In ancient times man attributed the movement of the sun to various gods and deities, however today we know that the movement of the sun is the result of orbital motion of the earth, and not gods riding their flaming chariots in the sky.
In this article I am going to explain two basic concepts:
– The sun changes its position relative to the time of the day.
– The position is influenced by the time of the year.
How the position of the sun changes during the day
Ancient man has long been aware of the fact that the sun changes its position depending on the time of the day. Some speculate that the Stonehenge were build to align with the sun at certain times in the year.
The Egyptian people knew long ago that the sun is a reliable way of telling time, the three Cleopatra’s needles from Paris, New York and London originate from the Egyptian city of Heliopolis, which means “Town Of The Sun” in ancient greek. You can examine the sun movement throughout the day fairly easily, for example take a stick and position it into the ground in a open area. You will realize that as the sun changes its position, the shadow from the stick changes too.
In the morning the shadow from the stick will be long and thin, but in the middle of the day the shadow changes position and also it gets shorter, only to become long again at the end of the day. This effect is caused by the earths rotation around its axis, which causes the position of the sun in the sky to change relative to our location.
How the Position of the sun changes during the year
We know that the sun is slightly tilted on its axis, and that as earth rotates around the sun in a 365 days cycle, different parts of our planet will be exposed to the sun for longer or shorter periods.
That’s why days are longer in the summer, and longer in the winter.
The season the in the southern hemisphere will be the exact opposite from the one in the northern hemisphere at any time.
What does this mean for your in practice?
It means that you will need to change the position of your solar devices depending on your location so you can harness the most solar energy during the year.
Rules for positioning
You need to pay attention to the site you will be developing on. Observe how objects and plots cast shadows in your area.
See where your home overshadows and where it doesn’t during the year (seasonal variation). Keep in mind that if an area is shadowed for a period in the year, that doesn’t mean that it will be shaded for all seasons.
Trees can be used in your favor. If they are deciduous, they will be covered in leaves in the summer, and will be bare during the winter. You can use them as automatic sunshade, in the summer their covering of leaves blocks sunshade, but in the winter they are bare and block less sun. Remember to keep a record of your observations, drawings are very helpful too, keep notes of anything interesting at various times during the day, what areas are shadowed and those that aren’t. Be on the lookout on the longest and shortest days of the year, the first days of summer and winter. These days represent extremes of what your observations will be. Think about when are you using your solar devices during the day.
Is it a photovoltaic cell that you will be using for charging all day, or a solar cooker that you will use in the afternoon? Think about when you will be using them and how much sunlight is available in various plots of your site. Try to find true north, not magnetic north. A compass will veer towards magnetic north so you need to compensate for this. It is important to know where north and south are when positioning solar devices. If you live in the northern hemisphere site elements where coolness is required are in the north, and elements of heat are in the south. Think about the qualities of morning and evening sun in your area. Elements that require cool morning sun must positioned to the EAST, and elements that require hot afternoon sun positioned to the WEST.