[Archived phorum post from squ1.com v2 by Olivier]

Paul,

I am writting you an answer on that.
Will post it tonight.
Thanks.

Olivier

[Archived phorum post from squ1.com v2 by Olivier]

Paul,

A run down of the various values displayed in the Solar Exposure window:

GLOBAL Wh/m2:This is the amount of solar radiation that is incident on a surface tracking the sun.
This value thus does not change with the orientation of your selected surface, since it is only dependant on the location.
Also, note that this is usually the highest value, as it has the advantage of showing "optimized"data.
Useful when you are thinking of potential solar energy collection.

SUN ANGLE (in the hourly exposure): this angle refers to the incident angle of the sun on the surface selected.
This is the angle formed between the sun rays and the normal of surface selected. Hence, it is almost 90 degrees in the mornings and goes down until noon on a horizontal surface.

AVERAGE SHADE: should be what it says: average shading on the surface. I am not too sure how this is calculated as I usually use the overshadowing sunpath to run this type of calculations.

COLLECTED: this is most likely what most people will look for. That is the amount of radiation received per unit area of the surface selected.
In the hourly exposure, the "h" is obviously absent since the data are collected for each hour of the day, hence it is just a Watt/m2.
The last column is the total amount of radiation for the surface collected - no /m2 thingy. It simmply multiply the previous value in W/m2 per the total area of the selected surface.

REFLECT: this one I do not know. Of course, it is probably the one you want to know about
I have never been able to use correctly the reflected componebt of the solar exposure calculation (when selecting "reflected"in the drop down menu). Even tagging the surface as a reflector does not appear to change anything for me. It's all 0 value, so I cannot guess what the column is supposed to represent.
As far as accounting for reflected radiation, the surface should pick up reflection from the ground (assumes a 20% ground reflection). But I said earlier, things don't change much in my results.

I wish I had all the answers Paul. We'll have to see what v. 5.5 has in store for us.

Best,
Olivier

[Archived phorum post from squ1.com v2 by Paul]

Thanks Olivier,

I am getting figures for "reflected" but how they related to the "collected" and for square meters of what - is what I am not sure on. This is critical to my study and so I hope that Caroline or Andrew will be able to get back to me some time soon and hopefully the explanations will be included in the help files sometime.

Paul

[Archived phorum post from squ1.com v2 by Olivier]

Paul,

In theory, I think, the COLLECTED values should include whatever reflected component your selected surface picks up. In addition, the breakdown of it should show up under the REFLECTED column. In that column, the m2 refers to the selected surface: whatever the value under this heading should be the amount of received radiation that was reflected off another plane, per unit area of the selected surface.
Does that make sense?
I still can't have my end figured out - I get nothing.
If you could email me your model, I'd like to have a look to confirm my theory here.
Thank you for your patience Paul.

Olivier

[Archived phorum post from squ1.com v2 by Paul]

yes it makes sense but the numbers don't figure then. The global radiation isn't per m2 of the collector surface and that is why I thought they might follow the same logic with the reflected surface. Hope I get an answer soon as I have an oppertunity to use this alot.

[Archived phorum post from squ1.com v2 by Olivier]

Paul,
The GLOBAL data displayed should be per m2.
Have you been trying multiple weather files, or only one?
What weather file are you using?

Olivier

[Archived phorum post from squ1.com v2 by Paul]

Thanks for the help Olivier,

It is a little pointless guessing what the issue might be if we do not know how, when,where and if the reflected component is added to the collected component. When I get a response on that I can then look at th figures again. The issue is that the maths of the figures just do not add up. I have tested a number of options with the same weather data and when looking at the results the numbers just don't add up in a way that makes sense. The difference in the collected component when the reflected component starts kicking in is not in the same order of magnitude to the reflected component itself. This is very much the case in the single day sim but less so in the monthly sim. I am not looking for difinitive figures just to know what I am comparing in the different design options.

Some help from above would be really great on this one.

Paul

[Archived phorum post from squ1.com v2 by Paul]

can anyone at square one shed some light on this?

[Archived phorum post from squ1.com v2 by raquel]

Hi Paul and Olivier

Unfortunately I don't have an answer for your problem about reflected/ collected. However, I would like to put forward something about Average Shading.

In one of my calculations, I was getting something like:

       	 GLOBAL	   AVG 	REFLECT	    COLLECTED  
MONTH	 kWh/m?	  SHADE	 kWh/m?	 kWh/m?	TOTAL(kWh)
-------	-------	-------	-------	-------	----------
Jan:	   46.4	   100%	    0.0	    7.3	     93.23

for a surface facing northeast, in London.

The values above show that although the selected surface is 100% shaded, it collects 7.3 kwh/m2 of solar radition!!!

If I select Direct Only, the values come up as:

       	 GLOBAL	   AVG 	REFLECT	    COLLECTED  
MONTH	 kWh/m?	  SHADE	 kWh/m?	 kWh/m?	TOTAL(kWh)
-------	-------	-------	-------	-------	----------
Jan:	   46.4	   100%	    0.0	    0.0	      0.00

It seems that Average Shading refers to Direct Solar Radiation only. Have you ever came across this? And, would you agree with me?

Regards
Raquel

[Archived phorum post from squ1.com v2 by Olivier]

Raquel,

Yes indeed, your results are actually quite resonable. The shading does mean how much of the direct is blocked. When you have 100% shading, you might still be getting diffused radiation from the northern sky. Hence when you were calculating Total Monthly radiations, the 7.3 kWh/m2 are solely diffused. It seems a lot because it's a total for the entire month.
Makes sense no?

Olivier

[Archived phorum post from squ1.com v2 by Olivier]

Paul,

The reflected component should show up only if you have a plane tagged as a reflector within your model. Even then, you might not get any values if that solar reflector does not reflect any light onto your selected surface.
I am still assuming that whatever reflected value you might get would be for the selected surface, not the reflector itself.
I will also assume that the total collected for the selected surface includes whatever reflected radiation you get.
Again, I am not able to reproduce this. I place a reflector in front of my selected surface. Check with the solar ray tracing that my surface does indeed receive some reflected components, but then when I do the solar exposure, i do not get any values for reflected. That is strange since you do, and I know of other users who are able as well.
This must be on my end. Although I do not see why.

Olivier

[Archived phorum post from squ1.com v2 by thida]

Hi Olivier,

In solar exposure calculation, why the radiation results are different while i set up different material properties.

I've read S Ex cal accounts for reflectance, but in my calculation, the results are only different by changing Windows(whatever SC, T, r, color (int/ext reflectance) to other opeque materials such as wall, door, panel with whatever reflectance values set up.

Why?
Wht does it means S Ex calculation account for reflectance?

Thank you.
Regards,
Thida

[Archived phorum post from squ1.com v2 by Olivier]

Hello Thida,

Sorry for not jumping on this post, it escaped me

Yes, i think I know what you are trying to say. As I was discussing on a previous post with Paul on Solar Exposure and Refractive Index of Glazing , Ecotect seems to take into consideration the Refractive Index of the glazing while performing solar exposure calculations.

When performing a thermal analysis, Ecotect calculates how much solar radiation enters a zone through glazings and openings, the direct Solar Gains. Since a part of the solar radiation will be reflected by the glazing and thus not enter the zone, the refractive index of the glazing is an important factor and Ecotect accounts for it.

When performing a simple Solar Exposure calculation, Ecotects flags any glazing element and account for their refractive index, as if you were doing a thermal analysis - the program doesn't really know what you really want to do. thus, while on opaque surface the solar radiation might be one figure, it will be a different one for the glazing surface.
The easy way to go around this is to assign a panel in lieu of your glazing, and see how much radiation falls upon it. Ecotect will then see it as an opaque surface and account for the entire amount of solar radiation.

Hope it makes some sense.

olivier

[Archived phorum post from squ1.com v2 by thida]

Hi Olivier,

Quick question, important for me.

Are they the same for a particular surface, "Solar shade % calculated in Solar Exposure & avg shading calculated in sunpath diagram?

when i try to compare at a particular day, one is 100% at noon while the other is 0% at noon?

Can we calculate overshadowing mask on all surfaces in a model for sunpath diagram calculating method?

In solar exposure cal, without doing interzone cal(that is neglect diffuse), solar shading will be correct?

Thanks you.
Best regards,
Thida

[Archived phorum post from squ1.com v2 by Olivier]

Thida,

Yes, the Shading Coefficients of the Sun Path and the Shading % of the Solar Exposure are the same.
One thing you have to remember is to use high resolution (accuracy) to compare the two, as Ecotect uses random ray spraying technique, hence the variation in results when not assigning high accuracy.

have a look at this post on the identical issue, as Answered by Andrew: Shading Calculations. Andrew makes a pretty good argument for the method used.

Also, i have just double check by running both method for an identical surface. While the figures differ slighlty from month to month by a few %, when I pasted the result of the Solar Exposure onto a spreadsheet and averaged the month's % shading, i came to within 0.1% of the Annual Average as calculated by the Sun Path. I used the Full accuracy for both. Pretty darn good.

I would never assume anything is correct before I run a interzonal adj. Calclculation. This creates shading mask for each surfaces on a thermal zone I believe. Keep in the habit of running it.

Olivier

Hello,

Apparently, "the lower a window's solar heat gain coefficient or shading coefficient, the less solar heat it transmits, and the greater is its shading ability". But, if the shading coefficient is the same as the shading %, which is "average shading on the surface", shouldn't it be the other way around? Shouldn't a surface which is less shaded than another transmit MORE solar heat? I'm puzzled...
Can anyone enlighten me, please?
Thank you,
Alice

Hi all,

I am trying to study the reflected radiation projected from adjacent buildings on my target building; I chose single glazed glass material for the whole façade area that faces my target building. So I am assuming that I have to have some reflections on my building. But the value of reflection in solar exposure still appears zero, although by selecting reflection only tab, it shows I have some amount of reflection on my building. Can you please help me to solve this? I need to study the cumulative incident radiation (including reflection) on solar panels which were placed on all the available facades area.

Thanks alot for your help