[BLDG-SIM] eQuest Dbl Skin Sim

CHEOL-SOO PARK gt7296c at prism.gatech.edu
Mon Feb 2 10:18:15 PST 2004


Dear list members,

Based on what I have learned from my recent Ph.D. thesis work on double-skin 
systems, please allow me to add my opinion to the discussion. 

1. Modeling  
As far as I know, there is no specific simulation tool developed for the 
system. That's part of the reasons that many researchers and scientists have 
developed so far their own simulation models which can be found in 
publications. For those who asked about the modeling, I want to mention some 
of publications within my reach as follows: 

  - Gratia, E. and Herde, A.D. (2004), Natural ventilation in a double-skin 
façade, Energy and buildings, vol.36, no.2, pp.137-146
  - Gratia, E. and Herde, A.D. (2004), Optimal operation of a south double-
skin facade, Energy and buildings, vol.36, no.1 pp.41-60
  - Manz, H. (2004), Total solar energy transmittance of glass double façades 
with free convection, Energy and buildings, vol.36, no.2, pp.127-136
  - Manz, H. (2003), Numerical simulation of heat transfer by natural 
convection in cavities of facade elements, Energy and buildings, vol.35, no.3, 
pp.305-311 
  - Park, C.S. (2003), Occupant Responsive Optimal Control of Smart Facade 
Systems, Ph.D. thesis, College of Architecture, Georgia Institute of 
Technology 
  - Saelens, D. (2002), Energy Performance Assessment of Single Storey 
Multiple-Skin Façades, Ph.D. thesis, Katholieke Universiteit Leuven 
  - Grabe, J. (2002), A prediction tool for the temperature field of double 
facades, Energy and buildings, vol.34, no.9, pp.891-899 
  - Cho, S.H., Shin, K.S., and Zaheer-Uddin, M. (1995), The Effect of Slat 
Angle of Windows with Venetian Blinds on Heating and Cooling Loads of 
Buildings in South Korea, Energy, Vol.20, No.12, pp.1225-1236 
  - Rheault, S. and Bilgen, E. (1990), Experimental Study of Full-size 
Automated Venetian Blind Windows, Solar Energy, Vol.44, No.3, pp.157-160 
  - Rheault, S. and Bilgen, E. (1989), Heat Transfer Analysis in an Automated 
Venetian Blind Window System, Journal of Solar Energy Engineering, Vol.111, 
No.1, pp.89-95 

Some of the above models are very detailed and for instance developed with 3D 
CFD simulations, whereas others are simple and lumped. But, a higher level of 
detail is not always better and in many cases even counterproductive as the 
required level of model complexity is dependent on the user's need. In my 
thesis work, I developed a lumped model for determining optimal control (of 
louver slat angle and airflow regime in the cavity) applied in an on-line and 
real-time control system. Using full 3D CFD models for this purpose would be 
an example of "over-engineering". I found that the lumped model, calibrated 
through in-situ experiments, is surprisingly accurate, stable, and very 
adequate for optimal control and performance studies. 

2. Economic aspect of the double-skin facade systems
One chapter in my thesis discusses performance comparison of an optimally 
controlled double-skin system (System I), a static double-skin system (System 
II, louver angle and airflow regimes changed manually without any optimization 
algorithm), and a conventional double-pane window system (System III) in the 
climate of Atlanta and Chicago. For this comparative study, I developed a set 
of performance indicators in the areas of energy, visual and thermal comfort. 
It was concluded that System I is most advantageous, but much to my surprise, 
System II is not always superior to System III in terms of energy. Thus, it 
was concluded that when designing/operating a double-skin system, intelligence 
is not an option but a must if energy saving is the target. One other thing I 
would like to stress here is that the control system responds to user 
preferences and changes in weather and environmental inputs, leading to 
improvements in visual and thermal indoor comfort, the economic benefit from 
which is hard to translate in terms of dollars. 


An on-going Ph.D. thesis work at Georgia Tech conducts techno-economical 
feasibility studies on whole building scale. The study will also address the 
optimal design of the double-skin facade systems in different climates and 
constrained by characteristics of the buildings.  Please find more detailed 
information on the Georgia Tech double skin facade research group website: 
http://sfdu.arch.gatech.edu

Looking forward to sharing your experience and opinions, 

Best Regards

Cheol-Soo Park, Ph.D.
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