Topic
Hour angle
About: Hour angle is a research topic. Over the lifetime, 136 publications have been published within this topic receiving 1145 citations.
Papers published on a yearly basis
Papers
TL;DR: In this paper, the authors show that at the equinoxes, for each latitude, all insolations are only a function of precession (this invalidates the results obtained by Cerveny [1991]), and at the solstices, both precession and obliquity are present.
Abstract: Solar irradiance received on a horizontal surface depends on the solar output, the semimajor axis of the elliptical orbit of the Earth around the sun (a), the distance from the Earth to the sun (r), and the zenith distance (z). The spectrum of the distance, r, for a given value of the true longitude, lambda, displays mainly the precessional periods and, with much less power, half precession periods, eccentricity periods, and some combination tones. The zenith distance or its equivalent, the elevation angle (E), is only a function of obliquity (epsilon) for a given latitude, phi, true longitude, and hour angle, H. Therefore the insolation at a given constant value of z is only a function of precession and eccentricity. On the other hand, the value of the hour angle, H, corresponding to this fixed value of z varies with epsilon, except for the equinoxes, where H corresponding to a constant z also remains constant through time. Three kinds of insolation have been computed both analytically and numerically: the instantaneous insolation (irradiance) at noon, the daily irradiation, and the irradiations received during particular time intervals of the day defined by two constant values of the zenith distance (diurnal irradiations). Mean irradiances (irradiations divided by the length of the time interval over which they are calculated) are also computed for different time intervals, like the interval between sunrise and sunset, in particular. Examples of these insolations are given in this paper for the equinoxes and the solstices. At the equinoxes, for each latitude, all insolations are only a function of precession (this invalidates the results obtained by Cerveny [1991)). At the solstices, both precession and obliquity are present, although precession dominates for most of the latitudes. Because the lengths of the astronomical seasons are secularly variable (in tenus of precession only), a particular calendar day does not always correspond to the same position relative to the sun through geological time. Similarly, a given longitude of the Sun on its orbit does not correspond to the same calendar day. For example, 103 kyr ago, assuming arbitrarily that the spring equinox is always on March 21, autumn began on September 13, and 114 kyr ago, it began on September 27, the length of the summer season being 85 and 98 calendar days, respectively, at these remote times in the past.
169 citations
TL;DR: In this article, a new combined cooling, heating and power (CCHP) system is proposed, which combines a Rankine cycle and an ejector refrigeration cycle, which could produce cooling output, heating output and power output simultaneously.
136 citations
9 Apr 2013
TL;DR: In this article, the optimum tilt angle of a solar panel was calculated by maximizing the theoretical expression of the global solar irradiation impinging on an inclined surface, with respect to the slope and orientation of the panel and to the solar hour angle.
Abstract: This paper proposes an algorithm to calculate the optimum tilt angle of solar panels by means of global horizontal solar radiation data, provided from Earth-based meteorological stations. This mathematical modeling is based on the maximization of the theoretical expression of the global solar irradiation impinging on an inclined surface, with respect to the slope and orientation of the panel and to the solar hour angle. A set of transcendent equations resulted, whose solutions give the optimum tilt and orientation of a solar panel. A simulation was carried out using global horizontal solar radiation data from the European Solar Radiation Atlas and some empirical models of diffuse solar radiation. The optimum tilt angle resulted was related to latitude by a linear regression with significant correlation coefficients. The standard error of the mean values resulted increased significantly with latitude, suggesting that unreliable values can be provided at high latitudes.
103 citations
Patent•
11 Nov 1976TL;DR: In this paper, a small satellite earth station is rocked about a single axis, corresponding to an oscillatory change in declination, but constant hour angle, and the rocking is approximately sinusoidal and has a period of one sidereal day.
Abstract: In a small satellite earth station a directional antenna is rocked about a single axis, corresponding to an oscillatory change in declination, but constant hour angle. The rocking is approximately sinusoidal and has a period of one sidereal day. In a preferred arrangement the antenna is mounted on a rocking axis pivot which is fixed at right angles to, and rotatable for adjustment about, a polar axis member. The polar axis member is set up parallel to the earth's axis and the pivot is rotated about the polar axis member to set the hour angle. The rocking of the antenna is achieved by a crank and tie-rod arrangement driven by a clock motor mounted on the polar axis member. The arrangement is particularly simple and will, when set up, track a synchronous satellite without needing frequent adjustment.
54 citations
1 Jan 2014
TL;DR: In this article, the basic solar geometry equations are given including declination, hour angle, altitude angle, azimuth angle as well as the incidence angle for stationary and moving surfaces, sun path diagrams, and shadow determination including the way to calculate shading effects.
Abstract: Chapter 2 gives an analysis of the environmental characteristics of solar radiation and in particular the reckoning of time and solar angles. In the latter the basic solar geometry equations are given including declination, hour angle, altitude angle, azimuth angle as well as the incidence angle for stationary and moving surfaces, sun path diagrams, and shadow determination including the way to calculate shading effects. This is followed by a description of the basic principles of solar radiation heat transfer including transparent plates, radiation exchange between surfaces, extraterrestrial solar radiation, atmospheric attenuation, terrestrial irradiation, and total radiation on tilted surfaces. It concludes with a review of the solar radiation measuring instruments and the way to construct typical meteorological year files.
41 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 2 |
| 2020 | 4 |
| 2019 | 4 |
| 2018 | 3 |
| 2017 | 9 |
| 2016 | 4 |