G to O
that bubbles up when charging a battery, contains sulfides and is poisonous,
flammable, and highly corrosive(or byproduct from consumption of Legumes).
Gel Cell Battery: maintenance
free battery that uses a gelled acid instead of liquid.
Golf Cart Batteries:
Low cost, deep cycle batteries used in electric vehicles, and small to
medium sized home solar systems. Usually open
Ground Rod: Copper plated
steel rod, usually 8 ft. long, that is driven into the ground (preferably
ground that stays moist year-round), to establish an electrical connection
with the earth ("ground"), and to which is attached the system's
grounding electrode conductor.
to the earth or to a metallic conductor or surface that serves as earth
(e.g. the chassis of an automobile)
(bare, green, or green with yellow stripe) A conductor not normally carrying
current used to connect the exposed metal portions of equipment that might
be accidentally energized to the grounding electrode system or the grounded
The conducting element in electrical contact with the earth (e.g. a ground
rod, a concrete encased conductor, grounded steel well casing, grounded
building steel, etc.)
Grounding Electrode Conductor:
A conductor not normally carrying current used to connect the grounded
conductor to the grounding electrode or grounding electrode system.
Grid: (See Electrical
Guarantee: Promise in
writing that something will perform satisfactorily for a given length
Guerrilla Solar: Grid
intertied systems that supply power to the grid without proper authorization
from (sometimes hostile) utility companies. They almost always still have
built-in safety features (anti- islanding) that prevent energizing lines
when the utility power is off.
Hallucination: a Sensory
experience that doesn't exist except in one's mind.
High Voltage Disconnect:
The voltage at which the charge controller will disconnect the array from
the batteries to prevent overcharging.
IV Curve: Plot of the
Current (I) versus Voltage (V) output of a photovoltaic cell, module,
or array. Three important points on the IV curve are the open-circuit
voltage, short-circuit current, and peak power operating point.
Impedance:This is the
total opposition to the flow of electricity in a circuit, combining the
effects of resistance, inductance and capacitance--measured in ohms.
Incandescent Light Bulb:
The "standard" type of light bulb, invented by Thomas Edison
100 years ago, in which electricity flows through a small filament which
disperses a small fraction of its energy as light and over 90% as heat.
They are very inefficient and should not be used in RE systems. (See Compact
Inductance (L): The
storage of electrical energy in a magnetic field, which creates opposition
to a change in current--like electrical inertia. When varying current
flows through a conductor (especially if coiled), a field of electromagnetic
flux (EMF) is generated that will induce voltage in any nearby conductor
(especially if coiled), as well as in the current carrying conductor itself.
Inductance in a circuit creates a phase difference between the voltage
and the current in that circuit, in which the voltage leads, or peaks
before the amperage. The unit of inductance is the henry (h). (See EMF;
Load: Any electrical device that has inductance and requires a
surge of power to start--especially those with inductive motors in them,
such as power tools and traditional AC well pumps, which can require up
to six times the power they need to run in order to start running. As
opposed to a resistive load.
Insolation: The incident
solar radiation (i.e. the amount of sunlight that falls)
on an area over time. Irradiance multiplied by time. Equivalent to energy
and usually expressed in kWh/m². Insolation Tables show insolation
data for many different places and different seasons. (See Irradiance;
Inverter: A device that
changes DC power (from the PV array and/ or batteries) to AC power compatible
with the utility grid and household AC appliances.
This is an inverter, designed to be used in a battery based system, that
has a built-in battery charger and automatic transfer switch.
Inverter Generator: New type of engine powered electric
generator that produces variable voltage DC that is then tamed by an onboard
inverter to produce a very stable AC sine wave regardless of engine RPM.
Lighter weight, more efficient, and quieter than regular generators.
Irradiance: The solar
power incident on a surface. Usually expressed in kw/m². Irradiance
multiplied by time equals Insolation.
Islanding: This occurs
when the grid power fails or is shut off for service and a grid tied inverter
continues providing power to the grid, to power an "island"
of local homes that are separated from the rest of the grid. This essentially
theoretical situation would occur if the neighborhood's loads were within
the inverter's output capacity. UL listed grid-tie inverters will disconnect
from the grid in this situation in milliseconds,so as to avoid powering
a local section of the grid that was purposefully shut down by utility
personnel for service.
Juice: 100% pure, fresh
Kilowatt (kW): One thousand
watts. A unit of power.
Kilowatt Hour (kWh): One thousand
watt-hours. A unit of energy. Power (watts) multiplied by time equals
LCD: Liquid Crystal
Latitude: angle measured
at the center of the earth from the equator to any point on the earth's
surface. 0 degrees would be at the equator, while the North pole would
be at 90 degrees latitude. Taos is around 36 degrees latitude. Latitude
is used in determining what angle to tilt a solar array to, and for determining
how long shadows will be.
Li+ Lithium Ion Battery: finish
Load: Any device that
consumes electrical energy. Also, the amount of electrical energy consumed
by a device.
Low Voltage: Voltage
under 50 volts, generally not considered an electrocution hazard. 48 volt
nominal systems are slightly controversial because they can operate above
or below 50 volts.
Low Voltage Disconnect (LVD):
A device (often built-into a charge controller) that disconnects all loads
from the batteries when battery voltage drops below a setpoint (typically
around 11 volts for a 12 volt nominal system) to prevent over-discharge
of the batteries.
Battery: Any sealed battery to which water cannot be added to maintain
electrolyte level. Includes sealed flooded acid (automotive types), AGM,
and Gel Cell batteries.
Maximum Power Point: also Peak Power
Point. The operating point of a PV module that produces the most power.
For a 12V nominal panel that point is usually around 16 to 17 volts and
current is about 90% of maximum. This combination of current times voltage
yields the most watts of power.
Maximum Power Point Tracking
(MPPT): A type of charge controller that operates the solar modules
at their Max Power Point and then reduces that voltage to the battery
voltage while boosting current.
Module: (See PV module)
Monocrystalline Cells (single crystal PV
cells): Usually higher performance than other types of PV cells.
Grown from single large crystals of silicon then sliced into cells.
MPPT: (See Max Power
NABCEP (North American Board
of Certified Energy Practitioners): Performs rigorous testing to
certify solar Installers and designers on a national level. Through stringent
qualifications NABCEP differentiates certified solar installers from regular
licensed electricians, and installers with no solar credentials.
NEC (National Electrical Code):
A set of guidelines for all types of electrical installations including
Article 690, "Solar Photovoltaic Systems". Now law nationwide.
NEC Compliant (Code Compliant):
Implies that a system design, its components, and its wiring comply with
the requirements of the National Electric Code.
NEMA (National Electrical Manufacturers
Association): This organization sets standards for some non-electronic
products like junction boxes.
NM: (NMB) Solid core,
Multi-conductor wire type that is not outdoor rated, water proof, sunlight
resistant, or suitable for direct burial. Commonly called Romex , used
for inside wiring in houses. (AlsoNew Mexico, our land of
Net Metering: Grid intertie
method that uses one meter which runs forward when you are using energy
from the grid and turns backward when you sell power to the grid. At the
end of the month you pay the net amount you have used, or the utility
pays you if you use less than you produce.
NiCad (Nickel Cadmium) Battery:
another type of battery that uses Nickel
NiMh (Nickel Metal Hydride)
Normal Operating Cell Temperature
(NOCT): The estimated temperature of a PV module when operating
under 800 w/m² irradiance, 20ºC ambient temperature and wind
speed of 1 meter per second. NOCT is used to estimate the nominal operating
temperature of a module in its working environment.
Nominal Voltage (V nom.):
A reference voltage used to describe batteries, modules, or systems. Actual
voltage may vary significantly. (I.e., a 12V nominal battery can charge
as high as 15.5 volts and discharge to as low as 10 volts, A 12V nominal
module can operate from 0 to 22 volts)
North, Magnetic: The
direction the needle of a compass points, which is different than true
north by what is called declination. (See Declination; North, True; South,
North, True: The direction
toward the north pole. Finding this direction allows you to then find
true south which is needed for siting and facing a solar array, or solar
house. (See North, Magnetic; Declination; South, True)
NREL (National Renewable Energy Labs): Federally
funded research facility, also performs educational and promotional work
for renewable energy. a branch of the Dept of Energy.
Ohm (Ω): The unit
of electrical resistance in which an electromotive force of one volt maintains
a current of one ampere.
Ohm's Law: This expresses
the relationship between voltage (volts), amperage (amps), and resistance
Open Circuit Voltage:
The maximum voltage produced by an illuminated photovoltaic cell, module,
or array with no load connected. This value will increase as the temperature
of the PV material decreases.
current into a fully charged battery. The battery will be damaged if overcharged
for a long period. (See Equalization)