Table 6.

The mathematical equations of PV/T with triangular tubes [77].

Description	Equations
Solar energy input ratio	$\delta SEIR=\frac{\delta m_a}{m_a}\left)\frac{\delta P}{mP}\right)\frac{\delta T_6}{T_6}\left)\frac{\delta I}{I}\right)\frac{\delta T_5}{T_5}\left)ANN\right){\left(ANN\right){\left(ANN\right)}^2]}^{1/2}$
PV efficiency	$\eta =\frac{P{V}_{output}}{A\times I}$
Fraction of absolute variance (R2)	$R^2=1-\frac{{\sum }_{m=1}^n{(y_{pre,m}-t_{mea,m})}^2}{{\sum }_{m=1}^n{\left(t_{mea,m}\right)}^2}$
Root mean square error (RMS)	$RMS=\sqrt{\frac{{\sum }_{m=1}^n{(y_{pre,m}-t_{mea,m})}^2}{n}}$
Coefficient of variance (COV)	$COV=\frac{RMS}{{\sum }_{m=1}^n\left(t_{mea,\mathrm{avg}}\right)}\times 100$