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ACS Advanced Control Strategy
Strategy to make use of Advanced Control Systems by modelling the wind turbine using computing techniques such as proportional-integral-derivative (PID), soft computing or fuzzy logic.
Airfoil Airfoil section
Cross section of an aerodynamic wing, blades (of a wind turbine), wings, sails etc.
AEP Annual Energy Production
Estimation of energy produced annually based on local wind speed distribution at hub height and power curve of the chosen wind turbine. AEP is an ideal estimation, i.e. uncertainties, technical losses, downtime etc. is not included.
AIM Asset Integrity Management
Discipline of business processes, systems, tools, competencies and resources needed to ensure integrity throughout the entire asset life time.
AM Asset Management
Coordinated activity of an organization to maximize value from assets, such as a wind farm. Asset Management refers to the full life time of an asset.
Percentage calculated on a annual basis describing the availability of a wind turbine for operation. It can be based on different variables, e.g. time- or production-based. Furthermore availability is often divided in two categories: technical and contractual availability, latter adjusted for e.g. contract clauses and exemptions.
BoP Balance of Plant
Supporting components and auxiliary systems of a power plant needed to deliver energy, other than the generating unit itself. In the case of wind energy, BoP often comprises inter-array and export cables, off- and onshore substations, as well as foundations.
BFT Beaufort scale
Scale describing wind force and wave height conditions, ranging from 0 (calm) to 12 (hurricane).
Boat landing Boat Landing
Access arrangement for service vessels to access a offshore wind turbine. The type of boat landing depends on foundation type.
BSH Bundesamt für Seeschifffahrt und Hydrographie
German authority in charge of regulations and permits granting to build offshore wind farms within German waters.
CAPEX Capital Expenditure
Investment costs (non-recurring costs) generated over lifetime of a wind farm comprising of pre-development, production, installation, decommissioning, disposal, site clearance, as well as investments during operations.
COD Commercial Operation Date
Point in time (particular date) for transition from construction to operations. The COD can be calculated in different ways. For example, it could be defined as the point in time when the last WTG gets into operations or the average of the CODs of all WTGs. Before COD, there is usually a final walk-through and short test period (e.g. 240 hours without stop).
CMS Condition Monitoring System
Vibration monitoring system primarily used on rotating parts, e.g. bearings and main shaft. Also known as Turbine Condition Monitoring (TCM).
CTV Crew Transfer Vessel
Access solution used for safe transfer of technicians, their tools and minor parts to a offshore wind turbine or substation.
DDS Data Distribution Service
Object Management Group (OMG) machine-to-machine (also called middleware) standard that aims to enable scalable, real-time, dependable, high-performance and interoperable data exchanges using a publish–subscribe pattern. DDS is used in the wind turbine controller software.
DC Daughter Craft
Fast tender boat used for accessing the offshore wind turbine from a SOV. It is suitable for lower wave heights than CTVs. Daughter crafts are obliged to stay within a certain distance to their SOV.
Davit Crane Davit Crane
Crane type lifting items between the wind turbine and service vessels. The Davit crane is most often located on the External Access Platform and/or the quay side in the harbour to lift components onto the CTV / SOV.
DECEX Decommissioning Expenditure
Costs for decommissioning a wind farm or turbine. Studies show it is approximately 5-10% of the Capital expenditures, but is largely dependent on the specific site and whether it is decied to repower the farm or remove it entirely.
DNP Defect Notification Period
Period where defects can be claimed under the purchase contract (TSA).
DRA Design Risk Assessment
The act of estimating potential risk within a design process. It can be carried out throughout the entire design phase to prevent potential failures and errors and achieving higher reliability for the product (e.g. a new type of foundation or transformer used for a wind turbine).
DEVEX Development Expenses
Expenses before signing the main construction contracts, typically including lease and development costs. In some cases DEVEX is included as a part of CAPEX.
DD Direct Drive
Drive-train design set-up of a wind turbine, whereby the rotor is connected directly to the generator via the main shaft. The direct drive design eliminates the need for a gearbox, yielding different specifications and design for the generator.
DAB Dispute Adjudication Boards
A person or a panel of individuals (usually 3) that under the terms of the contract provide: (1) non-binding recommendations to the contracting parties on issues arising; and/or (2) a binding decisions in relation to such matters.
Grid Electrical Grid
System which connects generating plants, e.g. wind farm to the consumer through distribution channels consisting of transmission lines and substations.
ESP Electrical Service Platform
See OSS. ESP is the term used in the United States of America.
EoL End of Life
Point in time referring to the wind farm approaching end of lifetime (after 20 to 25 years). There are different options to be considered: (1) Life time extension, (2) Repowering, (3) Decommissioning.
EoW End of Warranty
Point in time where a wind turbine or a wind farm goes out of warranty under the supply agreement. Typically after 2 or 5 years of operation.
EPC Engineering, Procurement, Construction
Type of "turnkey" contract comprising the full scope of engineering, procurement, and construction.
EPCI Engineering, Procurement, Construction, Installation
Type of "turnkey" contract comprising the full scope of engineering, procurement, and construction as well as installation.
EHS Environment, Health and Safety
EIA Environmental Impact Assessment
Report comprising a number of investigations of the impact on the environment by building and operating, in example, a wind farm. The EIA must be completed for granting permission to develop a wind farm. It contains aspects such as bird mitigation, installation and operational noise, endangered species and surveillance plan over the lifetime of the farm. Usually the investigations and the related report is developed by external specialists. The EIA reports determine whether or not the project is in line with environmental regulations.
EQP Equipment Platform
Platform attached on the Transition Piece (TP) of an offshore wind turbine generator (OWTG). Switchgear, lockdown system and elevator are often placed on the EQP.
EC Export Cable
Cable(s) exporting the generated electrical power from the offshore substation (OSS) (or directly from the wind farm if an OSS is not a part of the project) to onshore substation.
EAP External Access Platform
Platform placed on TP to access the offshore wind turbine from a marine vessel, e.g. CTV or SOV.
FAT Factory Acceptance Tests
Testing and validating whether components meet stated requirements before leaving the factory.
FAS Fall Arrest System
Safety system in a wind turbine enabling working at elevated heights.
FID Final Investment Decision
The FID is a key milestone in wind farm development. Before FID, activities such as business case development, completion of permits and financial arrangement are carried out. After successful FID, contracts for all major equipment can be placed, allowing procurement and construction to proceed and engineering to be completed.
The foundation of a wind turbine ensures stability to the rest of the structure. Various concepts are available for both onshore and offshore purposes. An offshore foundation consist of two major components; an upper part called Transition Piece (TP) and a bottom part varying according to site specifics. The two main types are Monopile or Jacket. The latter is used for larger water depths.
FEED Front End Engineering Design
An engineering design approach considering technical requirements and rough investment costs to enhance project cost planning and controlling.
GACP Galvanic Anode Cathodic Protection
Protection system placed externally on offshore foundations to prevent corrosion.
GPS Global Positioning System
A satellite-based radio-navigation system to determine an exact position on ground or at sea.
GWO Global Wind Organisaiton
Non-profit organisation of wind turbine owners and manufacturers. It aims at ensuring a safe and injury free working environment within the wind energy industry.
GBS Gravity Based Structure
Foundation type using gravity to position the turbine onto the seabed. It is often a concrete foundation placed on a stable seabed and the mass keeps it in place and position.
HSE Health, Safety and Environment
HSE comprises all processes and functions dedicated to preserve health, safety and environment. It is sometimes referred to as EHS.
HHO Helicopter Hoist Operation
Operational task requiring helicopter, a qualified crew and possibly a helicopter deck.
HAWT Horizontal Axis Wind Turbine
Mostly used type of wind turbine, named after horizontal drive train design. Thus blades are rotating vertically.
ICCP Impressed Current Cathodic Protection
Protection system placed internally on offshore foundations to prevent corrosion.
IAC Inter-Array Cable
Cable network within wind farm connecting between wind turbine and a connection point, e.g. substation. Typical voltage 33kV or 66 kV. There is a certain number of wind turbines connected to one string before the array cable connects to the offshore substation.
ISO 55000 International Organization for Standardization 55000
A standard specifying requirements for an asset management system within the context of an organization. It refers to all kinds of assets, tangible and non-tangible. In the case of wind industry it refers to the management of physical assets.
ITT Invitation to Tender
A formal request for supplier offers; term used across all industries.
JUB Jack-Up Barge
A type of Jack-Up vessel with jacket legs used for offshore wind turbine installation, foundation installation and exchange of major wind turbine components. The hull has a shape of a barge - this is where it got its name from.
Jack-up Jack-Up Vessel
Vessel for transporting, installing and changing larger components on a wind turbine. It is able to 'jack-up', meaning it has 4 self-elevating legs which fix the vessel on the seabed. This ensures a safe lift of heavy components and precise installation.
Jacket Jacket Foundation
Foundation type having a lattice structure, with heritage in offshore Oil & Gas platforms. Mainly used for larger water depths and on specific seabed conditions.
J-tube Jejunostomy Tube
Tube named after its shape leading the inter-array cable or export cable from bottom of the wind turbine through the foundation down to the seabed (or longer) for protecting of cables from twisting, bending and collision.
LE Leading Edge
Describing the edge along the entire Wind Turbine Blade, where the wind flow has its first contact with the blade.
Leading Edge Protection LEP
Protective layer(s) placed on the leading edge of a blade to prevent environmental erosion from e.g. small particles such as rain drops, hail, grains of sands. Blades are more exposed to erosion, because of the rotational movement, resulting in a higher collision impact contrary to static components such as the tower or nacelle.
LCoE Levelized Cost of Energy
Average cost per kWh produced by a wind turbine taking into account its entire lifetime. Costs included are all, DEVEX, CAPEX, OPEX and DECEX costs, thus non-recurring and recurring costs.
Lift Boat Lift Boat
See Jack-Up vessel.
LTP Long Term Program Service Agreement
Agreement between an owner of a wind farm and a contractor. The contractor is hired to service the wind turbines following the instructions agreed on in the LTP.
LMU Low Speed Monitoring Unit
Unit which is monitoring vibrations on components operating at low speed, e.g. detecting irregular changes and potential failure at the main bearing at an early stage.
MSL Mean Sea Level
The mean sea level at a given location. It influences for example the design of the offshore wind turbine foundation.
MVOW MHI Vestas Offshore Wind
Joint venture of Mitsubishi Heavy Industries and Vestas Wind Systems with focus on manufacturing, installing and servicing offshore wind turbines.
MP Monopile Foundation
Special type of main bottom component of a foundation, consisting of a steel tube hammered or vibrated into the seabed. Usually cheapest offshore foundation solution, but only suitable for certain seabed conditions and water depth.
German term for Point of Common Coupling.
NIMBY Not In My Back Yard
Public phenomenon describing the opposition towards e.g. wind farms, if in their local area, while still having a general positive attitude towards renewables ("Great, but not in my backyard").
OSS Offshore Substation
Station located offshore in or close to offshore wind farm. It collects, transforms and connects power generated by offshore wind turbines to the onshore substation via export cable(s).
OWF Offshore Wind Farm
A cluster of wind turbines built at sea. Some of the important factors for building a wind farm are: (1) Distance to the shore and coupling point to the grid. (2) The water level and soil conditions, determining foundation type. (3) Environmental impact. (4) Wind and weather conditions.
OWTG Offshore Wind Turbine Generator
Wind turbine operating offshore. Designed to comply with offshore accessibility challenges and withstand harsh environmental conditions, e.g. corrosion protection, remote control and monitoring, higher mean wind speed, boat landing and helihoist platform. Sometimes shortened to OWT (Offshore Wind Turbine).
OWP Offshore Windpark
German term for Offshore Wind Farm.
OnSS Onshore Substation
Station located onshore. Receiving and converting power to a desired voltage and current. It receives power from Offshore Substation via export cables and feeds it into the grid.
OPEX Operational Expenditure
Overall recurring cost of operating and maintaining a wind farm (excluding investment costs which are part of CAPEX).
O&M Operations and Maintenance
All processes and actions ensuring the profit and integrity of a wind farm.
OEM Original Equipment Manufacturer
Company which produces and supplies a product, which then is marketed by the buyer. In the wind industry it is used to refer to the supplier of the wind turbine generator and for the main components of the substation.
PCC Point of Common Coupling
Point in an electrical system, where multiple customers or multiple electrical loads may be connected. Also see Electrical Grid.
PCu Power Curve
Curve displaying the generated power according to the average wind speed. Each wind turbine type has its own power curve characteristic, e.g. dependent on the control system.
PPA Power Purchase Agreement
Agreement between the power producer (the wind farm project) and the off-taker. It describes terms and prices for the power provided by the power producer.
PBA Production-Based Availability
The ratio of actually produced power to possible power production based on the turbine availability.
PSO Public Service Obligation
Obligations made by the European Union to ensure services of public interest, while potentially promote other initiatives e.g. levy on electricity to cover initiatives for renewables energy.
PAS 55 Publicly Available Specification 55
British Standards Institution's Publicly Available Specification for optimized management of physical assets. The PAS55 served as the basis for the ISO standards family ISO 5500x.
ROV Remote Operated Vehicle
A vehicle, which is operated remotely. This means that the operator does not have to be physically in the same location as the ROV. Examples are toy race cars or drones. Usually ROVs are used in locations with difficult or dangerous access. In offshore wind ROVs are often used to scan the seabed and inspect foundation below water. Further drones are used to inspect blades of wind turbines.
ROC Renewables Obligation Certificates
UK specific certificate to accredit power stations, that generate electricity from eligible renewable sources, e.g. wind farms. Issued by the British regulator for the gas and electricity industry: Office of Gas and Electricity Markets (OfGEM).
SP Scour Protection
Protective layer between seabed and foundation to prevent undermining the foundation by washing out sand. Consisting of rocks and stones placed around the foundation. Also used to protect export cables. Needs to be monitored by ROV or certified divers.
Gap phenomenon happening between foundation and seabed. It occurs when seabed is washed away by currents. It can result in reduced support to the foundation. Sometimes scour is referred to as a scour hole.
SRL Self Retracting Lifeline
See fall arrest system.
SAA Service and Availability Agreement
Service agreement for wind turbines provided by the OEM. The term availability refers to the availability warranty of the wind turbines.
SMA Service and Maintenance Agreement
Service agreement for wind turbines are usually provided by the OEM supplying them. The term maintenance refers to the maintenance warranty of the wind turbines.
SWA Service and Warranty Agreement
Service agreement for wind turbines provided by the OEM. The term warranty refers to the availability warranty of the wind turbines.
SOV Service Operation Vessel
Access solution used for safe transfer and accommodation of service technicians. Minor parts for inspection and repair work can be stored. Contrary to a CTV, SOVs can be used as a base for service technicians to stay in the wind farm for a longer period of time ( 4-6 weeks). A daughter craft or CTV might be used to supplement the SOV, for travel between the SOV and offshore wind turbine or substation.
SGRE Siemens Gamesa Renewables Energy
Joint venture of Siemens Wind Power and Gamesa with focus on manufacturing, installing and servicing wind turbines.
Hs Significant Wave Height
Average height of the highest one-third waves in a wave spectrum. The height of the highest waves can be nearly twice as high as the significant wave height.
SAT Site Acceptance Tests
Verification of component(s) to ensure that no damage occurred between leaving the factory and intended placement. Recommended to undertake identical tests as in Factory Acceptance Tests (FAT) to ensure comparability of results.
SCADA Supervisory Control And Data Acquisition
Computer-based system used for collecting, controlling and presenting data from various systems in a wind farm. Comprising among other: data from PLC controllers, individual process instruments, vibration and temperature measurement instruments.
TOC Taking Over Certificate
Certificate indicating the date of officially handing over individual wind turbines, foundations etc. It is used as a input for contractual agreements e.g. as starting point for TSA warranty conditions.
TBA Time-Based Availability
Percentage of time when wind turbine is technically able to produce power. It is usually calculated on an annual basis.
TE Trailing Edge
Area on the rear end along a blade, used for aerodynamic features to enhance aerodynamic performance and reduce wind shear.
TP Transition Piece
The upper part of the foundation of a wind turbine located above sea level. Boat landing and the external access (secondary steel) platform are fixed on the TP.
TSO Transmission System Operator
Term defined by the European Commission describing an entity entrusted with transporting energy, which is utilized on national or regional level, e.g. natural gas or electrical power.
TMD Tuned Mass Damper
Device mounted on structures to absorb harmonic vibrations and prevent potential failure.
TCM Turbine Condition Monitoring
TSA Turbine Supply Agreement
A binding agreement containing terms of supplying wind turbine generators. It also includes associated equipment.
VAWT Vertical Axis Wind Turbine
Special design of a wind turbine, named after the direction of the main shaft. The main shaft is placed along the tower and transverse to the wind. Advantages are the wind direction is negligible, but increased wake effect because its structure lowers the overall yield. Further it causes fluctuating loads on the structure leading to increased fatigue.
WE Wake Effect
A wind turbine extracts energy from the wind, when converting energy from the wind into electrical energy. Further it and induces turbulence caused by its movement and friction with the air mass. Following this, the wind speed upstream (in front) of a turbine is higher than downstream (behind). This affects wind turbines standing downstream of another turbine resulting in less wind energy available and a more complex wind flow due to increased turbulence. One could say that the downstream wind turbine stands in the "shadow" of the upstream wind turbine.
W2W Walk to Work
Access type between a vessel and access platform on a wind turbine. As the name implies it is a easy solution for access from vessel to an External Access Platform.
WD Weather Downtime
Period during which wind turbines are not operating due to for example unsuitable weather conditions or breakdowns. This term is also referred to as the period during which wind turbines are not accessible by a vessel.
WKP Wiederkehrende Prüfung
German term for a periodic inspection, e.g. every year.
Shear Wind Shear
Vertical and horizontal variation of the wind caused by surface roughness, obstacles and landscape contours. A special type of wind shear is shadowing, which happens when a wind turbine causes additional wind power loss and less wind power availability, due to the construction acting as an obstacle for the wind turbines downstream. Wind shear is also a source for wind flow turbulence.
WTG Wind Turbine Generator
Wind turbine operating onshore. For Offshore Wind Turbine see OWTG.
WTIV Wind Turbine Installation Vessel
Term used for the jack-up vessel used during installation.
Estimated performance of a wind turbine based on its power curve.