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Photovoltaic Technology

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by

Jaya Sujeewon

on 24 March 2014

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Transcript of Photovoltaic Technology


A photovoltaic cell, also known as
a solar cell is one which converts light energy to electricity.
USES OF SOLAR CELL
The Photovoltaic
Technology
Rudhi Cantiah & Jaya Sujeewon
Photovoltaic Technology
What is a photovoltaic cell?
How does it work?

MONO CRYSTALLINE SILICON
POLY CRYSTALLINE
SILICON
AMORPHOUS
SILICON
Monocrystalline
Is made up from pure silicon, arranged in regular formation.
Polycrystalline
Made up from many
crystals
Thin Films
WAVELENGTH OF LIGHT
Eph < EG
Eph = EG
Eph > EG
No separation of electron-hole pair
Efficiently absorbed to create electron hole pair
Creation of electron-hole pair while excess energy dissipated as heat loss
Initial energy of photon = Eph
Electrical Resistance
Amorphous Silicon
Non Crystalline form of silicon
Recombination
Temperature
Reflection
30% of the energy incident on the surface of the solar panel is reflected
To
increase the efficiency
it is desired that
the light is not reflected
as far as possible before it reaches the absorber layer.
 Use of anti-reflective coating (ARC)
Textured surface for reduced reflection
Electrical contact is a bridge between the load and semiconductor material.
To collect most current, maximum front contacts need to be made using grid of metal strip

Shade is a problem that is also caused by
growing trees or a neighbouring
building itself

Harm the array of photovoltaic by
damaging the layering of cells
and/or wirings.

Not hazardous to the environment
Cheaper than C-Si Mono
Lifetime of around 20 to 25 years
Lower efficiency than C-Si Mono
More Efficient than other Silicon cells
Not hazardous to the environment
Lifetime of 20-25 years
Complex Manufacturing Process
Very Costly
Light
Cheaper than crystalline-Si
Flexible
Can be integrated in buildings
Less efficient
More space needed
Causes of Pollution : Dust, Soot, Stone crushers, exhaust from combustion cars, birds poop
Increase shade level
This problem can be overcome by a regular cleaning of the arrays.
Clearing of the bushes
or branches can get rid
of shade from trees or
re-positioning of the
arrays can be done.

Trade-off between input and output power

Also the use of electrical contact causes an increase in temperature.
FACTORS AFFECTING
THE EFFICIENCY OF
SOLAR CELLS
ADVANTAGES OF USING SOLAR CELLS
TO PRODUCE ELECTRICITY IN MAURITIUS
SOLAR ENERGY IS RENEWABLE AND FREE!!!!!!!
DOES NOT CAUSE AS MUCH POLLUTION AS FOSSIL FUELS! ^_^
IT IS A VERSATILE SOURCE OF ENERGY
LITTLE MAINTENANCE IS REQUIRED.
ALLOWS PEOPLE WHO LIVE IN REMOTE AREA TO PRODUCE ELECTRICITY
LAST BUT NOT LEAST.....
MORE USES OF SOLAR PANELS
IN MAURITIUS WILL INCREASE JOB
OPPORTUNITIES...
FOR US!!!!!!!!
DISADVANTAGES...
BACKUP ENERGY SOURCES MUST BE USED AT NIGHT.
ONLY FEW CAN AFFORD IT.
MAJORITY OF PANELS ARE ONLY 22% EFFICIENT.
valence band
STORING THE CAPTURED ENERGY HAS NOT YET REACHED ITS OPTIMUM POTENTIAL
stabilizes in
Process during which

meta-stable state electron
in the conduction band
lower energy band

that is the

empty

valence band

and

removes (recombines with) a hole
RESULT:
electron loses energy
The Nominal Operating Cell temperature, NOCT







temperature coefficient, y

Actual operating temperature, T





o
o
Power loss = y . ( T - 25 C)
Normal operating temperature = 25 C
IMPROVING
EFFICIENCY...
USING MULTIJUNCTION CELLS
Since different band gaps are present in the cell, photons
with different energy can be absorbed, thus proving to be more efficient.
Concentrated solar cells
This construction, as the name suggests, concentrates direct light, (limiting it to clear and sunny weather however tracking systems can be used) towards the solar cells giving several advantages.


Branches sequence to increase efficiency (Fibonacci)
Branches and leaves grow in way to maximise the amount of sunlight (photosynthesis)
Same principle to construct the order of solar panels
Branch and spirals - Fibonacci fraction
Spiral Pattern
Sound vibrations to increase efficiency of solar cells
music - pop and rock
high frequencies & pitch
zinc oxide nanorods
increases device efficiency by
75 decibels of sound
best at frequencies ~10 kHz
vibrations - strain - voltage
40%
FEASIBILITY STUDY
Description of Mauritius
Area 1870 Km
Located latitude 20 South and longitude 58 East
10.4 hours < < 13.9 hours
0
0
2
solar disc visibility
Total Reflected Energy: 49%
Absorbed Energy by Earth's surface: 51%
Factors considerable for measurement of solar power:

Solar irradiance
Power incident per unit area

Solar radiation (Insolation)
Power incident per unit area within a given time

Sky clearness index
light attenuation by atmosphere within a given time

4 KWh/ m daily< potential average < 7 KWh/ m daily
annual solar radiation
According to research in Mauritius
monthly peak irradiance of 1198 W/ m
Average monthly insolation
Insolation
KWh/m
2
Months
2
2
2
Incident sunlight in Mauritius also depends on:
Cloud cover - for 2013
cloudier and clearer during August and November respectively
median
cloud cover
is 54% to 69%
NOTE: All prices are in rupees (Rs)
Prices depending on Power generation per hour
Lawrence Berkeley National Laboratory (short: LBNL)
Solar Energy Industries Association (short: SEIA)
Studies on average PV system Prices
Mauritius
Excess of energy production?
Use Grid-Tied system!
Electricity utility in Mauritius - CEB
Small Scale Distributed Generation (SSDG)

Medium scale Distributed Generation (MSDG)
Small Scale Distributed Generation (SSDG)
low voltage, Capacity < 50 KW

2 MW available today
Now to public institutions, schools, religious and charitable institutes as well
By 2011, 2.54MW already allocated
residential, industrial & commercial
900 KW for Rodrigues
100 KW for Mauritius
In 2012
Another
1 MW
available
Household Type A
180 kWh
(Having appliances marked with an asterisk in table)


Household Type B
450 kWh
(Having all appliances in Table)

MEDIUM SCALE DISTRIBUTED GENERATION (MSDG)
For large voltage (22 KV)
Grid Code1
50 KW < Capacity < 200 KW


Grid Code 2
200 KW < Capacity < 2 MW
The selling tariff is determined depending on grid type
Payback Time and Return
on Investment
What is the payback time?

And if Grid-tied system is
implemented, what is the return on investment?
Initial electricity rate
Average yearly increase in grid-electricity rate
Decline in efficiency of the solar panel
Cost per peak kilowatt to install
Loan interest rate
Actual panel power output for full sunshine
Average sunshine hours per day for a year
Further investment for maintenance such as for batteries, inverters, solar grid

Payback Time and Return on Investment
Calculating payback time for Household A
Rating of chosen system: 2KW/Hour
Investment: Rs 340,000
Average insolation per day: 6 hours

household uses about 180 KWh per month,
So, for 6 hours, Power output = 6 x 2 KWh /day
Power output= 12 x 30 KWh / month
Laboratory test gives 27% efficiency for a rating of 2KWH
In real environment, efficiency is 18 %
hence,
Power Output =360 x (18/27) KWh = 240 KWh

60 KWh left
~
and according to CEB buying rates and KWh, only 50 KWh is allowed (SSDG)

Remaining Energy ( 60 - 50 ) KWh can be stored in battery


Calculating payback time for Household A
Initial investment = Rs 340,000
Saving = Rs 20,172 / year
Payback time = Intial investment / saving per year
= 16.85 years
Payback time =17 years approximately

The calculations were done while considering fixed utility rate per months which is not the case estimated 5% of tariffs increase per year
Assumptions: decline of PV system is 0.5% on average
Assuming maintenance cost of Rs 105,000
(inverter lifetime = 10 years)

Payback time < 22 years

Implementation in
Mauritius is indeed
feasible :D
This is the end of the presentation
on photovoltaic technology!

We thank you for your attention!
by
However this covers the surface through which light enters before being absorbed by the cells
Affected by critters and
rodents
SAVES =Rs ( 931 + [ 50 x 15 ] ) /month = Rs 20,172/ year
Bandgap threshold energy level, EG
Different layers which can absorb different wavelength of light can be used
The pyramid formed layer, reflects the light incident on it until it is absorbed
Fibonacci fraction 2/5 - ratio of spirals to branches
Example:
NOCT = 40 C
maximum temperature coefficient = 0.5%/ C


Power Loss on temperature = ( 0.5% x (40 C - 25 C))
Power Loss = 7.5 % approx

Decreasing NOCT to approx 25 C
Or using PV with lower temperature coefficient
~ reduces Power Loss
0
0
0
0
0

conduction band
before the electron is able to contribute to cell's current in the electrical circuit
Full transcript