Experimental analysis of solar powered ventilation

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

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

471

EXPERIMENTAL ANALYSIS OF SOLAR POWERED VENTILATION

COUPLED WITH THERMO ELECTRIC GENERATOR ON

UNROOFED PARKED VEHICLES

Ganni Gowtham1, Ksitij Kumar

2, S.S Charan

3, K Manivannan

4

1(Vellore Institute of Technology, Vellore, India, [email protected])



4(Professor, SMBS, Vellore Institute of Technology, Vellore, India, [email protected])

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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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 (Ω).

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 = SBT-SBT dT T2

T1 (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.

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

6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep

II. PV SOLAR CELLS

The use of PV solar cell modules connected together I

enable current and voltage oriented dispo

energy generated at a DC level of 12V, 24V or 48V. PV

electricity is performed from semiconductor materials junctions that

doped surfaces where photons coming from the sun overcome

generating an electron flux. The photoelectric

Applications on standard medium size energy generation are based on

located in house roofs, buildings and

panels on the roof of small automobiles. Use of solar cells in vehicles had the goal to ful

individual requirements and comfort such as charging auxiliary batteries for air

radio, charging GPS system, mobile phones or to maintain the temperature required inside the

cabin, motor and air-conditioning for fast start. Total capacity of PV modules currently used

is approximately 165-215 Watts,

roof is a constraint, as efficiency and capacity of cells improve, nominal power will increase

greatly and their use could soon be standardized.

experiment.

III. THERMOELECTRIC

Thermoelectric generators (also called thermo generators) are devices which

(temperature differences) directly into electrical energy, using a phenomenon called the

"Seebeck effect" (or "thermoelectric effect"). Their



convert it into potential energy that can be used to power the electronics or r


efficient cars. Fig2 shows Thermo electric generator


6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME

473

ll modules connected together I arrays of parallel and se

voltage oriented dispositions that allow capturing a distribution

generated at a DC level of 12V, 24V or 48V. PV conversion of solar energy into

semiconductor materials junctions that form layers of p and n

coming from the sun overcome the photo-electronic

generating an electron flux. The photoelectric effect is the base of such conversion.

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

panels on the roof of small automobiles. Use of solar cells in vehicles had the goal to ful

individual requirements and comfort such as charging auxiliary batteries for air-

obile phones or to maintain the temperature required inside the

conditioning for fast start. Total capacity of PV modules currently used

215 Watts, [2,3] though the limited surface available on the automobile

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

Fig. 1 PV Solar Panel

THERMOELECTRIC GENERATOR

nerators (also called thermo generators) are devices which transform


"Seebeck effect" (or "thermoelectric effect"). Their probable efficiencies are around 5



convert it into potential energy that can be used to power the electronics or recharge battery


Fig2 shows Thermo electric generator


Dec (2012) © IAEME

arrays of parallel and series circuits

distribution of the

conversion of solar energy into

form layers of p and n

ectronic band-gap

is the base of such conversion.

flat solar PV panel

ted [1] the use of solar energy

panels on the roof of small automobiles. Use of solar cells in vehicles had the goal to full fill

-conditioning,

obile phones or to maintain the temperature required inside the

conditioning for fast start. Total capacity of PV modules currently used

though the limited surface available on the automobile

is a constraint, as efficiency and capacity of cells improve, nominal power will increase

used for the

transform heat


efficiencies are around 5-10%.



echarge battery




IV. DETERMINATION

A Swift VDI car is used for experimentation.

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)

Where: -

Ti - Inside cabin temperature

To - Ambient temperature

∆T - (Ti-To)

Q - Amount of heat generated inside cabin

Cp - Specific heat at constant pressure



474

Fig. 1 CAD Model of TEG

OF TEMPERATURE INSIDE A PARKED CAR

ar is used for experimentation. The following are the specifications of a car.

3760 mm

1690 mm

1530 mm

5 persons

White

Tinted glass

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

Table 1 Observations

nside cabin temperature

Ambient temperature

Amount of heat generated inside cabin

Specific heat at constant pressure

(1.005 KJ/Kg/°c)


Dec (2012) © IAEME

CAR

The following are the specifications of a car.



475

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

0

50

100

150

200

250

300

03:40 03:50 03:55 04:05 04:10 04:15 04:20

He

at

Ge

ne

rate

d (

kJ)

Time (s)



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

Air Constant

4. Calculation

Required volume flow

So, the theoretical calculations show that around 22 cfm capacity should be used in cars. it’s

safe if we use within the range of 30

ventilator with the specified capacity and operating voltage an

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

near steering and at the top of roof. To run the

go for green technology like usage of solar panels or waste heat recovery fr

So, here we can use combined system of solar panels and thermoelectric generators

to harvest energy.

Fig.

VI. IMPLEMENTATION

As already observed, we are using

and make it more efficient, it is necessary to control the power supplied to the

based on requirement. This power controller is necessary in a time like this, where our

conventional power sources are fast exh

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

shows a linear output with respect to input is chosen. The working of this circuit can

explained using a simple block diagram.



476



vel) in meters 0 to 100 meters

3.1 m3/KWh

21.17 cfm

o, the theoretical calculations show that around 22 cfm capacity should be used in cars. it’s

safe if we use within the range of 30-40cfm. There are many ventilators

with the specified capacity and operating voltage and currents range between .

of size 97x33mm (for example) can be installed as shown in the

f heat penetration through car is the tinted glass windows. So, it can be placed

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.

So, here we can use combined system of solar panels and thermoelectric generators

Fig. 4 Placement of ventilator

IMPLEMENTATION OF VENTILATION SYSTEM

As already observed, we are using ventilators to ventilate the car. To further optimize it,

and make it more efficient, it is necessary to control the power supplied to the


conventional power sources are fast exhausting. [2, 3] Moreover a car runs on a battery, i.e.


ventilator, based on the temperature difference. A circuit which

ar output with respect to input is chosen. The working of this circuit can

explained using a simple block diagram.


Dec (2012) © IAEME



o, the theoretical calculations show that around 22 cfm capacity should be used in cars. it’s

ventilators and cooling

d currents range between .7 and

of size 97x33mm (for example) can be installed as shown in the

f heat penetration through car is the tinted glass windows. So, it can be placed

, it’s better to

om exhaust gases.

So, here we can use combined system of solar panels and thermoelectric generators (TEGs)

e the car. To further optimize it,

and make it more efficient, it is necessary to control the power supplied to the ventilators,


Moreover a car runs on a battery, i.e.


, based on the temperature difference. A circuit which

ar output with respect to input is chosen. The working of this circuit can



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

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

next stage. And finally a “voltage controlled voltage source” controls the voltage to be given

out, hence controlling the power and rpm of the

Fig. 6

We considered waste heat as first alt

can be used and its characteristics can be observed.

module HT 8-12-40 and the following reading is



477

Fig. 5 Block Diagram


the car. These sensors produce a voltage which is proportional to the



emperature are equal, the output of the differential amplifier would be zero. Otherwise, the


has the ability to shift the voltage levels to required range, which is compatible as inputs for


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)

can be used and its characteristics can be observed. An experiment was conducted on TEG

and the following reading is taken. Based on the study of existing


Dec (2012) © IAEME


the car. These sensors produce a voltage which is proportional to the



emperature are equal, the output of the differential amplifier would be zero. Otherwise, the


compatible as inputs for


ernative. For this a thermo electric generator (TEG)

ducted on TEG

taken. Based on the study of existing



478

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

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.

0

0.2

0.4

0.6

0.8

1

14.17 17.38 20.89 32.27 46.92 55.65 67.11

Vo

lta

ge

(V

)

Temperature difference (°C)



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

The solar panel charge the batteries,

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 imple

on a bread board. This circuitry was able to drive two cooling ventilator

estimated to consume a power of 4W.

delivered. Below photo illustrate the real time working of the circuitry.

Fig.

In steady state, when the sensors are at equal temperatures the

“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.



479

general solar charging circuit used to charge batteries

e the batteries, which prevents draining of them. As mentioned earlier

producing a constant voltage of more than 12V, sufficient to charge the batteries.


TEGs connected in series which is highly expensive. The designed circuitry is imple

This circuitry was able to drive two cooling ventilator

estimated to consume a power of 4W. With a better MOSFET higher output power can be

illustrate the real time working of the circuitry.

g. 9 Multimeter voltage reading

In steady state, when the sensors are at equal temperatures the ventilator don’t run. The value


the temperature difference is zero.


Dec (2012) © IAEME

As mentioned earlier

producing a constant voltage of more than 12V, sufficient to charge the batteries.


TEGs connected in series which is highly expensive. The designed circuitry is implemented

This circuitry was able to drive two cooling ventilators, which are

With a better MOSFET higher output power can be

don’t run. The value




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 re

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

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.

data represents the voltage and current produced by solar panel of following specifications.

Table 3 Readings

The above data represents the voltage and current produced by solar panel of following

specifications.

Maximum power

Maximum power voltage (V) 17 V

Open circuit voltage (V)

Maximum power current (A)

Short circuit current

Max system voltage 1000V



480

temperature difference of 10°C between the two sensors.


figure indicates that the temperature of heated sensor reached 42°C.We can see that

is running in this situation (figure 7). The value “0.10” in multimeter in the fourth


After reaching a steady state, the temperature is back to normal and the ventilator


The following table indicates the variation of voltage and current with heat flux.

current produced by solar panel of following specifications.

3 Readings for calculating output power


Maximum power 10W

(V) 17 V

Open circuit voltage (V) 21

Maximum power current (A) 0.59 Amps

0.62 Amps

age 1000V


Dec (2012) © IAEME

temperature difference of 10°C between the two sensors.


ached 42°C.We can see that

is running in this situation (figure 7). The value “0.10” in multimeter in the fourth


ventilator slows


The following table indicates the variation of voltage and current with heat flux. The below

current produced by solar panel of following specifications.




481

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 = 1kΩ

R1 = 1kΩ

R3 = 10Ω

R2 = 560Ω

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

6.6

6.8

7

7.2

7.4

7.6

7.8

19.23 18.97 19.25 19.2Py

ran

om

ete

r re

ad

ing

(N

o.)

Voltage produced (V)



482

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

Documents

Experimental analysis of solar powered ventilation