Experimental analysis of solar powered ventilation

INTERNATIONALMechanical Engineering and Technology (IJMET), ISSN 0976 –
International Journal of JOURNAL OF MECHANICAL ENGINEERING
6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME
AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)
IJMET
Volume 3, Issue 3, September - December (2012), pp. 471-482
© IAEME: www.iaeme.com/ijmet.asp ©IAEME
Journal Impact Factor (2012): 3.8071 (Calculated by GISI)
www.jifactor.com

EXPERIMENTAL ANALYSIS OF SOLAR POWERED VENTILATION
COUPLED WITH THERMO ELECTRIC GENERATOR ON
UNROOFED PARKED VEHICLES
Ganni Gowtham1, Ksitij Kumar2, S.S Charan3, K Manivannan4
1
(Vellore Institute of Technology, Vellore, India, ganni.gowtham14@gmail.com)
2
(Vellore Institute of Technology, Vellore, India, ksitiz52@yahoo.co.in)
3
(Vellore Institute of Technology, Vellore, India, samanchicharan@gmail.com)
4
(Professor, SMBS, Vellore Institute of Technology, Vellore, India, kmanivannan@vit.ac.in)

ABSTRACT

We have parked our vehicles in an open space under direct sunlight and observed the
increase in vehicle’s interior temperature due to various means of heat transfer and
greenhouse effect. We observed that, under hot weather conditions, vehicle’s interior
temperature can rise by Twenty degrees or more in thirty minutes which is also a serious
threat for children or pets left inside the vehicle. It is reported that in United States, about 38
children are dying every year in the vehicle because of rapid rise in vehicle’s interior
temperature [6]. In some situations, where parking roofs are not present, vehicle has to be
parked under direct sunlight most of the time. As a result, vehicle’s interior gets heated
causing thermal discomfort to the driver and passengers inside the vehicle. Sometimes,
Temperature rise in vehicle’s interior destroys the electronic gadgets left inside the vehicle.
Our experiment aims at the study of providing ventilation by using renewable energy along
with waste heat recovery from the vehicle. Solar panel along with a Thermo Electric
Generator (TEG) is used which will generate sufficient power to run a DC Ventilator. Solar
Panel and TEG powers the battery, the battery in turn powers the DC ventilator at constant
voltage. The ventilator inhales fresh air from outside (i.e atmosphere) into the interior of
vehicle and exhales hot air outside. Due to the mass transfer of hot air, the temperature inside
the vehicle can be maintained at required level. Temperature sensors are used to measure the
temperatures inside and outside the vehicle. Excess of power generated can be stored in the
battery which can be used to power vehicle’s head lights and small scale appliances.

Keywords – Thermo Electric Generator, Ventilation, ventilator, thermocouple, solar panel,
waste heat recovery

I. INTRODUCTION
According to the data observed by the World Meteorological Organization, the sun irradiates
the surface of the earth with at least 120 watts per square meter during daytime. The potential

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –

for solar energy is huge. Recent technological advancements have enabled us to harness the
electrical energy produced by the solar radiation falling on earth. Many devices have been
developed like the photo voltaic cells that convert the sun’s energy into electrical potential
that can power devices. Due to the recent developments in size, material, fabrication and
design of PV panels they are easily accessible and portable. Solar powered vehicles have
been powered by PV panels as well as devices like mobiles and laptops. Although solar
energy is abundant but methods to exploit it are limited and costly. Solar panels can be
mounted on the roof of the vehicles to supply energy to recharge the batteries.

I = IP – II – ISc
Where:-
I = current given as output (amperes)
IP = current generated by photons (amperes)
II = current through diode (amperes)
ISc = current through shunt (amperes).

The current can be governed by the voltage equation through the circuital elements.

VH = I + I*RS
Where:-
VH = voltage across both diode and resistor (volts)
V = voltage at output terminals (volts)
I = current as output (amperes).
RS = resistance in series ( ).

Thermo electric generator also known as TEG works on the principle of thermoelectric effect
where direct conversion of temperature difference to electric potential takes place. It creates
voltage due to temperature difference on either sides of the conductor popularly known as
Seeback effect.
The voltage V obtained is derived from equation :

V = ‫׬‬TT12 ቀSB ሺTሻ-SB ሺTሻቁ dT (1)
Where:-
SA = Seebeck coefficients of metals A as a function of temperature
SB = Seebeck coefficients of metals B as a function of temperature
T1 = temperatures of the junction 1(K)
T2 = temperatures of the junction 2(K)
One major applications of TEG in automotive industry is to recover waste heat from the
exhaust of the engine. By placing a TEG at the exhaust of the vehicle we extract heat and
convert it into potential energy that can be used to power the electronics or recharge battery
of the car. Research in waste heat recovery is being carried out by BMW in their new energy
efficient cars.
The purpose of our experiment was to apply old model to develop a new approach for
ventilation in cars. The existing approach to supply ventilation required use of power from
car battery which could easily drain the battery power. Our model coupled the use of a TEG
with solar panels to provide ventilation of the car without using car battery. We could use it
while our car is parked as well as when the car is moving.

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Sep

II. PV SOLAR CELLS
The use of PV solar cell modules connected together I arrays of parallel and series circuits
ll se
enable current and voltage oriented dispo
dispositions that allow capturing a distribution of the
energy generated at a DC level of 12V, 24V or 48V. PV conversion of solar energy into
electricity is performed from semiconductor materials junctions that form layers of p and n
doped surfaces where photons coming from the sun overcome the photo-electronic band-gap
ectronic
generating an electron flux. The photoelectric effect is the base of such conversion.
Applications on standard medium size energy generation are based on flat solar PV panel
located in house roofs, buildings and on the fields. In 1990 started [1] the use of solar energy
ted

panels on the roof of small automobiles. Use of solar cells in vehicles had the goal to ful fill
full
individual requirements and comfort such as charging auxiliary batteries for air-conditioning,
air-
radio, charging GPS system, mobile phones or to maintain the temperature required inside the
obile
cabin, motor and air-conditioning for fast start. Total capacity of PV modules currently used
conditioning
is approximately 165-215 Watts, [2,3] though the limited surface available on the automobile
215
roof is a constraint, as efficiency and capacity of cells improve, nominal power will increase
greatly and their use could soon be standardized. Fig1 indicates the PV used for the
experiment.

Fig. 1 PV Solar Panel

III. THERMOELECTRIC GENERATOR
Thermoelectric generators (also called thermo generators) are devices which transform heat
nerators
(temperature differences) directly into electrical energy, using a phenomenon called the
"Seebeck effect" (or "thermoelectric effect"). Their probable efficiencies are around 5-10%.
5
One major applications of TEG in automotive industry is to recover waste heat from the
exhaust of the engine. By placing a TEG at the exhaust of the vehicle we extract heat and
convert it into potential energy that can be used to power the electronics or recharge battery
recharge
of the car. Research in waste heat recovery is being carried out by BMW in their new energy
efficient cars. Fig2 shows Thermo electric generator

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Sep

Fig. 1 CAD Model of TEG
IV. DETERMINATION OF TEMPERATURE INSIDE A PARKED CAR
A Swift VDI car is used for experimentation. The following are the specifications of a car.
ar

Overall length 3760 mm
Overall width 1690 mm
Overall height 1530 mm
Seating capacity 5 persons
Colour White
Glass type Tinted glass

Location: VIT University (12° 55' N, 79° 11' E)

Table 1 Observations
Where: -

Ti - Inside cabin temperature
nside
To - Ambient temperature
∆T - (Ti-To)
Q - Amount of heat generated inside cabin
Cp - Specific heat at constant pressure
(1.005 KJ/Kg/°c)

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300

Heat Generated (kJ)
250
200
150
100
50
0
03:40 03:50 03:55 04:05 04:10 04:15 04:20
Time (s)

Fig. 3 Graph for heat generated

From the above analysis, it is clear that, within short span of one hour, the heat generated
inside cabin raises to 260 joules. To remove this heat, a ventilator or a cooling fan can be
used
V. SELECTION OF VENTILATORS

Ventilator and ventilators provide air for ventilation and industrial process requirements.
To decide the ventilator or cooling ventilators, one should know the parameters like static
pressure, maximum and minimum operating temperatures, rated power (operating voltage
and current) [1,2]
In enclosures and cabinets with highly efficient and sensitive electronic components heat
can also become a problem, especially with increasing packing density. Furthermore there is
a risk that the service life of components, e.g. semi-conductors, might be reduced when the
maximum operational temperature is exceeded. By using filter ventilator the generated heat
in enclosures can effectively be eliminated and thus ensure trouble-free operation of
electronic components.

Using the following calculations to correctly assess the required filter ventilators
performance which are taken from an open internet source[6].

1. Temperature differential
Variations in temperature (e.g. day-night, summer-winter, climate zones) have to be taken
into account. Please enter the maximum temperature differential or determine the temperature
differential in the enclosure based on the desired interior temperature (Ti) and the expected
ambient temperature (Tu):
Maximum ambient temperature 42.5°c
Maximum interior temperature 60°c
Temperature differential 17.5K

2. Installed stray power
The components installed in enclosures (e.g. transformers, relays, semi-conductors, bus bars,
etc.) generate heat when in operation. This self-warming is described as stray power, power
loss or dissipation. In this case, it is power generated inside the cabin.
Installed stray power 260W

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Sep

3. Air constant
The air constant f is determined by the altitude (above sea level) at the place of installation.
It factors in decreasing barometric pressure and air density with increasing altitude.
Altitude (above sea level) in meters 0 to 100 meters
vel)
Air Constant 3.1 m3/KWh

4. Calculation
Required volume flow 21.17 cfm

So, the theoretical calculations show that around 22 cfm capacity should be used in cars. it’s
o,
safe if we use within the range of 30 30-40cfm. There are many ventilators and cooling
ventilator with the specified capacity and operating voltage and currents range between .7 and
and .
13 volts. Small ventilators of size 97x33mm (for example) can be installed as shown in the
figure 4 below.

The source of heat penetration through car is the tinted glass windows. So, it can be placed
f
near steering and at the top of roof. To run the ventilator or cooling ventilators, it’s better to
,
go for green technology like usage of solar panels or waste heat recovery from exhaust gases.
from
So, here we can use combined system of solar panels and thermoelectric generators (TEGs)
to harvest energy.

Fig. 4 Placement of ventilator
VI. IMPLEMENTATION OF VENTILATION SYSTEM
As already observed, we are using ventilators to ventilate the car. To further optimize it,
e
and make it more efficient, it is necessary to control the power supplied to the ventilators,
based on requirement. This power controller is necessary in a time like this, where our
conventional power sources are fast exh
exhausting. [2, 3] Moreover a car runs on a battery, i.e.
a fixed power source, on the move. So, it is necessary to optimize its consumption. The idea
here is to vary the power of ventilator, based on the temperature difference. A circuit which
ventilator,
shows a linear output with respect to input is chosen. The working of this circuit can
ar
explained using a simple block diagram.

476

Sep

Fig. 5 Block Diagram
VII. SIMULATION
As one can see, the circuitry consists of two temperature sensors, one inside the car and
another outside the car. These sensors produce a voltage which is proportional to the
temperature of the surroundings. These two voltages are sent thru a differential amplifier,
which gives the difference of the voltages. So, whenever the inside temperature and outside
temperature are equal, the output of the differential amplifier would be zero. Otherwise, the
emperature
output grows linearly with the temperature difference. This is sent through SCC block which
has the ability to shift the voltage levels to required range, which is compatible as inputs for
next stage. And finally a “voltage controlled voltage source” controls the voltage to be given
out, hence controlling the power and rpm of the ventilators.

Fig. 6 A simple amps based circuit
We considered waste heat as first alternative. For this a thermo electric generator (TEG)
alternative.
can be used and its characteristics can be observed. An experiment was conducted on TEG
ducted
module HT 8-12-40 and the following reading is taken. Based on the study of existing

477


systems and project-relevant theories as well as different tests to evaluate the potential of
waste heat recovery a thermoelectric system was developed.
Unlike other approaches, that include a separate installation of the generator in the exhaust
gas line, the concept of this work suggests the integration in the muffler of the vehicle.
[4,5]The thermoelectric module as shown has many thermoelectric generators connected in
series with bimetallic strips inside to cut-off the modules from heat exchangers when
operating temperatures of heat exchangers exceeds the operating temperatures of TEG’s.
The following table represents the readings of thermoelectric generator of model number
HT8-12-40.

Table 2 Readings are taken for one thermoelectric module

1
0.8
Voltage (V)

0.6
0.4
0.2
0
14.17 17.38 20.89 32.27 46.92 55.65 67.11
Temperature difference (°C)

Fig. 7 Graph for temperature difference

VIII. SOURCE CHARGING CIRCUIT
As discussed earlier, these ventilators require power to run. Constant usage of power, when
car is parked can drain away the battery. So as an alternative solar power can be used. In here
power from solar panel is used to charge battery. A general solar charging circuit is used here.
The figure below illustrates the circuit diagram. A voltage regulator LM317 is used here to
provide required voltage [6] to charge the batteries. Transistor here acts as a switching circuit
which increases the efficiency when the output is finally taken through a low pass filter.

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6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep Dec (2012) © IAEME
Sep-

Fig. 8 A general solar charging circuit used to charge batteries

The solar panel charge the batteries, which prevents draining of them. As mentioned earlier
e
this unit is producing a constant voltage of more than 12V, sufficient to charge the batteries.
A similar circuitry can be used to harness power from TEG. But for this we need a lot of
TEGs connected in series which is highly expensive. The designed circuitry is implemented
imple
on a bread board. This circuitry was able to drive two cooling ventilator which are
ventilators,
estimated to consume a power of 4W. With a better MOSFET higher output power can be
delivered. Below photo illustrate the real time working of the circuitry.

Fig. 9 Multimeter voltage reading
g.
In steady state, when the sensors are at equal temperatures the ventilator don’t run. The value
“0.28” in the multimeter signifies that the temperature in the room is 28°C. The value “0.00”
in the multimeter signifies that the temperature difference is zero.

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6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep Dec (2012) © IAEME
Sep-

Fig. 10 shows temperature difference of 10°C between the two sensors.
Now one of the sensor is heated using a lighter, the value “0.42” in multimeter in second
figure indicates that the temperature of heated sensor reached 42°C.We can see that
reached
ventilators is running in this situation (figure 7). The value “0.10” in multimeter in the fourth
figure shows that there is a temperature difference of 10°C between the two sensors.
After reaching a steady state, the temperature is back to normal and the ventilator slows
down with drop in temperature and eventually stops without any external on/off switch.
The following table indicates the variation of voltage and current with heat flux. The below
data represents the voltage and current produced by solar panel of following specifications.

Table 3 Readings for calculating output power
The above data represents the voltage and current produced by solar panel of following
specifications.

Maximum power 10W
Maximum power voltage (V) 17 V
Open circuit voltage (V) 21
Maximum power current (A) 0.59 Amps
Short circuit current 0.62 Amps
Max system voltageage 1000V

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7.8

Pyranometer reading (No.)
7.6
7.4
7.2
7
6.8
6.6
19.23 18.97 19.25 19.2
Voltage produced (V)

Fig 11 Graph for pyranometer reading
IX. CALCULATIONS
In the first part of the circuit, the temperature sensors provide a voltage governed by the
equation

Vo = (temperature in °Celsius)/100 Volts

These voltage levels from the two sensors are subtracted in the next stage by a differential
amplifier circuit. The output voltage of differential amplifier is governed by

Vo= (-Rf/R1)*(V1-V2) Volts

Vo - Output from differential amplifier
V1, V2 - Voltages from sensors one and two
Rf, R1 - Resistors as mentioned in above simulation

This output voltage is given as input to the VCVS. The behavior of VCVS are governed by
the equation
R3/ (R2+R3) = V*Cmax/Vo

The values of resistors and the output ranges are given below
Rf = 1k
R1 = 1k
R3 = 10
R2 = 560

Final output varies from 2V to 11V depending on the input temperature difference.
X. CONCLUSIONS
The interior of the car gets heated up when parked in sun. This is harmful for both living
and non-living things present inside the car. This project is an effort to bring down this heat
by providing proper ventilation considering the draining effects of the car battery. A smart
system to ventilate the car is designed and relevant prototype is implemented. This system
consists of a ventilators placed at optimum positions and run with optimum power which
depends on the temperature. A hybrid system which has a combination of both thermoelectric
generators (TEG) and solar panel can be implemented as a source. The ventilation system can

481


be further improved by having ventilators which can rotate. They can recharge the battery of
the car as well as power electronics of the car.
However its demerits include added expenses to the car. Purchasing and installing solar
panel and a TEG would be expensive and add to the expense of the car. It will also
complicate the electronics of the car. If the system fails only a trained technician would be
able to repair the fault. Added weight will complicate the vehicle dynamics as well as the
ergonomics of the car.
Multiple units of the implemented prototype can be fitted inside the car to provide
ventilation effectively. According to our estimations 5-6 units of these prototypes can bring
equal temperatures inside and outside the car, within 20 minutes. The output seems
satisfactory and reasonable. If it was economically possible, the energy from waste heat of
the car would have been harvested. It is known that around 40% of energy from fossil fuels is
wasted as heat in the exhaust gases. Even though solar energy is harvested effectively, waste
heat recovery must also be considered, as this energy would go waste if not made use of. If
thermoelectric generators are used the hot side temperature can be maintained by exhaust gas
from muffler and cold side temperature can be maintained by radiator cooling system. The
combined system, we call it as hybrid system in modern vehicles can save fuel usage up to
10%. Not only in automobiles, it can also be used in sailing ships which can save tons of fuel
and preserve the oil/coal reserves. The only problem with it is, to get considerable amount of
power, investment should be higher and proper care should be taken for maintenance of TEG
setup. Further research has to be made to overcome these problems, we can expect good
boom for this. Anyways, considering the smart ventilation in automobiles, this has
remarkable advantages.
ACKNOWLEDGEMENT

We are deeply grateful to our advisor Dr E.Porpatam (SMBS-school), for his guidance,
patience and support. We would like to thank our friends K.Vivek Shankar, B.Srinivas,
L.Sree Harsha and committee members- Prof. Ram Mohan (TIFAC-school) and Prof. C.
Ramesh Kumar (SMBS-school), for taking their precious time to consider our work. We
consider ourselves very fortunate for being able to work with very considerate and
encouraging people like them.

REFERENCES
[1] Goswami, Kreith and Kreider. Principles of Solar Energy. Taylor & Francis. Second
Edition. 2000.
[2] K. David Huang, Sheng-Chung Tzeng, Wei-Ping Ma, Ming-Fung Wu, in : Intelligent
solar-powered automobile-ventilation system , Applied Energy Elsevier Vol. 141–154
(2005)
[3] R. Saidur, H. H. Masjuki and M. Hasanuzzaman in : Performance of an improved solar
car ventilator, International Journal of Mechanical and Materials Engineering (IJMME),
Vol. 4 (2009), No. 1, 24 -34.
[4] K. David Huang , Sheng-Chung Tzeng , Wei-Ping Ma ,Ming-Fung Wu “Intelligent
solar-powered automobile-ventilation system,” in Applied Energy 80 (2005) 141–154
[5] “Vehicle auxiliary power applications for solar cells”,I.F. Garner Solems S.A., France.
[6] http:// www.stego.de an internet open source

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