Comparison of thermal and light performance in two typical Chinese solar greenhouses in Beijing

Abstract

Solar greenhouses have been used for producing vegetables in northern China during early spring, late autumn or over-winter. To improve the thermal performance of solar greenhouses, a traditional type and a retrofitted design were comparatively evaluated. In the retrofitted design, three adjustments were incorporated: the material and structure of the walls, south-facing roof angle, and structure of the north-facing back-roof. The results indicated that the thermal and light performance of the retrofitted greenhouse was much better than that of the traditional greenhouse. Specifically, the daily mean temperature, minimum air temperature, and soil temperature inside the greenhouses after retrofit ting were increased by 1.3, 2.4, and 1.9°C, respectively, meanwhile, the daily total solar radiation and PAR were increased by 28.2% and 9.2%, respectively. The wall temperature and its daily variation range were reduced with increasing depth and height. The characteristic analysis of heat storage and release indicated that higher locations have longer heat storage, and shorter heat release time in vertical direction, as well as a lower ratio of heat release to storage. In horizontal direction, the western wall has the shortest heat storage time but the highest heat release flux density. Altogether, the heat storage time of the wall is 1.5 h less than that of the soil. The heat storage flux density of the wall is 1.5 times of that of the soil, but the heat release flux is only 61% of the soil's value. The total wall heat storage is half of that of the soil in the greenhouse; the total wall heat release amount is only a quarter of that of the soil. Therefore, the thermal environment of solar greenhouses can be further improved by improving the thermal insulation properties of the wall.

Modeling and simulation of temperature control system in plant factory using energy balance

“…A typical light-transmitting greenhouse with natural ventilation consists of some structural materials (glass, plastic), surface soil, architectural components, heating and vents [33] . Taking the air and crops in the greenhouse as the research object, two forms of energy can be divided, including the sensible heat and latent heat.…”

Analysis of the Effect of Exhaust Configuration and Shape Parameters of Ventilation Windows on Microclimate in Round Arch Solar Greenhouse

“…Currently China's energy-efficient solar greenhouses have been able to produce winter tomatoes, cucumbers, and other thermophilic vegetables under the condition of no warming measures, relying only on solar radiation [1][2][3]. The high production efficiency and annual intensive production of solar greenhouses have improved the land utilization rate, greatly increasing the production per unit area, effectively alleviating the problem of difficult supply of vegetables in the off-season in China, especially in the north, and greatly increasing the economic income of farmers [4][5][6]. Traditional solar greenhouse structures are mostly brick-walled or soil-walled thermal storage structures.…”

Performances of an air thermal energy utilization system developed with fan-coil units in large-scale plastic tunnels covered with external blanket

“…It could maintain high interior air temperature without or with a little amount of heating [1,2] . However, this type of greenhouse has the flaws of high construction cost, low land utilization efficiency, narrow space, etc [3,4] . As a result, a large-scale plastic tunnel with an external thermal blanket (LPTEB) has been employed in recent years to address the above issues.…”