Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Electric power subsystems in satellites
H.J. de Graaf
Dutch Space, Leiden
Symposium Advanced Battery Technology in Automotive and Aerospace
Helmond, 19-5-2010
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Contents
• Types of orbits• Power budget• Architecture and components• Batteries• Requirements for S/C equipment
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Low Earth Orbit (LEO)
• Altitude: 160 to 2000 km• Orbit duration 88-127 minutes
typical• Eclipse duration: 20 to 35 minutes• About 37.000 Battery
charge/discharge cycles over mission lifetime of 7 years
• Battery maximum Depth of Discharge: 20%
• Often used for earth observation missions
LEO
GEO
Not to scale
N
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Geostationary Earth Orbit (GEO)
• Fixed location above point on equator
• Altitude: 35,786 km• Orbit duration 24 hours• Eclipse duration: 0 to 72 minutes• About 1,350 Battery
charge/discharge cycles over mission lifetime of 15 years
• Battery maximum Depth of Discharge: 80%
• Used for telecommunication and weather satellites
LEO
GEO
Not to scale
N
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Medium Earth Orbit (MEO)
• Altitude: 2000 to 35,786 km• Used among others for navigation
satellites:– GPS: 20,350 km alt.– GLONASS: 19,100 km alt.– Galileo: 23,222 km alt.
Galileo
GPS
GLONASS
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Power Budget
• Solar array sizing is determined by:– Orbit average power need– Sun/eclipse ratio
– Losses in the system
• Battery sizing is determined by:– Eclipse power need
– Eclipse duration– Capacity fading (due to
mission lifetime and charge/disch. cycles
– Losses in the system
LEOGEO
Not to scale
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Example of simulated Power S/S behaviour (LEO)
• Body-mounted SA generates sine-shaped SA panel currents
• Battery charging strategy is CCCV (constant current, constant voltage), however the current varies to maximiseefficiency
0%
20%
40%
60%
80%
100%
0 90 180 270 360 450 540 630 720
Orbital phase [degrees]
Bat
tery
Ch
arg
e [%
]
0
1
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6
SA
ou
tpu
t / R
egu
late
d c
urr
ent [
A]
Bat
t. C
ell v
olta
ge
[V]
Batt charge
SA current
Regulated current
Batt cell volt
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Basic equipment and functions
• Solar Array– primary power generation
• BAPTA (Bearing and Power transfer assembly)– SA sun pointing by stepper motor, SA power transfer often via sliprings
• Battery– energy storage and peak power generation
• Power Control Unit– Solar Array power conditioning– Battery charge/discharge regulation– Communication to OBC (On-board Computer)
• Power distribution– Circuit protection– On/Off switching
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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DriveElectr.
Architecture
SAPCU
BAPTA
BAT
SA BAPTA PDU
SA pointing and power transfer
Circuit protection and power distribution
SA power conditioning and BAT management
OBCDriveElectr.
S/C Databus(Main+Red.)
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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PC(D)U
• Autonomous start-up in case the S/C is un-powered during launch
• Redundant design• Single point free design
BCRS3R
PCDU
Data I/F module
2 x Solar ArrayWing
BDR
50 Vdcregulated
PowerDistribution
+Cap. Banks
Section
50 Vdc
50 Vdc
28 Vdc
28 Vdc
CAN Bus
ExternalCharge (EGSE)
ExternalPower
(EGSE)
BAT TLM
2 x SADM
TSA
SA/SADM TLM
SADM drive signals
Li-ion Battery
EssentialHK
Essentialcommands
S/CSeparation
SwitchSignals
28 Vdcunreg.
Small PCU (70 W)
Large PCU (4000 W)
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Solar Array
• SA Power efficiency determined by– Solar cell type
• Silicon• Gallium-Arsenide
– 1-junction– 2-junction– 3-junction (state-of-the-art), up to 30% @
20 °C– Power conditioning method
• MPPT (Max. Power Point Tracking)• DET (Direct Energy Transfer)
– Temperature• GEO 70 °C• LEO 90 °C• LEO and body-mounted panels >100 °C
– Cosmic radiation degradation– Cell lay-up efficiency– Typical power/area is 200 W/m2 at EOL
for GEO– BOL design case dimensions required
wire gauge, slipring capability, etc.
0
10
20
30
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90
100
0 10 20 30 40 50 60 70
Voltage [V]
Cur
rent
[A]
0
1000
2000
3000
4000
5000
6000
Pow
er [W
]
Begin of Life (BOL)
End of Life (EOL)
0
10
20
30
40
50
60
70
80
90
0 10 20 30 40 50 60 70
Voltage [V]
Cur
rent
[A]
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Pow
er [W
]
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Solar Array types
• Rotating wings– S/C earth-pointing
• Fixed wings– S/C sun-pointing
• Body-mounted– S/C can be tumbling
Sloshsat
SOHO
Optus
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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BAPTA (or SADM)
• Stepper motor to keep SA sun pointing (S/C body is normally earth pointing)
• Slipring assembly transfers the SA generated power to the PC(D)U
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Space batteries, Ni technologies
• Nickel-Hydrogen (Ni-H2)– Heritage on GEO satellites– No longer used for new
designs
• Nickel-Cadmium (Ni-Cd)– Heritage on LEO satellites– No longer used for new
designs
SLOSHSAT Battery
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Space batteries, Li technologies
• Lithium-ion– Higher energy density than the
Nickel-based batteries– Heritage on LEO and GEO
satellites, widely used for new designs
• Lithium Polymer– Even higher energy density than
Li-ion– Not yet qualified for use on
satellite power subsystems
0
20
40
60
80
100
120
140
Wh/kg Wh/ltr
NiCdNiH2Li-ion
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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European S/C Battery Manufacturers
• SAFT– Dedicated development for space use– Cells placed in parallel/series configuration– Large single cell: 1.1 kg– Battery cell balancing performed– Relatively low shelf-life capacity fading
• ABSL– Battery cells from commercial origin (Sony 18650HC)– Cells placed in series/parallel configuration– Small single cell: 42 g– No Battery cell balancing performed– Relatively high shelf-life capacity fading
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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SAFT
• At the moment mainly used for GEO missions (15 years)
• Parameters for 3P9S battery:
STENTOR Battery
42.5 kgBattery mass
4188 WhTotal energy capacity at EOL
9.3%Capacity fading
4617 WhTotal energy capacity at BOL
9Number of cells in series
3Number of cells in parallel
171 WhEnergy capacity per cell at BOL (nominal)
SAFT VES180Cell type
ValueItem
4P8S configuration
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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ABSL• Mainly used for LEO and
interplanetary missions (< 7 years)
• Battery parameters (for GEO):
52 kgBattery mass
4141 WhTotal energy capacity at EOL
29%Capacity fading
5832 WhTotal energy capacity at BOL
10Number of cells in series
108Number of cells in parallel
5.4 WhEnergy capacity per cell at BOL (nominal)
Sony 18650Cell type
ValueItem
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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General requirements for S/C equipment
Requirement comment Verification method
Vibration - dictated by launch environment Analysis and testThermal - No heat exchange by convection, only by
conduction and radiation - Sun/eclipse cycles can cause large temperature range to cover, especially for exposed equipment like Solar Arrays
Analysis and test
Outgassing Review of designCosmic radiation (solar particles) - Solar cells
- Materials - Electronic components
Analysis
Magnetic moment - Residual magnetic moment will have effect on S/C Attitude Control
Analysis
Copyright © 2010 Dutch Space B.V., The NetherlandsAll rights reserved. Disclosure to third parties of this document or any part thereof, or the use of any information contained therein, for purposes other than provided for by this document is not permitted, except with the prior and express written permission of Dutch Space B.V.
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Questions???