nielniel Solar Expert Posts: 10,300 ✭✭✭✭
This is only meant as a rough guide to these words and their meanings in relation to helping some understand some of the applied terminology and it is the responcibility of the reader to verify the accuracy of the words and the definitions so no liability is expressed or implied from the forum or its members. note that this is a joint effort with general member input given for it. to keep clutter down and readability high, comments in this thread may be modified or deleted at any time and we ask that those comments be pertinent when made here.

AGM: Absorbed Glass Mat. Also sometimes called 'starved electrolyte'. A type of lead-acid battery whose electrolyte is contained within a glass mat. It is therefor an SLA, but not an FLA.
Amp: Ampere; unit of measurement for electric current named for André-Marie Ampère.
Amp Hour (Amp/hr or Ah): The current potential of a battery or battery bank in reference to an hour. Usually measured by the "20 hour rate" standard.
Array or PV Array: A group of two or more PV's connected in series or parallel for additional Voltage or Amperage.
Battery Bank: A group of two or more batteries connected in series and or parallel to increase Voltage or Amp Hour capacity. See also:
Battery Capacity: The Amp Hour rating of a battery or battery bank, usually in reference to a 20 hour rate of discharge where the ah capacity is equally divided, to the point of being dead at 10.5 volts for a 12 Volt (nominal) battery. For a 20 hour rate example, a 100 Amp Hour battery would be discharged at 100AH/20Hrs=5 Amps being drawn over 20 hours.
Battery Meter or Battery Monitor: A device for measure the charge state of the battery as best possible based on Voltage levels and current flow in and out of the battery.
Battery Temperature Sensor (BTS), a.k.a. Remote Temperature Sensor (RTS): A wired probe onto a battery for the purpose of detecting the temperature of the battery so that a connected device such as a charge controller or an inverter can make necessary changes in reference to the battery charge voltage.
Charge Controller (CC): An electronic regulator for controlling/converting array output to charge batteries. See also:
Deep Cycle: Battery capable of being repeatedly drawn down 50%-80% of charge and re-charged to ~100%.
Depth Of Discharge (DOD): Amount of power drained from a battery during usage and expressed as a percentage of the battery's total capacity adding that it is the reciprocal of SOC. 100% DOD = DEAD, 0% DOD = FULL.
DMM, (Digital Multimeter): An electronic instrument used to measure various electrical parameters such as voltage, current, and resistance.
DVM, (Digital Voltmeter): An electronic instrument used to measure voltage only.
Electrolyte: Conductive fluid in a battery. It is comprised mainly of sulfuric acid.
Feed-in Tariff: A guaranteed payment usually with the force of law for each kwh you generate and feed into the grid.
FLA: Flooded Lead Acid. Generic term for 'wet cell' batteries. On this Forum, usually refers to Deep Cycle cells suitable for Renewable Energy.
Gel or Gel Cell: A type of battery whose electrolyte is contained in a gelatinous substance.
Grid: The distribution network for utility supplied power. Usually in reference to Grid-Tie.
Grid-Tie Inverter (GT): As defined for inverter, but specifically designed to feed AC to an active utility grid. Some versions also have battery back-up capability.
HAWT: Horizontal Axis Wind Turbine.
Hydrometer: A device for measuring the Specific Gravity (SG) of a fluid, as in battery electrolyte.
Imp: Current at maximum power. The most Amps a solar panel will produce under normal operating conditions. The "I" comes from an old term for current; Intensity.
Inverter: A device for changing DC Voltage into AC Voltage. See also:
Inverter/charger: As defined for Inverter, but with utility or generator input for a built-in supplemental battery charger.
Isc: Current under short-circuit conditions. The peak current a solar panel can produce with its output shorted. Used for calculating wire size and circuit protection ratings. The "I" comes from an old term for current; Intensity.
Kilowatt (kW): One thousand Watts.
Kilowatt hour (kW hour or kWh): One thousand Watt hours.
Load: On this forum, a reference to 'end use' devices such as lights, refrigerators, et cetera. Anything that consumes electrical power.
Micro-hydro or Micro-hydro Turbine: Electro-mechanical device for generating electricity from flowing water.
MPPT: Maximum Power Point Tracking. A type of Charge Controller method that adjusts its output to achieve the most efficient charge rate possible from varying input Voltage. Some are able to change the higher PV Voltage into a lower System Voltage we refer to as down-converting.
MSW: "Modified Sine Wave". Correctly, Modified Square Wave. Refers to an inverter whose output waveform is incremental square-wave 'steps' that 'mimic' a sine wave. While usually less expensive than Sine Wave inverters, they have limitations in that some devices do not work properly or at all.
Ohm: Unit of electrical resistance named for Georg Simon Ohm.
Power Factor (PF): The ratio of real power (Watts) to apparent power (Volt-Amperes). PF = W/V-A. Although important to the efficiency of a load (and thus to conservation) this information is rarely included in manufacturer's specifications and must be measured by the user. Loads of a purely resistive type (heaters, incandescent bulbs) will have a PF of 1.0. Loads that include inductive or capacitive elements will have a lower PF.
PV: Photovoltaic (electric solar panel). Converts sunlight into electricity.
PWM: Pulse Width Modulation. A type of Charge Controller method that 'pulses' its output as needed to charge and then maintain battery Voltage.
Renewable Energy (RE): A reference to natural sources of power that are non-polluting in the act of generating the power.
Resistance: A.K.A. ohmic resistance, a property of a conductor by virtue of which the passage of current is opposed, causing electric energy to be transformed into heat equal to the voltage across the conductor divided by the current flowing in the conductor: usually measured in ohms.
RV/Marine "Deep Cycle": A 'hybrid' battery design whose plates are a combination of the thick 'true' Deep Cycle and the more porous SLI type. Not the best choice for Renewable Energy applications, but better than an SLI.
Shunt: A device with known, fixed, temperature-stable resistance wired in series between batteries and inverter to facilitate the use of a Battery Meter. It allows a small, proportional amount of current to flow through the meter, enabling it to register the total current flowing to or from the batteries.
SLA: Sealed Lead Acid. As FLA, but without the ability to open and inspect cells through 'caps'. Technically, AGM's are a type of SLA.
SLI: Starting, Lighting, and Ignition. Standard 'automotive' type battery. Not really suitable for Renewable Energy use.
Specific Gravity (SG): A weight ratio comparing one to another. In the case of lead acid batteries it is the ratio of the electrolyte made up of sulfuric acid and water compared to straight water. The higher the ratio, the more the acid in the electrolyte.
State Of Charge (SOC): Amount of power available from a battery at any given point in its usage cycle and expressed as a percentage of the battery's total capacity adding that it is the reciprocal of DOD. 100% SOC = FULL, 0% SOC = DEAD.
Sine Wave: aka, TSW and PSW. Refers to an inverter whose output waveform is close to that of an ideal sine wave by having its total harmonic distortion under 5%, the same as found on utility grid power or from a generator. Some refer to these Sine Wave inverters as True Sine Wave (TSW) or Pure Sine Wave (PSW), but that is a bit of a misnomer as the waveform is not true or pure.
Tracker, Solar Tracker, or Tracking Mount: a mounting for a PV Array which 'follows the sun', keeping the array in best possible alignment with solar radiation. There are two basic types: single axis, which follows the sun's movement through the day, and dual axis, which also adjusts for different angles per the time of year.
Tubular Plate Battery: Deep cycle battery used chiefly in Europe for renewable energy and backup applications. For stationary applications, if the batteries are of the flooded lead acid type, they are called "OPzS", while VRLA versions are called "OPzV". When used in forklifts and other mobile applications the batteries are called "PzS".
VAWT: Vertical Axis Wind Turbine.
Vmp: Voltage at Maximum Power. The output Voltage of a PV when it is at its maximum current.
Voc: Voltage Open Circuit. The output Voltage of a PV under no load.
Volt: Unit of electrical potential named for Alessandro Volta.
VRLA: Valve Regulated Lead-Acid. A type of SLA.
Watt: Unit of electrical power named for James Watt.
Watt hour (Wh): Quantity of electrical power as in one Watt used for one hour or any mathematical equivalent.
Wind Generator or Wind Turbine: Electro-mechanical device for generating electricity from moving air current.

Suggestions for additions to the Glossary may be made via PM to a Moderator.


  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Glossary

    i have to mention that our host has put up a glossary of terms as well.
    here is the link to it.
  • drraptordrraptor Solar Expert Posts: 218 ✭✭

    Please post all the common Terms, definitions and Formulas a newbie should know e.g

    Calculating Load in WH
    Power rating (watts) * Number of hours the appliance is used (hours) = WH

    Battery Bank calculation

    Wh * 1/Battery voltage * Number of days of storage * 1/maximum discharge = Ah @ Battery Voltage

    Array required for Charging a certain battery bank

    Ah * Charging Voltage * 1/0.77 panel+controller derating * % rate of charge (in fraction) = Watts, array size

    Definitions e.g
    Array: ??

    Terms e.g
    Panel wattage rating, how it is calculated etc.
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Re: Glossary

    OK, I have copied your post over to this thread.

    You asked:

    Diversion Load: A load which "must be used" to dump excess power from a power source who's output must be used as it cannot be "throttled". Examples include Horizontal Axis Wind Turbines (HAWT) are one--The turbines will over-speed in high winds if current is "turned off" when battery bank is full. Or Diesel gensets that usually must run at a minimum of 40-60% load or the engines will have problems when operated at light loads ("wet stack", carbonizing of combustion chamber, glazing of cylinder walls).

    Opportunity Load: A load that may be operated when there is "excess available power" available from generating sources. For example, Solar Arrays can be cycled on/off without damage--However, when the batteries are near full, there is "excess capacity" available that can be used for other needs. Water pumping, water heating, and desalinization are examples of Opportunity Loads.

    Diversion and Opportunity Loads do sort of have a crossover--You could use an Opportunity Load (water pumping) on a diesel genset when the battery bank and other loads are low.

    And you can used a Diversion (aka Dump and Shunt) controller to control the charging from a solar array on a battery bank.

    Diversion loads are (in my humble opinion) used to safely "dump" excess power needed to keep the generating source operating within specifications. And, for diversion charge controllers, they should have at least one backup to prevent (for example) the over charging of a battery bank (fire/explosion) or self destruction of a wind turbine if the primary diversion controller+load (such as a resistor bank) fails.

    Opportunity loads are just that--They are turned on when "cost effective" excess power is available (such as when battery bank is full) and you can pump water/run your clothes washer on the "extra power". If an opportunity load fails, there is no chance of fire/mechanical failures because the opportunity load has failed to consume the energy or the owner decided not to use the load that day.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,004 admin
    Re: Glossary

    From another thread, ILFE and Caribootcoot:
    Volts / Ohms = Amps (Ohm's Law).
    Volts * Amps = Watts (Power Formula without power factor correction).
    MPPT output current = panel Wattage * 0.77 efficiency / nominal battery Voltage.
    PWM output current = input current.
    To determine breaker or fuse size for panels: multiply Isc by 1.56 and round up to the next available size.
    Amp hours * battery Voltage = nominal total capacity in Watt hours.
    Watt rating * hours of use = Watt hours consumed.
    Watt hours per day / system Voltage = Amp hours per day (nominal).
    Rated array Watts x hours of good sun * 0.52 over-all efficiency = usable AC Watt hours.
    Rated array Watts x 0.77 efficiency * hours of good sun = expected grid-tie system production.

    There are some caveats that need to be included, such as real Amp hour capacity varying with rate of use and the fact the efficiency deratings are variable.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • alexjalexj Registered Users Posts: 25 ✭✭
    edited February 5 #6
    I have been building a free resource that is based upon the same platform as wikipedia - - that explains and links together many of the terms and concepts that are frequently discussed here. It covers off-grid system design from the most basics concepts to large stand-alone system design. I hope it's helpful.
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