RE: [EnergyPlus_Support] SOLAR COLLECTOR PARAMETERS:FLAT PLATE: Incident Angle Modifier is out of bounds

["Ellis, Peter" <peter_ellis@xxxxxxxx>]

I just wanted to follow up on this thread for the rest of the users.  As illustrated below, some coefficients for Incident Angle Modifier can be completely valid and reasonable, yet will generate an out-of-bounds error for large incident angles (~80 degrees).  Between Tobias and myself we ultimately learned that manufacturers and the testing agency (SRCC) only guarantee the coefficients for angles less than 60 degrees; it turns out that for some coefficients the curve fit can spike to infinity as you approach 90 degrees (parallel to the collector surface).  We will plan to get a fix for that into the next release.  
 
P

________________________________

From: EnergyPlus_Support@xxxxxxxxxxxxxxx on behalf of tobiasmaile
Sent: Wed 5/21/2008 12:21 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] SOLAR COLLECTOR PARAMETERS:FLAT PLATE: Incident Angle Modifier is out of bounds



Hi EnergyPlus team, 

I came along the following error message for my solar collector:

** Severe ** IAM Function: SOLAR COLLECTOR PARAMETERS:FLAT PLATE =
NOVAN SUNEARTH EC/EP32: Incident Angle Modifier is out of bounds due
to bad coefficients.
** ~~~ ** Coefficient 2 of Incident Angle Modifier =
-0.296400000000000
** ~~~ ** Coefficient 3 of Incident Angle Modifier = 
1.910000000000000E-002
** ~~~ ** Calculated Incident Angle Modifier = 19.8345404701638
** ~~~ ** Expected Incident Angle Modifier should be approximately
1.5 or less.
** Fatal ** Errors in SOLAR COLLECTOR PARAMETERS:FLAT PLATE input.

My solar collector parameters are directly out of the document that is
referenced in the engineering manual (Directory of Solar Collector
Ratings) and are as follows:

SOLAR COLLECTOR PARAMETERS:FLAT PLATE,
SunEarth EC/EP32, !- Name
3.051, !- Gross Area {m2}
WATER, !- Test Fluid
0.000046, !- Test Volumetric Flow Rate {m3/s} 
INLET, !- Test Correlation Type
0.7525, !- Coefficient 1 of Efficiency Equation
(Y-Intercept) {dimensionless}
-3.0285, !- Coefficient 2 of Efficiency Equation
(1st Order) {W/m2-K}
-0.0198, !- Coefficient 3 of Efficiency Equation
(2nd Order) {W/m2-K2}
-0.2964, !- Coefficient 2 of Incident Angle
Modifier (1st Order)
0.0191; !- Coefficient 3 of Incident Angle
Modifier (2nd Order)

Does anyone have some pointers why this is happening? I am using the
Boulder, CO weather file (similar behavior for TM2 and TM3).

Thanks.

Tobias



 


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