Definitions - d


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

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Days Of Storage

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Debt-for-nature Swap

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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.

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Deep Cycle Battery

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Deep Discharge

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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.

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Demand Response

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

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Density Dependence

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 The conversion of salt or brackish water into usable fresh water. Distillation is the most common commercial method; heat from the Sun or conventional fuels vaporizes brine, the vapor condensing into fresh water on cooling. Reverse osmosis and electrodialysis both remove salt from water by the use of semipermeable membranes; these processes are more suitable for brackish water. Pure water crystals may also be separated from brine by freezing.

The biggest problem holding back the wider adoption of desalination techniques is that of how to meet the high energy costs of all such processes. Only where energy is relatively cheap and water particularly scarce is desalination economic, and even then complex energy conservation procedures must be built into the plant.

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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.

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Design Month

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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

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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.

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Direct Insolation

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Direct Run-off

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Dirty Fallout

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Dispersion Trench

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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

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Dobson Unit

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Double-hung Windows

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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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  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.

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Drip Irrigation

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

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Dry Deposition

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Dry Farming

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Dry Rot

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Dryland Salinity

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Dryland Systems

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Dump Load

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Dystrophic Lakes

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