Investor LoginA battery with a fiberglass mat which suspends the electrolyte between the
lead plates. The mat allows the battery to be used in many positions and assists the recombination of hydrogen and
oxygen into water after it is released from the electrolyte during charging.
Alternating Current (AC)
Electric current from the power utility, a generator or inverter which changes direction of flow at frequent intervals. In the Western Hemisphere this is 120 times per second (60 cycles or hz). Most of the rest of the world operates on 50 cycles.
Amorphous
Having an atomic structure that is not periodic.
Amoprhous Silicon
A non-crystaline semiconductor material that is used in "thin-film" photovoltaic modules such
as those made by Uni-Solar and some of the earlier Solarex modules. The doped silicon is sprayed onto a sub-strate
such as glass or stainless steel. This type of module uses less photovoltaic grade silicon than a single or multi-crystal
module and also allows for a flexible panel with a metal or synthetic backin. They also will produce power in lower light
conditions than conventional modules.
Ampere (A) or Amp
The unit for electric current as in the flow of electrons. Describes the quantity of electrons passing
a point in one second. It will often be shown on a photovoltaic module label as "I" for intensity.
Ampere-Hour (AH)
The quantity of electrical energy equal to the flow of one ampere of current for one hour. Deep cycle storage battery capacity is often rated in amp hours.
Array
A number of photovoltaic modules wired together with a single output.
Autonomous System
A photovoltaic system that is stand-alone and has no backup power source. These usually incorporate a battery bank for power storage.
Balance of System
The items in a photovolaic system, with the exception of the pv modules themselves, that make
up a complete system.
Battery
Two of more cells connected together to store electricity.
Battery Capacity
The number of amp-hours that a battery can store.
Battery Cycle Life
The number of charge and dis-charge cycles a battery can endure before it is no longer useful. This is based on a specific depth of dis-charge (drawing the battery down to a given amp-hour capacity remaining.) The more the battery is drawn down before recharging, the lower the number of charge/dis-charge cycles that will be left.
Blocking Diode
In the "Olden Days" most photovoltaic charge controllers were either on/off or diversion types. At night power could drain from the batteries back into the photovolaic modules. The modules would actually glow (when viewed with light amplification equipment) like a huge led light. In those instances a blocking diode (or one-way electrical gate), usually a Schottky diode, was used to prevent this. Todays charge controllers either have a built-in diode or automatically disconnect the modules from the battery bank at night.
BOS or Balance of System (photovoltaic)
The parts of a photovoltaic system other than the array. For instance: switches, controls, meters, power conditioning equipment, supporting structure for the array, storage components, etc.
By-Pass Diode
PV modules can be connected in a series string (positive to negative) to increase voltage. If one of the
modules is shaded, the output from the other modules in that series string can feed into that shaded module causing damageor a fire. When the modules have a by-pass diode in the junction box that dioded will pass the power through without allowing it to go into the cells of the shaded module. Once the shading is removed, the diode has a higher resistance than the cells in the module and the module starts producing power again. UL Listed modules will show a maximum series string voltage which the by-pass diode in the module can handle.
Cell
The basic unit of a pv module or battery. In a pv module the cell produces around 0.45 to 0.5 volt, the more cells the higher the voltage. A lead acid battery cell produces about 2.0 volts (a 12 volt battery will have 6 cells.)
Charge Controller
This is placed between the alternative energy power source and the battery bank to prevent over-charging.
Charge Monitor/Meter
A device that displays the level of charge in a battery.
Charge Rate
The rate in amp hours of charging current supplied to a battery.
Charge Regulator
A device that controls the changing rate and/or state of charge for batteries. Wired between a photovoltaic array and a battery bank. Its main job is to prevent the battery from being overcharged from the PV array, while monitoring the array and/or battery voltage.
Compact Fluorescent Lamp (CFL)
Fluorescent lights which have an Edison (screw-in) base and use either short looped or spiral fluorescent tubes.
Components
Refers to other devices used and needed when building a solar system.
Converter
An electronic device that changes a DC voltage to some other DC voltage. For example, a converter may be used to convert the output of a 24-volt device to a 12-volt output.
Crystalline
Having a repeating atomic structure in all three dimensions.
Crystalline Silicon
A pv cell made of either a single crystalline or poly crystalline structure which have a controlled direction of the crystals. An Amorophous structure has random patterns and directions.
Current
The flow of electricity (electrons) between two points having a difference in potential (voltage.)
Current at Maximum Power (Imp)
The current rating of a pv module when the maximum power (watts) is being produced.
Days of Autonomy
The number of days a stand-alone system can power loads without incoming power from pv module input.
DC to DC Converter
A device which takes a direct current voltage and either steps it up or steps it down.
Deep Cycle Battery
A battery which is designed (usually with thick plates) to withstand being drawn down to a low state of charge
and still being able to be recharged.
Diode
A one-way electrical gate which allows current to travel in one direction only.
Direct Current
Electric current which travels in one direction only, such as that produced by a pv module or storage battery.
Discharge Rate
Usually shown in amp-hours (amps over time) which shows how much current is being taken from a battery.
Disconnect
Also a safety disconnect. A circuit opening device which can be placed between an alternative energy power source
and the charge controller, between the charge controller and batteries, as well as between the batteries and the loads.
Disordered
The atoms are not arranged in a repetitive periodic fashion.
Efficiency
This is the ratio of power put in verses power outputted. Usually shown as a percentage.
Electrical Circuit
The pathway from the power source to the load.
Electrical Grid
The system of power distribution from power generating plants to the customers. Usually operated by a public
utility company.
Electrolyte
The liquid in a storage battery. In a lead acid battery it is composed of water and sulfuric acid.
Energy
The ability to do work - it is usually measured in watts.
Energy Density
The ratio of energy available in a battery (storage device) to the mass or weight of the battery.
Equalization Charge: Intentionally over-charging a battery for short periods of time at a higher than normal voltage to help mix up the acid and water in the electrolyte and equalize, or balance, the cells in a battery.
Float Charge
This is a light maintenance charge to offset the battery losses caused by self-dischage in storage.
Float Life
This is the number of years a battery will retain its stated amp hour capacity when kept at a float charge.
Gassing Current
A portion of the charging current which is consumed by the electrolytic breakdown of the water into oxygen and hydrogen during charging.
Gel Battery or Gel Cell
A sealed battery where the electrolyte is captured in a silica gel.
Grid-Tie
An alternative energy system that output alternating current into the building's wiring. Any power not used will feed into the electrical grid.
Grid-Connected (photovoltaic)
A photovoltaic system in which the PV array supplies power directly to a load center (i.e. AC Service Panel) in a home or commercial facility. There is no on-site storage device included with a grid-connected photovoltaic system. Instead, all the kilowatt-hours generated by the PV system are either used by the loads connected to the load center in the building or they are pulled into the utility grid power lines via the utility kilowatt-hour meter attached to the building.
Hybrid System
A power generating system that has more than one power source such as: photovoltaic, wind, hydro or an auxillary generator.
Insolation
Sunlight, either direct or reflected which is usually measured in watts per square meter. Used to determine
the available sunshine in a given location for sizing a photovolatic system.
Interconnect
Wired connections between solar cells as well as between photovoltaic modules.
Inverter
A device which converts direct current from a battery (or photovoltaic modules in a grid-tie system) into
120 or 240 volt a.c.
Junction Box
An electrical enclosure where wiring circuits are connected. On the back of a pv module this is
commonly referred to as the "J" box.
Kilowatt
One thousand watts.
Kilowatt Hour
On thousand watt hours (i.e. 1000 watts either produced or consumed in an hour.)
Life Cycle Cost
The total system cost from the time of installation to the time it heads to the bone yard.
Load
Anything that draws power from a circut (i.e. lights, fan, radio, etc.)
Maximum Power Point Tracker (MPPT)
A charge controller that operates a pv array at its maximum power point voltage/amperage.
Megawatt
One million watts.
Module (photovoltaic)
PV modules are manufactured and assembled using solar cells, interconnect wire, bypass diodes, encapsulant (which is a top cover over the solar cells) and a protective back sheet behind the solar cells. Most solar modules also include a frame around the edges of the back sheet/top cover assembly. Together, all of these components form the solar PV module.
Mulitcrystalline
Photovoltaic cells that have semi-random orientation of the structure. They look like broken sheets
of colored glass.
NEC
National Electrical Code. Sets standards for electrical installations - article 690 of the code refers to pv systems.
Nominal Operating Cell Temperature (NOCT)
A reference temperature (usually 25 degrees C) for basing the output voltage and amperage of a pv cell or module. Some modules show both a NOCT on the sticker for both 25 degrees C and 45 degrees C. The higher temperature will have lower outputs.
Nominal Voltage
The reference voltage for describing battery, pv modules and systems (i.e. 12, 24 or 48 volt.) A 12 volt system usually operates from 12 to 14.5 volts.
Ohm
A unit of measurement dealing with the resistance to flow of electrons through a circuit.
One Axis Tracking
A pv system where the modules track the sun from East to West and return to East in the morning.
Open Circuit Voltage
The highest possible voltage a pv cell or module will produce when in full sun and without being
connected to a load.
Orientation
Aiming the pv module(s) to a compass heading, usually to true South in the Northern Hemisphere.
Parallel Connection
Connecting two or more electrical producing devices, such as pv modules, or storage devices, such as batteries, so the the capacity (amperage or amp/hours) increases but the voltage remains the same. This is done by connecting positive to positive and negative to negative.
Peak Load / Peak Demand
The most power consumed at a given moment in the day.
Peak Power
Maximum power rating for some particular device.
Peak Sun Hours
The number of hours in the day when solar irradiance (or insolation) averages 1000 watts per square meter - also known as full sun.
Photovoltaic (PV)
Refering to the direct conversion of light into electricity.
Photovoltaic Array
Connecting of one or more pv module(s) so they act as one electricity producing unit.
Photovoltaic Cell
The treated semiconductor material that converts solar irradiance to electricity.
Photovoltaic Module
A series of photovoltaic cells mounted in a self-contained package, also known as
a solar panel.
Photovoltaic System
A complete assembly from the pv module(s) to the power consuming loads.
Polycrystalline
Photovoltaic cells that have semi-random orientation of the structure. They look like broken sheets of colored glass.
Pulse-Width-Modulated Charge Controller
This is placed between the pv module(s) and the batteries. It operatesby allowing different width and different heights of voltage spikes to flow into the battery from the pv power source.
PV
PhotoVoltaic.
Remote Site
A location where the only power available is that which is produced on-site.
Resistance
The property of a conductor or electrical device to oppose the flow of electrons.
Roll-to-Roll Process
A process where a roll of substrate is continuously converted into a roll of product.
Series Connection
Connecting two or more electrical producing devices, such as pv modules, or storage devices,
such as batteries, so the the voltage increases but the capacity (amperage or amp/hours) remains the same. This is
done by connecting positive to negative and so on.
Short Circuit Current (Isc)
The current (amps) flowing from a pv cell or module through a circuit that has no load or
resistance - the highest possible current.
Shunt Regulator
A photovoltaic charge controller that shorts out the pv module when the battery is charged.
Silicon
The primary material in most photovoltaic modules. Commonly found in sand and quartz.
Sine Wave Inverter
A dc to ac inverter which produces alternating current (usually 120 volt a.c. in the Western Hemisphere)
that is of the same wave form as that delivered by the utility company. Also known as a pure or true sine-wave inverter.
Single Crystal Material (pv cell)
A pv cell where the crystal orientation is in the same direction. With current technology these
are the most efficient, as well as the most expensive to manufacture.
Solar
Energy from the sun.
Solar Cell
An eary term for a photovoltaic cell which is the building block of a pv module.
b]Solar Collectors[/b]
A device designed to capture light or heat energy from the sun. Solar thermal collectors are used in solar hot water systems (often found in homes) and photovoltaic collectors are used in solar electric systems
Solar Constant
The strength of sunlight which is about 1000 watts per square meter at sea level at the equator.
Solar Energy
Energy from the sun.
Solar Grade Silicon
A grade of silicon which is used to manufacture photovoltaic cells.
Solar Heating
Technologies or systems that take advantage of the heat energy coming from the sun. Solar thermal collectors are used in solar hot water systems (often found in homes) and photovoltaic collectors are used in solar electric systems.
Solar Panel
Another name for a single module or a group of solar modules that are part of a solar electric PV system (syn: solar array).
Square Wave Inverter
These are the earliest d.c. to a.c. inverters. Instead of producing a curved waveform like a sine wave
inverter, these produce a very low grade and inefficient form which is flatten (square) at the top and bottom.
Stabilized Energy Conversion Efficiency
The long-term ratio of electrical output to light input.
Staebler-Wronski Effect
The nature of amorphous (thin-film) photovoltaic devices is that they can lose up to 10% of their
output in the first year of being exposed to light. This is why manufacturers under-rate the output on the pv module label (it showsthe output after the first year) and why the controll and protection devices in a pv system have to be up-sized to handle the output of the pv modules for the first year.
Stand-Alone System
A system that relies on power produced by itself with no incoming power from the utility grid.
Stand-Off Mounting
This is when pv modules are roof mounted a few inches from the roof surface and tilted at the optimum angle for the site latitude. This also allows the back of the modules to cool which helps maintain output voltage.
Standard Test Conditions
When pv module output is measured for the labelling they are tested in a controlled laboratory.The irradiance (light source) supplies the standard 1000 watts per square meter and the temperature is 25 degrees C.
State of Charge
The available "useable" capacity remaining in a battery. This is usually measured in percent. In theory, a 100 amp hour battery that has had 50 amp hours removed from it would have a 50% state of charge.
Sulfation
A lead-acid battery has lead plates and an electrolyte composed of water and sulfuric acid. As the battery
discharges the sulfuric acid migrates into the lead plates. If it is allowed to remain in the plates sulfate crystals form on the surface and insulate the lead from the electrolyte. This can permanently reduce the storage capacity of the battery.
Superstrate
This is the top covering of the pv cells in a pv module. It is usually low-iron tempered glass but can also be a flexible synthetic material.
Surge or Surge Rating
When an electric motor is first started it requires a greater amount of amperage than the name
plate rating. This is because the motor has to overcome the inertia of the moving parts at rest and get them moving.
Surge Capacity
This is the ability of an inverter or generator to output a higher power than the name plate rating for a
few seconds to start an electric motor.
Systems; Balance of Systems
Solar electric systems include the photovoltaic array and the other components that allow these solar panels to be used in homes and commercial facilities where a regulated DC power supply or an AC power supply is required. Components used in solar electric systems include; wire and disconnect devices, charge regulators, inverters, metering, and grounding components.
Temperature Compensation
This is the ability of a charge controller to adjust the voltage going into a battery to allow
for higher or lower than normal battery temperature.
Thin-Film
A non-crystaline semiconductor material that is used in "thin-film" photovoltaic modules such
as those made by Uni-Solar and some of the earlier Solarex modules. The doped silicon is sprayed onto a sub-strate
such as glass or stainless steel. This type of module uses less photovoltaic grade silicon than a single or multi-crystal
module and also allows for a flexible panel with a metal or synthetic backin. They also will produce power in lower light
conditions than conventional modules.
Tilt-Angle
This is the angle of a pv module in relation to level which will orient it as close as possible to being perpendicular
to the sun for maximum power production.
Volts
The unit of electromotive force that will force a current of one amp through a resistor or one ohm.
Voltage
The measurement of the force of electricity.
Watts
A measure of electrical power that is determined by multiplying the voltage by the amperage.
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