1. Consider the transmission case of Problem 1.23, but now allow for radiation exchange with the ground/ chassis, which may be approximated as large surround- ings at Tsur = 30°C. If the emissivity of the case is s = 0.80, what is the surface temperature?
2. One method for growing thin silicon sheets for photo- voltaic solar panels is to pass two thin strings of high melting temperature material upward through a bath of molten silicon. The silicon solidifies on the strings near the surface of the molten pool, and the solid silicon sheet is pulled slowly upward out of the pool. The silicon is replenished by supplying the molten pool with solid sili- con powder. Consider a silicon sheet that is Wsi = 85 mm
(a) Determine the electric power, Pelec, needed to oper- ate the system at steady state.
(b) If the photovoltaic panel absorbs a time-averaged solar flux of q"sol = 180 W/m2 and the panel has a conversion efficiency (the ratio of solar power absorbed to electric power produced) of 77 = 0.20, how long must the solar panel be operated to pro- duce enough electric energy to offset the electric energy that was consumed in its manufacture?