Estimation of solar radiation from cloud cover data of Bangladesh

Sustainable Energy Research

Table 7 Regression models to estimate solar radiation directly from cloud cover fraction

#	Model type	Equations	R ²	MBE	MPE	MARE	RMSE	t-stat
1	Linear	\(H/H_0 = -0.2302C + 0.5713\)	0.9936	0.0213	0.6566	0.0716	0.3315	0.2139
2	Quadratic	\(H/H_0 = -0.4585C^2 + 0.2087C + 0.4942\)	0.9953	0.0157	0.4905	0.0585	0.2834	0.1850
3	Third degree	\(H/H_0 = 1.9104C^3 - 3.1785C^2 + 1.3352C + 0.3669\)	0.9954	0.0135	0.4482	0.0481	0.2831	0.1593
4	Fourth degree	\(H/H_0 = -11.449C^4 + 23.22C^3 - 16.729C^2 +4.7227C + 0.0963\)	0.9957	0.0008	0.8008	0.0543	0.2721	0.0098
5	Fifth degree	\(H/H_0 = 120.19C^5 - 299.15C^4 + 281.59C^3 -124.07C^2 + 25.073C - 1.3032\)	0.9974	0.0151	0.1131	0.0344	0.2107	0.2395
6	Logarithmic	\(H/H_0 = -0.083\ln (C) + 0.386\)	0.9905	0.0164	0.8877	0.0909	0.4052	0.1347
7	Exponential	\(H/H0 = 0.5819exp^{(-0.509C)}\)	0.9931	0.0362	0.3475	0.0728	0.3445	0.3505
8	Power	\(H/H0 = 0.3862C^{(-0.184)}\)	0.9899	0.0376	0.4436	0.0916	0.4184	0.2994