Glaring Study
Solar Glint and Glare by Reflection of Solar Panels and other reflective surfaces
Content
• Regulations
• Definition of Glaring
• Reflection on surfaces
• Examples of glaring
• Glaring calculation
• Glaring survey
• Glare-reducing measurements
Regulations
• FAA Technical Guidance for Evaluating Selected Solar Technologies on Airports(Form 7460)
§
Regulations - criteria
• Duration of the Glaring Hazard is the most important criteria
– maximum glare duration per day (e.g. 30 minutes)
– cumulated glare duration per year (e.g. 30 hours)
• Magnitude of the glare is less important, sun reflection almost always = disability glare
• Measurement / Simulation for single points of interest §
Definition of Glaring
• Disability GlareThe generally accepted metric for disability glare is the equivalent veiling luminance
• Discomfort GlareA nuisance measured on the deBoer‘s Scale
Reflection on Surfaces
reflecting surface
sun ray
Scattered light
Reflection
exit angle
angle of incidence
transmission & absorption
Examples
• Dazzling of highway traffic
• Dazzling of air traffic control towers
• Train driver not able to recognize a train signal
• neighbor disturbed by the glare of a large-scale PV plant
Solar Glare Calculation
• Duration during the year
• Duration during one day
• Angle to line of vision
• angle between sun and reflection
• size considerations
• distances and travel time considerations
Topography
Orientation of Surface in the space
Elevation
75 °
Azimuth
45 °
h1
6,0 m
h2
9,9 m
W
13,0 m L
4,0 m
© Zehndorfer Engineering Consulting e.U.Blend-Rechner V 3.2.2
Ground View (not to scale) Profile View (not to scale)
Calculation Model
Glare Occurrence
8:00
9:00
10:00
11:00 12:0013:00
14:00
15:00
16:00
5:00
6:00
7:00
8:00
9:00
10:00
11:0012:00
13:00
14:00
15:00
16:00
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18:00
19:00
0
10
20
30
40
50
60
70
-120 -90 -60 -30 0 30 60 90 120
Sun
Ele
vati
on
[°]
Azimuth [°] (east = negative)
Glare Occurrence
Winter
Summer
Horizon
Scattering
Core Time
Blend-Rechner V 3.2.2
© Zehndorfer Engineering Consulting e.U.
Graph Copy 4
POI 1
PV A
Glaring days
Date H1 23.3.-21.6.
Date H2 21.6.-19.9.
Time 10:47-13:12
Zone UTC+1
Glare Duration
0
20
40
60
80
100
120
140
Jän Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez Jän
Min
ute
s p
er
day
Glare Duration [min]Blend-Rechner V 3.2.2 © Zehndorfer Engineering Consulting e.U.
POI 1
PV A
total scatter direct
per year 272 177 95 h
max/day 120 75 45 min
Line of Vision
-30
-20
-10
0
10
20
30
40
-40 -20 0 20 40 60 80
Cockpit View
sun
scatter
direct
PV
Blend-Rechner V 3.2.1
© Zehndorfer Engineering Consulting e.U.
POI 3
PV A
heading 135°
day 31.5.
time 16:17
distance 115m
Glare-Sun 45°
Glare-LOV 35°
Glaring Frequency
Solar Glare Assessment
• calibration of locations
– PV Plant
– Points of Interest
• Solar Glaring Calculation
– What if? Iterative Process
– Angle, Locations, Shading
• Interpretation and Evaluation
Glare-reducing measurements
• Change of the reflecting surface
• Shading of the reflecting surface
• Shading of the point of interest
• Change or orientation
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