Surface Slope Error (error de pendiente)

[e k]

Hello,

I am using Tonatiuh for optical analysis of Parabolic Dish/Stirling
systems and I was wondering if there is a correlation between the
variable "m_sigmaSlope" in Tonatiuh and slope error measurements in
"mrad".

In order to perform realistic optical analysis, I have used values for
m_sigmaSlope that result in spillage (desbordamiento) values similar
to ones found experimentally (between 14-15%). However, trying to
relate that value of m_sigmaSlope to slope error (mrad) is slightly
more difficult as I have seen different values anywhere between 3 to 8
mrad...

So is there any relationship in Tonatiuh between the two variables?
And if not, is there perhaps another way of describing how the
m_sigmaSlope variable is defined?

Thank you in advance,
Elliot

[e k]

Just a follow up, in a paper by Iverson, Andraka et al. (Sandia Labs)
from last year's SolerPACES program, they say that it is typical to
combine all types of optical errors (structural alignment, tracking
errors, surface slope errors, material reflectance, etc.) into a
single RMS error parameter.
-Un poco más: en un artículo de investigadores de Sandia Labs de
SolarPACES de 2010, han mencionado que es normal que se combinen todas
las fuentes de errores del concentrador (alienación, seguimiento,
pendiente, reflexión, etc.) en un sólo parámetro de error RMS (raíz
cuadrática media).

I have not used CIRCE2 or SolTRACE before, but I know Tonatiuh has
been validated against SolTRACE, so I assume that parameters are
handled in similar ways; is "m_sigmaSlope" the *overall* error
parameter then, that encompasses all of these other (both random and
systematic) errors?
- No he usado los programas CIRCE2 ni SolTRACE nunca, pero sé que
Tonatiuh ya se ha validado/confirmado en ensayos mediante SolTRACE, y
supongo que se definen los parámetros de Tonatiuh de una manera
parecida; ¿es el "m_sigmaSlope" entonces el total de todos los demás,
y que abarca los errores (ambos al azar y sistemático)?

If so, then it makes sense that the value I have used in Tonatiuh to
achieve spillage results similar to experimentally-obtained values
(~14-15%) is near to a "typical" value for total error described by
Stine and Harrigan/Stine and Geyer in "Power from the Sun":
http://www.powerfromthesun.net/Book/chapter08/chapter08.html

But that would indicate that the value I used for the "m_sigmaSlope"
variable, which is near to the 6.7mrad given in the source above, has
units of milliradians (mrad)...
- Si es así, el valor que he usado para "m_sigmaSlope" sería parecido
a un valor "típico" para los sistemas de discos parabólicos dado en el
libro "Power from the Sun"...pero también, eso significaría que
"m_sigmaSlope" tiene unidades de milliradianes (mrad)...

Does that sound about right?
¿Es correcto entonces?

Gracias de antemano,
Elliot

[Manuel J. Blanco]

Dear Elliot,

You are right in your analysis. In the current version of Tonatiuh sigma-slope has to be entered in milliradians and not radians. This is an inconsistency since in other parts of the program angles are entered in radians.

In principle the sigma-slope integrates the mirror quality and slope-error.

Best regards,

Manuel