HOW TO CHART THE SUN’S MOTION IN RELATION TO YOUR HOMESTEAD


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Categories: Education

Learn to track the sun before you design your home to determine the best orientation for it, as well as how to take advantage of the sun rays, because the position is also important for the passive cooling and heating of the house.

Understanding the sun’s motion relative to a site is an important aspect of a good permaculture design, as various elements like plants, animals and solar devices depend on sun for their functionality. A good appreciation of the earth’s rotation about its axis, its revolution around the sun and the consequences of these motions on the sun’s position and availability at a given location on the earth’s surface, is essential for maximizing plant productivity, harnessing maximum energy, minimizing energy usage and maintaining a comfortable indoor environment for humans and animals alike.

For proper functioning and productivity gardens, greenhouses and orchards should be placed at specific locations based on the adequate availability of sunshine for the parts of the year in which the plants are growing or fruiting. Other elements of a permaculture design like solar panels are also needed to be placed thoughtfully to obtain maximum exposure to the sun to harvest as much energy as possible. Houses outside the tropics need to be designed/oriented to make more winter sunlight enter the living spaces, while for those in the tropics, they should be designed/oriented to have more shade and cooler air entering the living spaces. Even animals can derive benefits from thoughtful solar designs, as they too like to have winter warmth and summer shade. Beehives, chickens, fish ponds and livestock, all appreciate sunshine in winter and shade in summer.

For a given site, if we can create a chart that shows the areas of year round shade and year round sunshine, one can plan and design the various elements for optimal functioning. Meaning, we need to chart the sun’s position throughout the year. But how to find the sun motion relative to a site?

Let’s begin by trying to understand the earth’s rotation about its axis, its orbit around the sun and the four seasons.

THE FOUR SEASONS

We all know that summers are hotter and winters are colder. Also, when it is summer in the northern hemisphere, it is winter in the southern hemisphere. But why is that?

The summers are hotter because, the sun’s path is higher in the sky. This makes the days longer and it makes the summer sun more intense. To understand it more clearly, let’s do a simple demonstration using a flash light.

In a darkened room, switch on the flash light on a surface, at a direct 90° degree angle. Make note of the size of the lit area. Now, slowly reduce the angle to make it less direct. You will now observe that the size of the lit area has increased, but the intensity or brightness of it has reduced. What it implies is that, direct 90° degree angle provides more intense light than the inclined one. The same thing happens with the sun. Higher it is in the sky, the more direct and intense the sunlight would be.

Now, this brings us to the next question – why is the sun higher in the sky in summer? The answer lies in the earth’s rotation about its tilted axis and it orbit around the sun. The earth rotates about its own axis, titled at an angle of 23.5° degrees to its orbital plane and at the same time, travels around the sun in a huge circular path through space.

During summer, the North Pole is tilted towards the sun. As a consequence, the sun’s path is higher in the sky, causing the northern hemisphere to receive more light and heat. Around June 21st, the northern hemisphere is tilted the most towards the sun and is called as the Summer Solstice. On this day, which can be referred as the first day of summer, the sun’s path is higher in the sky than it is on any other day in the year. In addition, because the sun is in the sky for more hours, the summer solstice is also the longest day in the year. These extra hours of sunlight gives the sun more time to heat the earth and this is the main reason for summer to be the hottest season.

As the earth continues its orbit around the sun, it reaches a point where its tilt is sideways to the sun. This is called as the Autumnal Equinox, where both the day and the night are of equal length with 12 hours each.

Continuing further in its orbital path around the sun, the earth reaches the other side of the sun, with the northern hemisphere tilted farthest away from the sun. Now, the sun’s path is lower in the sky, causing the northern hemisphere to receive less light and heat. This makes the days shorter and colder. The shortest day in this period is called the Winter Solstice.

As the earth revolves back towards the summer, it passes through another point where the axis is tilted sideways to the sun. Once again, day and night are of the same length. This day is called as the Vernal Equinox.

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