About This Program

This Freeware program was written to help you design solar collector projects using Parabolic Reflectors. This program calculates the focal length and (x, y) coordinates for a Parabola of any diameter and depth. It can help you determine what size and shape to make your parabola very quickly.

If you would like modifications to the program to make it more useful to you, email me with as many details as possible. Please send bug reports, suggestions or feedback here. I appreciate hearing all of your comments.

Thanks to Bernhard S. Müller for beta testing the program.

Download the Program

This program was written in Visual Basic 6, and should run on Window 95 or later. It requires the Visual Basic 6 Runtime files, your computer may already have them installed. I would try downloading the smaller file first and seeing if it runs. If not, delete it and download the full Windows Installation Package. This will do a standard Window Installation of this program on your computer.

• Download Parabola.exe (69 kB)
    (does not include Visual Basic Runtime Files.)
• Download Windows Installer (1.45 MB)
    (unzip to any folder, run Setup.exe to install all necessary files.)
  VISTA USERS: One user reported that the installer froze his Vista machine - so please try running the Parabola.exe first, before trying the installer.
• Download VB6 Source Code (76 kB)

Links

SolarTechnik.com
La Cuisson Solaire

Program Notes

1.When you run the program you will see the main program window shown here. Use any units you like, as long as you use the same units for both the Depth and Diameter. I recommend using smaller units, e.g. inches instead of feet, centimeters instead of meters, to increase the resolution of your measurements.

2. After you enter some numbers into the Diameter and Depth text boxes and click the Calculate button, the program will show you the scaled down shape of the parabola you described, and it will calculate the (x, y) coordinates of the curve of the parabola in 16 straight line segments. I made the program default to 16 because I thought this would result in a decent reflection efficiency, while still being simple to make using a jig saw. But you can calculate the (x, y) coordinates using anywhere from 2 to 1000 segments (as you probably suspect, using only two segments would result in a very poor reflection efficiency).;

3. To see what the shape and focal length would look like the depth is increased to 18, hold down the horizontal scroll bar next to the text box and watch the parabola's shape change. To simplify the construction try reducing the number of straight line segments to 6. As you can see, now there are only 3 straight line segments making up each half of the parabola. This makes it very simple to build, although it will reduce the efficiency somewhat. There is a tradeoff between the parabola's efficiency as a reflector and ease of construction. The less straight-line segments used, the easier it will be to build, but the less efficient it will be. I would recommend using as many straight-line segments in the construction of your solar collector as you can handle building into it.

4. If you click the Save to File button, the program will prompt you to select a folder and enter a filename, and then it writes a file with the information you see in the text box on the right (above). Here's how the saved file looks when it is opened using Windows Notepad (using the Courier New font). The filename is as you see here: "Parabola Diameter 36 Depth 18.txt" , the program will automatically suggest a name that includes depth and diameter so when you're looking through your files later, it's easy to locate. You can enter any filename you like.

5. If you'd like to see the coefficients of the Equation that describes the current Parabola, use the menu choice: File > View the Coefficients. You will see a message box like this one showing you the values used in the parabola equation:

6. If you move your cursor over the image of the parabola, you will see the individual points calculated by the program: the (x, y) coordinates are shown at the bottom of the display. The point (horizontally) closest to the mouse cursor will be shown, you can see the location of each point listed in the text box.

7. If you want to know the length of material needed in a flat sheet to be able to cut out all of the pieces of your parabola, the program adds the lengths of each straight line segment and displays this in the menu and in the text box. In the text box this is called the "Linear Diam". The menu choice, and message box look like this:

8. If you'd like to see some interesting Web Sites about Solar Collectors and Solar Cooking Projects, or about the math behind Parabolas, click the menu choice: File > Parabola and Solar Project Websites. Click on a website and it will load into your default web browser automatically. Click the Hide button to view the main program form again when you're finished with the web sites. A collection of these links can be found here.