Definitions - d


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

Search the Web for Darrieus

Using various design methods, such as windows and skylights, to reduce the building’s reliance on electric lighting. Numerous studies have highlighted the productivity benefits of natural lighting for building occupants.

Search the Web for Daylighting
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.

Search the Web for Days Of Storage
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.

Search the Web for Debt-for-nature Swap

Perennial plants whose leaves die all at once (and usually fall) at the end of each growing season, to be replaced by new leaves at the next growing season. Most deciduous plants are broad-leaved, though a few, such as Larix laricina (Tamarack), have needles. Plants whose leaves live year-round are evergreen.

Search the Web for Deciduous

A shift in climate (e.g., temperature or precipitation) that occurs faster than the rate of change in the mechanism causing the change.

Search the Web for Decomposer
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.

Search the Web for Deep Cycle Battery
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.

Search the Web for Deep Discharge
Deep Green

Someone who believes we need a radical transformation to a more sustainable society. Also, the belief environmental sustainability should have primacy over economic and social factors. Contrasts with light green and bright green.

Search the Web for Deep Green

Ability of materials to break down, by bacterial (biodegradable) or ultraviolet (photodegradable) action.

Search the Web for Degradability

Human made. In the context of greenhouse gases, emissions that are produced as the result of human activities.

Search the Web for Delta
Demand Response

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

Search the Web for Demand Response

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

Search the Web for Denitrification
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.

Search the Web for Density Dependence

Any change to the environment whether adverse or beneficial, wholly or partially resulting from human activity, industry or natural disasters.

Search the Web for Desalination

Conversion of rangeland, rain-fed cropland to desert-like land, with a drop in agricultural productivity of 10% or more. This is usually caused by a combination of overgrazing, soil erosion, prolonged drought, and climate change.

Search the Web for Desertification
Design Month

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

Search the Web for Design Month

Animals and plants that consume detritus (decomposing organic material), and in doing so contribute to decomposition and the recycling of nutrients.

Search the Web for Detritivore
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

A pesticide used on citrus fruits.

Search the Web for Dicofol

A condition in trees or woody plants in which peripheral parts are killed, either by parasites or due to conditions such as acid rain.

Search the Web for Dieback

Long-lasting highly toxic hydrocarbons; byproducts of various industrial processes, including paper and pesticide manufacturing and waste incineration. Dioxins are the most potent carcinogens known to science and also may affect human development and reproduction.

Search the Web for Dioxins
Direct Insolation

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

Search the Web for Direct Insolation
Direct Run-off

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

Search the Web for Direct Run-off
Dirty Fallout

Air pollutants dropped by prevailing winds.

Search the Web for Dirty Fallout

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.

Search the Web for Dispatchability
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.

Search the Web for Dispersion Trench
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.

Search the Web for Distributed Energy Resources
Diurnal Temperature Range

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

Search the Web for Diurnal Temperature Range
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.

Search the Web for Dobson Unit
Double-hung Windows

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

Search the Web for Double-hung Windows

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.

Search the Web for Downcycling

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.

Search the Web for Downwelling
Drainage Area

This is the total surface area, upstream of a point on a stream, where the water from rain, snowmelt, or irrigation not absorbed into the ground flows over the ground surface, back into streams, to finally reach that point.

Search the Web for Drainage Area

  1. The drop in the water table or level of water in the ground when water is being pumped from a well.
  2. The amount of water used from a tank or reservoir.
  3. The drop in the water level of a tank or reservoir.

Search the Web for Drawdown
Drip Irrigation

The practice of spraying water directly on the base of plants so that less water is needed to make them grow.

Search the Web for Drip Irrigation
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.

Search the Web for Dry Deposition
Dry Farming

A type of farming practiced in semi-arid or dry grassland areas without irrigation using such approaches as fallowing, maintaining a finely broken surface, and growing drought-tolerant crops.

Search the Web for Dry Farming
Dry Rot

A crumbling and drying of wood that is caused by a fungus; turns wood into powder.

Search the Web for Dry Rot
Dryland Salinity

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

Search the Web for Dryland Salinity
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.

Search the Web for Dryland Systems
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.

Search the Web for Dump Load
Dystrophic Lakes

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

Search the Web for Dystrophic Lakes

Click on a letter to see all the terms and definitions that begin with that letter.

A free Android app containing all these definitions is now available, called the Green Dictionary. Click here to see the entry on the Android market; or click here if on an Android phone.