The art of fine control

Transcription

FINE
CONTROL
AND
NATURAL
VENTILATION
© WindowMaster – Solutions for Natural Ventilation
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VKR Group Structure
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Why are we here?
WindowMaster , through research and development over the last 20 years has established itself as
an authority on Natural Ventilation control, and market leader in energy efficient intelligent
solutions delivered in over 500 projects.
WindowMaster window actuators, and facade integration
Fine control with 2 way positional feedback. Unique MotorLink technology
mm x mm opening to provide fine control
3 speed actuators including ‘silent’ operation
Programmable anti entrapment control
Window controls specialists and indoor climate consultants with in house expertise
WindowMaster complete services for complete proven solutions
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What is Natural Ventilation?
Where the indoor climate of the building is controlled by fresh air intake
through openings within the facade that open automatically to provide single
sided or cross ventilation for a stable indoor climate and good air quality with
minimum heat loss through use of
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Opening windows and roof lights
Louvres
Windcatchers or chimneys
Hybrid solutions using mechanical ventilation
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Natural Ventilation
A History of Control
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The Problem with Natural Ventilation…
Natural Ventilation?
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too hot!
too cold!
too stuffy!
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Draughty!
high energy bills!
unpredictable results!
Naturally ventilated BSF projects using 300% more energy than expected
Manual Windows – do they really do the job?
Good design, but poorly specified or value engineered
Installed automated systems that can introduce more problems than they
solve?
Acoustics?
Health?
Security?
Perceived performance improvement in SBEM using Mechanical
systems…though at what cost?
The answer?
Well designed buildings and controls
Fine control....solution based, not product based
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The Need For A Stable Climate
User comfort
Insufficient
air change
Optimal window/opening position
Draught and cold problems
Air change
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A stable climate?
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A stable indoor climate is essential for productivity.
Incremental movements significantly reduce noise and
disturbance.
Precise control of the ventilation prevents draughts.
Precise control provides consistent
and even spread of ventilation.
Precise control of natural ventilation
provides a comfortable and
invigorating environment for all the
occupants of the office.
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How to Achieve Natural Ventilation
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Natural Ventilation is achieved through controlled openings in the
external facade of the building, which on the basis of different
indoor and outdoor conditions regulate the indoor climate by means
of:
Wind pressure
Temp. differences
Shape of the building
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Poor Control of Natural Ventilation
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The human temperature and air quality sensor
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Reactive
Heat loss and additional energy costs
Heat and purge (fully open/closed)
Modulating control based on
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Zone temperature no external drivers for wind pressure
Closing windows during rain....no ventilation
Product only based solutions
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Windows
Louvres
Windcathers/Chimneys
Hybrid Solutions
Complex difficult to understand control systems.....the result
Manual or mechanical solutions
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Controlling Natural Ventilation
Manual Control
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Lowest cost option – depends on the user operating the windows at the
correct times and by opening the correct amount….
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Research has shownCO2 levels can reach up to 4,000ppm in winter because the natural
response to cold outdoor temperatures is to leave windows closed.
Beisteiner, A & Coley, DA (2002) Winter Time Ventilation Rates in UK Schools. Centre for Energy and the Enviornment, University of Exeter
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Teachers are there to teach – do they want to open and close each of 4
windows in a class 40 times a day?
If opened too much or left open it can have a significant impact on heat losses
and therefore energy consumption
Security
No Night Cooling
The potential consequences – poor air quality
disruption to occupants
high energy useage
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Manual Control of Windows?
Temperature
Source: 2009 KONTROLLIERTE FENSTERLÜFTUNG – PILOTPROJEKT SCHULHAUS UNTERMOOS
Werner Hässig and André Galli
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Manual Control of Windows?
CO2 in Winter
Source: 2009 KONTROLLIERTE FENSTERLÜFTUNG – PILOTPROJEKT SCHULHAUS UNTERMOOS
Werner Hässig and André Galli
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Calculations
with Jannick Roth MSC
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Wind
VWind
Pref =
-
Vref ●
+
+
+
-
1
⋅ ρu ⋅ Vref 2
2
P2 = Cp 2 ⋅ Pref
P1 = Cp 1 ⋅ Pref
Positive Cp values (between 0 and 1)
Negative Cp values (between -1 and 0)
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Thermal Buoyancy and wind – several openings
Pressure differential over opening j :
THERMAL BUOYANCY
WIND

∆P j = P j - Pi =  C pj ⋅

1
2
⋅ ρ u ⋅ v ref
2
(
+ ρ u ⋅ g ⋅ H 0 ref − H j

 − Pi
) ∆T
T 
i

Reference Height H0 ref:
Typical neutral plane determined by mass balance
Vref
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Pu Pi
y
y
P
H0 ref
y
∆P
v
H
j
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Air Exchange Rates by
Thermal Buoyancy and Wind
0 °C
2 °C
4 °C
6 °C
8 °C
10 °C
12,0
10,0
Air change h-1
8,0
6,0
4,0
~5 l/s per person
2,0
0,0
0
2
4
6
8
10
12
Wind speed m/s
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CFD calculation - why?
Why: Weather is dynamic
A comfortable indoor climate depends on a precise control of
windows opening. The controls specialist should calculate a Cp
value for each window from wind pressure from different wind
directions.
Based on the Cp-values the required opening area / opening
degree is calculated for each wind direction and speed in order
to get the necessary air change in the building.
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CFD calculation - why?
Complex building design
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CFD calculations - why?
Complex building design + surroundings
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Pressure/Cp reading
Wind: NE
Wind: SE
Wind Speed m/s
Zone
Zone 27
1
5
5
5
5
5
5
5
5
N
324
NE
335
E
335
SE
317
S
323
SW
323
SW
322
NW
320
Cp 0
Cp 45
Cp 90
Cp 135
Cp 180
Cp 225
Cp 270
Cp 315
-0.06
0.96
0.96
-0.64
-0.13
-0.13
-0.19
-0.32
This provides the required degree of opening to achieve a certain air change
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CFD simulations - surroundings
Without surroundings
With surroundings
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CFD simulations
Without surroundings
With surroundings
Wind
Wind
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Ejbyskole in DK (school)
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Importance of Fine Control –
Opening distance vs Air flow
Results from Wind Tunnel tests on the specific windows, carried out by WindowMaster.
180
96%
160
91%
140
70%
46%
120
Volume flow (m3/hr)
73%
65%
100
80
60
40
20
0
0
30
10mm
60
50mm
90
120
150
180
210
240
Chain length (mm)
Bottom-hung inward
Top-hung outward
Parallel
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The Importance of Fine Control
● The importance of the first 5 cm of window opening for Natural Ventilation
● Control within this area is essential for:
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10mm
Control of temperature and C02
Control noise
Reduction of Draughts
Improved Security
Night Cooling
20mm
30mm
40mm
50mm
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Fine Control and Acoustics BB93
● Sound insulation at different opening distances
Sound
reduction[dB]
[dB]
Lydisolering
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30
25
20
15
10
5
0
0
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240
Åbningsgrad
Degree
of opening[mm]
[mm]
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Fine Control and Night Cooling
● Optimised Night Cooling with
restricted openings
● Windows located high within
façade
● Windcatchers/roof windows for
cross ventilation and mixed night
cooling strategies
● Potential use of louvres in high risk
areas
● Use of internal courtyards
● Use of PIR sensors/CCTV with
direct link to automatic controls
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Oerestad High School
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Danish architect: 3XNielsen
Size: 12,500 m2
Has been occupied since August 2007
Coordinated control of light and air
Opening windows and vertical louvres
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Oerestad High School – Innovative
Design
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Oerestad High School – Ventilation
Principle
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Oerestad High School – Opening
Distances
• Window opening distances in October 2007 and March 2008
Average opening distances
[%]
Opening distances
100
80
60
October 07
March 08
40
= 2.5 cm
20
0
Motorlines facing the Metro [-]
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Oerestad High School – Measured
Temperatures
• Recommendation in British Standard (BB101): Maximum 120 hours
above 28° C
• Recommendation in Danish Standard: Maximum 100 hours above 26°
C and 25 hours above 27° C
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Oerestad High School – Measured
Temperatures
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Specifying Controls for Natural
Ventilation
Conclusion
● Good building design
● Analysis required for both design compliance and fine control strategies
● Solution design based not led by one specific product with considerations for
● Location
● Acoustics
● Security
● One controls solution for Natural Ventilation with single point of responsibility
● Strong specifications
● Proof of ability to comply with specification through
● Live data logging
● Post occupancy evaluation
● Client testimonials
● Performance specifications to be ‘specific’ not vague
● Value engineering not cost cutting that devalues the design intent
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Any questions?
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The art of fine control

Transcription

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