How to find solar insolation in the IR spectrum

In summary, the task is to compute the solar irradiance in the near IR range at the top of the atmosphere over Denver at noon on August 23rd, assuming that 37% of the solar spectrum is in this range. The equations used include I=ScosZ, where Z is the azimuth angle over Denver at this time and S is 1360Wm-2, and I=I(0) exp(-u secZ), where u is the optical depth. However, the computed azimuth angle of 254.8 degrees results in a negative value for the first equation and the secant of 254.8 is undefined. The declination angle and solar hour angle were also used in the calculation, but the
  • #1
pondwire
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Homework Statement


Compute the solar irradiance in the near IR range (0.7 - 1.5 microns) at the top of the atmosphere over Denver at noon on August 23rd, and assume that 37 per cent of the solar spectrum is in this range.




Homework Equations


Equations? I=ScosZ where Z is the azimuth angle over Denver at this time, S is 1360Wm-2. Also, there is an equation that's supposed to give actual amount striking surface:
I = I(0) exp(-u secZ), where u is the optical depth.


The Attempt at a Solution


Failed miserably because my computed azimuth angle is 254.8 degrees which results in a negative value for the first equation. I tried the second equation anyway, and the secant of 254.8 is undefined. I spent a lot of time trying to figure out the azimuth angle and could only come up with 254.8 degrees. For that equation (azimuth) I used:

A = 180 deg. + sin-1(cos(11.5)sin(99.8) / sin(90))
Here, 11.5 is the declination angle, which was found from the analemma; 99.8 is the solar hour angle; and 90 is the sun's zenith angle at noon.

Please help. Thanks.
 
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  • #2
Why do you need the azimuth angle? You need the altitude of the Sun because that determines what angle the sun's rays hit the ground at. Try calculating the declination of the Sun at the time and work from there, remembering that at noon, the Sun is due south.
 

1. What is solar insolation in the IR spectrum?

Solar insolation in the IR spectrum refers to the amount of solar radiation that reaches the Earth's surface in the infrared wavelength range. This radiation is a form of electromagnetic radiation emitted by the sun and can be measured using specialized instruments.

2. Why is it important to find solar insolation in the IR spectrum?

Understanding solar insolation in the IR spectrum is important for a variety of reasons. It can help us better understand the Earth's climate and weather patterns, as well as the impact of solar radiation on our planet. It is also crucial for developing and improving solar energy technologies.

3. How can solar insolation in the IR spectrum be measured?

Solar insolation in the IR spectrum can be measured using instruments such as pyranometers, pyrheliometers, and spectroradiometers. These devices measure the amount of solar radiation in different wavelengths, including the infrared range.

4. What factors affect solar insolation in the IR spectrum?

There are several factors that can affect solar insolation in the IR spectrum, including the Earth's tilt, atmospheric conditions, and the position of the sun. Additionally, factors such as cloud cover, air pollution, and surface albedo can also impact the amount of solar radiation that reaches the Earth's surface.

5. How can I use solar insolation data in the IR spectrum?

Solar insolation data in the IR spectrum can be used for a variety of purposes, including predicting weather patterns, studying the Earth's climate, and designing solar energy systems. It can also be compared to data from other parts of the electromagnetic spectrum to gain a more comprehensive understanding of solar radiation.

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