Now that you have your handy dandy solar chart, you get to have fun with school supplies.
What you need:
A compass (can even be the inexpensive plastic camping ones)
A protractor (Yes, those fun little geometry tools you haven't used since high school)
String
Weight (the ones used for fishing work)
Permanent marker
A friend
Using your compass:
The compass will be used to calculate the azimuth angle for each object you want to plot on your graph (the tree in the front yard, the high rise apartments next door, etc.). In my case, I'll be standing at one of the two potential house sites (I'll be making a separate graph for each possible site). Once there, I will look around me to see what objects might affect sun exposure on the site. There will be a lot of graphing, let me tell you.
What you will do is stand at your site and point your compass to the object you want to graph. Set the degree dial so that the magnetic pointer is on the north/south axis (180 degrees at south end). Now, you need to know how many degrees true north/south is from magnetic north/south for your area. This website will help you figure that out. Be sure to adjust your readings accordingly. The azimuth angle will be the number of degrees east or west of south the compass is pointing. If you are like me, that sounded like jibberish. So, let me give you an example. If your compass reads 150 degrees, the azimuth angle is 30 degrees east of south because there is a 30 degree difference between 180 and 150. Make sense? If the compass number is above 180, it is however many degrees west of south.
Using your protractor:
Craft time! Attach the weight to one end of the string. The string doesn't have to be very long, just longer than the protractor. Attach the other end to the hole in the protractor. Congratulations! You just made your very own sextant. You will use your sextant to calculate the altitude of each object you want to graph. Hold the protractor semicircle down (or flat end up), so that you are able to look across the 0 to 180 line. Look across that line to the highest point of the object you are wanting to graph. This is when you need your friend. Have the friend read the angle measurement where the string rests against the protractor. In other words, if I am holding up the protractor, the weight will be pulling the string straight down. As I angle the protractor to look at the highest point of my object, that string will still be pointing straight down and will rest against the side of the protractor. Whatever measurement it is resting on will be the measurement you note.
You now have the azimuth and altitude angles for each object on your horizon. You can plot them on your graph to see how sun exposure might be affected on that site. Keep in mind that deciduous trees will lose their leaves in winter.
Happy graphing!
Saturday, July 21, 2012
Thursday, July 19, 2012
Making a Solar Map
If soil testing weren't enough of a good time, I am also preparing to create a solar map for the two potential building sites on the property I am attempting to purchase. What is a solar map, you say? A solar map is an important tool for anyone planning to use solar design in their building project. It can also be informative for people purchasing an existing home or for people interested in determining the feasibility of passive solar "fixes" in their existing homestead. It is also important for people trying to determine the best place on their property for a garden. There are all kinds of uses for a solar map. It is also tons of nerdy fun.
The solar map provides two very important pieces of information. First, it lets you know where the sun is in the sky at different times of day on different days of the year. It also tells you what and when different features in the landscape obstruct the sun from the area on which you are focusing. I learned about solar mapping by reading Building Green (2009) by Clarke Snell and Tim Callahan. This book is highly recommended for anyone interested in eco-friendly methods of building.
The first step in the process is creating your own graph for the mapping. If you are going to do it manually, you will need some graph paper. The horizontal axis will represent the east to west orientation (azimuth). The vertical axis will represent altitude. Intervals will be marked at 20 degrees. On this graph, you will mark the azimuth and altitude of the sun as it passes through the sky each hour on at least the summer and winter solstices. Now, don't freak out. You don't have to be a math or astronomy wizard for this. You just need Internet access.
This website will provide you with an altitude/azimuth table for your location. You just need to Google your latitude and longitude using your zip code. Below is an example table:
This concludes Part I of Solar Mapping. We'll address mapping of landscape features another time.
The solar map provides two very important pieces of information. First, it lets you know where the sun is in the sky at different times of day on different days of the year. It also tells you what and when different features in the landscape obstruct the sun from the area on which you are focusing. I learned about solar mapping by reading Building Green (2009) by Clarke Snell and Tim Callahan. This book is highly recommended for anyone interested in eco-friendly methods of building.
The first step in the process is creating your own graph for the mapping. If you are going to do it manually, you will need some graph paper. The horizontal axis will represent the east to west orientation (azimuth). The vertical axis will represent altitude. Intervals will be marked at 20 degrees. On this graph, you will mark the azimuth and altitude of the sun as it passes through the sky each hour on at least the summer and winter solstices. Now, don't freak out. You don't have to be a math or astronomy wizard for this. You just need Internet access.
This website will provide you with an altitude/azimuth table for your location. You just need to Google your latitude and longitude using your zip code. Below is an example table:
Astronomical
Applications Dept.
U.S. Naval Observatory
Washington, DC 20392-5420
NASHVILLE, INDIANA o ,
o ,
W 86 15, N39 13
Altitude and Azimuth of the Sun Jun 21, 2012
Eastern Standard Time
Altitude Azimuth
h m o o
05:00 -3.9 55.2
06:00 6.3 64.6
07:00 17.0 73.3
08:00 28.3 81.8
09:00 39.9 90.8
10:00 51.5 101.5
11:00 62.4 117.0
12:00 71.4 144.3
13:00 74.0 190.9
14:00 67.9 229.8
15:00 57.8 250.6
16:00 46.5 263.5
17:00 34.9 273.3
18:00 23.4 281.9
19:00 12.3 290.4
20:00 2.0 299.3
21:00 -8.0 309.2
Astronomical Applications Dept.
h m o o
08:00 -1.0 119.9
09:00 8.6 129.9
10:00 16.7 141.2
11:00 22.9 154.3
12:00 26.6 168.9
13:00 27.3 184.3
14:00 24.9 199.4
15:00 19.7 213.1
16:00 12.4 225.3
17:00 3.6 235.8
18:00 -6.7 245.1
Once you have this information, you can start plotting it on your graph.
If you are as lazy as I am, you can let an online calculator do it for you. Here are some online resources for that:
http://www.builditsolar.com/References/SunChartRS.htm
http://solardat.uoregon.edu/SunChartProgram.html
When all is said and done, you should have something that looks similar to this:
This concludes Part I of Solar Mapping. We'll address mapping of landscape features another time.
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