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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Solar radiation is an important parameter affecting light and thermal environment in solar greenhouse. Accurately obtaining the solar radiation value and variation of the interior wall and ground in the greenhouse can play an important guiding role in greenhouse design, construction, environmental regulation and crop production. On the basis of summarizing the previous models of solar radiation, a relatively perfect solar radiation model of solar greenhouse was established in this paper. Meteorological data, the laws of the earth and the movement of the sun, and the relationship between the sun's rays and the angle of the front roof were all considered in this solar radiation model. Internal radiation change of the greenhouse was analyzed based on the model. The model was verified in typical sunny days. The results showed that there were some differences between the calculated and measured solar radiation values, the MBE(mean bias error) was 63.46 W/m2, the MAE(mean absolute error) was 63.48 W/m2, the RMSE(root mean square error) was 79.18 W/m2 and the coefficient of determination R2 was high, ranged from 0.95 to 0.99. The model can be used to calculate the solar radiation intensity of the wall and the ground of solar greenhouse in any area anytime. Highly accurate analysis of the radiation change and the variation of light transmittance in the greenhouse in different seasons were achieved in this paper. It was found that the light transmittance is more affected by the solar azimuth and the solar elevation angle than by the roof angles at different positions. The solar radiation on the surface of the wall and the ground in greenhouse changes with the seasons. The spring equinox and autumn equinox are the days in which the wall and the ground received the longest solar radiation during the year. At this time, the surface of the wall is roughly equivalent to the solar radiation on the ground. From the spring equinox to the autumn equinox, the ground radiation is higher than the surface radiation, while it is opposite when it comes from the autumnal equinox to the vernal equinox. The daily accumulation of solar radiation on the wall changed little from the winter solstice to the start of spring, decreased from the start of the spring to the summer solstice and rose from the summer solstice to the start of winter. The time from winter to the start of the spring is the main production season in the greenhouse, and the heat accumulation of the wall is also the highest in the whole year. Therefore, it is of great significance to carry out research on the heat storage at this stage. Solar radiation in greenhouses in different regions is mainly affected by latitude. In lower latitudes, the amount of solar radiation in winter is large and the amount of radiation in summer is small. The research results can provide reference and related data for the study of wall heat storage, roof optimization, crop planting and energy balance of envelope in solar greenhouse. In addition, the change rule of solar radiation in greenhouse was analyzed just under clear and cloudless conditions. For the plant canopy shade, radiation under different weather conditions, insulation quilt position, different rear roof incline angles and lengths, azimuth angles, wall inclined angle and other aspects of the solar radiation change inside the greenhouse can be further explored by the method proposed in this paper. [ABSTRACT FROM AUTHOR]

The performance of greenhouse wall thermal storage and release capacity depends on the characteristics of the wall material and the thickness of the thermal storage layer. Determining the thickness of the solar greenhouse thermal storage layer is of great significance for promoting the improvement of the solar greenhouse wall. Parametric model according to the actual size and correlation of the test greenhouse was created based on the solar radiation and air temperature. Thickness of the wall thermal storage layer in different months was simulated in this study. In this paper, January 9th, February 9th, March 6th, and April 6th, 2018 in Urumqi was selected as typical sunny days. The solar radiation on the greenhouse floor and wall surface were used as the input condition, and the outdoor air temperature was the boundary conditions. The internal temperature field including each depth of 0, 10, 20, 30, 40, 50 cm of the greenhouse wall from 9:00 to next day 9:00 were simulated by using Autodesk CFD software. In order to ensure the consistency of CFD geometric models within one day and full release of heat from the greenhouse wall at night, no covering insulation quilt was carried out during the greenhouse test. The accuracy of simulated values was verified by comparing with the measured values. The results showed that the simulation results of the greenhouse wall were agreed well with the test results. The average error of each layer on January 9th, February 9th and March 6th was below 1.5 °C. The error and simulated results lags between the test results and the simulated results on April 6th is large. The trend becomes more pronounced as the depth and wall temperature increased. Under the combined influence of greenhouse wall materials, structures, and light and temperature environments, greenhouse wall heat transfer is a complex unsteady process. The brick wall greenhouse was similar to the soil wall greenhouse. The wall could be divided into “insulation layer, stable layer and heat storage layer”. The thickness of each layer was related to the thermal properties of the wall heat storage material and insulation material. The wall temperature fluctuation was more obvious in the depth range of 0-30 cm according to the temperature field of the wall, the temperature attenuation factor of each layer and the delay time. When the wall depth was more than 30 cm, the greenhouse wall temperature fluctuations was relatively flat and the amplitude is small. As the temperature rose, the internal temperature of the greenhouse wall increased overall, and the temperature fluctuations of the various layers were small. The thickness and fluctuation of the greenhouse heat storage layer were less affected by the external light and temperature environment in the case of the greenhouse structure and insulation performance unchanged. In summary, it was feasible to simulate the change of greenhouse wall temperature field. It was reliable that the thickness of greenhouse wall thermal storage layer determined according to the temperature field variation of greenhouse wall. Solar greenhouse temperature environment dynamic simulation model based on greenhouse structure parameters and environmental parameters also could be established in other regions through the methods provided in this paper. It can provide basis and reference for the improvement and optimization of greenhouse wall structure. [ABSTRACT FROM AUTHOR]

Chinese solar greenhouse(hereafter CSG) is an efficient energy-saving greenhouse, and plays an important role in Chinese protected horticulture development. Active thermal storage back wall of CSG has excellent effect of energy storage. However, the hygrothermal performance of active thermal storage wall should be studied further. In this paper, heat transfer characteristics of active heat storage wall with different structures were studied. The CSG with traditional active heat storage wall (hereafter G1) and CSG with backfill-assembled active heat storage wall (hereafter G2) was introduced for experiment based on the operation experiments of heat loss of CSG. The humiture of inlet and outlet, the surface heat flux, temperature and humidity of experiment CSG had been tested. And the heat transfer characteristics were also studied. The results showed that the wind speed at outlet of G1 was 2.82 m/s, significantly higher than that of G2. However, the wind speed of inlet of G1 was smaller than that of G2. Under continuous sunny conditions, the average temperature difference between inlet and outlet of G1 and G2 were 10.2, 11.6 °C, respectively, in the case of active thermal storage conditions; and the average temperature difference between inlet and outlet of G1 and G2 were 3.2 and 3.0 °C respectively, in the case of heat release conditions. Under continuous cloudy conditions, the average temperature difference between inlet and outlet of G1 and G2 were 1.8 and 2.3 °C respectively, in the case of heat release conditions; and the exothermic heat flux of G1 and G2 were 7.48 and 5.66 W/, respectively. The heat transfer characteristic of heat storage circulation system of active thermal storage wall were be analyzed. Research shows that the average heat exchange amount of G1 and G2 were 120.36 and 215.27 MJ, respectively, under continuous sunny conditions. And the energy efficiency ratio of G1 and G2 were 15.48 and 49.83, respectively. Therefore, the heat storage amount of G2 had a dramatic improvement compared to G1. The G2 had a better energy saving effect. Under continuous cloudy conditions, the G2 released more heat compared to G1. In the typical sunny day, the passive heat storage amount of back wall of G2 was 46.9% higher than G1 during the heat storage process and it was similar for both G1 and G2 during the heat release process. In the typical cloudy day, the passive heat storage amount of back wall of G2 was 46.4% higher than G1 during the heat storage process while the passive heat release amount of back wall of G2 was 26.2% lower than that of G1. In typical sunny day, the heat storage contributions of G1 and G2 were 30.02% and 34.32%, respectively and the heat release contributions of G1 and G2 were 27.38% and 39.35%, respectively. In typical cloudy day, the heat release contributions of G1 and G2 were 36.41% and 44.01%, respectively. Our study showed that the G2 had higher long-term heat storage capacity, and G2 would facilitate to maintain inner humiture stability of CSG under the long-term low temperature and cloudy conditions. This paper can provide a theoretical and practical guidance to thermal load design of CSG with active thermal storage system. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The typical Chinese solar greenhouse, compared to other types of greenhouse, has the properties of low construction cost and low energy consumption when operating during winter days, which draws the attention of the researcher in the field of facility horticulture. In recent years, the structural parameters, such as span, ridge height and wall thickness in Chinese solar greenhouse have been extensively studied. However, the correlation relationship between reasonable back roof projection width (BRPW) and northern wall height (NWH) have always been inconsistent and require further investigation. In this study, a new method for calculating BRPW and NWH was obtained based on the reasonable periods where the northern wall surface receive direct solar radiation in different latitude regions. Firstly, the average monthly lowest temperature and the average monthly highest temperature were statistically analyzed in some cities from January to June in 1998-2012. The data showed that when the average monthly lowest temperature was close to or exceeded 0 ℃, the average monthly highest temperature was close to or exceeded 30 ℃. Therefore, combined with the traditional Chinese solar knowledge, it is suggested that when the average monthly lowest temperature was lower than 0 ℃, it was necessary to ensure that at least part of the northern wall can receive direct solar radiation between 10:00 to 14:00 each day. Based on this, the reasonable periods where the northern wall surface received direct solar radiation in Chinese solar greenhouse in different latitude regions were obtained. Then according to the change of the sun direct light in the reasonable periods, the method for calculating BRPW and NWH in Chinese solar greenhouse was obtained. The NWH of solar radiation, which were observed at 10:00 am on winter solstice, in the solar greenhouses with different spans, were calculated by using the typical structure parameters of Chinese solar greenhouse in previous studies. The effects of thermal environment analysis were in accordance with the results in literatures. The utilization of the method for modeling the NWH of solar radiation in the well-known Shouguang solar greenhouse in various date confirmed that the actual period where the northern wall accept the direct solar radiation was close to the reasonable period proposed in this study, further suggesting the feasibility of this method. The method has been used to calculate the front roof lighting angle, ridge height, BRPW and NWH in solar greenhouses with various spans in different cities in China. The ratio of BRPW to the span in solar greenhouse ranged from 0.04 to 0.23, which varied in in geographic locations and climatic conditions. When the climatic conditions in different areas were similar, the increase of latitude resulted in an increase of BRPW. The areas with lowest BRPW ratio (0.04 to 0.11) were located in Taiyuan, Xi’an, Lanzhou, Xining, Yinchuan and other low-latitude cold regions. These results suggested that the BRPW can be slightly decreased in cold areas and appropriately increased in warm regions. This method can provide theoretical guidance for optimal design of solar greenhouse in China. [ABSTRACT FROM AUTHOR]