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WASTE HEAT RECOVERY BY USING THERMOELECTRIC GENERATOR

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 03, March 2019, pp. 188–195, Article ID: IJMET_10_03_019
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
Scopus Indexed
WASTE HEAT RECOVERY BY USING
THERMOELECTRIC GENERATOR
Basel Al Ghabet*, Raymond Kwesi Nutor, Xiaozhen Fan,
Sensheng Ren, Yunzhang Fang*
Physics Department, Zhejiang Normal University, Jinhua, China.
*Corresponding Author
ABSTRACT
This paper explains how to convert the lost energy through exhaust system in
internal combustion engines “ICE” to electric energy by using thermoelectric
generators "TEG" with the benefit of the equipment’s which are already existed in
most of the internal combustion engines such as water pump, heat exchanger, and
exhaust system. The miniature cooler system which is designed in the laboratory to
execute the experiment is similar to combustion engines water coolant system to keep
the cold side in “TEGs” fixed on ambient temperature. The heat source was applied
on the hot side to “TEGs” is came from small candles where the “TEGs” consist of
“Bismuth Telluride” material as N-P stripes attached thermally in parallel and
electrically in series where it inserted between two porcelain layers. The electric
current generated from “TEGs” is direct current “DC” the experiment showed the
value of electrical current was proportional to the temperature difference between
"TEGs" sides.
Key words: TEG; Waste heat recovery; ICE
Cite this Article: Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng
Ren, Yunzhang Fang, Waste Heat Recovery by using Thermoelectric Generator,
International Journal of Mechanical Engineering and Technology 10(3), 2019, pp.
188–195.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3
1. INTRODUCTION
Since 1970, conveyances, specifically the ignition of gas and diesel in vehicles, have acquired
expanding consideration as a source of air contamination at both neighbourhood and
worldwide scales. More than 95% of mechanized transport relies upon oil and records for
almost half of world utilization of oil (Woodcock et al., 2007). For the measure of auto use, in
the OECD (Economic Cooperation and Development) nations [1]. For these reasons and
others, the energy scientists have concentrated on their researchers to solving these problems
by using clean energy and developing internal combustion engines to reduce the emission of
harmful gases. For these reasons and others, the energy scientists have concentrated in their
researchers to solving these problems by using clean energy and developing internal
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Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang
combustion engines to reduce the emission of harmful gases. One of these methods is to use
the waste heat in internal combustion engines to generating electricity. Waste warmth through
fumes (30% as a motor cooling framework and 30 to 40% as nature through fumes gas).
Fumes gases quickly leaving the motor can have temperatures as high as 842-1112°F [450600°C]. Therefore, these gases have high heat content, diverting as fumes discharge.
Accomplishments can be made to outline more vitality proficient reverberator motor with
better heat exchange and lower fumes temperatures; notwithstanding, the laws of
thermodynamics put a lower confine on the temperature of fumes gases Figure (1)
demonstrate add up to vitality circulations from the inward burning motor. [2].
Figure 1 Total energy distributions from the internal combustion engine
2. THE PRINCIPLE OF “TEG” MODULES
Thermoelectric is a device depend on Seebeck effect principle to work wherein 1821 the
German physicist Thomas Johann Seebeck found that when two segments of various
electrically primary materials were isolated along their length yet merged by two "legs" at
their closures, an attractive field created around the legs, gave that a temperature division
existed between the two crossings. He distributed his acuities the next year, and the wonder
came to be known as the Seebeck impact. Be that as it may, Seebeck did not spot the reason
for the attractive field. This attractive field comes about because of equivalent however
inverse electric streams in the two metal-strip legs. These streams are caused by an electric
potential distinction over the intersections instigated by heat contrasts between the materials.
On the off chance that one intersection is open however the temperature differential is kept
up, current never again streams in the legs yet a voltage can be predictable over the open
circuit. This created voltage (V) is the Seebeck voltage and is identified with the distinction in
temperature (ΔT) between the heated intersection and the open intersection by a
proportionality factor (α) called the Seebeck coefficient, or V = αΔT. The inducement for α is
subject to the sorts of material at the intersection. While there is a Seebeck impact in
intersections between various metals, the impact is little. A significantly bigger Seebeck
impact is accomplished by utilization of p-n intersections between p-sort and n-type
semiconductor materials [3]. The figure (2) demonstrates p-sort and n-type semiconductor
legs between a heat source and a heat sink with an electrical power heap of protection RL
associated over the low-temperature closes. A practical thermoelectric gadget can be
comprised of numerous p-sort and n-type semiconductor legs associated electrically in
arrangement and thermally in parallel between a typical heat source and a heat sink
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Waste Heat Recovery by using Thermoelectric Generator
Figure 2 N-type and P-type semiconductor legs between the heat sink and a heat source
3. TEG PROFICIENCY AND FIGURE OF MERIT
Figure (3) represents a thermoelectric circuit (or couple) comprising of two distinct
homogeneous materials A and B, their intersections kept up at hot intersection temperature Th
and cold intersection temperature Tc (Th > Tc), and the terminals 1 and 2 of the circuit are
associated with an outside load RL. The heat proficiency, ηg, of the circuit, appeared in figure
(3) can be considered as
(1)
Where P is the electrical power which conveyed to the outer load RL and qh is the heat
input required to keep up the hot intersection temperature at Th.
Figure 3 Thermoelectric circuit
The electrical power, , is defined as
(2)
In equation (2) is the present coursing through the circuit and is characterized as the
proportion of emf created over the circuit to the cumulative shield of the circuit.
(3)
where α is the combined Seebeck coefficient of the materials A and B, ΔT is the
temperature contrast between the hot and cool intersections and R is the collection electrical
protection of the materials A and B. The heat contribution at the hot intersection, Th, is given
by
(4)
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Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang
Where is the combined Heat conductance of the materials A and B. The terms (κΔT)
and (- 1/2 I^2 R) in condition (4) result from the two irreversible impacts of Heat exchange
because of Heat conduction and Joule heating. While the term (αT_h) is because of the
reversible Peltier impact. Combining equalities (2), (3), (4), and
lead to:
(
)(
) (
(5)
)
For a fixed , , and , the
can be improved when the term (Rκα2 ) in the
denominator of condition (5) is limited. This gathering of properties, called the thermoelectric
figure of merit (Z), is characterized as
(6)
Where:
(̅
(̅
(̅
̅ )
̅ )
̅ )
Where
is the quantity of (series associated) couples in the gadget or generator, ̅ and
̅ are the Seebeck coefficients of the n and p write material arrived at the midpoint of over
the temperature run to . ̅ And ̅ are the electrical resistivity and ̅ and ̅ are the heat
conductivities averaged similarly. is the aspect ratio of the legs and assumed uniform over
the device or generator.[4]
4. DESCRIPTION OF EXPERIMENT
The proposed system in the laboratory was four thermoelectric modules attached as parallel in
thermally way and electrically in series way generate electrical power, where each module has
specifications shown in the table (1).
The heat source was candles put under aluminium heat sink which it touches TEGs in hot
side and transfer the heat by conduction process, while the cold side of TEGs is connected
with an aluminium plate to dissipating the heat through water flow inside it. The water was
pumped by using a small water pump located between small water tank and small heat
exchanger, where the purpose of heat exchanger is scattering the heat immersed from cold
way of TEGs and keep the water temperature equal to ambient temperature, therefore the
water is flowing from water tank to heat exchanger to arrive aluminum plate have ambient
temperature and come back to water tank in through closed circuit as shown in 3D drawing in
figure (4).
Table 1 Specifications of TEG module
Dimensions
Lead Specifications
Inner resistance
Temperature variance
Working current
Rated voltage
Cooling control
Assemblage pressure
N-P material type
40 * 40 * 3.7mm component pairs 127
Lead length 300 ± 5mm RV standard lead 5mm single tin
2.0 ~ 2.2Ω (ambient temperature 23 ± 1 ℃, 1kHZ Ac test)
△ Tmax (Qc = 0) 62 ℃ above.
Imax = 6
DC12V (Vmax: 15.5V)
Qcmax 60W
85N / cm2
Bismuth Telluride
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Waste Heat Recovery by using Thermoelectric Generator
Figure 4 3D drawing of an experiment
5. PRACTICAL EXPERIMENT AND RESULTS
The figure (5) shows the practical experiment implementation with all equipment used.
Figure 5 Practical experiment implementation
The experiment shows that when the difference in temperature between "TEGs" both
sides increase the electrical power output from "TEGs" increase as shown in tables (2) which
illustrates the measurements are taken and results.
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Table 2 The measurements are taken and results
Cold side
temperature(°c)
21.5
21.5
21.5
21.5
21.5
21.5
21.5
21.5
21.5
21.5
Hot side
temperature(°c)
24.3
30
40
50
60
70
80
90
100
110
Temperature
variance(°c)
2.8
8.5
18.5
28.5
38.5
48.5
58.5
68.5
78.5
88.5
Output (
V)
0.28
2
3.63
5.31
6.79
8.06
9.66
12
12.4
13.1
Output
(A)
0.05
0.12
0.24
0.38
0.48
0.6
0.69
0.77
0.93
0.97
Output
(W)
0.014
0.24
0.8712
2.0178
3.2592
4.836
6.6654
9.24
11.532
12.707
Figure 6 "TEG" output(V, A, W) vs temperature difference
The figure (6) shows the changing of “TEGs” output voltage, current, and power with the
temperature difference respectively.
6. APPLYING “TEG” SYSTEM ON INTERNAL COMBUSTION
ENGINES “ICE”
A concept of power generation system by using thermoelectric generators which are designed
for waste heat recovery in combustion engines based on the high temperature of rejected
gases from the combustion chambers which flow inside a duct connected with the exhaust
pipe to allow gases heat the internal sides of the duct while the TEGs based on external sides,
the hot side of TEGs will absorbing heat from duct surface by conduction thermal process
while the other side of TEGs will dissipating the heat through water flow inside aluminum
plates fixed on the TEGs cold side by conduction thermal process too. The water which
reasonable about absorbing the heat from cold side of TEGs came from the coolant
combustion system existed in the most of engines by adding water circuit with small pipes
diameter connected with the heat exchanger exit pipe and water pump inlet pipe where it
enters the aluminum plates cold and exit hot after absorbs the heat from TEGs to enter the
engine heat exchanger through water pump to cold back in closed circuit as shown in figure
(7) while the figure (8) shows the water coolant connections of “TEG” system.
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Waste Heat Recovery by using Thermoelectric Generator
Figure 7 Fixing "TEG" system with "ICE" exhaust pipe
Figure 8 Water coolant connections of “TEG” system
7. CONCLUSIONS
This research illustrated one of the useful methods to benefit from waste heat in combustion
engines and generate electric current by using thermoelectric generators with equipment exist
already in most of the combustion engines, the main benefit of this system is reducing the
fuels used in combustion engines which are leading to reduce the released emissions gases
from engines and environmental conservation.
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Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang
ACKNOWLEDGEMENTS
This work was held by the Pioneering group of the Zhejiang Solid State Photo-electronic
Plans Laboratory, Project 973 of the National Key Basic Research Program
(No.2012CB825705) of China.
REFERENCES
[1]
LU JIE, Professor Lars -Gunnar Franzén, Environmental Effects of Vehicle Exhausts
Global and Local Effects – A Comparison between Gasoline and Diesel, Halmstad
University, Halmstad 2011
[2]
J. S. Jadhao, D. G. Thombare. Review of Exhaust Gas Heat Recovery for I.C. Engine.
International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue
12, June 2013, ISSN: 2277-3754, Automobile Engineering Department, R.I.T., Sakharale,
Dist. Sangali, (MS).
[3]
https://www.britannica.com/technology/thermoelectric-power-generator#ref48989.
[4]
Madhav A Karri, Wallace H. Coulter, Thermoelectric power generation system
optimization studies a dissertation, NY 13699 – 5725, department of mechanical and
aeronautical engineering School of Engineering Clarkson University Potsdam.
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