Solar constant

About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.

Global Energy and Water Balances

Abstract: The earth's energy and water balances are summarised with the most recent observational and computational results. A special reference is given to the earth's surface. After a brief discussion of the limits of the observational accuracy, the author explains the mean state of the energy balance starting with the sun, through the atmosphere and to the earth's surface. The main contents are the Total Solar Irradiance (earlier called solar constant) and its variability, the climatic effect of the earth's orbital change, extinction processes of solar radiation in the atmosphere, the distributions of solar radiation on the earth's surface, reflection and albedo, terrestrial radiation from the atmosphere and the earth's surface, net radiation, sensible and latent heat fluxes, subsurface heat flux, and latent heat of melt. The distributions of the individual components are presented in maps. The important points of geographical distributions and energy fluxes are explained in the text. The energy balance climatology in the present article differs from earlier works mainly on three topics: 1) larger atmospheric absorption of solar radiation; 2) smaller solar radiation on the earth's surface; and 3) larger terrestrial counter radiation. These new situations are the results of the recent advances in spectrometry, observational technology both on the earth's surface and in the space, and also in computational skill. Therefore, the historical development of the understanding of the earth's energy balance is added. The article ends with a brief description of the mean hydrological cycle, allowing unsteady conditions due to the melt of glaciers during the twentieth century. Keywords: energy balance; heat balance; water balance; hydrological cycle; radiation; turbulence; melt; glacier

Selection of Solar Simulator for Solar Dynamic Ground Test

Abstract: The 2 kWe Solar Dynamic (SD) Ground Test Demonstration (GTD) experiment will be conducted in 1995 at NASA Lewis Research Center (LeRC). This solar dynamic power system test will be conducted in a simulated space environment and will require an artificial sun. To address the solar simulator requirements for the GTD, Arnold Engineering Development Center (AEDC) was hired under contract to review and visit four existing solar simulator facilities. The four facilities included, AEDC's Mark 1 Chamber, NASA-JSC Chamber A, AEDC's 12V Chamber, and NASA-JPL Space Simulator Chamber. Two design concepts were considered following several months of evaluating existing solar simulator facilities throughout the United States. To satisfy system requirements for the SD GTD experiment the solar simulator needs to provide a uniform light flux to the SD concentrator, provide the light within a subtense angle of one degree, and provide an intensity of one solar constant (1.37 kW/sq m) at airmass zero. Most solar simulators are designed for supplying heat loads to spacecraft where a cone angle as large as 3 degrees is acceptable. It was also concluded that a solar simulator, such like these considered in the AEDC study, would require major facility modifications for NASA LeRC and result in significant impacts to the program. The advanced solar simulator concept developed by NASA LeRC will meet the system requirements for the SD GTD experiment Since SD GTD solar simulator requirements could not be addressed by existing simulator, an advanced concept was considered.

Solar Energy Resource and Its Global Distribution

Abstract: The sun is an extremely powerful energy resource, and the solar energy is an important renewable energy. Solar energy can be used for producing heat and generating electricity. The amount of solar energy incident on earth is enormous, and it is larger than current and predicted energy requirements in the future. In this chapter, the basic concepts and parametrical performance of the sun and its radiation across the space and earth surface including solar irradiance on earth(i.e., diffuse irradiance and direct normal irradiance, the solar constant, extraterrestrial solar spectrum, extraterrestrial solar irradiance, and extraterrestrial solar radiation on a surface), ground-level solar radiation characteristics(atmosphere effects and solar spectrum), solar angles(i.e., the earth–sun angles, hour angle, declination angle, latitude angle, solar altitude, zenith, and azimuth angles), are described. Solar energy global distribution by belt and nation at variable geometrical regions on the globe is also presented.