Mark O Neill, LLC P.O. Box 2262 Keller, TX USA

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Space Photovoltaic Concentrator Using Flat Glass/Silicone Fresnel Lenses, 4-Junction IMM Cells, Graphene-Based Radiators, and Articulating Photovoltaic Receivers Mark O Neill, MOLLC, Keller, Texas A.

1 Space Photovoltaic Concentrator Using Flat Glass/Silicone Fresnel Lenses, 4-Junction IMM Cells, Graphene-Based Radiators, and Articulating Photovoltaic Receivers Mark O Neill, MOLLC, Keller, Texas A.J. McDanal, AJMLLC, Emory, Texas Henry Brandhorst, Carbon-Free Energy LLC, Auburn, Alabama Brian Spence, Deployable Space Systems, Inc., Goleta, California Shawn Iqbal, Deployable Space Systems, Inc., Goleta, California Paul Sharps, SolAero Technologies, Inc., Albuquerque, New Mexico Clay McPheeters, SolAero Technologies, Inc., Albuquerque, New Mexico Jeff Steinfeldt, SolAero Technologies, Inc., Albuquerque, New Mexico Michael Piszczor, NASA-GRC, Cleveland, Ohio Matt Myers, NASA-GRC, Cleveland, Ohio NASA SPRAT XXIV Cleveland, Ohio September 22, 2016 Mark O Neill, LLC P.O. Box 2262 Keller, TX USA markoneill@markoneill.com Mark O Neill, LLC

2 Background 2016 Mark O Neill, LLC Slide 2

$Refractive Concentrators for Space Power A Long Heritage$ Array on PV Array Space Power Plus (PASP-Plus) Provided

$with Refractive Linear Element Technology (SCARLET) 2.$ 5 kw Array on Deep Space 1 Performed Flawlessly for

Triple-Junction Cells Stretched Lens Array Invented in

on TacSat 4 Demonstrated Less than ½ the Degradation Rate

Lens Mechanical Failure (Problem Now Solved) Developed in

2003-2014: Ultralight SLA (>300 W/m 2, >350 W/kg, >80 kw/m

3 Refractive Concentrators for Space Power A Long Heritage of Success with 1 Glitch Launched in 1994: Mini-Dome Lens Array on PV Array Space Power Plus (PASP-Plus) Provided Best Performance and Least Degradation of 12 Advanced Solar Arrays Launched in 1998: Solar Concentrator Array with Refractive Linear Element Technology (SCARLET) 2.5 kw Array on Deep Space 1 Performed Flawlessly for 38-Month Mission on First Spacecraft Powered by Triple-Junction Cells Stretched Lens Array Invented in 1998 Launched in 2011: SLA Technology Experiment (SLATE) on TacSat 4 Demonstrated Less than ½ the Degradation Rate of One-Sun Cells During First 6 Months on Orbit Before Lens Mechanical Failure (Problem Now Solved) Developed in : Rigid Panel Version of SLA Developed in : Ultralight SLA (>300 W/m 2, >350 W/kg, >80 kw/m 3 ) Developed in : Flexible-Blanket Version of Stretched Lens Array (SLA) 2016 Mark O Neill, LLC Slide 3

Basic Building Block of New Concentrator New 10 cm x 10 cm Flat Color-Mixing Fresnel Lens Comprising a Single Sheet of 50 µ CMG Glass with 100 µ Tall Silicone Prisms Molded onto the Bottom Glass

4 Basic Building Block of New Concentrator New 10 cm x 10 cm Flat Color-Mixing Fresnel Lens Comprising a Single Sheet of 50 µ CMG Glass with 100 µ Tall Silicone Prisms Molded onto the Bottom Glass Surface Forming Two 4X Line-Focus Lenses 25 µ Graphene Sheet Waste Heat Radiator with 25 µ Silicone Coating on Both Sides to Enhance Emittance 4-Junction IMM Cells with Optimized Grid Pattern for 4X Concentration Profile and Appropriate Encapsulation and Front and Back Shielding for Mission Requirements 2016 Mark O Neill, LLC Slide 4

5 New Lens 2016 Mark O Neill, LLC Slide 5

6 New Color-Mixing Lens Design Approach Minimizes Chromatic Aberration Loss in 4-Junction IMM Cell Old Approach from SCARLET Period (1996) Used Color Mixing by Each Pair of Neighboring Prisms. New Approach Uses Color Mixing by Each Triplet of Neighboring Prisms with Better Mixing. Old Chromatic Aberration Model for 2- Junction Cells Has Been Extended to 4- Junction IMM Cells Assuming a Conservative 500 ohms/square resistance between junctions. Alex Haas (SolAero) and Sarah Kurtz (NREL) Were Consulted about this Resistance Value and this Extended Model. Both Thought 500 ohms/square Is Conservatively Large. Chromatic Aberration Power Loss for this Case < 1% Mark O Neill, LLC Slide 6

Three New Types of Robust Lenses Embedded Metal Mesh Silicone Lens

with Silicone Prisms All Three Lens Types Have Been Measured to Have

A Combination of the Glass and Mesh Approaches Is Also Under

7 Three New Types of Robust Lenses Embedded Metal Mesh Silicone Lens Patent Pending 50 Micron Ceria- Doped Microsheet Glass Superstrate with Silicone Prisms All Three Lens Types Have Been Measured to Have a Net Optical Efficiency of Over 90% for Zero Beta Angle. A Combination of the Glass and Mesh Approaches Is Also Under Consideration Transparent Film Superstrate with Silicone Prisms 2016 Mark O Neill, LLC Slide 7

New Lens Design with Articulating Receiver Enables Single-Axis Tracking with ± 50 Beta Angle Tolerance Patent Pending Lens Outdoor Measurements for Lens with 50 micron CMG Superstrate and 100 Micron

8 New Lens Design with Articulating Receiver Enables Single-Axis Tracking with ± 50 Beta Angle Tolerance Patent Pending Lens Outdoor Measurements for Lens with 50 micron CMG Superstrate and 100 Micron Silicone Prisms Focusing Onto 4-Junction IMM Cell 50º Beta Receiver Position 0º Beta Receiver Position A video showing more views is available at Mark O Neill, LLC Slide 8

0º Beta Above, 25º Beta Upper Right, 50º

9 Simple Method of Following Articulation Path Photos Clockwise from Above Showing Increasing Beta Angle Accommodation with Offset 4-Bar- Linkage Rotation. 0º Beta Above, 25º Beta Upper Right, 50º Beta Lower Right Mark O Neill, LLC Slide 9

features such as alignment holes for assembly into carbon fiber

10 Electroformed Mesh Suggested by Geoff Landis Offers Many Advantages Only 50 microns thick 97% open area Border can have features such as alignment holes for assembly into carbon fiber peripheral frame or graphene peripheral frame 2016 Mark O Neill, LLC Slide 10

11 New Strengthened Material Approaches Save Mass and Make More Robust Lens 2016 Mark O Neill, LLC Slide 11

12 Radiation Testing of Lens Materials 2016 Mark O Neill, LLC Slide 12

13 Photograph of 8 Samples After High-Energy Proton Exposure (Very Little Optical or Mechanical Change) Tested at Auburn University at 2.7 MeV protons through backside at 5x10 12 p+/cm 2 25µ PET (Mylar)/100µ Silicone 25µ Colorless Polyimide/ 100µ Silicone 25µ FEP (Teflon)/100µ Silicone 25µ ETFE (Tefzel)/100µ Silicone 100µ Glass Mesh Embedded in 200µ Silicone 200µ Monolithic Silicone 50 Micron CMG/100µ Silicone 100µ Aluminum Mesh Embedded in 200µ Silicone 2016 Mark O Neill, LLC Slide 13

14 Spectral Transmittance Before and After High-Energy Proton Exposure (2.7 MeV proton through backside at 5x10 12 p+/cm 2 ) CMG Superstrate/Silicone Aluminum Mesh Embedded in Silicone 2016 Mark O Neill, LLC Slide 14

15 Photos of Low-Energy Proton Samples Tested by Scott Messenger in Japan 2016 Mark O Neill, LLC Slide 15

16 AFRL Measurements of Transmittance Before and After Low-Energy Proton Exposure 2016 Mark O Neill, LLC Slide 16

17 The Low-Energy Proton Samples Were Uncoated A UVR Coating Would Minimize Surface Damage Degradation Was Minor Except at the Highest Dose of 1E16p + /cm 2 of 30 kev Protons The UV-Rejection Coating Which We Have Used Successfully on Silicone Lenses Since PASP+ in Would Intercept Most of the Low-Energy Protons and Protect the Silicone from Damage We Therefore Think the Silicone Lens with Embedded Metal Mesh Is Viable with the UV-Rejection Coating 2016 Mark O Neill, LLC Slide 17

18 New Graphene Radiator 2016 Mark O Neill, LLC Slide 18

Graphene Described in the Nobel Prize Press Release from 2010 In our 1 m 2 hammock tied between two trees you could place a weight of approximately 4 kg before it would break.

19 Graphene Described in the Nobel Prize Press Release from 2010 In our 1 m 2 hammock tied between two trees you could place a weight of approximately 4 kg before it would break. It should thus be possible to make an almost invisible hammock out of graphene that could hold a cat without breaking. The hammock would weigh less than one mg, corresponding to the weight of one of the cat s whiskers. Source: Scientific Background on the Nobel Prize in Physics GRAPHENE compiled by the Class for Physics of the Royal Swedish Academy of Sciences -- October 5, Mark O Neill, LLC Slide 19

20 Radiator Material Considerations (Patent Pending for Space PV Concentrator with Graphene Radiator) Until recently, the best radiator material from thermal, mass, and strength considerations was composite sheet made with carbon fiber fabric, and the second-best material was aluminum sheet with an oxide coating to improve emittance. Recent developments in graphene sheet have brought this new radiator material to the forefront. As shown in the table below, graphene offers unprecedented thermal, mass, and strength properties. Material Carbon Fiber Composite Sheet Effective Thermal Conductivity, k (W / m-k) Density, ρ (kg / m 3 ) Tensile Strength (MPa) k/ρ (W-m 2 / kg-k) 240 1,750 1, Aluminum Sheet 200 2, Graphene Sheet 1,600 2, Mark O Neill, LLC Slide 20

Graphene Is an Atomic-Scale Hexagonal Lattice Made of Carbon Atoms Andre Geim and Konstantin

groundbreaking experiments regarding the two-dimensional material graphene.

Electrical Conductivity: 12,000 S/cm Tensile Strength: 100 MPa Max Operating Temperature:

21 Graphene Is an Atomic-Scale Hexagonal Lattice Made of Carbon Atoms Andre Geim and Konstantin Novoselov at the University of Manchester won the Nobel Prize in Physics in 2010 "for groundbreaking experiments regarding the two-dimensional material graphene." Angstron Materials Thermal Foil In-Plane Thermal Conductivity: W/(m-K) In-Plane Electrical Conductivity: 12,000 S/cm Tensile Strength: 100 MPa Max Operating Temperature: 400 C in air Density: 2.2 g/cc Thickness: 25 µm and 40 µm < 10 /cm 2 Retail for 1 Sheet 2016 Mark O Neill, LLC Slide 21

22 Strengthening the Graphene Sheet and Adding Emittance-Enhancement Silicone Coating An Aluminum Mesh Has Been Added to the Graphene Sheet Using Silicone as Both Adhesive and Emittance- Enhancement Coating for Graphene Sheet 2016 Mark O Neill, LLC Slide 22

23 Graphene Emittance With and Without Silicone Coating (AFRL Measurements) 2016 Mark O Neill, LLC Slide 23

24 Figures from Pending Patent 2016 Mark O Neill, LLC Slide 24

25 Graphene Sheet Will Work Well for Line-Focus and Point-Focus Concentrators 5 cm Wide Line Focus 25 µ Thick 10 cm x 10 cm Point Focus 40 µ Thick 2016 Mark O Neill, LLC Slide 25

26 New IMM Cell 2016 Mark O Neill, LLC Slide 26

New 4-Junction IMM Cells in 3-Cell Receiver Circuit SolAero Produced a Trial Run of Cells with Average 1-Sun AM0 Efficiency of 31% for Total Cell Area Including Busbar and

27 New 4-Junction IMM Cells in 3-Cell Receiver Circuit SolAero Produced a Trial Run of Cells with Average 1-Sun AM0 Efficiency of 31% for Total Cell Area Including Busbar and Tab-Covered Area. On Active Area Basis, Average 1-Sun Cell Efficiency Would Be 33%. At 4X Concentration, Average Cell Efficiency Would Be 35% Mark O Neill, LLC Slide 27

28 Concentrator Test Module for Ground and Lear Jet Testing 2016 Mark O Neill, LLC Slide 28

29 Test Module Sketch 2016 Mark O Neill, LLC Slide 29

30 Module Under Outdoor Test 2016 Mark O Neill, LLC Slide 30

31 Integration of New Flat Lens Architecture into Deployable Space Systems SOLAROSA Platform 2016 Mark O Neill, LLC Slide 31

Flat Lens Engineering Development Unit (EDU)

lenticular springs Straps carried in tension.

Lenticular springs hold lens deck up off of

Small lanyard sets deployment position of

32 Flat Lens Engineering Development Unit (EDU) with Lenticular Springs Kevlar straps with lenticular springs Straps carried in tension. Lens bonded to Kevlar straps. Lenticular springs hold lens deck up off of cells. Small lanyard sets deployment position of lenticular springs. EDU unit developed to investigate kinematics and potential for safe stow Mark O Neill, LLC Slide 32

33 Flat Lens Engineering Development Unit (EDU) with 4-Bar Linkage Deployable 4-bar linkage: Integrated with 4-bar linkage to deploy lenses off of cell deck. Lenses bonded to small brackets at corners Small springs and hard-stops in cell-deck brackets set max deployment of lens-deck 2016 Mark O Neill, LLC Slide 33

34 Effect of New Lenses and Radiators on Specific Power 2016 Mark O Neill, LLC Slide 34

35 Lens + Receiver + Radiator Areal Mass Density for Heavily Shielded Receiver Areal Mass Density for 4X Line-Focus SLA with Glass/Silicone Lens, Graphene Radiator Sheet, and Photovoltaic Receiver Elements for IMM Cell with 150 micron (6 mil) Equivalent Cover Glass Shielding Front and Back Major Subsystem Geometric Concentration Ratio Aperture Width Element 4.00 X Physical Concentration Ratio 3.03 X 5.00 cm Cell Width 1.45 cm Element Area per sq.m. Aperture Thickness Density Receiver Width Mass/ Aperture 1.65 cm Subtotals: Mass/Aperture (sq.m.) (cm) (g/cu.cm.) (kg/sq.m.) (kg/sq.m.) Lens 50 micron CMG/50 micron Silicone Radiator Silicone-Coated Graphene Radiator CMG Microsheet Cover Glass Cover Glass Adhesive Receiver IMM Cell Glass Carrier Thermally Conductive Adhesive Total Areal Mass Density: kg/sq.m. New 92% Lens with New 35% Cell with Reasonable Knock-Down Factors Should Yield About 380 W/m 2 Areal Power Density for Higher Earth Orbits. With Lens + Receiver + Radiator Mass Shown Above, About 900 W/kg for the New Concentrator Blanket Is a Realistic Target. This Does Not Include Harnesses or Deployment and Support Structure Just the Three Key Blanket Elements Mark O Neill, LLC Slide 35

36 Conclusions and Acknowledgement 2016 Mark O Neill, LLC Slide 36

37 Conclusions Robust New Lens Has Been Developed for Future Missions 5.0 cm Wide Flat Lens for 4.2X Geometric Concentration Ratio (GCR) Leading Material Approach: Ceria-Doped Glass Superstrate Supports Silicone Prisms Alternate Material Approach: Embedded Mesh Supports Silicone Lens New 4-Junction IMM Cell Has Been Developed, Improving Efficiency and Reducing Mass New Graphene Radiator Has Been Developed, Improving Performance and Reducing Mass New Articulating Receiver Approach Has Been Validated, Enabling Single-Axis Sun-Tracking Test Module Has Been Developed for Ground and Lear Jet Testing Lens + Radiator + Photovoltaic Receiver Combine for 900 W/kg New SOLAROSA Platform Provides Deployment and Support 2016 Mark O Neill, LLC Slide 37

38 Acknowledgement The Authors Gratefully Acknowledge that the Work Reported in this SPRAT XXIV Presentation Was Funded by the NASA SBIR Program (Phase I and Phase II Contracts) with Mark O Neill, LLC 2016 Mark O Neill, LLC Slide 38

Line-Focus and Point-Focus Space Photovoltaic Concentrators Using Robust Fresnel Lenses, 4-Junction Cells, & Graphene Radiators

Line-Focus and Point-Focus Space Photovoltaic Concentrators Using Robust Fresnel Lenses, 4-Junction Cells, & Graphene Radiators Mark O Neill 1, A.J. McDanal 1, Michael Piszczor 2, Matt Myers 2, Paul Sharps