FABRICATION OF SOLAR REFRIGERATOR

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2 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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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




CONTENTS


OBJECTIVE


INTRODUCTION


CONSTRUCTION PARTS


WORKING OF EQUIPMENTS


POWER CALCULATION


OPERATING SPECIFICATION


ADVANTAGES


LIMITATIONS


APPLICATIONS

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.



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





FIG
-
1. SOLAR FRIDGE

CONSTRUCTION PARTS


Solar panel


Battery


Thermoelectric device


Air blower








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 /
mm
2


V=(P
-
Q)(
T
2
-
T
1
)



where v=voltage induced,P,Q are photovoltaic
coefficient of two voltaic materials



T
1
&
T
2

are temperatures of two materials




SOLAR CELL

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


PbO


+

2
H

SO


2
PbSO


+

2
H

O


One

cell

has

nominal

output

voltage
2
.
1
v


Charging

can

be

done

to

restore

o/p

voltage




LEAD ACID CELL

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




THERMOELECTRIC DEVICE

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


Q
h
or

Q
c
=B*I=A*T*I


Q
h

or

Qc

is

heat

absorbed

or

expellded


B

is

diffrential

peltier

cofficient


I

is

flowing

current

in

circuit

PELTIER EFFECT

SEMICONDUCTOR MODEL

POWER CALCULATION


Q
h

= Q
C

+ P
in






COP = Q
C

/ P
in



Where:



Q
h

= the heat released to the hot side of the
thermoelectric (watts).


Q
C

=

the

heat

absorbed

from

the

cold

side

(watts)
.




P
in

=

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

Q
C
,

the

heat

load

in

watts

absorbed

from

the

cold

side

is

difficult,

because

all

thermal

loads

in

the

design

must

be

considered
.




By

energy

balance

across

the

hot

and

cold

junction

it

produces


Q
h

=



T
h
)

x

I

-

C

(
T
h

-

T
c
)

+

I
2

R/
2





Q
C

=



T
c
)

x

I

-

C

(
T
h

-

T
c
)

-

I
2

R/
2

(
17
.
7
)




R

=

R
A

+

R
B




C

=

(k
A
+

k
B
)

(A/L)




To get the max the heat absorbed from the cold side
(Q
C
); by differentiate the Q
c

to the electric current I,


d Q
c
/d I = 0


Then it produces


I
opt
.
= α
T
c

/R



Substitute for
I
opt
.

In Equation to get the max the heat
absorbed from the cold side



Q
C

(max) = [(Z T
c2
)/2
-

(
T
h

-

T
c
)] C



Where,


Z = Figure of merit for the material A and B = α
2

/ R
C



OPERATING SPECIFICATION

T
h

= 30
o
C = 303 K

T
c

= 5
o
C = 278 K

d = 0.1 cm

L = 0.125 cm

A = (π/4) (0.1)
2

=7.854 x 10
-
3

cm
2


Overall electric resistance (R) =
R
element

+
R
junction



= 1.1
R
element



= 1.1(
ρ
p

+
ρ
n
) (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


= 1.1 (0.001 + 0.0008) (0. 125 / 7.854 x 10
-
3
)


= 0.0315 Ω


Conduction coefficient (C) = (
k
p

+
k
n
) (A/L)


= (0.02 + 0.02) (7.854 x 10
-
3

/0.125) = 2.513 x 10
-
3

W/K


Figure of merit (Z) = (
α
p

-

α
n
)

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.



Q
C
= Q
C

(max) = N C [(Z T
c2
)/2
-

(
T
h

-

T
c
)]


10 = N (2.513 x 10
-
3
) [0.5 (1.636 x 10
-
3

x (278)
2
)
-

(25)]
N



=105couples







Rate

of

heat

rejection

to

the

ambient

(
Q
h
)



I
opt
.

=

(
α
p

-

α
n
)

T
c

/R



=

(
360

x

10
-
6
)

x

278
/

0
.
0315



=

3
.
2

A



Q
h

=

N

[(
α
p

-

α
n
)

T
h

x

I
opt

-

C

(
T
h

-

T
c
)

+

I
2
opt

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

=

Q
C

/

P
in



P
in

(Power

input

by

power

source

to

the

thermoelectric)

=

Q
h

-

Q
C



=

47

-

10

=

37

W








COP = 10 / 37



= 0.27


The voltage drop across the
d.c
. power source.



voltage drop (∆V) = P
in

/ I


= 37 / 3.2


= 12 volt(approx)




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

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
.





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
.


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
.








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
.



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
.


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