Shaded Spacecraft Radiators to Be Used on the Daytime Surface of the Mercury Planet, the Moon, and Asteroids of the Solar System Inner Part

This chapter is concerned with the measurement of solar radiation that reaches the earth’s surface and with the measurement of earth radiation, the long wave band of radiation emitted by the earth. The unit of radiation used in this chapter is the Wm-2. Table 10-1 lists some conversion factors. Radiant flux is the amount of radiation coming from a source per unit time in W. Radiant intensity is the radiant flux leaving a point on the source, per unit solid angle of space surrounding the point, in W sr-1 (sr is a steradian, a solid angle unit). Radiance is the radiant flux emitted by a unit area of a source or scattered by a unit area of a surface in Wm-2 sr-1. Irradiance is the radiant flux incident on a receiving surface from all directions, per unit area of surface, in Wm-2. Absorptance, reflectance, and transmittance are the fractions of the incident flux that are absorbed, reflected, or transmitted by a medium. Global solar radiation is the solar irradiance received on a horizontal surface, Wm-2. This is the sum of the direct solar beam plus the diffuse component of skylight, and is the physical quantity measured by a pyranometer. Direct solar radiation is the radiation emitted from the solid angle of the sun’s disc, received on a surface perpendicular to the axis of this cone, comprising mainly unscattered and unreflected solar radiation in Wm-2. At the top of the atmosphere this is usually taken to be 1367 W m-2 ± 3% due to changes in the earth orbit and due to sunspots. The direct beam is attenuated by absorption and scattering in the atmosphere. The direct solar radiation at the earth’s surface is the physical quantity measured by a pyrheliometer. Diffuse solar radiation (sky radiation) is the downward scattered and reflected radiation coming from the whole hemisphere, with the exception of the solid angle subtended by the sun’s disc in Wm-2. Diffuse radiation can be measured by a pyranometer mounted in a shadow band, or it can be calculated using global solar radiation and direct solar radiation.

In this article, the results of the estimation of total and direct solar radiation in the summer season over the territory of Ukraine depending on changes in planetary and regional atmospheric circulation since the beginning of the 21st century are presented. The estimation was conducted for the period from 1991 to 2020 based on the ERA5 reanalysis data, which is currently considered one of the best and most widely used models. General trends in the increase in the values of total and direct solar radiation over the territory of Ukraine have been established. The detected increase has been occurring since 2001, which corresponds to the time of display of a new regional atmospheric circulation. The amounts of direct and total solar radiation increased on average by 100—150 MJ/m2 in the second decade of the 21st century compared to the last decade of the 20th century. There is a synchronous change in total and direct solar radiation. Analysis of individual summer months revealed that the lowest values of direct solar radiation over the territory of Ukraine were observed in 2001 and the highest in 2019. At the same time, the difference in monthly sums between these years was 150—170 MJ/m2. In July, the lowest values of direct solar radiation were observed in 1997, and the highest values in 2012. The difference in monthly sums is close to the values of June. In August, the lowest values of direct solar radiation were observed in 1997 and the highest in 2015 and 2018. The difference between the sums per month for these years is close to the values of the previous summer months. In August, although the increase in total and direct solar radiation persists, as in June and July, their values for this month are already lower than those of the two previous months. In general, the increase in direct solar radiation over the territory of Ukraine is determined by new features of the course of synoptic processes with a stable anticyclonic character, which cause cloudless or partly cloudy, hot weather without precipitation.

The Yuma Test Station, Arizona, hourly and daily insolation record, 1951–1962 : Bennett, Iven, U. S. Army Natick Laboratories, Natick, Mass., U. S. Army Materiel Command, Technical Report ES-15, March 1965, 57 p. illus.

Analysis of Hourly Global, Direct and Diffuse Solar Radiations Attenuation as a Function of Optical Air Mass

There are various empirical models used in the estimation of global solar radiation; however, knowledge of direct and diffuse solar radiation is insufficient. Global solar radiation is the sum of direct and diffuse solar radiation, and a method that calculates global solar radiation from the estimated direct and diffuse solar radiation was further proposed in this study. The observed daily solar radiation and meteorological data from 97 stations during 1993–2016 were used for the analysis, and the results indicated that the concave-shaped relationship with relative sunshine duration was more obvious for direct solar radiation than for global solar radiation, while an inverted u-shaped relationship was found for diffuse solar radiation. Generally, the performances of empirical models in estimating direct and diffuse solar radiation were worse than the estimation of global solar radiation. However, because the bias of estimated direct and diffuse solar radiation was partially offset, the results in this study indicated that global solar radiation can be better calculated from the estimated direct and diffuse solar radiation when compared with the best performed empirical model, especially in data-scarce regions. The results of this study will aid in better estimations and understanding of the variations in global solar radiation, as well as direct and diffuse solar radiation.

The long-term variability of direct and diffuse solar radiation at the surface remains unknown for many areas of the world due to the lack of measurements. In this study, two methods, an empirical model and a neural network, are used to estimate annual direct and diffuse solar radiation in North China for the 1959–2016 period. Results reveal that the two methods have a good performance in estimating direct solar radiation (R2 = 0.49–0.95), and the estimation accuracy of diffuse solar radiation can be improved by incorporating the influence of aerosols (R2 = 0.29–0.79). Generally, total and direct solar radiations have significantly decreased with the declining trend in sunshine duration since 1959 (p < 0.01). However, diffuse solar radiation shows a significant (p < 0.01) increasing tendency over the period of 1959–2016. The proportions of direct and diffuse solar radiation are almost equal from 1982 onward. Influenced by the atmospheric aerosols, two periods with large diffuse solar radiation values have been observed from 1959 to 1989 and from 2004 to 2016. Over the period of 2000–2016, sunshine duration and aerosols can explain 89 and 85% of direct and diffuse solar radiation variations, where aerosol concentration accounts for about 63% of changes in diffuse solar radiation. This study characterizes the long-term variability of direct and diffuse solar radiation in North China since 1959 and highlights the significance of aerosols to diffuse solar radiation from 2000 to 2016.

The impact of the atmospheric pollution on the direct solar radiation regime in Georgia was studied. As a quantitative parameter for the atmospheric pollution level the optical depth of atmospheric aerosols (τa) was used. Computer calculations of the direct Solar radiation using the data on (τa) for Georgia showed that the increasing level of the atmospheric pollution causes a reduction in the direct incident Solar radiation irradiance.The impact of the atmospheric pollution on the direct solar radiation regime in Georgia was studied. As a quantitative parameter for the atmospheric pollution level the optical depth of atmospheric aerosols (τa) was used. Computer calculations of the direct Solar radiation using the data on (τa) for Georgia showed that the increasing level of the atmospheric pollution causes a reduction in the direct incident Solar radiation irradiance.

Environmental Effects on the Performance of Nanocrystalline Silicon Solar Cells

The measurement of direct and diffuse solar radiation is not easily possible because instruments are quite expensive. The main objective of this study was to predict direct solar radiation (IB) and diffuse solar radiation (ID) on Pokhara (28.186643o N, 83.97518o E, 800 m asl) for a period of one year (2017). Daily data of spectral Aerosol optical depth (AOD) and total ozone column are obtained from NASA website. The maximum value of direct solar radiation and diffuse solar radiation values were found 932.9 ± 65.9 W/m2 in January and 363.0 ± 87.9 W/m2 in February respectively. The minimum value of direct solar radiation and diffuse solar radiation values were found 692.8 ±142.0 W/m2 in April and 107.7 ± 20.4 W/m2 in July respectively. The diffuse solar radiation changes with season. The annual average of direct solar radiation and diffuse solar radiation are found 808.1± 133.7 W/m2 and 220.8 ± 102.8 W/m2 and respectively. The results of this research work will help further identification, impact and analysis of solar radiation in different locations in Nepal with the same geographic conditions.

When the sun shines on people in enclosed spaces, such as in buildings or vehicles, it directly affects thermal comfort. There is also an indirect effect as surrounding surfaces are heated exposing a person to re-radiation. This laboratory study investigated the effects of long wave re-radiation on thermal comfort, individually and when combined with direct solar radiation. Nine male participants (26.0 ± 4.7 years) took part in three experimental sessions where they were exposed to radiation from a hot black panel heated to 100°C; direct simulated solar radiation of 600 Wm−2 and the combined simulated solar radiation and black panel radiation. Exposures were for 30 min, during which subjective responses and mean skin temperatures were recorded. The results showed that, at a surface temperature of 100°C (close to maximum in practice), radiation from the flat black panel provided thermal discomfort but that this was relatively small when compared with the effects of direct solar radiation. It was concluded that re-radiation, from a dashboard in a vehicle, for example, will not have a major direct influence on thermal comfort and that existing models of thermal comfort do not require a specific modification. These results showed that, for the conditions investigated, the addition of re-radiation from internal components has an effect on thermal sensation when combined with direct solar radiation. However, it is not considered that it will be a major factor in a real world situation. This is because, in practice, dashboards are unlikely to maintain very high surface temperatures in vehicles without an unacceptably high air temperature. This study quantifies the contribution of short- and long-wave radiation to thermal comfort. The results will aid vehicle designers to have a better understanding of the complex radiation environment. These include direct radiation from the sun as well as re-radiation from the dashboard and other internal surfaces.

The main objective of the study is to estimate direct solar radiation (IB) and diffuse solar radiation (ID) on Bode, Bhaktapur (27.68° N, 85.39° E, 1297 m a. s. l.) for a period of one year (2013). Daily data of Aerosol optical depth (AOD), total ozone column are derived from NASA website. The maximum and minimum monthly average of diffuse solar radiation values were found 318±95 W/m2 in April and 108 ± 20 W/m2 in August respectively. The maximum and minimum monthly average of direct solar radiation values were found 975±74 W/m2 in February and 748 ± 126 W/m2 in March respectively. The annual average of diffuse solar radiation and direct solar radiation are found 216 ± 88 W/m2 and 864 ± 125 W/m2 respectively. Result of this research work is beneficial for the further identification, impact and analysis of direct solar radiation diffuse solar radiation at different places.

Solar energy is the cleanest and most common renewable energy source. The solar energy market today is almost 103 gigawatts (GW). According to the International Energy Agency (IEA), about 125 GW of solar energy is produced in the world. In Ukraine, the average annual amount of total energy of solar radiation ranges from 1,070 kWh/m? in the northern part of Ukraine to 1,400 kWh/m? and above in the Autonomous Republic of Crimea. Along with a fairly large number of works devoted to the components of the radiation balance, research is mainly conducted to study their spatio-temporal distribution over the territory, and in Ukraine, the main source of data remains the few weather stations at which relevant observations are made. This exploration uses data from surface observations and reanalysis data. In particular, the surface observation data were taken from the Borys Sreznevsky Central Geophysical Observatory. Reanalysis data - from the European Center for Medium-Range Weather Forecasts, ECMWF [http://www.ecmwf.int/en/research/climate-reanalysis/era-interim]. For the exploration, 5 large cities of Ukraine were chosen, which highlight different parts of the country - Kyiv, Kharkiv, Lviv, Dnipro and Odesa. Validation was carried out on surface observation data using data covering the period 2008-2020. An exploration of the temporal distribution of direct, diffuse and total solar radiation was carried out on reanalysis data covering the period 1991-2020. For each city as a whole, for the summer and for a single month of the season, the values of direct, diffuse and total solar radiation were obtained according to the reanalysis data. The minimum and maximum values that occurred are determined. For each city, a general trend for the summer as a whole and separately for June, July and August was obtained. It was found that the reanalysis tends to underestimate diffuse and overestimate direct solar radiation. According to the reanalysis data, the changes in diffuse solar radiation are insignificant in terms of values for all cities, in terms of the actual direction of changes - for Kyiv, Kharkiv and Lviv, in Dnipro and Odesa at the end of the studied period there is a tendency for it to decrease. In general, these conclusions are confirmed by the data of surface observations, with the exception of Kyiv (for all summer months), as well as for June in Odesa and Lviv, where an increase in its values is observed at the end of the studied period. The largest fluctuations (both according to surface observations and reanalysis) occur for direct solar radiation and, as a result, appear in the amount of total solar radiation. In general, for the summer period in all five cities, there is a tendency to a slight increase in the amount of total solar radiation.

Multi-step ahead forecasting of daily global and direct solar radiation: A review and case study of Ghardaia region

During the observation period, significant changes in the influx of short-wave solar radiation due to the conditions of their passage through the Earth’s atmosphere and reflection from the underlying surface are registered. In the course of the study, the archive of observations of the meteorological and actinometric observation network of the Borys Sreznevsky Central Geophysical Observatory of the State Emergency Service of Ukraine was involved. A database of individual components of the Solar radiation regime has been compiled. Based on the methods of mathematical statistics, calculations of their spatial and temporal distribution on the territory of Ukraine were carried out. The results of changes in the components of the Solar radiation regime: direct, diffuse, and total solar radiation, albedo of the underlying surface, complete radiation balance and duration of sunshine during individual months, cold and warm periods, and year for the last three decades (1991-2020) relative to the climatological standard norm (1961-1990). Features of the modern climate affect the distribution of the components of the radiation regime and their change over the last three decades. This determines the expediency of determining the dynamics of the components of the radiation regime and their spatial distribution. The following components of the radiation regime experienced the greatest changes: duration of sunshine, direct and diffuse solar radiation. An increase in the duration of sunshine and direct solar radiation in the warm period of the year in a larger area of the country is characteristic. Scattered solar radiation decreased in almost all months of the cold and warm period almost everywhere in Ukraine. The total radiation increased during the warm period of the year, especially in the north and in the southern Steppe. The albedo of the underlying surface increased slightly, especially during the warm period in the south. The total radiation balance increased over a large area of the country, especially in the northeast and northwest. The determined changes in the formation of the components of the radiation regime are accompanied by changes during the growing season, with a tendency to increasing aridity and significantly affect the conditions for growing agricultural crops in Ukraine, which causes their spread across the territory. Their importance in the energy sector is due to the need to determine the profitability of operating solar energy plants for the production of electricity. The obtained conclusions are important for the use in the construction and operation of buildings of various purposes, as well as in general for climatic management of sectors of economy.

A method is proposed for estimating monthly mean hourly direct, diffuse, and global solar radiation from annual stochastical models (correlation coefficients are higher than 0.99), using only actual and daily maximum solar elevation and respective daily radiation as input data. The annual model (based on data collected on 45.8° northern latitude) of monthly mean hourly global solar radiation relative to the monthly mean daily radiation is found to be acceptable for latitudes between 40 and 50°N, if compared to other models. The same latitudinal validity is assumed for the annual models of diffuse and direct solar radiation. Similar models for other latitudes could be derived if representative pyrranometer data are available.