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.
| 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