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TERMINOLOGY

Acceleration - Increase in the velocity of a fluid or body

Centralized generation - Large scale generation; usually remote from the demand load requiring substantial transmission capacity to deliver the produced electricity

Consumption intensity - Instantaneous power used by a demand source per unit horizontal area e.g. kilowatt hours per square meter (kWh/m2); can be annualized. Urban examples:

New York City          126 kWh/m2
Los Angeles              96 kWh/m2
Hong Kong                77 kWh/m2
London                      63 kWh/m2
Chicago                     56 kWh/m2
Urban average           50 kWh/m2

Demand intensity – (see "consumption intensity")

Distributed energy (DE) - Energy produced near or at a demand source; can be generation or fuel production. Avoided transmission cost and losses are one of DE's potential advantages.

Distributed generation (DG) - generation near or at a demand source; usually below 25 MW

Energy density - Energy flux across a generation conversion plane

Energy intensity - Refers to the instantaneous or annual power consumed or produced in a unit horizontal area e.g. square meter (m2). It is sometimes also called power density or power intensity. Energy intensity increases as the cube of the fluid's velocity in fluid systems. For example, a 2 times acceleration of fluid velocity will result in an 8 times increase in energy intensity. (For the power density or power intensity of various technologies see V.Smil - Power Density: A Primer)

Energy supply intensity – Energy intensity per total area used by a generation technology; captures how efficiently a technology uses land or building rooftops; can be annualized. Urban examples:

Photovoltaic (DE)     1.5 kWh/m2
Wind (DE)                1.7 kWh/m2
Natural Gas (plant)   262 kWh/m2

Gen I energy - A generation technology that is limited by the naturally occurring intensity of its resource. Fossil fuels are limited to the maximum intensity of the chemical release of energy under combustion. Solar is limited to a maximum intensity by solar insolation per horizontal m2. In both examples these are hard limits to the technologies' intensity. Fossil cannot yield more energy than is released by the natural chemical reaction. Solar cannot yield more than the energy in the sunlight per m2 at the latitude irrespective of concentration, e.g. a solar tower or CSP will have the same intensity over its entire area as a PV module solar farm. Fossil and solar may improve their efficiency or capacity factor but will never increase their resource intensity or be Gen II technologies.

Gen II energy - A generation technology that is not limited by the naturally occurring intensity of its resource. In fluids and nuclear the naturally occurring intensity can be increased. For nuclear the natural intensity would be the radioactive decay of the fuel. For hydro it would be the freestream velocity of the water. For fluids increased velocity (by an accelerator) or pressure head (by a dam) yields increased energy intensity.

Generation intensity – (see "energy supply intensity")

Levelized Cost of Energy (LCOE) - The annualized all-in cost of a generation technology's equipment, cost of money, installation, permitting, and annual operating and maintenance expenses divided by the annual power produced. A typical NG central plant (>100MW) LCOE is approximately 6.5 cents per kWh. PV or Architectural Wind DE installations have LCOE's from 30 -50 cents per kWh (unsubsidized).

Supply capacity - The percentage of a demand load that can be supplied by a given generation technology; equal to Supply intensity divided by Demand intensity. Urban DE and DG examples:

Photovoltaic (DE)        3%
Wind (DE)                   3-4%
Natural Gas (plant)     >100%

Transmission - The power cable and associated capital equipment necessary to transfer electrical power produced at a given location to where the power is needed. DE limits the need for transmission.



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