News

Tonatiuh release 1.2.6 is now available!

This new version of Tonatiuh incorporates the following relevant new features:

• A new wizard-type plug-in that facilitates the simulation of solar tower systems. The wizard generates a heliostat field taking as input from the user: (1) a text file with the coordinates of the center of the bases of the heliostats that compose the heliostat field and (2) a component Tonatiuh file describing the geometry of the heliostats (it is assumed that the geometry of all heliostats are the same).
• Several new atmospheric transmittance plug-ins.
• A new reflectance material plug-in, which allows the user to independently define the slope error and the reflectivity ray error of a mirror-like surface.
• The possibility for the user of selecting which of the surfaces in the scene should not be taking into account during the ray tracing process.
• The resolution of a bug that made the program crash when the user tries to "undo" the elimination of a One-Axis tracker.
• The resolution of a bug associated with the definition of the Sun position using the SunPositionCalculator window (the error is related to an incorrect conversion from degrees to radians).

Overview

The Tonatiuh project aims to create an open source, cutting-edge, accurate, and easy to use Monte Carlo ray tracer for the optical simulation of solar concentrating systems. It intends to advance the state-of-the-art of the simulation tools available for the design and analysis of solar concentrating systems, and to make those tools freely available to anyone interested in using and improving them. Some of the most relevant design goals of Tonatiuh are:

• To develop a robust theoretical foundation that will facilitate the optical simulation of almost any type of solar concentrating systems.
• To exhibit a clean and flexible software architecture, that will allow the user to adapt, expand, increase, and modify its functionalities with ease.
• To achieve operating system independence at source level, and run on all major platforms with none, or minor, modifications to its source code.
• To provide the users with an advanced and easy-of-use Graphic User Interface (GUI).

Features

The use of extended Open Inventor files to represent the "scene" (i.e. the solar concentrating system, the sunlight model, etc.) An advance and easy-to-use GUI providing:

• 3D and tree views of the "scene" to simulate.
• Handlers and manipulators to modify and query scene objects using 3D views.
• Interface elements to manage the undo and redo of user actions.
• Interface elements to define de type of Monte Carlo ray tracing to execute.

• Add new sunlight models.
• Add new geometric surfaces.
• Add new reflective materials.
• (planned) Add new refractive materials.
• (planned) Add new photon map and other results analyzers, and post-processors.
• (planned) Add new spectrum models.

Requirements

As any other ambitious open source program, Tonatiuh uses and leverages on several existing open source libraries, and tools. The principal open source resources used by Tonatiuh are:

• Nokia QT for the Graphic User Interface (GUI).
• Coin3D Toolkit for 3D Graphics Visualization.
• Marble generic geographical map widget and framework.
• CPPUnit for testing the code.

Tonatiuh's output files format

Tonatiuh’s output file is a binary file whose format is independent of the host computer's operating system. The file stores real values one after the other in a block, with no spaces, separators, carriage returns, or line feeds separating the values. The binary format used to store the values is Real64 with big-endian byte ordering. The first value stored in the file is the power per photon in watts (W). This real value is then followed by seven-tuples of real values, one per photon . Every seven-tuple holds the following values in the specific order given:

• PhotonID
• x-coordinate
• y-coordinate
• z-coordinate
• surface side ( 0 if is back side , 1 if is front side )
• Previous PhotonID (0 if the photon is the first of a given ray)
• Next PhotonID (0 is the photon is the last of a given ray)

At CENER we use either Mathematica or R applications for post-processing of Tonatiuh's output binary files, in order to transform raw photon data into flux distributions estimates, and to present those fluxes estimates as graphs.

A typical Mathematica snippet for reading a Tonatiuh output file could be:

(* Function to Read Tonatiuh's binary output file *)
ReadTonatiuhResults[filename_] := BinaryReadList[ filename, "Real64",  ByteOrdering -> +1];

(* Read Tonatiuh's ouput file and store content in fileData *)
rawData = ReadTonatiuhResults["fileName.dat"];

(* Store the power per photon in powerPerPhoton *)
powerPerPhoton = rawData[[1]]
 
(* Create a matrix storing all the photon seven-tuples at a row per seven-tuple *) 
photonMap = Partition[fileData[[2;;Length[fileData]]],7];

numberOfPhotons = Length[photonMap]
 
....

A typical R snippet for reading a Tonatiuh output file could be:

#Open binary data file.
fileName<- file("filePath/fileName.dat", "rb")

#Store the power per photon in poerPerPhoton variable.
powerPerPhoton <- readBin(fileName, what="numeric", n=1, endian="big")

#Create a vector with photons all the information.
endOfFile<-FALSE
photonData<-vector( mode="numeric")
while( !endOfFile )
{
   photon<-readBin(fileName, what="numeric", n=7, endian="big")
   if( length( photon ) < 7 ) endOfFile = TRUE else photonData<-append( photonData, photon )
}
#Close the data file.
close(fileName)

#Compute the number of photons in the vector. all the photon sextuples at a row per #sextuple 
nPhotons<-length( photonData ) / 7
photonMap<-matrix(  photonData , nrow= nPhotons, ncol=7, byrow=TRUE )

...

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