| What is solar cell? |
A
photovoltaic cell (commonly called a solar cell) is a
nonmechanical device usually made from silicon alloys.
It converts sunlight into electricity. The PV cell was
discovered in 1954 by Bell Telephone researchers. Late
1950s, PV cells were used to power U.S. space satellites.
Individual cells can vary in size from about 1 cm (1/2
inch) to about 10 cm (4 inches). Most photovoltaic cells
are about ten percent efficient in covering sunlight to
electricity with further research being conducted to raise
this efficiency to fifteen-twenty percent.
Photovoltaic conversion is useful for several reasons.
Conversion from sunlight to electricity is direct, so
that bulky mechanical generator systems are unnecessary.
The modular characteristic of photovoltaic energy allows
arrays to be installed quickly and in any size required
or allowed.
Presently BCSC (Buried Contact Solar Cells) and Polycrystalline
CdTe-baser Photovoltaic are the latest technology in the
solar cells and having efficiency is around 15-20 % approx.
and we can get stable power output and long life. |
| |
| How does a solar cell work? |
Sunlight is composed
of photons, or particles of solar energy. These photons
contain various amounts of energy corresponding to the
different wavelengths of the solar spectrum. When photons
strike a photovoltaic cell, they may be reflected, pass
right through, or be absorbed. Only the absorbed photons
provide energy to generate electricity. When enough sunlight
(energy) is absorbed by the material (semiconductor),
electrons are dislodged from the material's atoms. Special
treatment of the material surface during manufacturing
makes the front surface of the cell more receptive to
free electrons, so the electrons naturally migrate to
the surface. When the electrons leave their position,
holes are formed. When many electrons, each carrying a
negative charge, travel toward the front surface of the
cell, the resulting imbalance of charge between the cell's
front and back surface creates a voltage potential like
the negative and positive terminals of a battery. When
the two surfaces are connected through an external load,
electricity flows. |
| |
| What is scribing and why scribing is
necessary? |
Scribing means,
cutting of a grid pattern of grooves in a semiconductor
material generally for the purpose of marking interconnections
or to cut the solar cells into two parts.
Laser scribing is done for the fabrication of monolithic
cell interconnections. Scribing, either with a mechanical
stylus or a laser is used for fabricating series interconnections
allowing a large, thin-film photovoltaic panels to be made
with, for example, 100 cells monolithically interconnected.
The series interconnection allows the same electrical power
to be produces from the panel with a voltage 100 times that
of an individual cell and the current equal to that of one
cell. For CdTe thin films, the individual cell voltage is
about 0.8V |
| |
| Comparison between Conventional Diamond
Cutter system for solar cells & Laser Solar Cell scribing
system: SLT-SS-2000 offered by SAHAJANAND LASER TECHNOLOGY. |
| |
| Technical: |
| Features |
Conventional System |
Laser System |
Advantages of Laser |
| Tool |
Diamond cutter |
Laser cutter |
Non contact type tooling. Most suitable for the
brittle materials which is used in Solar cell. |
| Positioning Speed |
|
60 mm / sec |
More Positioning speed. |
| Cutting Speed |
8.00 mm /sec |
30 mm / sec |
Faster scribing leads to comparatively high productivity. |
| Kerf width of the tool |
45 microns |
1 8 microns |
less wastage : Because a cell costs around $ 4.1:
more material saving, more economical. |
| Tooling Cost |
One Diamond Cutter approx. can cut 15,000 cell |
Laser : No replacement of tool |
Cutter cost can be saved. |
| Depth of cut |
|
0.6 mm |
Precise depth of cut can be achieved. |
| Accuracy |
|
1 micron precise accuracy |
More accuracy can be achieved. |
| Cost |
|
|
Very Cost Effective |
|
The laser's
precision means cell divisions can be very thin, allowing
more glass surface to be devoted to power production.
In addition to the increased processing efficiency of
laser scribing and cleaving of solar cells compared to
conventional diamond cutting, laser scribing also significantly
diminishes the generation of shunts, which degrade the
operation voltage of the cell. |
| |
|
| Laser
Head |
| Laser |
Lamp Pumped Nd:YAG Laser |
| Wavelength |
1.064µm |
| Transverse Mode |
TEMoo |
| Beam Diameter |
1.0 mm, nominal , M2 < 2.5 |
| |
|
| Q-Switched Performance at
3 kHz |
| Average Power |
75 Watts |
| Pulse Width, nominal |
110 ns |
| Peak Pulse Power |
75 kW |
| Pulse Stability ( peak- peak ) |
5% |
| |
|
| CONTROLLER & CNC SYSTEM |
| Controller |
PC based |
| Axis Travel (X & Y) |
200 mm x 200 mm ( 250mm X 250mm optional ) |
| Resolution |
1 Micron |
| Accuracy |
2 Micron / 25 mm |
| Repeatability |
2 microns / 25 mm Bi-directional |
| Straightness & Flatness |
2 Micron / 25 mm |
| Of Travel |
|
| Drive |
Servo Control Drives |
| Z Axis |
Manual |
| |
|
| VISION SYSTEM |
| CCTV Camera |
In-built |
| |
| MECHANICAL |
| Dimensions |
(L) 2000 mm x (W) 807 mm x (H) 1700 mm |
| |
|
| ELECTRICAL |
| Power |
380 ± 10% VAC, 3 Phase, 50/60 Hz. |
| |
|
| SOFTWARE |
| Dedicated software for Solar
Cell Cutting Application |
 |
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