# Photon Simulation

Hi all,

I am simulating a condition where I have an indoor farm with skylights. I want to find out how many photons will be received by the plants in one full day (lets say 22 March). There is a simple conversion between no. of photons and radiation received at the analysis point. I am using girdBasedSimulation with genCumSky.

I have a very basic question - Do I simulate with no. of bounces set to 1 or I keep my no. of bounces 4-6.

If I simulate with more than one bounce the cumulative radiation is more than the incoming radiation in the space, which makes sense because it is adding up from all the bounces. Logically the radiation energy in the room/space cannot be more than the total incoming radiation from the skylight.
I ran a simple box with one bounce and got logical results. The radiation in the box was slightly less than the incoming radiation. However I am confused why bounces should not be considered as the light will bounce and will have energy associated with it.

I hope I could explain the situation. Any expert advice on the physics and how to simulate it using ladybug-honeybee would be of great help.

Thanks and Regards
Saket

After some thinking I came up with the approach to model my surface representing plants as glass and placing my analysis points behind the glass surface so that I can capture how much radiation will be absorbed by the plants.
Pls suggest if there is any other way someone can think of.

Hi Saket,

I would not use glass material as leaves cause under different angles the glass material behave differently, see this https://radiance-online.org//pipermail/radiance-general/2015-February/010726.html , instead use “trans” material.But in general point above (on) the leaves should b fine. Maybe you should look into PAR simulation, it was discussed several times on the forum.

Best
Peter Z

Hi Peter,

Thanks for the input. I agree glass material will behave differently, I should rather use trans material. The aim is to find out how many photons are received by the plants on a vertical wall. Something like this (ignore the lights)

I will look into PAR simulation.

Regards
Saket