NANO SCIENCE IN SOLAR ENERGY
1.INTRODUCTION
The growing energy demand and the depletion of conventional energy sources along with global
warming threats has motivated researchers to design the most efficient photovoltaic (PV) cells. A PV
cell that used sunlight to generate clean electric power was first designed and fabricated by Bell
Laboratories in 1955 . Over the last five decades, numerous studies have reported the notable progress
in PV cells design and performance for terrestrial applications . Several pioneering research and
development have been conducted on crystalline silicon cells, amorphous silicon cells, CIGS (copper-in
diumgallium- diselenide) solar cells and other compound solar cells, and dye-sensitized solar cells.
Crystalline silicon cells, having a conversion efficiency of over 20 % over a small area, dominate the
recent trend of PV cell market. However, a solar cell module with crystalline silicon is expensive. In
order to reduce the production cost, research is being performed to develop thin-film solar cells with a
thickness of under 100 _ m at low temperature. On the other hand, amorphous silicon cells with a
thickness of a few micrometers are inexpensive and can be used for mass production. But their
efficiency is relatively low. Further investigation is continuing for developing microcrystalline silicon
cells with laminated structures to improve cell efficiency. Whereas, CIGS solar cells have a potential to
obtain cell efficiencies near 20 % over a small cell area, the efficiency drops sharply over a large area.
Dye-sensitized solar cells are relatively inexpensive.
In the last few years, extensive research has been conducted to reach cell efficiencies over 10 %
over a small cell area.
This paper reviews the remarkable performance of traditional PV cells and outlines the possible
areas for further investigation. Use of nanotechnology in hybrid solar cell design could further improve
the performance and reduce the cost of PV cells and modules. Basic principles, mechanisms and
challenges within three key areas of nano technology have been discussed from a clean energy
perspective.
1.1 ENERGY CHALLENGES
In today’s economy, reliable, efficient, pollution free, abundant energy requirement is the major
challenge. Our major economy needs, in terms of energy comprises of transportation sector, residential
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and commercial sector. We are heavily depending on the non-renewable sources for our energy needs.
Not only these resources will deplete over time, they are also the major source of pollution, which is
another issues in front of the economy. To face these challenges there’s needed to come up with the
new technology that helps in reducing the problems and also improves our economy.
1.2 LIST OF CONVENTIONAL ENERGY RESOURCES
The tabulation below shows various conventional energy resources. Source of energy demands,
reasons for its decline.
FORMATION
REASON FOR DECLINE
Formed from decayed swamp plant
Drives turbine to generate electricity.
matter that cannot decompose in the low
Fire cement and lime kills.
oxygen.

Steam engines.

Extracting iron.

Cooking.
Formed by decaying under pressure of
billons
of
microscopic
plants
in
Transportation has increased.
Used in lubricant, plastics, and fertilizers.
sedimentary rocks.
Formed by converting organic material
into natural gas due to high pressure.
Generation
of
power
gravitational flow of water.
using

the
Mostly in power generation.
Previously, burning it of often wasted it.
Irrigation.

Domestic purpose.

Industry.
This is fission of uranium to produce
Waste disposal.
energy. Heat is used to boil water and
High cost.
activates steam turbines.
1.3 NEED FOR NON-CONVENTIAL ENERGY
RESOURCES
As from the above table it is clear that the conventional energy resource is decaying as the day’s
passes.
In order to have a substitute for this conventional energy we supplement it with non-
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conventional energy. Non-conventional energy are of various forms such as solar, wind, biomass etc,
which exist in nature until the earth life period. In order to use such non-conventional energy in an
effective manner various technical processes are being developed.
1.4 THREE GENERATIONS OF SOLAR PANELS
/3 1
Photovoltaic technology has been categorized into three distinct generations, which mark step shifts in
the materials and manufacturing techniques used to make the cells.
The first generation of solar cells uses very high quality crystalline silicon. These are expensive to
manufacture, and have a fairly low theoretical efficiency limit of around 33%. Second generation PV
cells use thin film technologies with other semiconducting materials such as cadmium telluride (CdTe)
and copper indium gallium selenide (CIGS). These materials can significantly reduce processing costs,
and promise much higher theoretical efficiencies than silicon-based PV materials. Third generation PV
is a much broader group of technologies, all of which are emerging or in the development phases.
Technologies often considered part of this third generation include quantum dots, nanostructured
semiconductors, and amorphous silicon.
1.5 TRADITIONAL PV CELLS
Extensive research has been performed with crystalline, nanocrystalline, multicrystalline, thinfilm polycrystalline, and amorphous solar cells to maximize cell efficiency as well as to reduce
material size and cost. The concept of crystalline silicon thin-film solar cells of thickness fewer than
50nm reduces silicon material consumption significantly and has potential to reach high efficiencies
comparable to silicon wafer. The reducing thickness of a solar cell results in an increase open-circuit
voltage. However, the crystalline silicon technology has had the growing demand depending upon cell
performance and costs compared to the other forms . On the other hand, solar cell efficiency has also
been improved by developing multi junction devices as tuned to collect light at a certain wavelength,
which converts varying wavelengths of sunlight into electricity. Stacks of exotic semiconductor
materials composed of gallium, indium, phosphorous, germanium, and arsenic have been
used to develop multilayered systems. However, the costs of these semiconductor materials increase
solar cell module cost significantly than that of silicon.
PV cells convert sunlight directly into electricity without creating any air or water pollution.
PV cells are made of at least two layers of semiconductor material. One layer has a positive charge,
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the other negative. When light enters the cell, some of the photons from the light are absorbed by the
semiconductor atoms, freeing electrons from the cell’s negative layer to flow through an external
circuit and back into the positive layer. This flow of electrons produces electric current. To increase
their utility, dozens of individual PV cells are interconnected together in a sealed, weatherproof
package called a module. When two modules are wired together in series, their voltage is doubled
while the current stays constant. When two modules are wired in parallel, their current is doubled
while the voltage stays constant. To achieve the desired voltage and current, modules are wired in
series and parallel into what is called a PV array. The flexibility of the modular PV system allows
designers to create solar power systems that can meet a wide variety of electrical needs, no matter
how large or small.
1.6 SCIENCE OF SILICON PV CELLS
Scientific base for solar PV electric power generation is solid-state physics
of semiconductors. Silicon is a popular candidate material for solar PV cells because

It is a semiconductor material.

Technology is well developed to make silicon to be positive (+ve)
or negative (-ve) charge-carriers – essential elements for an
electric cell or battery

Silicon is abundant in supply and relatively inexpensive in production

Micro- and nano-technologies have enhanced the opto-electricity
conversion efficiency of silicon solar PV cells
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Fig 1:
A. Thin-Film Solar Cells
Thin film CIGS technology is very promising for achieving high efficiency at economic price. An ink
based non-vacuum process is used to fabricate CIGS solar cells both on rigid and flexible substrates. An
aqueous precursor metal-oxide suspension made from nanoparticles of Cu, Ia, and Ga oxides is coated
onto a Mo foil or a non-conducting substrate, improving cell efficiency to 8.9 % on polyimide, 13.0 %
on Mo foil, and
13.6 % on glass substrate . The recorded efficiency of ZnO / CdS / CuInGaSe2 thinfilm solar cells with
preferred orientation and absorber materials is 19.2% dueto higher open-circuit photovoltage (Voc) and
short-circuit photocurrent density (Jsc) . The performance of a thin film single junction GaAs solar cell
is improved with a gold mirror back contact, which reflects 90% of the high wavelength photons and
serves as low ohmic back contact and also reduces the thickness to half that of the regular
GaAs cell film thickness with reported cell efficiency of 24.5% AM1.5G .
B. Mono- Or Multi -Crystalline Silicon Solar Cells
Sun Power reported three wafer properties – lifetime, thickness, and resistivity to offer a
competitive price for a rear-contact solar cell with at least 20 % efficiency. The wide tolerance on wafer
thickness and resistivity helps to make the best use of silicon from an ingot, thereby lowering the wafer
cost as well as the cost of production . The production of crystalline solar cells has moved from monoDept of EEE, SR Engineering College, Warangal
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Si to multicrystalline-Si to diminish crystallographic defects as well as metal impurities. The buried
contact solar cell (BCSC) technology is used for solar cell metallization to improve efficiency to 17.6%
for multicrystalline silicon solar cells for a cell area of 144 cm 2 . The laser grooved buried grid
(LGBG) solar cell process has become well established method for mass production of high efficiency
monocrystalline solar cells from a base line efficiency of 16.2 % to 20 % due to small area cell with
LGBG contacts . Stacks of amorphous silicon and silicon oxide, deposited by PECVD (plasmaenhanced chemical vapor deposited), are used to passivate crystalline silicon solar cells’ surface, which
boosted cell efficiency to 21.7 % on ptype (Boron doped) float zone silicon substrates for a cell area of
4.0 cm 2 with a thickness of 250
m.
C. Dye-Sensitized Solar Cells
In the past, much attention has also been paid for the development of dye-sensitized solar cells
(DSCs) in order to reduce solar cell production cost. A DSC comprises a nanocrystalline TiO2
modified with a dye fabricated on transparent conducting oxide, a platinum counter electrode, and an
electrolyte solution with a dissolved iodide ion/ tri iodide ion redox couple between the electrodes. The
improvement of dye-sensitized solar cell performance was investigated by controlling thickness and
haze factor of TiO2 electrodes without loss of open circuit voltage. The reported efficiencies for
aperture area
of 1.004 cm 2 and 0.2227 cm 2 are 10.4 % and 10.8 %, respectively . A 15-
m TiO2 (23 nm)
nanocrystalline electrode coated with 1 wt % CaCO3 increased both opencircuit photovoltage (Voc)
and short-circuit photocurrent (Jsc) remarkably and produced cell efficiency of 10.2 % using an
antireflective film on the cell surface . However, for practical application, a DSC module with size 50
mm x 50 mm for aperture area 26.5 cm 2 has achieved cell efficiency of 6.32 % .
1.7 EMERGING TECHNOLOGY
To conserve and establish the new renewable sources, many countries are trying hard to develop
new projects and harness the new renewable forms of energy. These countries are trying to trap the
energy from relatively unexplored sectors. Nano-materials and hydrogen fuel cells have the advantage
of being smaller and portable. Therefore they have many more applications.
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1.8 THE ROLE OF NANO TECHNOLOGY
Nanotechnology can help with design and manufacture second generation, thin film PV cells.
However,
Nano materials will truly come into their own in the third generation of solar cell
technologies, where novel technologies like nanowires, quantum dots and radial junctions will begin to
push the upper limits of PV efficiency. Nanostructures can also allow efficient solar cells to be made
from cheaper, more conventional materials, like silicon and titanium dioxide. Although there will be
cost barriers involved in developing mass production techniques for nano-enhanced PV cells, the use of
cheaper raw materials will allow the cost of commercial solar cells to continue to decrease.
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2. NANO-MATERIALS
There is an active research and development of nano-technology, nano-material, which are of size
of a 10-9 meter, offer different chemical and physical properties from the same materials in their normal
form. They can be adaptive to new technologies and have the potential use in making more efficient
solar cells and catalysts that can be used in hydrogen-powered fuel cells.
Due to small size and excellent conductivity, CNT’S (carbon nano-tubes), can possibly be used
as base resource of future electronic devices. CNT cables could be used to make electricity transmission
lines, which will give us, large performance improvement over present day power lines.
2.1 INTRODUCTOIN TO SOLAR-ENERGY
Solar energy is an enigma of its own. Based on the current costs of producing solar panels and the
rate at which these costs have been dropping, it is evident that solar power would become a major
source of power in projection of future energy sources. If the current projections based on the NREL
model are correct, solar power could soon be a very competitive source of energy while addressing the
problem of producing power without generating carbon dioxide and other effluents. It would not be
subject to any kind of risk. It is impossible to embargo the sun. The budget for solar research is around
seventy million dollars in the west, and most forecast of source of energy in future give solar a minor
role.
2.2 NANOTECH SOLAR CELLS
In order to improve the conversion efficiency, the major research in third-generation PV cells is directed
towards absorbing more sunlight using nanotechnology, for example ‘nanotubes’, ‘quantum dots
(QDs)’, and ‘hot carrier’ solar cells. However, implementation of these nanotechnologies in the cell
design is a real challenge.
A. Nanotubes
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Carbon nanotubes are molecular-scale tubes, consisting of a hexagonal lattice carbon with remarkable
mechanical and electronic properties. The structure of ananotube can be represented by a vector, (nrow, mcolumn), which defines how thegraphene (graphene is an individual graphite layer) sheet is
rolled-up . Nanotubes can be either metallic or semiconducting depending on their structures. Thereare
two types of nanotubes, the singlewalled carbon nanotubes (SWNTs) and the multi-walled carbon
nanotubes (MWNTs). SWNTs consist of a single graphite sheet wrapped into a cylindrical tube and
MWNTs comprise an array of concentric cylinders In PV cells technology, the nanometer-scale tubes,
coated by the special p-type and n-type semiconductor (p/n) junction materials can be used to generate
electrical current, which would increase
the surface area available to produce electricity.In recent years, nanotubes are used as the transparent
electrode for efficient, flexible polymer-solar cells. In order to improve efficiency and reduce cost, a
molecular dispersed heterojunction solar cell, consisting of a poly (3-octylthiophene) (i.e.,P3OT) and
dye (naphthalocyanine, i.e.,NaPc) coated single-walled carbon nanotubes blend sandwiched between
electrodes (aluminum and indium tin oxide (ITO) glass) was fabricated. The dye (NaPc) acts as the
sensitizer, which transforms electrons to the nanotubes and holes to the polymer as shown in . The
nanotubes provide high field at the polymer/ tube interfaces for exciton dissociation. With the NaPc
dye-sensitized nanotubes, the absorbance of the active layer in ultra-violet and red regions is
significantly increased, resulting in much higher short circuit current . However, the open
circuit voltage of the sensitized device is reduced by 0.2 V than the non-sensitized one. The electrical
properties such as conductivity of SWNTs, embedded in P3OT matrix, were measured as a function of
the SWNT concentration. With the increase in nanotube concentration from 0 to 20 wt %, the
conductivity of the resulting film increases by six orders of magnitude due to the introduction of
conducting paths to the polymer. The behavior of conductivity as a function of doping is characteristic
of percolation, with a threshold of approximately 4 wt % for pure SWNTs, whereas for arc prepared
single walled nanotubes (ASWNTs), it rises to 11 wt % .
To improve further, researchers at Indian Association for the Cultivation of Science have
introduced functionalized \multi-walled carbon nanotubes (MWNTs) in poly (3-hexylthiophene)
(i.e.,P3HT) / buckministerfullerence (C60), donor/ acceptor-type photo voltaic devices. The nanotubes
in polymer-CNT composites provide percolating channels for hole transport to the electrode. The C60
layer acts as both electron acceptor and electron transporting layer to increase the mobility for carrier
transport. The devices were fabricated on indium tin oxide (ITO) coated glass substrate and on top of
C60 layer, aluminum (Al) was vacuum evaporated. Both open-circuit voltage and short circuit current
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have increased in the polymer-CNT / C60 devices as compared to it. In a separate study, MWNTs were
shown to generate photocurrent with an efficiency of ~ 7 % .
Researchers at Pennsylvania State University have fabricated highly ordered nanotube arrays of
46-nm pore diameter, 17-nm wall thickness, and 360-nm length, by
sputtering 500 nm-thick titanium films onto fluorinedoped tin oxide-coated glasssubstrates . The
ordered arrays of titania nanotubes are used in place of titania nanoparticles in dye-sensitized solar cells
as they have remarkable charge transfer and photo-catalytic properties, resulting higher
photoconversion efficiencies. The reported photocurrent efficiency for an active area of 0.25 sq. cm is
of 2.9 % with a photocurrent density of 7.87 mA/ sq. cm, which is five times higher than the
nanoparticulate titania typically used in dye-sensitized cells. Based on outstanding results, it has been
expected
that an ideal limit of ~ 31% photoconversion efficiency may be achieved for a single photosystem
scheme with an increase in nanotube-array length to several micrometers Researchers at Pennsylvania
State University have fabricated highly ordered nanotube arrays of 46-nm pore diameter, 17-nm wall
thickness, and 360-nm length, by sputtering 500 nm-thick titanium films onto fluorinedoped tin oxidecoated glass substrates . The ordered arrays of titania nanotubes are used in place of titania nano
particles in dye-sensitized solar cells as they have remarkable charge transfer and photo-catalytic
properties, resulting higher photoconversion efficiencies. The reported photocurrent efficiency for an
active area of 0.25 sq. cm is of 2.9 % with a photocurrent density of 7.87
mA/ sq. cm, which is five times higher than the nanoparticulate titania typically used in dye-sensitized
cells. Based on outstanding results, it has been expected that an ideal limit of ~ 31% photoconversion
efficiency may be achieved for a single photosystem scheme with an increase in nanotube-array length
to several micrometers
B. Quantam Dots
Quantum dots (QDs) are semi-conducting crystals of nanometer dimensions, molded into a
variety of different forms with a tunable bandgap of energy levels that behave as a special class of
semiconductors composed of periodic groups of II-VI, III-V, or IV-VI
materials. The larger dots will absorb or emit the longer wave length of the solar spectrum. A solar cell
with the greater bandgap of semiconductor absorbs more energetic
photons causing the greater output voltage. On the other hand, a cell with the lower bandgap captures
more photons including those in the red end of the solar spectrum, resulting in a higher output current
and lower output voltage.
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2.3 ECONOMICS OF SOLAR
One of the problems with evaluating the economics of solar cells is that many analysts base their
analyses on dollar per peak watt. In terms of economics of capital investment, this is not very useful
manner to evaluate the economics of solar power.
Solar energy has two major cost components. The cost of the solar panels and the cost of system
balance per square meter. Denote these two costs by Cp and Cb. The other key parameters are the
efficiency of the solar panel that we will denote as ; the number of KW-hours per square meter per
year that are delivered by the sun at the location of the installation ; the rate at which the efficiency of
the panel degrades , and the economic life of the project T. The cost of solar power for project c is
T
Cp+ Cb=
 e  r   cdt ----- eq. (1)
0
T
Cp+ Cb=
 c1/ 1  r )1   
t
------eq (2)
t 1
The term e t  or the term  1 / 1    is the amount of electricity produced at time t and
t
e  rt c or term c1 / 1  r  is the present value of the electricity produced at time t. The cost of solar
t
power is that stream of income whose present value will cover the capital costs. Note that this does not
include such elements as profits or cost of transmission. If we solve equation 1 we get

C= Cp  Cbr    /  1  e r   
T

 --------eq (3)
If we examine eq (3) we see that cost per peak watt. (Cp/), is not an adequate measure of the cost
of solar power. That measure only considers the cost per square of the solar panels, Cp and the
efficiency. It ignores some very important variable such as the amount solar energy at a particular
location, the interest rate, and the cost of the balance of systems.
Other important variables are the interest rates. If the project has an infinite life, the cost of solar
power would be liner with the interest rate. Let c( r) be the cost as a function of the interest rate. The
graph below shows the ratio ( r)=(c( r)/c ( 0.5) for =0 and T=20. This is the measure of how much the
interest rate increases the cost of solar power for a period of 20 years.
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FIGURE 1
3
2.5
2
1.5
Series1
1
0.5
0
0
5
10
15
20
25
INTEREST(PERCENTAGE)
Fig 2:
, we plot the costs of solar powering using Zweibel’s cost $85.00 at a production volume of 250,000
square meters per years as a function of interest rate. We will assume that the solar panels are 9.5 %
(=0.095), that the sun delivers 2500 KW-hours per year (=2500), the panels degrades at a rate of 1%
(=0.01), and the project life is 20 years (T=20). The cost of the balance of system is assumed to be 35
dollars per square meter.
COST OF SOLAR POWER
12
10
8
6
Series1
4
2
0
0
5
10
15
20
25
INTEREST RATE(percentage)
Fig 3:
If we examine fig 3, we see that if the discount rate used is between 5 to 8%, the cost of solar power
runs between 4.5 to 5.5 cents per KW-hours to grid. This is competitive with combined cycle gas plants
at a price of gas in the neighborhood of $5 per thousand cubic feet. However, if a rate of return on the
project of 12 to 16% is required, the cost of power goes up to 7 to 9 cents KW-hours. At that price, solar
power is not competitive with combined cycle generation with natural gas as a feedback fuel when the
price of natural gas is in the neighborhood of $5 per thousand cubic feet.
Which is the correct value for the discount rate? Why would the private sector not invest in projects
when the rate of return is higher than the cost of capital? At first glance, this seems a paradox. Why
would firms pass up projects whose rate of return is greater than their cost of capital? The answer may
be that capital is only one of the inputs of firm. There may be other inputs, some of which are not
tradable, which results in firm requiring a higher rate of return than the cost of capital. Thus, solar
power may be a viable technology if one just considers the opportunity cost of the resources involved as
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measured by the interest rate. However, with current technology, solar power is not sufficiently
profitable for the private sector to make substantial investment in it.
A related problem is that of economic of scale. The marginal cost of producing solar panels is on
the order of $30 to $50 a square meter. A study by Zweibel and a model based on data furnished to the
authors by first solar suggest that costs in the neighborhood of $85 per square meter are possible with
current technology. However, to achieve such costs, it would be necessary to have a plant volume of
production of the order 250,000 square meters per year to achieve the necessary economics of scale.
This is 25 million peak watts. The U.S market for solar panels last year was 125 Mwp. Thus, at the
present time, the volumes necessary to achieve the economics of scale that are needed for solar power to
be competitive in supplying power to be the net can be sustained only if there is a demand from such
large projects as solar fields. But developing demand in that order of magnitude would require a drop in
solar cell costs, creating a chicken-egg problem for the technology.
Solving this dilemma will require leadership and entrepreneurship that is not likely to be
forthcoming from the private sector. The private sector is driven by a short-term profit motive and at the
present time, there are more attractive, immediate opportunities than solar power.
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3. NANO-TECHNOLOGY FOR SOLAR ENERGY APPLICATION
3.1 Solar Collector and Nano-Technology:
Solar technology has been struck for decades, with only minor incremental improvement in siliconbased solar cells, never achieving more than 30% efficiency ratio for converting sunlight to electricity.
However, this malaise in solar technology appears to be coming to an end, due to advancements in
nano-technology (building structure on the molecular level).
Fig 4:
Recent nano-technology break through in regards to solar have promised new solar cell design
capable of capturing a much wider range of solar energy, which would be much more efficient at
converting solar energy to electricity (approaching 60% efficiency), more versatile (able to be painted
onto just about any surface), and less costly than today’s solar technology. These nano-technology
advancements in solar energy technology appear to be finally advancing solar beyond its initial siliconbased.
 Nano-Technology plus plastic electronics: Solar Cells
A new generation of solar cells that combines nano-technology with plastic electronics has been
launched with the development of semiconductor-polymer photovoltaic devices by researchers with the
U.S. Department of energy’s Lawrence Berkeley National Laboratory (Berkeley lab) and the University
of California at Berkeley (UCB). Such hybrid solar cells will be cheaper and easier to make in the same
nearly infinite variety of shapes as pure polymers.
Thus by the use of nano-manufacturing can easily increase the effective area and thus reducing the
distance traveled by the electron-hole pair to safe.
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 Nano-Technology may give plastic solar cells a boost:
RIT researches, led by Ryne Raffaelle, professor of physics and micro system engineering and director
of the nano-power research lab, hope to develop and improve polymer solar cell using nano-material
additive. Raffaelle and his team will use a thin polymer film that can be rolled out in sheets. The film
will contain nano-scale pieces of semiconductor material and single-walled carbon nano-tubes to
maximize energy conversion.
3.2 Nanostructured Silicon Solar Cells Achieve High Conversion Efficiency Without
Antireflective Coatings
The economics of solar cells always involves striking a balance between conversion efficiency and
manufacturing costs. Researchers of Energy’s National Renewable Energy Laboratory (NREL) believe
that they have struck a balance between both of these factors by developing a nanotechnology-enabled
silicon solar cell that boasts 18.2 percent conversion efficiency and that should be cheaper to produce.
According to research, (“An 18.2%-efficient black-silicon solar cell achieved through control
of carrier recombination in nanostructures”), was able to create a solar cell without the use of antireflective coatings that are typically required to reach that conversion efficiency.
The NREL team was able to achieve this high efficiency without anti-reflection coatings by making
billions of nano-sized holes in silicon. Since the holes are actually smaller than the light wavelengths
striking the silicon, there is no sudden change in the light density and the light doesn’t reflect back off
the surface of the silicon. While the NREL researchers had previously demonstrated that these
nanostructures in silicon reflected less light off the surface, this latest research was the first time they
were able to use the technique to achieve high conversion efficiency with the nanostructure silicon
cells.While attaining high energy conversion efficiencies for an individual cell—and even doing it with
a cheaper manufacturing process that eliminates the need for antireflective coating—is an achievement,
a big obstacle remains getting those individual cells into a module without significant losses in
efficiency.
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4. SCIENTIFIC RESEARCH
Fig 5:
Over fifty years, billion of dollars have been spent on fusion research. If commercially priced,
electrical power developed by fusion technology would be very inexpensive. In order to use fusion
power, it requires at least 2 technical problems to be solved.
(1) To develop a sustained fusion reaction
(2) How to convert the fusion energy into electricity.
There is, however, one source of fusion power currently available, the SUN. At the distance
between the earth and the sun, the sun delivers 1.3 KW per square meter per hour. This is 11,400 KWhours per square meter per year. Some of the loss is due to the atmosphere; only one KW per hour
reaches the earth’s surface. The rest is due to the rotation of earth. Thus, a space based solar plant has
factor of 4.5 advantages over a ground based solar plant. However, a space based solar plant can cost no
more than 4 times cost of solar plant on earth if it is to be competitive as a source of power. It is very
expensive to lift mass to orbit or moon.
One way to get around the cost of lifting solar cells is to build them on moon. Such a project has
been proposed. However, even if a process can be designed so that solar cells can be constructed at a
price that can compete with an earth-based system, there is still problem of transmitting the power to
earth. The analysis that should be made is whether transmitting power from moon to earth is a less
expensive than power transmitting from point to point on the earth as the earth turns. It seems plausible
that any technology that can transmit power from the moon to the earth can also be used to transmit
power from point to point on earth. Further, on earth, there is the possibility of developing land-based
nano-wire transmission lines as well as electricity storage based on new materials and nano-technology.
Dept of EEE, SR Engineering College, Warangal.
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Another strong advantage of an earth-based system is that it will be easier to incorporate
technical change. The NREL model of costs projects a 20% reduction in the cost of solar cells for
doubling of output of solar cells. Demand is growing at 25% a year. If we combine these two
observations we can fill the need.
The cost of the solar power as a function of the costs of solar panels as projected by the NREL
mode; We will assume that the solar panels are 9% efficient, that the sun delivers 2500 KW-hours per
year, the panel degrades at a rate of 1% a year, the interest rate is 8% and project life is 20 years. The
cost of the balance of system is assumed to be 35 dollars per square meter.
It should be noted that the NREL models does not differentiate between saving due to
economics of scale and technical progress. The 25% increases in demand is also based on historical data
and cannot take into account threshold effects where the cost of solar power drops to the point where it
becomes competitive in new markets. For example, around a price of four cents per KW-hours, largescale solar fields become very competitive at the current and projected price of electricity. When the
cost drops below 2 cents per KW-hour, solar hydrogen may be an economical alternative to natural gas
in petrochemicals.
The projected costs of electricity using the NREL model under the assumption that 9% efficient
solar panels at eighty-five dollars per meter were available. The cost starts at about 5.8 cents per KWhour and falls to about 2.6 per KW-hour over a twenty-year period.
The projection is based on current technology and therefore can be considered conservative.
Electric power in range of 2.5 to 1.9 cents per KW-hours that does not produce carbon dioxide would be
invaluable in solving the energy crisis and the problem of global warming. So we can ask why solar
power plays such a small role in future energy projections and why funding of solar research is so
small?
There are perhaps several reasons for this lack of understanding of the potential of solar power.
(1) The advocates of solar power have not done a good job in educating policy marker.
They think in terms of cost per peak-watt rather than the cost per kilowatt-hour.
(2) There is not a clear understanding of the vast potential availability of solar power.
Currently most of the investment in solar power is taking place in Europe and Japan where the sun
delivers 900 to 1200 KW-hours per year.
Dept of EEE, SR Engineering College, Warangal
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5 CONCLUSION
The conclusion obtained from the above topic is that we should increase the use of renewable
sources of energy and decrease the use of non-renewable resources. Existing renewable resources are
well established. It has been seen through the various articles that available renewable energy resources
are helping in the production of the other forms of energy, which makes our energy system more strong
and economical. Likewise the production of solar energy, from the available sunlight, and its usage is
more clean, safe and efficient. They are commercially available and are being utilized. The new
upcoming technologies in renewable resources are very promising but a lot more research and
infrastructure is required before it can be adapted.
Dept of EEE, SR Engineering College, Warangal.
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REFERENCES:
1) U.S department of Energy’s national renewable energy,
2) Ahmed.K, “Renewable energy Technologies”,
3) Cody.G and T.Tiedje, (1996),”A learning curve approach to projecting cost and
performance in thin film photovoltaic”.
4) Zweibel.K (1999) ”Issues in thin film PV manufacturing cost reduction, solar energy
materials and solar cells”.
Dept of EEE, SR Engineering College, Warangal
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