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I am trying to calculate the amount of electricity generated and heat collected by a PV/T panel using Type 50.
I have a question about heat collection.
To calculate the amount of heat collected by the panel, we need the intercept and slope of the heat collection efficiency graph. In the same collector, Type 71, there is a parameter for intercept and slope. in Type 50a, I guess the 6th parameter (collector loss coefficient) is the slope. However, I am not sure how to set the intercept. How can I use the setting? My understanding may be wrong.
I would like to apologize for my poor English.
Your English is very good! I think I understand the question you are asking, but if not, please let me know!
I assume you are trying to set the parameters of Type 50 to model a collector for which you know the intercept and slope of its efficiency curve. In other words, you know the parameters Frta and FrUl in the Hottel-Whillier equation:
efficiency = Frta - FrUl*(T_inlet - T_ambient)/IncidentSolar
Unfortunately, Type 50 does not take the intercept and slope of the efficiency curve as parameters the way Type 71 and other models do. Type 50a takes the following four parameters for thermal efficiency: the collector fin efficiency factor (F', Parameter 3), the collector plate absorptance (alpha, Parameter 5), the cover transmittance (tau, Parameter 9), and the collector loss coefficient (Ul, Parameter 6). The product of F' x tau x alpha is similar to Frta, and the product of F' x Ul is similar to FrUl. As a quick way to get started, I would assume guess values for the transmittance and absorptance (or the actual values at an incidence angle of 0 degrees, if you have them), calculate Fr from Frta/(tau x alpha), calculate Ul as FrUl/Fr, and set F' = Fr (approximate). I should caution, the assumption that F' is similar to Fr will work much better for collectors with high flow rates per unit area and low loss coefficients than it will for lower flow rates and higher loss coefficients; however, Fr can never be greater than F', so it will at least be a conservative model of collector thermal performance.
For an even better model, I would use a resource like Solar Engineering of Thermal Processes by J.A. Duffie and W.A. Beckman, and calculate F' from Fr. In the 2nd edition of the book, Eqn (6.7.4) can be re-arranged to solve for F' as a function of Fr and Ul. You will also need to know the tested flow rate per unit collector area and the specific heat of the collector test fluid to solve for F'.
Best of luck!
