# Homework Help: Incident Solar radiation on an inclined surface

1. Feb 21, 2012

### tommy060289

1. The problem statement, all variables and given/known data

Hey everyone, as part of a final year project I am looking at the economic feasibility of solar panels and whilst I have solar data for radiation intensity on flat surface, longitude (and plus or minus 15°) and 90° Im trying to find a calculation of intensity at any given angle.

Ive been looking in books and they do sort of give and answer but Iv'e been struggling to understand the books for this section and haven't been successful in gaining a real equation. Also, the equation seem to relate to when really little info is known. I already know the intensity of m^2 of flat ground. So what I'm trying to find is if it's possible to calculate the intensity on an incline given that 0° intensity is known.

2. Relevant equations

This is what Im trying to figure out, if there is a direct equation from known 0° to any desired angle

3. The attempt at a solution

I've been looking in books and on the internet but have struggled to understand there description. Im looking for some personal help to help me figure this out!

2. Feb 21, 2012

### tiny-tim

hi tommy!
If you think about it, the intensity falling on any surface is the same as the intensity (not) falling on the shadow of that surface.

So just find the relationship between the area of the surface and the area of its shadow on flat ground.

3. May 23, 2012

### johnvanboxel

Hi Tommy,
I teach atmospheric physics and pretend to know something about the subject.
There is not one simple equation to do the conversion. But the problem is solvable, with a reasonable accuracy.
There are a lot of input parameters, but most can easily be obtained:
Date, Time (and time zone), Latitude and longitude, slope angle, orientation of the slope (=azimuth) and a few more that are less important and of course the global radiation (the radiation measured on a horizontal surface.
I could send you a student report on a similar problem, I could send you a report writeen by me, discussing the theory and I could put the equations in a spreadsheet, so you can play with them. To find me Google for "John van Boxel".