Solar Site Design

Page created on: 24 June 2010

Designing with the moon

Same azimuth for the sun and full moon six months apart

If you want to design a building or a site for optimum solar placement, or want to install a solar power system, you need to know if the sun will be shaded out by surrounding structures or trees in the winter months. In the winter you can simply look at the sun's position to see how high it is above the horizon. But what do you do if you are designing the site or want to install some panels in the summer. Will they still get the sun later in the year? There is a little quirk about the sun's and the full moon's path which, per chance, is the same six months apart. When you look at the full moon, you will see where the sun will be in six months. Before you ask, I don't know if this applies to the southern hemisphere, though I think it probably does. In any case, it only applies to the full moon.

There is more information on finding the sun's position by the moon for other times, albeit a little more complex, in this article under section 11. The emphasis in the article is on the phase of the moon, but does mention the path relative to the sun.

The above widget shows the moon phases live, so do check back whenever you want to check them. If you have your own website you can get the code for the moon phases by clicking on the link at the bottom of the above widget.

There is also a website which shows a moon phase calendar for every month of the year for the northern and southern hemisphere and gives times for the moon quarters in the northern hemisphere for GMT. Stardate.org has calendars for any day, month and year between 1951 and 2015 if you want to plan your growing according to the moon phases, or check against your journal if there is a pattern between you moods or events and the phases of the moon. Stardate also have interesting information and other astronomical data.

Sun and moon rising and setting times

Another website which has a wealth of useful data, including a calculator for sun and moon rising and setting times in your location, is the U.S. Naval Observatory website. Check out the links on the Astronomical Applications page. The calculator pages you arrive at first will be for the US. If you live anywhere else in the world, follow the links on the calculator pages after the red notice to get the chart for your location. You need to enter a latitude and longitude. You can easily find out with the calculator at satsig.net. All you have to do is drag and zoom the google map to center your location on it, and read the result below when you let go of the mouse button. Use the second set of figures which give the degrees and minutes rather than decimals. However, keep those decimal figures handy if you want to create a solar path chart (links further down).