Definitions - d

Darrieus

A Vertical Axis Wind Turbine design from the 1920s and 1930s by F.M. Darrieus, a French wind turbine designer.

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Daylighting

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Days Of Storage

The number of consecutive days the stand-alone system will meet a defined load without solar energy input. This term is related to system availability.

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Debt-for-nature Swap

Agreement in which a certain amount of foreign debt is canceled in exchange for local currency investments that will improve natural resource management or protect certain areas in the debtor country from harmful development.

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Deciduous

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Decomposer

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Deep Cycle Battery

A Deep Cycle Battery is a battery that is capable of been discharged to nearly completely empty without long term negative effects on the life of the battery and its storage capacity.


Most batteries if deeply discharged will suffer a rapid degradation in their storage capacity.

Some batteries, such as Zinc Bromine based batteries, are able to be completely discharged without ill effect.

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Deep Discharge

The number of consecutive days the stand-alone system will meet a defined load without solar energy input. This term is related to system availability.

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Deep Green

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Degradability

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Delta

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Demand Response

Mechanisms to manage the demand from customers in response to supply conditions.

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Denitrification

Removal of nitrate and nitrate product from water to produce a quality that answeres common water standards.

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Density Dependence

The tendency of a population's growth rate to depend on its size, with an increase in population density corresponding to a decrease in growth. This self-regulating dynamic helps prevent extinction.

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Desalination

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Desertification

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Design Month

The month having the combination of insolation and load that requires the maximum energy from the photovoltaic array.

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Detritivore

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Dew Point

The dew point is the temperature to which a given parcel of humid air must be cooled, at constant barometric pressure, for water vapor to condense into water. The condensed water is called dew. The dew point is a saturation temperature.

The dew point is associated with relative humidity. A high relative humidity indicates that the dew point is closer to the current air temperature. Relative humidity of 100% indicates the dew point is equal to the current temperature and the air is maximally saturated with water. When the dew point remains constant and temperature increases, relative humidity will decrease. Search the Web for Dew Point
Dicofol

A pesticide used on citrus fruits.

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Dieback

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Dioxins

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Direct Insolation

Sunlight falling directly upon a collector. Opposite of diffuse insolation.

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Direct Run-off

Water that flows from the ground surface directly into streams, rivers, and lakes.

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Dirty Fallout

Air pollutants dropped by prevailing winds.

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Dispatchability

Dispatchability is the ability of a power plant to be turned on quickly to a desired level of output. Wind power plants are not dispatchable.

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Dispersion Trench

A Dispersion Trench is a method by which effluent after processing is distributed back into the environment in a way which reduces environmental impact. They often positioned so that the effluent is distributed by a grid of trench pipes into the soil directly; the aim being that the effluent never gets to the surface.


They are typically positioned such that the danger of run off into creeks, waterways and natural landscapes is minimized. This can often be achieved by placing the trenching in a lawn in a residential context.

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Distributed Energy Resources

DERs. A variety of small, modular power-generating technologies that can be combined with energy management and storage systems and used to improve the operation of the electricity delivery system, whether or not those technologies are connected to an electricity grid.

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Diurnal Temperature Range

The difference between maximum and minimum temperature over a period of 24 hours.

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Dobson Unit

A unit used to measure the abundance of ozone in the atmosphere; one Dobson unit is the equivalent of 2.69 x 1016 molecules of ozone/cm2.

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Double-hung Windows

A traditional window style with two glass-holding frames that slide past each other vertically.

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Downcycling

Downcycling is the recycling of a material into a material of lesser quality. For example, when plastics are recycled they are turned into a lower grade quality plastic.

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Downwelling

The process of accumulation and sinking of warm surface waters along a coastline. A change of air flow of the atmosphere can result in the sinking or downwelling of warm surface water. The resulting reduced nutrient supply near the surface affects the ocean productivity and meteorological conditions of the coastal regions in the downwelling area.

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Drainage Area

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Drawdown

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Drip Irrigation

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Dry Deposition

Emissions of sulphur and nitrogen oxides that, in the absence of water in the atmosphere (i.e., rain), settle to the ground as particulate matter.

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Dry Farming

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Dry Rot

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Dryland Salinity

(water management) Accumulation of salts in soils, soil water and ground water; may be natural or induced by land clearing

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Dryland Systems

Dryland systems are ecosystems characterised by a lack of water. They include cultivated lands, scrublands, shrublands, grasslands, savannas, semi-deserts and true deserts.

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Dump Load

A device to which wind generator power flows when the system batteries are too full to accept more power, usually an electric heating element. This diversion is performed by a Shunt Regulator, and allows a Load to be kept on the Alternator or Generator.

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Dystrophic Lakes

Acidic bodies of water that contain many plants but few fish, due to the presence of great amounts of organic matter.

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