Performance analysis of partially covered photovoltaic thermal (pvt) water collector

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
_______________________________________________________________________________________
Volume: 05 Issue: 01 | Jan-2016, Available @ http://www.ijret.org 15
PERFORMANCE ANALYSIS OF PARTIALLY COVERED
PHOTOVOLTAIC THERMAL (PVT) WATER COLLECTOR
Pratish Rawat1
, K.Sudhakar2
1
Assistant Professor, Mechanical Department, Poornima University, Jaipur, Rajasthan, India
2
Assistant Professor, Energy Centre, Maulana Azad National Institute of Technology Bhopal, India
Email: pratishrawat@gmail.com (Corresponding Author)
Abstract
In this paper the photovoltaic thermal (PVT) water collector partially covered by glass and its energy and exergy analysis were
carried out. The various parameters were computed such as thermal efficiency, electrical efficiency, exergy efficiency etc on daily
basis for Meteorological conditions of Bhopal, India in the month of May. It is found that the maximum temperature of hot water
from PVT system on particular day was found to be 47.5 0C with mass flow rate of 0.0025 kg/sec. The thermal efficiency,
electrical efficiency and energy saving efficiency of the system were found to be exceeding 67%, 9% and 67% respectively. The
use of PVT system, not only reduce the electrical load from conventional energy sources but also produces two form of energy
from single system i.e. electricity and thermal.
Key Words: Energy, Exergy, Solar PVT Collector, PVT System, Solar Energy, Performance Analysis
--------------------------------------------------------------------***----------------------------------------------------------------------
1. INTRODUCTION
A huge amount of research on solar PV-thermal hybrid
collectors has been carried out over the past three decades.
A photovoltaic-thermal (PVT) system is developed by
combining solar photovoltaic and solar thermal system. The
PVT system is an integrated system which can produce both
electricity and heat at the same time. A hybrid photovoltaic
thermal (PVT) solar energy system consists of a PV panel at
the back of which a heat exchanger is attached. The PVT
system refers to a system that extracts heat from the panel
by using heat transfer fluid, usually water or air and
sometimes both. There are many reasons which motivate the
researchers to develop various models and designs of the
PVT system. One of the main reasons is that PVT system
can provide higher efficiency than individual PV and
thermal collector system. The integration of two systems to
one not only increases the efficiency of overall system but
also reduces the payback period. Solar PVT collectors can
be classified as:
1. PVT liquid collector
2. PVT air collector
3. PVT Liquid and air collector
4. PVT concentrator (CPVT)
There are various approaches in PVT system designing. The
solar PVT design parameters are based on type of working
fluid, thermal and electrical efficiency, solar radiation and
working temperature. The solar PVT water collector
system consists of conductive-metal pipes or plates attached
to the back of a PV module which acts as an absorber,
absorbs heat from back of module and transfer it to
circulating fluid. In this arrangement, water is flowed
through these pipes with the help of pump. In solar PV
system, high incident solar radiation on solar PV panel give
high electrical output but at the same time it also increase
the temperature of the solar cells and that results in
reduction in the efficiency of the panel. At standard
temperature and pressure (STP) conditions and depending
on type of material of solar cell, the electrical conversion
efficiency of commercially available solar panel is in the
range of 6–15%. It has been found that with every increase
of 1 0
C in temperature of solar PV panel, there is reduction
of the efficiency by 0.5%.
1.1 Application of solar PVT system
1.2 Advantages of PV/T system
1. Maximizes yield from sun's energy where roof space is
restricted
2. Cooling circuit improves efficiency of solar PV cells
3. Cost of manufacturing and installation reduced
4. Low maintenance
Domestic/
Industrial
water
heating
Hybrid
solar
still
Space
Heating
Space
Heating
Solar
Dryer
Solar
Green
House
Solar PVT
Collector
PVT water
collector
PVT air
collector

_______________________________________________________________________________________
2. METHODOLOGY
2.1 Experiment Methodology
In the construction of solar PV/T system 37W
polycrystalline silicon solar panel is used. A combination of
copper sheet and tubes is attached at back side of panel
which act as absorber. Water is circulated as coolant in the
pipes with the help of pump. A transparent glass cover is
used which partially cover the solar PV panel. The
experiments were carried out at M.A.N.I.T. Bhopal (latitude
of 23.16ºN; longitude of 77.24ºE) India. Various parameters
are measured during the experiment such as Solar intensity,
wind velocity, ambient temperatures, relative humidity,
open circuit voltage, short circuit current, maximum power,
front side and back side temperature of module, fill factor,
etc. The parameters were measured in every one hour from
10.00 a.m. in the morning to 5.00 p.m. in the evening.
Table 2.1: Meteorological Conditions
Location Bhopal, Madhya Pradesh, India
Meteorological
Conditions
Latitude of 23.16ºN;
Longitude of 77.24ºE
Month May 2014
Time 10.00 a.m. to 5.00 p.m.
Table 2.2: Technical specification of PV/T system
1
Solar PV module
type
Polycrystalline
2 Maximum power 37 W
3
Voltage at max.
power (Vmp)
17 V
4
Current at max.
power (Imp)
2.18 A
5
Short circuit
current (Isc)
2.30 A
6
Open Circuit
Voltage (Voc)
21 V
7 Module area 0.3216 sq. m.
8 Absorber
Copper sheet 0.5 mm thick and
copper tubes 12 mm diameter
9 Fluid Water
10
Submersible
Pump
AC-220V, 50Hz, 18W,
Maximum lifting height = 1.65
m.
Table 2.3 Instruments Used in experiment
S.No. Instrument Accuracy Range Parameter
Measured
1 Solar
Module
Analyser
+/- 1% 0-10
V
0.01-
10A
Voc, Isc, Vm,
Im, Pm,
Efficiency,
Fill Factor
2 Solar Power
Meter
+/- 5% 0-
1999
W/m2
Solar
Irradiance
3 Humidity/
Temperature
meter
0.1%
R.H.
+/- 0.8
0
C
R.H.
– 0 –
80%
& 0-
50 0
C
Ambient
Temperature,
Humidity
4 IR
Thermometer
+/- 2 o
C -18 to
400
o
C
Surface
Temperature
5 Water proof
digital
thermometer
+/- 1 0
C -50 to
300
0C
Inlet and
outlet water
temperature
6 Hot wire
Anemometer
+/- 0.1
m/s
0.2 –
20
m/s
Wind
velocity
2.2 Performance Evaluation
Photo electric conversion efficiency is the ratio of useful
electrical output of the system to the incident solar
irradiation on the surface of collector within a given period.
Photo Electric conversion efficiency
Ƞe = (Im Vm)/( GA) (1)
Thermal efficiency is the ratio of useful thermal energy
output of the system to the incident solar irradiation on the
surface of collector within a given period.
Thermal Efficiency,
Ƞth = mcp (Tf - Ti) /( GA) (2)

_______________________________________________________________________________________
The sum of thermal and electrical efficiency is known as
overall efficiency and is commonly used to assess the
overall performance.
Overall Efficiency, Ƞo = Ƞth + Ƞe (3)
Considered electrical energy as a high grade form of energy
gain, the energy saving efficiency ƞf is also used [1]: it is
defined as:
Energy saving efficiency,
Ƞf = (Ƞe/ Ƞpower) + Ƞth (4)
Where Ƞpower is the electric power generation efficiency of
the conventional power plants; its value can be taken as
38%.
2.2.1 Energy and Exergy Analysis
According to first law of thermodynamics,
in outE E (5)
General equation for the exergy balance:
in out lossEX E E  (6)
For the steady-state flow process during a finite time
interval, the overall exergy balance of the solar PV can be
written as follows [2].
Exergy Input = (Exergy Output + Exergy Loss +
Irreversibility) (7)
The energy conversion efficiency of the solar PV (ηenergy) is
calculated from the following equation: [3-4]. The current-
voltage characteristics of the electric circuit of solar cell can
be described by the following simplified equation
 
1 0 exp
sq V IR
A K T
I I I
  
 
  
   (8)
The electric power output of PV is:
Pel = I × V (9)
The maximum power output is given by:
Pmax = VOC × ISC × FF (10)
Pmax = Vmp × Imp
A dynamic thermal model proposed by Duffie and
Beekman, included a lump overall loss coefficient UL for a
unit area [5]. Exergy efficiency of the photovoltaic module
is also defined as the ratio of total output exergy to total
input exergy [2, 6, 7]. An exergy efficiency of the solar PV
can be defined as the ratio of the exergy gained by the solar
PV (exergy output) to the exergy of the solar radiation
(exergy input) [8].
Ƞex = (Ex output)/ (Ex input) (11)
Electrical Exergy in the output electrical power of PV
module [4]
Ex electrical = Voc x Isc x FF (12)
Table 2.4: Input parameter used for analysis
Input parameter Value
Nominal operating cell
temperature (NOCT)
41 o
C
Stefan Boltzmann constant
(σ)
5.67×10-8
W/m2
-K
Emissivity of the panel (ε) 0.9
Sun temperature 5800 K
3. RESULTS AND DISCUSSION:
The maximum global radiation reaches to 850 W/m2
and
maximum temperature of 44.7 0
C. Figure 3.1 shows the
variation of global radiation and ambient temperature with
time for PV. The maximum global radiation reaches to 990
W/m2
. Figure 3.2 shows the variation of front and back
temperature of panel of PV and PV/T. Back temperature of
PV/T is lower than PV because of heat transfer from panel
to flowing water. The back side temperature of PV panel
reaches upto 73 0
C whereas back side temperature of PV/T
reaches upto 65 0
C. Figure 3.3 shows the difference of inlet
and outlet temperature of water. The inlet water temperature
is kept below the ambient temperature for higher heat
transfer rate and better efficiency. The temperature of outlet
water exceeding 47.5 0
C and maximum inlet temperature
reaches upto 350
C. Figure 3.4 shows the variation of
electrical, thermal and overall efficiency with time for PV/T.
the electrical efficiency is around 6-7% and maximum of
9.7%, thermal efficiency exceeding 67% and overall
efficiency exceeds 69%. Figure 4.18 shows the variation in
electrical efficiency of PV/T and PV. The average electrical
efficiency of PV/T is 6.39% for the day and that for PV is
7.50%. Exergy efficiency is the ratio of exergy out to exergy
in. The exergy efficiency is exceeding 13% for the mass
flow rate of 0.0025 kg/sec. The maximum exergy input is
about 300 W/m2
. Exergy out is the addition of electrical
exergy and thermal exergy which is reaches up to 30.8
W/m2
.
Table 3.1: Test Result of PV and Partially Covered PV/T system
Time
Global
Radiation
(PV/T)
Global
Radiation
(PV)
Thermal
Efficiency of
PV/T
Electrical
Efficiency of
PV/T
Overall
Efficiency of
PV/T
Electrical
Efficiency of
PV system
Exergy
Efficiency
Energy Saving
Efficiency
10:00 640 767 46.509 9.765 56.275 8.789 13.310 46.766
11:00 690 888 51.198 8.277 59.476 8.352 12.156 51.416
12:00 707 918 53.206 7.181 60.387 8.176 12.341 53.395
13:00 850 990 48.873 6.758 55.631 6.578 10.130 49.050
14:00 770 826 47.153 6.041 53.195 8.107 10.603 47.312
15:00 542 666 39.228 6.755 45.983 7.595 9.948 39.405
16:00 250 375 47.102 4.067 51.170 9.466 4.588 47.209
17:00 150 210 67.601 2.373 69.865 2.946 2.820 67.660

_______________________________________________________________________________________
Figure 3.1: Variation of Electrical, Thermal and Overall
Efficiency of PV/T with Glass Cover
Figure 3.2: Variation of Inlet and Outlet Water Temperature
for PV/T with Glass Cover
Figure 3.3: Variation of Electrical Efficiency of PV and
PV/T with Glass Cover
Figure 3.4: Variation of Exergy IN, Exergy OUT and
Exergy Efficiency of PV/T with Glass Cover
Table 3.2: Comparison of various efficiencies of PV/T and
PV
S.
No.
Partially Covered Solar PV/T Hybrid System
Solar
PV
MassFlowRate
(kg/sec)
AverageElectrical
Efficiency(%)
AverageThermal
Efficiency(%)
AverageOverall
Efficiency(%)
AverageEnergy
SavingEfficiency(%)
AverageExergy
Efficiency(%)
AverageElectrical
Efficiency(%)
1 0.0025 6.39 50.11 56.49 50.27 9.48 7.50
4. CONCLUSION
This article has presented performance evaluation of the
partially covered photovoltaic thermal water collector. A
partially covered solar PVT system was successfully
designed and a preliminary study of this technology was
carried out in a university building of MANIT, Bhopal. The
surface temperature of solar PV panel is directly
proportional to intensity of solar radiation. With increase in
solar irradiance electrical efficiency increases but surface
temperature of solar panel also increases which can affect
the electrical performance of the PV system. With the
combination of solar PV and solar thermal system as PVT
system, the energy yield per unit area, can be improved. By
using the PVT technique partially covered with glass, it was
concluded from the experimental result that with the mass
flow rate of 0.0025 kg/ sec, the daily average electrical
efficiency was about 6.39%, the characteristic daily thermal
efficiency exceeded 67%, the characteristic average overall
efficiency was above 56.49% and the characteristic daily
energy saving was up to 67.66%. The exergy efficiency was
0
10
20
30
40
50
60
70
80
Efficiency(%)
Time
Thermal
Efficiency
of PV/T
Electrical
Efficiency
of PV/T
Overall
Efficiency
of PV/T
0
5
10
15
20
25
30
35
40
45
50
Temperature(0C)
Time
Ambient
Temp(oC)
Water
Temp IN
Water
Temp
OUT
0
2
4
6
8
10
12
Efficiency(%)
Time
Electrical
Efficiency
of PV/T
Electrical
Efficiency
of PV
system
0
2
4
6
8
10
12
14
0
50
100
150
200
250
300
350
ExergyEfficiency(%)
ExergyInandExergyOut
Time
Exergy IN
Exergy
OUT
Exergy
Efficiency

_______________________________________________________________________________________
exceeds 13%. The effect glass cover reduces the heat loses
but it also increases the reflective losses which can be seen
by comparing electrical efficiency of PV and PVT system.
The high efficiency of the combined system can shorten the
payback period of the entire system. The cost of adding the
collector to the PV module is not very significant compared
to the price of PV module itself. Therefore, the PV/T system
is worth developing in the industry.
NOMENCLATURE
ɳf Energy Saving Efficiency %
ɳth Thermal Efficiency %
ɳe Electrical Efficiency %
ɳo Overall Efficiency %
Voc Open circuit voltage V
V Voltage V
Vmp Voltage at maximum power
point
V
Imp Current at maximum power
point
A
Isc Short circuit current A
I Current A
FF Fill factor No units
m Mass flow rate Kg/sec
A Surface area of the module m2
G Global irradiance W/m2
K Boltzmann constant J/K
Pel Electrical power W
Pmax Maximum power W
T Temperature K
Ta Ambient temperature K
Tm Module temperature K
NOCT Nominal operating cell
temperature
o
C
ACKNOWLEDGEMENT
I am thankful to Dr. Appu Kuttan KK, Director, MANIT,
Bhopal for giving me an opportunity to carry this work. I
extend my sincere thanks to Dr. Manoj Gupta, Provost and
Dean (SET), Poornima University, Jaipur for his continuous
support and encouragement. I take this opportunity to
express my profound gratitude and deep regards to my guide
Dr. K. Sudhakar, Assistant Professor, Department of
Energy, MANIT, Bhopal, for his exemplary guidance,
monitoring and constant encouragement. I also express our
deep thanks to all the faculty and staff members of
Department of Energy, MANIT, from whom I got direct or
indirect cooperation.
REFERENCES
[1] Vokas G, Christandonis N, Skittides. Hybrid
photovoltaic-thermal systems for domestic heating and
cooling – a theoretical approach. Sol Energy 2006;80:607–
15.
[2] Wong, K.F.V., 2000. Thermodynamics for engineers.
University of M iami, CRC Press LLC.
[3] Sahin, A.D., I. Dincer and M .A. Rosen, 2007.
Thermodynamic analysis of solar photovoltaic cell
systems. Solar Energy M aterials & Solar Cells, 91:
153-159.
[4] Joshi, A.S., I. Dincer and B.V. Reddy, 2009.
Thermodynamic assessment of photovoltaic systems.
Solar Energy, 83(8): 1139-1149.
[5] Duffie, J. A, Beckman, W. A, 1991. Solar Engineering
of Thermal Processes, 2nd ed., John Wiley and Sons, New
York, USA.
[6] Bejan, A., 1998. Advanced engineering
thermodynamics. John W iley & Sons Ltd., Chichester,
UK.
[7] Kotas, T.J., 1995. The exergy method of thermal
plant analysis. M alabar, FL: Krieger Publish Company.
[8] Petela, R., 2003. Exergy of undiluted thermal
radiation. Solar Energy, 74: 469-488.
[9] Petela, R., 2008. An approach to the exergy analysis
of photosynthesis. Solar Energy, 82: 3 11-328.
[10] F. Sarhaddi, S. Farahat, H. Ajam, A. Behzadmehr.
2010. Exergetic Performance Evaluation of a Solar
Photovoltaic (PV) Array, Australian Journal of Basic and
Applied Sciences, 4(3): 502-519.
[11] Boyle, G., 2004. Renewable energy power for a
sustainable future. second ed., Oxford University Press,
Oxford.
[12] Watmuff, J.H., W .W .S. Charters and D. Proctor,
1977. Solar and wind induced external coefficients for
solar collectors, COMPLES 2, 56.
[13] Sukhatme, S.P., 1993. Solar energy, M cGraw-Hill,
pp: 83-139.
[14] Pratish Rawat, Mary Debbarma, Saurabh Mehrotra,
K.Sudhakar, Prakash Sahu, “Performance Evaluation of
Solar Photovoltaic/Thermal Hybrid Water Collector”
Impending Power Demand and Innovative Energy Paths,
ISBN: 978-93-83083-84-8, 278-285.
[15] Pratish Rawat, Mary Debbarma, Saurabh Mehrotra,
K.Sudhakar “Design, Development and Experimental
Investigation Of Solar Photovoltaic/Thermal (PV/T) Water
Collector System”, International Journal of Science,
Environment and Technology, Vol. 3, No 3, 2014, 1173 –
1183.
[16] Pratish Rawat, Pardeep Kumar, “Performance
evaluation of Solar Photovoltaic Thermal (PV/T) System,
Vol. 4, No. 8, 2015, 1466-1471.
[17] V.V. Tyagi, S.C. Kaushik, S.K. Tyagi, “Advancement
in solar photovoltaic/thermal (PV/T) hybrid collector
technology”, Renewable and Sustainable Energy Reviews
16 (2012) 1383– 1398
[18] Wei He et. al. “ Hybrid photovoltaic and thermal solar
collector designed for natural circulation of water” Applied
energy 83(2006) 199-210
[19] Boddaert S, Caccavelli D. Hybrid PVTh Panel
optimisation using a Femlab/ Matlab/Simulink approach.
Environment Identities and Mediterranean Area,
ISEIMA’06. In: First international Symposium on 2006.
2006. p. 121–6.
[20] Tiwari A, Sodha MS. Performance evaluation of hybrid
PV/thermal water/air heating system: a parametric study.
Renewable Energy 2006; 31: 2460–74.

_______________________________________________________________________________________
BIOGRAPHIES
Mr. Pratish Rawat is currently
working as Dy. HOD and Assistant
Professor in Department of
Mechanical Engineering in
Poornima University, Jaipur. He
obtained his B.E. in Mechanical
Engineering from R.G.P.V. Bhopal
and MTech in Renewable Energy
from Maulana Azad National
Institute of Technology (MANIT),
Bhopal. His major research area includes: Energy
Management and Audit, Climate Change, Hybrid System,
Solar Thermal & PV Systems, Wind Energy and Energy
Conservation. He has published number of research papers
in national and international journals. He also published
book on solar PV/T with LAP lambert academic publishing.
Dr. K. Sudhakar obtained his B.E in
Mechanical Engineering from
Government College of Engg., Salem
and M.Tech in Energy Management
from School of Energy And
Environmental Studies, Devi Ahilya
University, Indore and Ph.D from
National Insitute of Technology,
Tiruchirapalli.. He was awarded
Senior Research Fellowship by DST
and Young Scientist Award by Madhya Pradesh State
Council of Science and Technology, Bhopal. His major
research area includes: Climate Change, Carbon
Sequestration, Hybrid System, Plant Fuel cell, Algal Bio-
fuel, Solar Thermal & PV Systems, Wind Energy and
Energy Conservation. He has published more than 50
research papers in International Journal and Conference. He
is a Certified Energy Manager & Energy Auditor by BEE.
He has been a keynote speaker and resource person at
several International/National Conferences. He is currently
working as Assistant Professor in Energy Department,
Maulana Azad National Institute of Technology, Bhopal.

Performance analysis of partially covered photovoltaic thermal (pvt) water collector

Related slideshows

More Related Content

Performance analysis of partially covered photovoltaic thermal (pvt) water collector