[esp-r] Re: climate and snow

[Ida Auråen]

Thank you all for replying!

Your answers gave me the information I needed.

I appreciate your help!

Best Regards
Ida Auråen


2013/5/24 Jeffrey D. Spitler <spitler at okstate.edu>

>  Ida,
> It has been probably 10 years since I looked at the esp-r surface heat
> balance and transient conduction routines for the surrounding ground.  But,
> at that time, the answer was "no"  - it did not model the effects of snow
> by either changing the reflectivity of the surface or by accounting for the
> insulating effect of snow.  I strongly suspect this is the case for most or
> all other building simulation tools.
>
> If you are only interested in getting an answer for a particular building
> in a particular location, you can STOP READING HERE and hope that someone
> else will give you some more useful advice!  But, since I am involved in
> related research, I have a few thoughts on the matter...and am always
> interested to find out that I have missed some published work in the area,
> don't know about an unpublished technique or method, there is a better way
> to do it; I am plain wrong, etc.!
> Then, from my perspective, the basic issues are:
>
> (1) You need to have weather data that would support this kind of
> calculation.  I have looked at a lot of the EnergyPlus weather files for
> the USA and while there are fields for precipitation, in many cases they
> just have zero values.  On the other hand, I think you mentioned Östersund
> in an earlier message - I checked the IWEC-2 data file for Östersund and it
> does have precipitation depth in liquid equivalents, including values for
> hours that are below freezing.  With that, it would at least be possible to
> estimate when you have snow fall.
>
> I suspect one reason for the paucity of freezing precipitation data is
> that you need a heated rain gauge to measure precipitation "correctly" in
> sub-freezing conditions; heating the rain gauge can introduce other errors;
> at least here, automated surface observation stations tend not to have
> heated rain gauges because of the power requirements.  That doesn't explain
> why there is a shortage of any precipitation data in weather files here in
> the USA, though.
>
> (2) From an energy calculation standpoint, a typical snowfall year is
> problematic for calculating heat loss from the basement or foundation.  In
> many locations, a year with an early snowfall will have much different
> ground heat transfer than a year with a late snowfall.  This seems to be
> highly random for many locations.
>
> (3) To automatically predict, in a building simulation tool, when you
> would have snow and how much snow would be present and what its insulating
> value would be, you would need a full snow accumulation/melting model.  We
> have done this for bridge deck snow melting systems:
>
> Liu, X., S.J. Rees and J.D. Spitler. 2007. *Modeling Snow Melting on
> Heated Pavement Surfaces Part I: Model Development*. Journal of Applied
> Thermal Engineering. 27:1115-1124. ****
>
> Liu, X., S.J. Rees and J.D. Spitler. 2007. *Modeling Snow Melting on
> Heated Pavement Surfaces Part II: Experimental Validation*. Journal of
> Applied Thermal Engineering. 27:1125-1131.****
> and then later applied it to look at what is needed for prediction of
> undisturbed ground temperatures; I view this as a precursor to predicting
> disturbed ground temperatures - the issues are basically the same, though
> we found that disturbed ground temperatures could also be influenced by
> shading from the building in some of our work related to foundation heat
> exchangers:
>
> Xu, H. and J.D. Spitler. 2011. *Importance of moisture transport, snow
> cover and soil freezing to ground temperature predictions.* Proceedings
> of the Nordic Symposium on Building Physics. May 2011.
>  (I should also note that we found freezing and thawing in the ground to
> be important.)  Modeling of snow accumulation and melting is
> computationally demanding and would take some time to implement in any
> building simulation program.  It may well be that some clever individual
> has developed an approximate algorithm that is faster and "good enough".
> If so, I would be quite interested to hear about it.
>
> I am also very interested to hear if anyone else is involved in related
> research.  Ida - I am sorry not to have a more immediately helpful answer.
>
> Best wishes,
> Jeff Spitler
>
>
> ****
>
>
>
>
>
>
>
> On 5/24/2013 7:41 AM, Ida Auråen wrote:
>
>  Hi,
>
> I have a question regarding climate file and snow.
>
> If you are modeling a building in a cold climate where there is snow lying
> on the ground a significant time of the year, will ESP-r take this into
> account?
>
> Snow will insulate the ground and minimize the depth of frozen ground. The
> snow will also reflect solar radiation well and it will contribute to more
> passive solar heat through windows or to solar collectors/pv-panels.
>
> Is there snow on the ground for the simulations done in ESP-r in colder
> climates?
>
>
>  Best Regards
>
> Ida Auråen
>
>
> _______________________________________________
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>
>
> --
> Jeffrey D. Spitler, PhD, PE
> Regents Professor and C.M. Leonard Professor
> School of Mechanical and Aerospace Engineering
> Oklahoma State Universityhttp://www.hvac.okstate.edu
> Ofc: 405-744-6578
>
>
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