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Sun angle math

Calculating your sun
angleOne of the reasons I'm plugging along with Will Hooker's permaculture videos even though I know most of the information is that I want to fill in any obvious gaps in my scattered, homeschooled education.  So I was thrilled to have sun angles finally explained to me in a manner I could understand in lecture 6.

I've posted previously about the science behind sun angles, but the math has always eluded me.  Luckily, Hooker broke it down into simple arithmetic.  All you have to do to find the height of the sun above the horizon at the equinoxes is to subtract your latitude from 90 degrees --- so, the equinox sun is 54 degrees above the horizon at a latitude of 36 degrees.  Since the sun angle at the equinox splits the difference between summer and winter sun angles, people often use this figure to calculate the tilt of their solar panels.  If you want to have the sun's rays striking a solar panel perpendicularly at the equinox, just tilt the panel the same number of degrees as your latitude --- 36.8 degrees here.  If you want a bit more efficiency from your panels in the winter, tilt the panel a bit steeper; for a bit more energy in the summer, tilt the panel more shallowly.

Sun angle and overhang depthIn order to figure out the sun angle at the summer and winter solstice, you need to understand that the earth is tilted at an angle of 23.5 degrees.  (This is what gives us seasons.)  At the summer solstice, you add the earth's tilt to the equinox's angle --- so Will Hooker's sun angle at the summer solstice is 77.5 degrees (and ours is 76.7).  At the winter solstice, you subtract the tilt of the earth, so for us the sun angle at the winter solstice is 29.7 degrees.  These two sun angles are what you need to determine overhang depths for passive-solar structures.

This information is just what we needed as we plan more energy-saving trailer retrofits!

Permaculture Chicken: Pasture Basics walks you through rotational grazing from a chicken's perspective.

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