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Solar Energy Resources
Published in Radian Belu, Fundamentals and Source Characteristics of Renewable Energy Systems, 2019
There is a strong relationship between the solar azimuth and hour angles, the first being the angle on the horizontal plane between the solar radiation projection and the line of the north-south direction, its positive values are indicating that the Sun is west of the south, while the negative values indicate that the Sun is east of the south. The hour angle represents the angular distance between the Sun position at a particular time and its highest position for that day when crossing the local meridian at the solar noon. The length of the day varies for all latitudes during the year, so the solar altitude angle also changes hourly and daily, as expressed in Equation (2.11). To avoid the failures of Equation (2.11) because the arcsine of a negative number does not exist, it is advisable to implement the following equation: () αS=arctan(sin(αS)cos(αS))
Definitions and Terminology
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
To an observer on the Earth at 40°N latitude, the celestial sphere is tilted as in Figure 2.4. Note that the closer the observer is to the equator, the closer the equatorial plane is to the zenith, or equivalently the east and west horizon. And on the spring equinox and the autumn equinox for an observer at the equator, the Sun will pass directly overhead. Now the task is to relate the celestial position of the Sun to a local coordinate system defined for an observer’s position on the Earth’s surface. The local meridional plane is defined by three points: due south, due north, and the zenith. The meridional plane runs through the Earth’s axis of rotation and is perpendicular to the local east–west axis and is the plane defining the local longitude of the site. As the celestial sphere rotates around the Earth, the time during the rotation when the local meridional plane bisects the Sun is called solar noon and is the moment when the Sun has an hour angle value of zero. Solar hour angle uses time units to measure how much time the Sun is from reaching solar noon or how much time the Sun is past solar noon. As mentioned earlier, the celestial sphere rotates at about 15°/h, and an hour angle of 1 hour represents a rotation of 15 degrees. The hour angle is positive after solar noon and negative before solar noon. In Figure 2.4, it will take about 2 hours for the celestial sphere to rotate before the Sun is at solar noon or equivalently reaches the local meridian. The hour angle of the Sun in Figure 2.4 is, therefore, approximately –2 hours (see Equation 2.9 for computing solar hour angle values).
Long-Term Uncertainty of Renewable Energy Generation
Published in Ning Zhang, Chongqing Kang, Ershun Du, Yi Wang, Analytics and Optimization for Renewable Energy Integration, 2019
Ning Zhang, Chongqing Kang, Ershun Du, Yi Wang
Hour angle is a quantity used to measure the position of the sun relative to a certain place on Earth within one day. If the time is not calculated according to the local time but is calculated according to the standard time, the main factor affecting the hour angle of the area is the local longitude. Using Beijing time (GMT+8) as an example, the hour angle can be calculated by the following formula: () ω=t-12×15°+ψ-120°.
Optimal tilt angle and orientation for solar photovoltaic arrays: case of Settat city in Morocco
Published in International Journal of Ambient Energy, 2020
Mohamed Nfaoui, Khalil El-Hami
The hour angle AH is calculated by the daily rotation of the earth around its axis. It is the measure of the arc of the solar trajectory between the sun and the meridian surface of the place defined by (Oudrane et al. 2017): where TSV is the local solar time corrected for the time equation, a universal astronomical datum related to the eccentricity of the earth’s orbit around the sun.
An investigation of double-glass-covered trapezoidal salt-gradient solar pond coupled with reflector
Published in International Journal of Green Energy, 2018
The hour angle () is defined as the angular displacement of the sun east or west of the local meridian due to rotation of the earth on its axis at 15° per hour and by convention it is negative in the morning and positive in the afternoon (Duffie and Beckman 1991). Thus, hour angle in degrees can be calculated as
Determination of optimum tilt angle of the solar collector and evaluation of the position of the existing buildings in terms of solar potential
Published in Architectural Engineering and Design Management, 2022
Seyfi Şevik, Abdülkadir Koçer, Hüseyin İnce, Fazlı Engin Tombuş
Hour angle () is the angle between the longitude of the point considered on the Earth and the longitude indicated by the sun rays, the line joining the sun to the center of the Earth. Sun elevation angle (y) is the angle the sun rays make with the horizontal plane. z + y = 90°. Sun elevation angle;