Transcript Wind Power and Radio Astronomy

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 CO2
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. 5000m2
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 Lb(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 Gmax(f) = 32 - 25log(fmin) 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
DPH (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
DPsite= DPH+ Lb(0.05,f) - Gmax(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 DPd(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 DPscat(f) from other sources scattered by the turbine and support
structures.
Assessment of scattered radiation :
Measurements of the power flux densities Ssite(f,h) (= pfd given in dB(W/m2) 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 Sambient(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
DPscat(f)= Sambient(f)+10·log(h(f))+10·log(Ar/m2)
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. DPd(f) + DPscat(f)
b. DPd(f) + DPscat(f)
c. DPd(f) + DPscat(f)
< DPsite(f)
(in band limit)
< DPsite(f)+ Gout
(out of band limit)
< DPIM+ Lb(0.05,f) - Gmax(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
47
56
60
dBmV/m
dBmV/m
dBmV/m
dBmV/m
for
f < 230 MHz
for 230 MHz < f < 1 GHz
for
1 GHz < f < 3 GHz
for
f > 3 GHz
In the US, the standards according to FCC Rules and Regulations,
Title 47, Part 15 B apply.
Permissible Radio Emission
0
Power dB(W )
50
1 00
1 50
2 00
2 50
10
1 00
3
1 10
MHz
4
1 10
5
1 10
Diamonds indicate the permitted signal level receivable on the telescope site DPH(f)
according to ITU-R RA 769-2 and the blue line shows the emission EEN(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.
Pathloss required for Compatibility of Industrial Plant with Radio Astronomy
Required Path Loss for Protection
1 50
dB
1 40
1 30
1 20
1 10
10
1 00
3
1 10
MHz
4
1 10
5
1 10
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.
Separation Distances
min. separation (km)
4 00
2 00
0
1 00
3
1 10
freq uen cy (MHz)
Horizon for free space propagation in flat terrain
4
1 10
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.
path loss
+ 19.10
200
+ Gebiete 27.62 18.67
-50.5
190
+ 12.53
+ Gebiete 0.16 1.29
180
+ 21.57
-50.48
latitude (deg)
+ 5.42
+ 8.57
+ 6.51
-50.46
170
+ 6.29
-50.44
+ 0.68
+ 10.44
+ 0.28
+ 3.55
+ 17.78
+ 1.16
160
150
+ 1.41
+ 85.74 Sued
140
* WKA Kempenich
-50.42
* WKA W eibern
+ 5.73
130
-50.4
120
110
-50.38
7.05
7.1
7.15
longtude (deg)
7.2
7.25
7.3
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
Characteristics of Proposed Sites for Wind Turbines 24 km SW of Effelsberg
Location
0.16
0.28
0.68
10.44
01.16
12.53
01.41
17.78
19.10
21.57
03.55
05.42
05.73
06.29
06.51
08.57
85.74 Nord
85.74 Süd
WKA1
WKA2
27.62 + 18.67
Path Loss
610 MHz
(dB)
1400 MHz
5000 MHz
10 GHz
610 MHz
Emission limit (dBm/MHz)
1400 MHz
5000 MHz
10 GHz
159
173
173
170
156
156
169
161
152
141
172
141
156
166
159
117
169
163
160
157
144
170
187
183
180
166
166
179
173
165
152
182
152
166
179
171
120
181
174
172
168
157
184
208
196
194
180
181
193
190
180
168
196
169
180
198
185
129
196
188
189
187
175
191
219
203
201
187
188
200
198
187
177
202
178
187
208
192
135
203
194
197
195
183
-21
-7
-7
-9
-23
-23
-10
-19
-28
-39
-8
-39
-23
-14
-21
-63
-11
-16
-20
-23
-35
-49
-32
-37
-39
-53
-53
-40
-47
-54
-68
-37
-67
-53
-40
-49
-99
-38
-45
-47
-51
-63
-19
9
-7
-9
-23
-22
-10
-12
-23
-33
-8
-32
-23
-2
-18
-75
-7
-16
-13
-15
-27
-30
-6
-18
-20
-34
-33
-21
-24
-34
-46
-18
-45
-34
-16
-29
-85
-18
-26
-25
-27
-39
=> Site specific ambient radiation levels are still unknown, the planning procedure continues
Summary:
1. The use of wind power is necessary to minimize CO2 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.