Passive solar design is based on utilizing the sun’s heat energy and its predictable movements through the seasons.
As the Earth rotates around the sun on its annual cycle, it is tilted at an angle on its vertical axis. This impacts how the sun’s rays strike various locations on Earth. The Earth is its most extreme tilt at the winter and summer solstices.
The sun appears to rise in the east and it sets in the west. In actuality, the Earth is rotating on its axis and around the sun.
Here is a diagram that compare the sun’s path on the winter and summer solstices.
This affects how low or high the sun appears in relation to the horizon.
In the winter, the sun is relatively low in the sky with its lowest arc through the sky on the winter solstice, on December 21st.
In the summer, the sun travels a high path through the sky and is at its highest angle on the summer solstice, on June 21st.
The equinox falls on the point between the solstices and indicates the arrival of spring or fall.
This picture shows the sun’s path throughout the year. The highest arc represents the sun’s path on the summer solstice, while the shortest, lowest arc is the sun’s path on the winter solstice.
On each equinox, the sun travels a path that is right in the middle of the path that it travels on the solstices.
March 21st – Vernal Equinox
June 21st – Summer Solstice (highest path)
Sept 21st – Autumnal Equinox
Dec 21st – Winter Solstice (lowest path)
Passive solar design uses the predictable movements of the sun to best utilize its energy within the building’s overall design both for heating and cooling purposes. Many passive solar buildings also include active solar aspects, such as photovoltaic panels, as shown on the roof in the first diagram located at the top of this post.
Maybe I went into too much detail in my last comment. I’ll try to make it simpler.
The diagram contains an error. Yes, the noontime sun for the June and December solstices are probably in about the right place, for somewhere in mid-north latitudes.
But the circles showing the paths of the Sun across the sky should be parallel. The June path needs to rise and set farther north than it does in the diagram. The December path needs to rise and set farther south. They should be traveling both at the same angle relative to the ground.
Which region is this because in southern Africa the winter sun leans more to north than south
You’re correct. Southern Africa is in the southern hemisphere, so if in Southern Africa, you’d face the north to get the winter sun. Here’s another article about building in the southern hemisphere, in New Zealand.
House built in the Solar Decathlon from Team New Zealand and another one built in New Zealand.
Take it from a NABCEP Certified PV Installer. The ideal angle of tilt on a fixed tilt array, to maximize annual production should be equal to your latitude on the earth. For example I’m from Columbia, SC and it lies at 32.8 degrees roughly. So the PV arrays in Columbia (when possible) are tilted at 32.8 degrees. Let’s not forget about azimuth, the closer your array is to 180 degrees south, the better your annual production will be.
Every thing from streetlights and the way cities light up at night this type of harnessing is what I see for the future some people who are visual find it easy to help our economy and help our future with the suns rays and eventually all energy
I believe the diagram is mistaken in one detail. The circle that is the path of the sun will indeed be farthest north on June 21 and farthest south on December 21. But the circle itself (not where we see the sun) will always form the same angle to the (apparently, to an observer on earth) flat plain of the ground. To put it another way, the two circles, and all circles in between will be parallel to each other.
By the way, one might have added another circle. That would be half way between the two already there (and parallel to them both, if the two give were shown correctly). They would cross the horizon exactly east and west. That would show the path on both March 20 and September 20, the beginning of (northern) spring and fall, respectively.
And… I just read the linked article. Never mind, that has what I am looking for.
Thanks for the link.
Oh, sorry. Louisville Ky.
Where we are the summer solstice angle of the sun is about 75 degrees from horizontal. Our cloud cover is less in summer than the other seasons. The panels will be fixed, unfortunately. (Funny how a plant’s leaves will move to maxamize sun-catching for free).
I would think I would want them at somewhere between 60 and 70 degrees?
What is the ideal angle to have solar panels in Louisville to maximize their efficiency?
Seems to me it would be at wherever the sun is around noon at a month from the summer solstice?
Michael, not sure which Louisville you are located in, but because the globe is a big place, depending on longitude and latitude, the precise ideal angle will differ. The ideal angle for solar panels will also change through the seasons.
Here’s a resource that might be able to help you: http://www.solarpaneltilt.com/
THANKS , IT WAS VERY USEFUL .
We are loosing the safe distance from the sun gradually.
Very, very, very slowly… but in the meantime, why not harness its power? 🙂