Differences between Radiation results of LB components

[Arding]

Hello everyone,

I was calculating some PV surface outputs that noticed there is a difference in the Radiation result of “Radiation_Analysis” and PhotovoltaicSurface". So I do a simple test with a cube. As you can see the PV component considers radiation for the bottom of the cube which should be 0(as it is the result of radiation analysis) Also the Number of irradiances in the North direction is nearly doubled.
I would be appriciated if you have faced same Issue or have an Idea how to fix it?

Radition comparison.gh (416.7 KB)

[chris]

Hey @Arding ,

I suggest that you use the LBT 1.6 plugin instead of Legacy Ladybug. The Legacy Ladybug radiation analysis did not include an emissive ground hemisphere, which helps approximate the solar radiation that would be reflected off the ground onto the geometry.

The LBT plugin’s LB Incident Radiation component includes this ground hemisphere as you can see here:

Difference Between "LB Incident Radiation" and "Ladybug Solar Radiation" Components

Good question and this is directly linked to what I said here: In LBT, we do the ray tracing for a full sphere around each point so that we can account for the radiation that’s “reflected” off the ground (technically, we’re doing this by assuming an emissive ground hemisphere that has 0.2 the intensity of the sky hemisphere, much in the same way Radiance does). In legacy, we only looked at the radiation coming from the sky dome, which was ok for some purposes but could be 20% less than expect…

[Arding]

Thank you @chris for your reply,

I used the LBT 1.6 , The result was higher but still my problems remain.

1. why there is a radiation for bottom side. it should be 0 as it is in legacy version, but in PhotovoltaicSurface and IncidentRadiation shows 254kw/m2:
   

   

2. I’m using PhotovoltaicSurface regularly. Doing a comparison with pv-sol, notice me this differences. How can I improve accuracy of PhotovoltaicSurface as there is still not new version of it in LBT, or in another word how to use this new result pf LBT 1.6 into old PhotovoltaicSurface component?

Thank you so much