A Top
of Page
Absorption Charge - The second stage of three-stage battery
charging. Voltage remains constant and current tapers as internal
battery resistance increases during charging. (Ensures complete
charging.)
Alternating Current (AC) - Electric current in which
the direction of flow is reversed at frequent and regular intervals,
usually 120 times per second (60 cycles per second). It is the
opposite of direct current. For example, 120 Vac 60 Hz. power
reverses flow 60 times a second, hence the rating 60 Hz. (cycles).
This is what is found in all standard-built homes -- the two
vertical prongs plus one round one below (120 Volts in North
America or 240 Volts Internationally). This type of electrical
power is supplied by utilities or made when a generator is run.
Amorphous Silicon - Silicon in which the atoms are not
arranged in an orderly pattern as they are in single or polycrystalline
silicon solar cells.
Ampere (Amp) - A measurement of the flow of electrical
current -- the flow of electrons. One amp is produced by an electric
force of one volt acting across a resistance of one ohm. Amperes
= watts / volts. Top of Page Level
II
Amp Hour - One amp of electrical current flowing for one
hour. Expresses the relationship between current (amps) and time.
(OHMS law A =V/R)
Angle of Incidence - The angle that a light ray striking
a surface makes with a line perpendicular to the surface.
Anode - The positive electrode in an electrochemical cell
(battery). It also refers to the earth ground in a cathodic protection
system or may denote the positive terminal of a diode.
Anti-reflective coating - A thin layer of transparent
material which decreases light reflection and increases light
transmission through a glass or a surface of a solar cell.
Array - A group of solar electric modules wired together.
Autonomous System - A stand-alone photovoltaic system
which has no back-up generating source. It may or may not include
storage batteries.
Azimuth - Horizontal angle measured clockwise from true
north.
B Top
of Page Level II
Balance of System - The parts of a photovoltaic system
other than the array: switches, controls, meters, power conditioning
equipment, supporting structure for the array, and storage components,
if any.
Battery - A device that converts the chemical energy contained
in its active materials directly into electrical energy by means
of an electrochemical oxidation-reduction (redox) reaction.
Battery Capacity - The total number of ampere-hours that
can be withdrawn from a fully charged battery. See Ampere-Hour.
Battery Cell - The smallest unit or section of a battery
that can store electrical energy and is capable of furnishing
a current to an external load.
Battery Charge Regulator - An electrical device used to
keep current within a specific range. It can be used to keep
current from running backwards through an array at night or during
periods of low sunlight, thereby preventing drainage of the storage
battery. Electricity will naturally flow from the higher charge
to the lower charge. In sunlight, the higher charge will be the
array. At night, the battery has more power than the array so
the battery would power the array at night! The regulator will
prevent this.
Battery Cycle Life - The number of cycles that a battery
can undergo before failing.
Battery Self-Discharge - Loss of energy by a battery that
is not under load. Top of Page Level
II
Battery State of Charge - Percentage of full charge or
100 percent minus the depth of discharge. See Depth of Discharge.
Blocking Diode - A device that prevents electric current
from running backwards through an array at night or during periods
of low sunlight, thereby preventing drainage of the storage battery.
Borehole - A hole drilled down to reach water under ground.
Standard borehole diameters are 4 to 6 inches.
Bulk Charge - The first stage of three-stage battery charging.
Current is sent to batteries at the maximum rate they will accept
while voltage rises to full charge level.
Bypass Diode - A diode connected in parallel with a PV
module to provide an alternate current path in case of module
shading or failure.
C Top
of Page Level II
Cathodic Protection - A method of preventing oxidation
(rusting) of exposed metal structures such as bridges by imposing,
between the structure and ground, a small electrical voltage
that opposes the flow of electrons. This value is greater than
the voltage that is present during oxidation.
Centrifugal Pump - A pump that produces a pressure difference
by throwing water outwards from a central impeller.
Concentrator - A photovoltaic array which includes an
optical component such as a lens or focusing mirror to direct
incident sunlight onto a solar cell of small area.
Conversion Efficiency (Cell) - The ratio of the electric
energy produced by a solar cell (under full sun conditions) to
the energy from the sunlight incident upon the cell.
Converter - A unit that converts a DC voltage to another
DC voltage.
Current - The rate of flow of electrical charge. The flow
of amps is often expressed as current. Top of Page
Level II
Cycle - The discharge and subsequent charge of a battery.
Czochralski Process - Method of growing a perfect crystal
of large size by slowly lifting a seed crystal from a molten
bath of the material under careful conditions of cooling.
D Top
of Page Level II
Days of Storage - The number of consecutive days the stand-alone
system will meet a defined load without solar energy input. This
term is related to system availability.
Deep Cycle - Type of battery that can be discharged to
a large fraction of capacity many times without damaging the
battery.
Deep Discharge - Discharging a battery to 20 per cent
or less of its full charge.
Depth of Discharge (DOD) - The percent of the rated battery
capacity that has been withdrawn. See Battery State of Discharge.
Design Month - For the purpose of sizing a solar photovoltaic
system, it is necessary to choose a "worst month" for
which the system must meet the load requirements. This month
is termed the design month.
Diffuse Radiation - Solar radiation scattered by the atmosphere.
Top of Page Level II
Direct Current (DC) - The type of electricity stored in batteries
and generated by solar electric devices. Current flows in a single
direction. Opposite of alternating current (AC).
Direct Radiation - Solar radiation transmitted directly
through the atmosphere. Discharge The withdrawal of electrical
energy from a battery.
Drawdown - The distance below the natural water table
that the water-level in a well falls to when steady-state pumping
is in progress.
Dynamic Head - The head loss in pipes caused by the flow
of water through the pipes.
E Top
of Page Level II
Electrical Grid - An integrated system of electrical distribution,
usually over a large area.
Electrolyte - A liquid conductor of electricity. Electrolyte
is a conductive medium in which the flow of electricity takes
place; this is the liquid found inside storage batteries. It
is the medium that provides the ion transport mechanism between
the positive and negative electrodes of a battery.
F Top
of Page Level II
Fill Factor - The ratio of maximum output of a PV cell
under reference conditions to the product of open circuit voltage
and short circuit current, under the same conditions.
Flat Plate (Module or Array) - An arrangement of solar
cells in which the cells are exposed directly to normal incident
sunlight. Opposite of concentrator.
Float Charge - The third stage of three-stage battery charging.
After batteries reach full charge, charging voltage is reduced
to a lower level to reduce gassing (boiling of electrolyte) and
prolong battery life. This is often referred to as a maintenance
charge, since rather than charging a battery, it keeps an already-charged
battery from self-discharging.
Friction Head - The energy that must be overcome by the
pump to offset the friction losses of the water moving through
a pipe.
G Top
of Page Level II
Global Irradiance - The sum of diffuse and direct solar
irradiance incident on a horizontal surface.
Grid - When used in reference to utility power, it refers
to a system of electrical transmission and distribution lines.
Grid-Connected (PV system) - A PV system in which the
PV arrays act like central "generating plants" supplying
power to the grid. Either the PV system is operated by the utility
(in what is known as a grid-interactive system) or the individual
houses and other buildings in the grid are equipped with PV systems
that feed into the grid when they generate excess power. These
systems will draw from the grid at night and in periods of low
sunshine.
Ground Fault Protection (GFP) - A circuit protection
device that prevents the flow of electrical current to earth
if a short circuit is present. Usually required in wet locations- ex..
for outdoor, kitchen and bathroom circuits.
H Top
of Page Level II
Head - The height of water column that would produce the
pressure that the pump experience.
Hertz (Hz.) - The frequency, or number of times per second,
that the flow of AC electricity reverses itself. Also referred
to as cycles (see alternating current).
High Battery Protection - A control circuit that disconnects
charge current flowing to battery (s) when voltage reaches a dangerously
high threshold. Prevents damage created by excess gassing (or
boiling) of electrolyte. Top of Page Level
II
Hybrid PV System - A PV system that includes other sources
of electricity generation such as a generator (any gas powered
type such as diesel or NPG and/or micro-hydroelectric) or wind
generator.
Hydraulic Duty - The work that must be done to lift water,
expressed as hydraulic energy, or as a volume-head product.
Hydraulic Energy - The energy necessary to lift water.
Hydrometer - A simple device that measures the specific gravity
of battery electrolyte. Specific gravity readings express state
of charge/discharge of battery.
I Top
of Page Level II
Idle Current - The amount of electrical power required
to keep an inverter ready to produce electricity on demand.
Insolation - The solar radiation incident on an area over
time. Usually expressed in kilowatt-hours per square meter. Sunlight,
direct or diffuse.
Inverter - A device that converts direct current (DC)
to alternating current (AC). Top of Page Level II
Irradiance - The solar power incident on a surface. Usually
expressed in kilowatts per square meter. Irradiance multiplied
by time equals insolation.
IV Curve - A graphical presentation of the current versus
the voltage from a photovoltaic cells as the load is increased
from the short circuit (no load) condition to the open circuit
(maximum voltage) condition. The shape of the curve characterizes
cell or module performance. Three important points on the IV
curve are the open-circuit voltage, short-circuit current, and
peak power operating point.
J Top
of Page Level II
Jack Pump (Nodding Donkey) - Reciprocating pump in which
the motor is on the surface and the pump is down the well. Used
for high head applications.
K Top
of Page Level II
Kilowatt (kW) - One thousand watts of electricity.
Ten 100-watt light bulbs use one Kilowatt of electrical power.
Kilowatt hour (kW/h) - One kW of electrical power used
for one hour. The most common measurement of electrical consumption,
most grid connected electrical meters measure kW/h for billing
purposes.
L Top
of Page Level II
Life-Cycle Cost - The estimated cost of owning and operating
a system for the period of its useful life.
Light Emitting Diode (LED) - A device used to display various
status functions.
Line - That part of an electrical current from which live
power emanates and to which a load (or loads) is/are connected.
A line is the electrical wire that electricity travels in --
both the large power lines from your utility company and the
ones in your home or RV.
Line-Commutated Inverter - An inverter that is tied into
a power grid or line. The commutation of power (conversion from
AC to DC) is controlled by the power line, so that if there is
a failure in the power network, the PV system cannot feed power
into the line. Similar in function to the battery charge regulator.
Top of Page Level II
Line Loss - A voltage drop caused by resistance in wire during
transmission of electrical power over distance. Line loss is
the voltage drop over the length of electric line wire. This
robs your system of power when wire is too small for the load
being run through the line or when voltage is too low for the
distance the power must travel.
Line-tie - An electrical system that is connected to a
utility distribution grid. For example, Trace SW line-tie inverters
are designed to connect to and interact with utility power.
Load - Any device that consumes electricity in order
to operate. Anything in an electrical circuit which, when the
circuit is turned on, draws power from that circuit. Appliances,
tools, and lights are examples of electrical loads.
Low Battery Protection - A control circuit that stops
the flow of electricity from batteries to loads when battery
voltage drops to dangerously low levels.
M Top
of Page Level II
Maximum-Power-Point - The point on a current-voltage curve
where a PV device produces maximum power. This will be about
0.45 volts for a typical silicon cell.
Maximum Power Point Tracking (MPPT) - Every PV (solar electric)
device has a point where maximum current is delivered. MPPT electronically
adjusts the output PV-device output to the maximum power point.
Top of Page Level II
Modified Sine Wave - An AC wave form (generated by
many inverters) that is a pulse width modified square wave. It
consists of a number of very small on/off steps rather than a
fully smooth wave.
Multicrystalline Silicon - Silicon that has solidified
at such a rate that many small crystals (crystallites) were formed.
The atoms within a single crystallite are symmetrically arranged,
whereas the grouped crystallites are jumbled together. "Multi"
is used interchangeable with the word "Poly". Please
note that the use of "Multi" is somewhat more common
since "Poly" crystalline silicon is understood in the
microelectronics field to be the feed material which is melted
down to be regrown as ingots which are then sliced into silicon
wafers.
N Top
of Page Level II
National Electric Code - A consistent set of electrical
wiring and installation standards used in the United States.
O Top
of Page Level II
Off Grid - An electrical system that is not connected
to a utility distribution grid.
Ohm - A measure of resistance to the flow of an electric
current.
Open-Circuit Voltage - The voltage across a photovoltaic
cell in sunlight when there is no current flowing. It is the
maximum possible voltage.
Orientation - Placement with respect to the cardinal directions:
N, S, E, W. "Azimuth" is the measure of orientation
from the north.
Oscilloscope - A device that displays the wave form
created by an electrical generating device such as a generator,
inverter, or utility.
Overload/Overcurrent Protection - A control circuit
designed to protect an inverter or similar device from loads
exceeding its output capacity. (A fuse, for example, is an overcurrent
protection device.) All Trace inverters have internal circuitry
to protect themselves from overload/overcurrent conditions.
P Top
of Page Level II
Parallel Connection - A method of interconnecting two
or more electricity-producing, or power-using devices, such that
the voltage produced, or required, is not increased, but the
current is additive. Opposite of series connection.
Parallel Wiring - A group of electrical devices, such as
batteries or PV modules, wired together to increase ampacity,
while voltage remains constant. (Two 100 amp hour 12 Vdc batteries
wired in parallel will form a 200 amp-hour 12 Vdc battery bank.)
Peak Watt (s) (Wp) - The amount of power a photovoltaic
cell will produce at noon on a clear summer day with the sun
approximately overhead (insolation at 1000 watts/square metre)
when the cell is faced directly towards the sun.
Photovoltaic (PV) Array - An interconnected system of
photovoltaic panels that function as a single electricity-producing
unit. The panels are assembled as a discrete structure, with
common support or mounting. In smaller systems, an array can
consist of a single panel plus support structure or mounting.
Photovoltaic (PV) Cell - A device that converts light
directly into electricity. The building block of a photovoltaic
module.
Photovoltaic (PV) Module - A number of photovoltaic cells
electrically interconnected in either series or parallel and
mounted together, usually in a sealed unit of convenient size
for shipping, handling and assembling into panels and/or arrays.
The term "module" is often used interchangeably with
the term "panel". Top of Page Level II
Photovoltaic (PV) Panel - A group of modules fastened
together and wired in either series or parallel. The term "panel"
is often used interchangeably with the term "module".
Photovoltaic System - A complete set of components for
converting sunlight into electricity by the photovoltaic process
including array and balance of system components. These components,
which form a solar electric generating system, usually consist
of the charge controller, circuit protectors (fuses or breakers),
and batteries as well as the PV modules.
Photovoltaic (s) (PV) - This term pertains to the direct
conversion of light into electricity.
Plates - This refers to (a) metal plate (s) immersed in
the electrolyte inside a battery.
Polycrystalline Silicon - Silicon that has solidified
at such a rate that many small crystals (crystallites) were formed.
The atoms within a single crystallite are symmetrically arranged,
whereas the grouped crystallites are jumbled together. Top
of Page Level II
Positive Displacement Pump - A pump which moves water
by means of a cavity or cylinder of variable size. Also known
as a volumetric pump.
Power Conditioning Equipment - Electrical equipment used
to convert power from a photovoltaic array into a form suitable
for subsequent use. A collective term for inverter, converter,
battery charge regulator and blocking diode.
Progressive Cavity Pump - A positive displacement pump
that has a helical cavity between the rotor and stator. As the
rotor rotates, the cavity "progresses" upwards carrying
the water with it.
PV - Abbreviation for photovoltaic (s).
Pyranometer - An instrument used for measuring solar irradiance.
R Top
of Page Level II
Reciprocating Pump - A pump which is driven by a push/pull
motion rather than by rotation.
Remote - A solar electric or other alternative energy
system, including a hybrid source of power, which is not connected
to a utility grid.
Resistance - The opposition of a substance to the free
flow of electrons or electricity through it. Normally, this is
measured in units called "ohms".
Rotor - This refers to the rotating central section of
a motor or pump assembly.
S Top
of Page Level II
Semiconductor - Any material that has limited capacity
for conducting an electric current. Certain semiconductors, such
as silicon and gallium arsenide, are uniquely suited to the photovoltaic
conversion process.
Series Connection - A method of interconnecting devices
that generate or use electricity so that the voltage, but not
the current, is additive. The opposite of a series connection
is a parallel connection.
Series Wiring - A group of electrical devices, such as batteries
or PV modules, wired together to increase voltage, while ampacity
remains constant. (Two 100 amp hour 12 Vdc batteries wired in
series form a 100 amp hour 24 Vdc battery bank.) Top
of Page Level II
Short Circuit Current - The current flowing freely from
a photovoltaic cell through an external circuit that has no load
or resistance; the maximum current possible.
Sine Wave - The output wave form of an electric generator
or utility. A smooth wave going above and below zero is created.
This wave form is also produced by sine wave inverters such as
the Xantrex/Trace SW and Prosine series. Top of Page
Level II
Single-Crystal Silicon - A material formed from a single-silicon
crystal. Many PV cells are made from Single-Crystal Silicon.
Solar Irradiance - The power received per unit area from
the sun.
Specific Gravity - The ratio of the weight of the solution
to the weight of an equal volume of water at a specified temperature.
Used as an indicator of battery state of charge.
Stand-Alone (PV System) - An autonomous or hybrid photovoltaic
system which is not connected to a grid. It may or may not have
storage, but most stand-alone systems require batteries or some
other form of storage.
Stand-Off/Stand-Alone Mounting - Technique for mounting
a PV array on a sloped roof that involves mounting the modules
a short distance above the pitched roof and tilting them to the
optimum angle. Top of Page Level
II
Static Head - The height over which water must be pumped,
e.g. from the well level to a storage tank.
Stator - The outer, stationary component of pump assembly.
See "progressive cavity pump".
Storage - This term has a dual meaning for water pumping
systems. Storage can be either achieved by pumping water to a
storage tank or by storing energy in a battery subsystem.
String - A number of modules or panels interconnected
electrically to obtain the operating voltage required by the
load.
Suction Head - The vertical distance from the surface
of the water source to the center of the pump (when the pump
is located above the water level). Top of Page
Level II
Sun (One Sun, Peak Sun Hours, etc.) - This is the equivalent
number of hours per day when the solar irradiance averages 1000
Watts/m2. A value of 6 peak sun hours, for example, means that
the insolation received in one day is the same as if the sun
had shone for 6 hours at 1000 Watts/m2. Peak sun hours is a useful
measure when sizing photovoltaic systems since they are usually
rated in peak Watts.
Surge Capacity - The ability of an inverter or generator
to deliver high currents momentarily which is normally required
when starting an AC motor. In solar electric terminology, it
usually refers to the amount of current an inverter can deliver
for short periods of time. Most electric motors draw up to three
times their rated current when starting. An inverter will "surge"
to meet these motor-starting requirements. Most Trace inverters
have surge capacities at least three times their continuous ratings.
System Availability - The percentage of time (usually
in one year) that a PV system is in use.
T Top
of Page Level II
Telemetry - The remote measurement of any physical quality
(ex. geological seismic readings, meteorological conditions such
as windspeed and barometric pressure, electromagnetic forces,
etc.) using instruments and equipment which convert the measurement
into a transmittable signal for the purpose of data collection.
Temperature Compensation - An allowance made in a charge
controller's set points for changing battery temperatures.
Temperature Correction - A correction factor for battery
capacity when the battery is operating at temperatures lower
than 20°C.
Thin Film PV Module - A PV module constructed with sequential
layers of thin film semiconductor materials. See "Amorphous
Silicon".
Tilt Factor - The ratio of solar irradiation incident
on a tilted PV array to global irradiation (i.e. the degree of
incident angle). Due to the sun's positional variance throughout
the year (in the Northern Hemisphere, the sun is higher in the
summer), seasonal adjustment is advisable. Top
of Page Level II
Total Head - In water pumping, this is the sum of the
static and dynamic heads and drawdown.
Tracking Array - A PV array that follows the path of the
sun. This can mean a one axis tracking of the sun from east to
west daily or it can refer to a two-axis tracking where the sun's
elevation is also tracked.
Transfer Switch - A switch designed to transfer electricity
being supplied to loads (appliances etc.) from one source of
power to another. (A transfer switch may be used to designate
whether power to a distribution panel will come from a generator
or inverter.)
V Top
of Page Level II
Voltage, Volt, Volts (V) - A measure of the force or
"push" given the electrons in an electric circuit;
a measure of electric potential or the pressure in an electrical
circuit.. One volt produces one amp of current when acting against
a resistance of one ohm. Volts = Watts/Amps. Voltage is often
explained using a liquid analogy comparing water pressure to
voltage: a high pressure hose would be considered high voltage,
while a slow-moving stream could be compared to low voltage.
Volume-Head Product - The daily water volume multiplied
by the total head. The term is used as a measure of the hydraulic
duty; it is proportional to the hydraulic energy. Units are m4.
Volumetric Pump - A type of water pump that utilizes a
piston, cylinder, and stop valves to move water.
W Top
of Page Level II
Water Supply - Water supply for drinking and other
domestic purposes in rural communities. This may also include
some livestock watering or micro-irrigation (e.g. household vegetable
garden). Referred to in some publications as "rural water
supply".
Watt (s) - A quantitative measurement of electrical power.
Watts are calculated by multiplying volts times amps. Using a
liquid analogy, watts are similar to liquid flow such as liters
or gallons. (watts = volts x amps)
Watt-Hour (w/H) - A quantity of electricity. One watt
hour of electricity is consumed when one watt of power is used
for a period of one hour. Electrical power measured in terms
of time. (A one-watt light operated for one hour would consume
one watt hour of electricity.) Top of Page
Level II
Wattage - A measure of electric power (in watts "W")
or the amount of work done in a unit of time. One amp of current
flowing at a potential of one volt produces one watt of power.
Watts = Volts x Amps.
Waveform - The characteristic shape of an AC current or
voltage output.
Wp - See "Peak Watt" definition.
Copyright © 1991- 2006;
2007 Enviromart
Inc. All rights reserved. Information in
this document is subject to change without notice. No text, code,
or graphics herein may be copied for any purpose other than for
consumer viewing without the express written consent of Enviromart Inc. Other
products and companies referred to herein are trademarks or registered
trademarks of their respective companies or mark holders. Copyright
of individual articles is retained by the individual authors or
their assigns. Copyright of the compilation as a whole is held
by Enviromart Inc.
