Solar Radiation

1
Solar Radiation
Goals Understand solar radiation and solar
constant qualitative
effects of incident angle.
2
Q1

• A detector is measuring solar radiation intensity
  I at point A, B, C. Which is true?
• I(A) gt I(B) gt I(C)
• I(A) gt I(C) gt I(B)
• I(C) gt I(B) gt I(A)
• 4) I(B) gt I(A) gt I(C).

3
Q2

• You see someone plotted the radiation intensity
  as a function of distance from the sun, R. Which
  one is true?
• A) I(R) increases as a function of R
• B) I(R) decreases as a function of R
• C) I(R) is independent of R

4
Solar radiation constant

• Solar radiation intensity near the earth is
• called solar radiation constant.
• It is about S1367W/m2.
• Why not higher or lower?

5
Q3

• On a planet that is at distance d5 a.u. from the
  sun, the solar constant is about
• A) 54 W /m2
• B) 270 W /m2
• C) 1,367 W /m2
• D) 5W / m2.

6
Power per unit area versus the distance
http//hyperphysics.phy-astr.gsu.edu/hbase/forces/
isq.html
7
Q4

• A solar-battery powered heater is used to heat
  water in a house. The surface area of the solar
  panel is 5m2 and efficiency is 25. At noon
  time under direct sunshine, what is the output
  power of the solar battery?
• A) 5W
• B) 75 W
• C) 1.75 kW
• D) 10kW.

8
Q5

• During the noon time, to power a heater
  which works with input power 5kW, the surface
  area of the solar panel should be around
• A) 1m2
• B) 8m2
• C) 15m2
• D) 30m2.

9
Incident-angle (theta) dependence of intensity .
theta
A
A
gt
10
Energy per square meter decreases at lower sun
angles and shorter daylight periods.