status of tonatiuh as of july 2011

• Program background

• Design goals

• Implementation approach

• Current status

• Comparison with SolTrace

• Experimental validation

• Usage example

• Conclusion

• Acknowledgments

Index

Tonatiuh, in Mesoamerican religion, Nahua sun deity of the fifth and final

era (the Fifth Sun). In most myths of the Mesoamerican Nahua peoples,

including those of the Aztecs, four eras preceded the era of Tonatiuh, each

ended by cataclysmic destruction. (Ref.: Encyclopædia Britannica)

Program background

Simulate the optical behavior of solar concentrating systems, providing detailed information regarding the flux distributions incident upon its surfaces.

Design Goal

• Simulate most concentrating systems of interest.

• Be easy to learn, use, and maintain.

• Be easy to improve, and extent.

Design Goal

Design Goal

Tonatiuh

Design Goal

• Full-fledge public Open Source

project

• C++ (object-oriented)

• Leveraging on well established

open source libraries and tools

Implementation approach

Implementation approach

Implementation approach

Implementation approach

video channel

developers blog

users group

main web site

Current status

• Ray tracing and plug-in architecture fully implemented and operational.

• Program able to model a large variety of reflective concentrating systems.

• Users around the world are using it, reporting bugs, and providing valuable feed back.

• Ray tracing and plug-in architecture fully implemented and operational.

• Parallel computation capabilities fully implemented and operational.

• Scripting, dynamic help, and self-updating capabilities in well-advanced development stages.

• Continuous extreme programming development with monthly release cycles consolidated.

Current status

• Able to model a large variety of reflective and refractive solar concentrating systems.

• Successful comparison with SolTrace to the point that Soltraceis evolving to adopt Tonatiuh characteristics (e.g. it is being rewritten in C++, its user interface is being modernize, etc.)

Current status

Since the opening of the

Tonatiuh website in June

2008, it has received 23,496

visits, which came from 147

countries / territories.

Current status

Comparison with

SolTrace

SOLTRACE

• C++ (former Borland

Delphi) Monte Carlo

Ray Tracer

• Windows-based

• Simple GUI

• Commercial use,

closed development

Comparison with

SolTrace

TONATIUH

• C++ object oriented

Monte Carlo Ray

Tracer

• Plug-in architecture.

• Operating system

independent

• State-of-the-art GUI

• Open source

Comparison with

SolTrace

Parabolic Dish Parabolic Trough Solar Furnace

Parabolic dish

Tonatiuh

SolTrace

Power at the target

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

Tonatiuh

SolTrace

Parabolic dish

Frequency distribution of photons

Parabolic dish

Tonatiuh

SolTrace

Maximum flux density

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

Tonatiuh

SolTrace

Parabolic trough

Power at the target

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

Parabolic trough

Tonatiuh

SolTrace

Frequency distribution of photons

10 20 50 100 200 500 1000

0

50

100

Thousand raysDif

fere

nc

efo

rmT

on

ati

uh

refe

ren

ce

va

lue

Maximum Flux Density

Tonatiuh

SolTrace

Parabolic trough

Maximum flux density

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

NREL solar furnace

Tonatiuh

SolTrace

Power at the target

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

Tonatiuh

SolTrace

NREL solar furnace

Frequency distribution of photons

Radius (m)

Fre

qu

en

cy

NREL solar furnace

Tonatiuh

SolTrace

Maximum flux density

Diffe

rence

fro

m T

onatiuh’s

estim

ate

(%

)

• Tonatiuh and SolTrace generate similar estimates

– In the comparison differences never exceeded 2.4%, and were negligible in most cases.

• Both trace similar number of photons to converge in their estimates

– Between 1 to 2 millions, depending on the value being estimated.

SolTrace comparison

conclusions

The general goals of the experimantal validation exercise were:

• To test Tonatiuh’s flexibility to be adapted to simulate real experiments performed on a relatively complex system.

• To test the usefulness of Tonatiuh as a design and analysis tool.

Experimental validation

• To adapt and use Tonatiuh to simulate several experiments that were carried out at the Plataforma Solar de Almería(PSA) during the testing of a secondary concentrator, and compare Tonatiuh’s solar flux estimates with experimental results.

Goals of the experimental

validation

Use as input values to Tonatiuh:

• The appropriate measured values if available.

• Reasonable “a priori” estimates determined without using any experimental results from the secondary concentrator tests to simulate.

Boundary conditions

• Develop a new sunshape plug-in based on a more realistic sunshape model than the pill-box.

• Develop a new shape plug-in to facilitate the simulation of the hexagonal CPC secondary concentrator.

• Define an “a priori” set of input values for each of the test to simulate.

Execution steps

Execution steps

CSR = 30%

Sunshape: Distribution of radiance (W/m2 sr) as a function of the angular distance from the centre of the solar disc.

New, more realistic, sun shape plug-in.

Execution steps

Buie’s sunshape

model

L=f(DNI,CSR)

CSR = 30%

Equivalent probability

density function

CSR = 50%

New, more realistic, sun shape plug-in.

Execution steps

Million of rays

Relative error

standard deviation (%)

New, more realistic, sun shape plug-in.

Execution steps

New shape plug-in to facilitate the simulation of the hexagonal CPC secondary concentrator.

Execution steps

Execution steps

Execution steps

Execution steps

Test # 01

Configuration

Test # 02

Configuration

Execution steps

TEST 01 TEST 02

Date 10-15-1990 10-30-1990

Solar time (hh:mm:ss) 12:18:00 13:15:00

Direct Normal Irradiance (W/m2) 932 975

Sunshape type Buie sunshape Buie sunshape

Circumsolar ratio (%) 0,9 0,9

Transmissivity (%) 100 100

Number of heliostats 2 14

Heliostats reflectivity (%) 87 86

Heliostats optical quality (mrad) 1,55 1,55

Reconcentrator reflectivity (%) 77 77

Reconcentrator optical quality (mrad) 1,55 1,55

Test results

Total Power

(kW)

Average Flux

(kW/m2)

Maximum

Flux (kW/m2)

Measured 31,04 38,32 241,37

Tonatiuh 29,92 36,94 230,80

Relative error (%) -3,59 -3,59 -4,38

Total Power

(kW)

Average Flux

(kW/m2)

Maximum

Flux (kW/m2)

Measured 164,76 203,40 1.050,99

Tonatiuh 174,98 216,02 1.181,39

Relative error (%) 6,20 6,20 12,41

TEST 01

TEST 02

Results: Test # 01

Measured

Tonatiuh

Results: Test # 02

Measured

Tonatiuh

• Tonatiuh has been able to predict the total energy, the average and peak fluxes, and the overall shape of the flux distributions at the exit of the secondary concentrator, using only “a priori” and measured input values.

Experimental validation

conclusions

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 5º

Sun Elevation: 10º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 20º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 30º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 40º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 50º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 60º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 70º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 80º

Usage example:Parabolic Trough Incident Angle Modifier

Sun Elevation: 90º

Usage example:Parabolic Trough Incident Angle Modifier

• Tonatiuh is a flexible an accurate tool for the analysis and design of complex solar concentrating systems operating under real working conditions.

Conclusion

• Since 2004, Tonatiuh’s development is being supported at the University of Texas at Brownsville by DOE and NREL under Minority Research Associate (MURA) Program Subcontract ACQ-4-33623-06.

• Since 2006, it is being also supported by the National Renewable Energy Centre of Spain (CENER), which is contributing the core development team, and providing overall project coordination.

Acknowledgments