Question

What is the standard value of the solar constant?

• A. \(1.75\text{ kW/m}^2\)
• B. \(1.50\text{ kW/m}^2\)
• C. \(1.36\text{ kW/m}^2\)
• D. \(1.00\text{ kW/m}^2\)

Hint:

Solar constant $= 1367\text{ W/m}^2 = 1.367\text{ kW/m}^2 = 432\text{ Btu/ft}^2\cdot\text{h} = 1.96\text{ Langley/min}$.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The solar constant (\(I_{sc}\)) is the rate of total solar radiant energy received on a unit area oriented perpendicular to the sun's rays at the mean earth-sun distance outside the earth's atmosphere.
Key Formula or Approach:
\[ I_{sc} = 1367\text{ W/m}^2 = 1.367\text{ kW/m}^2 \approx 1.36\text{ kW/m}^2 \]

Step 2: Detailed Explanation:
The World Meteorological Organization (WMO) and NASA standard value for the extraterrestrial solar constant is \(1367\text{ W/m}^2\) (or \(1.96\text{ cal/cm}^2\cdot\text{min}\)).
Expressed in kilowatts per square meter:
\[ I_{sc} = \frac{1367}{1000} = 1.367\text{ kW/m}^2 \approx 1.36\text{ kW/m}^2 \]

Step 3: Final Answer:
Therefore, the standard value of the solar constant is \(1.36\text{ kW/m}^2\), corresponding to option (C).