[esp-r] Re: Proposed development of window shading models

[Jon Hand]

Re: email for window shading systems....

There are several issues that would be useful to discuss:

a) Blinds imply the possibility of either user or automated control
    actions and there are several people in the development community
    who have an interest in enabling better control of blinds and other
    aspects of optical properties.  

    Currently optical controls are held in the zone tmc file and options
    for what can be sensed and what can be actuated are frustratingly
    different than they are for other zone controls.  And when surfaces
    are added or deleted from a zone these contols sometimes fail.

b)  Between-glass blinds are one of the simpler cases. Traditionally
    one adds a layer within the construction and associates appropriate
    optical properties (e.g. a roller blind). The solution technique tracks
    the solar radiation absorbed by the blind layer and it would be useful
    to discuss whether the proposal is to extend this approach.

    If blinds are within the room and the blinds change physically what should the
    rest of the solution domain recognise as the surface or surfaces
    that make up the blind?  Are the blinds aggregated within the surface that
    is transparent or are they explicit surface(s) within the room with full
    interaction with the surrounding zone.

    When blinds get hot one should observe long wave exchanges as well at 
    the solar band distributions.  In the proposal what, specifically is it that
    the other surfaces interact with for the various flux exchanges?

    After the simulation has run users might wish to enquire as to the state of the
    blind.  And how does one report on the energy balance?   What blind-related
    information might be useful to record for later analysis?

c) Blinds on the outside of the building are also delightfully
    complex in their physics - one might expect exterior blinds
    to impact both the near-building air temperature and the short-wave
    and long wave environment at the facade.  Some work was done
    in other research projects and whether what was learned elsewhere
    can be incorportated would be useful to talk about.  How would
    the proposal interact with the current shading analysis tool?

d) How is the proposed method different than what is being carried
    out in WIS?  Window 6 from California includes some blind descriptors
    so what can be learned from these other approaches? 

    Is this a replacement for externally generated optical
    properties sets?  Is this proposal to work in conjunction with
    current optical properties within esp-r or to have an alternative
    path or as a replacement?

e) Blind geometry and possible rotations and transforms are currently 
    not included as descriptive fields in the model files (only the aggregate
    change in optical properties).  Is the proposal to re-form the matrix
    as required to account for a different geometry within the zone?

f) Those looking at designs such as double skin facades will probably
   bring up the issue of treatement and control of blinds within partitions.

g) Facade engineers will probably be interested in how actions of
    blinds create different resistences to air flows within rooms and
    in the case of blinds suspended within double skin facades.

h) The current optical properties database probably needs to evolve
    to support the description of blinds (actually lots of things need
    to evolve in terms of optical properties). Horizontal and vertical blinds will
    introduce direct-to-diffuse flux optical issues that are covered by the
    calculations in WIS - similar ideas are probably needed.
  
It would be great if materials could be made available for use in
discussions at the developers conference later this month.  Of course
it someone from Canada could come along to the conference and
join in the discussions that would be even better!

-Jon Hand

-----Original Message-----
From: esp-r-bounces at lists.strath.ac.uk on behalf of Bart Lomanowski
Sent: Mon 3/12/2007 3:29 AM
To: esp-r at lists.strath.ac.uk
Subject: [esp-r]  Proposed development of window shading models
 
Hello All,

In response to Jon's reply...

I am a Master's student at the Solar Thermal Research Lab at the University of 
Waterloo. Our group has developed window shading models focusing on the 
accurate treatment of venetian blinds in glazing systems. 

The models essentially extend a standard center-glass glazing analysis to add 
venetian blinds of arbitrary geometry, slat angle and position within the 
glazing system. The analysis is based on calculating spatially averaged, or 
effective solar optical and longwave properties for a shading layer given a 
specific geometry and slat surface reflectance. A multi-layer solar optical 
analysis determines the absorbed, transmitted and reflected components of 
incident beam (off-normal) and diffuse solar radiation. Next, a heat transfer 
analysis, including the absorbed solar radiation terms, determines all the 
radiative and convective fluxes and layer temperatures. A convection 
correlation has been developed for a between-the-panes venetian blind. 

Proposed ESP-r development:
The development, still in the early stages, aims to create an "advanced glazing 
systems" facility giving the user the freedom to specify any glazing/shading 
arrangement . The optical properties for glazing/shading systems would be 
calculated based on the insolation data per time-step, allowing for accurate 
solar energy accounting. Convective and radiative heat transfer across air gaps 
would be treated in more detail than the current air gap resistance 
approach.    

These models will pave way for the development of intelligent automated blind 
systems. 

The method of implementation is still in the early stages so there is still 
uncertainty about code interventions at this time. I anticipate that the 
subroutines MZSLGN, MZCOE1 and MZSETU will require extensive work, however, the 
plan is to create new subroutines for handling advanced glazing systems.

I look forward to discussions on the subject.

Regards,
Bart Lomanowski




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