BIG60MILLION LTD BOTWNNOG SOLAR FARM GLINT …

BIG60MILLION LTD

BOTWNNOG SOLAR FARM

GLINT ASSESSMENT

AUGUST 2015

Wardell Armstrong Baldhu House, Wheal Jane Earth Science Park, Baldhu, Truro, Cornwall, TR3 6EH, United Kingdom Telephone: +44 (0)1872 560738 www.wardell-armstrong.com

Wardell Armstrong Baldhu House, Wheal Jane Earth Science Park, Baldhu, Truro, Cornwall, TR3 6EH, United Kingdom

Telephone: +44 (0)1872 560738 www.wardell-armstrong.com

ENERGY AND CLIMATE CHANGE

ENVIRONMENT AND SUSTAINABILITY

INFRASTRUCTURE AND UTILITIES

LAND AND PROPERTY

MINING AND MINERAL PROCESSING

MINERAL ESTATES

WASTE RESOURCE MANAGEMENT

DATE ISSUED: AUGUST 2015

JOB NUMBER: CA10881

REPORT NUMBER:

BIG60MILLION LTD

BOTWNNOG SOLAR FARM

GLINT ASSESSMENT

AUGUST 2015

PREPARED BY:

Craig Donlevy

Renewable Energy

Consultant

APPROVED BY:

Adrian Lea Technical Director

This report has been prepared by Wardell Armstrong LLP with all reasonable skill, care and diligence, within the terms of the Contract

with the Client. The report is confidential to the Client and Wardell Armstrong LLP accepts no responsibility of whatever nature to third

parties to whom this report may be made known.

No part of this document may be reproduced without the prior written approval of Wardell Armstrong LLP.

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GLINT ASSESSMENT

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CONTENTS

1 INTRODUCTION ................................................................................................................... 1

2 ASSESSMENT APPROACH ..................................................................................................... 2

2.1 What is Glint? ............................................................................................................................. 2

2.2 Guidelines .................................................................................................................................. 4

2.3 Methodology .............................................................................................................................. 7

2.4 Reflectivity ................................................................................................................................. 7

2.5 When can Glint Occur? .............................................................................................................. 9

2.6 Summary .................................................................................................................................. 11

3 BASELINE CONDITIONS ....................................................................................................... 13

4 KEY EFFECTS ....................................................................................................................... 14

4.1 Glint Receptors and Effects ...................................................................................................... 14

4.2 Effect on Residential Housing .................................................................................................. 15

4.3 Historical Buildings and Features ............................................................................................. 21

4.4 Effect on Public Rights of Way ................................................................................................. 24

4.5 Effect on Public Roads.............................................................................................................. 25

4.6 Effect on Railways .................................................................................................................... 29

4.7 Effect on Airfields & Aircraft .................................................................................................... 29

4.8 Cumulative Effects ................................................................................................................... 30

5 SUMMARY ......................................................................................................................... 32

6 REFERENCES ...................................................................................................................... 34

TABLES

Table 2.1: Definitions of Glint, Glare and Dazzle .................................................................................... 4

Table 4.1: Listed Buildings within the Potential Ground Based Glint Zones ......................................... 22

Table 4.2: Aerodromes within 15km of the Site ................................................................................... 29

FIGURES

Figure 1.1: Google Earth Image Showing Site Boundary (© 2014 Google; Image © 2014 Get Mapping

plc)........................................................................................................................................................... 1

Figure 2.1: Types of Reflection, Specular or Glint (left), Diffused or Glare (right) (Federal Aviation

Authority, 2010) ...................................................................................................................................... 2

Figure 2.2: Glint Ocular Hazard Plot (Sandia National Laboratories 2014) ............................................. 3

Figure 2.3: Solar Farm Adjacent to the Runway at Dusseldorf Airport (Aviation Pros, 2013) ................ 6

Figure 2.4: Solar Array next to Gatwick Runway (Business Green, 2013) .............................................. 7

Figure 2.5: Reflectivity of Common Materials (Sunpower Corporation, 2011) ...................................... 8

Figure 2.6: Number of Daylight and Sunshine Hours per Month in the UK.......................................... 10

Figure 2.7: Sun Path Diagram (Sun Earth Tools 2015) .......................................................................... 10

Figure 4.1: Receptors Close to the Site (© 2015 Google) ..................................................................... 15

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Figure 4.2: Listed buildings shown in Green with development boundary shown in Red. .................. 21

Figure 4.3: Showing the Public Rights of way (shown in Yellow). ......................................................... 24

Figure 4.4: Image Travelling on the Unnamed Road which Runs South-North, from Llandegwning to

Mynytho (© 2014 Google) .................................................................................................................... 26

Figure 4.5: Image Travelling South-North from llandegwning to Botwnnog with the proposed array

located to the East. (© 2014 Google) ................................................................................................. 27

Figure 4.6: Image Travelling East-West on the unnamed road running from Bryncroes to Nanhoron.

(© 2014 Google) ................................................................................................................................... 28

Figure 4.7: Airfields around the Site and Military Low Fly Zones ......................................................... 30

APPENDICES

Appendix 1: Zone of Theoretical Visibility and Ground-based Glint Zones

Appendix 2: Individual Receptors – Glint Analysis

Appendix 3: Mathematical Calculations

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1 INTRODUCTION

Big60Million Ltd is proposing to install a 5MW solar farm approximately 12acres in area on

land to the south east of Botwnnog, Llŷn Peninsula.

Information has been requested about the effects of glint caused by the proposed

development, which could be perceived as a potential nuisance at receptors in the vicinity

and as a potential threat to aircraft safety.

The site is located approximately 900m southeast of the village of Botwnnog and

approximately 4.7km northwest of the town of Abersoch. The site lies under the planning

authority of Gywnedd Council. The British National Grid Reference of the centre of the site is

226930:330640 Figure 1.1: Google Earth Image Showing Site Boundary (© 2014 Google;

Image © 2014 Get Mapping plc) below shows the proposed site area.

Figure 1.1: Google Earth Image Showing Site Boundary (© 2014 Google; Image © 2014 Get

Mapping plc)

The proposed solar panels would be fixed at 15 degrees to the horizontal. Varying the angle

of the proposed panels would have an impact on where/when any glint may occur. This

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assessment will assume a uniform horizontal panel angle of 15 degrees facing due south in

order to assess where ground based glint may occur.

2 ASSESSMENT APPROACH

2.1 What is Glint?

Glint, glare and dazzle are often used interchangeably but are defined in this report as

described below and shown in Figure 2.1.

Glint – Also known as a specular reflection, this is produced as a direct reflection of

the sun on the surface of the solar panel. It occurs with the reflection of light from

smooth surfaces such as glass, steel and calm water.

Glare – A scattered reflection of light. Glare is significantly less intense than glint and

is produced from rougher surfaces such as concrete, tarmac, and vegetation.

Dazzle – An effect caused by intense glint and glare, which can cause distraction, and

if strong enough reduce the ability of the receptor (pilot or otherwise) to distinguish

details and objects.

Figure 2.1: Types of Reflection, Specular or Glint (left), Diffused or Glare (right) (Federal

Aviation Authority, 2010)

Due to the intensity of glint being much higher than glare, this report will focus on glint alone.

The perceived intensity of glint will vary depending on the ambient light level and direction

and distance to the receptor.

The intensity of any perceived glint by an observer may be separated into three categories

based on retinal irradiance and the subtended source angle as shown in Figure 2.2 below.

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Figure 2.2: Glint Ocular Hazard Plot (Sandia National Laboratories 2014)

In simplified terms the most hazardous category of glint as shown in the red section of Figure

2.2 is only possible when light is being focussed onto the eye which would only normally be

possible from solar PV concentrators, although it could be theoretically possible if an array

had panels at differing angles. The yellow section can be caused by reflections being received

from multiple panels simultaneously and would only normally be experienced close to the

array.

It is worth mentioning that different organisations and agencies refer to the glint and glare

events interchangeably and Table 2.1 summarises the definitions and shows how they relate

to the definitions used in this report.

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Table 2.1: Definitions of Glint, Glare and Dazzle

Organisation Organisations Terminology Our Terminology

Sandia National

Laboratories

The term “glare” represents the specular direct

reflection of sunlight off smooth materials such

as solar panels and does not account for the

diffuse component.

The Sandia software

uses the term “glare”

which our report

defines as “glint”.

Federal Aviation

Authority

“Glint is referred to as momentary flash of

bright light and “glare” is defined as continuous

source of bright light. Specular reflection is

caused by reflections from smooth surfaces

while diffuse reflections are from rough

surfaces.

Our terminology is in

agreement with this

definition of glint as a

momentary flash of

bright light caused by a

specular reflection.

Building

Research

Establishment

“Glint” and “dazzle” are used when referring to

sunlight reflected from a glazed façade.

Although not explicitly mentioned this is

referring to specular reflections.

Our terminology uses

the term “glint” in place

of “glare” and “dazzle”

as used by BRE.

2.2 Guidelines

In the UK at the domestic level the closest guidelines regarding this issue are the BRE

guidelines on Glare and Dazzle (Building Research Establishment, 1991), which are primarily

used in conjunction with glass or mirror fronted buildings. These state:

"Glare or dazzle can occur when sunlight is reflected from a glazed facade. This

can affect road users outside and the occupants of adjoining buildings. The

problem can occur either when there are large areas of reflective tinted glass

on the facade, or when there are areas of glass which slopes back at up to 35°

from the vertical so high altitude sunlight can be reflected along the ground,

solar dazzle is a long-term problem only for some heavily glazed (or mirror clad)

non-domestic buildings. A glazed façade also needs to face within 90° of due

south for significant amounts of sunlight to be reflected".

In the domestic setting the guidelines state that glare and dazzle are only issues if the facade

(or panel in this case) is within 35 degrees of the vertical or 55 degrees of the horizontal.

Beyond this angle, incident light will be reflected primarily skywards. This is because the angle

of reflection of light from a point source will always be the same as the angle of incidence.

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The fact that this incident light will be reflected skywards is of principle concern for aircraft.

The health and safety of passengers and crew on flights into and out of airports is of

paramount importance and it is therefore critical to demonstrate that the effects of the

proposed solar farm will not compromise this.

In 2010 the Civil Aviation Authority (CAA) issued interim guidance on Solar Photovoltaic

Systems on and near to licensed aerodromes while formal policy was being developed (Civil

Aviation Authority, 2010). This covers development:

“Principally on or in the vicinity of licensed aerodromes but will also include

guidance on installations away from aerodromes (or ‘en-route’).”

‘Vicinity’ in the above statement is defined as within 15km of an aerodrome. The proposed

solar farm is not within 15km of any aerodromes, noted in Figure 4.1. The closest licensed

civil aerodrome is EGOD Llanbedr located 30km to the East of the development. Therefore,

no known unlicensed civilian aerodromes are within 15km/”vicinity” of the site boundary.

The CAA identified the key issue as being:

"perceived to be the potential for reflection from SPV (solar photo-voltaic) to

cause glare, dazzling pilots or leading them to confuse reflections with

aeronautical lights.”

It gives the following articles of the Air Navigation Order that should be considered.

Article 137 - Endangering safety of an aircraft.

Article 221 - Lights liable to endanger.

Article 222 – Lights which dazzle or distract.

It is not considered that there is opportunity for pilots to confuse reflections with aeronautical

lighting. The times when aeronautical lighting is lit and is most prominent in the pilot’s view

are times when there are low light levels such as at night-time or when weather conditions

like cloud or fog reduce visibility. At these times panels will produce no glint or glare due to

low light levels. The CAA has not yet adopted formal policy regarding this issue.

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Further work by the US Federal Aviation Authority (FAA) in their Solar Guide (Federal Aviation

Authority, 2010) incorporates a chapter on the impact and assessment of glint from solar

panels. It concludes that (although subject to revision):

“…evidence suggests that either significant glare is not occurring during

times of operation or if glare is occurring, it is not a negative effect and is a

minor part of the landscape to which pilots and tower personnel are

exposed.”

The geometric analysis included later in this report (full details in appendix 3), which defines

the extent and time at which glint may occur, is suggested by the FAA as a method of

evaluating potential glint effects.

There are a considerable number of large-scale solar installations that are already operating

and located near to airports. These include Newquay Airport and Dunsfold Aerodrome. Figure

2.3 shows a large scale solar farm similar to the proposed scheme constructed at Dusseldorf

Airport, glint from the solar farm has not affected flight operations.

Figure 2.3: Solar Farm Adjacent to the Runway at Dusseldorf Airport (Aviation Pros, 2013)

A ground-mounted array of solar panels has also been installed at London Gatwick on land

adjacent to the runway and taxiway (see Figure 2.4 ). Consultation was undertaken between

the developer and the Gatwick aerodrome safeguarding team, National Air Traffic Services

(NATS), and NATS (En Route) Plc (NERL) (Crawley Borough Council, Planning Ref:

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CR/2011/0602/CON). These consultees did not object to the proposal on any grounds

including glint.

Figure 2.4: Solar Array next to Gatwick Airport Runway (Business Green, 2013)

It is not expected that the potential for glint generated by the proposed solar farm at

Botwnnog could cause any serious operational effects to aircraft but since the position of the

sun in the sky and the angle of the panels will be known, it is possible to predict exactly when

there would be any chance of effecting a particular flight path and hence it would be possible

to forewarn any pilots.

2.3 Methodology

A geometric analysis was conducted to study where and when glint events may occur. This

looks at receptors present at ground level, such as dwellings, roads, public rights of way and

railway lines. The study also assesses the potential for glint to effect aircraft operating near

the site using a tool developed in the United States by the Sandia National Laboratory.

2.4 Reflectivity

Solar PV panels are designed to absorb light. Their primary function is converting light into

electrical energy so any light that is reflected is a sign of inefficiency. The glass which coats

solar panels is specifically designed with a low iron content to aid the absorption of daylight

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and thus has a much lower level of reflectivity than the glass typically seen in conventional

windows. This means that less than 9% of the total incident visible light is reflected, while

normal glass reflects approximately 17%. Thus reflectance levels from a given solar site are

much lower than the reflectance generated by standard glass and other common reflective

surfaces as indicated in Figure 2.5.

Figure 2.5: Reflectivity of Common Materials (Sunpower Corporation, 2011)

Solar panels have a comparable reflectivity to that of calm water and considerably lower than

that of snow. Any glint that may occur would be no worse than that seen when flying over a

reservoir on a calm day or a snow covered landscape on a bright day.

It has been raised as an issue that the solar PV panels themselves may not be the only source

of reflection from a solar farm. Although the steel mounts used to support the panels could

reflect sunlight the frames are well shaded by the solar panels above them and any exposed

elements on the end of rows cover an extremely small area. Due to being mounted vertically,

reflections will be directed into the ground.

As distance from the glint source increases, the intensity of the event drops appreciably. This

is due to both the diffraction of light after it reflects off the panel and atmospheric conditions

such as the presence of particulates, haze or low cloud.

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2.5 When can Glint Occur?

Glint can only occur when direct sunlight can reach the solar panels. Diffused lighting, caused

by weather conditions such as cloud, fog, and mist, cannot cause glint due to the low energy

intensity of the light incident on the panels.

In the UK, average daily sunshine hours range from between one and two in midwinter to

between five and seven in midsummer. Figure 2.6 shows the total number of daylight hours

available each month (red) based on the site’s location. Also shown is the average number of

hours of sunshine each month (blue), taken from Met Office data recorded over a 85 year

period at Valley Meteorological Station between 1930 and 2015 (this is the closest active Met

Office weather station to the site). The Valley Meteorological Station is approximately 47km

from the site and is expected to be broadly representative of the weather conditions that the

site will be expected to experience.

Figure 2.6 also shows the ratio of sunshine to daylight displayed as a percentage (green) for

each month in the UK. As can be seen, the sunniest month on average was May with just over

223 hours of sunshine. Even then, the actual incidence of glint events can only be expected

to be just over 45% of the theoretical maximum. This is because the ratio of sunshine to

daylight is approximately 45% at this time. During less sunny months glint events may occur

for as little as 19.8% of the theoretical maximum because the ratio of sunshine to daylight is

much less at these times.

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Figure 2.6: Number of Daylight and Sunshine Hours per Month in the UK

Figure 2.7: Sun Path Diagram (Sun Earth Tools 2015)

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

45.0%

50.0%

0.00

100.00

200.00

300.00

400.00

500.00

600.00H

ou

rs p

er m

on

th

Sunshine Hours Daylight Hours Sunshine as % of Daylight

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A key fact to remember is that any glint can only be experienced at one point at any time. This

is because the panels are all fixed at the same angle and orientation. The point which

experiences glint slowly tracks - as the sun rises and falls - across the sky and ground. It moves

from the west to directly above or slightly behind the site depending on the time of year and

then to the east. This track changes daily as the suns position varies throughout the year.

The sun diagram (Figure 2.7) shows the pattern of sun movement across the sky relative to

the site location for the summer, spring/autumn and winter solstices. As the angle of

incidence of sunlight is known from the sun diagram the direction of the reflected light (glint)

can be found for any particular moment in time.

In the northern hemisphere the sun appears to rise in the north-east. This is as a result of the

tilt of the earth at the summer solstice. When the sun reaches a sufficient elevation in the sky

to allow sunlight to strike the solar panels ground glint may occur. When the suns angle in the

sky attains a certain value the reflected beam will be directed back into the sky towards the

south-west. Put simply, ground based glint will normally only occur in the early morning or

evening when the sun appears low in the sky. As a result of this glint will only occur in a

relatively small area in an approximate bow tie shape with the solar panels in the centre as

shown in Appendix 1. Glint does not occur during winter months due to sunlight striking the

panels from the front and reflecting upwards. In the evening, with the sun setting in the

northwest, glint may occur to the southeast.

2.6 Summary

The reflectivity of solar panels is considerably less than many other common materials seen

in the built or natural environment. Water bodies such as reservoirs, lakes (and on a calm day

the ocean) have very similar reflective properties to solar panels as seen in Figure 2.5 and

represent much larger areas than that taken up by the solar panels at the site. Pilots are

currently able to fly at low level next to these bodies of water – along with greenhouses and

other reflective surfaces – and car drivers able to drive towards glass fronted buildings

without undue adverse glint effects. For example, aircraft flying out of London Heathrow fly

low and adjacent to many large reservoirs with no difficulty.

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For ground receptors where screening such as vegetation and other buildings obscures views

of the site glint cannot occur. As ground-based glint cannot occur during winter the lack of

leaves on deciduous trees will not affect the level of glint screening.

Those ground receptors that are closest to the site – and thus likely to potentially experience

the strongest reflections – will not experience glint from the whole site due to the first rows

of panels screening those built behind it. In more exposed and elevated positions glint has the

potential to cause longer but less intense events due the effects of light attenuation through

the atmosphere.

At very close distances to the site – when glint is at its strongest - the solar farm will appear

below the aircraft, out of view of the crew. Similarly if climbing or flying away from the solar

farm any glint will strike the underside of the fuselage and will not be visible to the crew.

When aircraft are flying both towards the site and the sun, the sun will offer a much brighter

and longer duration source of intense brightness than reflected glint could ever cause.

The significance of an effect is defined as a function of the receptor’s sensitivity and the

magnitude of the effect. There are no current formal guidelines either within the UK or

internationally as to what constitutes a significant effect. However The FAA, which utilises the

analysis method used in this report, states in informal guidance that it will consider issuing an

objection if the glint has the potential to form a temporary after image, other factors, such as

the direction of frequency of the glint, also play a role in the choice of issuing an objection or

not.

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3 BASELINE CONDITIONS

As identified in Figure 2.5 there is a range of common materials and surfaces that are likely to

cause glint already present in the study area. These include glass in windows, conservatories

or greenhouses, a flash caused by light reflecting off passing vehicles and calm water. It is not

possible to quantify the level of glint currently experienced by receptors in the vicinity of the

proposed site and it is therefore presumed for the purposes of this report that no glint

currently occurs at receptors in the vicinity of the site.

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4 KEY EFFECTS

4.1 Glint Receptors and Effects

Appendix 1 shows the geographical extent of potential ground glint events up to a distance

of 5km. For a glint event to occur on the ground the receptor must be in both the zone of

theoretical visibility (ZTV) and the ground based glint zone. The ZTV is based on 3.0m high

panels, a receptor (viewing) height of 2m and OS Terrain 50 data with a 50m-grid resolution.

The calculated ZTV shows the points where any part of the solar farm is visible from. Only

certain portions of the solar farm can cause glint at points on the ground (for example the

most northerly panels cannot cause glint in the far southern extents of the ground glint zone).

So while a point may lie in both the ZTV and ground glint zone, further inspection of the

orientation of the site and receptor may reveal that it cannot receive glint. The maximum and

minimum azimuth angles used to create the ground based glint zones were calculated and

applied to the site boundary.

The southernmost receptors within the glint zone have much shorter extents than shown in

the drawing as the light reflected from the panels is angled slightly downwards. Conversely

the northernmost receptors are only relevant on surrounding higher ground as glint is angled

slightly upwards.

Receptors would have to be able to see the panels in order to experience glint events and this

may not be possible due to screening from intervening hedgerows, trees, buildings and the

security fence that will surround the site. When the sun is not shining directly onto the panels

due to cloud or mist (approximately 2/3 of daylight hours during the year) it will also not be

possible for glint to occur.

The ZTV shown in Appendix 1 presumes that no screening is present. Inspection of aerial

photography and Google Street view surrounding the site demonstrate that there are a

considerable number of hedgerows, trees and buildings, some of which will block views and

hence glint of the solar farm, meaning views from long distances are less likely. Mature

vegetation is present along a good proportion of the site’s northern and eastern boundary

meaning views of the site from the ground are limited. The receptors shown in Figure 4.1

below are those close to the site and within the potential glint zone (demarked with the white

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lines). These have the highest chance of experiencing glint. Receptors further away from the

solar farm are less likely to be able to experience glint.

Figure 4.1: Receptors Close to the Site (© 2015 Google)

4.2 Effect on Residential Housing

There are a number of properties in relatively close proximity to the proposed solar farm.

Many of these are surrounded by trees and other forms of screening but there will be some

potential for glint impacts to be present at some of these properties.

For the purposes of this assessment where a cluster of properties are present in a small area

a representative observation point has been selected to provide information on the likely

effects that may be observed. Modelling is based on the theoretical observation of a typical

person standing at ground level.

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Observation Point 1

Observation point 1 represents an agricultural building located within close proximity to the

proposed development and is positioned within 20m of the proposed development site as

seen in Figure 4.1. The building is located within the ZTV and ground glint zone suggesting

glint could potentially therefore glint will not occur at this building.

Computer modelling from the given location suggests that glint could potentially occur from

February to September between 05:40-06:50 GMT and 18:00-19:00 GMT and should last for

no longer than 60 minutes per day. The computer model indicates that the glint will be

primarily of a low intensity as seen in Appendix 2. However, there is a potential for a mid-

intensity glint to occur from 17:30 – 18:30 GMT in Feb-march and Sept –Oct.

Observation Point 2

Observation point 2 is representative of the residential property of Felin Isaf. The property

lies approximately 115m east of the proposed development as seen in Figure 4.1 and is within

the ZTV and ground based glint zone, suggesting there is scope for glint to occur.


March - September between 18:00-19:10 GMT and should last for no longer than 30 minutes

per day. The computer model indicates that that any glint experienced at this property will

be of low intensity.

Inspection of aerial imagery shows that the property has natural screening in the form of trees

surrounding its borders and that in reality glint is not expected at this location.

Observation Point 3:

Observation point 3 is representative of the residential property of Caeau. The property is

located approximately 300m east of the site as seen in Figure 4.1 and is within the ZTV and

ground based glint zone, suggesting there is scope for glint to occur.

Computer modelling from the given location suggests that glint could potentially from March

to September, between 17:50-19:00 GMT and should last for no longer than 30 minutes per

day. The computer model indicates that the glint will be primarily of a low intensity as seen

in Appendix 2. However, there is a potential for a mid-intensity glint to occur from 17:30-

18:30 GMT in March-April and Sept –Oct.

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Inspection of aerial imagery shows that the property has natural screening in the form of

woodland located 150m west of the property and that in reality glint will be of minimal levels

at this location furthermore planned screening of this boundary with a new hedgerow will

further reduce any impact.

Observation Point 4

Observation point 4 is representative of the residential property of Bryn Llewelyn. This

residential property is located approximately 680m east of the proposed development as

seen in Figure 4.1 and is within the ZTV and ground based glint zone, suggesting there is scope

for glint to occur at this location.


March to September, between 17:50-18:40 GMT and should last for no longer than 30

minutes per day. The computer model indicates that the glint will be primarily of a low

intensity as seen in Appendix 2. However, there is a potential for a mid-intensity glint to occur

from 17:50-18:30 GMT in March-April and Sept –Oct.

However, upon inspection of aerial imagery further indication suggests that the property has

screening in the form of woodland and treelines to the western and that in reality glint will

be at minimum levels at this location.

Observation Point 5

Observation point 5 is representative of the residential property of Llwyn-Onn. This

residential property is located approximately 1km east of the proposed development as seen

in Figure 4.1 and is within the ZTV and ground based glint zone, suggesting there is scope for

glint to occur at this location.


April to September, between 17:50-18:30 GMT and should last for no longer than 30 minutes

per day. The computer model indicates that any glint experienced at this property will be of

a low intensity.

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Inspection of aerial imagery further indication suggests that the property has screening in the

form of woodland and treelines to the western and that in reality glint will be at minimum

levels at this location.

Observation Point 6

Observation point 6 is representative of the residential property of Nant-Rhiwdar. This

residential property is located approximately 1km east of the proposed development as seen

in Figure 4.1 and is within the ZTV and ground based glint zone, suggesting there is scope for

glint to occur at this location.


March to September, between 17:50-18:40 GMT and should last for no longer than 30

minutes per day. The computer model indicates that the glint will be primarily of a low

intensity as seen in Appendix 2. However, there is a potential for a mid-intensity glint to occur

from 17:50-18:30 GMT in March-April and Sept –Oct.

However, upon inspection of aerial imagery further indication suggests that the property has

screening in the form of woodland and treelines to the western and that in reality glint will


Observation Point 7

Observation point 7 is representative of the residential property of Barach-Bach. This

residential property is located approximately 900m southeast of the proposed development

as seen in Figure 4.1 and is within the ZTV and ground based glint zone, suggesting there is

scope for glint to occur at this location.




a low intensity.


form of woodland and treelines to the western as seen in Appendix 1 and that in reality glint

will be at minimum levels at this location.

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Observation Point 8

Observation point 8 is representative of Gelliwig Farm Caravan Park. The park is located

approximately 1.1km west-southwest of the proposed development as seen in Figure 4.1 and

is within the ZTV and ground based glint zone, suggesting there is scope for glint to occur at

this location.




a low intensity.

Inspection of aerial imagery further indication suggests that the property has natural

screening in the form of woodland completely surrounding its borders as seen in Appendix 2

and that in reality glint will not occur at this location.

Observation Point 9

Observation point 9 is representative of the residential property of Trewen Farm. This

residential property is located approximately 370m west of the proposed development as




mid-March to September, between 04:50 - 06:30 GMT and should last for no longer than 30

minutes per day. The computer model indicates will be of a low intensity.


form of hedgerows and trees along the road to the east which will further reduce any glint

based event.

Observation Point 10

Observation point 10 is representative of the residential property of Dolafon. This residential

property is located approximately 500m west-northwest of the proposed development as



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Computer modelling from the given location suggests that glint could potentially at two time

frames throughout the year, these are from April-May and Between September-October-

November at between 05:30-06:30 GMT and should last for no longer than 30 minutes per

day. The computer model indicates will be of a low intensity.


form of woodland and treelines to the east as seen in Appendix 1 and that in reality glint will



Observation point 11 is representative of the residential property of Gors-Bach-Y-Wynllan.

This residential property is located approximately 1.5km west of the proposed development

as seen in Figure 4.1 and is within the ZTV and ground based glint zone, suggesting there is

scope for glint to occur at this location.




a low intensity.

Inspection of aerial imagery further indication suggests that the property has natural

screening around its entire borders in the form of woodland and treelines as seen in Appendix

1 and that in reality glint will be at minimum levels at this location.


Observation point 12 is representative of the residential property of Llys-Meddyd. This

residential property is located approximately 400m west-northwest of the proposed

development as seen in Figure 4.1 and is within the ZTV. However, not being situated within

the ground based glint zone, there is no scope for glint to occur at this location.

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4.3 Historical Buildings and Features

Figure 4.2: Listed buildings shown in Green with development boundary shown in Red.

This section makes no attempt to assess the historical significance of any of the buildings or

historical assets discussed as this is addressed comprehensively in the archaeology and

cultural heritage assessment. Instead the focus of this section will be on whether there is any

opportunity to experience glint effects at these receptors. Table 4.1 below identifies the

Listed Buildings within the ground-based glint zone.

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Table 4.1: Listed Buildings within the Potential Ground Based Glint Zones

List Entry Name/Description Grade

4310 Church of St Cian II

19644 Poultry House at Rhandir II

19614 Lychgate to Church of St Cian II

4311 Siop Llangian II

19640 Penygraig II

19638 The Lodge at Haulfryn II

19639 The Squash Court at Haulfryn II

19615 Garth II

19637 Pigeon-tower at Haulfryn II

19630 Haulfryn II

19636 Terrace Pavilion at Haulfryn II

4215 Castellmarch II*

4316 Barn to E of Castellmarch II

19334 Bridge at Trewen II

19333 Pont Rhyd-goch II

19331 Coach House and Stables at Plas Gelliwig II

4263 Plas Gelliwig II

20021 Frondeg II*

22787 Pigsty at Frondeg II

4249 Pic-y-parc II

Scheduled Monuments

There are two Scheduled Monuments within 5km of the site that are situated within both the

ground glint zone and ZTV these are (CN207: Mynydd Rhiw Stone Axe Factory and CN102:

Mynydd Rhiw Round Cairns)

The nearest Scheduled Monument is at a distance of at least 3.5km and it is not expected that

glint could occur at this location due to intervening obstacles with regards to buildings and

natural screening in the form of woodlands, treelines and hedgerows.

Listed buildings

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There are twenty Listed Buildings within 5km of the development site, eight of which are

located outside the ZTV and therefore will not receive any glint.

The remaining listed buildings are identified in Appendix 1. Glint would not be expected at

these Listed Buildings due largely to natural screening in the form of woodlands, treelines and

hedgerows.

The only listed building where glint would be expected to occur is ‘Bridge at Trewen’ (Table

4.1 above) this has been previously been considered in the ‘Residential Observation Points

chapter’ as per Observation Point 9 where it is explained that computer modelling suggests

that glint could potentially occur from mid-March to September, between 06:00 - 06:50 GMT

and should last for no longer than 30 minutes per day. The computer model indicates that

any glint would be of a low intensity.


form of hedgerows and trees along the road to the east which will further reduce any glint

based event.

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Figure 4.3: Showing the Public Rights of way (shown in Yellow).

4.4 Effect on Public Rights of Way

Information obtained from Gwynedd Council has indicated 2 public footpaths lie within the

ZTV and ground-based glint zone and the ZTV which are detailed below:

The footpaths to the east of the development located at a distance of at least 20m to

the site boundary of which a length of 200m of footpath lies within the ZTV and ground

glint zone. Computer modelling suggests that, in a worst case scenario, glint may be

visible from March-September between 17:45-19:20 GMT. The computer model

indicates that the glint will be primarily of a low intensity as seen in Appendix 2. There

is a potential for a mid-intensity glint to occur from 17:50-18:30 GMT in March-April

and Oct–Nov. However, there is a mature treelines along this footpaths which will

further limit the potential for glint to occur.

The footpath to the west of the development located at a distance of at 400m to the

site boundary of which a length of 1km of footpath which lies within the ZTV and

ground glint zone. Computer modelling suggests that, in a worst case scenario, glint

may be visible from March-September between 05:20-06:30 GMT. However, there is

a mature treeline along this footpath which will further limit the potential for glint to

occur.

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Figure 4.3: Showing Roads Located within ZTV and Ground Glint Zone (in Green)

4.5 Effect on Public Roads

There are several roads which run in close proximity to the proposed development, of which

four has distances that lie within both the ground based glint zone and ZTV, suggesting there

is a theoretical potential for glint to occur.

The most notable road is the unnamed road which runs in a south west to northeast

orientation, from Llandegwning to Mynytho. The Road is situated 600m east of the proposed

development, it has a total distance of approximately 1.3km that lies within the ZTV and

ground glint zone

Computer modelling suggests glint may occur from March to September between 17:50-

19:00 GMT. The computer model indicates that the glint will be primarily of a low intensity as

seen in Appendix 2. However, there is a potential for a mid-intensity glint to occur from 18:00-

18:30 GMT in March-April and Sept –Oct. Further inspection of aerial imagery as seen in

Figure 4.4 below indicates that there is sufficient natural screening along this road, which will

further reduce the potential for motorists to receive glint.

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Figure 4.4: Image Travelling on the Unnamed Road which Runs West-East, from

Llandegwning to Mynytho (© 2014 Google)

The next most notable road is the unnamed road that runs in a South to North orientation

from Llandegwning to Botwnnog. This road is the closest most notable road to the proposed

development located at a distance of 150m and has a section of approximately 750m of which

is located within the ZTV and ground based glint zone suggesting there is theoretical potential

for motorists to receive glint.

Computer modelling for this road suggests that a low intensity glint may theoretically be

visible from March-September at between 04:50-06:50 GMT. However, it is worth mentioning

that this road has a substantial amount of natural shading in the form of mature treelines and

hedging. The following image (Figure 4.4) has been included to give an indication of such

screening.

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Figure 4.5: Image Travelling South-North from Llandegwning to Botwnnog with the

proposed array located to the East. (© 2014 Google)

The road that runs in an east to west orientation also lies within the ground glint zone and

ZTV suggesting there is scope for motorists to receive glint along this section of road. The

extent to which the span of road lies within both the ZTV and ground based glint zone is

around 1.3km. The road is situated 800m to the west-northwest of the proposed site

boundary.

Computer modelling suggests that low intensity glint events can occur from April to

September between 05:30 and 06:30 GMT. The modelling suggests glint will be of a low

intensity and further inspection of aerial photography, as seen in Figure 4.6 below, the

screening to the roads in the form of hedgerows and treelines should further limit any

potential for glint to be experienced by road users.

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Figure 4.6: Image Travelling East-West on the unnamed road running from Bryncroes to

Nanhoron. (© 2014 Google)

The final road to mention is the unnamed road that runs in a North-South orientation from

Bryncroes to Rhiw this road has a 2.5km section of road that lies within both the ZTV and

ground based glint zone is around 1.3km. The road is situated at 3km to the west of the

proposed site boundary.

Figure 4.6 below has been included to give an indication of a motorists view travelling along

the unnamed road, glint would normally be expected due to the road height above the

proposed array. However, this will be vastly reduce with screening between the 3km distance.

Computer modelling suggests that low intensity glint events can occur from March to

September between 05:50 and 06:40 GMT. The modelling suggests glint will be of a low

intensity and further inspection of aerial photography as seen in Figure 4.6 below, the

screening to the roads borders in the form of hedgerows and treelines should further limit

any potential for glint to occur.

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Figure 4.6: Image Travelling South-North on the unnamed road running from Rhiw to

Bryncroes. (© 2014 Google)

4.6 Effect on Railways

There are no railway tracks within 5km of the proposed development.

A consultation with Network Rail would normally be undertaken. However, as mentioned

above the proposed development is located at a distance of 11km to the nearest railway track

therefore glint is not expected.

4.7 Effect on Airfields & Aircraft

There are concerns that glint could have a negative effect on both airfield and aircraft

operations whilst on the ground and on aircraft flying over or near to the site. Table 4.2 below

gives the details of aerodromes within 30km of the site and shows that there is one licensed

civilian aerodrome within the vicinity (30km) of the site.

Table 4.2: Aerodromes within 15km of the Site

Name Distance Use

EGOD Llanbedr 30Km E Licenced civilian aerodrome

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Figure 4.7, below shows the known aerodromes and airfields surrounding the site. Also shown

on this map are the military low fly zones as published by the MoD. As can be seen the site

lies within the blue zone which indicates that low flying exercises are of a low priority in the

area.

Figure 4.7: Airfields around the Site and Military Low Fly Zones

4.8 Cumulative Effects

There are no known solar farms built, consented or in planning in the immediate area around

the proposed development. For this reason there are not expected to be any cumulative glint

effects.

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4.9 Mitigation

Mitigation measures have already been implemented into the design of the scheme by

reducing the size of the site and locating the solar panels in areas that would lead to the

lowest visual impacts.

Hedgerows located on the boundary of the development areas within the site should be

allowed to grow to 2.5/3m in height, and any gaps planted up. This would primarily reduce

the visual impact associated with visual receptors within close proximity to the site, but would

also reduce the prominence of the development in distant views

In addition a new hedgerow should be planted on the eastern boundary of the site, as this is

the only boundary not located adjacent to an existing hedgerow, tree belt or woodland block.

The proposals would take around 5 to 8 years to establish and grow sufficiently to screen

views

The screening that has been discussed in this chapter will further reduce the potential for glint

to occur, this mitigation measure will also ensure that potential glint impacts will reduce as

the planting grows.

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5 SUMMARY

This report has set out to demonstrate the possible effects that reflected sunlight from the

proposed solar farm would have on receptors in the vicinity. These include residential

properties, road, rail and air traffic and users of public rights of way.

There is currently some potential for glint effects to be visible from individual properties and

nearby roads around the site. It is possible that the screening present around the site itself

and in the local area, in the form of trees and hedgerows, will prevent most of these effects

although this cannot be confirmed definitively at this stage. Consequently it is assumed that

at certain times of the day and year, there is some potential for glint reflections to be

experienced by both residents and motorists. It must be borne in mind that motorists

frequently encounter reflections whilst driving and routinely travel directly towards the sun

when it happens to be low in the sky. Effects are modelled as being of a low intensity and,

given the relative infrequency of predicted events, even if they are visible, they are not

expected to be a cause of substantial nuisance to residents.

At the time of writing no consultation was deemed necessary with Network Rail due to the

distance between the proposed development and the nearest railway track.

Hedgerows located on the boundary of the development areas within the site should be

allowed to grow to 2.5/3m in height, and any gaps planted up. This would primarily reduce

the visual impact associated with visual receptors within close proximity to the site, but would

also reduce the prominence of the development in distant views

Notwithstanding this, the glint events modelled should be placed in context:

The panels will be made up of specialist glass, which has a much lower reflectivity than

conventional glass. The strength of reflection is much lower than from other features

commonly seen such as glasshouses, glass fronted buildings and calm reservoirs.

Aircraft can currently operate at low level near to these features without any

significant effects caused by glint.

Due to the fixed orientation of the panels reflections can only be directed to one area

of the sky at any one time. This point slowly moves across the sky as the sun moves

during the course of a day. The maximum extent of any glint is only the size of the

proposed solar farm and as such an aircraft moving at high speed will cross this point

very quickly.

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The sun offers a much stronger source of intense brightness that is longer in duration

than any reflection from solar panels. The potential for glint will not exist where cloud,

rain or other weather event obscures the sun from the panels as glint can only be

caused by direct sunlight incident on the panels.

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6 REFERENCES

Aviation Pros, 2013. Düsseldorf International Airport Goes Solar. [Online]

Available at: http://www.aviationpros.com/news/10599152/dsseldorf-international-airport-

goes-solar [Accessed 3 March 2014].

Building Research Establishment, 1991. Site Layout Planning for Daylight and Sunlight, a Guide

to Good Practice, s.l.: s.n.

Business Green, 2013. Gatwick solar system hailed a runway success. [Online]

Available at: http://www.businessgreen.com/bg/news/2156392/gatwick-solar-cleared

[Accessed 4 March 2014].

Civil Aviation Authority, 2010. Interim Solar Photovoltaic Guidance, s.l.: s.n.

Federal Aviation Authority, 2010. Technical Guidance for Evaluating, Washington DC: s.n.

Sun Earth Tools, n.d. [Online] Available at: http://www.sunearthtools.com/

[Accessed 06 2014].

Sandina National Laboratories, 2014. GHHAT technical text. [online] Available at

https://share.sandia.gov/phlux/static/references/glint-glare/SGHAT_Users_Manual_v2-

F.pdf (accessed 08/01/2014)

Sunpower Corporation, 2011. Solar Module Glare and Reflectance Technical Memo, s.l.: s.n.

2015.[ONLINE] Available at:http://www.ead.eurocontrol.int/eadbasic/pamslight-

EF167E56E9C329BB73138FA50E323A96/7FE5QZZF3FXUS/EN/AIP/AD/EG_AD_2_EGNH_en_

2015-05-28.pdf. [Accessed 16 June 2015].

http://www.ead.eurocontrol.int/eadbasic/pamslight-EF167E56E9C329BB73138FA50E323A96/7FE5QZZF3FXUS/EN/AIP/AD/EG_AD_2_EGNH_en_2015-05-28.pdf



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