Thermoelectric Generation by Thermoelectric Generation by Radiative Cooling of the EarthRadiative Cooling of the Earth

Adam VoreAdam VoreStella KimStella Kim

Jung Hye LeeJung Hye LeeJovani TafoyaJovani Tafoya

OverviewOverview

• Need/Purpose

• Theory

• Theoretical vs. Actual Data

• Construction

• Advantages/Disadvantages

• Commercial Viability

• Results/Conclusion

Need/PurposeNeed/Purpose

• Solar Cells need sunlight

• Electricity is needed at night

• Maximizing generated power

TheoryTheoryIntensity

0.00E+00

5.00E+06

1.00E+07

1.50E+07

2.00E+07

2.50E+07

3.00E+07

3.50E+07

0 5 10 15 20 25 30 35

Wavelength

Inte

nsi

ty

Atmospheric Window

•The Atmosphere is clear In the 8-14m range•Most of the radiation of a 300K body is in the “Atmospheric window”

Blackbody curve for a body at 300K

Governing Equation

TheoryTheory

P

•Voltage is generated by temperature difference•Power is generated by heat flow

AK

LQT

nTSV Governing Equations

TheoryTheory

Governing Equations

Generated Electric Power

0

0.01

0.02

0.03

-140 -120 -100 -80 -60 -40 -20 0 20 40

Sky Temperature (oC)

Ele

ctr

ic P

ow

er

Gen

era

ted

(w

att

s) Electric Power (watts)

•Heat Flow Governed by Boltzmann radiation law•Typical values for Thot and Tcold are•Thot =15oC (air temperature)•Tcold=-50oC (sky radiometric temperature)

TheoryTheory

15oC

-60oC

T.E. Generator

Photon path 5oC

•Net Radiation flux out•Heat flow

DataDataOutput vs sky temp and air temp

-5.00

0.00

5.00

10.00

15.00

20.00

7:55:12 PM 8:09:36 PM 8:24:00 PM 8:38:24 PM 8:52:48 PM 9:07:12 PM 9:21:36 PM

Time

Tem

p (

oC

)

0

0.5

1

1.5

2

2.5

3

Ou

tpu

t (m

V)

Sky Temperature

Air Temp

mV output

Voltage output vs sky temperature

0

0.5

1

1.5

2

2.5

3

3.5

-60 -50 -40 -30 -20 -10 0 10 20

Sky temp (oC)

DV (mV)

•Performance was better than expected

•Probably due to Thermoelectric element not covering entire area of emmitter

Measurements taken with the following equipment•1 Apogee instruments infrared thermometer for sky temp•1 Vaisala Weather station for air temp•1 Campbell Scientific CR1000 datalogger for voltage measurements

ConstructionConstruction

• Aluminum reflectors

• Copper Emmiters

• Foam Insulation

• Thermoelectric

• Epoxy

• Dry ice

• Voltage meter

AdvantagesAdvantages

ECONOMICAL/ENVIRONMENTAL

•SUSTAINABLE RESOURCES•LESS MAINTENANCE FEE•ECO-FRIENDLY

DisadvantageDisadvantage

LIMITED AREAS

•LOCATIONS•HUMIDITY•SEASON

Commercial ViabilityCommercial Viability

• A Football field could generate 50kW• For a 1MW powerplant, you’d need 20 football

fields• At a cost of $2/cm2 it would cost $66,000,000

per football field• Costs would go down with a high level of

production• Target cost of $30,000 per football field• Low maintenance costs (cleaning)

Results/ConclusionResults/Conclusion

• A football field could power a house (average daily residential use: )

• Micro thermoelectric generator can reduce the area required

Standard thermoelectric generator mini thermoelectric generator2.5 mm2 – 1.2 mm23.6 mm2 – 38.44 cm2

• High start up costs : $50,000

Solar panel : $ 11,500 wind turbine: minimum $ 2,000/kW

• Inexpensive maintenance

• Cost effective in long-term (Average monthly electricity bill: $95.66)

Pays back after 26 yrs

• Sustainable• Environmentally

friendly

Questions?Questions?

• Please direct all your questions toward Jovani