Definitions - d

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

A turbine having a large vaned wheel rotated by the wind to generate electricity. Often collected together to form 'farms'.

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.

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.

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.

A Decomposer is an an organism whose ecological function involves the recycling of nutrients by performing the natural process of decomposition as it feeds on decaying organisms.

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.

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.

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.

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

A fan-shaped alluvial deposit at a river mouth formed by the deposition of successive layers of sediment.

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

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

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.

 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.

Total dry weight of all living organisms that can be supported at each tropic level in a food chain.

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

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

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.

A pesticide used on citrus fruits.

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

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.

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

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

Air pollutants dropped by prevailing winds.

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.

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.

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.

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

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.

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

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.

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.

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.

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.

Total dry weight of all living organisms that can be supported at each tropic level in a food chain.

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.

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.

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

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

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

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.

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