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Wind Energy (the facts) - Glossary of wind turbines
Category: Sciences > Glossary of wind turbines
Date & country: 21/12/2010, UK
Words: 126


Adequacy
a measure of the ability of the power system to supply the aggregate electric power and energy requirements of the customers within component ratings and voltage limits, taking into account planned and unplanned outages of system components. Adequacy measures the capability of the power system to supply the load in all the steady states in which ...

Ancillary services
are services such as provision of reactive power, or frequency response, necessary for control or operation of the power system, and which it may be beneficial to provide from generators or other system users.

Annualised net metering
is the same as net metering, but in this case the regulator averages a user`s net electricity consumption or production over the span of one full year, rather than a shorter period.

ASACS
UK Air Surveillance and Control Systems.

Auxiliary costs
are other than those of the turbine itself, in other words foundation, grid connection, electrical installation, road construction, financial charges and so on.

Availability
describes the amount of the time that the wind turbine is actually functional, not out of order or being serviced.

Balance of Plant
(BOP) the infrastructure of a wind farm project, in other words all elements of the wind farm, excluding the turbines. Includes civil works, SCADA and internal electrical system. It may also include elements of the grid connection.

Black start capability
some power stations have the ability to start up independently of a power grid. This is an essential prerequisite for system security, as these plants can be called on during a blackout to re-power the grid.

Boundary layer profile
see wind shear profile.

Capacity
is the rated continuous load-carrying ability of generation, transmission or other electrical equipment, expressed in megawatts (MW) for active power or megavolt-amperes (MVA) for apparent power.

Capacity credit
a wind turbine can only produce when the wind blows and therefore is not directly comparable to a conventional power plant. The capacity credit is the percentage of conventional capacity that a given turbine can replace. A typical value of the capacity credit is 25 per cent (see capacity factor).

Capacity factor
(load factor) is the ratio between the average generated power in a given period and the installed (rated) power.

Capital costs
are the total investment costs of the project, including auxiliary costs.

Carbon dioxide
(CO2) is a naturally occurring gas, and also a by-product of burning fossil fuels and biomass, as well as land-use changes and other industrial processes. It is the principal anthropogenic greenhouse gas that affects the Earth`s radiative balance.

Citizen engagement
can be defined as being responsive to lay views and actively seeking the involvement of the lay public in policymaking and decision-making. Considered a central motif in public policy discourse within many democratic countries, it is acknowledged as an important component of good governance.

Climate change
is a change of climate attributed directly or indirectly to human activity which alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.

Cogging
variation in speed of a generator due to variations in magnetic flux as rotor poles pass stator poles. Cogging in permanent magnet generators can hinder the start-up of small wind turbines at low wind speeds.

Community acceptance
refers to the acceptance of specific projects at the local level, including affected populations, key local stakeholders and local authorities.

Contingency
is the unexpected failure or outage of a system component, such as a generator, transmission line, circuit breaker, switch or other electrical element. A contingency may also include multiple components which are related by situations leading to simultaneous component outages.

Control area
is a coherent part of the UCTE Interconnected System (usually concurrent with the territory of a company, a country or a geographical area, and physically demarcated by the position of points for measurement of the interchanged power and energy to the remaining interconnected network), operated by a single transmission system operator (TSO), with p...

Control block
comprises one or more control areas, working together in the secondary control function, with respect to the other control blocks of the synchronous area to which it belongs.

Costs of generated wind power
see levelised costs.

Curtailment
means a reduction in the scheduled capacity or energy delivery.

D
is the wind turbine rotor diameter (measured in metres).

Darrieus rotor
is a sleek vertical axis wind turbine developed by French inventor G. J. M. Darrieus in 1929 based on aerodynamic profiles.

dB(A)
The human ear is more sensitive to sound in the frequency range 1 kHz to 4 kHz than to sound at very low or high frequencies. Therefore, sound meters are normally fitted with filters adapting the measured sound response to the human ear.

Decibel
(dB) is a unit of measurement that is used to indicate the relative amplitude of a sound or the ratio of the signal level such as sound pressure. Sound levels in decibels are calculated on a logarithmic scale.

Diffuser
is a downwind device that diffuses the wind stream through a rotor.

Direct drive
is a drive-train concept for wind turbines in which there is no gearbox and the wind turbine rotor is connected directly to a low-speed electrical generator.

Direct employment
is the total number of people employed in companies belonging to a specific sector.

Discount rate
is the interest rate (in ) used to calculate the equivalent present-day costs or value of future expenditure or income.

Distributed generation
means single or small clusters of wind turbines spread across the landscape, in contrast to the concentration of wind turbines in large arrays or wind power plants.

Doppler effect
(or Doppler shift) after Austrian physicist Christian Johann Doppler (1803–1853).

Doubly fed induction generator
(DFIG) is an electrical machine concept in which variable-speed operation is provided by using a relatively small power electronic converter to control currents in the rotor, such that the rotor does not necessarily rotate at the synchronous speed of the magnetic field set up in the stator.

DTI
former Department of Trade and Industry of the UK Government, now Department of Business, Enterprise and Regulatory Reform (BERR).

Efficiency
for a turbine describes the amount of active electrical power generated as a percentage of the wind power incident on the rotor area.

Electricity demand
is the total electricity consumption in GWh consumed by a nation annually.

Emissions
are the discharges of pollutants into the atmosphere from stationary sources such as smokestacks, other vents, surface areas of commercial or industrial facilities, and mobile sources such as motor vehicles, locomotives and aircraft. With respect to climate change, emissions refer to the release of greenhouse gases into the atmosphere over a specif...

Energy payback
is the time period it takes for a wind turbine to generate as much energy as is required to produce the turbine in the first place, install it, maintain it throughout its lifetime and, finally, scrap it. Typically, this takes 2–3 months at a site with reasonable exposure.

Equivalent sound level
(dBLeq) quantifies the environmental noise as a single value of sound level for any desired duration. The environmental sounds are usually described in terms of an average level that has the same acoustical energy as the summation of all the time-varying events.

ETSU
Energy Technology Support Unit of the UK Government.

EWEA
European Wind Energy Association.

Experience curve
relates the cumulative quantitative development of a product with the development of the specific costs. The more this product is produced, the more efficient the production process and the cheaper it becomes.

External costs
are those costs incurred in activities which may cause damage to a wide range of receptors, including human health, natural ecosystems and the built environment, and yet are not reflected in the price paid by consumers.

Fault ride-through
(FRT) is a requirement of many network operators, such that the wind turbine remains connected during severe disturbances on the electricity system, and returns to normal operation very quickly after the disturbance ends.

FINO 1
is an offshore research platform in the North Sea, off Germany.

Fuel cycle
the impacts of power production are not exclusively generated during the operation of the power plant, but also in the entire chain of activities needed for the electricity production and distribution, such as fuel extraction, processing and transformation, construction and installation of the equipment, and the disposal of waste. These stages, whi...

Full load hours
is the turbine`s average annual production divided by its rated power. The higher the number of full load hours, the higher the tubine`s production at the chosen site.

Furling
is a passive overspeed control mechanism which functions by reducing the projected swept area, by turning the rotor out of the incident wind direction.

Gate closure
is the point in time when generation and demand schedules are notified to the system operator.

Generation mix
is the percentage distribution by technology (nuclear, thermal, large hydro, renewables) of the capacity of operational generation plants.

Geographical information system
(GIS) is a software system which stores and processes data on a geographical or spatial basis.

Giromill
(or cycloturbine) is a vertical axis H configuration wind turbine with articulating straight blades.

Greenhouse gases
are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of infrared radiation emitted by the Earth`s surface, the atmosphere and clouds. Human-made greenhouse gases in the atmosphere such as halocarbons and other chlorine- and bromine containi...

Grid reinforcement
a weak grid can be reinforced by up-rating its connection to the rest of the grid. The cost of doing this may fall to the wind farm developer.

Grid-connected
a wind turbine is grid-connected when its output is channelled directly into a national grid (see also stand-alone system).

High voltage
(HV) typically 100 to 150 kV.

Horizontal axis wind turbine
(HAWT) a wind turbine whose rotor axis is substantially parallel to the wind flow.

Hub
the rotating component of the wind turbine to which the rotor blades are fixed.

Hub height
is the height of the rotor axis above the ground.

Hybrid power systems
(HPS) are combinations of renewable technologies (such as wind turbines or solar photovoltaics) and conventional technologies (such as diesel generators) that are used to provide power to remote areas.

IEC
International Electrotechnical Commission.

Impact pathway approach
is developed by ExternE to establish the effects and spatial distribution of the burdens from the fuel cycle to find out their final impact on health and the environment. Subsequently, the economic valuation assigns the respective costs of the damages induced by a given activity.

Independent power producer
(IPP) a privately owned and operated electricity production company not associated with national utility firms.

Indirect employment
refers to those employed in sectors and activities supplying intermediate products/components to, for example, wind turbine manufacturers. Indirect employment includes employment throughout the production chain.

Input-output
the national accounts of a country`s or region`s economic transactions keep track of all the inputs and outputs between economic sectors.

Installed capacity
is the total MW of operational generation plant of a given technology.

Institutional capacity building
refers to the process of creating more effective institutions through the increase of shared knowledge resources, relational resources and the capacity for mobilisation. It is usually related to the capacity to facilitate open policy- and decision-making processes (at national and local levels) that provide access to relevant stakeholders and room ...

Institutional framework
is a concept used to refer to the policy and regulatory elements affecting energy developments. In the wind energy context, this would include issues such as political commitment, financial incentives, planning systems, presence and roles of landscape protection organisations, and patterns of local ownership.

Interconnected system
two or more individual electric systems that normally operate synchronously and are physically connected via tie-lines (see also synchronous area).

Interconnection
is a transmission link (such as a tieline or transformer), which connects two control areas.

Intermedial load
refers to those electricity-generation technologies contributing to satisfy the demand in a range between the base load and peak load of the electricity system. A generating unit that normally operates at a constant output (amount of electricity delivered) takes all or part of the base load of a system. In contrast, a peak load unit is only used to...

Investment costs
are the costs of the turbine itself, including transport from the factory to the place where the turbine is erected.

ISO
International Organization for Standardization.

K-factor
is a weighting of the harmonic load currents according to their effects on transformer heating. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects. The K-Factor is used by transformer manufacturers and their customers to adjust the load rating as a function of the harmonic cur...

Kilohertz
(kHz) is a unit of measurement of frequency. It is a unit of alternating current (AC) or electromagnetic (EM) wave frequency equal to one thousand hertz (1000 Hz).

Learning rate
is a learning curve parameter. It is estimated on available data for wind turbines and tells you the achieved reduction in specific production costs.

Levelised costs
the present-day average cost per kWh produced by the turbine over its entire lifetime, including all costs – (re-)investments, operation and maintenance. Levelised costs are calculated using the discount rate and the turbine lifetime.

Load
means an end-use device or customer that receives power from the electricity system. Load should not be confused with demand, which is the measure of power that a load receives or requires.

Load-frequency control
(LFC) see secondary control.

Local ownership
is a way of community involvement based on the fact that local residents can own shares in and obtain personal benefits from local developments. There is a significant relationship between share ownership and positive attitudes towards wind farms, and local ownership and levels of wind implementation.

Low voltage
(LV) below 1000 V.

Low-voltage ride-through
(LVRT) see fault ride-through.

Market acceptance
refers to the process by which market parties adopt and support (or otherwise) the energy innovation. Market acceptance is proposed in a wider sense, including not only consumers but also investors and, very significantly, intra-firm acceptance.

Medium voltage
(MV) typically 10 to 35 kV.

Met mast
a mast or tower which carries meteorological instrumentation (typically wind speed transducers at several heights and wind direction, air temperature and pressure transducers).

Microvolts/cm
(μVcm−1) is a unit of measurement of electrical fields.

Millitesla
(mT) is a unit of measurement of static magnetic fields.

Minigrid
is a distribution network usually operating only at low voltage and providing electricity supply to a community. It is supplied by one or more diesel generators, wind turbines, mini-hydro generators or solar photovoltaics.

Minute reserve
(15-minute reserve) see tertiary control.

Multiplier/multiplicator
for employment, this measures the direct and indirect employment effect of producing €1 million worth of output from the wind turbine manufacturing sector. Basically, it assumes that it is valid to multiply total wind turbine manufacturing in euros with a factor giving the necessary employment to produce this output. Series of multipliers fo...

N-1 criterion
is a rule that requires elements remaining in operation after the failure of a single network element (such as a transmission line/transformer or generating unit, or in certain instances a busbar) to be capable of accommodating the change of flows in the network caused by that single failure.

Net metering


Net transfer capacity
is the maximum value of generation that can be wheeled through the interface between the two systems without leading to network constraints in either system, taking into account technical uncertainties about future network conditions.

Network power frequency
characteristic defines the sensitivity, given in megawatts per hertz (MW/Hz), usually associated with a (single) control area/block or the entire synchronous area, which relates the difference between scheduled and actual system frequency to the amount of generation required to correct the power imbalance for that control area/block (or, vice versa...

Nitrogen oxide
(NOx) is a product of combustion from transportation and stationary sources. It is a major contributor to acid depositions and the formation of ground level ozone in the troposphere. It is formed by combustion under high pressure and high temperature in an internal combustion engine. It changes into nitroge...

Numerical weather prediction
(NWP) means weather forecasting by computational simulation of the atmosphere. O

Offshore
wind generation plant installed in a marine environment.

Offshore wind developments
are wind projects installed in shallow waters off the coast.

Onshore wind developments
are wind farms installed on land.