A Sunlight-to-Microwave Power

Transmission Module Prototype for

Space Solar

Paul Jaffe, PhD

U.S. Naval Research Laboratory

Paul.Jaffe@nrl.navy.mil

Overview

Space Solar and the

“Sandwich” Approach

Thermal Considerations & the Tile

and Step Sandwich Module Concepts

Progression Through Layer Designs

& Implementations:

– Solar Array

– Electronics

– Antenna

Testing Methodology

Results2

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Motivation

Climate change demands new energy sources

Alternatives to fossil fuels often suffer from:– Intermittency

– Lack of scalability

– Locale dependence

– Safety risks

Solar energy has a long history:– Pro: The sun is an effectively unlimited energy supply

– Con: Ground solar collection suffers from night and

atmospheric losses

Recent studies of Space Solar suggest research

that may clarify its technology challenges &

economic feasibility– Technological advances may increase its prospects

– Niche applications may tolerate higher energy cost,

such as remote military bases3

4

What is Space Solar?

Collection of solar energy in space and its wireless transmission for use on earth

– Overcomes atmospheric and diurnal limitations associated with terrestrial solar power

– Could offer energy security, environmental, and technological advantages to initial developers

– Has been criticized as economically infeasible, but there is not an empirical basis from which to create a realistic detailed analysis

5

Functions a Solar Power Satellite Must Perform

Energy Collection:

– Photovoltaics (PV)

– Solar thermal (Heat Engine)

– Sun-pumped lasers

Power Transmission:

– Microwave

– Laser

– Reflection

NASA Reference Design, circa 1981

Aerospace Corp. Laser Concept, circa 2002

For this discussion, focus will be

on the most commonly proposed

combination, PV/Microwave

" , .. v ,,. ...... ........ ,. ......... :.

6

System Blocks and Estimated

Currently Achievable Efficiencies

Segment Efficiency Notes

Photovoltaics 30%Efficiencies >40% in lab

under concentration

DC-to-RF

Conversion85%

Varies with conversion

method & implementation

Antenna 90%Includes conduction and

scan losses

Atmospheric

Transmission98%

Weather & frequency

dependent

RF Collection

Area90%

Function of rectenna array

size & transmit taper

Rectenna

Elements91%

Demonstrated at 2.45

GHz

TOTAL 17%

Energy is available

essentially 24 hours a

day, all year round

Satellite

Ground Station

Modular Architectures

Each PV/Microwave

architecture has:– Solar panel area

• Affects power collected

– Antenna transmission area• With frequency, affects

power beam directivity

Some architectures

match these two areas

and increase power

collected using

concentrating reflectors– Reduces wiring mass and

avoids slip rings

Modular Symmetrical Concentrator, circa 2007 (NSSO)

Thousands of adjacent

sandwich modules form

this surface

SPS-ALPHA, circa 2012 (Artemis Innovations)

Thousands of

adjacent

sandwich

modules form

this surface

8

Solar Concentration

Concentration advantages:

– Improves solar cell efficiency

– Reduces the required panel

area

– Has the potential to reduce

launch mass for given power,

since reflectors tend to be

lighter than solar cells per unit

area

– Reflectors used for

concentration may also be

used to redirect energy to

simplify onboard power

distribution

Concentration disadvantages:– Compounds thermal challenges

because of the additional heat needing to be dissipated

– Requires additional structure to implement reflectors

– Requires higher pointing accuracy

Integrated Symmetrical Concentrator, circa 1998 (NASA)

Light

μWaves

Photovoltaics

DC to RF conversion

Antenna

The “Sandwich” Module

9

Prior Sandwich Module Efforts

Hiroshi Matsumoto, Kyoto University, with SPRITZ –

Solar Power Radio Integrated Transmitter, 2001

Owen Maynard Solid State Sandwich Report, 1980

2002 and 2001 Sandwich Reference Models, JAXA Contractor Report, 2003, URSI ICWG Report, 2007

Nobuyuki Kaya, Kobe University, and John Mankins with

sandwich prototype, photovoltaics removed, 2009 Photovoltaics removed to show

phase control electronics

Key Problems

Low PV & DC-RF efficiency

Implementing retrodirective

control of beam

Layer integration & thermal

dissipation

10

PROGRESS REPORT ON SOLID STATE SANDWICH CONCEPT

- DESIGNS, CONSIDERATIONS AND ISSUES -

Owen E. Maynard

Raytheon Company, Equipment Divis ion

P resenfeallt

Sol id State Configurations Session of the SPS Microwave Systems Wo 15-18 January 1980

Lyndon 8. Johnson Space Center, Houston, Texas

Antenn,1

/1 ~~

11

Objectives of the Research

(2) Perform the First Test of a

Sandwich Module for Space Solar

Power Under Space-like Conditions

(1) Design, Fabricate, and Test the

Highest Specific Power, Highest

Efficiency Sandwich Module to Date

(3) Characterize and Compare the

Performance of Two Different Types

of Sandwich Modules

12

Figures of Merit (FOMs) for Sandwich Modules

Mass per unit area [kg/m2]

Specific power [W/kg]

Combined conversion efficiency [%]

Sun concentration ratio acceptance [# suns]

Survival temperature range [°C]

Continuous operation duration [hours]

Other considerations: – Adaptability for use with a retrodirective control scheme, Susceptibility to space radiation

environmental effects, Susceptibility to solar wind and space weather effects, Solar UV

degradation tolerance, Space environment charging behavior, Susceptibility to parts aging

effects, Avoidance of multipactor effects, Launch acoustic and vibration environment

tolerance, Electromagnetic compatibility and interference susceptibility, Manufacturability,

Ease of integration with other modules in space, Ability to transfer heat from other modules,

Ability to transfer electrical power from other modules, Outgassing qualities, Structural

rigidity, Reliability, Durability, Serviceability

Of Primary

Interest

Light (about 7% of incident

light is reflected)

μWaves

Photovoltaics ~30% efficient

DC to RF ~80% efficient

Antenna ~95% efficient

Summary of the Thermal Challenge

Using Idealized Efficiency Figures

13

P is the heat power radiated

ε is the emissivity of the material

σ is the Stefan-Boltzmann constant

A is the radiating area

T is the temperature

Stefan-Boltzmann Law:

P = εσAT4

Heat

TOTAL MODULE

EFFICIENCY: ~23%

For every 100W of incident sunlight,

about 72W must be radiated as heat power

14

Temperature Considerations

Solar cell and solid state power amplifier efficiencies decrease with rising temperature

Options to maintain acceptable operating temperatures:

P = εσAT4

– Increase total module efficiency to reduce heat power

• PV is limiting factor, efficiency increase beyond scope

– Reduce sun concentration

• Reduces potential system mass savings

– Use high emissivity materials (≈1)

• Limited by black body radiator

– Increase device operating temperature

• Beyond project scope

– Increase radiator area

• Means a departure from the flat module approach

(constant)

15

Radiator Area Required to Maintain Temperature Equilibrium for a

Flat, 28 cm x 28 cm Square Module at 23% Efficiency

1.0

0.9

0.8

Ki"' 0.7 E .._... co 0.6 (1) Ii,.,.

<( 0.5 Ii,.,.

0 +-' 0.4 co ,:, co 0.3 0:::

0.2

0.1

0.0 0

-+-Black body ( emissivity 1) @ 65°C ~ Anodized Al (emissivity 0.9) @ 100°C _._Graphite (emissivity 0.96) @ 100°C ~ Black body ( emissivity 1) @ 100°C ~ Black bod ( emissivit 1 @ 200°C

0.078 m2 (one side of module)

1 2 3 4 5 6 7 8 9

Number of Suns of Concentration

10

16

Temperature of Flat 28 cm x 28 cm Square Module with Both Sides

as Black Body Radiators for Various Module Efficiencies

350 - 10°1o

300 ..-.. -+---23%

~ 250 .,_... -+-50% (].) --5 200 ~ so% 0 ~ '+- 150 0 (].) ~

:J 100 +-' cu ~

(].) a. 50 E ~ 0

3 4 5 6 7 8 9 10 -50

Number of Suns of Concentration

17

Using a “Tile” Sandwich Module

The top and bottom sides of tile module are

available to radiate heat, sides connect to

adjacent identical modules which also need

to radiate heat.

Primary Mirror

Secondary Mirrors

/r\ ~

•· · Photovoltaics

and 1 , ~::~rn,ss,on

Antenna

Primary Mirror

a ia e ea

18

Using a “Step” Sandwich Module

Additional area on the step module for

radiating heat versus the tile module allows

cooler operating temperatures and/or

higher sun concentration levels

Primary Mirror

Secondary Mirrors

/r\ r

Primary Mirror

a iate ea

19

Simulation Shows Step Module Max Temp

Runs ~60° Cooler at 3 Suns vs. Tile Module

RF & power

electronics go

here to lower

heat exposure;

note electronics

temp is ~20°

cooler than tile

SOLAR

ARRAY

FACE

TRANSMIT

ANTENNA

FACE

SOLAR

ARRAY FACE

TRANSMIT

ANTENNA

FACE

Teri~eru-ture [ CJ Node > 110, 7

> 173, 2

110, 7

173, 2

101. 6

164, 3

92 , 4 9

155, 4

83, 37

146, 5

74

137, 7

65

128, 8

56

119, 9

46

11 1

37

102, 2

28

93, 3

19

84, 42

< 19, 55

<8 4, 42 TeM~erutur e [ CJ

Photovoltaics

DC to RF Electronics

Antenna

Tile Sandwich Module Layer Implementations

20

Solar Array: 28 Cells in Two Strings

Array has two 14 cell strings in parallel

– 28.3% efficient Spectrolab UTJ cells used,

mounted on FR4

1.59mm aluminum support substrate

– Step module utilizes a continuous piece of

pyrolytic graphite sheeting for heat spreading

Nusil RTV for bonding

21

AM0, 1 Sun, 70°C

Voc (V) 33.8

Isc (A) 0.919

Vmp (V) 29.1

Imp (A) 0.870

Pmp (W) 25.3

Power @ 28V (W) 24.4Output current scales nearly linearly with

sun concentration for a fixed temperature

Tile Module: 0.30m x 0.29m (12.6” x 11.3”)

Step Module: 0.30m x 0.29m (12.6” x 11.3”)

with 0.29m (11.5”) radiators

Tile Module Solar Array I-V Curve Testing

22

4000W Xenon light source with

different combinations of light

attenuating screens used for

measuring power output of each

panel string

1.0

0.9

0.8 - I-VCurve a

0.7 - I-VCurve b

~ 0.6

- Power{W) .... C ~ 0.5 - Power(W) :::s u

0.4 I-V curve a IV curve b

0.3 lsc = 0.9342 A lsc = 0.9409 A

Voe = 30.549 V Voe = 30.172 V

0.2 5 Pmax = 20.233 W Pmax = 19.761 W

Vmp = 26.786 V Vmp = 26.113 V

0.1 lmp = 0.7554A Imp = 0.7567 A

Fill Factor = 70.90 % Fill Factor = 69.61 %

0.0 Panel Temp = 128.5°C Panel Temp = 132.7°C _,._ ___________________________ ___..,__ ___ --1.. 0

0 5 10 15 20 25 30 35

Voltage{V)

Electronics: 2.45 GHz RF Amplifier Chain

RF chain matched for solar array is about 47% efficient

Tile module uses a single chain, Step module uses three

chains in parallel that are power combined

23

~ ~ o:jtl'.~ '" ~- CJC "" •m . •o. l'lMll!'"I, ;'; .. ,

Source BPF Atten Delay AMP Loss PA Loss Line Hittite CGH27015

@) [ZS] ~ 0 [> ~ [> ~ TOTAL

Vds [V] 5.0 5.0 29.0 Pde [W] 0.2 4.8 27.6 32.6 PAE [%] 3% 21.0 55.0 47.4%

Gain [dB] 0.0 -2.0 -6.0 -0.3 30.9 -0.1 12.1 -0.2 34.4 Pout [dBm] 7.5 5.5 -0.5 -0.8 30.1 30.0 42.1 41.9 41.9 Pout [W] 0.0 0.0 0.0 0.0 1.0 1.0 16.2 15.5 15.5

Electronics: Power Conversion

24

Power electronics was

designed to support both tile

and step modules

Power electronics measured

efficiency ~96% or better

Power Board Efficiency vs. # of Suns 96.8% ~---------------

96.6%

> 96.4% u -~ 96.2%

-~ 96.0% = w 95.8%

95.6%

95.4%

■ ■ -■ ■ -■ ■ - -1 2 3

# of Suns

■ S/N 2

■ S/N 3

, .. :~: . '(,

-- . - .. - -.. . - -- . - . t,j'

.. , • -~ .. a:

i 11111 , ......... ------· Ii{ - .. . . l 1111 !fi

Power and RF Electronics on Tile Module

Baseplate Prior to Thermal Feature Installation

25

Power

Electronics

Board

Voltage

Controlled

Oscillator

Driver

Stage RF

Amplifier

Final

Stage RF

Amplifier

26

Power and RF Electronics on Tile Module

Baseplate After Thermal Feature Installation

Blanketing

Covering

Power

Electronics

Board

Thermocouple

Wire Bundle

Black

Kapton

Tape

Antenna: Short Backfire Design

Flat reflector version used

Max published gain ~ 18.1 dBi

Quoted efficiency ~ 91-95%

Electronics module output

connected to dipole feed port

(linear-polarized)

To be Measured:

– VSWR

– Radiation Patterns & Gain

– Efficiency (Wheeler Cap method)

Gain Pattern

2.45 GHz

16.5 dBi peak

E-plane

H-plane

27

Dia: 292mm

Hgt: 61.2mm

in "O

C co

<.?

Surface current [d BA 1m)

-1 0 .o -15.0 ·20.0 - 2 5.0 - 3 0 .0

· 3 5.0 -40.0

• 4 5.0 - 50 .0

20

15

10

5

0

-5

-10

-15

'

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I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

-20 ~~~~~-~-~~-~-~-~-~~~--~~~~ -180 -150 -120 -90 -60 -30 0 30 60 90 120 150 180

Theta [deg]

28

Integrated Tile Module with Antenna Mockup

Tile Module Solar Array &

Power and RF Electronics Testing

29

DC to RF Electronics

Step Sandwich Module Layer Implementations

30

Photovoltaics

Antenna

31

Integrated Step Module with Antenna Mockup

Step Module Solar Array &

Power and RF Electronics Testing

32

33

Testing Apparatus – Tile Module Configuration

Vacuum Chamber

Test Workstation

Protective

Shroud

Sun

Simulator

and

Attenuating

Screens

34

Tile Module Illumination Testing –

Electronics Powered by Solar Array

Illumination Testing at Ambient

Pressure on Lab Bench

Illumination Testing Under Vacuum in

Thermal Vacuum Chamber

The gobo prevents excess light from entering and

unnecessarily heating the chamber itself, rather than

the test article

Tile Module RF Conversion Efficiency and Solar Array Temp

at Ambient Pressure Under Various Illumination Conditions

Screen A No Screen E D C B

100% 160 I I I I I

90°/o • Solar Array Temperature I I I I 140

I I I 80% • RF Conversion Efficiency

I I I 120 I I I 70% en

I I :::,

1 oo ·en 60% -I (1'

~ I u (.) 50% 80 C: en

(1' (1' ·- f (.) 40% ·- 60 C) :t: I I w I I I

(1'

30% I ~ .. _I f C

I ... 40 20%

I t I I I I I 20

10%

Screen A I

No Screen I

E I

D I

C I

B 0% I I I I I 0

~ ~ ~ ~ ~ ~ ~ ~ a.. a.. a.. a.. a.. a.. a.. a.. T""" LO 0) (") ~ T""" LO 0) ~ 0 N LO T""" ~ 0 N (") CX) N c.o Time ~ LO 0 ~ ~ LO T""" N LO T""" N T""" T""" N N N N (") (")

Tile module RF Conversion Efficiency, Solar Array Power,

and RF Output Power Under Various Illumination

Conditions at Ambient Pressure

I I I I I 90%

I Solar Array Power 1

70% -+-------<

• RF Conversion Efficiency 1 60% -+-----I ■ RF Output Power

1 ~ I g 50% +-------------- ---------- -----.1~~ --- --------1

a, • e -•t· a ·- -<.> 40% a 9

E W 30% +-------------~:--------~-

• 20% -+-------------------------------------- ------ --------------1 I I

10% +-------------- ---------- ---------.--- - ------1

S A IN s 118 O% _____ -----,,,~c~r~e~e~n.........,~-----.--~•-~o~~c~r~e~e~n........,~____,,,,,,,__--r"""'------"----=-____::_,--=-----' ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ m ~ ~ ~ ~ m 0 N ~ ~ ~ 0 N

f8 ~ ~ Time ~ t8 ~ ~ N N N N ~ ~

30

25

20 Cl)

= C'O

15 S:

10

5

0

Tile Module Data Show Vacuum Correlates

with Reduced Output Power

Ambient,

Pwr Sim

Ambient,

Light

Vacuum,

Light

Vacuum,

Light+

Vacuum,

Light++

Each cluster

of 3 points

represents

(in order) the

mean, min,

and max

Chamber

window

(not used for

ambient)

incurs ~5%

power loss

Light,

Light+, &

Light++

correspond

increased

light intensity

& degraded

field

uniformity

Data was collected over a 30 minute equilibrium period for each condition (σ<0.4°C for every temperature point)

50 I I I I

45 • • I I • I I • • • •

40 • 35 I I • I • Electronics Eff %

I I I A Array Power (W)

... ... ... ... 30 ... ■ Array Voltage (V}

■■■ I ■ ... ■ I I ♦ RF Power (W)

25 ■

' I ... ... 20 • '

■ ■

I I • I 15 •• I I I I 10

I I •• I • 5 I

I I I I 0

Tile Module Data Show Vacuum Correlates

with Higher Module Temperatures

Ambient,

Pwr Sim

Ambient,

Light

Vacuum,

Light

Vacuum,

Light+

Vacuum,

Light++Each cluster of 3

points represents the

mean, min, and max

Data was collected over a 30 minute equilibrium period for each condition (σ<0.4°C for every temperature point)

160

I I ••• I I ••• ••• 140 ♦ Array Right

I I ;;: I I ■ Array Bottom 120 e ' • Array Left ••• I I I ••• I ■ Array Top QJ

-c 100 .,, .,, . • Array Center "' ---

,._ ••• I

b0

I I ::+c Power Electronics +,I

C QJ 80

o vco u 1/)

I ooo I - RF Out Cable QJ

I I QJ

000 ,._ b0

+ RF plate center QJ 60 +++ C .,.,,

I I I I _. Final Stage Amp ~ ooo .._ Driver Stage Amp 40 +

XXX I I I I + RF plate corner ~~~

20 ••• I I I I

0

Tile & Step Module Figures of Merit

Mass per unit area (Lower is better)

– Antenna mockup rather than antenna used

– Tile Module: 21.9 kg/m2

• 1.91kg/(0.286m * 0.305m = 0.0872m2)

– Step Module: 36.5 kg/m2

• 3.33kg/(0.286m * 0.319m = 0.0913m2)

– Results fall within 4 kg/m2 to 40 kg/m2 predicted range found in the

literature

Specific power (Higher is better)

– Antenna and miscellaneous small parts masses are estimated

– Tile Module: 4.5 W/kg measured @ minimum 1.0 sun illumination in

vacuum

• Solar array temps 122-150°C, 9W RF output / 1.91kg module mass

– Step Module: 5.8 W/kg measured @ minimum 2.2 sun illumination in

vacuum

• Solar array temps > 103-130°C, 19W RF output / 3.33kg module mass

40

Tile Module Efficiency in Vacuum

Module conversion efficiency with minimum one sun

incident on module (>117 W over 0.0872 m2)

Solar Panel: power measured during integrated module under vacuum and solar illumination, solar array temps

in range 122-150°C as seen in plot for case “Light++”. Note cell voltage at peak power drops ~6.5mV/°C.

Power Electronics: power measured during electronics board standalone test under loading conditions similar

to integrated module test

RF Chain: power measured during integrated module test under vacuum and solar illumination, driver stage

amp @ 80°C, final stage amp @ 83°C

Antenna: *efficiency calculated from simulation

**Combined figure use simulated antenna efficiency value.

Element Goal Achieved Power Out (W)

Solar Panel 24% 19% 22

Power Electronics 95% 97% 22

RF Chain 50% 44% 9

Antenna 95% 95%* 9

COMBINED MODULE 11% 8%** 9

(Combined efficiency and power out at

ambient under illumination with no chamber

window were 11% and 14W)

41

Step Module Efficiency in Vacuum

Module conversion efficiency with minimum 2.2 suns

incident on module (>275 W over 0.0913 m2)

Solar Panel: power measured during integrated module under vacuum and solar illumination, solar array temps

in range >103-130°C. Note cell voltage at peak power drops ~6.5mV/°C.

Power Electronics: power measured during electronics board standalone test under loading conditions similar

to integrated module test

RF Chains: power measured during integrated module test under vacuum and solar illumination, driver stage

amps in range 105-107°C, final stage amps 95-101°C

Antenna: *efficiency calculated from simulation

**Combined figure use simulated antenna efficiency value.

Element Goal Achieved Power Out (W)

Solar Panel 20% 17% 46

Power Electronics 95% 97% 44

RF Chains 50% 44% 19

Antenna 95% 95%* 18

COMBINED MODULE 9% 7%** 18

42

Summary

Trade studies, analyses, and simulations were performed in

the design and production of sandwich module prototypes

for space solar power

A novel approach for increasing thermal dissipation

capabilities in modular space solar architectures was

explored

The first-ever sandwich module testing under space-like

conditions was conducted

This work provides an empirical basis for informing technical

and economic analyses for a prominent class of space solar

systems

Thank You

for Your Time

and Attention

Paul.Jaffe@nrl.navy.mil

44

Backup Charts

45

Historical Survey of Some SSP Concepts

NASA/DOE SPS Reference System, circa 1978

SPS 2000 Japanese LEO concept, circa 1994

SunTower LEO/MEO/GEO concept, circa 1999

Peter Glaser GEO concept, circa 1968

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en.gyTransmiuion •UGHl(~ I

46

System Blocks and Historical Efficiencies

Image from 1980 DOE/NASA report

~ '

~ - SOLAR DISTAHCE .9675

\~~-----SEASONAL VARIATION .91

{ .1455 (Si, CRl) ,1437 (GaAs, CR2) SOLAR ARRAY

SOLAR~.H-t-+-t-H ARRAY t-t-H-~ ~ ------ ARRAY POWER .DISTRIBUTION .9368

------- ANTENNA POWER DISTRIBUTION .963

TRANSMITTING --1lt~========-.:DC-Rf CONVERSION .85 ANTENNA ANTENNA • 9653

AOOSPHERE .98

_,_ __ RF-DC CONVERSION .89

.---- GRID INTERFACE .97

POWER GRID-I

23 W107 W 30 W 24 W

1 W6 W

47

Heat Dissipation for One Sun Incident28 cm x 28 cm Module Area

70 W

Solar Cells

30% efficient

DC-to-RF

80% efficient

Antenna

95% efficient

Reflected light

Incoming

sunlight

Power

sent

to the

ground

Total heat power to

be dissipated: 77 W

Combined module

efficiency: 23%

Efficiency estimates are optimistic, especially for DC-to-RF, and neglect power distribution and other losses

Module Architecture Trade Study

Shape should tessellate in order to form arbitrarily large

surfaces. Candidates: triangles, squares, hexagons

Hexagons make best volumetric use of a cylindrical

payload fairing. Cross-sectional area coverage: triangle

~41%, square ~64%; hexagon ~83%

However, as PV cells are generally available as

rectangular shapes, higher module percentage

coverage is provided by a square vs. a hexagon

Additionally, since launch vehicles tend to be mass-

limited instead of volume-limited for a given payload

fairing accomodation, optimizing the use of volume is

important only for the very lowest density payloads

Thus, a square module shape is likely favored

48

49

An Approach To Increase Radiator Area

The “sandwich module” disc is replaced by an open-top conical graphite structure

“Stepped”

Sidewall

Reflective

inner film

PV panel

Waste heat radiator area

is increased

Structure wall is

high-conductivity

graphite composite

Use an aperture constructed of step-shaped modules

Increased radiator area vs. flat module, giving lower operating temps

Heat rejection area can be increased arbitrarily, but at the cost of structure mass and increasing distance from the primary heat source

Two-phase heat pipes could be used for heat transport within and between modules, but complexity would increase

l

Photovoltaics Trade Study

Trade factors: Temperature performance characteristics, Concentration ratio tolerance,

Efficiency, Power output/mass, High voltage capabilities, Can I actually buy it?

– 43.5% efficient cells under hundreds of suns for a fraction of a second in the lab are not

applicable to the prototype; 35.8% one-sun efficiency cells are likewise not commercially

available, even for space

Higher efficiency cells (~30%) are likely worth the cost

– PV is the most inefficient link in the chain, want to minimize loss

– Higher efficiency PV also helps reduce the thermal problem

– Now possible to get very lightweight triple junction cells

Manufacturers: Emcore and Spectrolab

50

ZTJ Photovoltaic Cell Advanced Triple-Junction Solar Cell for Space ApplicatlOOS

DATASHEET SPACE PHOTOVOLTAICS

Typical Performance Data ■ ,___. ___ (1~1-o:n

lnE!loencyit~l'l:IM,-Ft.t 29W.

,,,., J..i. l1 4 ml,/w

H IV

J. 1HIIIMJ!r'

29.5% Minimum Average Efficiency Qualified & Characteozed to the AIAA•SI 11-2005 & AIAA-S112-2005 Standarck

Features & Characteristics

■ Lowest solar cell mass of 84 mg/cm2

■ 3rd Generation Triple-Junction (ZTJ) lnGaP/lnGaAs/Ge Solar Cells

with n-on-p Polarity on 140-µm Uniform Thickness Substrate

■ Fully space-qualified with proven flight heritage

■ Excellent radiat ion resistance with P/Po = 0.90 0 1-MeV, SE14 e/cm2

fluence

■ Designed to accept corner-mounted silicon bypass diode for

invidua l cell reverse bias protection

SPECTROLAB A BOEING COMPANY

29.5% NeXt Triple Junction (XT J) Solar Cells

Features

• Small and large cell sizes offered for optimum pacioog factor and cost competitiveness

• Gcostollonary Orbit (GEO) missKll'I qualified • 29.5% efficiency (mn average@ mJX power, 2s•c, AMO) • 29.3% efficiency (mfl. average@ load, 2s•c, AMO) • Discrete S1 bypass dlOdc protection • Available as CIC assembly (Ccn.1ntcrconooct-Cov«glass

with diode) for ease of integration or delivered on completed solar panels (see Panel Data Sheet)

• L.>rgc area cclVCIC (59.65anZ) quallftcabon 111 progress

I l

Key Qualification Results

• Completed 2,000 GEO quahlicallon cycles, including Combined Effects Test

DC-RF Conversion Trade Study

Solid State

Power Amps

are light,

available,

and easy to

phase control

51

Method GaN SSPA Magnetron TWT MBK

Efficiency 43-70% 44-73% 66-70% 50%*

Mass (kg) <0.1 0.9-4.3 0.7-3.0 1.0*

Power Output (W) 25-220 900-5,000 20-300 1,000*

Input voltage (V) 28-50 4,000-20,500 5,000-20,000 2,000-4,000*

Manufacturers Cree, TriQuint Toshiba, Hitachi L3, Thales CCR

SSPA=Solid State Power Amplifier, TWT = Traveling Wave Tube, MBK = Multiple Beam Klystron. Values (except

for MBK) taken from data sheets of potential models in the 2-10GHz frequency range, some available from

Richardson Electronics. Masses exclude voltage conversion components. *rough estimates

CGH55030F2 / CGH55030P2 25 W, C-band, Unmatched, GaN HEMT

Cree's CGH55030F2/ CGH55030P2 is a gallium nit r ide (GaN) high electron

mobil it y transistor (HEMT) designed specifically for h igh efficiency, high

gain and wide bandwidth capabilit ies, which makes t he CGH55030F2/

CGH55030P2 ideal for C-band pulsed or CW saturated amplifiers. The

transistor is available in both screw-down, flange and solder-down,

pill packages. Based on appropriate external match adjustment, t he

CGH55030F2/ CGH55030P2 is suita ble for applications up to 6 GHz.

FEATURES

• 4.5 to 6.0 GHz Operation

• 12 dB Small Signal Gain at 5.65 GHz

30 w typical P ,.,

60 % Efficiency at PSAT

• 28 V Operation

APPLICATIONS

2-Way Private Radio

Broadband Amplifiers

Cellular Infrastructure

Test Instrumentation

Class A, AB Amplifiers for Drivers and

Gain Blocks

CGH40180PP 180 W, RF Power GaN HEMT

Cr"H's CGH-40 t 80PP Is an unmatched, gallium nitride (G&N) high

electron mobility tnmslstor (HEMT). The CGH40180PP, operati"'.l

from a 28 volt rail, offers a general purpose, broadband solut ion to

a vark!ty of RF and microwave appllcatlons. GaN HEMT1 offer high

efficiency, high gain and wide bandwidth capabllltles making the

CGH40180PP Ideal for noear and compressed ampHfler circuits.

The translst« Is avallable In a 4 ·1ead flanoe packaoe.

CREE•

FEATURES APPLICATIONS

Up to 2.5 GHz Operation

20 dB Small Signal Gain at 1.0 GHz

15 dB Small Signal Gain at 2.0 GHz

220 w typical P !.I.I

70 % Efficiency at P s.1i,

28 V Operation

2-Way Private Radio

Broadband Amplifiers

Cellular Infrastructure

Test Instrumentation

Class A, AB, Linear amplifiers suitable

for OFDM, W-CDMA, EDGE, CDMA

wavefonns

Trade factors: Mass, Usability as thermal radiator, Efficiency, Ease of use in an array, Compatibilitywith Mechanical Design

Array element options

– Type

• Patch, helix, slots, dipole, X-dipole, etc.

– Polarization

– Spacing of elements

– Number of elements per module

– Sub array characteristics

Beam forming considerations

– Signal distribution

• Coax, waveguide

Diagram Source: Kawasaki, S., "A Unit Plate of a Thin, Multilayered Active Integrated Antenna for a

Space Solar Power System," URSI Radio Science Bulletin, No. 310, September 2004, pp. 15-22

Antenna Trade Study

52

53

Characterization of Power Added Efficiency Performance

of Final Stage Amplifier

Region of Interest

20 80%

18 70% -II)

:t 16 ('t,

3: 60% -14 ,._

QJ

3: 0 12 0..

50%

"'C QJ

- Power Diss ipated ta 10 a. - Power Added Efficiency 40% II) II)

8 C - Out put Power

30% "'C C: ('t, +"

6 :::s a. 20%

+,,I 4 :::s 0

2 10%

0 0%

5 10 15 20 25 30 35

Input Power (dBm)

Data Sheet for Cells Used for ModulesSPECTROLAB A BOEING COMPAN) S P E C T R O L A B A BOEING COMPANY

28.3% Ultra Triple Junction (UT J) Solar Cells

Features

• Small and large cell sizes offered for optimum packing factor and cost competitiveness

• All sizes qualified for LEO and GEO missions

• Discrete Si bypass diode protection

• Performance for ceEs <32 cm' is 28.3% efficiency (min. average@ max power, 28°C, AMO)

• Performance for ceEs >50 cm' is 27 .7% efficiency (min. average @ max power, 28°C, AMO)

• Available as CIC assembly (Cell-lnterconnect-Coverglass wi1h diode) for ease of integration or delivered on completed solar panels (see Panel Data Sheet)

Product Description

Substrale

Solar Cell Structure

Method

Device Design

Standard Sizes

Assembly Method

CIC Assembly

Germanium

GalnP,/GaAs/Ge

Metal Organic Vapor Phase Epitaxy

Monolithic, two terminal triple junction. nip GalnP,, GaAs, and Ge solar cells interconnected with two tunnel junctions

26.62cm' and 59.65cm' are most cost effective and common standard sizes; other sizes available

Welded

Coverglass thickness range from 3 mils lo 30 mils wrth various coatings. Interconnects available wrth either out-of-plane or in-plane slress relief

©2010 Spectrolab, Inc All Rights Reserved

lt

Cells shown wilb nte,r;onnec;,;, coverglass, and bypass diode

Key Qualification Results

Geostationary Orbit (GEO) 115,550 cycles

Multiple Interplanetary Missions: Mars, Jupiter, Asteroid

ESD Survivability Tested to ISO Standard

Heritage

• More than 2.6 million multi-junction cells delivered

• More than 820 kW of multi-junction arrays on orbit

• Large area cell (59.65crn') delivered on solar panels for 25 satellites (LEO constellation)

• 1 MW annual capacrty - cells and panels

Intellectual Property

This product is protected by Speclrolab's portfolio of patents including the foUowing:

• 6,150,603 • 7,119,271 • 6,255,580 • 7,126,052

• 6,380,601

Specifications Subject to Change Without Notice

LS . .061 ll'T •• - "

i.'1/~' llO'I/IIIL',-~J. M.l~~CllHJ,.'l' iYHDI Ct•llnt.91Vl>'I/I' A~~~P.Q = l$014001 =

Spectrolab, Inc. 12500 Gladstone Avenue, Sytmar, Califom1a 91342 USA • Phone 818 365 4611 • fAX: 818 361 5102 Webs~e ~

28.3% Ultra Triple Junction (UT J) Solar Cells

Typical Electrical Parameters (AMO (135.3 mWlan12s·c, Bare Ce/lj

Parame/BfS <32ctrP >50ctrP

Jsc 17.05mNcm' 17.0S mNcm'

Jmp 16.30mNcm' 16.JOmNcm'

J1oad mr...11"9 16.40mNcm' 16.40 mNcm'

Voe 2.660 V 2.660V

Vmp 2.350 V 2.300V

Vload 2.310V 2.270V

Cit 0.85 0.83

Eflload 28.0% 27.5%

Effmp 28.3% 27.6%

Radiation Degradation (Fluence 1MeV Electrons/cm')

Parameters 1x10" 5x10" tx10"

lmpnmpo 0.99 0.98 0.96

VmpNmpo 0.94 0.91 0.89

PmpiPmpo 0.93 0.89 0.86

Thermal Properties

Solar Abso,ptance= 0.92 (5 mil CMG/AR, 0.90 for bare cells)

Emittance (Normal)= 0.85 (Cena Doped Microsheet)

Weight 84 mg/ cm' (Bare) @ 140 µm (5.5 mi) Ge wafer thk:kness

Temperature Coefficients rwc-eo·c1 (F/uence 1MeV Electrons/cm')

Typical IV Characteristic AMO (135.3 mW/cm') 28°C, Bare Cell

18 16 14 12 10 8

6 4 2

0 0 0.5 1 1.5 2

Voltage (V)

r.,C11:MP1

Tunnel Junction j o Middle Coll: GaAa

i ....................... -➔ I

\ I I

2.5 3

Parameters BOL 5x10" 1x10"

Jmp (µAlcm'rC) 1.2 5.3 6.9

The information conta ined on this sheet is for reference only. Specifications subject to change without not ice.

Jsc (µAlcm•rc)

Vmp (mVrC)

voe (mv1·ci

ISO "IGIIT ■ - ■ D

Revised 101512010 5.3 6.5 6.9

-6.5 -6.7 -6.8 © 2010 Spectrolab, Inc All Rights Reserved

-5.9 -6.3 -6.5

= 11014001

Spectrolab, Inc. 12500 Gladstone Avenue, Sytmar, Caritom1a 91342 USA •Phone8183654611 •FAX 8183615102 Webs~e ~

Power Electronics Block Diagram

55

Power Electronics Board

Solar Array Blocking

Output Diodes

2 strings x 78 cells Switches Vdd

28V Bus ® 39W

Vbias optional Input ® i 8.7W

Filter Synchronous Vose

Buck 5V

0 i 250mW Converter LT3891 Vtune

® i 10mW

+5V Status LED

i Vgg

Output Status LED 0 150mW Cuk Converter -5V

LT3580 Output On Switch Power

Sequence

Output Off Switch Logic

56

Back of Solar Array with Thermal Features

Black

Kapton

Tape

Thermocouple

Wire Bundle

57

Tile Module Power and RF Electronics

Baseplate Integrated with Solar Array

Test Workstation

58

Solar Array Simulator

PC with LabView

RF

Attenuator

USB

Power

Meter

Test BoxData Acquisition

Unit

Spectrum

Analyzer

Thermal Vacuum Chamber

Tile Module Power and RF

Electronics Testing

59

Sandwich Module Functional Diagram

60

Frequency & Phase

Information

Pilot Signal Receive

Antenna

Pilot Signal

Photovoltaics

DC Power Conversion

RF Amplification & Phase Shifting

Output Filter

Power Transmit Antenna

Power Beam

Sandwich Module Functional Diagram

Showing Elements Implemented

61

-

-

Frequency & PRase

I Af8FR9atieA •

Pi let SigAal Receive

AAteAAa

Poot SigAal

~

~ ~

Simulated Sunlight ,,,__ ~ -

w

Photovoltaics

y

DC Power Conversion

y

RF Amplification & Phase Shifting

• Output Filter

-•-Power Measurement

TFaASR9it AAteAAa

... PeneF BeaR9

,

Temperature Effect on I-V Curves at About One Sun

62

0.7

0 .6

0 .5

< 0 .4 -.... C:

~ I.. :::, u 0.3

0 .2

0 .1

0 .0

0 5

- 1-V Curve @ 82 .8°C

- 1-V Curve@ 87 .3°C

- 1-V Curve @ 92 .7°C

- 1-V Curve @ 96.5°C

- 1-V Curve @ 102 .0°C

10 15 20 25 30 35

Voltage (V)

Tile Module Integration and Testing Flow

63

PV

Power

DC-RF

Antenna or

Mockup

Mass Properties

Power Electronics

Functional Test

DC-RF Electronics

Functional Test

Mass Properties

Mass Properties

Mass Properties

Ambient Sun Concentration

1-VCurves

Mass Properties

Wheeler Cap Efficiency Test

(for actual antenna only )

Thermal Features &

Sensors Installs

Solar Array Simulator

Power Test

Thermal Features &

Sensors Installs

Ambient Illumination Power Test

T-Vac Illumination Power Test

Mass Properties

Xenon Lamp & Solar Spectral Power Distribution

64

Fused Silica Spectral

Transmissivity

- lYU E C:

;:;-.. 4 E 80 ...... -! c ... ·= 60 -QJ 3 .:;; ;: ..,.. 0 e C. .,:, 40 =

Ni = F

2 2{1

0

1 ~ • 1

~~A A --

0 I I I I I I I I

350 600 850 1100 1350 1600 1850 2100 2350 Wavelength (nm)

- 2.5--------------------------------~ E C: -r--.1

E 3:

2

cu 1 .5 .._, C: t'O

~ 1 ..... ..... 0 . 5

UV

0 250

Visible , Infrare d ----

Sunlight at Top of the Atmosphere

/ S2S0° C Blackbody Spectrum

Radiation at Sea Level

Absorption Bands H20 CO2

500 750 1000 1250 1500 1750 2000 2250 2500

Wavelength (nm)

I

I. I -ll ,

I I I I I I I I I I I I

' I I

r u .2 .3 .5 .6 .7 .8 .9 1.0 2 .0 3. 10

Wav,e I eingth ( µm)

Beam Uniformity Maps

65

One Lamp Two Lamps

Beam uniformity varies with lamp focus setting and other factors

2.60 2.780 2.89 2.93 3.08 3.25 3.25

3.01 3.19 3.12 3.32 3.31 3.37 3.40

_1. 2 ____ _1. 41 ____ _1. 53 3.20 3.21 3.15 3.18 3.00 3.19 3.06 ... -,"!~'

1.24 1.39 1.47 2.82 2.86 2.89 2.81

Goubau and Schwering Method of

Finding Beam Collection Efficiency

66

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 0.5 1 1.5 2 2.5 3

Co

llect

ion

Eff

icie

ncy

(%)

t

Calculated

Measured

Using GEO (36,000km), 1500 m Tx diameter, and 2.45 GHz assumptions with a 7.5

km diameter receiving area provides a τ of about 2, > 95% collection efficiency

-~

/ / ,

I I • I ,

J /

One-way Sea Level to Zenith Attenuations

in Clear Sky Conditions

67

0.001

0.01

0.1

1

10

100

1000

0 20 40 60 80 100 120 140

Ze

nit

h A

tte

nu

ati

on

(d

B)

Frequency (GHz)

Total Water Vapor Dry Air

1013 hPa pressure

15°C temperature

7.5 g/m³ water vapor density

94

35

5.8

2.45

~ ----- - - I I '

r • .. .. " I ..... _ , ' ~ -" 1 _ -· ·---- ~ ··-. -,,_ -- - I .. .. -. 1 - - --- .. -

J . '• , ~_, --'.J "~- .--...ill i--- ....

.. l

I - -

I

'

SPS Systems Designs Considered in URSI Report

68

Model Old JAXA mode l JAXAI mode l JAXA2 Model A A-DOE

model Frequency 5.8 G Hz 5.8 GHz 5.8 G Hz 2.45 GHz

Diameter of transmitting 2.6 km I km 1.93 km l km antenna (TX)

A mplitude taper 10 dB Gau 1an 10 dB Gaussian 10 dB Gau ssian 10 dB Gaus ian

Output power 1.3 GW 1.3 GW l.3 GW 6.72 GW

(beamed to earth)

Maximum power ? ? 114 mW/cm2 ?

density atTX center 63 mW/ cm- 420 mW/cm- 2.2 WI cm-

Minimu m power 6.3 mW/ cm

2 42 mW/ c m

2 ll.4mW/cm.2 0.22 WI cm

2

de nsity atTX center Antenna spacing 0 .75 'A, 0.75 'A, 0.75 l 0.75 'A,

Power per one antenna Max. 0 .95 W Max. 6. IW Max. 1.7 W Max. 185 W

umber of (3.54 bill ion) (540 million) ( 1.950 million) (97 mi Ilion) e lements)

Rectenna 2.0 km 3.4 km 2.45 km IO km

Diameter

Maximum Power 180 mW/cm2 26 mW/cm2 100 mW/cm2 23 mW/cm2

density at rectenna

Collection 96.5 % 86 % 87 % 89 %

Efficiency

Simplified Levelized Cost of Energy (LCOE)

for Space Solar Power

69

LCOE COL+CSS

MSP*TSL

Input Unit

Mass-specific transmitted power of conversion element, MSP W/kg

Total on-orbit service life, ISL years

Cost of launch to low earth orbit, COL $/kg

Cost of conversion element space segment, CSS $/kg

Inputs Case 1 Case 2 Case 3 Case4

Mass-specific power (W /kg) 5 20 80 200

Total service life (years) 20 25 30 35

Cost of launch ($/kg) 2,500 1,000 500 100

Cost of space segment ($/kg) 10,000 5,000 1,000 100

Output

Levelized cost of energy ($/kWh} 15.84 1.37 0.07 0.0033

Comparison of Levelized Cost of Energy

for Various Means of Power Generation

70

Capacity Levelized Variable Total

O&M Transmission System Plant Type Factor Capital Fixed O&M

(including Investment Levelized {%) Cost

fuel) Cost

Natural Gas: Advanced Combined Cycle 87 17.9 1.9 44.4 1.2 65.4

Natural Gas: Conventional Combined Cycle 87 17.5 1.9 48.0 1.2 68.6

Hydro 53 76.9 4.0 6.0 2.1 89.0

Wind 34 83.3 9.7 0.0 3.7 96.7

Conventional Coal 85 65.8 4.0 28.6 1.2 99.6

Geothermal 92 76.6 11.9 9.6 1.5 99.6

Advanced Coal 85 75.2 6.6 29.2 1.2 112.2

Advanced Nuclear 90 88.8 11.3 11.6 1.1 112.8

Biomass 83 56.8 13.8 48.3 1.3 120.2

Advanced Coal with CCS 85 93.3 9.3 36.8 1.2 140.6

Solar PV 25 144.9 7.7 0.0 4.2 156.8

Solar Thermal 20 204.7 40.1 0.0 6.2 251.0

Solar Power Satellite Case 1 90 15,844.0 0.0 0.0 0.0 15,844.0

Solar Power Satellite Case 2 90 1,368.9 0.0 0.0 0.0 1,368.9

Solar Power Satellite Case 3 90 71.3 0.0 0.0 0.0 71.3

Solar Power Satellite Case 4 90 3.3 0.0 0.0 0.0 3.3

Comparison of JP-8 Cost per Gallon with $/kWh

Equivalents and SPS Cases

71Range of reported “Fully Burdened Cost of Fuel” values is $3 to $400 per gallon

$/(Gallon of JP-8) $/kWh 3.75 0.10 .. 0.07 SPS Case 3 7.51 0.20

15.02 0.40

22.53 0.60

30.03 0.80

37.54 1.00

45.05 1.20

52.56 1.40 .. 1.37 SPS Case 2 60.07 1.60

. . . ... 450.51 12.00

. . . ... ~ 15.84 SPS Case 1