Product specifications

5150
Technical definitions
Amorphous silicon solar cells
The term amorphous refers to the non-crystalline structure of
silicon atoms. The efficiency is lower than crystalline silicon, and
typically ranges from 5% to 10%. The energy yield per installed
Watt peak is higher compared to crystalline silicon modules
because of the relatively high efficiency at low irradiation.
Autonomous PV systems
Supply electricity to locations where no public grid is available or
a long distance from that grid. In such situations, a PV system is
significantly cheaper than connecting to the mains or a non-stop
generator.
Energy-neutral building
A building where the balance between energy production and
energy consumption is zero on a yearly basis. This can be
achieved by installing various renewable energy sources like PV
cells, hot water systems, heat pumps etc.
Grid connected PV system
The low voltage direct current (DC) electricity is converted to
230 V alternating current (AC) power by an inverter. The
inverter feeds the electricity, produced by the PV system, back
into the utility grid. This means the PV system actually functions
as a mini power station. If the solar energy production is higher
than the electricity consumption at any given moment, most
electricity meters spin backwards. The returned electricity is
automatically incorporated in the energy bill.
Inverter efficiency
A percentage that indicates which proportion of the incoming
solar-generated electricity is being transformed into useful AC
energy. Modern high-quality inverters have efficiencies higher
than 92%.
Irradiation
The light intensity in a given area. Africa, for example, receives
around twice as much sun as the Netherlands. Irradiation varies
within a country too: In the Netherlands for example, it varies
between 980 kWh/m² per year in the east to 1070 kWh/m² on the
west coast. The average air temperature is also of importance for
the annual energy yield of a PV system; solar cells perform better
at lower temperatures (see also Underdimensioning).
Maximum Power Point Tracker
An intelligent voltage regulator that adjusts the operating voltage
of the PV array to variations in temperature and cell type. A good
MPP tracking algorithm draws the maximum solar power from
the PV array in all conditions.
Monocrystalline silicon solar cells
Monocrystalline silicon solar cells are cells made from one large
monocrystal. Thanks to this method of production we have
round solar cells, each made from one silicon crystal. The
standard dimensions are 10 by 10 cm. Monocrystalline silicon
solar cells typically have an efficiency of 16% to 18%.
Output of a PV system
Solar panels have an efficiency that varies between 8% and 18%.
The orientation and shading of the panels and the panel
temperature can also affect the eventual output.
Photovoltaic systems
Also known as PV systems. The word Photovoltaic is a
combination of the Greek word for light and the name of the
physicist Alessandro Volta. It denotes the direct conversion of
sunlight into energy by means of solar cells.
Polycrystalline/multicristalline silicon solar cells
Solar cells made up of multiple silicon crystals. As the crystal
edges can impede the electron flow, multicrystalline silicon solar
cells are usually less efficient than the monocrystalline equivalent.
The output is usually between 14% and 16%. Most poly-
crystalline silicon solar cells are blue in colour.
Power loss
Power loss can be caused by the location and orientation of the
solar cells and other factors such as:
• Placement losses caused by non-ideal orientation to the sun.
• Shading losses: Even partial shading of cells or modules causes
relatively high losses.
• Panel losses caused by the electrical resistance of inter-
connections inside the solar module and losses introduced by
series connection of the cells (see String).
• Inverter losses: Solar energy converted to heat and therefore
not fed back into the grid.
• Cable losses caused by the electrical resistance of the wiring.
• Temperature losses: solar voltage and power decreases with
±0.5% per degree Celsius. This may lead to relatively large
losses at full irradiance (see also Underdimensioning).
Shading
Shading of solar cells may lead to electrical resistance within a
closed current loop. This resistance causes the shaded cells to
heat up and, if the temperature rises sufficiently, to break down
(the Hot-Spot effect). To prevent this, small groups of cells are
protected by a bypass diode that stops the shaded solar cells
from heating up.
Silicon
Raw material for solar cells.
Solar cell
In a solar cell, light energy (photons) is converted into electric
power. See also Working principle of a solar cell.
Solar energy applications
• The active or passive heating of buildings.
• The heating of tap water.
• The generation of electricity (photovoltaic solar energy or PV).
Solar panel
A group of PV cells combined in one unit.
STC or standard conditions
Conditions used to set the panel capacity: a cell temperature of
25 °C and light intensity of 1000 W/m
2
.
String
A group of solar cells (or solar panels) connected in a series.
When solar cells or modules are series-connected, the voltage
will add up with the number of cells/modules, while the current
is equal to the current of one cell. Because of the relatively low
current, electrical losses in wiring are low as well. A string of
cells or modules performs only as well as the worst cell/module
in the string. If differences between solar cells or panels are
significant, it may be worthwhile separating lower performance
modules from higher and combining them into separate strings. If
cells, modules or strings are connected in parallel, the current
will add up with the number of units connected in parallel, while
voltage remains constant. With both parallel or series
connection, the total power generated is the sum of all the
power generated by the connected solar cells.
Underdimensioning
Means that the nominal input power of an inverter is less than the
power of the PV array, expressed in kWp. In one year, the solar
array will seldom generate the specified Watt peak power. In
Northern Europe, the inverter input power can generally be
chosen to be around 80% of the PV capacity without introducing
significant losses.
Watt peak (Wp)
A measure of the electrical power a solar cell or module will
generate at standard conditions. See also STC.
Working principle of a solar cell
Solar cells consist of two layers of semi-conducting material,
usually silicon. Between these two layers, the n-layer above and
the p-layer below, is an electric field. When sunlight shines on the
n-layer it is partly absorbed by the semi-conductor and converted
into energy (heat). This energy generates electrons that are free
to move through the material. The crystalline structure of the
silicon and the electrical field ensure that the free electrons move
in a certain direction. This phenomenon is called electricity, and
the flow is taken from the cell for use in external applications.