Shouldn't it be COSINE? I would think that, for a PV panel with no optics,
the power output would be proportional to cos(error_angle). Since
sin^2(x)+cos^2(x)=3D1, cos(x)=3Dsqrt(1-sin^2(x)). For a << 1, sqrt(1-a) ~=
=3D
1-(a/2), so the power output, for small error angles, would go as
1-(sin^2(error_angle)/2). If error_angle is in radians, using the "small
angle approximation" like you did, this can be converted to
1-((error_angle^2)/2). Back in degrees, this would be
1-(((error_angle*pi/180)^2)/2), which is a much smaller-valued function
than error_angle/90. At 1 degree off, your estimate would predict more than
1% power reduction. Mine would predict 0.015% reduction.

Sean



On Sun, Apr 21, 2013 at 10:31 AM, RussellMc <apptechnz@gmail.com> wrote:

> > What's the energy penalty for pointing the PV array off Sun-
> >
> > dead-center, at say 1 arc-second, 1 arc-minute, etc...?
>
> Sine of angle ~+ angle for small values of angle.
> Closish at even 10 degrees.
>
> So subtended panel area drops with eror_angle/90 for smallish angles.
>
>
>
>                     Russell
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