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iat-cener / tonatiuh

A Monte Carlo ray tracer for the optical simulation of solar concentrating systems
http://iat-cener.github.io/tonatiuh/
GNU General Public License v3.0
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Tonatiuh's Irradiance #77

Open DAPB opened 8 years ago

DAPB commented 8 years ago

Hi, My name is Daniel Barros and I am student at Instituto Superior Técnico, Lisbon, Portugal and I am using Tonatiuh in my Thesis. So, I would like to know if the accepted irradiance is horizontal or is it normal to the surface. And also, if there is a script function that has the irradiance as a parameter.

Thank you and have a nice day.

ilescener commented 8 years ago

Hi Daniel,

I guess you are asking for information about the "Irradiance" field which appears in "Environment/Sun Light/Define Sun Light...". Before explaining that, it's important to know the differences between Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI) and Global Horizontal Irradiance (GHI), although I'm pretty sure you probably know all of this stuff. The DNI is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky, the DHI is the amount of radiation received per unit area by a surface that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmosphere and comes equally from all directions, and finally, the GHI is the total amount of radiation received from above by a surface horizontal to the ground, it means that GHI = DHI + DNI * Cos(zenith). As we can see, de DHI is not defined in one direction so in concentrated solar system has not repercussion at all. The GHI is only useful for surface that are always placed horizontal to the ground, not the typical surface that we can find in a system which usually track the sun and try to maximize the total amount of irradiance received. And in last instance, GHI is a function of DNI and zenith angle. Consequently, the irradiance term used to characterize the sun is and must be always the DNI value. I hope it's clear now.

About the scripting, there is a function to assign the sun parameters: SetSunshapeParameter( QString parameter, QString value )

As an example of how to define a completely sun model:

tonatiuh.SetSunshape( "Pillbox_Sunshape" );
tonatiuh.SetSunshapeParameter( "irradiance", 500 )
tonatiuh.ChangeSunPosition(  180, 60  );

If you want to know more information about script functions you can find them all in the wiki following this link: https://github.com/iat-cener/tonatiuh/wiki/Script%20functions

Kind regards Iñigo

DAPB commented 8 years ago

Thank you very much for the swift response, it was most kind and helpful.

Daniel Barros