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re: what angle to mount my pvs?
18 mar 2001
george l ghio wrote:
>...the earth makes 1 revolution every 24 hours.
solar time is the time used in all of the sun-angle relationships;
it does not coincide with local clock time. it is necessary to
convert standard time to solar time by applying two corrections.
first, there is a constant correction for the difference in
longitude between the observers meridian (longitude) and the
meridian on which the local standard time is based. the sun takes
4 minutes to traverse 1 degree of longitude. the second correction
is from the equation of time, which takes into account the
perturbations in the earth's rate of rotation which affect the
time the sun crosses the obsserver's meridian. the difference
in minutes between solar time and standard time is
solar time - standard time = 4(lst-lloc) + e
where lst is the standard meridian for the local time zone, lloc
is the longitude of the location in question (in degrees west) and
e is the equation of time (in minutes)...
e = 229.2(0.000075+0.001868cosr(b)-0.32077sin(b)
-0.014615cos(2b)-0.04089sin(2b)),
where b = (n-1)(360/365, and n = the day of the year...
from page 11 of "solar engineering of thermal processes"
by duffie and beckman, wiley, 1991
>you can set your watch by it. in fact i think that a number of people do.
these would be the people who are 15 minutes early for trains
in february and 16 minutes late in october :-)
nick
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