Hello guys,
I’m having some issues with Solar Adjusted MRT. In particular it does not seem to work the context function (I am getting the same results, despite I have a control point shaded by a tall building).
Do you happen to know if I am doing something wrong?
I am considering Standing position, 0 angle, above the ground (Z positive) and sky fully generated.
As always I cannot stress enough how good is L+H.
-berardo
Hi Bernardo,
Thank you for reporting. I just did a massive overhaul of this component this past weekend and I found the bug that you mentioned in this discussion. The bug was essentially that the context was not being meshed correctly and it has since been fixed. You can get the new component by syncing with the github or by using the component that is in the attached GH definition.
Also, I should note that a key new feature that has been added in this overhaul is the ability to run a much faster calculation using a method that was developed by the awesome comfort scientists over at the center for the built environment (http://escholarship.org/uc/item/89m1h2dg). The new method gets you results that are very close to that of the full mannequin mesh but in about 1/50th of the time by extrapolating the mannequin geometry down to a set of 9 points and using some coefficients to compensate for the geometry of the human body.
Lasty, I put in options of 3 simplified mannequin meshes for the 3 different body positions (standing, sitting, and lying down). This should allow you to run a faster version of the older method if you so desire. They can be accessed by plugging integers 3,4 or 5 into the BodyPosture input.
Ultimately, the new fast methods are going to allow us to factor in direct solar radiation in the indoor temperature maps that I have been working on:
https://www.youtube.com/watch?v=__cRBh2DGMA&list=UUc6HWbF4UtdKd…
I will post a new tutorial video on the updated solar MRT adjustor and the indoor temperature maps once I finish developing the full workflow to make indoor comfort maps.
Hey Chris,
Thank you very much for your message and thanks for fixing up the bug. I was aware of the CBE paper and their method is great.
I was wondering if you have ever encountered any discrepancies with other models. It seems that the CBE is tailored for indoor conditions, whereas other models are focused on outdoor (for example Rayman Model).
http://www.mif.uni-freiburg.de/rayman/
http://www.mif.uni-freiburg.de/rayman/description.htm
I will dig more into that…
Cheers,
berardo
Bernardo,
I have not delved too deeply into RayMan or done a results comparison from both models but, as I understand it, the underlying principle of the indoor and the outdoor MRT calculation is the same and should be applicable to both cases. Both are trying to estimate the amount of solar radiation that falls on the human body and, in the case of RayMan, this seems to be fed into a human energy balance equation with terms for long wave radiation while, for the CBE Tool, they pull out just the terms of this equation that has to do with direct/diffuse solar radiation to give an MRT delta off of an an existing MRT from long wave radiation.
The rayMan method is nice for outdoor because you usually have no idea of the longwave radiation from outside surfaces but, for indoor, you usually have accurate MRT already from an energy simulation so all that you need is a delta. As I understand it, this is the only major thing that makes the tool suited to indoor vs outdoor. For using the Ladybug tool, I caution that, if you start having a lot of context surfaces in outdoor cases, it is really important to try to get an accurate starting longwave MRT instead of using the air temperature. Ryaman seems to have ways of doing this long wave calculation and I think I will create some workflows in the future that use the outdoor surface temperature from E+ simulations to help with this.
In any case, with all of this taken together, the geometry and exact position of the human body usually ends up being very important to estimating an exact MRT delta for solar radiation and, as a designer or engineer, it can be very difficult to know this for your real-world case since all that the occupant has to do is tilt their chair. This is one of the main reasons why I started this component with a mannequin that showed where the radiation was falling on the person so that everyone could be aware of the assumptions. So, given this large uncertainty, I would take any of the results of a solar temperature estimator with a significant margin of error from the real-world case (maybe 10-20%) and just use it to get a sense of the order of magnitude change that the sun produces. Both Rayman and, the CBE method, and the Ladybug component should all fall withing this margin of error and order of magnitude.
I hoe this was helpful,
-Chris