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Visualize Shadows

 

The visualization of shadows itself is the most intuitive method of the error-proof of your solar project. This basic option is available in all our "solar" products Shadow Visualizer, Shadow Calculator, and Shadow Analyzer.

 

Considering the scene day by day for different seasons of the year, you can determine the origin of the collector shading and the time boundaries when it occurs. It helps also to interpret the numerical data of the "solar" windows of Shadow Calculator and Shadow Analyzer, because the shading characteristics become more evident after you compare them with the shadow images of the 3D View window.

 

Use Shadow Visualizer, Shadow Calculator, and Shadow Analyzer to error-proof your solar project:

 

 

 

 

 

Before to start your first session with the real architecture environment and the particular configuration of your solar project, it is useful to consider some example scenes that you can find in the folder "Examples". To find the location of this folder on your PC, you can use the command "Folder Architecture" of the File menu.

 

Understand the Solar Path on the sky

 

To train your intuition and your 3D imagination, consider the example scenes with the file names "s740_SkySphere..." that you can see on the following screen shot.

 

 

Use the keyboard to observe quickly the Sun path for the entire year. For this purpose, press the key "4" of your keyboard (to switch to the Mode "4" -- "Month/Time"), and then use the LEFT / RIGHT and UP / DOWN arrow keys.

 

Note that we use the specific time system that passes just to the solar energy calculations. Namely, we count time from the true solar noon, when the Sun crosses the plane of your local meridian. So 12:00 on all the screen shots corresponds to true solar noon.

 

If you want to use this model with the latitude of your particular site, do the following. Open any one of the scenes "s740...". Save it under another file name. Change the scene latitude using the leftmost Spin control of the toolbar 3D View. Note that you need to set the negative value of the latitude, if your site is located in the Southern Hemisphere. Then, select the object 5 "Sky Sphere". Open the combo box CS of the toolbar Location. Select the second Euler angle E2, and set its value so that E2 = Latitude - 90, like it is shown on the next screen shot.   

 

 

Observing this model of the sky sphere for different seasons, you see that the Sun path during any day (as it is visible from your site) is an arc that is parallel to the Equator plane (object 9), and is situated between two conical boundaries: object 6 "June 22" and object 7 "Dec 22". The angle between each conical surface and the Equator plane is equal to 23.45 degree. It is just the angle between the axis of the Earth own spinning and the normal to the plane of the Earth orbit (Earth revolution) around the Sun. 

 

You can compare the scenes shown above with the Sun path diagrams for Stuttgart, Germany (latitude 4846' N) that we obtained from the Satellight website "The European Database of Daylight and Solar Radiation" 

http://www.satellight.com/ 

 

 

 

 

These diagrams use the true solar time units (hours from midnight). At 12:00 solar time, the Sun is exactly south.

 

A typical session

 

This is the screen shot of a typical session with Shadow Visualizer. We hid some toolbars to simplify the picture. Two toolbars are shown: Toolbar Show and Toolbar 3D View. 

 

 

You see the scene "s823   " in two 3D View windows. You can open a new 3D view window of the same scene using the command "New Window" of the "Window" menu. Then, you can manage the view parameters (like Date, Time, the vintage point, etc.) of each active 3D view independently from other 3D views. In this way, you can visually compare the shading of your collectors in different days and seasons. 

 

On the screen shot above, the right 3D View window is active (its title bar is highlighted). So all the control elements correspond now to this active view. You see the Date and Time of this view in the second and the third indicators of the Status bar. If you check the button "inf" of the toolbar 3D View (just when a particular view is active), then the Date and Time will be visible as the yellow text line inside the 3D view, even when the view window is inactive. We did it for both the 3D views.

 

Use the keyboard to observe quickly the shading of your collector system for the entire year. For this purpose, press the key "4" of your keyboard (to switch to the Mode "4" -- "Month/Time"), and then use the LEFT / RIGHT and UP / DOWN arrow keys. 

 

Check the button "View from Sun" of the toolbar 3D View (or press the key "9") and uncheck the button "PJ" of the toolbar Show, to see how other objects block the path of the solar beam radiation to your collectors. These settings correspond to the Mode "9" -- "Looking from Sun", and to the orthographic projection of the 3D view. So you will see not the shadows themselves (as in the left window of the screen shot), but just the objects that cast shadows on your collectors (as in the right window of the screen shot). In this mode, you see the collectors always from the Sun side, because the vintage point is changing automatically when you use the arrow keys, as if you (as an observer) are moving together with the Sun.      

 

The following fragments of the topic User Interface remind you the sense of some control elements and options of the user interface that you can use for the shadow visualization.

 

Use the Status bar

 

See the status bar at the bottom of the main window. It consists of the status line and five indicators.

 

The status line displays hints for all the control elements. Move the mouse pointer to a control element like a button or a Spin control, and read its descriptions in the status line. In particular, you see the description of the button "View from Sun" on the screen shot above.

 

Five indicators at the right side of the Status bar display:

 

 

Note that in addition to true solar time that is displayed in the Status bar, you can see both the true solar time and your local clock time in the 3D View window if you check the button "inf" of the toolbar 3D View. See below how to set your latitude and GMT zone with the command "Set Geography..." of the Edit menu.

 

Use the toolbar 3D View

 

In Shadow Visualizer and Shadow Analyzer, the X, Y, and Z axes of the coordinate system of the scene are looking to the East, North, and Zenith, respectively. The azimuth is counted clockwise from the North, so that the azimuth values of the East, South, and West are 90, 180, and 270 degrees, respectively.

 

The toolbar 3D View manages the parameters of the active 3D view window. However, you can hide it and use the keyboard, as it is described in the next point below.

 

In Shadow Visualizer and Shadow Analyzer, you manage the Sun position indirectly, setting the geographical latitude, the month, the day, and the time by first four (3 vertical and 1 horizontal) Spin controls of the 3D View toolbar.

 

The button "View from Sun" allows to switch quickly between the usual view mode and the specific view mode "Looking from Sun", where the viewpoint automatically follows the current Sun position that is calculated by the current day and time.

 

Next two Spin controls (vertical and horizontal) manage the viewpoint elevation and azimuth. These Spin controls become disabled in the view mode "Looking from Sun" (because the Sun position is calculated automatically).

 

The information button "inf" ("Sun Azimuth/Elevation") displays a short string with the values of the Sun azimuth and elevation in the left top corner of the active 3D view window. Note that in addition to true solar time that is displayed in the Status bar, you can see both the true solar time and your local clock time in the 3D view. See below how to set your latitude and GMT zone with the command "Set Geography..." of the Edit menu.

 

The button "##" ("Object Numbers") marks all objects in the active 3D view window by their numbers in the scene. If an object is a parent of other ones, then its number is prefixed by the underscore "_". The numbers of the corresponding parent objects are shown in parentheses (without the underscore).

 

The Spin control "Zoom In/Out" changes the zoom factor value. You can also use the keyboard keys "PAGE UP" / "PAGE DOWN" or the wheel of your Wheel mouse. 

 

"Set Geography..." command

 

Note that you can use Shadow Visualizer and Shadow Analyzer not only for the visualization and analysis of your solar collector system, but also for many other tasks that are somehow associated with the solar radiation or solar light in architecture, solar design, and even in your everyday practical life.

 

Usually, we use true solar time as more natural units for our solar calculations. However, the local clock time can be more convenient in the everyday life. Therefore in addition to true solar time that is displayed in the Stratus bar, we display both the true solar time and your local clock time in the 3D View window. To see this information, check the button "inf" of the toolbar 3D View.

 

Before to use clock time, you need to set the longitude and the GMT zone of your site with the command "Set Geography..." of the Edit menu that calls the following dialog.

 

 

The dialog contains three Edit boxes, two Check boxes, and one Combo box.

 

Use first two Edit boxes to set the longitude and the latitude of your site. The longitude and latitude settings that you see on the dialog image correspond to the geographical location of Almeria (Spain). Note that the longitude of Almeria is 2.4 degrees West. Therefore we use the sign 'minus' to set the longitude. Also use the sign 'minus' for the latitudes of sites located in the Southern Hemisphere. Note that you can change the latitude also with the "Latitude" Spin control of the toolbar 3D View. The difference is that the Spin control change the latitude with the step of 1 degree, while the dialog allows you to set both longitude and latitude with the accuracy of 0.1 degree.

 

The first Check box that follows the longitude and latitude Edit boxes allows you to lock the latitude settings so that the "Latitude" Spin control of the toolbar 3D View will be disabled. It helps you not to change the latitude occasionally, when you are working long time with a particular scene. Once the latitude is locked, it can be changed next time only with the Geography dialog.

 

The third Edit box allows you to set your Time Zone. The GMT zone means how your local clock time in winter differs from the "Greenwich Mean Time". To know this difference compare your clock time with the time of London (UK). Deduct the London time from your local clock time, and put the difference into the Edit box.

 

The second Check box allows you to apply the Summer time if it is used in your country. In some countries, for energy saving purposes, one hour is added to clock time from the last Sunday of March, to the Saturday before the last Sunday of October. This is called daylight saving time or summer clock time, as opposed to winter clock time outside of that period.

 

Due to the changing of the week days from year to year, the beginning (and consequently the end) of the Summer time period varies within a week. If you need to set precisely the beginning of the Summer time period for a particular year, use the Combo box of the dialog to set the date of the last Sunday of March for that year (the default value is March 28). The end of the Summer time period will be calculated automatically. 

 

Use the following links to the Glossary of "The European Database of Daylight and Solar Radiation" and Wikipedia to read more about the true solar time, "Greenwich Mean Time", and the "Equation of time":

http://www.satellight.com/indexgG.htm 

http://en.wikipedia.org/wiki/Greenwich_Mean_Time 

http://en.wikipedia.org/wiki/Equation_of_time 

 

Note that although the definitions in these publications differ in some details of "astronomical" accuracy (the Wikipedia definitions are more rigorous), they are equivalent for our practical purposes. We use the definition of true solar time according to the Glossary of "The European Database of Daylight and Solar Radiation".

 

You can see how all this works on the following screen shot.

 

 

You see two example scenes "s611_Tent_Almeria.sa1" and "s611_Tent_Bari.sa1" of the same configuration that model a small open summer restaurant under a light roof or a tent. The geography settings of the scenes correspond to Almeria (Spain) and Bari (Italy). Both the locations belong to the same time zone GMT+1, but differ in longitude by 19.3 degrees.

 

The top views show the scenes before the Summer time period, for the same day March 21, at 12:00 solar time. In the contrast, the bottom views shows the scenes within the Summer time period, for August 15, at approximately the same clock time near the clock time noon (at 12:04 and 12:07 correspondingly).

 

You can use this technique in many real life situations to predict (if it is important or desirable) when and where the shadows casted by different objects will appear. For example, you can do it planning your solarium, a sunroom, or a terrace in your house, or choosing the best time to make impressive professional photographs of a rocky landscape, or even merely adjusting the tent above the table in your garden.

 

Use the keyboard modes

 

Here we again add a fragment of the topic User Interface to remind you the sense of some control elements and options of the user interface that you can use for the shadow visualization.

 

You can use the same arrow keys (LEFT, RIGHT, UP, and DOWN) of your keyboard for different purposes switching between several modes by number-keys with numbers "1", "2", "3", "4", "9", and "0", or by the "space bar"-key. 

 

 

Mode "0" is the "Default viewpoint" mode (same as mode "3", but in addition returns the viewpoint to its default position).

 

Firstly, select a mode by a number-key, then use LEFT / RIGHT and UP / DOWN arrow keys.

 

In the "Geographical latitude" mode (1), you can increase / decrease geographical latitude by UP / DOWN arrow keys. The value of the latitude is shown in the first indicator of the Status bar. Note that this setting is applied to the entire scene and affects all its views. Usually, you use it only once, when you create the architecture environment of your scene. The LEFT / RIGHT arrow keys do not work in this mode.

 

In the "Date/Time" mode (2), you can decrease / increase the Date (day by day) by UP / DOWN arrow keys. Or you can decrease / increase time by LEFT / RIGHT arrow keys. Date is shown in the second indicator, and Time is shown in the third indicator of the Status bar.

 

In the "Viewpoint" mode (3), you can move your viewpoint to the left, to the right, up, and down by LEFT / RIGHT and UP / DOWN arrow keys. The scene in the active 3D view will rotate, as if you are running around the scene. 

 

In the "Month/Time" mode (4), you manage the view as you do in the mode "2", but the UP / DOWN arrow keys change the date month by month, while the day is always the 15th day of the month.

 

The "Looking from Sun" mode (9)  is designed specifically for the visual analysis of solar collector systems (especially for the sun-tracking collectors). The arrow keys in this mode act as in mode "2" or "4" (depending on which mode was the latest) -- they change the date (day by day or month by month) and the time of the 3D view. But the viewpoint also moves following the current Sun position -- as if we are looking from the Sun, along the direction of solar beams. Note, if in addition we switch the projection from "perspective" to "orthographic" (using the button "PJ"), the shadows become unseen, being blocked by visible surfaces of the nearest to us objects.

 

Use the "0"-key to switch the 3D view to the "Viewpoint" mode and return the viewpoint to its default position.

 

Use the "space bar"-key to switch the 3D view quickly between the "Viewpoint" mode (3) and the latest one of the "Date/Time" mode (2) or the "Month/Time" mode (4). It is the most often switch, when you are working with scenes, so this function of the "space bar"-key is duplicated also by the "Insert"-key at the bottom of the numeric pad.

 

Simplify your scene if it is needed

 

This point concerns Shadow Calculator and Shadow Analyzer. We discussed the theme of the scene complexity in the topic Create Architecture of this chapter. If you feel that your scene works slowly with the "solar" windows, you can use the results of the shadow visualization to simplify the scene removing the objects that definitely do not cast shadows on your solar collectors in any time of the year.

 

See the following screen shot. After the visual analysis of the scene "s823_Static_PV_on_Roof.sa1" for the entire year, you can make sure that some objects never take part in the shading of the collector system. So the scene can be reduced to the very simple scene "s823_Static_PV_Shadowers.sa1" to speed up the shadow calculations for the "solar" windows. The initial scene consists of 34 objects with 445 polygonal faces, while the final scene has only 21 objects with 264 faces.

 

 

This is only an illustration of the idea of the scene simplification, because actually both the scenes are enough simple, and work enough fast with the "solar" windows on any contemporary PC. The difference become more contrast if the initial scene is really complex and contains thousands polygonal faces. If it is the case, the simplification is necessary.