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PV Array -
A group of PV (photovoltaic)
modules (also called
panels
) arranged to
produce the voltage and power desired.
PV Array-Direct -
The use of electric power
directly from a photovoltaic array, without
storage batteries to store or stabilize it. Most
solar water pumps work this way, utilizing a
tank to store water.
PV Cell -
The individual photovoltaic device.
Most PV modules are made with around 36 or
72 silicon cells, each producing about 1/2 volt.
PV Module -
An assembly of PV cells framed
into a weatherproof unit. Commonly called a
“PV panel”. See
PV array
.
Solar Tracker -
A mounting rack for a PV
array that automatically tilts to follow the daily
path of the sun through the sky. A “tracking
array” will produce more energy through the
course of the day, than a “fixed array” (non-
tracking) particularly during the long days of
summer.
Voltage, Open Circuit -
The voltage of a PV
module or array with no load (when it is
disconnected). A “12 Volt Nominal” PV
module will produce about 20 Volts open
circuit. Abbreviation: Voc.
Voltage, Peak Power Point -
The voltage at
which a photovoltaic module or array transfers
the greatest amount of power (watts). A “12
Volt Nominal” PV module will typically have a
peak power voltage of around 15-17 volts.
The solar array for a PV array-direct solar
pump should reach this voltage in full sun
conditions, or a multiple of this voltage.
Abbreviation: Vpp.
Pumps & Related Components
Booster Pump -
A surface pump used to
increase pressure in a water line, or to pull
from a storage tank and pressurize a water
system. See
surface pump
.
Centrifugal Pump -
A pumping mechanism
that spins water in order to push it out by
means of centrifugal force. See also
multi-
stage
.
Check Valve -
A valve that allows water to
flow one way but not the other.
Diaphragm Pump -
A type of pump in which
water is drawn in and forced out of one or
more chambers, by a flexible diaphragm.
Check valves let water into and out of each
chamber.
Float Switch -
An electrical switch that
responds to changes in water level. It may be
used to prevent overflow of a tank by turning a
pump off, or to prevent a pump from running
dry when the source level is low.
Float Valve -
A valve that responds to
changes in water level. It is used to prevent
overflow of a tank by blocking the flow of
water.
Foot Valve -
A check valve placed in the
water source below a surface pump. It
prevents water from flowing back down the
pipe and “losing prime”. See
check valve
and
priming
.
Helical Rotor Pump
- A pump with a helix-
shaped rotor that fits closely into a rubber
stator that has a helical groove. It forms
sealed cavities that trap water. As the rotor
turns, the cavities move toward the outlet. See
positive displacement pump
. Synonyms:
progressive cavity pump, screw pump.
Impeller -
The device that spins inside of a
centrifugal pump, in order to develop centrifu-
gal force.
Jet Pump -
A surface-mounted centrifugal
pump that uses an “ejector” (venturi) device to
augment its suction capacity. In a “deep well
jet pump”, the ejector is down in the well, to
assist the pump in overcoming the limitations
of suction. (Some water is diverted back
down the well, causing an increase in energy
use.)
Multi-Stage Centrifugal -
A centrifugal
pump with more than one impeller and
chamber, stacked in a sequence to produce
higher pressure. Conventional AC deep well
submersible pumps and some solar
submersibles work this way.
Positive Displacement Pump -
Any mecha-
nism that seals water in a chamber, then
forces it out by reducing the volume of the
chamber. Examples: piston, diaphragm,
helical rotor, vane. Used for low volume and
high lift. Contrast with
centrifugal
. Synonyms:
volumetric pump, force pump.
Priming -
The process of hand-filling the
suction pipe and intake of a surface pump.
Priming is generally necessary when a pump
must be located above the water source. A
self-priming
pump is able to draw some air
suction in order to prime itself, at least in
theory. See
foot valve
.
Pulsation Damper -
A device that absorbs
and releases pulsations in flow produced by a
piston or diaphragm pump. Consists of a
chamber with air trapped within it or a length
of flexible tube.
Glossary of Solar Electricity and Water Pumping continued
