Solar Panels and Solar Radiation Flux Density Help - Very Confused

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Homework Help Overview

The discussion revolves around the calculation of solar power and solar radiation flux density, particularly in the context of solar panels. The original poster expresses confusion regarding the time period for energy calculations, the concept of solar radiation flux density, and how to account for factors such as the angle of inclination of solar panels.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate power from energy values but questions the appropriateness of using a full 24-hour period for daylight hours. They also express uncertainty about solar radiation flux density and its relevance to their calculations. Some participants suggest that the terms related to solar radiation may be more straightforward than initially thought and encourage the poster to consider the angle of inclination in their calculations.

Discussion Status

Participants are exploring different interpretations of solar radiation flux density and its relationship to intensity. There is an ongoing dialogue about the implications of angle on solar energy received by panels, with some guidance provided regarding the use of trigonometry to relate these concepts. However, there is no explicit consensus on the correct approach or calculations.

Contextual Notes

The original poster notes a lack of specific information regarding daylight hours in their region, which affects their calculations. Additionally, there is mention of textbook references that are unclear to the poster, contributing to their confusion.

  • #31
Steve4Physics said:
Agreed.No. It is meaningless to refer to the "intensity of the solar panel". The solar panel does not have an intensity. The intensity is the amount of power from the sun per square metre. 5.53W/m² is the intensity *calculated assuming the solar panels are 100% efficient*. So 5.53W/m² is not an accurate value of intensity (because efficiency is not 100%).

But we know the panels are only 20.8% efficient. So intensity must be (roughly 5 times) bigger than 5.53W/m².Yes but round to 3 sig. figs.No. First, 'example' is the wrong word. And we physicists don't use words like 'tremendous' in this context! Just say (for example) "300W/m² is an overestimate ...
'per day' is wrong. You = mean averaged over a day.
13.29055 is too many significant figures.

The most *accurate* values of intensity are the ones calculated allowing for efficiency. So you should be averaging the answers from 1c) and 2c), not from 1b) and 2b).
(204 + 26.6)/2 = 115Wm/s²
So the 300W/m² (assumed to be an annual average), compared to 115W/m², is roughly between two and three times too big.

Thank you for your reply and your continued insight.

2. c) Sorry my mistake, clearly I misused intensity here.

Question 3) "example" was the wording from the original question. Oh right, I will correct my average value also, thank you for remarking on that.

Can I verify that it would be correct to use an angle of 35 degrees when finding the intensity, as I have become a little uncertain?
 
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  • #32
etotheipi said:
Intensity is another word for energy flux density. But in common (maybe sloppy) parlance, people like to drop the word "density". So you just have to keep your wits about you as to whether someone is talking about the evaluated surface integral (formally flux), or the integrand (formally flux density)!
Yes indeed. In general, we have to be prepared to interpret loosely used terminology in context. It's very difficult for the younger students who have had little exposure to different terminologies.
 
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  • #33
AN630078 said:
Can I verify that it would be correct to use an angle of 35 degrees when finding the intensity, as I have become a little uncertain?
I can't verify that. The wording in the question is unclear. 35º is is simply my best guess using the available information, as I explained in message #21. Is this a written piece of work you have to hand-in? If so precede it with a statement such as:
"The direction of solar radiation relative to the panel is unclear. I have assumed an angle of incidence of 35º".
You will not be penalised if the angle is not 35º because the question is so obviously poorly-worded.
 
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  • #34
Steve4Physics said:
I can't verify that. The wording in the question is unclear. 35º is is simply my best guess using the available information, as I explained in message #21. Is this a written piece of work you have to hand-in? If so precede it with a statement such as:
"The direction of solar radiation relative to the panel is unclear. I have assumed an angle of incidence of 35º".
You will not be penalised if the angle is not 35º because the question is so obviously poorly-worded.
Thank you very much for your reply and for your advice, I admit I will probably use your statement. It is a question my physics tutor sent to me in a quantum physics revision package of questions, but I had not come across a homogenous problem to this before, at least not within the context. If you like, once I have feeback from them I can inform you of the angle demanded by the question. Thank you again 👍😁
 
  • #35
haruspex said:
I worried you might think that, but I assure you not. Hence the Like.
Thankyou!
 
  • #36
AN630078 said:
Thank you very much for your reply and for your advice, I admit I will probably use your statement. It is a question my physics tutor sent to me in a quantum physics revision package of questions, but I had not come across a homogenous problem to this before, at least not within the context. If you like, once I have feeback from them I can inform you of the angle demanded by the question. Thank you again 👍😁
You are welcome. Yes, it would be interesting to learn what the intended angle actually is!
 
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