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Calculating the solar irradiance
Published in David Thorpe, Passive Solar Architecture Pocket Reference, 2018
Sun path diagrams are an important tool to understand how much solar gain there will be at different times of day throughout the year. They are used to evaluate the solar altitude and azimuth angles for a given latitude, longitude, time of year and time of day. Sun path diagrams represent a horizontal or vertical projection of the imaginary sky dome placed over a building site. These may graphically assess solar exposure of a reference point (e.g. a building or a part of a building) throughout a year. In a sky dome, the horizontal lines represent altitude and the vertical lines represent the azimuth. A vertical sun path diagram represents the projection of the sky dome on the vertical plane.
Solar Geometry
Published in Pablo La Roche, Carbon-Neutral Architectural Design, 2017
Sun path diagrams can be used to determine solar potential of a location, especially to determine comfort, the placement of photovoltaic systems, or passive gains in a solar building. Building shading on outdoor spaces has an important effect on its perception and use. If it is intended for winter use and is shaded by a neighboring building, it will probably be dark, cold, and unused; and will not be used if it is unshaded and intended for use during hot weather. Sun path diagrams and shadow masks are used to determine shade from adjacent buildings, trees, or other obstacles. The position of the obstacles is calculated by determining the azimuths and altitudes of the edges of the points and plotting them on the sun path diagrams. The area that is intersected by the path of the sun and the enclosed surface indicates when the sun is blocked by obstacles. If the surface is outside the path of the sun, this means that the sun is not blocked by obstacles at any moment. Figures 7.32 and 7.33 show the same obstacles plotted on a vertical and a horizontal sun path diagram. A tree blocks the sun during a large part of the summer morning, and during the summer it is mostly clear close to noontime. Because the position of the obstacles on the sun path diagrams are the result of geometric relationships between the point in the site and the obstacles, the position of the obstacles on the chart changes as we analyze different points. Because they indicate the times during which solar radiation will be available, these can also be used to establish performance of photovoltaic systems or direct gain systems for passive and active heating. Adjustments in building massing can then be proposed to improve shading or solar access. It is now also possible to generate these sun path diagrams with software.
Solar Collectors and Solar Thermal Energy Systems
Published in Radian Belu, Fundamentals and Source Characteristics of Renewable Energy Systems, 2019
The projection of the Sun’s path on the horizontal plane is called the sun path diagram, as the diagrams shown in Figure 3.12. Solar altitude and azimuth angles for given latitude can be conveniently represented in such graphical format, that can be used to find the position of the Sun in the sky at any time of the year. Sun path diagrams, besides of helping us to build the intuition of the Sun position during the day, have also a very practical design and operation applications in the field when trying to predict shading patterns at a specific site or location, a very important consideration for the solar energy conversion systems, which are sensitive to the shadow. The concept is simple, the solar altitude and the solar azimuth angles are function of latitude, hour angle and declination. Using only two parameters, in a two-dimensional plot, the other two parameters can be correlated. For given latitude and a given day, the solar altitude angle and the azimuth angle are function of the hour angle, therefore the solar time. By entering in a sun path diagram for given latitude with appropriate values of the declination and hour angle, the point of intersection of the corresponding lines represents the instantaneous location of the Sun. The solar altitude can then be read from the diagram circles. Usually different Sun path diagrams are plotted for different latitudes, and are showing the complete variations of the hour angles and declination for the full year. Lines of constant declination are labeled by the values of the angles, while points of constant hour angles are clearly marked. The azimuth angles are the normal compass coordinates where the South is 180°, so the azimuth angle coordinates run from 0° to 360°, and the elevation angles coordinates from 0° to 90°. Since the Sun’s path is symmetric about the summer solstice, the lines for the other year half are not included, being simply the duplicate of those of the first half of the year. The plot of sun path diagram may be shown in polar coordinates. Notice that the diagrams of Figure 3.11 are referring to the Northern Hemisphere, while for the Southern Hemisphere the declination angles’ signs are reversed.
Explorations and estimations using Google Maps images
Published in International Journal of Mathematical Education in Science and Technology, 2022
With the knowledge, the question reduces to: When is the sun in London (latitude ) at an altitude of 36° and simultaneously at an azimuth of 10° in the east? The daily sun path in the sky depends on the so-called declination of the sun, which varies between −23.5° and +23.5° in the course of one year. The possible values of the declination occur generally twice a year (except both the boundary values at the beginning of summer on 21 June and at the beginning of winter on 21 December); thus, it is clear that every sun path has two days of realization in the course of a year. That means actually: If one fixes one point in the sky (in the area in which the sun can be in principle) then the sun comes to this point two times per year. There are tables for the declination of the sun (see Table 1), between the given values one may interpolate linearly – high precision is not needed in our topic!
Experimental studies on efficiency enhancement of the parabolic solar collector combined with mirrors using the artificial neural network
Published in International Journal of Ambient Energy, 2021
Suneetha Racharla, K. Rajan, M. Rajaram Narayanan, K. R. Senthil Kumar
The main aim of the paper is to focus the PV panel towards the sun at maximum time. For this astronomical data are considered to estimate the sun path angle. Total rotation angle of the panel is 180° whereas sun light duration in one-day is 10 h. In case of the panel, the angle of rotation in 1 h is estimated as 180°/10. The angle of rotation in 30 min is calculated as 18°/2 and so the angle of rotation in 15 min becomes 4.5°. Two servo motors are used for smooth and precise movement of the system. Selected rpm of the motor depending on the overall system is 200 rev/s. Thereby the angular speed equals to 200 * 2 * ∏/60 which gives 20.94 rad/s. From this the angular acceleration is estimated to be 2.09 rad/s2. From the above values the moment of inertia and torque are calculated to be 0.49 kg m2 and 1.02 N m, respectively (Figure 5).
Comprehensive solar energy resource characterisation for an intricate Indian province
Published in International Journal of Ambient Energy, 2021
Subhadeep Bhattacharjee, Rahul Bhattacharjee
The sun path diagram is a representation of the trail of the sun across the sky from a flat surface. The sun path diagram has been used to identify the sun’s position easily and quickly in the sky at any time of the day or at any time of the year. Sun path diagram is different for every latitude. The sun path diagram is shown in the Figure 5 that shows the sun’s position on the study site for different months of the year. The azimuth angle is plotted along the x-axis while the solar elevation angle is plotted along the y-axis. The day length can easily be estimated from the graph. It is apparent from the sun’s path for December that the sun will remain in front of an observer from sunrise to sunset. The elevation angle will be at about 43° at noon of winter (December–January). During summer noon, on June, the sun will become nearly overhead, with a solar elevation of 87°, to the observer. It is evident that the sun will rise and set behind the observer (facing south) in June.