A solar panel mounted on a spacecraft has an area of 1 m2 and a solar-to-electrical power conversion effi- ciency of 12%. The side of the panel with the photo- voltaic array has an emissivity of 0.8 and a solar absorptivity of 0.8. The back side of the panel has an emissivity of 0.7. The array is oriented normal to solar irradiation of 1500 W/m2.
(a) Determine the steady-state temperature of the panel and the electrical power (W) produced for the prescribed conditions.
(b) If the panel were a thin plate without the solar cells, but with the same radiative properties, determine the temperature of the plate for the prescribed con- ditions. Compare this result with that from part (a). Are they the same or different? Explain why.
(c) Determine the temperature of the solar panel 1500 s after the spacecraft is eclipsed by a planet. The thermal capacity of the panel per unit area is 9000 J/m2 · K.
Consider conditions for which the solar and atmospheric irradiations are GS = 600 W/m2 and Gatm = 300 W/m2, respectively, and the air temperature and relative humidity are T00 = 27°C and 00 = 0.50, respectively. The reflectivities of the water surface to the solar and atmospheric irradiation are pS = 0.3 and patm = 0, respectively, while the surface emissiv- ity is s = 0.97. The convection heat transfer coefficient at the air-water interface is h = 25 W/m2 · K. If the water is at 27°C, will this temperature increase or decrease with time?