generating thermo-electricity using graphit and aluminum module

Aluminum – Graphite Aluminum – Graphite Thermo-electric Thermo-electric

GeneratorsGeneratorsCharith S Suriyakula

Faculty of Applied SciencesRajarata University of Sri Lanka

Simple theorySimple technologyLow cost Robust

For what.....?For what.....?• Fossil fuel is a limited resource of Earth. Fossil

fuels are non-renewable and is a finite resource.• To meet the power demand of the world, people

have to discover renewable energy sources.• Using fossil fuel is damaging the environment and

also it is expensive

2012 world electricity generation pie chart, from BP Statistical Review of World Energy 2013

Renewable energy Renewable energy sourcessources• Main source is sunlight. Also known as Solar

energyo Can directly use to light, heat homes and other buildings.o Can be used to generate electricityo Hot water heating

• Wind energy is captured by wind turbines to generate electricity

• Hydro power is used to rotate turbines and generate electricity

• Some alternative energy generation methodo Geo-thermal energyo Thermo-electricity

What we need……?What we need……?Heat energy from any source………Heat energy from any source………

• Mechanical engines, computers

• Stoves, lamps• Sun light • Radio active elements…….

Heat Heat Electricity ? Electricity ?• Seebeck effect is the

phenomenon of inducing electricity from heat

• It was first discovered by Thomas Seebeck in 1821

• Modern technology use semiconductor materials to design TEG devices

• To design and develop a low-cost and low-tech thermo-electric generator module.

Glass slidesCopper wires

plastic

wood

aluminum

adhesives paper

Seebeck coefficients of some common Seebeck coefficients of some common metalsmetals

Metal / Alloy Seebeck Coefficient (µV/K) compared to

Platinum

Semiconductor Seebeck Coefficient (µV/K)

compared to Platinum

Antimony 47 Se 900Nichrome 25 Te 500Cadmium 7.5 Si 440Gold 6.5 Ge 300Silver 6.5 n-type Bi2Te3 -230Copper 6.5 p-type Sb2te3 185Lead 4.0 PbTe -180Aluminum 3.5 Pb06Ge39Se58 1670Carbon 3.0 Pb15Ge37Se58 -1990Mercury 0.6 PbBi4Te7 -53Platinum 0 SnSb4Te7 25Sodium -2.0 SnBi4Te7 120Bismuth -72 SnBi2Sb2Te7 151

Metal / Alloy Seebeck Coefficient (µV/K) compared to

Platinum

Semiconductor Seebeck Coefficient (µV/K)

compared to Platinum

Antimony 47 Se 900Nichrome 25 Te 500Cadmium 7.5 Si 440Gold 6.5 Ge 300Silver 6.5 n-type Bi2Te3 -230Copper 6.5 p-type Sb2te3 185Lead 4.0 PbTe -180Aluminum 3.5 Pb06Ge39Se58 1670Carbon 3.0 Pb15Ge37Se58 -1990Mercury 0.6 PbBi4Te7 -53Platinum 0 SnSb4Te7 25Sodium -2.0 SnBi4Te7 120Bismuth -72 SnBi2Sb2Te7 151

• The following factors were considered when designing

o Minimized Heat conductivity from “hot” junction to “cold” junction.

o Maximized temperature difference between “hot” and “cold” junctions

o The contact points of two materials needs to be clearly specified.

o More couples = more power

• More couples in a single glass slide.• Still the contact points were not clearly

visible.

• The aluminum and graphite strips are connected using “L” shaped contact area.

ResultsResults

DiscussionDiscussion Strip width comparison

Cell #

Aluminum Graphite Number of junctions

Hot Junction Temp. (0C)

Cold Junction Temp. (0C)

Room Temp. (0C)

Generated voltage (mV)

Total resistance (kΩ)

Width (cm)

Height (cm)

Width (cm)

Height (cm)

05 0.5 3 0.5 3 4 37 22 29 0.24 45.6 0.5 3 0.5 3 4 45 24 29 0.52 50.4 0.5 3 0.5 3 4 54 26 29 0.78 55.2 0.5 3 0.5 3 4 67 28 29 1.27 60.113 1.0 3 1.0 3 4 43 23 28 0.26 39.7 1.0 3 1.0 3 4 54 27 28 0.58 47.6 1.0 3 1.0 3 4 98 42 28 2.1 48.1

Cell #

Aluminum Graphite Number of junctions

Hot Junction Temp. (0C)

Cold Junction Temp. (0C)

Room Temp. (0C)

Generated voltage (mV)

Total resistance (kΩ)

Width (cm)

Height (cm)

Width (cm)

Height (cm)

13 1.0 3 1.0 3 4 43 23 28 0.26 39.7

1.0 3 1.0 3 4 54 27 28 0.58 47.6

1.0 3 1.0 3 4 98 42 28 2.1 48.1

15 1.0 2 1.0 2 4 82 38 28 2.01 21.6

1.0 2 1.0 2 4 90 39 28 2.1 54.8

1.0 2 1.0 2 4 103 46 28 2.52 62.9

1.0 2 1.0 2 4 114 51 28 3.0 92.8

Strip height comparison

• Generated per couple voltage increases with the temperature difference between two junctions.

• Theoretically this is a linear relationship.

• Some reasons for the variation with the practical grapho Unevenly distributed graphite powdero Contact between the tow materials

• Temperature difference between the ‘hot’ and ‘cold’ junctions play an important role in generating a higher voltage.

Future developmentsFuture developments• Introducing a proper cooling mechanism for the

‘cold’ junction.

• Experimenting on different materials to make the design more portable and to minimize the heat conductivity between the two junctions.

• Making the module more durable.

AcknowledgementAcknowledgement• Dr. Deepal Subasinghe of Institute of

Fundamental Studies, Kandy for the opportunity given to conduct the project.

• Senior colleagues of Department of Earth Sciences, Institute of Fundamental Studies, Kandy for the continuous support and guidance given throughout the project.

• Dr. T. M. W. J. Bandara of Faculty of Applied Sciences, Rajarata University of Sri Lanka for the constant advice given to make this project a success.

ReferencesReferences• 1. Van Herwaarden, A. W., & Sarro, P. M. (1986). Thermal sensors based on

the Seebeck effect. Sensors and Actuators, 10(3), 321-346.• 2. Harman, T. C., Cahn, J. H., & Logan, M. J. (1959). Measurement of thermal

conductivity by utilization of the Peltier effect. Journal of Applied Physics, 30(9), 1351-1359.

• 3. Iue.tuwien.ac.at. 2013. 3.5.12 Seebeck Coefficient. [online] Available at: http://www.iue.tuwien.ac.at/phd/mwagner/node47.html [Accessed: 20 Sep 2013].

• 4. Douglas-self.com. 2013. Thermo-Electric Generators. [online] Available at: http://www.douglas-self.com/MUSEUM/POWER/thermoelectric/thermoelectric.htm [Accessed: 20 Sep 2013].

• 5. Thermoelectrics.caltech.edu. 2013. History of Thermoelectrics. [online] Available at: http://www.thermoelectrics.caltech.edu/thermoelectrics/history.html [Accessed: 20 Sep 2013].

• 6. Kasap, S. (2001). Thermoelectric effects in metals: thermocouples. Canada: Department of Electrical Engineering University of Saskatchewan.