Consider the concentrating photovoltaic apparatus of Problem 7.19. The apparatus is to be installed in a desert environment, so the space between the concentrating lens and top of the photovoltaic cell is enclosed to protect the cell from sand abrasion in windy conditions. Since convection cooling from the top of the cell is reduced by the enclosure, an engineer proposes to cool the photovoltaic cell by attaching an aluminum heat sink to its bottom surface. The heat sink dimensions and material are the same as those of Problem 7.29. A contact resistance of 0.5 x 10-4 m2 ∙ K/W exists at the photovoltaic cell/heat sink interface and a dielectric liquid (k = 0.064 W/m ∙ K. v = 10-6 m2/s. Pr = 25) flows between the heat sink fins at U'X = 3 m/s, Too = 25°C.

(a) Determine the electric power produced by the photovoltaic cell and the silicon temperature for a square concentrating lens with Liens = 400 mm.

(b) Compare the electric power produced by the photo-voltaic cell with the heat sink in place and with the bottom surface cooled directly by the dielectric fluid (i.e., no heat sink) for Llens = 1.5 m.

(c) Determine the electric power output and the silicon temperature over the range 100 mm Liens < 3000 mm with the aluminum heat sink in place.