Definitions - d

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

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.

Energy Efficiency is when you use less energy to accomplish the same task, for example heating your home or washing clothes. Using less energy by being more efficient means less air pollution and lower costs.

To save energy in your home, you can use weather stripping, solar water heating, passive solar or compact fluorescent light bulbs. Also when shopping for household appliances, look for the Energy Star to find appliances that use less energy and lower your electricity costs.

You can also reduce your heating and cooling costs by installing better insulation.

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.

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.

Clusters of houses having shared dining halls and other spaces, encouraging stronger social ties while reducing the material and energy needs of the community.

A manifestation of weather which is rare within its statistical distribution on a particular location. By rare one usually means rarer than the 90th percentile. The characteristics of extreme weather vary according to the location.

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.

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

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.