Experimental Investigation of the potentiality of Nanofluid in enhancing the performance of Hybrid PV/T systems. The global need for energy savings requires the usage of renewable sources in many applications. Harnessing solar energy using photovoltaic cells which converts solar radiation into electricity seems a good alternative to fossil fuels. However the heat trapped in photovoltaic cells during operation decreases the efficiency of the system. To avoid the temperature increase of the PV system we use photovoltaic-thermal hybrid solar system (Hybrid PV/T) where the unfavourable absorbed heat from the cells is collected through an additional thermal unit. Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid. Generally, the nanofluids possess greater heat transfer characteristics compared to the common fluids.

1. Experimental Investigation of potentiality
of Nanofluid in enhancing the
performance of Hybrid PV/T systems
Varun Goyal, Prakhar Chaturvedi and Faisal Khan.
Project Supervisor:- Dr. Syed Mohd Yahya

2. Contents:-
2
 Introduction
 Literature Review
 Methodology
 Formulae used
 Uncertainty Analysis
 Results and Conclusions
 Future Scope
 References

3. INTRODUCTION
The global need for energy savings requires the usage of renewable sources in many applications.
Harnessing solar energy using photovoltaic cells which converts solar radiation into electricity seems
a good alternative to fossil fuels.
However the heat trapped in photovoltaic cells during operation decreases the efficiency of the
system.
To avoid the temperature increase of the PV system we use photovoltaic-thermal hybrid solar
system (Hybrid PV/T) where the unfavourable absorbed heat from the cells is collected through an
additional thermal unit.
Nanofluids are engineered colloidal suspensions of nanoparticles in a base fluid.
Generally, the nanofluids possess greater heat transfer characteristics compared to the common
fluids.
3

4. Role of nanofluids in PV/T systems:-
An extensive literature survey showed that the impending roles in which
nanofluids are employed in a PV/T systems are:-
4
1. As a coolant
2. As an Optical
Filter

5. Evolution of PV/T systems
• PV systems get heated due to non-direct absorption with continuous operation which results in the
increase of the PV cell working temperature
• This absorbed heat causes problems such as decrease in efficiency of the system and may also lead
to permanent circuit damage if conditions persist of too long.
• Thus, a non-inflammable fluid is generally chosen which flows beneath the PV panel and acts as a
heat exchanger.
• It absorbs the solar thermal energy directly, reducing the heat loss and hence enhancing the thermal
efficiency.
• The system formed in this way is called a photovoltaic thermal (PV/T) system, which can supply
electrical and thermal energy simultaneously.
5

6. Schematic of PV/T system with nanofluid as a coolant
6

7. Application of Nanofluid as a coolant
• Here, nanofluids are employed as thermal absorbers and take away heat from the PV
panels either through direct contact or channel contact.
• Reviewing the literature, it can be observed that different types of geometries have
been studied to investigate the effect of nanofluids in cooling of PV/T systems, which
are: -
A. Microchannel
B. Sheet and tube configuration
C. Single rectangular channel
D. Serpentine shaped channel
We have employed “ Serpentine shaped channel” geometry in our
experimental work.
7

8. 8
Microchannel Heat
Exchanger (A)
Other Types (B,C,D)
Serpentine geometry being
used in experiment

9. LITERATURE REVIEW
9

10. METHODOLOGY
• Nanofluids were prepared by the two step process.
• Zinc nanopowder of APS 50 nm was purchased from Sisco Research Lab Pvt Ltd.
• 3 different solutions of concentration 0.3% by volume was prepared with Zn nanoparticles in 3
different basefluids; Water, Water(75%) with Ethylene Glycol(25%) and Water(75%) and
propylene Glycol(25%). In each case sonication was performed in an Ultra sonic bath for 2 hrs. to
produce colloidal solutions.
• A closed circuit for the flow of nanofluid was established with the heat exchanger and a pump in
between. Thermocouples are attached at different points to measure the temperature.
• Setup was then run at a constant flow rate of 2 LPM (0.033kg/s)and the readings were taken at
intervals of 30 min.
• Intensity of radiation was varied after every half an hour, starting from 700W/m𝟐to 900
W/m𝟐 to simulate the outdoor conditions.
• Instruments and the flow chart of circuit is shown in the next slides.
10

11. Line diagram of the experimental setup:-
11

12. Part Specifications:-
COMPONENT DESCRIPTION
Hybrid PV/T panel 300W, Collector area 1.44m2
Battery Amaron; 12V, 100Ah
Pump Metro; 165-250Volts,
Power: 12W
Hmax= 1.5-2.8 m of water
Flowmeter Capacity:- 0-2 LPM
Datalogger E&E, 8 channel data logger
Infrared Thermometer HTC; MT4
Range: -50 to 550 °C
Heat Exchanger Air cooled fin type
Thermocouple Range 0 to 500 °C
Nickel-Chromium(K type)/Metal wire
Solarimeter Tenmars electronics; TM 206
Solar simulator Halonix; 49 Halogens of 150 watts each
Charge controller Sukam; MPPT Charge controller
12

13. FORMULAE USED
After taking all the readings, electrical and thermal efficiencies of the hybrid PV/T system
would be evaluated to investigate the effect of nanofluids.
Assuming a steady state condition of the system, energy balance can be applied as:-
𝐸𝑖𝑛 = 𝐸𝑜𝑢𝑡
which implies,
𝐸𝑖𝑛
.
= 𝐸.
𝑒𝐼 + 𝐸𝑡ℎ
.
+ 𝐸𝑙𝑜𝑠𝑠𝑒𝑠
.
where E in is the incident solar irradiation to the PV/T,
Eel the output electrical power,
Eth the useful thermal energy gained from the collector,
Elosses is the energy loss for the control volume.
13

14. FORMULAE USED (cont.)
• 𝐸𝑡ℎ can be calculated by a simple energy analysis as:-
where:-
mf is the fluid mass flow rate through the collector,
Cpf is the fluid specific heat, and
Tfi and Tfo represent the fluid inlet and outlet temperatures from the collector, respectively.
• The thermophysical properties of the prepared nanofluids are calculated from water and
nanoparticles characteristics at the bulk temperature using following empirical relations:-
• For Density of the mixture:-
𝜌𝑛𝑓 = 𝜑𝜌𝑛 + 1 − 𝜑 𝜌𝑏𝑓
And
𝜌𝑏𝑓 = ∅𝜌𝑓1 + 1 − ∅ 𝜌𝑓2
14
Eth = 𝑚𝑓.𝐶𝑝,𝑓. 𝑇𝑓,𝑜 − 𝑇𝑓,𝑖

15. FORMULAE USED (cont.)
• For the Specific Heat Capacity of the mixture:-
𝐶𝑝,𝑛𝑓 =
𝜑. 𝜌𝑛.𝐶𝑝,𝑛 +(1−𝜑). 𝜌𝑏𝑓.𝐶𝑝,𝑏𝑓
𝜌𝑛𝑓
And
𝐶𝑝,𝑏𝑓 =
∅. 𝜌𝑓1.𝐶𝑝,𝑓1 +(1−∅). 𝜌𝑓2.𝐶𝑓2
𝜌𝑏𝑓
• where 𝜌 is the density and subscripts n, bf and nf represent, nanoparticles, base fluid, and nanofluid
respectively.
• 𝜑 is the volumetric ratio of nanoparticles in a suspension solution of the base fluid that can be
calculated by the following:-
𝜑 =
𝑚𝑛
𝜌𝑛
𝑚𝑛
𝜌𝑛+
𝑚𝑏𝑓
𝜌𝑏𝑓
• where mn and mf are the mass of the nanoparticles and fluid respectively.
15

16. FORMULAE USED (cont.)
• ∅ is the volumetric ratio of fluids in the base fluid solution that can be calculated by the following:-
∅ =
𝑚𝑓1
𝜌𝑓1
𝑚𝑓1
𝜌𝑓1
+
𝑚𝑓2
𝜌𝑓2
• where mf1 and mf2 are the masses of the fluids, used to prepare the base fluid.
• Thus thermal efficiency can be expressed as:-
ηth =
𝐸𝑡ℎ
𝐸𝑖𝑛
• The electrical efficiency can be expressed as:-
ηel ≡
𝐸𝑒𝑙
𝐸𝑖𝑛
=
𝑉𝑜𝑐×𝐼𝑠𝑐×𝐹𝐹
𝐺𝑒𝑓𝑓× 𝐴𝑐
16

17. FORMULAE USED (cont.)
• Where,
• Voc is the open circuit voltage
• Isc is the short circuit current.
• FF is fill factor (for polycrystalline PV panels the value of fill factor is 0.89).
• Geff is the mean of the incident radiation measured from solar power meter.
• 𝑨𝒄 is the area of collector.
17

18. UNCERTAINTY ANALYSIS
An uncertainty analysis is performed on both thermal and electrical efficiencies. The uncertainties associated
with the measuring instruments of the experimental setup are reported in Table 3.
If R is a function of ‘n’ independent linear parameters as;
R = R (v1, v2, v3…vn), the uncertainty of function R may be calculated
As:-
𝑅 =
𝑅
𝑣1
𝑣1
2
+
𝑅
𝑣2
𝑣2
2
+ ⋯ +
𝑅
𝑣𝑛
𝑣𝑛
2
Where R is the uncertainty of function R, vi the uncertainty of parameter vi, and R/vi is the partial
derivative of R with respect to the parameter vi.
18

19. UNCERTAINTY ANALYSIS (cont.)
Equipment and model Measurement section Accuracy
Digital multimeter Voltage ±(0.5%+1)V
Digital multimeter Current ±(0.8%+1)A
Solar power meter Incident solar radiation ±10 W/m2
Infrared thermometer PV surface temperature 0.14°C
Thermocouple Fluid temperatures ±0.15-0.25°C
Mercury thermometer Ambient temperature ±0.5°C
Rotameter Mass flow rate ± 1kg/hr
19

20. UNCERTAINTY ANALYSIS (cont.)
Using the above equations and recalling fractional uncertainties of the sun input and the thermal/electrical
outputs calculated from the table, the maximum fractional uncertainty of the electrical efficiency can be
calculated by considering the maximum uncertainties for each parameter based on the following equation:-
𝜂𝑒𝑙 = 𝑓 𝐺, 𝑃𝑒𝑙 =
𝛿𝜂𝑒𝑙
𝜂𝑒𝑙
= ±
𝑉
𝑉
2
+
𝐼
𝐼
2
+
−𝐺
𝐺
2
= ±0.019
which means that the maximum uncertainty of the electrical efficiency in the experiments is 1.9%.
Using a similar method, the maximum uncertainty for thermal efficiency is calculated as:-
𝜂𝑡ℎ = 𝑓 𝐺, 𝑇𝑖𝑛, 𝑇𝑜𝑢𝑡, 𝑚 =
𝛿𝜂𝑡ℎ
𝜂𝑡ℎ
= ±
𝑇
𝑇
2
+
𝑚
𝑚
2
+
−𝐺
𝐺
2
= ±0.029
It can be seen that the maximum absolute uncertainty for all parameters is less than 3% in the experiments.
This is an indication of the reliability of the measured data. 20

21. RESULTS AND CONCLUSIONS
The results of the experimental investigation are presented here:-
21
0
2
4
6
8
10
12
10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30
el
Time
Electrical Efficiency (el v/s Time)
Electrical Effeciency with Water only (%) Electrical Effeciency with Zn-Water Nanofluid (%)
Electrical Effeciency with Zn-(Water+Propylene Glycol) Nanofluid (%) Electrical Effeciency with Zn-(Water+Ethyleen Glycol) Nanofluid (%)

22. 22
0
10
20
30
40
50
60
70
80
90
10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30

th
(%)
Time
Thermal Effeciency (thv/s Time)
Thermal Effeciency with Water only (%) Thermal Effeciency with Zn-Water Nanofluid (%)
Thermal Effeciency with Zn-(Water+Propylene Glycol) Nanofluid (%) Thermal Effeciency with Zn-(Water+Ethylene Glycol) Nanofluid (%)

23. 23
0
10
20
30
40
50
60
70
80
10:00 10:30 11:00 11:30 12:00 12:30 1:00 1:30 2:00 2:30 3:00 3:30
PV
TEMP.(
O
C)
TIME
PV SURFACE TEMP.
PV temp. with Water
only
PV temp. with Zn-Water
Nanofluid
PV Temp.
with Zn-(Water+Propylene Glycol) Nanofluid
PV Temp.
with Zn-(Water+Ethylene Glycol) Nanofluid

24. Cumulative Energy Output
24
0
100
200
300
400
500
600
700
With water only With Zn- Water With Zn- Water + 25%
Propylene Glycol
With Zn- Water + 25%
Ethylene Glycol
322
415
532
610
167
195
290
350
Cumulative
Energy
Output
(KWh/m
2
)
Total thermal energy output Total electrical energy output

25. Conclusions
• Thermal efficiency and Electrical efficiency obtained of the hybrid PV/T system is highest when its
cooled by Zn-(Water+Ethylene Glycol) nanofluid and least in the case when its only cooled by water.
• The maximum change in electrical efficiency observed is 2.6% and maximum change in thermal
efficiency observed is 31%.
• Electrical efficiency of the Hybrid PV/T system decreases with time, as the operation time of the
solar panel increases its resistance increase, current generating capacity decreases and hence its
power generation capacity.
• Thermal efficiency of the Hybrid PV/T system increases with time as the operation time of the panel
increases because more temperature difference is obtained across the heat exchanger.
• PV Panel surface temperature also is least in case of Zn-(water+Ethylene Glycol) Nanofluid cooled
hybrid system and maximum in the case of water cooled system.
• PV surface temperature increase with time in all the 4 cases of cooling because of its continuous
operation.
• Zn-(Water+Ethylene Glycol) Nanofluid gives most drop in surface temperature as compared to other
3 liquids/coolants. During our experiment the maximum temperature difference between water
cooled and Zn-(Water+Ethylene Glycol) Nanofluid cooled PV Panel is 190C.
25

26. FUTURE SCOPE
• Concentrations and mass flow rates can be varied of nanofluids in the system to check their effects.
• Combination of different nano materials possessing various desired thermal properties can be tested.
• The PV/T systems which apply nanofluids as the optical filter, and can use phase change materials
(PCMs) or thermoelectric devices for cooling of PV cells can be another attractive new subject.
• Use of ETFE (Ethylene Tetrafluoroethylene) layer as a front coating on PV panels can be employed.
• Research on building-integrated nanofluid-based PV/T could be advantageous.
26

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29. ThankYou