Thermal

The thermal inputs define how SunSolve Yield calculates the operating temperature of the modules. They are found under the Thermal panel of the Losses tab.

For the equations behind these inputs — the energy balance, view-factor irradiance, and each heat-flow component — see the Thermal model technical reference.

Thermal model for modules

The Thermal model for modules dropdown selects one of two models:

ModelDescription

Faiman, The standard Faiman model. Groups all cooling into two coefficients and requires only the absorptance and the two heat-transfer coefficients.

Extended Faiman, Applies the Faiman model but adds optional heat-flow mechanisms — transients,, radiation to the sky,, heat flow to the ground,, tilt dependence,, and wind direction.

Common inputs

The following inputs apply to both the Faiman and Extended Faiman models.

Energy absorption

InputSymbolDescriptionFront absorptance, ${\alpha }_f$, Fraction of front plane-of-array irradiance absorbed as heat.Rear absorptance, ${\alpha }_r$, Fraction of rear plane-of-array irradiance absorbed as heat.

Heat-transfer coefficients

InputSymbolDescription

Calm U-value, $U_c$, Heat flow to the ambient with no wind. Represents all forms of cooling other than forced convection.

Wind U-value, $U_v$, Forced-convection coefficient; scales heat flow to the ambient with wind speed.

Extended Faiman options

When Extended Faiman is selected, additional heat-flow mechanisms can be enabled with checkboxes. Each option reveals its own inputs when enabled.

OptionRevealsDescription

Account for transients, Module weight/area ($m_{\text{mod}}$) and module heat capacity ($c_{\text{mod}}$), Makes the current module temperature depend on its previous temperature. Important for time steps of 15 minutes or less.

Include radiation to sky, Module emissivity ($\epsilon$), Adds radiative heat flow from the module to the sky.

Include heat flow to ground, Ground temperature model,, ground temperature ($T_g$),, and ground U-value ($U_g$), Adds a heat-flow path from the module to the ground.

Include tilt dependence of $U_c$, Dependence on tilt ($U_{c\beta }$), Adjusts the calm U-value with module tilt.

Account for wind direction, Amplitude ($a$),, frequency ($b$),, and phase shift (${\delta }_0$), Modulates the wind U-value with wind direction.

Ground temperature model

When Include heat flow to ground is enabled, the Ground temperature model dropdown determines the temperature of the ground heat sink:

ModelDescriptionEqual to $T_{\text{amb}}$, The ground temperature tracks the ambient temperature at each time step.Constant, A fixed ground temperature ($T_g$), entered in kelvin.

The Ground U-value ($U_g$) sets the heat-transfer coefficient for flow between the module and the ground.