Modeling and simulation of thermoelectric device used as a heat pump and an electric generator under mediterranean climate1

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Modeling and simulation of thermoelectric
device working as a heat pump and an electric
generator under Mediterranean climate
ARTICLE in ENERGY · JULY 2015
Impact Factor: 4.16 · DOI: 10.1016/j.energy.2015.06.090
4 AUTHORS, INCLUDING:
Bourhan Mohammad Tashtoush
Jordan University of Science and Technology
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Available from: Bourhan Mohammad Tashtoush
Retrieved on: 21 July 2015

Modeling and simulation of thermoelectric device working as a heat
pump and an electric generator under Mediterranean climate
Moh'd A. Al-Nimr, Bourhan M. Tashtoush*
, Ahmad A. Jaradat
Mechanical Engineering Department, Jordan University of Science and Technology, Irbid, Jordan
a r t i c l e i n f o
Article history:
Received 16 February 2015
Received in revised form
14 June 2015
Accepted 22 June 2015
Available online xxx
Keywords:
Thermoelectric heat pump
Thermoelectric generator
Dual usage
Evacuated tube
Solar energy
Energy saving
a b s t r a c t
This paper presents a study of a small thermoelectric device used primarily as a heat pump and
secondarily as an electricity generator when space heating and cooling are not required and incident
solar radiation is sufficient. As a power generator, the thermoelectric device is integrated with an
evacuated solar collector to utilize solar power. Performance of the thermoelectric device as a heat pump
and as an electric generator is simulated using MATLAB/SIMULINK. The purpose of this study is to es-
timate the energy savings from using the thermoelectric device in its electricity generation mode. The
potential of energy saving because of this electricity generation mode function, has been examined in
three different cases. These cases represent the operation of the dual mode thermoelectric system in
typical home, school and office buildings in the Mediterranean region. In addition, the effects of different
parameters, such as the solar radiation and ambient conditions, on the device performance were
investigated for both modes as well as parameters related to the device itself. Furthermore, hours of
operation were estimated and the economic feasibility of the device was evaluated. Results of this study
include performance curves of the thermoelectric device in both modes as well as the estimation of the
payback period for Mediterranean regions.
© 2015 Elsevier Ltd. All rights reserved.
1. Introduction
TEGs (thermoelectric generators) are thermoelectric devices,
which generate electric power from any temperature gradient
along its junctions. Thermoelectric devices can also operate to form
temperature gradients if an electric current is applied. This gradient
can be utilized for heating and cooling by controlling the direction
of the current and the positions of the poles.
Thermoelectric devices have various advantages in compare to
other devices used for similar applications [1], namely: (1) Ther-
moelectric generators utilize low-grade thermal energy, which is
cheap and available. (2) Thermoelectric generators are environ-
mentally friendly, since they do not emit pollutants during opera-
tion. (3) Thermoelectric devices have a longer lifetime; because
there are no moving parts in compare to conventional thermal
systems, such as conventional heat pumps.
In addition to all advantages previously mentioned, thermo-
electric heat pumps have a lighter weight, do not contain any fluids,
and their purposes can be changed easily. Therefore, the reliability
of thermoelectric devices are relatively higher [2]. Also, thermo-
electric devices have the advantage over PV (photovoltaic) modules
which need direct solar radiation to operate rather than available
temperature gradients. On the other hand, low efficiency is a major
disadvantage. The efficiency of thermoelectric generators usually
does not exceed 10%. However, rapid advancements in semi-
conductors technologies show great chances to help overcome this
disadvantage.
Thermoelectric devices are based on two principles. The first
one is Peltier Effect, which converts electrical energy to thermal
energy. This implies that a direct current drives heat to flow
through two different junctions. The second principle is Seebeck
Effect, which produces an electric potential when a temperature
gradient across two junctions exists [3].
Using thermoelectric devices as power generators, heaters, or
coolers has been studied by many researchers. The following
literature review has been included to present their findings. Ac-
cording to this review, researchers investigated thermoelectric
devices as power generators or as heat pumps alone; however, to
the best of authors' knowledge, they did not study the utilization of
thermoelectric devices for both modes.
* Corresponding author. Tel.: þ962 2 720 1000.
E-mail address: bourhan@just.edu.jo (B.M. Tashtoush).
Contents lists available at ScienceDirect
Energy
journal homepage: www.elsevier.com/locate/energy
http://dx.doi.org/10.1016/j.energy.2015.06.090
0360-5442/© 2015 Elsevier Ltd. All rights reserved.
Energy xxx (2015) 1e12
Please cite this article in press as: Al-Nimr MA, et al., Modeling and simulation of thermoelectric device working as a heat pump and an electric
generator under Mediterranean climate, Energy (2015), http://dx.doi.org/10.1016/j.energy.2015.06.090

Researchers studied experimental and numerical models of
thermoelectric devices used for air heating and cooling. Better COP
(coefficients of performance) were recorded by Cosnier et al. [4],
Astrain et al. [5], and Riffat et al. [6].
Russel et al. tested the characteristics of a TEC (thermoelectric
cooling device) under different ambient conditions. Effects of
different parameters on the performance of the (TEC) device were
studied, those parameters included: the number of the thermo-
electric cooling elements, geometric factors, and the resistance of
the cold and hot junctions. Their results showed that the system
could run at the minimum power with minimum operating con-
ditions [7]. Yilbas and Sahin [8], investigated the integration of a
refrigerator with thermoelectric generator. The results exhibited
that the position of the thermoelectric generator in the middle of
the evaporator and condenser reduced the overall coefficient of
performance for the system, and the position in the middle of the
ambient and the condenser improved the overall coefficient of
performance of the system. Miranda et al. [9] modeled a thermo-
electric cooling device used for air conditioning. The results showed
the increase of the convection heat transfer coefficient by 10%. He
et al. [10] investigated thermoelectric heat pump considered in
heating and cooling modes. Photovoltaic/thermal system used to
provide electrical power to the thermoelectric heat pump and
thermal power used for domestic water heating. The investiga-
tional results revealed that the coefficient of performance of the
thermoelectric heat pump was greater than 0.45 and the water
temperature of the storage tank was approximately 9 C. Shen et al.
[11] modeled and examined an innovative thermoelectric heat
pump. The results have shown that the coefficient of performance
of the thermoelectric heat pump was close to that in traditional air
conditioner and radiant air conditioner, but its cost is higher. Zhao
et al. [12] investigated the integration of both phase change ma-
terial as heat storing system and thermoelectric cooler. The results
exhibited that the coefficient of performance was in the range of
0.87e1.22 and the phase change material reduced the electricity
consumption by 35.3%.
Zhang et al. [13], Zheng et al. [14], and He et al. [15] designed
thermoelectric systems in which solar collectors were integrated for
double functions: the first was Electricity Generation and the second
was Water Heating. Their results showed that integrating thermo-
electric devices with solar collectors was economically feasible, and
such integration could be used for large-scale applications. These
studies also revealed the relationships between the electrical and
thermal efficiencies with solar radiation, number of thermoelectric
elements, water temperature, and ambient temperature.
Kinsella et al. [16] studied a thermoelectric device to generate
electricity used to charge a battery. Krishna et al. [17] simulated a
thermoelectric generator and a photovoltaic module using MAT-
LAB. Their system was designed to harvest thermal energy rejected
from car engines and reuse it for air heating, air-cooling, lighting,
and charging the battery.
Montecucco and Knox [3], Rezania et al. [18], and Kraemer et al.
[19] modeled and simulated a thermoelectric device to produce
electricity with maximum power output. Both electrical and ther-
mal models were simulated. Their results showed that the simu-
lation results were close to experimental records for the (TEGs).
They also showed that the maximum power generation could be
achieved at various thermal and electrical resistance values.
Lesage et al. [20], Nia et al. [21], and Date et al. [22] designed
thermoelectric generators, which utilized solar energy as a source
for electricity generation. Their results showed the relationship
between the optimum load and the maximum output power. They
also showed that the thermoelectric generator was a promising
technology for power generation from renewable energy sources
rather than fossil fuels.
Martinez et al. [23] presented a thermoelectric generator, which
could be cooled by itself without the need for extra electrical po-
wer. Their results showed that thermoelectric self-cooling systems
could work as temperature controllers.
Francis et al. [24] simulated a refrigeration thermoelectric de-
vice at different working conditions using MATLAB. Their results
showed that the COP was affected by the temperature difference
between the heat sink and the heat source; hence, the COP was
maximized when the temperature difference was minimized.
Maneewan et al. [25] simulated the combination of a thermo-
electric generator with a solar collector installed on a rooftop in
order to reduce an attic heat gain. The proposed system generated
enough electricity to run a fan used to cool the system and
Nomenclature
TH hot side temperature of thermoelectric device, K
TL cold side temperature of thermoelectric device, K
A cross sectional area of thermoelectric module, cm
L length of thermoelectric module, cm
QC cooling capacity of thermoelectric heat pump, W
N number of modules, N
a Seebeck factor for thermoelectric element, V/K
aT total Seebeck factor for the module, V/K
I electrical current, A
R electrical resistance of thermoelectric module, U
PINH input electrical power for heating, W
PINC input electrical power for cooling, W
n number of thermoelectric elements, n
Ta ambient temperature, K
Qh heating capacity for thermoelectric heat pump, W
COPH coefficient of performance for heating, COPH
K thermal conductance of thermoelectric module, W/K
Pout output power from thermoelectric generator, W
QH absorbed heat at hot side of thermoelectric generator,
W
V voltage difference between hot and cold sides of
thermoelectric device, V
PELEC output electrical power from thermoelectric generator,
W
QL absorbed heat at cold side of thermoelectric generator,
W
RL load resistance of thermoelectric generator, U
h thermoelectric generator efficiency, %
Ai surface area of internal tube, m2
Re Reynolds number, Re
V air velocity, m/s
r air density, kg/m3
m dynamic viscosity of the air, N s/m2
hia convection heat transfer coefficient, W/(m2
K)
Nu Nusselt number, Nu
k thermal conductivity of the air, W/(m K)
Qth absorbed heat by thermoelectric generator, W
Aabs absorption area of solar collector, m2
G solar radiation, W/m2
hthermal thermal efficiency of evacuated tube solar collector
M.A. Al-Nimr et al. / Energy xxx (2015) 1e122

minimize the ceiling heat addition. The results showed that the
saved electricity per year was 362-kWh and the payback period of
the system was 4.36-years.
Singh et al. [26] designed a thermoelectric generator combined
with thermos-syphon to produce electric power. The temperature
difference between the hot and the cold junctions was in the range
of (40e60)-C. The results showed that the system could generate
electric power from low temperature difference, especially when it
was used in rural areas.
Tayebia et al. [27] studied and optimized a micro fabricated
thermoelectric generator made from thin film. The results revealed
that this kind of fabrication could give an efficiency competitive
with the traditional one and a fewer intermittent as an energy
source. Hadjistassou et al. [28] proposed a model to develop the
optimal efficiency of thermoelectric generator. The model was valid
for temperature range from 298 K to 623 K. The Results exhibited
that the suggested model had the maximum efficiency of 5.29% at a
temperature difference of 324.6 K. Yusop et al. [29] studied a model
of hybrid thermoelectric generator with solar energy. The shaping
method dependent on the exponential function of reverse dynamic
study was used in order to stabilize the electrical voltage. The re-
sults exhibited that the suggested method would be applied in
order to track the thermoelectric module performance. Attia et al.
[30] designed the low temperature difference of thermoelectric
generator used for small power generation. The investigational
results showed that the typical thermoelectric generator could
produce the highest power. Fisac et al. [31] studied the integration
of thermoelectric modules with photovoltaic modules in order to
cool the back side of the photovoltaic modules and increase their
efficiency. In the mean while, the temperature absorbed by ther-
moelectric device was used to produce electricity. As a result, the
total electrical energy production from the system was increased.
Raghavendran and Asokan [32] simulated an analytical model of
thermoelectric generator with battery that assisted the medicinal
server. The suggested model used the maximum power point
tracker in order to get the peak power from the system. The results
showed that the efficiency of the thermoelectric generator was
improved with the tracking system.
This paper presents modeling and simulation of a thermoelec-
tric device used as a power generator (TEG) and as a heat pump for
cooling and heating. The thermoelectric system will be functional
as a power generator when air conditioning is not needed. Using
thermoelectric devices for those two purposes under Mediterra-
nean climate is very advantageous. This system is used to generate
electricity when there are moderate weather conditions like those
in spring and autumn. In this time of year there is no need for air
conditioning since the temperature is near the thermal comfort
level. In addition, it can operate as a power generator when the
space is unoccupied by residents like in vacations or off days and
after working hours.
2. System overview
2.1. Components and mechanism
Referring to Fig. 1, the system consists of an evacuated tube solar
collector (A), which receives solar radiation and converts it into
thermal energy transferred to the thermoelectric generator (D) to
generate power during its power generation mode. Then, this
generated power is transferred to the battery (E) to be stored.
During the heat-pumping mode, electric power is provided by an
AC source (B), then it is converted into DC and supplied to the
thermoelectric device (D) by a DC source (C). The thermoelectric
device (D) converts electric energy into thermal energy, which is
used to change the air temperature of the space (F) using a fan. This
fan is also used to circulate air around the cold junction in order to
extract rejected heat in the power generation mode.
In addition to the mentioned components, there are two more
components: the first one is the MPPT (maximum power point
tracker), which is a type of a control system that works on calcu-
lating the output current and voltage from the TEG (thermoelectric
generator). This will change the duty cycle of the converter to
maintain the output power to its maximum. The second compo-
nent is the fan controller, which calculates the speed and the cur-
rent of the fan to control the speed.
The studied system contains 18 thermoelectric modules and 18
evacuated tubes.
2.2. The heat pump
When the ambient temperature is low and falls in the range of
(0e19)-C, the thermoelectric system will be functioning as a heat
pump. Under these conditions, the system is used for space heating,
and electric power is drawn from the DC source to create a tem-
perature gradient across the junctions. Heat is then transferred into
the space e which acts as a heat sink-using the fan.
The system will also be functioning as a heat pump when the
ambient temperature is high and falls in the range of (26e35)-C.
Under these conditions, the system is used for space cooling; this
can happen by reversing the direction of the direct current. This
implies that the thermoelectric device will start cooling the air
instead of heating it.
2.3. Electricity generator
The thermoelectric system will be functioning as a power
generator when the ambient temperature is moderate and space
heating or cooling is not necessary. Under these conditions, the
solar thermal collector absorbs solar radiation to heat water. This
water will be circulating to act as a heat source for the (TEG), and it
will be stored in a tank to be used in other domestic applications.
The cold junction's temperature can be controlled by exposing it to
Fig. 1. Schematic drawing of the system. (A) Evacuated Tube Solar Collector. (B) AC
Source. (C) DC Source. (D) Thermoelectric Device. (E) Battery. (F) Space to be
conditioned.
M.A. Al-Nimr et al. / Energy xxx (2015) 1e12 3

outdoor ambient temperature, or by utilizing any other cold
reservoir like geothermal cold-water sources such as water wells.
3. Modeling and simulation
3.1. Heat pump model
A simple model is proposed for the thermoelectric device, which
is valid for all geometries. The heat balance equations are applied
on both the hot and cold sides.
3.1.1. Assumptions
The thermal conductivity (k), electrical conductivity (s), and the
Seebeck factor (a) are constants and temperature independent.
They are found at the average temperature between the hot and
cold junctions.
The model is valid for one or many pairs of legs and several
modules of thermoelectric devices according to reference [7].
The value of the hot side temperature is higher than the ambient
temperature, and the cold side temperature is below the
ambient temperature according to reference [6].
3.1.2. Governing equations
The system as a cooler is described by the following set of
equations:
TH ¼ Ta þ 13 (1)
K ¼
kA
L
(2)
aT ¼ na (3)
TH ¼
L
As
(4)
QC ¼ N

aT ITL À KðTH À TLÞ À 0:5RI2

(5)
PINC ¼ N

aT IðTH À TLÞ þ RI2

(6)
COPC ¼
QC
PINC
(7)
The above equations are valid for one module with one or many
pairs of legs and several thermoelectric modules. Equation (2) is
based on the assumption that the hot side temperature is higher
than the ambient temperature.
The heat balance at the hot or the cold junctions refers to three
main heat sources: (A) Joule Heat. (B) Conduction Heat. (C) Peltier
Heat Pumping. The Joule Heat means that the current flows to
produce a resistance along the thermoelectric module. The Con-
duction Heat occurs when heat is transferred from the hot junction
to the cold junction across the module. The Peltier effect Heat
Pumping is when heat is absorbed by one junction and released
from the other junction.
The performance of the thermoelectric system as a heat pump is
described by the COP (coefficient of performance). The COP is
defined as the fraction of useful thermal heat, which is absorbed or
released to the provided electric work.
To describe the system as a heater, the following set of equations
are used in addition to equations (2)e(4) [34]:
TH ¼ Ta À 3 (8)
QH ¼ N

aT ITH À KðTH À TLÞ þ 0:5RI2

(9)
PINC ¼ N

aT IðTH À TLÞ þ RI2

(10)
COPH ¼
QH
PINC
(11)
Equation (8) is based on the assumption that the cold side
temperature is below the ambient temperature.
3.2. Thermoelectric generator model
3.2.1. Assumptions
The system isrunning under moderateweatherconditions(Spring
and Autumn), or when there are no occupants in the space.
The thermal conductivity (k), electrical conductivity (s), and the
Seebeck factor (a) are constants and temperature independent.
They are found at the average temperature between the hot and
cold junctions.
3.2.2. Governing equations
QH ¼ N

aT ITH þ KðTH À TLÞ À 0:5RI2

(12)
QC ¼ N

aT ITL þ KðTH À TLÞ þ 0:5RI2

(13)
Pout ¼ QH À QL (14)
I ¼
nfðTH À TLÞ
R þ RL
(15)
V ¼ NðnfðTH À TLÞ À IRÞ (16)
Pelectric ¼
NðnfðTH À TLÞÞ2
4R
(17)
h ¼
Pout
QH
(18)
3.3. Evacuated tube solar collector model
A simple thermal analysis is used to describe the output of the
evacuated tube solar collector. The purpose of using the model is to
predict the temperatures of the hot and the cold sides of the
thermoelectric generator. The model is similar to the one found in
reference [33].
Re ¼
rVDi
m
(19)
Nu ¼ 0:3Re0:6
(20)
hia ¼
Nuk
Di
(21)

Fig. 3. Building block diagram of the thermoelectric air cooler heat pump, (Cooling Mode) in MATLAB/SIMULINK.
Fig. 2. Building block diagram of the thermoelectric air heater heat pump, (Heating Mode) in MATLAB/SIMULINK.

Rth ¼
1
hiaAi
(22)
Qth ¼
GAabshth
N
(23)
TL ¼ Ta þ
GAabshth
N
Rth (24)
TH ¼ Ta þ
GAabshth
N
ðRth þ RÞ (25)
3.4. Simulation
3.4.1. Heat pump
Fig. 2 presents a building block diagram of the thermoelectric
heat pump in heating mode. This diagram is simulated using
MATLAB/SIMULINK environment.
The inputs for the heating mode simulation are the hot
side temperature, the ambient temperature, and the elec-
tric current. The outputs of the simulation are the cold side
temperature, the heating capacity, and the coefficient of
performance.
Fig. 3 shows a complete building block diagram of the ther-
moelectric heat pump (cooling mode). This diagram is simulated
using MATLAB/SIMULINK environment.
Inputs for the cooling mode are the ambient temperature, the
cold side temperature, and the electric current. The outputs of the
simulation are the hot side temperature, the cooling capacity, and
the coefficient of performance.
Fig. 4 shows a flow chart designed for the system simulation as a
heat pump (Cooling and Heating modes). Programming of the
simulation is based on this flow chart.
3.4.2. Thermoelectric generator
Fig. 5 shows a complete building block diagram of the ther-
moelectric generator. This diagram is simulated using MATLAB/
SIMULINK environment.
Fig. 4. Flow chart for the heat pump simulation algorithm.

The inputs for the power generation mode are the weather
conditions for Irbid city in Jordan. The outputs of the simulation are
the useful heat absorbed by the thermoelectric device, the tem-
peratures of the hot and the cold sides, the voltage difference, the
electric current, the power, and the efficiency.
Fig. 6 shows a flow chart designed for the system simulation as a
power generator. Programming of the simulation is based on this
flow chart.
3.5. Selected parameters
3.5.1. Thermoelectric module
The physical specifications of the selected thermoelectric
module are shown in Table 1, whereas the electrical and thermal
specifications of the thermoelectric module are shown in Table 2.
3.5.2. Evacuated tube solar collector
Table 3 shows the geometrical specifications of the evacuated
tube solar collector selected for this study.
4. Results and discussion
4.1. Heat pump
4.1.1. Heating mode
Fig. 7 shows the electrical current variation with the electrical
input power. It is noticed that as the electrical current increases the
input power increases and reaches its peak value of 2208 W at the
maximum current value of 10 A. In addition, it is noticed that the
coefficient of performance reaches its maximum value of 3.8 when
the electrical current is low. The coefficient of performance
decreases and reaches its minimum value of 1.26 when the electric
current increases and reaches its maximum value of 10 A.
Fig. 8 shows the relationship between the electric power input
with the heating capacity and the coefficient of performance for
heating mode. It is noticed that when the input power is low, the
coefficient of performance reaches its maximum value. The coeffi-
cient of performance decreases to its minimum value as the elec-
trical power increases to its peak point. Furthermore, it can be
noticed that when the electrical input power to the heat pump
increases, the heating capacity also increases. Accordingly, the
thermoelectric heat pump can operate at the maximum coefficient
of performance with low input power, but the heating capacity is
low and will not be sufficient for the intended purpose.
Fig. 9 shows the relationship between the heating capacity and
input power of the thermoelectric heat pump with the hot side
junction temperature. It is concluded that the hot side temperature
increases when the heating capacity and input electrical power
increase.
4.1.2. Cooling mode
Fig. 10 shows the coefficient of performance as a function of the
input power and the cooling capacity. It is noticed that the coeffi-
cient of performance reaches its maximum value of 2.35 when the
power input is low. The coefficient of performance decreases to its
minimum value at the input power's peak value, and the cooling
capacity increases to its maximum value.
Fig. 11 shows the relationship between the electric current with
coefficient of performance and cooling capacity. When the elec-
trical current is low, the coefficient of performance is high. The
coefficient of performance decreases to its minimum value of 0.38
when the electric current is in its maximum value of 8.5 A. The
cooling capacity also increases to its peak value of 626 W.
Fig. 5. Building block diagram for the thermoelectric generator (TEG) in MATLAB/SIMULINK.

Fig. 6. Flow chart for the power generator simulation algorithm.
Table 1
Physical specifications of the thermoelectric module that have been chosen for this
study, [35].
Physical properties Value Unit
Length 6.27 cm
Width 6.27 cm
Area 39.31 cm2
Number of thermocouples 97 N
Table 2
Electrical and thermal specifications of the thermoelectric module, which has been
chosen for this study, [35].
Property Value Unit
Power 9 W
Load voltage 3.28 V
Internal resistance 1.15 U
Current 2.9 A
Open circuit voltage 6.5 V
Efficiency at 200
C temperature difference 4.5 %
Thermal conductivity 0.018 W/(cm K)
Heat flux 5.52 W/cm2

Fig. 12 shows the relationships between the cold side junction
temperature with input electrical power and cooling capacity. It is
noticed that the needed input power increases when the cold side
temperature increases. This is explained by the increase in the
cooling capacity needed to cool the ambient at relatively high
temperature of the cold side.
4.2. Power generator
Fig. 13 shows the relationship between the cold and hot junc-
tions temperatures and the absorbed heat. It is noticed that the hot
side temperature increases to its maximum value of 433.8 K when
the absorbed heat reaches its peak value of 845.9 W in addition, the
cold side temperature increases by conduction to its maximum
value of 359.8 K.
Table 3
Geometrical specifications of the evacuated tube solar collector, which was selected
for this study, [13].
Geometrical properties Value Unit
Outer glass tube diameter 0.07 M
Inner tube diameter 0.058 M
Length of the tube 1.95 M
Number of tubes 18 N
Number of solar collectors 1 N
Fig. 7. The relationship between the coefficient of performance and the input power
with the electric current.
Fig. 8. The relationship between the coefficient of performance and the heating ca-
pacity with the input power.
Fig. 9. The relationship between the heating capacity and the input power with the
hot side temperature.
Fig. 10. The relationship between the coefficient of performance and the cooling ca-
pacity with the input power.
Fig. 11. The relationship between the coefficient of performance and the cooling ca-
pacity with the electric current.
Fig. 12. The relationship between the input power and the cooling capacity with the
cold side temperature.

The difference in temperature is an important factor since it
plays a significant role in generating the output power from the
thermoelectric generator. When the difference in temperature in-
creases, the electrical current and the power generation increase to
their maximum points of 1.027 A and 21.85 W; respectively at the
maximum temperature difference value of 74 C, as shown in
Fig. 14.
Fig. 15 describes the relationship between the generated electric
power and the total heat absorbed by the thermoelectric generator,
with the efficiency of thermoelectric generator. It can be seen that
the heat absorbed by the thermoelectric generator increases to a
high temperature of the hot side junction, leading to an increase in
the output power and generator efficiency; respectively. The
maximum thermoelectric generator efficiency is 2.58%.
4.3. Energy calculations
Tables 4 and 5 show the energy calculations results for the
system as a heat pump and as a generator under Summer and
Winter conditions; respectively.
It can be seen that the thermoelectric generator contributes in
low percentage of the energy consumption reduction from the heat
pump. This percentage is acceptable since using the device for
electricity generation is a secondary purpose. In addition, the
thermoelectric generator can be fully operated when there is no
need for the heat pump in Autumn and Spring seasons.
As can be seen from these Tables 6e8, the thermoelectric
generator saves 19% of energy consumption from the heat pump in
both heating and cooling mode throughout the year in the typical
school building. Furthermore, the thermoelectric generator saves
8% of energy consumption from the heat pump in both heating and
cooling modes throughout the year in the typical office building.
The thermoelectric generator saves 6% of energy consumption from
the heat pump in both heating and cooling mode throughout the
year in the typical home building.
4.4. Summary of the results
The results of the thermoelectric heat pump (cooling mode)
simulation are shown in Figs. 10e12. The calculated coefficient of
performance for cooling was 0.48 for a current of 7.5 A. Input power
was 1285 W and the cooling capacity was 618.94 W. Similarly, the
results of thermoelectric heat pump (heating mode) are shown
in Figs. 7e9. The calculated coefficient of performance for heating
was 1.46 for a current of 7.5 A. Input power was 1268 W and the
heating capacity was 1860.4 W.
The results of the thermoelectric generator were obtained and
revealed that the saved energy was 9.9% of the energy consumption
from the thermoelectric heat pump (cooling mode), 7.7% of the
energy consumption from the thermoelectric heat pump (heating
mode), and 4.3% of the total energy consumption of the heat pump
for one year.
5. Economic analysis
An economic study is carried out and presented in this paper.
The lifetime of the thermoelectric device is known to be 20-years.
The device includes 18 thermoelectric modules which are con-
nected electrically in series and thermally in parallel. The total area
of the system is 0.0708 m2
. The initial investment includes the costs
Fig. 14. The relationship between the electric current and the temperature different
with the electric power output.
Fig. 15. The relationship between the absorbed heat and the electric power output
with the thermoelectric generator efficiency.
Table 4
Different operating conditions for the heat pump and the thermoelectric generator in summer.
The percentage of operation hours for the heat pump (Cooling Mode) 10% 20% 30% 40% 50%
Energy consumption from the heat pump (kWh) 3.084 6.168 9.252 12.336 15.420
The percentage of day light operation hours (%) 0 10 10, 20 10, 20, 30 10, 20, 30, 40, 50
Energy production by thermoelectric generator (kWh) 0 0.025 0.025, 0.05 0.025, 0.05, 0.075 0.025, 0.050 0.075, 0.100 0.125
The percentage of thermoelectric generator energy production from heat
pump energy consumption (%)
0 4 3, 5.4 2, 4, 6 1.6, 3.2, 4.9, 6.4, 8.1
Fig. 13. The relationship between the hot side temperature and the cold side tem-
perature with the absorbed heat.

of the thermoelectric device with the fan, the maximum point
power tracker and the battery. Maintenance costs are assumed to
be neglected.
The annual energy production was 42 kWh for the maximum
temperature difference between the both sides of 74 C. The annual
energy production became 70 kWh when the maximum temper-
ature difference between the two sides became 94 C. The gener-
ated energy from this device is used to charge a small battery,
which can be used for household applications.
6. Closing summary
Modeling of a small thermoelectric system integrated with an
evacuated tube solar collector used for heating, cooling and elec-
tricity generation is studied and simulated using MATLAB. This study
includes mathematical modeling of the system's behavior, simula-
tion procedures, energy calculations, and an economic analysis.
Performance curves describing the system operating as a heat
pump (heating and cooling) and as an electricity generator are
obtained. The curves show the relationship between many
different variables. In addition, different tables are presented to
show results of the energy calculations and the economic study
(Tables 9 and 10).
The studied system operates as a heat pump (cooling mode)
when the temperature difference between the hot and cold junc-
tions is 28 C. The calculated values of the coefﬁcient of perfor-
mance varied in the range of 0.38e2.35.
Table 7
Comparison of energy consumption from thermoelectric heat pump and energy production by thermoelectric generator in an ofﬁce building in Jordan (Case Study).
Months of the year 1 2 3 4 5 6 7 8 9 10 11 12 Total
Days of the work 24 24 24 24 24 24 24 24 24 24 24 24 264
Operation hours 8 8 0 0 0 8 0 8 0 0 0 8 40
Energy consumption (kWh) 185 213 0 0 0 577 0 137 0 0 0 275 868
Holydays, spring and autumn days 6 6 30 30 30 12 30 6 30 30 30 6 246
After work hours 48 48 0 0 0 48 0 48 0 0 0 48 159
Energy production (kWh) 2 2 6 7 9 6 12 2.8 7 6 5 2 72
Energy saving (%) 1 1 e e e 11 e 2 e e e 1 8
Table 8
Comparison of energy consumption from thermoelectric heat pump and energy production by thermoelectric generator in a typical home building in Jordan (Case Study).
Days of the work 30 30 30 30 30 30 30 30 30 30 30 30 365
Operation hours for heat pump (H C) M 8 8 0 0 0 8 8 8 0 0 0 8 40
Energy consumption from the heat pump (kWh) 231 266 171 231 171 0 0 0 344 125
During work hours 5 6 0 0 0 6 6 6 0 0 0 5 34
Energy production by generator (kWh) 4. 5 6 7 9 5 6 4 7 6 5 4 74
Energy saving by thermoelectric generator (%) 2 2 e e e 8 4 3 e e e 1 6
Table 9
Capital cost of thermoelectric device components, [36].
Item No. of units One unit
price (JOD)
Total
price (JOD)
Thermoelectric modules 18 6 108
Small cooling fan 1 4 4
Electric battery 1 4 4
Fan controller 1 2 2
Maximum power point tracker 1 20 20
Sum e e 138
Table 6
Comparison of energy consumption from thermoelectric heat pump and energy production by thermoelectric generator in a typical school in Jordan (Case Study).
Days of the work 5 15 23 22 22 18 0 11 22 17 21 25 201
Operation hours 6 6 0 0 0 6 0 6 0 0 0 6 30
Energy cons. (kWh) 28.9 99.9 0 0 0 32.5 0 47.1 0 0 0 215 423.7
After work hours 10 45 0 0 0 10 0 44 0 0 0 50 159
Energy prod.(kWh) 4.20 3.99 6.5 7.7 9.5 6.95 12. 6.38 7.5 6.6 5.7 2.1 80.02
Energy saving (%) 15 4 e e e 21 e 14 e e e 1 19
Table 5
Different operating conditions for the heat pump and the thermoelectric generator in winter.
The percentage of operation hours for the heat pump (Heating Mode) 10% 20% 30% 40% 50%
Energy consumption from the heat pump (kWh) 3.04 6.086 9.130 12.173 15.216
The percentage of day light operation hours of the
thermoelectric generator (%)
0 0.0175 0.0175, 0.0341 0.0175, 0.0341, 0.052 0.0175, 0.0341, 0.052,
0.0691, 0.087
Energy production from thermoelectric generator (kWh) 0 0.0175 0.0175, 0.0341 0.0175, 0.0341, 0.052 0.0175, 0.0341, 0.052
0.0691, 0.087
The percentage of thermoelectric generator energy production
from heat pump energy consumption (%)
0 2.9 1.9, 3.8 1.4, 2.9, 4.3 1.2, 2.3, 3.5, 4.6, 5.8

Similarly, the system operated as a heat pump (heating mode)
when temperature difference between the hot and cold junctions is
24 C. The calculated values of the coefficient of performance varied
in the range of 1.26e3.8.
The electricity generation performance of the thermoelectric
device, including the evacuated tube solar collector attached to the
hot side was also investigated. Factors, such as the output power,
the current, and the temperature difference were studied.
The potential of energy saving, as a result of implementing the
electricity generation mode system, has been estimated in three
cases: typical home, typical school and typical office building in the
region. Operating the thermoelectric system in its dual mode will
yield the following average percentages in energy saving over the
year: 19% in typical school, 6% in the typical home and 8% in typical
office building.
In conclusion, this system is satisfactory when used under
Mediterranean weather conditions. The main purpose of the ther-
moelectric system is to be primarily used as a heat pump (heating
and cooling). Using the same system as a power generator is a
secondary purpose. The expected payback period for the system is
14 years.
Acknowledgment
The authors would like to than Mr. Dahdolan, Moh'd-Eslam for
his effort in editing the manuscript.
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Table 10
Results of economic analysis for thermoelectric device.
Interest rate (%) BCR NPV(JOD) PBP (Yr)
Life time of the system
5 10 15 20
5 1.42 À89
À40 9.18
58.5 14
6 1.29 À90
À45 À1.46
40.1 15.17
7 1.17 À92
À49.5 À11
24.1 16.5

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