Wind Power and Radio

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Nov 24, 2013 (3 years and 6 months ago)

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Wind Power and Radio
Astronomy

A.
Jessner
,
MPIfR

Effelsberg

April 2010

1.
Introduction

2.
Possible Impact Mechanisms

3.
Compatibility Estimates

4.
A Case Study



Because of the grave environmental and energy problems

facing humanity on a global scale, all efforts to utilize sustainable
energy sources ought to be supported.




Wind power for electricity generation is one of the few
sustainable ways of power generation with minimal CO
2

emissions.




Farms of wind turbines are planned to be installed next to radio
astronomy facilities. Planning procedures have started in Sweden,
Belgium, Italy (Sardinia) and Germany




Compatibility of wind parks has been studied w.r.t.


TV reception, fixed links and radar




But not yet for radio astronomy

IMPACT MECHANISMS


The interference to radio astronomy can be produced by:


1.
Primary emissions:
generator and associated circuitry used by


variable speed wind turbines or HVDC systems generate harmonics


These can be radiated and also received by RA station as interference.



Electrical power 3 MW (
65
dBW
) RA sensitivity 10
-
20

W
(
-
200
dBW
)



2.
Secondary emissions:

multipath propagation effects (reflections, diffractions, etc)


produced by tower and rotating blades of the wind turbine. They act as a passive


repeaters for other transmitters.



Reflective areas of ca. 5000m
2



3.
Thermal Emission:
At distance of 3km a 100m disk subtends an angle of
1.9
°




HPBW of a 100m dish at 600 MHz
= 0.34
°

=> ‘Artificial Moon’


Generic Case: Impact assessment procedure


1.
Calculate the effective path loss
L
b
(p,f)

from the telescope to the site for
each frequency band using the methods (8a) of ITU
-
R P.452
-
12.


For cases where there is no direct line of sight because of elevated terrain
between the observatory and the proposed structure, a path profile analysis
according to Appendix 2 to Annex 1 of ITU
-
R P.452
-
12 has to be
undertaken to include the sub
-
path diffraction losses.

2. If the antenna cannot point at the structure, then calculate the maximum


side
-
lobe gain
G
max
(f)
=

32
-

25log(f
min
) If the antenna can point at the


structure, then use the full main beam gain of the antenna.


3.
ITU
-
R RA. 769 gives a table of emission limits of continuum input power
D
P
H

(table 1, column 7) for each radio astronomical frequency. Any emission
from the site of the planned structure must be kept below the site limit of



D
P
site
=
D
P
H
+

L
b
(0.05,f)
-

G
max
(f)



4. Repeat for all relevant frequencies to
estimate site emission limits


The operator has to prove beyond all reasonable doubt that his
equipment will not exceed these emission limits through the sum


of all emissions from


a.
direct emission
D
m
d
(f)

from the plant and its control and power electronics
including transmissions from power lines. It is the burden of the operator to
prove that the equipment will stay within the operating constraints, by providing
proper emission measurements of his equipment in the required bands.


b.
radiation

D
P
scat
(f)

from other sources scattered by the turbine and support
structures.


Assessment of scattered radiation :

Measurements of the power flux densities
S
site
(f,h)

(= pfd given in dB(W/m
2
) on
all bands and at heights
h

up to the top of the structure should to be made so that a
statistically meaningful survey of the ambient maximum signal levels
S
ambient
(f)

and the band occupancy at the proposed planning location is available.



For a proper assessment, these measurements should be performed at different
heights h and then an integration over the effective surface contributions with
varying heights should be made, yielding the effective scattered power of


D
P
scat
(f)= S
ambient
(f)+10∙log(
h
⡦⤩⬱シ汯木(
r
/m
2
)

Compatibility



means, that for all frequencies f, the sum of direct and


scattered emissions stays below the interference limit on


all considered frequencies in at least 98% of the time



a.
D
P
d
(f) +
D
m
scat
(f)

<
D
m
site
(f)



(in band limit)

b.
D
P
d
(f) +
D
m
scat
(f)

<
D
m
site
(f)+ G
out



(out of band limit)

c.
D
P
d
(f) +
D
m
scat
(f)

<
D
m
IM
+ L
b
(0.05,f)
-

G
max
(f)

(out of band IM limit)


If there is to be more than one Wind turbine, the cumulated effect of all structures
will have to be considered.


The administration should list the wind turbine site as a coordination location,
where the limits derived above may not be exceeded when new transmitters are
brought on
-
line elsewhere (i.e. The new 2.6 GHz mobile internet band).

Permitted Emissions from Equipment complying with


CISPR
-
22 (in Germany: EN 55022)


For industrial plant the radio disturbance characteristics and
emission limits are given by CISPR
-
22 for a measurement distance
of 3 m (10m for frequencies below 230 MHz):



40 dB
m
V/m for f < 230 MHz

47 dB
m
V/m for 230 MHz < f < 1 GHz

56 dB
m
V/m for 1 GHz < f < 3 GHz

60
dB
m
V/m for f > 3 GHz


In the US, the standards according to
FCC Rules
and

Regulations
,
Title 47, Part 15

B apply.


10
100
1
10
3
1
10
4
1
10
5
250
200
150
100
50
0
Permissible Radio Emission
MHz
Power dB(W)
Diamonds indicate the permitted signal level
receivable

on the telescope site
DP
H
(f)

according to
ITU
-
R RA 769
-
2

and the blue line shows the
emission

E
EN
(f)

permitted by the
CISPR
-
22

standard. The difference is the minimum path loss
L(f)

required to shield the telescope from the
permitted

equipment emissions.


10
100
1
10
3
1
10
4
1
10
5
110
120
130
140
150
Required Pat h Loss for Prot ect ion
MHz
dB
Pathloss required for Compatibility of Industrial Plant with Radio Astronomy

100
1
10
3
1
10
4
0
200
400
Separat ion Dist ances
frequency (MHz)
min. separation (km)
The graph below shows the required separation distance for various frequencies
(red) and the line of sight horizon for a 50 m telescope and a 150 high structure
with electrical equipment that is in compliance with CISPR
-
22.


Horizon for free space propagation in flat terrain

Case Study:



Proposed Placement of Windpower Generators close to the
Radio Observatory in Effelsberg (Germany).



Twenty
-
one sites have been marked for development as
locations of 150m high windturbines in a district about
24 km
south
-
east of Effelsberg.


Map of the district where
wind parks are planned
(TOP50) Proposed sites are
not marked, as they would be
easily lost in the detail.


The lake shown is 2.0 km
long and 1.2 km wide.


The path loss between the telescope at a height of 50m and the centre of a wind
turbine at the same height has been calculated for four different frequency bands
(0.61 GHz, 1.41 GHz, 5 GHz, 10 GHz).


Four digital maps, one for each frequency, showing the expected path loss in a
60km by 60 km area centred on Effelsberg were provided by ANFR.


longtude (deg)
latitude (deg)
path loss


+ Gebiete 27.62 18.67
* WKA Kempenich
* WKA Weibern
+ 19.10
+ 12.53
+ 21.57
+ Gebiete 0.16 1.29
+ 8.57
+ 5.42
+ 6.51
+ 6.29
+ 0.68
+ 10.44
+ 0.28
+ 3.55
+ 1.41
+ 85.74 Sued
+ 17.78
+ 1.16
+ 5.73
7.05
7.1
7.15
7.2
7.25
7.3
-50.5
-50.48
-50.46
-50.44
-50.42
-50.4
-50.38
110
120
130
140
150
160
170
180
190
200
Characteristics of Proposed Sites for Wind Turbines 24 km SW of Effelsberg

Location

Path Loss (dB)





Emission limit (
dBm
/MHz)



610 MHz

1400 MHz

5000 MHz

10 GHz


610 MHz

1400 MHz

5000 MHz

10 GHz













0.16

159

170

184

191


-
21

-
49

-
30

-
19


0.28

173

187

208

219


-
7

-
32

-
6

9


0.68

173

183

196

203


-
7

-
37

-
18

-
7


10.44

170

180

194

201


-
9

-
39

-
20

-
9


01.16

156

166

180

187


-
23

-
53

-
34

-
23


12.53

156

166

181

188


-
23

-
53

-
33

-
22


01.41

169

179

193

200


-
10

-
40

-
21

-
10


17.78

161

173

190

198


-
19

-
47

-
24

-
12


19.10

152

165

180

187


-
28

-
54

-
34

-
23


21.57

141

152

168

177


-
39

-
68

-
46

-
33


03.55

172

182

196

202


-
8

-
37

-
18

-
8


05.42

141

152

169

178


-
39

-
67

-
45

-
32


05.73

156

166

180

187


-
23

-
53

-
34

-
23


06.29

166

179

198

208


-
14

-
40

-
16

-
2


06.51

159

171

185

192


-
21

-
49

-
29

-
18


08.57

117

120

129

135



-
63

-
99

-
85

-
75



85.74 Nord

169

181

196

203


-
11

-
38

-
18

-
7



85.74 Süd

163

174

188

194


-
16

-
45

-
26

-
16



WKA1

160

172

189

197


-
20

-
47

-
25

-
13



WKA2

157

168

187

195


-
23

-
51

-
27

-
15



27.62 + 18.67

144

157

175

183


-
35

-
63

-
39

-
27


Minimum Path Loss in dB for Compatibility between CISPR
-
22 and ITU
-
R 769
-
2


610 MHz


1400 MHz

5000 MHz

10 GHz



134


135


141


136


=> Site specific ambient radiation levels are still unknown, the planning procedure continues

Summary
:



1.
The
use

of

wind power
is

necessary

to

minimize

CO
2

emissions

and

to



provide

energy

sources

that

are

indepented

of

fossil
fuels
.


2.
The
compatibility

of

wind power plant
and

radio

astronomy

stations

has

not


been

studied

before
, but
there

is

the

potential
of

very

strong
interference

over

a
great

distance
.


3.
Primary
and

secondary

emissions

from

wind power
generators

vary

from

site

to

site

and

depend

on
construction

details
.
Their

levels

need

to

be

established

prior

to

any

compatibility

assesment
.


4.
Propagation
of

radio

waves

between

wind power
site

and

radio

telescope

is

strongly

frequency

and

location

dependend
.


5.
Direct

line

of

sight

placement

of

wind
parks

near

radio

telescopes

should

be

avoided

.


6.
Good

modelling

procedures

are

available

to

establish

protection

criteria


7.
Compatibility

and

co
-
existence

of

wind power
and

RAS
can

be

achieved

in
the

small

areas

around

a
telescope

that

do
require

coodination
.