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Photothermal/day lighting performance analysis of a multifunctional solid compound parabolic concentrator for an active solar greenhouse roof
摘要： Currently, the excess light above a light saturation point cannot be harnessed for plant growth in conventional greenhouse covers. In this study, we developed a solid compound parabolic concentrator (CPC) cover for use in greenhouses to convert excess light into heat. Optical simulation software was used to track the sunlight at different incident angles over time. We also conducted experiments to determine the transmittance and heating power of the solid CPC coating under real weather conditions. The maximum instantaneous thermal efficiency and thermal energy of a single solid CPC cover plate were 32.2% and 353 W/m2, respectively. The simulation results were in good agreement with the experimental output power and the trend of the actual transmittance of the covering material. The transmittance of the covering material was low when the midday sun was intense, and the transmittance was relatively high in the morning and afternoon. The variation of red and blue light in the greenhouse with the spectrum was analyzed at the same time. Studies have shown that this new greenhouse covering material can better adjust the brightness, make the illumination in the greenhouse more uniform, and thus improve the thermal environment in the greenhouse. The heat pipes converted excess light into heat, thereby achieving comprehensive utilization of solar light and heat.
关键词： Heat energy utilization,Solid CPC,Solar greenhouse roof,Light transmittance,Solar PT/D system
更新于2025-09-23 15:22:29
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Preliminary application of diffuse light film in a Chinese solar greenhouse
摘要： To explore the application of diffuse light film in a Chinese solar greenhouse (CSG), we did several comparative trials in CSGs in Beijing, Ningxia and Shandong provinces. We did three contrast tests on CSG cover films with average haze of 16.8 and 36.2%, including trials on tomatoes (in Beijing, seedlings; in Shandong, cultivation) and cucumbers (in Beijing, seedlings); the other four experiments used with films in an average haze 24.2 and 39.7%, which included trials on tomatoes (in Beijing, seedlings; in Ningxia, cultivation) and cucumbers (in Beijing, seedlings; in Ningxia, cultivation). Plant growth parameters, yield and quality index were evaluated. The result of preliminary tests showed that a higher haze film was able to improve homogeneity of light in the crop canopy and had a positive effect on cultivation. For example, in the contrast tests, we observed that a film with higher haze contributed to increases in plant height, stem diameter, leaf area, SPAD chlorophyll index, and seedling index; the seedling indices of tomatoes and cucumbers were enhanced by 50 and 10.5%, respectively, and their yields were increased by 17.0 and 21.9%, respectively, which demonstrated the outstanding impact of the higher haze films on production. Furthermore, it played a significant and positive role in flower bud differentiation of cucumbers, harvest time of tomatoes and cucumbers, and fruit quality of both crops. Based on the results of these preliminary tests, it can be concluded the diffuse film was able to accelerate plant growth and enhance crop production.
关键词： diffuse light film,Chinese solar greenhouse,tomato,cucumber
更新于2025-09-23 15:22:29
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Thermo-environomic assessment of an integrated greenhouse with an adjustable solar photovoltaic blind system
摘要： Optimum energy consumption and renewable energy utilization reduce environmental impacts and are cost-effective. They are the key aspects of achieving sustainable energy management, such as in the agricultural industry. The contribution of the horticultural section in the global energy demand is approximately 2%, and among its various sections, greenhouses are one of the main systems in modern agriculture that have a great share on energy consumption. In this study, a rose greenhouse is examined and modeled in EnergyPlus as a greenhouse reference (GR). Validation of the developed greenhouse model is carried out with a site experimental measurement. Using the GR as the basic model, 14 various configurations of greenhouses have been assessed by considering a solar photovoltaic blind system (SPBS) in checkerboard arrays 1 meter above the greenhouse roof. These modified greenhouses called solar-blind greenhouses (SBGs) have different shading rates and SPBS sizes. To perform a Thermo-environomic assessment, the effects of various parameters, including temperature, relative humidity, natural gas consumption, electricity consumption, and carbon dioxide (CO2) emission reduction, are studied. Results indicate that covering 19.2% of the roof, with no significant change in the illumination level on the plant canopy, will annually reduce natural gas consumption, electricity demand, and CO2 emission by 3.57%, 45.5%, and 30.56 kg/m2, respectively. Moreover, with the SPBS, the annual electricity production is approximated at 42.7 kWh/m2.
关键词： Energy,Solar Greenhouse,Photovoltaic,Thermo-environomic,Solar Blind System
更新于2025-09-23 15:19:57