Modeling the effect of the inclination angle on natural convection from a flat plate: The case of a photovoltaic module

Abstract

a Fac ulty of Tech ni cal Sci ences, Uni ver sity of Pristina in Kosovska Mitrovica, Kosovska Mitrovica, Ser bia b In de pend ent Con sul tant in the Field of Ur ban and Spa tial Plan ning, Nis, Ser bia c Fac ulty of Elec tronic En gi neer ing, Uni ver sity of Nis, Nis, Ser bia d Kulab, KU Leuven, Ostend, Bel gium Orig i nal sci en tific pa per https://doi.org/10.2298/TSCI140821059PThe main pur pose of this pa per is to show how the in cli na tion an gle af fects nat u ral con vec tion from a flat-plate pho to vol taic mod ule which is mounted on the ground sur face. In or der to model this ef fect, novel cor re la tions for nat u ral con vec tion from iso ther mal flat plates are de vel oped by us ing the fun da men tal dimensionless number. On the ba sis of the avail able ex per i men tal and nu mer i cal re sults, it is shown that the nat u ral con vec tion cor re la tions cor re spond well with the ex ist ing em pir i cal cor re la tions for ver ti cal, in clined, and hor i zon tal plates. Five ad di tional cor re lations for the crit i cal Grashof num ber are de rived from the avail able data, three indi cat ing the on set of tran si tional flow re gime and two in di cat ing the on set of flow sep a ra tion. The pro posed cor re la tions cover the en tire range of in cli na tion an gles and the en tire range of Prandtl num bers. This pa per also pro vides two worked exam ples, one for nat u ral con vec tion com bined with ra di a tion and one for nat u ral con vec tion com bined with forced con vec tion and ra di a tion. Key words: em pir i cal cor re la tion, flat plate, fun da men tal dimensionless num ber, in cli na tion an gle, nat u ral con vec tion, pho to vol taic mod ule Perovi}, B. D., et al.: Modeling the Effect of the Inclination Angle .· In tro duc ing the pro posed cor re la tions into the heat trans fer model, a sim ple al go rithm to es ti mate the av er age heat trans fer co ef fi cients due to nat u ral con vec tion, forced con vec tion, and ra di a tion is de vel oped. The heat trans fer co ef fi cients due to nat u ral con vec tion are avail able for dif fer ent in cli na tion an gles. · The pro posed heat trans fer model that is based on the Swinbank cor re la tion [28] gives better re sults than the mod els de vel oped us ing the ra di a tion shape fac tors. · The heat trans fer co ef fi cients due to nat u ral con vec tion from the in clined PV mod ules have trends which are in the line with the ex pec ta tions. · The heat losses due to nat u ral con vec tion from the UF and DF sur faces of the PV mod ules are be tween 6.775-20.175% and 3.082-16.092% of the to tal heat loss, re spec tively. Lower val ues of the heat losses due to nat u ral con vec tion cor re spond to the case when the trans fer of heat is af fected by the wind. · The pre sented an a lyt i cal re sults cor re spond well with ex ist ing ex per i men tal data. Ac knowl edge mentThis pa per was based on re search con ducted within the pro ject TR33046 funded by the Min is try of Ed u ca tion, Sci ence, and Tech no log i c...

A thermal model for open-rack mounted photovoltaic modules based on empirical correlations for natural and forced convection

“…The calculation of the temperature of an open-rack mounted PV module is based on the following assumptions [8,9]: The structure consisted of front glass, encapsulant over PV cells, PV cells, encapsulant under PV cells and tedlar backing sheet is assumed to be homogenous, isotropic and isothermal; The solar absorptivity α S for the front PV module surface is assumed to be constant and equal 0.97; The solar absorptivity and thermal emissivity for the front and back PV module surfaces are considered as independent of wavelength; The four lateral edges of the PV module are considered as adiabatic; The sky is clear; It is assumed that the PV module operates under steady-state conditions. This thermal model is based on an energy balance between the energy of solar radiation incident on the front PV module surface α S G, on one side, and the electricity generated in the PV module η el α S G and the heat dissipated by convection and radiation from the PV module surfaces, on the other.…”

“…The values for h f and h b are estimated using the correlations for natural and forced convection between the front and back PV module surfaces and the air. The correlations for natural convection are given in [9], while the correlations for forced convection are derived in the next section. The correlations for natural convection from [9] include the effects of the inclination angle and flow separation.…”

“…The correlations for natural convection are given in [9], while the correlations for forced convection are derived in the next section. The correlations for natural convection from [9] include the effects of the inclination angle and flow separation. The proposed thermal model is more complicated than the SNL and NOCT-based correlations because it incorporates the more complex and more precise correlations for natural and forced convection.…”

“…This is valid for the values of the Reynolds number Re ≤ 5·10 5 for which the flow is considered to be laminar [14]. For the values of the Reynolds number Re > 5·10 5 , regardless of the angle, α, and other flow conditions, it is assumed that the flow is turbulent [9,14]. Based on the correlation proposed by Kendoush [15] and the experimental results used in [12], the dependence of the coefficient h windward on the angle, α, wind velocity, v w , and characteristic length, L c , can be expressed:…”

An empirical correlation of ambient temperature impact on PV module considering natural convection

“…Parameters description indicated in the above equations[21][22][23][24] Parameter Description Unit TPVThe mean value of the PV modulus temperature. [K] αSThe solar radiation absorption coefficient for upper surfaces of the PV module.…”