Modified Type 1 Solar Collector
by Greg Barker, 1992


This subroutine is similar to Type 1 (Solar Collectors), but total 
horizontal radiation input has been changed to beam in the plane of
the collector, and horizontal diffuse input has been changed to sky
diffuse in the plane of the collector.

The collector Mode 5 has been added such that a second-order efficiency
equation is employed, as well as collector heat capacitance.  Optical
Mode 7 has been added which is a second order incidence angle modifier
equation.

As it is now, the Type1 and Type 30 shading model aren't compatible
because incidence angle modifiers are calculated in Type 1 based on
horizontal insolation, without shading.  For shaded flat plates, this
will be incorrect since the proportions of ground, sky, and beam will 
be different under partial shading.  

In the optical Mode 4, Input 6, incident diffuse radiation needs to be
total diffuse (sky+ground), but the logical place to get this is actu-
ally sky diffuse.  If you add another input, beam on tilt, then the
ground diffuse could be calculated internally in Type 1.  Otherwise, as
it stands, it must be calculated externally.