[TRNSYS-users] Translating SRCC OG-100 solar water heater collector equations into TRNSYS

[Thomas de Fresart]

I need help translating SRCC OG-100 ratings into TRNSYS.  Specifically, I
have questions (listed below background info) on what the units are and if
they are positive or negative.

I'm currently translating the SRCC OG-100 ratings of a flat plate collector
used in domestic solar water heating into my TRNSYS program.  I'm using at
Type 539 under the Tess Solar Library - Glazed Flat Plate Collector - OG100
Quadratic Efficiency Approach.

My solar collector has the following specs:
https://securedb.fsec.ucf.edu/srcc/coll_detail?srcc_id=2007032A

* Efficiency Equation [NOTE: Based on gross area and (P)=Ti-Ta]* *Y
INTERCEPT**SLOPE*   *SI Units:*η= 0.718 -2.29060  (P)/I-0.04398  (P)2/I
0.744-5.151  W/m2.°C

 *Incident Angle Modifier [(S)=1/cosθ - 1, 0°<θ<=60°]*    *Kτα* = 1
-0.322  (S) 0.031  (S)2    *Kτα* = 1-0.29  (S) Linear Fit

TRNSYS states, Efficiency = a0 - a1*(T-T_Ambient)/G - a2*(T-T_Ambient)^2/G
   where T = fluid temperature
              T_Ambient = ambient air temperature
              G = total solar radiation incident on the surface [kJ/hr]

Parameter a1 is the first-order parameter of the collector efficiency
equation.  Its units are [kJ/hr-m2-K].
Parameter a2 is the second-order parameter of the collector efficiency
equation.  Its units are [kJ/hr-m2-K2].


-and for IAM coefficients -
Modifier = 1 - b0 * S - b1 * S^2

where S=1/cos(Incidence angle)-1
b0 and b1 correspond to the two IAM coefficients


Here is what I am doing, but would like confirmation:
*TRNSYS Parameter                           TRNSYS Value   ... from SRCC
value*
Intercept efficiency (a0)                      +0.718 (no units, η from
SRCC specs)
1st order efficiency coefficient (a1)      +2.29060 (W/m^2*K?)  (P)/I
(-2.29060) from SRCC specs, but input as a positive value in TRNSYS?
2nd order efficiency coefficient (a2)     +0.04398 (W/m^2*K)?  (P)2/I
(-0.04398)from SRCC specs, but input as a positive value in TRNSYS?
1st order IAM coefficient                    +0.332 (no units)        S
(-0.322) from SRCC specs, but input as a positive value in TRNSYS, or
should this be negative
2nd order IAM coefficient                    -0.031 (no units)
(S)2 (+0.031)from
SRCC specs, but I input as negative value in TRNSYS since it's the opposite
of all others


   - I want to confirm that the W/m^2.C that is noted on the SRCC webpage
   next to the slope is what I'm using for a1 and a2 units, instead of the
   kJ/hr.m^2.K^2 that TRNSYS has as default.  Or are the SRCC units posted
   in kJ/hr.m^2.K^2 ?
   - I also want to know which units are positive and which are negative,
   as it seems SRCC states them opposite of how they are inputted into TRNSYS,
   but I'm not 100% certain, especially for the IAM coefficients.


Thanks!
Tom
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