Question

The daytime solar flux density measured above the Earth’s atmosphere is about 1370 Watts/m^2

(a) How far do you need to be away from a 100-W bulb for it’s radiant flux to equal that of the Sun’s at Earth?

(b) What is the average daytime solar flux density measured at Mars?

(c) If the approximate efficiency of the solar panels (1.3m^2 ) on the Martian rover, Spirit, is 30%, how many Watts could the fully illuminated panels generate? How many 60 W bulbs could these solar panels power?

(d) If we do not assume that the Sun is directly overhead from the rover, but at a 45 degree angle from overhead, how does this change the power generated in part c? How many 60 W light bulbs could the solar panels power with the sun at an angle?

Answer 1

The flux density is simply the power divided by the area of the spherical shell at the required radius.

About 15 cm away from the bulb.

The distance of mars to sun is 1.524 AU.

The power obtainable is:

It can power about 4 bulbs. (actually 3.78 bulbs)

The new power is just the cos(45) times the old power.

P_new=160.54 W

number of 60 W bulbs = 2.675 bulbs