## 4 Conclusions
**Nomenclature**  
General Parameter  
A  Area, m\({}^{2}\)  
Cp  Specific heat capacity of the fluid, kJ/(kg K)  
C  Concentration ratio, -  
D  Diameter, m  
E  Energy flow, W  
f  Friction factor, -  
G  Intensity of solar radiation, W/m\({}^{2}\)  
h  Coefficient of heat convection, W/(m\({}^{2}\) K)  
L  Length, m  
m  Mass flow rate, kg/s  
P  Power, W  
P  Perimeter, m  
Q  Energy rate, W  
Re  Reynolds number, -  
Re\({}_{\rm cr}\)  Critical Reynolds number, -  
T  Temperature, \({}^{\circ}\)C  
u  Wind speed, m/s  
V  Volume flow rate, m\({}^{3}\)/s  
W  Power, W  
Greek symbols  
\(\beta\)  Coefficient temperature for PV element, %/K  
\(\Delta\)P  Pressure drop, Pa  
\(\eta_{\rm el}\)  Electric efficiency, -  
\(\eta_{\rm lex}\)  Energy efficiency, -  
\(\eta_{\rm th}\)  Thermal efficiency, -  
\(\eta_{\rm opt}\)  Optical efficiency, -  
v  Kinematic viscosity, m\({}^{2}\)/s  
\(\rho\)  Density, kg/m\({}^{3}\)  
Subscripts  
a  Ambient  
abs  Absorbed  
b  Beam  
col  Collector  
cpc  Utilized by the reflector  
d  Diffuse  
down  Bottom  
eff  Effective  
el  Electrical  
g  Glass  
h  Hydraulic  
in  Inlet  
m  Mean  
n  Normal  
opt  Optical  
out  Outlet  
pv  Photovoltaic  
r  Receiver  
ref  Reference  
s  Solar  
sky  Sky  
sol  solar  
sun  Sun  
T  Perpendicular to aperture  
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