Hi everyone !
As one of my latest message on this Forum I’m doing a tool for the firm to do quick studies for PV installations and modules. My aim is to improve it, and I wish to consider the reflexion of the different materials composing the nearest urban context, I’m sure it change the final results of the AC Energy. And I’m thinking that it impacts directly the annual shading. But how considers it ? Changing the Albedo ?
Normaly I found a way to define different material and different reflexion but I’m not sure how to assign material to its reflexion …
Here is a screenshot of this part (sorry, for confidential reasons I can’t give the Programm …)
Thank you a lot !
I leave this to people who know more about this topic.
cc: @djordje, @AntonSzilasi
Thank you very much @mostapha !
Hi @benjamin.grouteau,
I can’t help you with Honeybee.
I am sure Anton will also give you quite good answer on Honeybee generation components.
As for Ladybug Photovoltaics components:
They are based on PVWatts model, where “annual shading” accounts for direct irradiance only. Here is result example from “Sunpath shading” component which calculates it. It basically tries to replicate the annual shading calculation of measurement tools as SunEye.
“_albedo” input affects the ground reflected irradiance.
It represent an average hourly albedo (fraction of reflected irradiance in comparison to received one) that your “_PVsurface” can ‘see’ around itself. For example if there is some water area behind the “_PVsurface”, it will not be ‘seen’ - not receive the reflected irradiance from it.
Most photovoltaics softwares just set the albedo value to same average annual value, as 0.2, as this is somewhat an average annual albedo of the materials in urban conditions (grass 0.25, concrete 0.4, asphalt 0.05…). As reflected irradiance affects the final AC power output quite ‘weakly’, this assumption is justifiable.
However, in higher latitude areas (where optimal tilt angles are larger) plus/or higher altitude areas (where there is presence of snow on the ground during the year), the impact of albedo can be ‘stronger’.
If you do not add anything to the “_albedo” input, it will generate an hourly values corrected for the presence of snow.
If you can generate albedo of the surfaces that surround your _PVsurface input through Honeybee, you can add them into the same “_albedo” input, to account for some other affects (water body, or metal roof…).
Sorry if this was not the reply that you have been asking for.
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@djordje thank you for your patience !
If I well understood what you explained, the context is “seen” as an opaque surface isn’t it ? And the Albedo in cities which considers only the ground, does not impact very much the energy provided by PV Installation.
In the next link, I read that it’s possible to modify the reflectance of the context for EnergyPlus Simulation. Do you think by changing this and runing the simulation,we can take the total energy to input it on the “photovoltaics Performance Metrics” ? Perhaps in this way we can obtain the optimal System Size taking considering the urban context not as opaque surface …
[Reflectance of Shading Surfaces in EnergyPlus]
I just started working on Grasshopper, Ladybug and Honeybee only for two months, I try to understand everything ^^
Thank you
Hi Benjamin,
No problem.
You mean when annual shading is calculated with “Sun path shading” component?
Sorry if I misunderstood you.
The ground, but also all horizontal surfaces around the PV panels. For example: flat roofs around it. Sorry for not being precise in the previous post: so ground-reflected should actually be: horizontal surface reflected.
But in general, yes, you are right.: it can be said that the albedo does not significantly address the annual AC output. You can actually test this by yourself, by trying to supply a single value, duplicated 8760 times to the “_albedo” input.
I can’t comment on Energy Plus, I haven’t been working with those components.
The optimal system size, from “Photovoltaics Performance Metrics” will actually calculate the size of which system would fulfill the required power demands defined through “ACenergyDemandPerHour_” input.
Hi Djordje,
Yes I mean when annuel shading is calculated with “Sun path Shading” component 
I’ll try this to see the Impact of the Albedo on my programm !
Ok I see what you mean, I’m not really sure this consideration can be done for our project because we wish to use the Programm in order to have real good assessment of the Output energy of a PV Installation. Thus, we can help the architect to design sustainable building.
Thank you very muchfor all these informations !
Hi Benjamin,
Okay, then the answer to your previous quesiton:
The buildings and other non-transparent structures are opaque. The trees, have transmission index which defines how much direct radiation is allowed to pass through them. “Sunpath shading” component uses some default values for these transmission indices, for coniferous and deciduous in-leaf/leaf-less periods during a year. We literally copied them from Deutsche Gesellschaft Für Sonnenenergie (Dgs), Dec 2007.
You can change them through “Sunpath shading” inputs, but I assume you can stick with those default ones already defined.
Download the Ladybug Photovoltaics example files, and open the 020_Photovoltaics shaded analysis.gh file. It will contain an already internalized geometry of some of the trees.
You would have to connect the components, but there are explanations and arrows for that.
If you do not exceed, let us know.
Ok all is clear now, thank you very much !
What I’m suggest for the futur of the “sun path shading” tool and other Tools which consider the urban context as shading, is to allow user changing the reflexion and the transparence of the context. Indeed, for some cases the reflexion is to important to be not neglected, especially if we have some curved Surface near a PV Installation.
Thank you again for all the Information !
