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Gassing:Hydrogen Gas 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.

Grounded: connected to the earth or to a metallic conductor or surface that serves as earth (e.g. the chassis of an automobile)

Grounding Conductor: (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 conductor.

Grounding Electrode: 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 Grid)

Guarantee: Promise in writing that something will perform satisfactorily for a given length of time.

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.


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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 Fluorescent).

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; Transformer)

Inductive 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; Solar Resource)

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.

Inverter/Charger: 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.

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Juice: 100% pure, fresh electrical power!

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 energy.

LCD: Liquid Crystal Display.

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.

Maintenance-Free 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 Point Tracking.)


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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 enchantment)

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 FINISH

NiMh (Nickel Metal Hydride) Battery: finish

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, True)

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 (ohms).

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.

Overcharge: Forcing current into a fully charged battery. The battery will be damaged if overcharged for a long period. (See Equalization)


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