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is maximizing the direct sunlight. However, a solar thermal panel can be as high as 80% efficient at
transmitting direct sunlight into usable energy. Because of the much higher efficiency, siting is not as
crtcal, although t s stll mportant.
You want to nstall your solar panels n a spot that receves drect sunlght from 9 a.m. to 5 p.m. on
December 21
st
. Ideally, you would also lke to nstall your collectors facng drectly south and angled
to match the lattude of your ste. It s at ths pont that many people get dscouraged. Some of the
common problems with finding an ideal location are: wrong tilt, wrong angle, and shading. I will address
each n turn.
Issue #1—Wrong tilt:
Many solar collectors nstalled n the past sought to get the perfect angle for
solar collecton by usng specal mountng hardware to nclne the collectors at the “perfect” angle. Ths
is almost entirely unnecessary. While it is true that if you tilt the collectors at exactly the same angle
as your site’s latitude you will maximize the solar radiation on the collector, the difference between
perfect and not perfect s vrtually mmeasurable. Runnng the numbers n a smulaton, I found that
for Ralegh, North Carolna (lattude 35.7
0
), f you mount the collectors between 0
0
and 60
0
the worst
performance s only 9% off of optmal. Whle the deal angle for my solar collectors s 35.7
0
, I nstalled
my solar collectors flush to the 12/12 pitch roof with roughly the same annual performance I would have
acheved had I mounted them at the “deal” angle.
The general rule states that f your collectors are mounted at an angle less than your lattude you wll
receve more heat n the summer and less n the wnter. If your collectors are mounted at an angle
greater than your lattude your wnter heat gan wll be hgher and your summer lower. That s the rule,
but as you can see from the previous example, the actual annual performance difference is small.
Issue #2—Wrong Direction:
“My house sts on my lot n such a way that the secton of roof I want to
nstall the collectors on ponts southeast or southwest or due east or due west.” Whle t s true that due
south s the optmal orentaton, a solar thermal system s pretty forgvng n ths regard as well. Your
collectors can be ponted wthn 45
0
of south and not see more than a 3.5% reducton n ther output. If
you get much beyond 45
0
off of south, I would recommend ncreasng the area of your collectors before I
would recommend anglng your collectors perfectly toward the sun. If you don’t have a compass handy,
I would suggest downloadng a copy of Google Earth
TM
free from the Internet. Wth ths software you
can get a satellte mage of your home that ncludes the compass rose. Usng ths snapshot, you wll
know the exact orientation of your home.
Pcture 1: Ths s a snapshot from Google Earth
TM
showng a street address and how that buldng sts relatve to South. As
you can see from the pcture, the street s almost due south from the buldng so any collectors should be be nstalled facng
the street.
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