|
At this junction, an
interior electric field is built
up which leads to the separation
of the charge carriers that are
released by light. Through metal
contacts, an electric charge can
be tapped. If the outer circuit
is closed, meaning a consumer is
connected, then direct current
flows.
Silicon cells
are approximately 10 cm by 10 cm
large (recently also 15 cm by 15
cm). A transparent
anti-reflection film protects
the cell and decreases
reflective loss on the cell
surface.
 |
|
Model of a crystalline
solar cell |
Characteristics of a Solar Cell
The usable voltage from solar
cells depends on the
semiconductor material. In
silicon it amounts to
approximately 0.5 V. Terminal
voltage is only weakly dependent
on light radiation, while the
current intensity increases with
higher luminosity. A 100 cm²
silicon cell, for example,
reaches a maximum current
intensity of approximately 2 A
when radiated by 1000 W/m².
 |
|
current-voltage line of
a si-solar cell |
The output (product of
electricity and voltage) of a
solar cell is temperature
dependent. Higher cell
temperatures lead to lower
output, and hence to lower
efficiency. The level of
efficiency indicates how much of
the radiated quantity of light
is converted into useable
electrical energy.
The principles of solar cell
power generation
Solar cell is a light,
responsive and are able to
convert light energy into
electrical devices. Photovoltaic
effect can produce many kinds of
materials, such as: silicon,
polycrystalline silicon,
amorphous silicon, gallium
arsenide, copper indium
selenium. They are basically the
same principles of power
generation is now crystal as an
example to describe the process
of light generation. P-type
crystalline silicon doped with
phosphorus available through
N-type silicon, the formation of
P-N junction.
When the light irradiation solar
surface, part of the photons
absorbed by silicon material;
photon energy transfer to the
silicon atoms, so that
electronic transitions have
taken place and become a free
electron concentration in the PN
junction formed on both sides of
the potential difference, when
the external circuit connected ,
in which the role of voltage,
there will be current flow
through the external circuit
produces a certain output power.
The essence of this process is:
the process of photon energy is
converted into electrical
energy.
Different Cell Types
One can distinguish three cell
types according to the type of
crystal: monocrystalline,
polycrystalline and amorphous.
To produce a monocrystalline
silicon cell, absolutely pure
semiconducting material is
necessary. Monocrystalline rods
are extracted from melted
silicon and then sawed into thin
plates. This production process
guarantees a relatively high
level of efficiency.
The production of
polycrystalline cells is more
cost-efficient. In this process,
liquid silicon is poured into
blocks that are subsequently
sawed into plates. During
solidification of the material,
crystal structures of varying
sizes are formed, at whose
borders defects emerge. As a
result of this crystal defect,
the solar cell is less
efficient.
If a silicon film is deposited
on glass or another substrate
material, this is a so-called
amorphous or thin layer cell.
The layer thickness amounts to
less than 1µm (thickness of a
human hair: 50-100 µm), so the
production costs are lower due
to the low material costs.
However, the efficiency of
amorphous cells is much lower
than that of the other two cell
types. Because of this, they are
primarily used in low power
equipment (watches, pocket
calculators) or as facade
elements.
|
Material
|
Level of
efficiency in % Lab
|
Level of
efficiency in %
Production
|
|
Monocrystalline Silicon
|
approx. 24 |
14 to17 |
|
Polycrystalline Silicon
|
approx. 18
|
13 to15 |
|
Amorphous Silicon
|
approx. 13 |
5 to7 |
From the Cell to the Module
In
order to make the appropriate
voltages and outputs available
for different applications,
single solar cells are
interconnected to form larger
units. Cells connected in series
have a higher voltage, while
those connected in parallel
produce more electric current.
The interconnected solar cells
are usually embedded in
transparent Ethyl-Vinyl-Acetate,
fitted with an aluminum or
stainless steel frame and
covered with transparent glass
on the front side.
The typical power ratings of
such solar modules are between
10 Wpeak and 100 Wpeak. The
characteristic data refer to the
standard test conditions of 1000
W/m² solar radiation at a cell
temperature of 25° Celsius. The
manufacturer's standard warranty
of ten or more years is quite
long and shows the high quality
standards and life expectancy of
today's products.
Electricity Energy Monitors
(Sailwider-SmartPower's monitor
can be used to monitor home
solar plant)
Wireless Electricity
Energy Control System with
monitoring function for Home
Solar Power Generator Plant
The basic figures contained
within a monthly or quarterly
electricity bill do not give you
much information as to where
your electricity is going - they
just tell you how much you have
used in total during that period
and how much totally you need to
pay. Therefore it is well worth
considering purchasing an
electricity usage monitor and
using it to see exactly where
all your hard-earned money is
going.
One great way to find out how
much electricity each of your
household appliances and
electronic devices uses is with
a wireless electricity
power/energy monitor, which
shows you in real time exactly
how much money your total home
or office electricity usage is
costing you. These monitors can
help you reduce your electricity
consumption by as much as 20%
simply by showing you what you
are using.
Sailwider-SmartPower is a developer and
manufacturer of electricity power
monitor and controlling system.
Most electricity energy monitors
in the market are uni-directional
(1-way) only, that means you can only
get energy consumption
information from the monitor.
The
bi-directional (2-way)
electricity power monitoring and
control system
from Sailwider-SmartPower makes
the user not only able to
monitor the electricity usage,
but also can easily remote control
the connected electrical
appliances wirelessly, providing great
convenience to electricity
efficiency management.
 |
