Among and declining fossil fuel assets made us

          Among the of incoming solar radiation
(insolation) at the upper atmosphere, earth receives about 174 petawatts (PW)
of the incoming solar radiation. There are 174 Petawatts (PW) of
approaching sunlight based radiation (insolation) at the upper environment is
get by the earth. In this sum, in the scope of 30% is reflected back to space
while the rest is consumed by mists, seas and land masses. At the surface of
earth, range of sun oriented light is generally spread over the noticeable and
close infrared extents with a little part in the close bright.


Solar power may have had extraordinary potential,
however it was left as a second thought at whatever point fossil powers were
more reasonable and accessible. “Just in the most recent couple of decades
when developing vitality requests, expanding ecological issues and declining
fossil fuel assets made us look to option vitality alternatives have we
centered our consideration around really misusing this colossal asset.”
For example, the US Department of Energy subsidized the establishment and
testing of more than 3,000 PV frameworks amid the 1973-1974 oil ban. By the
late 1970s, vitality organizations and government offices had put resources
into the PV business, and “a gigantic speeding up in module advancement
occurred.” Solar vitality upgrades were again looked for amid the Gulf War
in the 1990s.1


            Solar electric power can be made
either by power plants using the sun’s heat or by photovoltaic (PV)
advancement, which changes over light specifically to power utilizing by using
solar energy. PV development is more helpful for private usage. Structures to
use the glow of the sun particularly can be either active or passive. In active
structures, air or liquid course through sun controlled experts and bring
warmth to where it is used. In passive systems, structures are worked with
windows and warmth engaging surfaces set up to extend sun based warming in
winter. Either innovation is appropriate for residential usages 1.


2.0 Solar Photovoltaic

              Conversion of sunlight into
electricity is called as photovoltaic energy. With the help of a photovoltaic
cell, commonly called a solar cell or PV, the solar energy can directly convert
into electrical power. A photovoltaic cell is made up of silicon alloys which
is refer as a non-mechanical device.

           Sunlight has a composition of protons,
or particles of solar energy. Various amounts of energy corresponding to the
different wavelengths of the solar spectrum is contain in the protons
found in the sun radiant.  When a photovoltaic cell is strike by the
protons, they may be reflected, pass right through, or be absorbed. Only the
protons which absorbed the energy will generate the electricity 12.

1: Structure of a photovoltaic cell


            A photovoltaic array’s performance
is dependent upon sunlight. There will a significant effect on the amount of
solar energy received by a photovoltaic array which might effect by the climate
conditions such as clouds and fog, which in turn will affect   its
performance. Recent photovoltaic technology modules having 10% of converting
efficiency. Further research is being conducted to raise this efficiency 12.


            A solar photovoltaic technology is one of the
renewable technologies, which has a potential to shape a clean, reliable,
scalable and affordable electricity system for the future. The earth gets a
stunning supply of solar energy in the future. Considering this fact, all over
the world governments are encouraging the development and deployment of solar
PV technology. A wide range of PV materials are available worldwide. Globally,
there are hundreds of companies involved in the manufacturing of PV modules
with varying efficiencies and limitations. At the same time, installation costs
differ from system to system and from project to project.


             Globally there are more than 350
companies from different countries involved in manufacturing of PV cells. Based
on the years of 2014’s review , the major five leading countries identified are
China, Japan, USA, Germany and UK. These five countries altogether accounted
for 80% of photovoltaic installations in 2014. The cumulative global PV
capacity has reached 177 GW by means 1% of world electricity generation is from
PV. In addition, by the end of year 2014, there are 20 countries across the
globe that has passed the benchmark of 1 GW cumulative PV installation. For the
year 2014, it has been noticed that Asia ranks in first place for the second
year in a row with around 60% of the global PV installations 12.


             China, one of the biggest
contributors of Asia since decade, installed 10.6 GW in 2014. USA has installed
6.2 GW in 2014 with large-scale and new business models dominating the market.
However, Europe has significantly declined from 22 GW of installation per year
in 2011 to around 7 GW in 2014. Nevertheless, in the year 2014, PV contributes
3.5% of the electricity demand in Europe and 7% of the peak electricity demand
(International Energy Agency, 2015a). UK by installing 5 GW of PV projects holds
the first position in European countries for PV installation in the year 2014,
followed by Germany (1.9 GW) and France (0.9 GW) 12.

2. PV installations in the year 2014 for leading countries 12.


               From the figure, it clearly shows
that China has extremely rich solar energy resources and its PV industry is
growing on a faster pace than any other country in the. Such growth has been
made possible due to the significant support of government incentives and


              The Renewable Energy Law was planned in 2005
by the National People Congress (NPC) and implemented in January 2006. It was
based on five key mechanisms:

(a)    National
target for development of renewable energy: it directs the investment towards
all sources of renewable energies

(b)   A
mandatory connection and purchase policy between grid companies and renewable
energy electricity generator: grid companies need to sign an agreement that
they will purchase renewable electricity from all renewable electricity generators
and provides the grid connection services

(c)    Feed
in Tariff (FiT) system and price: FiT prices are fixed and will be paid to
renewable electricity generators for each kWh electricity generated

(d)   Cost
sharing mechanism: the cost of grid connection and renewable energy generation
will be divided among utilities and end users of electricity by implementing a
surcharge on sold electricity

(e)    The
renewable energy development special funds: based on this funds will be
provided to activities like research and development of renewable energy,
setting up pilot projects or renewable resources assessments


             Japan policies are always in the
favour of the PV technology. It has constantly noticed that either these
policies are targeting the deployment of R on PV technology or on the
climate change issue. After the oil crisis in 1973, Japan introduced its first
PV industry support project named as Sunshine Project in 1974 which was
established by Ministry of Economy. In 2007, Japan’s Prime Minister launched a new
scheme named as Japan’s Cool Earth Initiative (2008) with the aim of reducing
the greenhouse gases by 50% by 2050. It involves the development of latest 21
technologies including solar cell technology. One of the plans under this
program is to develop low cost solar cell with conversion efficiency up to 40%
and generate power at £0.04/kW (7 Yen/kW) as compared to the current rate of
£0.21/kW (40 yen/kW). In July 2012, another scheme called FiT  was introduced which resulted more than 20.9
GW of PV projects, which were approved by the end of May 2013.12


In the Middle East, Israel endured as the very first market. While it
remains to be shown that this system can be commercially viable, it shows how
the cost decline of PV systems in the past centuries has brought down PV
electricity manufacture costs.4


Europe, the market sustained to decline, in spite of the growth of the UK
market that recognized itself as first place in Europe with 2.4 GW in 2014.
Germany experienced another market decline to 1.9 GW, with extremely reasonable
enticements.  France grow of France
was  close to 1 GW and  the Italian market, as feed-in tariffs (FiT) markets
were phased-out, it inclined to a rather low level (424 MW).4


              The solar photovoltaic
advancement is one such source that can looked upward to as boundless research
is being done and a basic change in execution has been refined. PV is one of
the fastest creating ventures worldwide thus as to keep up this improvement
rate necessity for new advancements concerning material use and usage, gadget
outline and generation innovations and likewise new plans to fabricate the
general profitability develops. A couple of PV advances, going from silicon to
thin movies, multi-intersection and solar concentrator structures for terawatt
level arrangement of the current solar cells, and for every innovation,
distinguished changes and developments required for further scale-up. Solar PV
energy is the answer of future energy challenges 5.


3.0 Generations of Solar PV

First Generation 


solar cells are made from silicon, are currently the most efficient solar cells
available for residential use and account for around 80+ percent of all the
solar panels sold around the world. Solar cells of silicon bases are more
efficient and longer lasting than non-silicon based cells. However, they are
more at risk to lose some of their efficiency at higher temperatures (hot sunny
days), than thin-film solar cells. 11 Currently four types of silicon based
cells are in for residential use. The types are based on the type of silicon
used, specifically:


Monocrystalline Silicon Cells

of the oldest solar cell technology which is still considered as  popular with high efficiency are solar cells
made from thin wafers of silicon. These are called monocrystalline solar cells
because the cells are sliced from large single crystals that have been
painstakingly grown under carefully controlled conditions. Typically, the cells
are a few inches across, and a number of cells are laid out in a grid to create
a panel.


to the other types of cells, they have a higher efficiency (up to 24.2%),
meaning will obtain more electricity from a given area of panel. This is useful
if when have a limited area for mounting panels, or if want to keep the
installation small for aesthetic reasons. However, growing large crystals of
pure silicon is a difficult and very energy-intensive process, so the
production costs for this type of panel have historically are the highest of all
the solar panel types.


             Production and price for raw silicon have
improved and panels from monocrystalline solar cells have fallen a great deal
over the years, due to the competition where other types of panel have been
produced. Another issue arise from monocrystalline silicon cells is that the
efficiency of theses panels reduce when the temperature increases about 25?C. Due
to this reason, the installation has to made is such way in order increase
their efficiency by permit the air to circulate over and under the panels. 11


Polycrstalline Silicon Cells


wafers are cheaper to produce in molds from multiple silicon crystals rather
than from a single crystal as the conditions for growth do not need to be as tightly
controlled. In this form, a number of interlocking silicon crystals grow
together. Generally speaking, polycrystalline panels have an efficiency that is
about 70% to 80% of a comparable monocrystalline solar panel. The most
efficient polycrystalline panels are built by Mitsubishi Electric Corporation.
In February 2010, two world record is achieve by Mitsubishi for photoelectric
conversion efficiency in polycrystalline silicon photovoltaic (PV) cells by
decreasing the  resistive loss in the
cells. The conversion efficiency rates have been confirmed by the National
Institute of Advanced Industrial Science and Technology (AIST), in Japan. 11



Amorphous Silicon Cells


of developing silicon precious stones is done in making the two past sorts of
sun powered cells, silicon is kept in a thin layer on to a support substrate,
for example, metal, glass or even plastic. At times a few layers of silicon,
doped in somewhat unique approaches to react to various wavelengths of light,
are laid over each other to enhance the effectiveness. The creation strategies
are mind boggling, however less vitality serious than crystalline boards, and
costs have been descending as boards are mass-delivered utilizing this


panels can  made flexible if very thin
layers of silicon is used. The disadvantage of amorphous panels is that they
are much less efficient per unit area (up to 10%) and are generally not suitable
for roof installations where it would require two times the area for the same
power panels. Having said that for a given power rating, they do perform better
at low light levels than crystalline panels which is worth having on a dismal
winter’s day, and when the temperature increases, it does not effect their


there flexibility makes them an excellent choice for use in making building
integrated PV (e.g., roofing shingles), for use on curved surfaces, or even
attached to a flexible backing sheet so that they can even be rolled up and
used when going camping / backpacking, or put away when they are not needed. 11


Hybrid Silicon Cells

           One recent
trend in the industry is the emergence of hybrid silicon cells and several
companies are now exploring ways of combining different materials to make solar
cells with better efficiency, longer life, and at reduced costs.

Sanyo introduced a hybrid HIT cell whereby a layer of amorphous silicon is
deposited on top of single crystal wafers. The result is an efficient solar
cell that performs well in terms of indirect light and is much less likely to
lose efficiency as the temperature climbs.


Second Generation


              Second-generation solar cells are
usually called thin-film solar cells because when compared to crystalline
silicon based cells they are made from layers of semiconductor materials only a
few micrometers thick. The combination of using less material and lower cost
manufacturing processes allow the manufacturers of solar panels made from this
type of technology to produce and sell panels at a much lower cost.


             There are basically three types of
solar cells that are considered in this category, amorphous silicon, and two
that are made from non-silicon materials namely cadmium telluride (CdTe), and
copper indium gallium diselenide (CIGS). Together they accounted for around
16.8% of the panels sold in 2009.


              First Solar, the number one
producer and seller of solar panels in the world currently makes their solar
cells using cadmium telluride. The big appeal of these type of solar cells is
that they are inexpensive (currently below $1.00 / watt to produce and heading
towards $0.70 / watt).              Venture
capitalists love CIGS solar cells (or at least used to – as they have invested
over $2.3 billion into companies developing these cells but have yet to see them
be a commercial success) as they have been able to reach efficiency levels of
20% in the laboratory. Unfortunately it has turned out to be much more
difficult to produce CIGS solar cells in mass quantities at competitive prices
with anywhere near than efficiency level, so the jury is still out on this
technology. 11

Third Generation Solar Cells

             Currently there is a lot of solar
research going on in what is being referred to in the industry as
Third-generation solar cells. In fact according to the number of patents filed in
the United States  solar research ranks
second only to research in the area of fuel cells.


             This new generation of solar cells
are being made from variety of new materials besides silicon, including
nanotubes, silicon wires, solar inks using conventional printing press
technologies, organic dyes, and conductive plastics. The goal is to improve on
the solar cells already commercially available by making solar energy more
efficient over a wider band of solar energy (e.g., including infrared), less
expensive so it can be used by more and more people, and to develop more and
different uses.Currently, most of the work on third generation solar cells is
being done in the laboratory, and being developed by new companies and for the
most part is not commercially available. 11

Figure 3: Efficiency and cost projections for first- (I),
second- (II), and third generation


4.0 High efficiency solar cell


                 Tandem PV devices are the best
developed so far and help change, regardless of whether by extended
concentrator structure productivity or by diminished cost and extended adequacy
of thin-film designs, can impact much lower general costs per Watt. Regardless,
these devices tend to encounter the ill effects of poor spectral robustness.
Chip away at middle of the road level gadgets and up/down transformation is at
a much prior stage, yet guarantees expanded efficiencies and more prominent
spectral robustness, conceivably with thin-film-sort materials. The more moved
thoughts of different transporter period and hot bearer cells are further away
and still have genuine hypothetical request to answer. In any case, execution
of such techniques could essentially reduce cost per Watt with spectral
robustness as they are good with theoretically moderately basic thin-film
gadgets 9.


                 A tandem cell, by definition,
comprises of no less than two p-n intersections with cells made out of
materials that retain diverse photon energies. The top cell would assimilate
the higher energies while the base cell would retain the lower energies that
were not consumed by the top cell, like the guideline behind thin film cells.
The couple cell would then have a higher productivity as it could retain more
photons of the sunlight based range for vitality transformation. This
innovation is as of now being put to use in sun oriented cells in space. Pair
sun oriented cells are ordinarily made of mixes of components in the III and V
gatherings of the occasional tables. Cases of these mixes are: gallium arsenide
(GaAs), indium phosphide (InP), gallium antimonide (GaSb), gallium indium
phosphide (GaInP), and gallium indium arsenide (GaInAs). These sun powered
cells have the most elevated reported effectiveness at 43% when utilizing a
three cell sun oriented cell, yet they utilize uncommon metals and are
amazingly costly to manufacture, so they are not commonsense for use on far
reaching earth.8


Expanded number of cells in a couple cell will build the hypothetical
most extreme effectiveness of the solar cell, however there still remains a
breaking point to the productivity. A solitary cell has a hypothetical greatest
productivity of 31%. A two cell pair sun oriented cell has a greatest
proficiency of 42.5%; a three cell sun oriented cell has a most extreme
effectiveness of 48.6%, etc. The hypothetical most extreme efficiencies will
keep on increasing, however an interminable heap of solar cells has a greatest
proficiency of just 68.2%. The proficiency picked up by including another cell
diminishes with each ensuing expansion.8


   Considering that “the main practical
solar cells were made under 30 years back,” there have been some
significant progress. The profligation of solar energy organizations outlining
one of a kind and particular solar energy frameworks for individual homes,
implies there is no more extended a reason not to consider the usage of solar
energy. The greatest hops in productivity came “with the appearance of the
transistor and going with semiconductor innovation.” The generation cost
has tumbled to about 1/300 of what it was amid the space program of the
mid-century and the buy cost has gone from $200 per watt in the 1950s to a
conceivable simple $1 per watt today. The productivity has expanded
significantly to 40.8% the US Department of Energy’s National Renewable Energy
Lab’s new world record as of August 2008.9


5.0 Conclusion


            There are a couple of central
purposes of photovoltaic solar energy that make it “a champion among the
most promising renewable energy sources on the earth. It is non-polluting, has
no moving parts that could particular, requires little support and no
supervision, and has a presence of 20-30 years with low running costs. It is
especially remarkable in light of the fact that no large scale establishment is
required. Remote reaches without a lot of an extend convey their own particular
supply of energy by creating as meager or as tremendous of a system as required.
Solar power generators are basically scattered to homes, schools, or
associations, where their social gathering requires no extra progression or
land extend and their ability is shielded and quiet. Contrast those qualities
with those of coal, oil, gas, or nuclear power, and the choice is
straightforward. solar energy progressions offer a spotless, inexhaustible and
private vitality source. Wind control, hydro power as well as solar thermal
power needs maintenance and they have parts that dissemble. Therefore in this
sense, solar PV has an advantage over them.11


               By enhancing the efficiency of
solar cells, the cost of solar energy can be limited also as indicated by Larry
Kazmerski, Director of the DOE’s National Center for Photovoltaics. Any
improvements and progressive cost lessening will be important to space
applications. Finding the privilege electrical organization likewise can help
lessen the cost. They can enable you to profit with such choices. As time
passes by, the cost solar energy will keep on decreasing while the costs of
powers keep on being on the ascent. This will at that point imply that solar
energy is going into another period of worldwide development. 10