Enhancement of the output power generated from a hybrid solar thermal system

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org 322
ENHANCEMENT OF THE OUTPUT POWER GENERATED FROM A
HYBRID SOLAR THERMAL SYSTEM
Magdy M. Abdelhameed1
, M. A. Abdelaziz2
, A. Bayoumi3
1
Head of department, Professor, 2
Assistant Professor, Mechanical Engineering Department, Ain Shams University, Cairo,
Egypt
3
Teaching Assistant, Mechanical Engineering Department, The British University in Egypt, Cairo, Egypt
Abstract
This paper investigates the output power and increased the efficiency of a hybrid Photovoltaic/ Thermal (PV/T) modules through
utilizing the heat generated from the surface of panels by one axial tracking of the hybrid PV/Tsystem by means of zenith angle and
decreasing the heat generated from the PV modules by controlling the flow rate of the system. A comparison between theoretical and
experimental work results for fixed and tracking PV/T hybrid system is presented. Comsol software package used to simulate the
electromagnetic waves produced by the sun through solving Maxwell's equations in three dimensions and the sun irradiance is
assumed to be Gaussian distribution across the twelve mourning hours. Beside that an experimental work is presented depending on
the results conjured from the theoretical experience used in Comsol Multiphysics In the second part of the experimental work, one
axial sun-tracking system is designed where the movement of a photo-voltaic module is controlled to follow the Sun’s radiation using
a Data acquisition card (DAQ) unit. Finally an active cooling system is designed and conducted to cool the fixed and tracking
modules at which an absorber system consists of copper pipe welded with aluminium plate is attached underneath the PV modules to
allow water flowing below the modules. In addition to the above an electrical analysis for both systems are presented where I-V, P-V,
power with 12 mourning hour’s and electrical efficiency. Beside that the thermal analysis for the fixed and tracking PV modules and
the piping water are presented where the input, output temperatures, the total energy of heat losses and thermal efficiency are
calculated. As a result, a significant enhancement in the total electrical efficiency is observed with acceptable increase in the output
water temperature.
Keywords: Cooling systems; DAQ; Hybrid; Comsol Multiphysics; Mat lab; Solid work; Lab view.…
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Table 1: Nomenclature
Symbol Description Units
h Planck’s constant 6.626*10−34
J
*s
C The speed of light 3*108
m/sec
P12 The transition of an electron
from E1 to E2
---------------
---------------
𝑔 𝑣(E1) The density of electrons in
the initial state
𝑚−3
𝑔𝑐(𝐸2) The density of available final
states
𝑚−3
KB Boltzmann constant 1.38*
10−23
𝑚2
*
𝑘𝑔 ∗ 𝑠−2
∗
𝐾−1
𝑞 The electron charge 1.6*10-19
C
T Temperature K
Ep The phonon energy Joules
vth The thermal velocity 105
m/sec
S The grid-shadowing factor -----------
r(λ) The reflectance -----------
α(λ) The absorption coefficient 𝑚−1
Г(λ) The incident photon flux ----------
I Current A
V Voltage V
𝐼01 Dark saturation Current A
𝜂 𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐 PV efficiency. %
Pout The maximum power output W
Pin The total optical input power W
Voc Open circuit voltage V
FF Fill Factor. %
𝜌 Fluid Density Kg/m3
T Time Sec
𝑢 Fluid velocity m/sec
P Electrical power out of PV
cell
W
µ Dynamic viscosity Pa*s
Cp Heat capacity at constant
pressure
J/ kg*K
∇T Temperature Gradient K*𝑚−1
𝑞𝑙𝑤 Long wave energy W
E Surface emissivity ----------

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Σ Stefan-Boltzmann constant 5.67𝑒−8
W/𝑚2
*𝐾4
U Overall heat transfer
coefficient
W/𝑚2
*K
A Plate surface area and PV
area
𝑚2
𝑡ℎ Thickness of the plate M
A Pipe surface area 𝑚2
𝐾𝑠𝑖 Silicon thermal conductivity W/𝑚2
*K
𝐾𝐴𝑙 Aluminum thermal
conductivity
W/𝑚2
*K
𝐾𝑃𝑖𝑝𝑒 Pipe thermal conductivity W/𝑚2
*K
ℎ 𝑤 Water thermal conductivity W/𝑚2
*K
ℎ 𝑎𝑖𝑟 Air thermal conductivity W/𝑚2
*K
𝑟𝑖𝑛 Pipe inner radius 𝑚
𝑟𝑜𝑢𝑡 Pipe outer radius 𝑚
L Plate length 𝑚
W Plate width 𝑚
L Total pipe length 𝑚
Q. The rate of heat transfer W
∆ T Temperature difference K
Qheat Heat flux going into PV cell W/𝑚2
qrad Solar Irradiant W/𝑚2
Vmp Maximum power point
voltage
V
Imp Maximum power point
current
A
Ein Solar irradiant energy W
Ewater Thermal Energy extracted by
water
W
mwater Mass of water Kg/s
Tout The output temperature K
Tin The input temperature K
Cpwater Specific heat of water 4.18kJ/kg*K
ηth Thermal efficiency. %
EPV Electrical energy W
ηtotal Total efficiency %
1. INTRODUCTION
Solar energy is becoming one of the primary sources of energy
replacing fossil fuels. Its versatility, abundance and
environmental friendly have made it one of the most
promising renewable sources of energy. Egypt is a primer
location for solar energy production. The Sahara receives
some 2,400 hrs/year of sunshine, about 1.5 times the 1,000
hrs/year than Europe receives. Egypt is one of the Sun Belt
countries receiving between 1970 kWhr/m2
/year in the North
and 2600 kWhr/m2
/year in the South [1].
Bakker et al. [2] analyzed a PV/T panel array where heat was
extracted from the panels and stored underground in a heat
exchanger. In winter, the heat could be extracted from the
ground via a heat pump and used to heat potable water and
support a floor heating system while increasing the electrical
efficiency of the solar panel. Chen et al. [3] developed a
hybrid PV/T pump system using refrigerant fluid R134a as the
heat carrying fluid. The coefficient of performance (COP) of
the heat pump and electrical efficiency of the PV panel was
measured at different condensing fluid flow rates and
temperatures. Teo et al. [4] investigated a tracking PV panel
cooling system, in which the PV panels were cooled by forced
convection, with air being the heat carrying fluid, and resulted
in a 4-5% efficiency increase. Yang et al. [5] developed a
functionally graded material (FGM) is a PV layer, copper
water pipes cast into plastic lumber that was bonded with
thermal paste to the backside of a PV/T panel. Cooling water
was pumped at various flow rates through the cast copper
pipes to decrease the PV/T panel temperature thus increasing
PV/T panel electrical efficiency by up to 2%. This study also
analyzed the thermal efficiency of the closed system design,
and reported that a combined thermal and electrical efficiency
of 71% could be achieved, compared to 53-68% total
efficiency of other PV/T concepts.
2. PROBLEM STATEMENT
As the sun irradiance is varying across the day reaching its
maximum at the normal direction with PV module, the total
output power extracted is changing according to this variation.
To maximize such an output power, one axial sun- tracking
system is suggested. This tracking system provides the
orthogonal between the sun and the PV module across the
morning hours by controlling the modules using the zenith
angle. On the other hand, rising in climate temperature causing
a dramatically increase in the modules temperature. This
increase is from 10 0
C to 15 0
C higher than the rite
temperature which reflects on the PV performance by
decreasing its conversion efficiency. To solve such a problem,
a high heat capacity fluid is used to cool the modules by
passing through pipes in the backside face of the module. This
fluid will extract the heat from the panel causing its
temperature to decrease, in other words its efficiency will
increase. By using hybrid PV/T system another source of
energy is generated due to the thermal effect of the fluid
passing inside the copper pipers.
3. MODELLING AND SIMULATION
Herein, a simulation model for a fixed and tracking hybrid
PV/T system is presented. A backside water pipe is heated by
the influence of the photovoltaic modules results an
enhancement in the total conversion efficiency of the solar
system with increasing the output water temperature.
3.1. Mechanical Model
One axial sun tracking PV modules is presented. The type of
PV modules is a polycrystalline (Si) as shown in Figure (1).
The system has been simulated using Comsol Multiphysics,

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Solid work and Mat lab programs. This hybrid system consists
of four connected PV modules with area 1.0396
m2andthickness is 0.04 m.The effects of cooling system by
passing water in the backside copper pipes of 0.012 m, 0.013
m for inner and outer diameters and 11.6 m length. A copper
pipe material is chosen due to its high thermal conductivity
[6], while water is selected as a cooling fluid for its
availability and high specific heat constant. For the tracking
system, the incident angle is set to be 30ofor winter season
and 15oin summer season for maximum irradiance. The sun
irradiance is assumed to be Gaussian with a peak of 1000
W/m2at noon while AM 1.5G is considered for the fixed
system [7].
Fig 1: A tracking Polycrystalline PV/T hybrid system used in
Comsol
3.2. PV Model
Modelling PV system is done through two main phases, the
first phase is modelling the optical behaviour of the module
and this is done by solving Maxwell’s equations using Comsol
Multiphysics in three dimensions and determines the
absorption coefficient of the material used in modelling the
PV (Silicon). The second phase in modelling device
characteristics by solving passion equation and getting the I-V
characteristics of the device and this is done using Mat lab.
All electromagnetic radiation, including sunlight, is composed
of particles called photons, which carry specific amounts of
energy determined by the spectral properties of their source.
Photons also exhibit a wavelike character with the wavelength,
λ, being related to the photon energy, Eλ, by [8].
Eλ =
hc
λ
(1)
Only photons with sufficient energy to create an electron–hole
pair, those with energy greater than the semiconductor band
gap (EG), will contribute to the energy conversion process.
Thus, the spectral nature of sunlight is an important
consideration in the design of efficient solar cells.
The creation of electron–hole pairs via the absorption of
sunlight is fundamental to the operation of solar cells. The
excitation of an electron directly from the valence band (which
leaves a hole behind) to the conduction band is called
fundamental absorption. Both the total energy and momentum
of all particles involved in the absorption process must be
conserved. Since the photon momentum, Pλ= h/λ, is very
small compared to the range of the crystal momentum, P = h/l,
the photon absorption process must, for practical purposes,
conserve the momentum of the electron. The absorption
coefficient (α) for a given photon energy, hν, is:
α hυ = P12 gv E1 gc(E2)(2)
Assuming that all the valence-band states are full and all the
conduction-band states are empty. Absorption results in
creation of an electron-hole pair since a free electron is excited
to the conduction band leaving a free hole in the valence band
[9].
The conservation of electron momentum of theindirect band
gap semiconductors like Si and Ge, where the valence-band
maximum occurs at a different crystal momentum than the
conduction-band minimum, necessitates that the photon
absorption process involve an additional particle. Phonons, the
particle representation of lattice vibrations in the
semiconductor, are suited to this process because they are low-
energy particles with relatively high momentum. Notice that
light absorption is facilitated by either phonon absorption
(αab ) or phonon emission (αem ). The absorption coefficient,
when there is phonon absorption and emission, are given by:
αab hυ =
hυ−EG +EP
2
e
EP
KB T −1
(3)
αem hυ =
hυ−EG −EP
2
1−e
−
EP
KB T
(4)
Ep =
h vth
λ
(5)
α λ = αab + αem (6)
Since both a phonon and an electron are needed to make the
indirect gap absorption process possible, the absorption
coefficient depends not only on the density of full initial
electron states and empty final electron states but also on the
availability of phonons (both emitted and absorbed) with the
required momentum. Thus, compared to direct transitions, the
absorption coefficient for indirect transitions is relatively
small. As a result, light penetrates more deeply into indirect

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band gap semiconductors than direct band gap
semiconductors.
In practice, measured absorption coefficients or empirical
expressions for the absorption coefficient are used in analysis
and modelling. The rate of creation of electron–hole pairs
(number of electron–hole pairs per cm3 per second) as a
function of position within a solar cell is:
G x = 1 − s 1 − r λ Г λ α(λ)e−αx
dλ(7)
Here, the absorption coefficient has been casted in terms of the
light’s wavelength through the relationshiphv = hc/λ. The
photon flux, Г(λ), is obtained by dividing the incident power
density at each wavelength by the photon energy. Regarding
the semiconductor behaviour of the device equation (8),
repeated here, is a general expression for the current produced
by a solar cell [8].
I = Isc − I01 eq
V
KT
− 1 − I02 eq
V
2KT
− 1 (8)
The short circuit current and dark saturation currents are given
by rather complex expressions that depend on the solar cell
structure, material properties, and the operating conditions. A
full understanding of solar cell operation requires detailed
examination of these terms. However, much can be learned
about solar cell operation by examining the basic form of
equation (8).
From a circuit perspective, it is apparent that a solar cell can
be modelled by an ideal current source (ISC) in parallel with
two diodes – one with an idealist factor of “1” and the other
with an idealist factor of “2”. Note that the direction of the
current source is opposed to the current flow of the diodes –
that is, it serves to forward-bias the diodes.
Solar cell efficiency, η, is defined as the ratio of electrical
power out (at an operating condition of maximum power
output), Pout, divided by total optical power in, Pin, typically
under AM1.5G.AM1.5G stands for Air Mass 1.5 [7], Global
illumination. “Air Mass 1.5” indicates that the sunlight has
been attenuated by passage through the Earth’s atmosphere a
distance equal to 1.5 times the shortest path (when the sun is
directly overhead). “Global” indicates that both direct and
diffuse components of sunlight are included:
ηelectric =
P(out )
P(in)
=
Voc ∗Jsc ∗FF
P(in)
(9)
3.3. Thermal Model
In this study, forced convection does not only occur on the top
surface of the PV panel, but also through the pipe mounted to
the backside of the panel. Therefore, the total convective heat
transfer is a combination of the heat transfer at the surface of
the panel and the heat transfer from the flowing water in the
pipe. The finite element analysis software being used in this
study, Comsol Multiphysics contains an open system laminar
flow and conjugate heat transfer physics package, which is
being used to model the convective heat transfer in the water
pipe on the backside of the PV panel. This package is
appropriate for this study, because of the inhomogeneous
temperature field that is created as water flows from the inlet
to the outlet of the pipe. Comsol numerically solves the fully
compressible continuity and momentum equations, which are
the governing equations for the fluid flow, and are shown
below in equations (10 and 11), shown in [6].
dρ
dt
= ∇ . ρu = 0(10)
ρ
du
dt
+ ρu . ∇u = −∇p + ∇ . μ ∇u + ∇u T
−
23 μ ∇ . u I (11)
The heat equation is also solved, which is shown in equation
(12).
ρCpu . ∇ T = ∇ . K ∇ T (12)
The long wave radiation heat loss can be calculated from
equation (13).
qlw = ε . ς . ( TPV
4
− Tamp
4
)(13)
A numerical model based on Comsol Multiphysics simulation
tool [10] for a hybrid PV/T is introduced as shown in Figure
(2). The silicon PV modules are heated by the electromagnetic
waves produces by the sun through radiation heat transfer.
This heated body (PV modules) transfers its heat to the
aluminium plate and the copper pipe surface (outer and inner)
by conduction. Finally the cooling liquid (water) is heated by
convection where the heat loses and the surrounding radiations
are ignored. The overall heat transfer coefficient is given by
equation (14, 15 and 16) and the rate of heat transfer
calculated by equation (17) for an open thermodynamic
system [6].
1
U A
=
th
KSi A
+
th
KAl A
+
ln(
rin
rout
)2
2 πKPipe L
+
1
hw a
+
1
hair a
(14)
A = l x w (15)
a = 2π r L 16
Q.
= A U ∆ T (17)

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Fig (2): Front and back view for a PV/T system used in
Comsol.
The thermal model modelled in this study is identical to that
modelled by Jones and Underwood [11], although the amount
of energy applied to the PV cell that is converted to heat
energy is calculated using the same method Kerzmann and
Schaefer [12] utilize. The heat energy going into the PV cell is
a function of the PV cell efficiency, ηPV , as shown below in
equation (19) Using this calculated value for the PV cell
efficiency, the amount of solar irradiance, qrad that is
converted to heat energy, Qheat isthen calculated at each time
step from equation (18). The steady state solution is finally
reached as the Comsol solver converges.
Qheat = qrad ( 1 − ηpv
)(18)
The PV cell electrical output efficiency can also be expressed
as a function of PV cell power output, solar irradiance, and the
PV cell surface area as shown in equation (19).
ηPV
=
Vmp Imp
qrad A
(19)
Post processing of the data recorded in the simulations is
required to calculate the thermal efficiency,ηth, of the PV/T
panel [9]. First, the total amount of energy (solar irradiance)
into the cell must be calculated, which is given by equation
(20).
Ein = qrad A(20)
Next, the thermal energy of the extracted by the water per
second must be calculated from equation (21).
Ewater = mwater Cpwater Tout − Tin (21)
The mass of the water passing through the reservoir per
second can be calculated from the density and flow rate of the
water, assuming unit depth of the reservoir. The thermal
efficiency is simply given by equation (22).
ηth
=
Ewater
Ein
(22)
Similarly, the quantity of the total input energy converted to
electrical energy can be approximated from the solution data
by obtaining the average electrical efficiency of the PV/T
panel, a COMSOL derived value taken across the top layer of
the model, and multiplying it by the total energy into the
panel, Ein. This is shown by equation (23).
EPV = ηPV
Ein (23)
The total efficiency of the PV/T panel is then computed from
equation (24).
ηtotal
=
Ewater +EPV
Ein
(24)
Using equations (22 and 24) the thermal and the total
efficiency are simulated.
4. THE PROPOSED TECHNIQUES FOR
ENHANCING THE EFFICIENCY
Two techniques are used to enhance the efficiency of the PV
thermal system. First enhancing the tracking of the hybrid
PV/T system by zenith angle and second decreasing the
temperature of back surface for PV modules.
4.1. Tracking System
A closed loop control system of the hybrid PV thermal system
has been designed to track the zenith angle [13]. Figure (3)
shows the designed control system where a PID controller has
been done. The block diagram of closed loop control contains
DAQ, potentiometer and simple circuit assisted the motor to
rotate shaft for facing the Sun irradiance. Figure (4) shows the
place of the potentiometer used to feedback the angle of PV
thermal system.
The mathematical description of PID control is given by
equation (25):
u t = Kp e t + Ti e(τ
t
0
d+Td
de(t)
d(t)
](25)
4.2. Decreasing the Temperature of Back Surface for
PV Modules
To decrease the temperature of back surface of PV modules
used four temperature sensors (LM 35) are used and placed on
the surface of four PV modules to control solenoid valve by
PWM (Pulse Width Modulator) as shown in Figure (5). Figure
(6) shows the place of electrical valve in the PV thermal
system. Beside that two thermistors are located in inlet and
outlet copper pipes to calculate the heat generated from PV

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modules. The mathematical description of Qheat is given by
equation (26):
Qheat = m.
Cp ∆T(26)
And then calculate the thermal power generated from PV
panels by equation (27):
Pthermal =
Qheat
time(27)
Fig (3): Closed loop block diagram for controlling the motor.
Fig (4): Place of Potentiometer to control the PV thermal system.
5. HYBRID PV/T EXPERIMENTAL SETUP
Figure (7) shows the experimental set-up designed to
investigate how the temperatureaffects the efficiency and
power output of PV panel during operation and takes
advantage of these heat losses. The system mounted on a roof
of a building in a sub-urban area near Cairo. A PV/T system
designed as one axial active tracking [14]. During the
operation, a mechanical tracking system was used to modulate
the power output from solar panel by regulating the position of
the photovoltaic module facing the sun. In other words this
mechanical system makes the zenith angleapproaches to zero
from sun rise to sun set to ensure that the maximum electrical
power is extracted depends on solar irradiance as arrange from

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400 W/m2
to 980 W/m2
.A hybrid system combined between
PV and cooling systems was designed to cool the modules.
The experiment was conducted from 6:00 am to 6:00 pm. A
solar power meter was used to capture the daily global solar
irradiance. Temperature measurements are important in these
experiments and therefore calibrated K-type thermocouples
were utilized. In the experiments, PV current, PV voltage,
water input and output temperatures, PV surface temperatures
and solar irradiance were collected. All the experimental test
rig components that used have been calibrated. Readings were
collected from June 2013 to January 2014.
In order to provide one axial rotation tracker, a closed loop
control system is used. A 5 volt potentiometer is fixed inside
the spindle perpendicularly to detect the angle of rotation. The
potentiometer voltage is acquired to a NI DAQ 6008 and
calibrated into the corresponding angle. Then a PID controller
is chosen to control the system using a previously calculated
reference angle as shown in Figure (8).
In order to maximize the electrical power extracted from the
PV modules, a solenoid valve is used to control the water flow
by acquiring the PV surface temperatures using a 5 volt (LM
35). The temperature sensorsignal (from LM 35) acquired to
the Lab view through the NI DAQ to be calibrated. Pulse
width modulation (PWM) is used to control the opening
duration of the valve by varying the duty cycle of a square
wave generated by Lab view. The frequency of the PWM is
chosen to be 50 Hz as required by the solenoid valve. The Lab
view block diagram shown in Figures (9). The input and
output water temperatures is measured through a 5 volt
thermistor and acquired to the lab view throw the NI DAQ to
be used in calculating the total amount of energy losses from
the PV modules to the water.
Fig (5): Closed loop block diagram for decreasing the temperature of back surface of PV modules
Fig (6): Place of electrical valve used to decrease the temperature of PV surface modules.

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Fig (7): General view of the experimental system used.
Fig (8): Closed loop block diagram for decreasing the temperature of back surface of PV modules.
Fig (9): Closed loop block diagram for decreasing the temperature of back surface of PV modules.

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6. RESULTS AND DISCUSSION
6.1. Tracking Response
Figure (10) shows the response of the tracking control system
where Kp = 3, Ki= 0.63 and Kd = 0.0086. The PID controller
shows a zero steady-state error as response to step input. The
maximum over shot 93 degree and occurred at Tm.o.s= 3.1 sec.
The Kp responsible for increases the responses speed of the
motor, the overshoot of the closed loop system increases [15].
Fig (10): Acquired voltage vs. duration time response for PID
control.
To examine the utility of the PV tracker based on a
potentiometer, the reference angle is plotted verse the actual
angle as shown in Figures (11) and the error is calculated
shown in Figure (12). As expected the error various from 0 to
9% as we go toward extremes either to left or to right. A
minimum error is recorded at noon angle where the efficiency
can be observed from the graph that the error doesn’t exceed
10% which indicated that the used technique is an efficient
one to track the sun across the day.
Fig (11): Rotation angle verses 12 hours mourning.
Fig (12): Absolute error verses 12 hours mourning.
6.2. I-V AND P-V Characteristics Curves for
Theoretical and Experimental Results
The I-V and P-V measured experimentally under difference
irradiance are compared with the corresponding simulation
results as shown Figure (13). This comparison shows an
acceptable response between the experimental and theoretical
results. It can be observed from the graph that the impact of
the Sun irradiance is reflected on the short circuit current with
low effect on the opencircuit voltage. The higher Sun
irradiance is the higher short circuit current. It has to be
mentioned here that the differencebetween the experimental
and simulation results is due to the limited number of
measured data that is taken in the experimentalresults as the
high power resistors are of fixed tendered values.
Fig 13: Comparison between I-V & P-V curves for fixed and
tracking PV/T hybrid system
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
8
9
10
Time (Hr)
Absoluteerror(degree)
0 2 4 6 8 10 12 14 16 18 20
0
2
4
6
V(volt)
I(A)
I-Vcurves for 4 PVmodules
0 2 4 6 8 10 12 14 16 18 20
0
20
40
60
V(volt)
Power(Watt)
P-Vcurves for 4 PVmodules
Simulation Results
Expremintal Results
q rad =450 w/m2
q rad =640 w/m2
q rad =850 w/m2
q rad =714 w/m2
0 2 4 6 8 10 12
50
100
150
200
Time (Hr)
Rotationangle(degree)
Reference angle
Actual Angle

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6.3. Theoretical and Experimental Results for Output
Powers and Related Efficiencies
6.3.1. Without Cooling
Figure (14) provide a comparison between theoretical and
experimental work of fixed and tracking systems without
cooling. This comparison shows an acceptable response
between the experimental and theoretical results. The tracking
system shows an improvement of about 20% in the output
electrical power with respect to the fixed system. This
enhancement in the Pout is reflected on electrical efficiency of
the PV modules as shown in Figure (15).
Fig 14: Comparison between simulation & experimental
results for Pout with 12 hour’s mourning for Fixed & tracking
PV/T system without cooling on31st
December &1st
January.
Fig15: Comparison between simulation & experimental
results for electrical efficiencies with 12 hour’s mourning for
Fixed & tracking PV/T system without cooling
on31st
December &1st
January.
6.3.2. With the Enhanced Hybrid System
experimental work of fixed and tracking systems with cooling
but without controlling on the flow rate inside the copper
pipes. This comparison shows a great accordance between this
case and previous one (without cooling). This comparison
shows an acceptable response between the experimental and
theoretical results. The tracking system shows an
improvement of about 30% in the output electrical power with
respect to the fixed system. This enhancement in the Pout is
reflected on electrical efficiency of the PV modules as shown
in Figure (17). By comparing both with (without using
controlling system) and without cooling systems, it can be
observed that a cooling system records a higher system
enhancement of 7% compared to without cooling case.
Fig16: Comparison between the power outputs with 12 hour’s
morning for fixed and tracking PV-modules without
controlling the flow rate in the pipes cooling on
14th
January &15th
January
Fig 17: Comparison between the electrical efficiencies with
12 hour’s morning for fixed and tracking PV-modules without
14th
January &15th
January.
For thermal analysis, the output temperatures are measured
under both fixed and tracking systems and compared with the
corresponding simulation results as shown in Figure (18). This
comparison shows an acceptable response between the
experimental and theoretical results 15% increase in the output
temperature is observed due to tracking. The thermal power
generated from PV panels calculated from Qheat as shown in
Figure (19). This achievement in thermal power due to the
0 2 4 6 8 10 12
0
10
20
30
40
50
60
70
Time (Hrs)
OutputPower(Watt)
Power Output vs time
Fixed Experimental Results
Tracking Experimental Results
Fixed Simulation Results
Tracking Simulation Results
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
time (Hrs)
ElectricalEfficiency(%)
Electrical Efficency vs time
Simulation Fixed Results
Simulation Tracking Results
Exp. Fixed Results
Exp. Tracking Results
0 2 4 6 8 10 12
0
10
20
30
40
50
60
70
80
time (Hrs)
PowerOutput(Watts)
Simulation Fixed results
Exp. Fixed Results
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
Time (Hrs)
ElectricalEffeciency(%)
Exp Fixed Results
Exp Tracking Resulta

__________________________________________________________________________________________
water passing throws the pipes cooling continuously. It
reached to 11% in case of fixed system while it observed to
18% in tracking system. This improvement causes a 20%
increased in the thermal efficiency so that a 62% thermal
efficiency is detected as shown in Figure (20) for the tracking
system while that of the fixed system is only 48%. Finally the
total efficiency is calculated in Figure (21) as the sum of the
electrical and thermal efficiencies. A 20% enhancement in the
total efficiency is observed, which is considered a big
improvement of PV/T system.
Fig 18: Comparison between the output water temperatures
with 12 hour’s morning for fixed and tracking PV-modules
without controlling the flow rate in the pipes cooling on
14th
January &15th
January.
Fig19: Comparison between the thermal powers generated
from PV panels with 12 hour’s morning for fixed and tracking
PV-modules without controlling the flow rate in the pipes
cooling on 14th
January &15th
January
Fig 20: Comparison between the thermal efficiencies with 12
hour’s morning for fixed and tracking PV-modules without
14th
January &15th
January.
6.3.3 Decreasing The Temperature of Back Surface
for PV Modules Results
experimental work of fixed and tracking systems with cooling
but with controlling on the flow rate inside the copper pipes by
means with using the electrical valve and the sensors on the
surface of PV panels. The controller assists the electrical valve
to open and closed by PWM. The flow rate of water got inside
the copper pipes by different flow. This comparison shows a
great accordance between this case and previous one (without
controller). This comparison shows an acceptable response
between the experimental and theoretical results. The tracking
system shows an improvement of about 30% in the output
electrical power with respect to the fixed system. This
enhancement in the Pout is reflected on electrical efficiency of
the PV modules as shown in Figure (22). By comparing both
with (with controller) and without cooling systems, it can be
observed that a cooling system records a higher system
enhancement of 17% compared in case of without cooling
Fig21: Comparison between simulation & experimental
results for Pout with 12 hour’s mourning for Fixed & tracking
PV/T system with cooling on31st
December &1st
January.
0 2 4 6 8 10 12
10
11
12
13
14
15
16
17
18
time (Hrs)
ThermalPower(Watt)
Thermal Power vs time
Exp. Fixed Results
0 2 4 6 8 10 12
0
10
20
30
40
50
60
70
time (Hrs)
ThermalEfficiency(%)
Thermal Efficiency vs time
Exp Fixed Results
Exp Tracking Results
0 2 4 6 8 10 12
30
35
40
45
50
55
60
65
time (Hrs)
TotalEfficiency(%)
Total Efficiency vs time
Simulation tracking Results
Exp. Fixed Results
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
8
Time (Hrs)
ElectricalEfficiency(%)
Exp Fixed Results

__________________________________________________________________________________________
Fig 22: Comparison between simulation & experimental
results for electrical efficiencies with 12 hour’s mourning for
Fixed & tracking PV/T system with cooling
on31st
December &1st
January.
For thermal analysis, the output temperatures are measured
under both fixed and tracking systems and compared with the
corresponding simulation results as shown in Figure (23). This
comparison shows an acceptable response between the
experimental and theoretical results 30% increased in the
output temperature is observed due to tracking. The thermal
power generated from PV panels calculated from Qheat as
shown in Figure (24). This achievement in thermal power due
to the water passing throws the pipes cooling by PWM. It
reached to 6% in case of fixed system while it observed to 9%
in tracking system. This improvement causes a 30% increase
in the thermal efficiency so that a 78% thermal efficiency is
detected as shown in Figure (25) for the tracking system while
that of the fixed system is only 61%. Finally the total
efficiency is calculated in Figure (26) as the sum of the
electrical and thermal efficiencies. A 30% enhancement in the
total efficiency is observed, this improvement is considered
the main achievement in this work.
Fig 23: Comparison between the output temperatures with 12
hour’s morning for fixed and tracking PV-modules with pipes
cooling on31st
December &1st
January.
Fig 24: Comparison between the thermal powers generated
from PV panels with 12 hour’s morning for fixed and tracking
PV-modules with controlling the flow rate in the pipes cooling
on 14th
January &15th
January.
Fig 25: Comparison between the thermal efficiencies with 12
cooling on 31st
December &1st
January.
Fig 26: Comparison between the total efficiencies with 12
cooling on 31st
December &1st
January.
CONCLUSIONS
The present work introduces a PV/Thermal hybrid system
where the efficiency of the PV modules is calculated without
cooling and with cooling water system in two cases with and
without controlling the flow rate of water inside thermal
system. The following major conclusions are derived from the
discussion of the experimental results:The cooling system
reduce the PV modules temperature up to 10 and 20 °C in
0 2 4 6 8 10 12
0
20
40
60
80
Time (Hrs)
Outputpower(Watt)
Exp Fixed Results
Simulation Tracking Results 0 2 4 6 8 10 12
0
10
20
30
40
50
Time (hrs)
Outputtemprature(C)
Output Temprature vs time
Exp. tracking system
Exp. fixed system
Simulation fixed system
Simulation tracking system
0 2 4 6 8 10 12
0
20
40
60
80
time (Hrs)
ThermalEfficiency(%)
Thermal Efficency vs time
Exp fixed system
Exp tracking system
0 2 4 6 8 10 12
1
2
3
4
5
6
7
8
9
10
11
time (Hrs)
ThermalPower(Watt)
Thermal Power vs time
Simulation Tracking System
Simulation Fixed System
Exp Fixed System
Exp Tracking System
0 2 4 6 8 10 12
0
10
20
30
40
50
60
70
80
time (Hrs)
TotalEfficiency(%)
Exp fixed system
Exp tracking system

__________________________________________________________________________________________
without controlling but with controlling between 10 to
30°Crespectively for fixed and tracking systems compared to
the non-cooling module due to the back pipes cooling. The
thermal power in case of controlling reached to 10 Watt but
without controlling obtained to 18Watt. This is due to the
inability of water inside the copper pipes to suspense and takes
the enough time to decrease the temperature of PV panels. As
the modules temperature increases the output current increases
through limited range In contrast, the output voltage decreases
where the band gab energy for semiconductor decreases with
increases the surface temperature this cause an increase in fill
factor for the module with cooling rather than without cooling
and without controlling for the flow rate.As The fill factor is
inversely proportional to the module surface temperature.The
reduce in module surface temperatures due to cooling system
causing an increase in the module daily output power obtained
to 10% for fixed system while in the tracking system without
controlling reached to 20 % respectively compared to with
controlling obtained to 30% due to back cooling.
REFERENCES
[1] “Solar Thermal Energy.” New and Renewable Energy
Authority.5Aug.2008<http://www.nrea.gov.eg/english1
.html>.
[2] M. Bakker, H. A. Zondag, M. J. Elswijk, K. J.
Strootman, M. J. M. Jong, “Performance and costs of a
roof-sized PV/thermal array combined with a ground
coupled heat pump”, Solar Energy 78 (2005), pp. 331-
339.
[3] H. Chen, Saffa B. Riffat, Yu Fu, “Experimental study
on a hybrid photovoltaic/heat pump system, Applied
Thermal Engineering” 31 (2011), pp. 4132-4138.
[4] H. G. Teo, P. S. Lee, and M. N. A. Hawlader, An active
cooling system forphotovoltaic modules, Applied
Energy 90 (2012) 309-315.
[5] D. J. Yang, Z. F. Yuan, P. H. Lee, and H. M. Yin,
“Simulation and experimental validation of heat
transfer in a novel hybrid solar panel”, International
Journal of Heat and Mass Transfer 55 (2012), pp. 1076-
1082.
[6] The Department of Energy DOE, “FUNDAMENTALS
HANDBOOK - THERMODYNAMICS, HEAT
TRANSFER, AND FLUID FLOW” - Volume 2 of 3”,
Washington, United State of America, June (1992), pp.
11-25.
[7] Reference solar spectral irradiance: Air mass 1.5,
National Renewable Energy Lab.
http://rredc.nrel.gov/solar/spectra/am1.5/. Accessed 29
March 2011.
[8] Antonio Luque, Steven Hegedus, “Handbook of
Photovoltaic and Engineering”, Wiley (2003), pp 62-
87.
[9] O. Lipscombe, “MultiphysicsModeling of Sensors and
Actuators”, Dover Publications, New York, NY,
(2013), pp. 34–81.
[10] Comsol, Version 4.2, http://www.comsol.com.
[11] A.D. Jones and C.P. Underwood, “A Thermal Model
for Photovoltaic Systems”, Solar Energy 70 (2001), pp.
349-359.
[12] Tony Kerzmann and Laura Schaefer, “System
simulation of a linear concentrating photovoltaic system
with an active cooling system”, Renewable Energy 41
(2012), pp. 254-261.
[13] A. Beckman, A. William, “Solar Engineering of
Thermal Processes”, Wiley 4ed, pp. 13-20, (2013).
[14] M.Abderahman, A.Eliwa and Osama.Abdellatif,”
Effect of Aerodynamics Characteristics on Solar Cells”,
Cairo, Egypt , July (2012),pp.21-30.
[15] K. Åström, C. Hang, P. PerssonandW. Ho, “Towards
intelligent PID control”, ResearchTrianglePark, North
Carolina, USA, (1992).
BIOGRAPHIES
Magdy M. Abdelhameed: received his
B.S.c., M.S.c. and PhD degrees from Ain
Shams University, faculty of
Engineering, MechanicalEngineering
Department in 1983, 1989 and 1994
respectively. Currently He is enrolled as
a head of the mechatronicsDepartment atAinShams
University, faculty of Engineering. His research interests lie in
the field of renewable energy especially PVs
Mohamed A. Abdelaziz: received his
B.S.c., degrees from Ain Shams University,
faculty of Engineering, Mechanical
Engineering department in 2001. He then
received his M.S.c and PhD. degrees from
University of Illinois . Chicago, USA,
faculty of Engineering, Mechanical
Engineering Department in 2007. Currently He is enrolled as
an associate professor in the Automotive Engineering
Department atAin Shams University, faculty of
Engineering.His research interests lie in the field of
automotive systems.
Abdelaziz B. Hussien :received the B.Sc.
degree in Mechatronics Engineering,
Mechanical Department from The Higher
Technological Institute, Tenth of Ramadan
City, Egypt, in 2007 and the M.Sc. student
in Mechatronics Engineering Department at
Ain Shams University, Cairo, Egypt.
Currently He is enrolled as an demonstrator in the Mechanical
Engineering Department in the British University in Egypt
(BUE) His research interests lie in the field of renewable
energy especially PVs.

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