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Scroll down for pictures and definitions related to solar electric
PV and solar hot water systems (listed in alphabetical order)
|This type of system uses a small pump to
circulate the water through the solar heating
panel from the water storage tank. Usually the
pump is powered by solar electricity. Passive
systems depend on water pressure to circulate
2 or more modules
Alternating Current (AC)
Electrical current that alternates from positive to
negative. This type of current is required to
operate most electrical appliances and motors.
This system uses weight in the form of specially
designed concrete pads to hold the modules on
the roof. This type of system requires less
penetrations of the roof but may cost more.
Battery Backup System
Batteries are used to store electrical power that
is produced by the PV modules. The stored
electrical power can then be used to power
appliances when there is no power available
from the electrical grid. There are a number of
different types of batteries available. Battery
Backup systems are more costly and complicated
than grid tied systems.
Bifacial PV modules
New type of module developed by Sanyo that can
collect reflected solar energy from underneath
the module as well as direct solar energy from
the top side, thus increasing efficiency. This type
of module must be located over a white or
reflective surface so light is reflected up to the
underside of the module.
These are used to hold the modules to frames.
There are many types
This is where the wires from separate arrays are
all connected to one wire that goes to the to the
Direct Current (DC)
Electrical current that flows in on direction. PV
cells produce direct current. But most appliances
are designed to work with alternating current.
Disconnect Switch (box)
Required device that allows the current from the
PV array to be shut off to the house or circuit.
The modules are attached to frames. There are
many types of frames.
Grid Tied PV system
Electricity generated by PV modules is converter
to AC power and either used by appliances or
sent to the electrical grid. In order to function the
gird tied system must have a working electrical
grid connection. This type of system will not work
when the power is out. It is the most common
type of PV system. It costs less than battery
Ground mounted PV system
These are generally less expensive to build than
roof top systems.
Required to connect to all module frames in the
array in order to ground the array. Special clamps
hold the grounding wire to the frames. See also
WEEBs (scroll down)
Is a measure of solar radiation received on a
given surface area in a give time. Under standard
test conditions (STC) it is considered to be 1000
watts per meter squared
A device the converts direct current (DC) to
alternating current (AC)
A measure of the intensity of solar power (see
insolation). Irradiance increases when
temperatures go down. This affects wire sizing
A measure of solar energy accumulated on a
given area in a given time
Usually a metal box in which wires are connected
These are the UL listed connections on the
wiring that comes attached to the modules. They
require a special tool to open them.
Maximum Power Point (MPP)
This is a term for the maximum power that can be
produced by a PV array depending on the current
and voltage available.
Maximum Power Point Tracking (MPPT)
Electronic system designed to get the most
output from PV arrays under changing
temperature and irradiance
Enphase Energy has developed a type of module
that has its own inverter. Since each module has
an inverter the DC current is converted to AC at
the modules. This may reduce costs from the
wiring needed to conduct DC longer distances to
a large inverter for the array. It may also make it
feasible to set up arrays in areas where some
modules may get shade which would not be
feasible with the conventional system of one
inverter for the whole array.
These are made up of a lot of photovoltaic cells
that are wired together to generate electricity
Open Circuit Voltage (Voc)
Maximum voltage when there is no current
Solar PV modules are required to have a
nameplate on the back the lists important ratings
for the module such as max power, short circuit
current, open circuit voltage
When electrical producing units such as solar
arrays are connected in parallel the current
increase by the sum of all the arrays. See Series
Passive solar water heating
This type of system uses water pressure to
circulate the water from the storage tank to the
solar panel and doesn’t need a pump.
1000 Watts per meter squared also know as 1 Sun
A type of tubing often used in hot water floor
heating that can be used to transfer hot water
from the solar hot water panel to the hot water
storage tank. It is less efficient than copper but
less expensive. In this picture the tubing is being
covered with black pipe insulation and the run
through PVC pipe to keep it dry underground
Technology that converts sunlight into electricity
by using semiconductors
Made mostly from silicon and are capable of
generating electricity form sunlight. PV modules
are made up of cells wired in series
Poly-crystalline PV Module
A type of PV module generally a little less
efficient than the mono-crystalline type of module
This is where the p type and n type
semiconductor material in a PV cell are in contact.
Pressure Relief valve
Solar hot water panels should have a pressure
A material that has both insulating properties
(preventing electrical conduction) and will also
conduct electricity under some conditions. PV
cells and modules are made of mostly silicon
which is a semiconductor.
When pv modules are connected in series the
current remains the same but the voltage is
In this picture the PV modules are short ciruited.
This is also known as Isc. In this condition the
current is at maximum. There is no load and no
voltage output. It is safe to short circuit PV
panels and is recommended to do this to prevent
damage to connectors when installing panels.
This is a very clever device that is used to show
any shading that may occur over the year in a
location for a PV array or solar water heating
system. It is placed in the location of the
proposed solar array or hot water system and the
graph on the face of the device will show any
shading and the time of year in which it will occur.
This is a type of module that fits flat on the roof
and is considered to be more esthetically
pleasing to look at.
Standard Test Conditions (STC)
The standard conditions under which modules
are rated. These conditions are solar irradiance
of 1000 Watts per meter squared, air mass index
1.5 and cell temperature of 77F or 25C.
A type of PV module. These are generally flexible
and can be rolled up. The produce less electricity
than mono-crystalline per square foot but cost
less and produce better when temperatures are
high and light levels are low.
UL listed grounding device that connects the
modules without the need to connect them all
with a grounding wire
|Active Solar Water Heating
Solar water heating panel for an "active
solar water heating system. This type of
system has a pump powered powered by
a small pv panel. See next picture.
|Active Solar Water Heating
Hot water storage tank for an "active"
solar hot water system. This type of
system has a pump to circulate water to
panel if temperature gets low. The
pump is powered by a small solar pv
An array is 2 or more modules wired in
series. In this picture there are 4 sub
arrays. The 6 modules in each row are
wired in series. All the sub arrays are one
|Picture shows concrete blocks which are
engineered specially to comply with code
for wind loading.
|Pictures show bifacial array with white
gravel underneath to reflect light onto
bottom side. Solar energy hitting either
top or bottom is converted to electricity
|small PV panel to power pump