Definitions - n

Nacelle

The part of a wind generator that houses the generator, gearbox etc at the top of the tower.

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Nacreous Clouds

Clouds of unknown composition that have a soft, pearly luster and that form at altitudes about 25 to 30 km above the earth's surface. They are also called mother-of-pearl clouds.

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Natural Products

Natural Products are products made using natural organic ingredients and none factory processes. Often made by small independent local businesses or individuals.

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Negative Feedback

A process that results in a reduction in the response of a system to an external influence. For example, increased plant productivity in response to global warming would be a negative feedback on warming, because the additional growth would act as a sink for CO2, reducing the atmospheric CO2 concentration.

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Nekton

Animals, such as fish and whales, that move independently of water currents between the bottom and surface of the ocean.

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Net Metering

Net Metering is a method of crediting customers for electricity that they generate on site in excess of their own electricity consumption. Customers with their own generation offset the electricity they would have purchased from their utility. If such customers generate more than they use in a billing period, their electric meter turns backwards to indicate their net excess generation.

Depending on individual state or utility rules, the net excess generation may be credited to their account (in many cases at the retail price), carried over to a future billing period, or ignored.

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Nimbostratus

A dark, gray cloud characterized by more or less continuously falling precipitation. It is not accompanied by lightning, thunder, or hail.

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Nitrate

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Nitrilotriacetic Acid

(NTA) A compound now replacing phosphates in detergents.

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Nitrogen Cycle

Cyclic movement of nitrogen in different chemical forms from the environment, to organisms, and then back to the environment.

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Nitrogen Fixation

GreenGuard certification for a product indicates it has been tested to ensure chemical and particle emissions meet acceptable standards. It uses performance-based standards to define goods such as building materials, interior furnishings, furniture, cleaning and maintenance products, electronic equipment and personal care products with low chemical and particle emissions for use indoors.

The standards establish certification procedures including test methods, allowable emissions levels, product sample collection and handling, testing type and frequency, and program application processes and acceptance.

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Non-linearity

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of about 5730 years. Carbon is one of the few elements known since antiquity. The name "carbon" comes from Latin language carbo, coal.

See the full entry on wikipedia

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Non-potable

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Nonpoint Sources

Sources of pollution that do not originate at the point where pollution is detected, e.g.: agricultural runoff: precipitation and irrigation-related runoff of animal wastes and pesticides from crop and pasture lands. feedlot runoff: primarily precipitation-related discharge of animal wastes from concentrated livestock feeding areas. individual wastewater treatment system runoff: discharge of partially treated sewage from malfunctioning on-site septic systems. urban runoff: precipitation-related discharge of septic leachate, animal wastes, etc. from impervious surfaces, lawns, and other urban land uses. wildlife runoff: precipitation-related runoff of animal wastes from areas with high concentrations of wildlife (e.g., waterfowl).

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Null Electricity

Null Electricity is electricity that is stripped of its attributes and undifferentiated. No specific rights to claim fuel source or environmental impacts are allowed for null electricity.  Also referred to as commodity or system electricity.

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Null Hypothesis

The assumption that any observed difference between two samples of a statistical population is purely accidental and not due to systematic causes.

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Nutrient Pollution

Contamination of water resources by excessive inputs of nutrients. In surface waters, excess algal production is a major concern.

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