Consider the photovoltaic solar panel of Example 3.3. The heat transfer coefficient should no longer be taken to be a specified value.
(a) Determine the silicon temperature and the electric power produced by the solar cell for an air velocity of 4 m/s parallel to the long direction, with air and surroundings temperatures of 20°C. The boundary layer is tripped to a turbulent condition at the leading edge of the panel.

(b) Repeat part (a), except now the panel is oriented with its short side parallel to the airflow, that is, L = 0.1 m and w = 1m.
(c) Plot the electric power output and the silicon temperature versus air velocity over the range 0 ≤ u_m ≤ 10 m/s for the L = 0.1 m and w = 1 m case.

Example 3.3

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A photovoltaic panel consists of (top to bottom) a 3-mm-thick ceria-doped glass (kg = 1.4 W/m.K), a 0.1-mm-thick optical grade adhesive (k = 145 W/m-K), a very thin layer of sili- con within which solar energy is converted to electrical energy, a 0.1-mm-thick solder layer (Ksdr = 50 W/m .K), and a 2-mm-thick aluminum nitride substrate (Kan = 120 W/m-K). The solar-to-electrical conversion efficiency within the silicon layer n decreases with increasing silicon temperature, Tsi, and is described by the expression n = a - bTsi, where a = 0.553 and b = 0.001 K-¹. The temperature T is expressed in kelvins over the range 300 K ≤ T ≤ 525 K. Of the incident solar irradiation, G = 700 W/m², 7% is reflected from the top surface of the glass, 10% is absorbed at the top surface of the glass, and 83% is transmitted to and absorbed within the silicon layer. Part of the solar irradiation absorbed in the silicon is con- verted to thermal energy, and the remainder is converted to electrical energy. The glass has an emissivity of ε = 0.90, and the bottom as well as the sides of the panel are insulated. Determine the electric power P produced by an L = 1-m-long, w = 0.1-m-wide solar panel for conditions characterized by h = 35 W/m² K and T = Tsur = 20°C. Electric power to grid, P Constr Air Glass T = 20°C h = 35 W/m2.K Adhesive -Silicon layer Solder L=1m- G = 700 W/m² Tur=20°C Substrate L₂ = 3 mm = 0.1 mm = 2 mm Ldr = 0.1 mm an