Overview: device for measuring at one time without needing clear weather, the the daily solar exposure possible at a specific place for the whole year. For placing solar panels or collectors, esp. in areas far from the equator. (South of equator, reverse month labels: December at top and June at bottom)
Construction: Copy the picture below on a transparent sheet.
Use Part A to mark up a bottom plate which is then cut in that half circle form. The bottom plate should be fastened so it will make an angle to the horizontal as determined by the latitude angle scale D. (The angle between the horizontal base and the scale bearing baseplate = 90 - latitude degrees. In picture C, the scale bearing base plate is 10 degrees up from the horizontal base for measuring at latitude 80 degrees North. I had a hinge along the straight part of A which was screwed to a horizontal base plate, with a tripod screw-hole and spirit level. A screw could be adjusted for changing the latitude adjustment.)
Drill a hole in the A plate where the siting pin mark is.
Cut out B and glue (the crosshatched ///// part) to outer edge of A (with text facing inwards. Insert a straight pin in the siting pin hole. The length should be such that the top is at the same level as the March September line on the scale. (It should also be "automatically" right between the 6 am and the 6 pm vertical lines, if the instructions thus far have been followed). Using: The surveyor is placed where the solar device is planned. (Perhaps measurements should be made in each of the planned collector's corners). If the scale bearing base plate has been fastened to a horizontal base (forming angle according to D with the scale base), that horizontal base must be level. If you have a compass the apparatus can be oriented so the "siting pin to 12 o clock line" points South. Without a compass, you can orient it if the sun is visible: you should be able to turn the apparatus (while keeping horizontal base level) so that the sun is on the correct time on the siting scale. (If you have daylight savings time the sun should be one hour less than "clock" time. E.g. if the time is 10 am daylight savings time, the sun will be at 9 am on the scale when properly oriented.)
Now you place your eye near the end of the siting pin (see illustration C) and check which things (horizon, trees, buildings) will interfere with sun. See an example of how it could look below.
I can see that, in the above picture, on Dec 22 (=the worst case in Northern hemisphere), the sun would just barely go above the horizon from about 1200 till 1230.
In March (and September), I see the sun would go up about 0700 till 1600 but that a tree would shade the position from about 1020 till 1140. For some seasons it could be good to differentiate between evergreen trees and trees that drop their leaves (in cold or dry weather). Other things to take notes on is: My tree or someone elses? (="Can I cut this tree if it gets in the way too much?") How much higher can these trees get? Any planned buildings that could get in the way? Any reflecting surfaces (water, snow) that could increase the sun energy input in some cases?
I usually make a paper copy (for each location I'll check) of the surveyor scale and sketch on it: the horizon including buildings, evergreen trees, deciduous trees, and mark other peoples trees with another color pen. A sketch could look like this:
Any questions, suggestions? Drop me a mail! Jeff Forssell
© Jeff Forssell sun-el.html Last uppdate
99-May-2
