Solar gain wrong, need urgent hot fix please.

ApacheCalc – Heat loss/gain calculations using CIBSE procedures to determine design heating/cooling loads.
ApacheLoads – Design heating/cooling loads calculations using ASHRAE Heat Balance Method.
huntervu28
VE Graduate
VE Graduate
Posts: 68
Joined: Mon Oct 05, 2009 1:56 am

Solar gain wrong, need urgent hot fix please.

Postby huntervu28 » Wed Sep 01, 2010 8:42 am

I found this result is not logic, see attached image.

2 zones are similar but mirror, selected zone (red) gains much solar energy in..winter :roll: ---- > Peak cooling load will be in winter.
None selected zone has normal result.

Setting : Default North direction, same result in other direction setting.
Climate : Always show this kind of result in every climate file (cold or hot)
Same result when using Ashrae or Cibse method or Dynamic Simulation
Shape : Always get this result when using this kind of shape (torus segment)

Need a hot fix please.

Image

JosephG
VE Graduate
VE Graduate
Posts: 92
Joined: Wed Jan 14, 2009 3:29 pm

Re: Solar gain wrong, need urgent hot fix please.

Postby JosephG » Wed Sep 01, 2010 10:43 am

Without seeing the model myself, it is somewhat presumptive to state that the solar gain must be higher in summer than in winter and that it must follow the fact that the cooling load is higher in summer than in winter. It is entirely feasible that the solar gain is lower in summer than in winter. IES takes into account the angular dependence of glass solar transmittance, i.e. if the sunlight is closer to being perfectly normal with the glass more solar energy will penetrate. I'm not too sure how your model is setup or where your windows are, but it's not necessarily wrong. Maximum solar gain can occur at a different time than maximum cooling load, simply because the maximum cooling load doesn't necessarily depend only on solar gain, it also depends on outside air temperature. We often forget, but there IS solar gain in winter (in no small amount) and it DOES help keep buildings warm.

I suggest running a dynamic simulation (ApacheSIM) to get to the bottom of it. The result is not necessarily wrong, you need to investigate it first.

huntervu28
VE Graduate
VE Graduate
Posts: 68
Joined: Mon Oct 05, 2009 1:56 am

Re: Solar gain wrong, need urgent hot fix please.

Postby huntervu28 » Thu Sep 02, 2010 3:11 am

Perhaps, I should check more.

But solar gain in winter is double than in summer is incredible, how can it happens :cry: .

Window in two zones are the same, at green line in none selected zone. Default material. This test I use hot climate weather, max : 37,7oC on summer, min 9oC on winter.

huntervu28
VE Graduate
VE Graduate
Posts: 68
Joined: Mon Oct 05, 2009 1:56 am

Re: Solar gain wrong, need urgent hot fix please.

Postby huntervu28 » Thu Sep 02, 2010 4:39 am

Got same result in designbuilder (DB) trial.
ApacheSim show same graph.

This result is right

DB zone 2 : http://img137.imageshack.us/i/capture1v.jpg/

DB zone 1 : http://img295.imageshack.us/f/capture2bg.jpg

ApacheSim : http://img180.imageshack.us/f/capture5h.jpg/


Return to “ApacheCalc/Loads”

Who is online

Users browsing this forum: No registered users and 1 guest