engineering application The radiant energy from the Sun that reaches Earth\'s or
ID: 2059059 • Letter: E
Question
engineering application
The radiant energy from the Sun that reaches Earth's orbit is1.35kW/m2 (a) Even when the Sun is directly overhead andunder dry desert conditions, 25 percent of this energy is absorbedand /or reflected by the atmosphere before it reaches Earth'ssurface. If the average frequency of the electromagnetic radiationfrom the Sun is 5.5x1014 Hz, how many photons per secondwould be incident upon a 1.0-m2 solar panel? (b) Supposethe efficiency of the panels for converting the radiant energy toelectrical energy and delivering it is a highly efficient 10.0percent. How large a solar panel is neede to supply the needs of a5.0-hp solar-powered car (assuming the car runs directly off thesolar panel and not batteries) during a race in Cairo at noon onMarch 21? (c) Assuming a more-realistic efficiency of 3.3 percentand panels capable of rotating to be always perpendicular to thesunlight, how large an array of solar panels is needed to supplythe power needs of the International Space Station (ISS)? The ISSrequires about 110kW of continuous electric power.
Explanation / Answer
a) Energy reaching earth surface = .75 * 1.35 W/m2 = 1.0125 W/m2 Energy of 1 photon = h*frequency = 3.644*10^-19 J Photon Incident /Sec / m2 = Energy / Energy of 1 photon = 2.778*10^18 photon
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