Shading Ratio Research Articles

EFFECT OF POLY-GREENHOUSE SHADING RATIOS ON GERMINATION AND YIELD OF TOMATO UNDER FAYOUM DEPRESSION CLIMATIC

Four similar experimental poly-greenhouse models with different shading rations and ventilation gaps were used and compared with the open field condition. One of the four poly-greenhouse models was covered by a single layer of polyethylene (without shading), and the others three models were covered with an external black screen shade net sheets of 25%, 63% and 75% shading ratios, during the winter months. While, three poly-greenhouse models were covered only with black screen shade net sheets of 25%, 63% and 75% shading ratios during the summer months. The thermal performance of the greenhouse models and their effects on seedlings germination and yield of tomato (GSI Seed, Hybrid Tomato, Nora-765) were investigated under Fayoum depression climatic conditions during the winter and summer months of 2009. The obtained results indicated that the air temperature inside the un-shaded model was almost higher than in shaded models and ambient temperature during the winter months (January to May). The air temperature inside the greenhouse models covered only by black screen shade net sheets of 63% and 75% shading ratios were down the ambient temperature during the summer months (June to October) with ventilation rate during the night time. All shading ratios caused to increase the relative humidity inside the greenhouse models, especially with 63% and 75% shading ratios. As shading ratio increased the light intensity decreased, and thus, the light intensity was adequate when it decreased by 63% and 75%, which is satisfactory for seedlings germination, plant growth and yield of tomato at the summer months. Poly-greenhouse with single layer of polyethylene was found more suitable for seedlings germination, plant growth and yield of tomato than those with the other shading ratios and open field condition during the winter months. Poly-greenhouse covered only by black screen sheets (especially with 63% or 75% shading ratios) was found more suitable for better seedlings germination, plant growth and yield of tomato than this with 25% shading ratio and open field condition in the summer months.

Operative temperature and thermal sensation assessments in non-air-conditioned multi-storey hostels in Malaysia

This study assessed the influences of operative temperature on occupants’ perceptions of indoor thermal condition in three non-air-conditioned multi-storey hostels in Klang Valley, Malaysia. The thermal conditions of 24 measured rooms were recorded with and without an operating ceiling fan from May until July 2007. Measurements were made simultaneously at three different floor levels, namely, at the first, fifth and top floor of each of the case study hostels. A questionnaire survey was completed by 298 female student occupants of the same case study hostels. The results suggested that even though a significance above p < 0.01 was recorded between the operative temperatures with and without fan operation, the temperature difference remained small, i.e., from 0.5 K to 1 K. The findings of the questionnaire survey showed that the occupants perceived the thermal conditions in rooms that were shaded with a projected balcony (shading ratio of 0.9), a long roof overhang (shading ratio of 1.6) and an operable window-to-wall ratio of 0.3 to be thermally comfortable.

Numerical model analysis of the shaded dye-sensitized solar cell module

On the basis of a numerical model analysis, the photovoltaic performance of a partially shadowed dye-sensitized solar cell (DSC) module is investigated. In this model, the electron continuity equation and the Butler–Vollmer equation are applied considering electron transfer via the interface of transparent conducting oxide/electrolyte in the shaded DSC. The simulation results based on this model are consistent with experimental results. The influence of shading ratio, connection types and the intensity of irradiance has been analysed according to experiments and numerical simulation. It is found that the performance of the DSC obviously declines with an increase in the shaded area due to electron recombination at the TCO/electrolyte interface and that the output power loss of the shadowed DSC modules in series is much larger than that in parallel due to the ‘breakdown’ occurring at the TCO/electrolyte interface. The impact of shadow on the DSC performance is stronger with increase in irradiation intensity.

태양전지 모듈의 바이패스 다이오드 동작 특성 분석

In this paper, an I-V characteristics of bypass diode has been studied by counting the shading effect in photovoltaic module. The shadow induces hot spot phenomenon in PV module due to the increase of resistance in the current path. Two different types of PV module with and without bypass diode were fabricated to expect maximum output power with an increasing shading rate of 5 % on the solar cell. Temperature distribution is also detected by shading the whole solar cell for the outdoor test. From the result, the bypass diode works properly over 60 % of shading per cell with constant output power. Maximum power generation in case of solar cell being totally shaded with bypass diode decreases 41.3 % compared with the one under STC(Standard Test Condition). On the other hand, the maximum output power of the module without bypass diode gradually decreases by showing hot spot phenomenon with the increase of shading ratio on the cell and finally indicates 95.5 % of power loss compared with the output under STC. Finally the module temperature measured increases around <TEX>$10^{\circ}C$</TEX> higher than that under STC due to hot-spots which come from the condition without bypass diode. It has been therefore one of the main reasons for degrading the PV module and shortening the durability of the PV system.

R12 hydrate formation kinetics based on laser light scattering technique

A circulating flow system consisting of a transparent U-bend flow loop, a mixing tank and a laser granulometer was set up for studying the kinetics hydrate formation and the pressure is up to 4 MPa. Refrigerant CCl 2 F 2 (R12) hydrate formation experiments were performed using laser light scattering method at 277.1 K and pressures of 0.24 and 0.32 MPa. The liquid flow rates were in the range of 300—1400 L/h. The size distribution and density of R12 hydrate particles in pure water were measured using a laser granulometer. Experimental results show that the size of hydrate particles increases sharply at the initial stage and approaches gradually to a stable size. The hydrate particle concentration in the aqueous phase increases with pressure and circulating liquid flow rate. Based on the material balance, the mathematical model among gas consumption, average hydrate particle size and shading ratio has been established. The calculated results using the mathematical model accord well with the experimental gas consumption data.

Spectral shade ratios on horizontal and sun normal surfaces for single trees and relatively cloud free sky

Spectral shade ratios, defined as the ratios of the spectral irradiances on horizontal and sun normal planes in the tree shade to those on a horizontal plane in sunlight, were calculated. These planes were in the shade of an isolated medium canopy density tree and a sparse canopy density tree at the tree shade sites of the centre, edge and trunk. The sun normal plane was employed as there are some activities that have exposures to parts of the body that are orientated in a sun normal plane. The horizontal plane shade ratios for the medium density canopy dropped by 47–56% from the ratios in the range 301 to 310 nm to the ratios in the range 391 to 400 nm. In absolute terms, the largest change in the shade ratio of 0.28 was for the centre and edge sites compared to 0.07 for the trunk. Similarly, for the sun normal plane, the ratio dropped by 40–49% with an absolute reduction of 0.19 for the edge and 0.04 for the trunk. For the sparse density canopy, the decrease in the shade ratios over the same wavelength range was a drop by 37–42% on a horizontal plane or, in absolute terms, a reduction by 0.22 for the edge and 0.13 for the trunk. Similarly, the decrease was 34–39% on the sun normal plane or, in absolute terms, a reduction by 0.19 for the edge and 0.12 for the trunk.

Comparison of the spectral biologically effective solar ultraviolet in adjacent tree shade and sun

The solar spectral UVR irradiances in tree shade and sunlight have been measured in a sub-tropical southern hemisphere summer. The spectral data allowed the UVB and UVA irradiances and the biologically effective irradiances to be calculated for different harmful biological processes to human skin and eyes. The average of the ratio of the UVA to UVB irradiances was lower by 26% in the shade compared with the same ratio in the sun. The spectral shade ratio calculated as the ratio of the spectral biologically effective irradiances in the shade to those in the adjacent sun decreased with increasing wavelength for all of the trees. The decrease in the shade ratio was approximately 42% at 400 nm compared with the shade ratio at 300 nm. Despite the UVR protection provided by tree shade, the erythemal UVR exposure received in 1 h in the tree shade exceeded the occupational limit for UVR exposure.

EFFECT OF SHADING ON GROWTH AND QUALITY OF SUMMER SPINACH

Spinach (Spinacia oleracea L. cv. Active) was cultivated four times during the summer season (from June to September) in four plastic houses with different aluminum coated polyethylene nets which had 0%, 30%, 45%, and 60% shading ratios, respectively, to prevent the increase of air and soil temperature in plastic houses. Integrated solar radiation in plastic houses was decreased as shading ratio increased. Air and soil temperatures were kept the same. Spinach growth was the best under 45% shading ratio in June, August, and September and 60% in July. Sugar and ascorbic acid (vitamin C) contents were decreased as shading ratio increased in all seeding times. Nitrate content was highest under 45% shading ratio in July, August and September and 30% in June. Soluble oxalate content was highest in June, July, and August and lowest in September in the non-shaded house.

Instrumental Evaluation of Fabric Wrinkle Recovery

This paper describes the application of computer image analysis techniques to characterization and quantification of fabric wrinkling for the purpose of devising an automated rating system of fabric wrinkle recovery. Two variables, surface ratio and shade ratio, are defined to quantify wrinkled appearance. The techniques for measuring these variables are discussed. Based on the analysis of the AATCC wrinkle recovery replicas using these techniques, we found that each of these two variables approximately exhibits an exponential relationship with the grades presented by the replicas. Through non-linear regression, two empirical equations are formulated to serve as mathematical models for grading fabric wrinkle recovery. The wrinkle recovery of seven different fabrics is evaluated, respectively, by observers using AATCC test method 128 and by the image system. Results show that the computer grading is highly consistent with the visual grading, and is more accurate and reliable.

植物を配置した室内の温熱環境・快適性の予測モデルの作成

In this study, the authors made a non-steady state simulation model of the thermal environment and comfort in the rooms where plants were placed. The room which was assumed in the simulation model was the same room that used in our previous experiment (Asaumi et al., J. Archit. Plann. Environ. Eng., AIJ, 464, 1994) . Ornamental foliage plants which were assumed to be placed in the room were Schefflera arboricola “Hong Kong, ”Dracaena fragrans“Massangeana, ”Ficus benjamina and Epipremnum aureum, and the stomatal resistances and shading ratios measured in our previous experiment (Asaumi et al., SHITA J., 4 (2), 1993) were applied. Simulation was conducted concerning the data on January 5, 1993, and the results were compared with the results of our previous experiment (Asaumi et al., 1994) . Furthermore, simulation was conducted concerning the data on the standard sunny day in April. The results of the simulation of January 5, 1993 showed the same tendency as the results of our previous experiment (Asaumi et al., 1994), so the simulation model was considered to be valid. Therefore, the simulation model is useful for the design of the thermal environment and comfort in rooms where plants are placed.

アメニティ植物の蒸散量・気孔抵抗および遮光率の測定

アメニティ植物の蒸散量・気孔抵抗および遮光率の測定

雲仙普賢岳と桜島火山灰の付着がキュウリの葉温と気孔コンダクタンスに与える影響

This study was conducted to infer the effects of volcanic ash accumulating on a leaf surface on its photosynthesis. Particle size distribution and shading ratio were measured on 2 kinds of ash from Mt. Sakurajima (white and black) and 4 kinds from Mt. Unzen-Fugendake. Reflected spectral radiant flux density, temperature and Stomatal conductance of cucumber leaves covered with those ashes were also measured.Particle size distribution of ashes were different each other, Particle (<3μm) contents of them were 6 to 13%. Shading ratios were 8 to 20% at 5gm-2 of ash load. The ash with smaller particle size had bigger shading ratio. Integrated radiant flux density (280-2500nm) of reflection from leaves covered with ashes from Mt. Sakurajima (black and white) and Mt. Unzen-Fugendake at 50gm-2 were 65, 53 and 106% to control leaves, respectively. Temperature of leaves covered with these ashes at 50gm-2 increased by 2.4, 2.6 and 1.2°C, respectively, at a solar radiation of 876 W m-2. The ash from Mt. Unzen-Fugendake, with the smallest particle size, decrease stomatal conductance significantly even after it was washed out from the leaf surface. These results suggest that the volcanic ash with dark color and small particle size reduces photosynthesis through shading, increasing temperature and plugging stomata.