absorbed glass mat (AGM): A fibrous silica glass mat to suspend the electrolyte in batteries. This mat provides pockets that assist in the recombination gasses generated during charging back into water.

alternating current (AC): Electric current in which the direction of flow is reversed at frequent intervals, usually 100 or 120 times per second (50 or 60 cycles per second or 50//60 Hz).

amorphous silicon: A non-crystalline semiconductor material that has no long-range order, often used in thin-film photovoltaic modules.

ampere (A) or amp: The unit for the electric current; the flow of electrons. One amp is 1coulomb passing in one second. One amp is produced by an electric force of 1 volt acting across a resistance of 1 ohm. Sometimes this is abbreviated as I for intensity.

ampere-hour (Ah): Quantity of electrical energy equal to the flow of one ampere of current for one hour. Typically used to quantify battery bank capacity.

array: Any number of photovoltaic modules connected together to provide a single electrical output at a specified voltage. Arrays are often designed to produce significant amounts of electricity.

autonomous system: A standalone PV system that has no backup generating source.  May or may not include storage batteries.

avoided cost: The minimum amount an electric utility is required to pay an independent power producer, under the PURPA regulations of 1978, equal to the costs the utility calculates it avoids in not having to produce that power (usually substantially less than the retail price charged by the utility for power it sells to customers)
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balance of system (BOS): All system components and costs other than the PV modules, including inverters, mounting structures, disconnects, wire and conduit.

battery: Two or more “cells” electrically connected for storing electrical energy. Common usage permits this designation to be applied also to a single cell used independently, as in a flashlight battery. battery capacity: The total number of ampere-hours that can be withdrawn from a fully charged cell or battery.

battery cycle life: The number of cycles, to a specified depth of discharge, that a cell or battery can undergo before failing to meet its specified capacity or efficiency performance criteria.

battery self-discharge: The rate at which a battery, without a load, will lose its charge.

battery state of charge: Percentage of full charge, or100 percent minus the depth of discharge.

bypass diode: A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the cell(s) become reverse biased.  Alternatively, a diode connected anti-parallel across a part of the solar cells of a PV module. It protects these solar cells from thermal destruction in case of total or partial shading of individual solar cells while other cells are exposed to full light.
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cell: The basic unit of a photovoltaic module. This word is also commonly used to describe the basic unit of batteries (i.e., a 6-volt battery has three 2-volt cells).

charge controller: A device that controls the charging rate and/or state of charge for batteries.

charge rate: The current applied to a cell or battery to restore its available capacity. compact fluorescent lights (CFL): Lights that use a lot less energy than regular light bulbs We can use compact fluorescent lights for reading lights and ceiling lights.

crystalline silicon: A type of PV cell made from a single crystal or polycrystalline slice of silicon.

current: The flow of electric charge in a conductor between two points having a difference in potential (voltage).

current at maximum power (Imp): The current at which maximum power is available from a module. [UL 1703]

cycle life: Number of discharge-charge cycles that a battery can tolerate under specified conditions before it fails to meet specified criteria as to performance (e.g., capacity decreases to 80-percent of the nominal capacity).
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days of autonomy: The number of consecutive days a standalone system battery bank will meet a defined load without solar energy input.

DC to DC converter: Electronic circuit to convert DC voltages (e.g., PV module voltage) into other levels (e.g., load voltage). Can be part of a maximum power point tracker ( MPPT).

deep cycle battery: Type of battery that can be discharged to a large fraction of capacity many times without damaging the battery.

depth of discharge (DOD): The amount of ampere hours removed from a fully charged cell or battery, expressed as a percentage of rated capacity.

diode: Electronic component that allows current flow in one direction only.
direct current (DC): Electric current in which electrons flow in one direction only. Opposite of alternating current.

discharge rate: The rate, usually expressed in amperes over time, at which electrical current is taken from the battery.

disconnect: Switch gear used to connect or disconnect components of a PV system or DC or AC systems for safety or service.

duty cycle: The ratio of active time to total time. Used to describe the operating regime of appliances or loads.
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edge-defined film-fed growth (EFG): A method for making sheets of polycrystalline silicon in which molten silicon is drawn upward by capillary action through a mold.

edge of cloud effect (EGE):

efficiency: The ratio of output power to input power. Expressed as a percent.

electric circuit: Path followed by electrons from a power source (generator or battery) through an external line (including devices that use the electricity) and returning through another line to the source.

electric current: A flow of electrons; electricity.

electrical grid: An integrated system of electricity distribution, usually covering a large area; most typically in the USA, owned and operated by a public utility.

electrolyte: A liquid conductor of electricity in which flow of current takes place by migration of ions. The electrolyte for a lead-acid storage cell is an aqueous solution of sulfuric acid.

energy: The ability to do work. Stored energy becomes working energy when we use it. energy density: The ratio of energy available from a battery to its volume (Wh/1) or mass (Wh/kg).

equalization: The process of mixing the electrolyte in batteries by periodically overcharging the batteries for a short period to “refresh” cell capacity.
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float charge: Float charge is the voltage required to counteract the self-discharge of the battery at a certain temperature.

float life: Number of years that a battery can keep its stated capacity when it is kept at float charge.
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gassing current: Portion of charge current that goes into electrolytical production of hydrogen and oxygen from the electrolytic liquid in the battery. This current increases with increasing voltage and temperature.

gel-type battery: Lead-acid battery in which the electrolyte is composed of a silica gel matrix.

gigawatt (gW): One billion watts. One million kilowatts. One thousand megawatts.

grid-tie: A PV, wind or hydroelectric systems that supplies power directly to the utility grid. Also called grid-connected, grid-interactive, utility-intertie and other similarly descriptive terms.
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hybrid system: A PV system that includes other sources of electricity generation, such as wind or fossil fuel generators.
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insolation: Sunlight, direct or diffuse; from ‘incident solar radiation.’ Usually expressed in watts per square meter. Not to be confused with ‘insulation.’
interconnect: A conductor within a module or other means to provide an electrical connection between the solar cells.

inverter: Device that converts DC electricity into AC electricity (single or multiphase), either for off-grid standalone systems or for grid-tie systems.
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junction box (J Box): An electrical box designed to be a safe enclosure in which to make proper electrical connections. On PV modules this is where PV strings are electrically connected.
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kilowatt (kW): 1000 watts.

kilowatt-hour (kWh): One thousand watt-hours. The kWh is a unit of energy. 1 kWh=3600 kJ. life cycle cost: An estimate of the cost of owning and operating a system for the period of its useful life; usually expressed in terms of the present value of all lifetime costs.
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load: Anything in an electrical circuit that, when the circuit is turned on, draws power from that circuit.
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maximum power point tracker (MPPT): Means of a power conditioning unit that automatically operates the PV generator at its MPP under all conditions.

megawatt (MW): One million watts; 1000 kilowatts.

module: See ‘photovoltaic module.'

modified sine-wave inverter: See 'modified square-wave inverter.'

modified square-wave inverter: These inverters produce a square-wave that has been modified thus providing a better signal then the square-wave inverters.

multicrystalline: Material that is solidified at such as rate that many small crystals (crystallites) form. The atoms within a single crystallite are symmetrically arranged, whereas crystallites are jumbled together. These numerous grain boundaries reduce the device efficiency. A material composed of variously oriented, small individual crystals. (Sometimes referred to as polycrystalline or semi-crystalline).
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NEC: An abbreviation for the National Electrical SKU which contains safety guidelines and required practices for all types of electrical installations. Article 690 pertains to solar photovoltaic systems.

nominal operating cell temperature (NOCT): The reference cell (module) operating temperature presented on manufacturer’s literature. Generally the NOCT is referenced at 25°C, 77°F.

nominal voltage: A reference voltage used to describe batteries, modules, or systems (i.e., a 12-, 24-, or 48-volt battery, module or system).
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ohm: The unit of resistance to the flow of an electric current.

one-axis tracking: A system capable of rotating about one axis, also referred to as single axis. These tracking systems usually follow the sun from east to west throughout the day.

open-circuit voltage (Voc): The maximum possible voltage across a photovoltaic cell or module; the voltage across the cell in sunlight when no current is flowing.

orientation: Placement according to the compass directions, north, south, east, west.
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parallel connection: A way of joining two or more electricity-producing devices such as PV cells or modules, or batteries by connecting positive leads together and negative leads together. Such a configuration increases the current but the voltage is constant.

peak load; peak demand: The maximum load, or usage, of electrical power occurring in a given period of time, typically a day.
 

By keeping your batteries at least 80% charged will greatly reduce this process.  Also, the use of a battery desulfator will help prolong your batteries strength.

superstrate: The covering on the sun side of a PV module, providing protection for the PV materials from impact and environmental degradation while allowing maximum transmission of the appropriate wavelengths of the solar spectrum.

surge: Is a momentary large spike in current (amperage) that is required by an electric motor in order to get it started.  Once the motor has started the amperage will resume its normal use level.

When sizing your inverter it is important to take into consider your surge loads.  It is important to remember that this includes all your pumps, electric tools, and your refrigeration units as well.  Even though not all these items will be starting at once, you need to make an educated guess as to what will be used. 

Is the momentary start-up condition of an electric motor requiring a large amount of current.

surge capacity: The ability of an inverter or generator to deliver high currents momentarily required when starting a motor.
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temperature compensation: An allowance made in charge controller set points for changing battery temperatures.

thin film: A layer of semiconductor material, such as copper indium diselenide, cadmium telluride, gallium arsenide, or amorphous silicon, a few microns or less in thickness, used to make photovoltaic cells.

tilt angle: Angle of inclination of a module as measured in degrees from the horizontal.  For maximum performance solar collectors/modules should be set as close as possible to perpendicular to the sun.

total harmonic distortion (thd): The measure of closeness in shape between a waveform and its fundamental component.

tracking PV array: PV array that follows the path of the sun to maximize the solar radiation incident on the PV surface. The two most common orientations are (1) one axis where the array tracks the sun east to west and (2) two-axis tracking where the array points directly at the sun at all times. Tracking arrays use both the direct and diffuse sunlight.  Two-axis tracking arrays capture the maximum possible daily energy.

transformer: An electromagnetic device used to convert AC electricity, either to increase or decrease the voltage.

trickle charge: A charge at a low rate, balancing through self-discharge losses, to maintain
a cell or battery in a fully charged condition.

two-axis tracking: A system capable of rotating independently about two axes and following the sun’s orientation and height in the sky (e.g., vertical and horizontal).
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utility-interactive inverter: An inverter that can function only when tied to the utility grid, and uses the prevailing line-voltage frequency on the utility line as a control parameter to ensure that the PV system’s output is fully synchronized with the utility power.
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VAC: Volts AC.

VDC: Volts DC.

Voc: Open-circuit voltage (seen entry).

volt (V): A unit of measure of the force, or ‘push’, given the electrons in an electric circuit.  One volt produces one amp of current when acting against a resistance of one ohm.

voltage at maximum power (VMP): The voltage at which maximum power is available from a module.
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wafer: A thin sheet of semiconductor material made by mechanically sawing it from a single-crystal or multi-crystal ingot or casting.

watt (W): The unit of electric power, or amount of work. One ampere of current flowing at a potential of one volt produces one watt of power.

watt-hour (Wh): A quantity of electrical energy when one watt is used for one hour.

waveform: The shape of the curve graphically representing the change in the AC signal voltage and current amplitude, with respect to time.

wire: A conductor which is used to connect electrical components to each other.  Proper wire size is important to prevent voltage loss during transmission.  Use this wire chart to determine wire size.
 

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