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

17:00

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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