a maximum instantaneous thermal efficiency of 32.2% and thermal power of 353 W/m2, demonstrating potential for comprehensive solar energy utilization in agricultural applications.
研究不足
The study is limited by the use of only one cover plate due to high processing costs, which restricts the scale of energy collection. The simulation assumes only direct sunlight, whereas real weather includes scattered light, leading to discrepancies. The system's performance may vary with geographic location and seasonal changes.
1：Experimental Design and Method Selection:
The study involved optical simulations using TracePro software to track sunlight at different incident angles and experimental tests under real weather conditions to measure transmittance and heating power. The solid CPC was designed with specific geometric parameters and integrated with a heat pipe system for thermal energy collection.
2：Sample Selection and Data Sources:
The solid CPC covers were machined from polymethyl methacrylate (PMMA) and tested outdoors in Beijing, China. Data on solar irradiance, temperature, and light transmittance were collected using various instruments.
3：List of Experimental Equipment and Materials:
Equipment includes solarimeters, thermocouples, flow meters, anemometers, illuminometers, and a solar simulator. Materials include PMMA for the CPC, PVC soft glass, thermal insulation material, selective absorbing coating, and heat pipes.
4：Experimental Procedures and Operational Workflow:
The transmittance was tested using an optics integrating box, with illuminometers measuring indoor and outdoor light intensity. Thermal performance was evaluated by measuring water temperature changes in a heat storage tank connected to the heat pipe. Simulations were conducted for different times of the year to analyze light distribution.
5：Data Analysis Methods:
Data were analyzed using energy balance equations for the collector, with instantaneous efficiency calculated based on solar radiation and temperature differences. Statistical comparisons were made between simulation and experimental results.
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