[Radiance-general] Greenhouse energy modeling

[Christopher Rush]

Hi Valerie,
Are you primarily doing electric lighting calculations (rather than daylight) for real manufactured light fixtures? Do the manufacturers provide IES photometric data in human vision lumens and candela?

The radiance tool ies2rad converts IES files into radiance data and geometry. There is a multiplier option for that command that could create the radiance light source definition in photosynthesis units rather than visible light units. For example if your source provides 0.003 Watts PAR per lumen (*), and you’re using an IES data file that’s based on visual lighting units, you could apply -m 0.003 to the ies2rad command and then work in Radiance as usual from there as if it were any other light source. Any results you have that would typically report lux (if you had not used the multiplier) would instead be reported in W/m² PAR since you provided the conversion in the front end in setting up the light source definition.

However you should take more care if you can’t work with equal spectrum material definitions. If you need reflective or transmitting materials that have colored reflectance and varying PAR properties across the spectrum, you might need something more complicated than above.

* disclaimer: I hope I’m conveying the concept here correctly, but I don’t know if this is a realistic conversion factor – just tried to make something up roughly based from Wikipedia

-Chris



From: Valerie Tan [mailto:vlt26 at cornell.edu]
Sent: Wednesday, August 02, 2017 2:19 PM
To: radiance-general at radiance-online.org
Subject: [Radiance-general] Greenhouse energy modeling


Hello,



My name is Valerie Tan and I am a undergrad designing greenhouse energy modeling software for the Cornell Controlled Environment Agriculture group. I am a computer science major (Cornell Engineering, Class of 2019) working for the Cornell CEA group with Kale Harbick (researcher) and Kevin Ye (also an undergrad). I am new to using the Radiance libraries and have questions on the features and capabilities of Radiance. I have been, and will continue to look through tutorials, archived mailing lists and presentations.



We are implementing a ray-tracing and energy modeling component of the NYSERDA funded GLASE project. See https://glase.cals.cornell.edu/<https://secure-web.cisco.com/1SKjFONMt9byWzA9S9ADQZ0p1y2eIkClhW_NBkxGkDeAcXXWk8dgMJnJp76a8kbr-G11WDx_MJZJhuuJGiFfHJdb3WeIUgQiHfA3blgs8haqOQaf16HndOxJQvF79dsZtQ0enZ1oLB5ucfun0Sm2jJj2j7881SD7Ck8Tblw4cffzGxLr3CmAOANg8HtOhY2d3XXfmF6C-H8Jj3wcqVJNi_FwZczYGZOw-fLylWsKwgomxjgAS6Pk3sIoRY4jIk5ZFWv4jtMy_773Z6AsdpEHbCw/https%3A%2F%2Fglase.cals.cornell.edu%2F> for a brief synopsis.



I was given a big task of designing software that models a greenhouse and calculates the total amount of light (from all directions, not just one direction as in backwards ray-tracing) that reaches particular sample points, given the geometry, weather, time of day, artificial light configurations, etc. Imagine a typical greenhouse, with glass panels that reflect and refract light, and a rectangular plot where you grow the plants. We want to pick sample points on that rectangular plot and figure out how much energy reaches that point. Ultimately, we want to model and optimize everything such that all areas of the growing area receive optimal and equal amounts of light.



My main question is, how do I make light calculations in micromoles instead of lumens or RGB values? From what I've seen, Radiance appears to have this type of focus, but I could be entirely wrong. (This is my first research position and that I am still in the learning process of understanding technical descriptions and tutorials.) The issue with lumens and RGB values is that they are calibrated for human vision and are very difficult to work with in terms of plant science, while micromoles measures the actual number of photons. It looks like the "Photon map extension user manual" from the website (https://www.radiance-online.org/learning/documentation/photonmap-user-guide<https://secure-web.cisco.com/1oBqhvNcvvnKBsnXUz3WOQvxiumTnewUCZDdwFua-KClDBlzaNwMBKLpONUQlkL8xzQoP2qjE_OwZls1DJY8VzH9DLbgnRR1LAgLGO-7D-wgtR91DdakdecZfI8T0mYp7Pr26oEjqgjXaO70KCyDPivYqbnmzYCURvhAddOWtG4kMihXZhiML3nHbrE-bBKIz_duRZ7ou14UENzb6fhnZETGdl4RU7Dqetkn_QtxLCF3hwAhujhwPL__6YqwYM_Dj/https%3A%2F%2Fwww.radiance-online.org%2Flearning%2Fdocumentation%2Fphotonmap-user-guide>) is a possible solution.



I really appreciate any kind of advice on using the Radiance libraries. Thank you for your time and hope to hear from all of you.



Best,



Valerie

--
Valerie Tan
Computer Science
College of Engineering
Cornell University '19

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