Solar refrigerator

1. FABRICATION OF SOLAR REFRIGERATOR
GUIDED BY:- SUBMITTED BY:-
KIRAN RAJ K RAVI KANT PANDEY
DEPARTMENT OF RAVISH KUMAR
MECHANICAL ENGG. RAJEEV KUMAR
VIKAS KUMAR
VIKASH KUMAR
SANTOSH ABHISHEK

2. CONTENTS
• OBJECTIVE
• INTRODUCTION
• CONSTRUCTION PARTS
• WORKING OF EQUIPMENTS
• POWER CALCULATION
• OPERATING SPECIFICATION
• ADVANTAGES
• LIMITATIONS
• APPLICATIONS

3. OBJECTIVE
• To design and develop a thermoelectric refrigerator in
order to produce a small quantity of refrigerating effect by
using Solar energy.
• To effectively use the low grade Solar energy rather than
using high grade energy.
• To design a refrigerating unit which will work without
any moving parts.
• To develop a vibration less refrigerator.

4. INTRODUCTION
• Freezing action means transfer of heat from low temperature
to a high temperature body
• Freezing effect can be produced by vapour compression,
vapour absorption, and thermoelectric effect
• Solar fridge works on the principle of thermo electric
refrigeration
• It is non conventional type of refrigeration used to produce
small amount of refrigeration
• The working principle is based on peltier effect

5. FIG-1. SOLAR FRIDGE

6. CONSTRUCTION PARTS
• Solar panel
• Battery
• Thermoelectric device
• Air blower

7. SOLAR PANEL
• Solar panel consists of solar photovoltaic cells which
converts solar energy into electrical energy
• One cell in the panel is capable of producing 0.45v is
when current is 0.27A /mm2
• V=(P-Q)(T2-T1)
where v=voltage induced,P,Q are photovoltaic
coefficient of two voltaic materials
T1&T2 are temperatures of two materials

9. SOLAR CELL

10. BATTERY
• The device consist of lead-acid cell
• Sulphuric acid is used as electrolyte
• Gives high load current of current rating (100-300)
A-hr
• The following chemical phenomena takes place
• PbO₂ + 2H₂SO₄ 2PbSO₄ + 2H₂O
• One cell has nominal output voltage2.1v
• Charging can be done to restore o/p voltage

11. LEAD ACID CELL

12. THERMOELECTRIC DEVICE
• Thermoelectric device are pair of two dissimilar
metals, semiconductors or conductor with
semiconductor.
• The pair should have high electrical conductivity but
low thermal conductivity because we are working
with low amount of refrigeration.
• In this system the device is made of extrinsic
semiconductor having p-n junction in series with
required no of cells.
• The energy difference of conduction band of material
should be high for higher refrigeration

13. THERMOELECTRIC DEVICE

15. WORKING PRINCIPLE
• System works on peltier effect
• As d.c supply is provided there is formation of hot
and cold junctions
• The heat absorbed or expellded is given by
Qhor Qc=B*I=A*T*I
• Qh or Qc is heat absorbed or expellded
• B is diffrential peltier cofficient
• I is flowing current in circuit

16. PELTIER EFFECT

17. SEMICONDUCTOR MODEL

18. POWER CALCULATION
• Qh = QC + Pin
•
• COP = QC / Pin
Where:
• Qh = the heat released to the hot side of the
thermoelectric (watts).

19. • QC = the heat absorbed from the cold side (watts).
• Pin = the electrical input power to the thermoelectric
(watts).
• COP = coefficient of performance of the
thermoelectric device, typically is between 0.4 and 0.7
for single stage applications.
• Estimating QC, the heat load in watts absorbed from the
cold side is difficult, because all thermal loads in the
design must be considered.

20. • By energy balance across the hot and cold junction it
produces
• Qh = (α Th) x I - C (Th - Tc) + I2 R/2
• QC = (α Tc) x I - C (Th - Tc) - I2 R/2 (17.7)
• R = RA + RB
• C = (kA+ kB) (A/L)

21. • To get the max the heat absorbed from the cold side
(QC); by differentiate the Qc to the electric current I,
• d Qc /d I = 0
• Then it produces
• Iopt. = α Tc /R
• Substitute for Iopt. In Equation to get the max the heat
absorbed from the cold side
• QC (max) = [(Z Tc2)/2 - (Th - Tc)] C
Where,
Z = Figure of merit for the material A and B = α2 / R
C

22. OPERATING SPECIFICATION
Th = 30oC = 303 K
Tc = 5oC = 278 K
d = 0.1 cm
L = 0.125 cm
A = (π/4) (0.1)2 =7.854 x 10-3 cm2
Overall electric resistance (R) = Relement + Rjunction
= 1.1 Relement
= 1.1(ρp + ρn) (L/A)
p n
α (V/K) 170 x 10-6 -190 x 10-6
ρ (Ω.cm) 0.001 0.0008
k (W/cm K) 0.02 0.02

23. = 1.1 (0.001 + 0.0008) (0. 125 / 7.854 x 10-3)
= 0.0315 Ω
• Conduction coefficient (C) = (kp + kn) (A/L)
= (0.02 + 0.02) (7.854 x 10-3 /0.125) = 2.513 x 10-3 W/K
• Figure of merit (Z) = (αp - αn) 2/ RC
= (360 x 10-6)2/ (0.0315 x 2.513 x 10-3)
= 1.636 x 10-3 K-1
• Number of couples required.
QC = QC (max) = N C [(Z Tc2)/2 - (Th - Tc)]
10 = N (2.513 x 10-3) [0.5 (1.636 x 10-3 x (278)2) - (25)]
N
=105couples

24. • Rate of heat rejection to the ambient (Qh)
Iopt. = (αp - αn) Tc /R
= (360 x 10-6) x 278/ 0.0315
= 3.2 A
• Qh = N [(αp - αn) Th x Iopt - C (Th - Tc) + I2opt R/2]
= 105 [(360 x 10-6) 303 x 3.2 - 2.513 x 10-3 (25)
+(3.2)2 0.0315/2]
= 47 W
• COP = QC / Pin
Pin (Power input by power source to the thermoelectric) =
Qh - QC
= 47 - 10 = 37 W

25. • COP = 10 / 37
= 0.27
• The voltage drop across the d.c. power source.
voltage drop (∆V) = Pin / I
= 37 / 3.2
= 12 volt(approx)

26. OBSERVATION OF WORKING PARAMETERS
•
CHANGE
IN
TEMP
TIME
2 4 6 8 10 12 14 16 18 20 22
2
4
6
8
10
12
14
16
18
20
22
Current-3.2amp
Voltage-12V

27. ADVANTAGES
• No moving parts, hence operation is noiseless.
• Simple and fewer parts are required.
• Less power consumption.
• Maintenance cost is low.
• Easily portable.
• Suitable for low capacity.
• Compact in size.
• The weight per unit refrigeration is considerably
lower than conventional refrigeration system.

28. • An interchange of heating and cooling process can be
exercised by reversing the polarity.
• An important advantage of this refrigeration system is
the independence of C.O.P. on the size of thermo-
electric refrigerator and this makes it particularly
attractive to use peltier cooling when the cooling
capacity required is high.
• It is free from vibration of any kind unlike the vapour
compression refrigeration, which uses compressor
making it to vibrate.

29. LIMITATIONS
• Low C.O.P.
• Advantageous only for units of smaller capacity.
• Can not be used for large freezing requirement.
• Unavailability of suitable materials of high figure of
merit.

30. APPLICATION
• Peltier refrigerators are widely used in several western
countries.
• Serum coolers for preservation of blood plasma and
serums.
• Photo multiplier cooler.
• Dew point hygrometer for determining absolute humidity.
• Constant low temperature bath and chambers.

31. CONCLUSION
• In this work, a portable thermoelectric generator unit was
fabricated and tested for the cooling purpose. The refrigerator
was designed based on the principle of a thermoelectric
module to create a hot side and cold side. The cold side of the
thermoelectric module was utilized for refrigeration purposes
whereas the rejected heat from the hot side of the module was
eliminated using heat sinks and fans. In order to utilize
renewable energy, solar energy was integrated to power the
thermoelectric module in order to drive the refrigerator.

32. Furthermore, the solar thermoelectric refrigerator avoids
any unnecessary electrical hazards and provides a very
environmentally friendly product. In this regard, the
solar thermoelectric refrigerator does not produce
chlorofluorocarbon (CFC), which is believed to cause
depletion of the atmospheric ozone layer. In addition,
there will be no vibration or noise because of the
difference in the mechanics of the system. In addition
the rejected heat from the solar thermoelectric
refrigerator is negligible when compared to the rejected
heat from conventional refrigerators. Hence, the solar
thermoelectric refrigerator would be less harmful to the
environment