Definition of Characteristics of Instantaneous Diurnal Activity of Human Body Affected by Solar Radiation in the Circadian Region of Optical Spectrum during Daytime

The article reviews the impact of daily changes in characteristics of solar radiation in the circadian region of optical spectrum on diurnal (circadian) activity of human body with changes of solar altitude angle. Analytical expressions, allowing to theoretically estimation instantaneous melatonin content in human blood plasma and dependence of instantaneous human activity during daytime on solar altitude angle, were obtained.

Analytic Representation of Illuminance on the Earth Surface with Different Types and Conditions of Cloud Cover over the 11-Year Solar Activity Cycle

The article describes the analytical expression approximating experimental data on daily natural illuminance on the Earth surface with different types and conditions of cloud cover over the 11-year solar activity cycle within the solar altitude angle range of 0 ° to 90 °. The values of the direct, diffused, and total illuminance on the Earth surface with different types and conditions of the cloud cover and, to some extent, of the substrate were defined and summarised in tables. The data presented may be used as part of the visual perception studies, light and engineering calculations, architecture and construction practice, etc.

Diurnal Cycle Model of Lake Ice Surface Albedo: A Case Study of Wuliangsuhai Lake

Ice surface albedo is an important factor in various optical remote sensing technologies used to determine the distribution of snow or melt water on the ice, and to judge the formation or melting of lake ice in winter, especially in cold and arid areas. In this study, field measurements were conducted at Wuliangsuhai Lake, a typical lake in the semi-arid cold area of China, to investigate the diurnal variation of the ice surface albedo. Observations showed that the diurnal variations of the ice surface albedo exhibit bimodal characteristics with peaks occurring after sunrise and before sunset. The curve of ice surface albedo with time is affected by weather conditions. The first peak occurs later on cloudy days compared with sunny days, whereas the second peak appears earlier on cloudy days. Four probability density distribution functions—Laplace, Gauss, Gumbel, and Cauchy—were combined linearly to model the daily variation of the lake ice albedo on a sunny day. The simulations of diurnal variation in the albedo during the period from sunrise to sunset with a solar altitude angle higher than 5° indicate that the Laplace combination is the optimal statistical model. The Laplace combination can not only describe the bimodal characteristic of the diurnal albedo cycle when the solar altitude angle is higher than 5°, but also reflect the U-shaped distribution of the diurnal albedo as the solar altitude angle exceeds 15°. The scale of the model is about half the length of the day, and the position of the two peaks is closely related to the moment of sunrise, which reflects the asymmetry of the two peaks of the ice surface albedo. This study provides a basis for the development of parameterization schemes of diurnal variation of lake ice albedo in semi-arid cold regions.

Analytic Representation of Relation between Solar Altitude Angle and Local Time for Calculating Daylight Irradiance and Illuminance of the Earth Surface

The analytic expression which sets relation between the solar altitude angle and local time at a random point of the Earth surface on a random day of a year is obtained. The obtained expression and derived relations allow one to conduct calculations of daylight irradiance and illuminance of the Earth surface in analytic form.

Building Shadow Detection on Ghost Images

Although many efforts have been made on building shadow detection from aerial images, little research on simultaneous shadows detection on both building roofs and grounds has been presented. Hence, this paper proposes a new method for simultaneous shadow detection on ghost image. In the proposed method, a corner point on shadow boundary is selected and its 3D approximate coordinate is calculated through photogrammetric collinear equation on the basis of assumption of average elevation within the aerial image. The 3D coordinates of the shadow corner point on shadow boundary is used to calculate the solar zenith angle and the solar altitude angle. The shadow areas on the ground, at the moment of aerial photograph shooting are determined by the solar zenith angle and the solar altitude angle with the prior information of the digital building model (DBM). Using the relationship between the shadows of each building and the height difference of buildings, whether there exists a shadow on the building roof is determined, and the shadow area on the building roof on the ghost image is detected on the basis of the DBM. High-resolution aerial images located in the City of Denver, Colorado, USA are used to verify the proposed method. The experimental results demonstrate that the shadows of the 120 buildings in the study area are completely detected, and the success rate is 15% higher than the traditional shadow detection method based on shadow features. Especially, when the shadows occur on the ground and on the buildings roofs, the successful rate of shadow detection can be improved by 9.42% and 33.33% respectively.

ABSORBER PLATES POSITION INFLUENCE ON SOLAR COLLECTOR OPERATION EFFICIENCY

In order to increase the operating efficiency of solar power generating system its absorbing surface must be continuously turned towards the Sun. Modern Sun tracking systems are analyzed. Operation of solar air wall-type collector is considered. Collector’s absorber plates were situated in two ways – horizontally and vertically. Operation of the collector with horizontally situated plates is to turn of the plates towards the Sun according to solar altitude angle. Vertically situated plates position depends on solar azimuth angle. Cross shading of the absorbers plates during Sun tracking is calculated. To estimate the collector efficiency its operation within two days of the year (1.01.2016 and 11.06.2016) is studied. In order to compare the collectors’ characteristics with different types of the absorber the mathematical model is built.

Calculation and Distributive Characteristics of Solar Radiation in Henan Province

Taking factors such as astronomy, atmosphere, microgeography and local landscape that comprehensively affect solar radiation into account, we established a direct solar radiation (DSR) model on the accidented topography. Dynamics of DSR on accidented topography in Henan province were also statistically analyzed. Modeling results showed that highest DSR in Henan occurred between May and July, while lowest DSR occurred between December and February of the next year, and the multi-annual mean DSR in Henan province was 2127.7MJ/ m2. Impacts of local landscape on DSR on accidented topography in Henan province differs in different seasons. In winter half year, during which solar altitude angle is relatively low, this impact is more significant.

The Tracking of the Sun for Solar Paraboloidal Dish Concentrators

Paraboloidal dish concentrators need tracking the sun in the east-west and north-south direction continuously throughout the year. But this paper explains the method of intermittent tracking of the sun in the north-south direction with no tracking in the east-west direction for less energy yield. The frequency of tracking in the north-south direction is determined by the relationship between the variation in solar altitude angle and the size of the absorber in the Paraboloidal dish concentrator. A computer program in Visual BASIC is written to enable the detailed calculations of data for the analysis.© 2004 American Institute of Physics.