Infrared Energy to Deep Space

Transcription

1 Infrared Energy to Deep Space The Nighttime Solar Cell R.J. Parise,, Ph.D. Parise Research Tech. Suffield, Connecticut G.F. Jones, Ph.D. Villanova University Villanova, Penn. Workshop: Infrared Radiation, Thermoelectricity and Chaos JMU, June 17, 2015

2 Dedicated to the Great Italian Inventor Leonardo da Vinci April 15, 1452 May 2, 1519 Creative: Architect Scientist Anatomist Geologist Botanist Talented : Painter Sculptor Musician Cartographer Writer Brilliant Inventor, Mathematician, Engineer Leonardo was the ultimate Renaissance man and perhaps the greatest inventor ever.

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5 What is this? Ice in the desert mid-summer 5000 years ago. Alien Intelligence or clever Persians?

6 Perspective: Note man sitting

7 Desert summertime ice 5000 years ago 1. Store winter ice: 2 meter thick walls 2. Evaporative cooling intricate wind/vent system 3. Radiative cooling at night; open canal system 4. Radiation to deep space; opening in roof Other observations: Danger: We lose heat to Deep Space; exposure deaths at night. Frost on windshield in a.m. after 38 o F ambient temps. Why not use Deep Space phenomenon for clean, renewable energy?

8 WHAT S THE PHYSICS HERE? Spectral Properties of Earth s Atmosphere Radiation Heat Loss to Deep Space from Earth s surface (IR Energy)

9 Downgoing Solar Radiation Upgoing Thermal Radiation 70-75% Transmitted 15-38% Transmitted Window Through Atm to Deep Space Window Glass Shut off Radiation Intensity Planck s Law: 2hc E( λ, T ) = 5 λ where : 2 1 hc exp λkt h = Planck' s constant = c = Speed of -34 light J s 8 = m sec λ = wavelength ( m) k = Boltzmann' s constant 23 = J K T = temperature ( K) 1 70

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11 IR Energy to Deep Space

12 The Heat Engine for the NSC?

13 THERMOELECTRIC GENERATOR Standard Operation/Installation of Thermoelectric Generator Rejected heat CJP TEG ELEMENTS Heat In T drives thermal energy Through P-N Junction to Produce electrical energy V = S T where : S = Seebeck Coefficient

14 Device Utility Nighttime Solar Cell 1. Renewable Non-polluting Energy Source 2. Remote Electric Power, 24 hours/day 3. Produces Electrical Energy Day or Night 4. For Large Land Arrays Land More Productive Day and Night 5. Device Can Augment PV (Solar) Panels 6. Very Good for Arid Environments 7. Technology Available Today 8. Solid State Reliability

15 Spectral Window x DEEP T sky = 3.5 K Partial Attenuation of IR Energy in Air δ gap (Thermal Sink) RADIATION Vacuum/Gas Cold Junction Plate N P N P N P Hot Jcn. Hot Junction Plate Thermal Source LOAD k gap Cold Jcn. T h T ambient T c, A CJP Vacuum Cell I Description of Operation 1. TEG Module and Cold Junction Plate (CJP) mounted inside vacuum cell. 2. Vacuum cell sealed by spectral window with high transmissivity in mid-ir range (8 µm to 13 µm band). 3. CJP surface facing window has high emissivity. 4. Vacuum cell mounted with spectral window facing deep space. 5. Thermal energy from surroundings (or low-grade waste thermal heat) enters cell only via Hot Junction Plate. 6. Vacuum isolates thermal energy by conduction heat transfer through TEG elements only and into CJP. 7. High emissivity CJP surface transmits IR thermal energy through spectral window and atmosphere into deep space which is the thermal sink at 3.5 K. 8. Atmosphere is transparent to about 15% - 38% of the IR energy at the expected temperature of operation. 9. Temperature difference across TEGs can be up to 50K, depending on module geometry and thermal conditions. 10. Daytime operation of the cell can use the sun as thermal source to heat CJP; the ambient becomes thermal sink thus reversing the current flow through the Load. 11. The nominal size of a single cell is 6cm x 6cm x 3cm. 12. Cells can be assembled into large arrays. Schematic of Cell Configuration

16 Deep 4K Thermosphere (125km) Mesosphere (85km) Stratosphere (50km) Troposphere (10km) 15% to 38% Earth Surface Energy to Deep Space O 3 ; CO 2 ; Trace 8 µm-13 µm Spectral Window in Atmosphere He H 2 N 2 O 2 Ar T=700K (n) to 2200 (d) P=1.0e-6atm T=180K P=1.0e-5atm T=230K T=270K P=1.2e-3atm T=230K P=1.5e-2atm T=220K P=0.20atm H 2 O; CO 2 ; Trace Ar O 2 N 2 Atmosphere Model ε p =0.96 Cold Junction Plate T=288K P=1atm

17 Previous Model Development for NSC 1. One-dimensional heat flow 2. Steady flow 3. Internal heat generation due to I 2 R losses 4. Internal reflections on CJP with window only 5. Convection heat transfer at external window surface 6. Constant ambient temperature at hot junction 7. Deep space at constant 3.5 K 8. CJP is diffuse, gray-ish surface 9. Active atmospheric bandwidths as required 10. CJP view factor with deep space is unity Previous Research 1. Design/select TEG elements: Number of junctions based on: a. cross-sectional area; b. length. Design constraint: 2 x 2 ZnSe window 2. Develop atmospheric model based on absorption/emission of IR energy gases in 8µm to 13µm spectrum 3. Study various effects/parameters on system: CJP area vs TEG cold plate area; daytime solar heating; low-grade thermal source effect, changing CJP area/design.

18 Deep Space Atmospheric Radiation Model L L L { { { q o,λ,g (T,P,L) q o,λ,g (T,P,L) q o,λ,g (T,P,L) Atmospheric Layers: Different Temps and Pressures DEEP T S =3.5 K COLD JUNCTION PLATE, T C, A W q o,λ,cjp (T) Note: Spectral Window absorption not shown here Cold Junction Plate Energy balance between CJP and Deep Space through Atmosphere Convect fr. Spect Window. Rad. to Conduct. Rad. to Rad. to Radiation to. + CJP fr. + to CJP = CJP Top + CJP Top + Deep Space Window fr. TEGs fr. CO 2 fr. H 2O Less Absorbed Radiation fr. Radiation fr. Radiation + Deep Space + trace comps. + to CJP Top to CJP Top to CJP Top fr. Ozone Neglect back radiation from atmospheric gases: Convect. Rad. to Conduct. Radiation to Radiation fr. fr. Spect. + CJP fr. + to CJP = Deep Space + Deep Space Window Window fr. TEGs Less Absorbed to CJP Top

19 ε W = 12 i= 1 ε F i ( λ T, λ T ) i s i+ 1 s 80 Transmittance (percentage) Wavelength (microns) Twelve-Banded Model for Atmospheric Transmittance at Sea Level 0

20 Nighttime Solar Cell Model Radiation Equation: q c = (1 ρ ) J where J c W is W radiosity Cold Junction Plate. h c τ σt of 4 Sky ε W σt 4 W Energy Balance on Window: w T ( T and amb T W = 3.5K ) = 2ε ε T ( x = 0) = T sky W W 4 W + ( k Energy Equation: q ηa ( A c r P element h + J c σt, known, A N element ε gap W / δ ) = κ( T + ( α σt P gap h 4 sky )( T c + α c T ) N T ) 2 W T c (1) (2) ) (3a) (3b) (4) I out + energy transmitted to deep space energy transmitted by window 1 2 Spectral Window Spectral Window x I 2 out R δ gap DEEP T sky = 3.5 K elements (Thermal Sink) Partial Attenuation of IR Energy in Air L RADIATION h W k gap reflected energy Cold Junction Plate N P N P N P Hot Jcn. Hot Junction Plate Thermal Source LOA D Cold Jcn. Vacuum Cell energy radiated from space and atmosphere T amb T h T ambient T c, A CJP I Five Equations, Five Unknowns (T c, q c, J c, T W, I out )

21 Nighttime Solar Cell Model (continued) where η is " fin" effiecincy of unity, κ is TEG κ = ( λ A p p L p CJP, consider to be pair thermal ) + ( λ A R is TEG electrical resistance: R = ( ρ nln / An ) + ( ρ plp / Ap ) Figure of Merit: Z = Current out: ( α 2 ) 2 2 [( ρ λ ) ( ) ] 1/ + ρ λ 1/ 2 n n p + α n p p n conductance : n L n ) energy transmitted to deep space energy transmitted by window Spectral Window Spectral Window x δ gap DEEP T sky = 3.5 K (Thermal Sink) Partial Attenuation of IR Energy in Air L RADIATION h W k gap reflected energy Cold Junction Plate N P N P N P Hot Jcn. Hot Junction Plate Cold Jcn. Vacuum Cell energy radiated from space and atmosphere T amb T c, A CJP I out ( α p + α n )( Th Tc ) R[ + ] ( T T ) Z h + with = = c Open Circuit Voltage: 1/ 2 Thermal Source LOA D T h T ambient I V oc ( α + )( T T ) = α p n h c

22 Number of TEG Junctions vs. Power Output of the Cell

23 Third Generation Prototype Custom Built TEG Module By this time we knew the device works and many of the naysayers were still scratching their heads.

24 Prototype Parameters TEG MODULE Elements: 0.635mm x 0.635mm x 24.13mm long No. of TEG Junctions: 32 Material: bismuth telluride Standard Ceramic End Face Construction COLD JUNCTION PLATE (CJP) Size: 44.5mm x 44.5mm x 0.5mm Spectral Coating: Stove-black Paint ε = 0.94 Material: Copper WINDOW Size: 5cm x 5cm x 4mm Material: zinc selenide CELL Finned aluminum base: 5.9cm x 5.9cm x 0.6cm Delrin Body: 5.9cm x 5.9cm x 3.5cm Aluminum window frame: 5.9cm x 5.9cm x 0.4cm ELECTRICAL: Two water-tight connections: positive/negative

25 V = S T Long TEG elements: T based on conduction heat transfer TEG Module Used in Prototype

26 Prototype Nighttime Solar Cell in Assembly

27 Prototype Nighttime Solar Cell Located on Roof

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31 Next Generation NSC Use Micro-TEGs

32 3.388mm 3.364mm Simple Micro Generators

33 Current Micro-TEG Thermal Props. Poor Match for NSC. Various cell configurations and Micro- TEG designs will be studied to improve Operation; Ultimate goal is to complement PV cell arrays by producing clean, silent electric power day and night.

34 Future Research 1. Select inexpensive materials for cell construction; build and prove efficacy; 2. Reconfigure Micro-TEG design and assembly to better match NSC requirements; 3. Build and test evacuated or controlled cell internal environment to improve operation, reduce cost, and simplify manufacturing needs; 4. Select/test materials to demonstrate ruggedness and portability of NSC; 5. Research other unique applications for remote usage and silent electric power applications.

35 Summary 1. The NSC uses spectral gap in atmosphere to produce clean, renewable, limitless electric power; 2. Great for remote outposts where a silent, zero-footprint is required; 3. Can be made very portable for easy set-up, breakdown and mobility; 4. Produces electrical energy day and night; 5. Large arrays more effective with nighttime usage; 6. Previous research shows with Low-Grade Thermal Source, 10K temp. increase improves power output 22%; 7. Improved TEG Module output will allow Nighttime Cell to compete with solar photovoltaics; 8. Previous research shows operation in arid locales will be exceptional; 9. Micro-TEG improvements/redesign will reduce overall cell manufacturing costs; 10. One might say almost 40% of the windows are always open in the Greenhouse, how will we keep the plants from freezing? Produce electricity instead.

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