## Nomenclature
\begin{tabular}{l l} \(L_{\rm c}\) & Characteristic length of the PV section (\(L_{\rm c}=L_{\rm PV}\)) or acrylic plate (\(L_{\rm c}=L_{\rm AP}\)) in m \\ \(L_{\rm PV}\) & Height of the PV section in m \\ \(L_{\rm TS}\) & Height of the top section of the solar chimney in m \\ Nu & Nusselt number \\ Pr & Prandtl number \\ \(Q_{\rm air}\) & Amount of heat absorbed by the mass of the air in the ventilation channel in W \\  & Free convection heat transfer between the upper surface of the PV section and \\ \(q_{\rm c,PV}\) & the ambient air in W/m\({}^{2}\) \\ \(q_{\rm E,S}\) & Solar irradiance that can be received by a horizontal surface on Earth in W/m\({}^{2}\) \\ \(Q_{\rm el}\) & Power related to the generation of electricity in the PV section in W \\ \(q_{\rm t,AP}\) & Heat transfer through the acrylic plate between the air in the ventilation \\  & channel and the ambient air in W/m\({}^{2}\) \\ \(q_{\rm t,PV}\) & Radiation heat exchange between the upper surface of the PV section and the surroundings in W/m\({}^{2}\) \\ Ra & Rayleigh number \\ Re & Reynolds number, \(\rm Re=\
u_{\rm air}d_{\rm H}/\
u_{\rm av}\) \\ \(S_{\rm AP}\) & Area of one side of the acrylic plate in m\({}^{2}\) \\ \(S_{\rm D}\) & Cross-sectional area of the ventilation channel in m\({}^{2}\) \\ \(S_{\rm PV}\) & Area of one side of the PV section in m\({}^{2}\) \\ \(T_{\rm a}\) & Temperature of the ambient air in K or \({}^{\circ}\)C \\ \(T_{\rm a,av}\) & Average temperature of the air in the ventilation channel in K or \({}^{\circ}\)C \\ \(T_{\rm AP}\) & Average temperature of the acrylic plate in K or \({}^{\circ}\)C \\ \(T_{\rm APb}\) & Temperature of the bottom surface of the acrylic plate in K or \({}^{\circ}\)C \\ \(T_{\rm APu}\) & Temperature of the upper surface of the acrylic plate in K or \({}^{\circ}\)C \\ \(T_{\rm f}\) & Film temperature in K \\ \(T_{\rm i}\) & Temperature of the air at the inlet of the ventilation channel in K or \({}^{\circ}\)C \\ \(T_{\rm o}\) & Temperature of the air at the outlet of the ventilation channel in K or \({}^{\circ}\)C \\ \(T_{\rm PV}\) & Average temperature of the PV section in K or \({}^{\circ}\)C \\ \(T_{\rm PVb}\) & Temperature of the bottom surface of the PV section in K or \({}^{\circ}\)C \\ \(T_{\rm PVu}\) & Temperature of the upper surface of the PV section in K or \({}^{\circ}\)C \\ \(T_{\rm sky}\) & Temperature of the sky in K or \({}^{\circ}\)C \\ \(U_{\rm AP}\) & Overall heat transfer coefficient for the acrylic plate in W/(m\({}^{2}\cdot\)K) \\ \(v_{\rm air}\) & Average velocity of the air in the ventilation channel in m/s, \(v_{\rm air}=(v_{\rm i}+v_{\rm o})/2\) \\ \(v_{\rm l}\) & Air velocity at the inlet of the ventilation channel in m/s \\ \(v_{\rm o}\) & Air velocity at the outlet of the ventilation channel in m/s \\ \(\alpha_{\rm A}\) & Solar absorption coefficient for the absorption area of the absorber \\ \(\alpha_{\rm PV}\) & Solar absorption coefficient for the upper surface of the PV section \\ \(\alpha_{\rm t}\) & Thermal diffusivity of air in m\({}^{2}\)/s, \(\alpha_{\rm t}=k_{\rm f}/(\rho\cdot c_{\rm t})\) \\ \(\beta\) & Thermal expansion coefficient of air in 1/K, \(\beta=1/T_{\rm f}\) \\ \(\Delta_{\rm AP}\) & Thickness of the acrylic plate in m, \(\Delta_{\rm AP}=0.003\) m \\ \(\Delta p_{\rm t,buoy}\) & Total pressure difference due to buoyancy (natural draft pressure) in kg/(m\(\cdot\)s\({}^{2}\)) \\ \(\Delta p_{\rm t,loss}\) & Total pressure drop across the ventilation channel in kg/(m\(\cdot\)s\({}^{2}\)) \\ \(\Delta T\) & Temperature difference between the two surfaces of the PV section in K \\ \(\varepsilon_{\rm PV}\) & Thermal emissivity for the upper surface of the PV section \\ \(\eta_{\rm el}\) & Efficiency of conversion of solar energy into electricity \\ \(\mu\) & Dynamic viscosity of air at the film temperature \(T_{\rm f}\) in kg/(m\(\cdot\)s) \\ \(\
u\) & Kinematic viscosity of air in m\({}^{2}\)/s, \(\
u=\mu/\rho\) \\ \(\
u_{\rm av}\) & Average kinematic viscosity of the air in the channel at the temperature \(T_{\rm a,av}\) \\  & in m\({}^{2}\)/s \\ \(\Pi_{\rm D}\) & Wetted perimeter of the channel in m, \(\Pi_{\rm D}=0.45\) m \\ \end{tabular}