? Design
? Installation and decommissioning
? Operation and maintenance / reliability
2. Grid integration and electrical transmission
3. Social, political and environmental issues
4. Recent and current activities
5. Resources and economics
Annexed to this summary report is a table with the key RTD actions
identified by the project members. Also given in the table is a ranking in
terms of the timescale on which progress must be made and the importance of that
RTD action for the progression of the industry.
A summary of the table is presented in the following sections.
In the short term with highest priority, inherent design for improved
reliability and installation expediency must be addressed. The logistical
difficulties presented by locating turbines offshore imply a much improved
reliability requirement be placed on offshore specific wind turbine variants,
reliability levels which must exceed those currently displayed on onshore wind
farms. Manufacturers involved in offshore wind are currently addressing a
fuller understanding of the effects of a maritime climate on wind turbines, and
results are awaited for recently introduced technological improvements.
The cost of installation is an inherent economic problem to the
viability of an offshore wind farm mainly due to the weather constraints and
type of equipment required. Traditionally, floating cranes and jack-up
barges have and continue to be utilised by offshore wind farm developers,
equipment which in general has been developed and costed for oil and gas
exploitation. There must be concerted action to eliminate the need for
expensive vessels to be employed at installation and major component
change-out. Consideration must also be given to the loads experienced by
large wind turbine components during transportation and erection at sea.
The best-practice approach to support structure design continues to be
a medium term goal, with consideration of installation for increasingly arduous
site conditions.
In the medium term with highest priority, component development
particularly with the mandate to improved reliability and maintainability
becomes a feature. Aerolastic and structural design of rotor blades must
evolve with the continued preference for larger and higher performance wind
turbine units.
Within this timescale with less urgency, the goals for optimal
structural design and design for reliability and maintainability come to the
fore. As the wind power industry evolves, the development of standards
relating to wind turbine design is bound to mature in proportion. The
standards currently being developed by bodies such as the IEC should be extended
to include all aspects of offshore wind turbine design. The development and
validation of such standards is important because the lack of reliable and
commonly accepted design guidelines has the effect of reducing the level of
confidence with which offshore wind projects can be financed and implemented.
Optimal structural design will focus on recurrent wind turbine aspects
such as reduction of fatigue loading by introduction of inherent flexibility,
and more sophisticated control as examples. More particularly, the
features of offshore environment will drive closer attention to issues such as
wave induced tower vibrations, ice loading, and positive aspects such as
allowance of higher blade tip velocities.
Design for reliability and reduction of scheduled and unplanned
maintenance will include obvious topics for improvement such as enhanced
corrosion and lightening strike protection and reduction in overall number of
components. More ambitious plans include the modular design of turbines to
facilitate change-out and installation, and justification for the introduction
of redundancy at component and turbine level.
Finally within this priority category, the conceptual design of large
wind turbines and wind farms should be explored for technological and commercial
viability.
Efforts over the next five year period with low urgency shall focus on
innovative and evolutionary design of structures and alternative rotor blade
numbers and hub configuration, namely the reduction in blade number to two
coupled with the elimination of a teetering mechanism.
Long term goals for offshore technology will address siting structures
in remoter/deeper water and may include support structure rationalisation
methods such as multi-rotor. With the advancement in tidal stream turbine
and wave technology, there may be scope for combined wind/wave structural
innovation mounted on support structures which have life-ratings well above the
energy capturing devices that mount them to facilitate re-use.
Research into the engineering and economic feasibility of floating wind
turbine systems for deep water sites should also be considered as a long term
objective.
Also in the immediate term, occupational health and safety standards
and procedures should be developed in line with the rapid development of
offshore wind farms. While there is no need to constrain the wind power
industry to the same levels of safety required for offshore oil and gas
exploitation, the working practices applicable to offshore are far more life
threatening than the equivalent onshore practices.
In the medium term, to allow offshore working a wider weather window,
installation methodologies should be made less sensitive to wind/wave
conditions. The development of erection techniques may be subject to
review where more assembly operations are conducted onshore prior to
transportation to site.
Within the next five years but with lesser priority is to consider
decommissioning requirements at conceptual design and build-in features which
will assist at the inevitable later stages.
A related priority is the development of mooring systems which provide
safe access to personnel alighting from a vessel and disembarking from a turbine
access platform. The development of operation and maintenance models
should continue, particularly taking cognisance of operational data and
experience, providing input data when choosing a suitable site specific
maintenance strategy.
In the medium term, the development of inexpensive purpose-built
vessels should be considered. Future offshore wind farms may be large
enough to justify the purchase of a dedicated vessel for installation, O ? M,
and decommissioning activities. With recent advancements in SCADA
technology, condition monitoring of components which are susceptible to wear and
failure must be explored to reduce the cost and requirement for site
visits. Innovative maintenance strategies should be explored in
conjunction with the development of O?M models.
Of lesser urgency is the requirement to explore HVDC multiple (up to
35kV) and single grid (up to 200kV) link designs, the effect of LSOWE projects
on grid operation.
In the medium term, there should be the development of HVDC converter
stations, cabling and associated infrastructure. A fundamental stumbling
block to further advances in offshore wind exploitation is the scarcity of
suitable existing points of grid connection and grid fragility. A study of
the relationship between technical-economical offshore wind energy potential and
the cost of providing adequate grid reinforcement is required.
Of lesser priority in this timescale, is the requirement to eliminate
offshore transformers by either generation at high voltage or offshore
substation development. Wind turbines can be used to assist grid control
in terms of power factor and voltage control, and the cost associated with the
development of this ability should be explored. The availability
statistics of a wind farm are affected by grid faults, and there is merit in
developing turbines which can withstand transient external faults without
consequential disconnection from the network.
Efforts over the next five years with lower priority should focus on
socially acceptable methods for apportioning the grid integration cost of
offshore wind farms from energy provider to energy user. A study is
required to address whether the existing safety distances between subsea cables
can be reduced.
Long term goals for grid integration and electrical transmission issues
include wind farm control using centralised converters, and finding suitable
methods for power storage.
The environmental impact particularly at the construction stage of an
offshore wind farm requires careful assessment, and mitigating measures
implemented to reduce the effects on natural surroundings, e.g. piling
effects on marine life. There is a need for ongoing studies identifying
sensitive and protected areas which are not suitable for development.
In the short term with less priority, validation of predicted visual
assessment must be carried out to ascertain the accuracy of models in varying
weather conditions.
In the medium term, environmental impact data from existing offshore
wind farms should be disseminated and appraised for future developments.
Clearer definition and standardisation of marking requirements may negate
conflict from the shipping industry.
Within the next five years but of less priority is the need for
improved public relations to counter the often ill-informed views of national
populations. This task may be assisted by a willingness to share
information through visitor centres for example, and involve local populations
throughout the development process.
The biological impact of developments as affecting bird, mammal and
marine life must be assessed, and every measure taken to protect and enhance
where possible natural habitats. The effect of acoustic and
electromagnetic noise emissions must be studied and mitigation measures
incorporated in wind turbine and wind farm design.
In the medium term the owners of early offshore wind farm projects
should be actively encouraged to freely disseminate and evaluate them with a
view to steering future projects.
The potential benefits to employment and benefits to European
industrial development should continue to be assessed.
In the medium term, development and validation of models assessing
inshore joint wind/wave and wave induced current simulations is required.
Wind data collection methodology should be improved to provide valuable reliable
data at a reasonable cost. There is a need for concerted European and
national wind monitoring programmes.
On a lesser priority rating, there may be a requirement for finding
test sites which exhibit benign to extreme offshore wind conditions while
providing easy access, e.g. small islands with a causeway.
| Task | Timescale (2/5/10 yrs) | Importance (Low/Med/High) | ||
| Better definition of design criteria and extreme wind/wave recurrence periods for inshore waters | 2 | High | Generic R?D | Offshore Technology |
| Development and validation of models for reliable prediction of fatigue and extreme loads | 2 | High | Generic R?D | Offshore Technology |
| Assess reliability of existing spectral wave models | 2 | High | Generic R?D | Offshore Technology |
| Measurement campaigns on early projects | 2 | High | Generic R?D | Offshore Technology |
| Review of safety factors | 2 | High | Generic R?D | Offshore Technology |
| Investigation of breaking waves, shallow water effects and resulting loads. | 2 | High | Generic R?D (technology transfer) | Offshore Technology |
| Further research on geotechnics of inshore waters - improve understanding of the interaction of seabed/soil characteristics with system dynamics - sensitivity of resonant frequencies, fatigue loading etc. | 2 | High | Generic R?D (technology transfer) | Offshore Technology |
| Improved dissemination of knowledge of offshore marine related construction procedures and techniques amongst designers/developers | 2 | High | Technology transfer | Installation and decommissioning |
| Reduce time for offshore working | 2 | High | Installation and decommissioning | |
| Minimisation of offshore lifting operations | 2 | High | Installation and decommissioning | |
| Safety of personnel | 2 | High | O?M/reliability | |
| Remote control facilities to allow manual over-ride of turbine control system from an onshore base | 2 | High | O?M/reliability | |
| Development of suitable wind turbine (generator) models for dynamic grid simulation codes (in particular for variable speed wind turbines, and including mechanical dynamics) | 2 | High | Grid Integration ? Energy Supply | |
| Development of forecasting methods for wind energy production up to several days ahead | 2 | High | Resources ? Economics | |
| Mean wind speeds | 2 | High | Resources ? Economics | |
| Vertical wind speed and turbulence profile | 2 | High | Resources ? Economics | |
| Evaluation and prediction of wake effects and turbulence on power output of large wind farms | 2 | High | Resources ? Economics | |
| Risk assessment (construction cost, delay risk, energy production, operating costs, availability) | 2 | High | Resources ? Economics | |
| Joint wind/wave loading on short time scales for weather forecasting, power output and improved maintenance scheduling | 2 | High | Resources ? Economics | |
| Database of information on existing operational offshore projects and research work | 2 | High | Recent ? Current Activities ? Prospects | |
| Fish: Manage public awareness of ?stunned? fish during construction (pile driving) | 2 | High | Social, Political ? Environmental Aspects | |
| Air: Safety of civil air traffic | 2 | High | Social, Political ? Environmental Aspects | |
| Air: Safety of air traffic related to project | 2 | High | Social, Political ? Environmental Aspects | |
| Air: Studies of disturbance to radar | 2 | High | Social, Political ? Environmental Aspects | |
| Identification and avoidance of sensitive areas | 2 | High | Social, Political ? Environmental Aspects | |
| Work to establish whether the different conditions offshore (particularly turbulence) affect the pros and cons of variable speed. | 2 | Medium | Incremental development | Offshore Technology |
| Reduction of need for floating cranes by development of internal cranage capability for lifting all, including largest, components | 2 | Medium | Incremental development | Offshore Technology |
| Controlled nacelle environments | 2 | Medium | Incremental development | Offshore Technology |
| Consideration of transport and installation loads | 2 | Medium | Generic R?D | Offshore Technology |
| Better prediction of loading of various foundation configurations - validation through measurement programmes | 2 | Medium | Generic R?D | Offshore Technology |
| Decision as to whether components (namely turbine and support structure) are treated in an integrated way during design, reducing conservatism. | 2 | Medium | Generic R?D | Offshore Technology |
| Control costs of overall installation process | 2 | Medium | Installation and decommissioning | |
| Occupational health ? safety standards to be reviewed for offshore work | 2 | Medium | Installation and decommissioning | |
| Development of mooring systems | 2 | Medium | O?M/reliability | |
| Development of O?M models | 2 | Medium | O?M/reliability | |
| High voltage grid link designs, e.g.; multiple medium voltage links (up to 35 kV), single high-voltage link (100 to 200 kV), and HVDC | 2 | Medium | Electrical transmission ? grid connection | |
| Evaluation of effect of early LSOWE projects on grid operation | 2 | Medium | Grid Integration ? Energy Supply | |
| Quantify uncertainty in energy yield estimates | 2 | Medium | Resources ? Economics | |
| Early assessment taking account of distance from shore and nature of viewpoints | 2 | Medium | Social, Political ? Environmental Aspects | |
| Validation of visual assessment | 2 | Medium | Social, Political ? Environmental Aspects | |
| Air: Safety of air crew training | 2 | Medium | Social, Political ? Environmental Aspects | |
| Avoidance of site works during sensitive time periods | 2 | Medium | Social, Political ? Environmental Aspects | |
| Aeroelastic and structural design of large rotor blades | 5 | High | Generic R?D | Offshore Technology |
| Develop low maintenance/high reliability components | 5 | High | Incremental development | Offshore Technology |
| Reduce sensitivity to wave / wind conditions | 5 | High | Installation and decommissioning | |
| Development of purpose built jack-up barges, floating barges and landing craft | 5 | High | O?M/reliability | |
| Develop condition monitoring via SCADA systems (enhanced capability, 2 from 3 decision-making, improved reliability) | 5 | High | O?M/reliability | |
| Development of HVDC converter stations, cabling and insulation | 5 | High | Electrical transmission ? grid connection | |
| Study of the impact of grid limitations on offshore wind energy potential ; study of the relationship between technical-economical off-shore wind energy potential and cost of required grid reinforcements | 5 | High | Grid Integration ? Energy Supply | |
| Development ? validation of inshore joint wind/wave simulations | 5 | High | Resources ? Economics | |
| Cost reduction and reliability improvement for methods for offshore wind data collection | 5 | High | Resources ? Economics | |
| Generic evaluation of LSOWE investment costs taking into account cost influencing factors (distance from shore, water depth, wind and wave climate, soil conditions, ? | 5 | High | Resources ? Economics | |
| Develop standards for offshore wind industry | 5 | High | Recent ? Current Activities ? Prospects | |
| Systematic evaluation of the results of test and demonstration projects | 5 | High | Recent ? Current Activities ? Prospects | |
| Baseline and impact studies from individual projects to be disseminated and jointly appraised | 5 | High | Social, Political ? Environmental Aspects | |
| Ships: Clearer definition of marking requirements | 5 | High | Social, Political ? Environmental Aspects | |
| Conceptual design of large wind turbines and wind farms (e.g. unit power rating greater than 5MW with rotors greater than 100m diameter, wind farm rating several hundred MW) | 5 | Medium | R?D support of potential manufacturers | Offshore Technology |
| Higher blade tip velocities . | 5 | Medium | Incremental development | Offshore Technology |
| Development of standards | 5 | Medium | Generic R?D | Offshore Technology |
| Reduction of fatigue loading by introduction of inherent flexibility, e.g. flexible towers, compliant couplings, etc. | 5 | Medium | Incremental development | Offshore Technology |
| Reduction of fatigue loading through more sophisticated control. (Benefits of greater sophistication to be balanced against potential reliability problems.) | 5 | Medium | Incremental development | Offshore Technology |
| Improve corrosion protection systems | 5 | Medium | Incremental development | Offshore Technology |
| Enhanced lightning protection systems | 5 | Medium | Incremental development | Offshore Technology |
| Reduction in overall number of components (e.g. new drivetrain concepts - Windformer, Aerodyn Multiwind, permanent magnet generators) | 5 | Medium | Innovation support | Offshore Technology |
| Building in redundancy | 5 | Medium | Incremental development | Offshore Technology |
| Modular design approach to facilitate changeouts | 5 | Medium | Incremental development | Offshore Technology |
| Sectional components to facilitate ease of transportation and lifting | 5 | Medium | Incremental development | Offshore Technology |
| Development ? validation of metocean prediction models | 5 | Medium | Generic R?D | Offshore Technology |
| ‘Smart tower?which can alter natural frequencies | 5 | Medium | Incremental development | Offshore Technology |
| Research into ice loading, support structure design to deal with ice | 5 | Medium | Generic R?D | Offshore Technology |
| Optimise the cost-effectiveness of offshore wind structure installation operations by making use of novel construction sequences and scenarios | 5 | Medium | Installation and decommissioning | |
| Develop and analyse innovative maintenance strategies | 5 | Medium | O?M/reliability | |
| Offshore substation design development | 5 | Medium | Electrical transmission ? grid connection | |
| Development of methods to allow LSOWE plants to withstand transient external faults without disconnecting from the network | 5 | Medium | Electrical transmission ? grid connection | |
| Elimination of offshore transformers, generation at high voltage (AC or DC) | 5 | Medium | Electrical transmission ? grid connection | |
| System analysis based on future LSOWE plans, taking account of spatial correlation of supply, existing system characteristics, future plans for cross-border links, etc. | 5 | Medium | Grid Integration ? Energy Supply | |
| Analysis of the economical effect (cost) of requiring LSOWE plants to contribute to primary and secondary control | 5 | Medium | Grid Integration ? Energy Supply | |
| Evaluate feasibility of demand-side measures to accept high penetrations of LSOWE | 5 | Medium | Grid Integration ? Energy Supply | |
| Analysis of the effect on the transmission grid (at local, national, and international scale), including additional network costs and benefits, to accept offshore wind farms at high wind penetrations. | 5 | Medium | Grid Integration ? Energy Supply | |
| European and national wind monitoring programmes | 5 | Medium | Resources ? Economics | |
| Benefits to employment | 5 | Medium | Recent ? Current Activities ? Prospects | |
| Benefits to European industrial development | 5 | Medium | Recent ? Current Activities ? Prospects | |
| Birds: Layout design to accommodate flight paths, where these are defined. | 5 | Medium | Social, Political ? Environmental Aspects | |
| Mamals: Avoidance of sensitive habitats | 5 | Medium | Social, Political ? Environmental Aspects | |
| Mamals: Minimisation of atmospheric and subsea noise levels during construction and operation | 5 | Medium | Social, Political ? Environmental Aspects | |
| Mamals: Study effect of electromagnetic fields | 5 | Medium | Social, Political ? Environmental Aspects | |
| Fish: Minimise effect of structures and cabling on stocks | 5 | Medium | Social, Political ? Environmental Aspects | |
| Fauna: Study effect of electromagnetic fields | 5 | Medium | Social, Political ? Environmental Aspects | |
| Fauna: Investigate value of local measures to enhance habitat | 5 | Medium | Social, Political ? Environmental Aspects | |
| Hydrography: Investigation of appropriate foundation design | 5 | Medium | Social, Political ? Environmental Aspects | |
| Hyrdography: Guidelines for site works | 5 | Medium | Social, Political ? Environmental Aspects | |
| Promotion of openness and local involvement | 5 | Medium | Social, Political ? Environmental Aspects | |
| Ongoing PR work to counter poor publicity | 5 | Medium | Social, Political ? Environmental Aspects | |
| Maintain good standards of noise emission despite increases in turbine size and tip speed | 5 | Medium | Social, Political ? Environmental Aspects | |
| Ships: Collation of collision risk analyses | 5 | Medium | Social, Political ? Environmental Aspects | |
| Alternative rotor blade numbers and hub configuration | 5 | Low | R?D support of potential manufacturers | Offshore Technology |
| Assess importance of wave-driven fatigue on offshore wind structures | 5 | Low | Generic R?D | Offshore Technology |
| Optimal design of interface between tower and support | 5 | Low | Incremental development | Offshore Technology |
| Innovative and evolutionary design of structures | 5 | Low | Generic R?D | Offshore Technology |
| Design for decommissioning | 5 | Low | Installation and decommissioning | |
| Develop offshore converter designs (optimisation of power factor and voltage control) | 5 | Low | Electrical transmission ? grid connection | |
| Development of methods to decrease currently required safety distances between sea cables | 5 | Low | Electrical transmission ? grid connection | |
| Harmonization of electrical protection and reactive power requirements | 5 | Low | Grid Integration ? Energy Supply | |
| Research in support of finding a socially acceptable way of allocating the system cost created by LSOWE (grid reinforcement, priority access, increase control requirements for conventional plants, ? to the different stake-holders (LSOWE project owners,all generators, all customers, all tax-payers) | 5 | Low | Grid Integration ? Energy Supply | |
| Provide tests sites with suitable offshore conditions, e.g. small islands | 5 | Low | Resources ? Economics | |
| Design for deeper waters including floating systems. | 10 | Medium | Generic R?D | Offshore Technology |
| Wind farm control (e.g. centralised converter) | 10 | Medium | Electrical transmission ? grid connection | |
| Power storage systems development and cost reduction | 10 | Medium | Electrical transmission ? grid connection | |
| Research into multi-rotor systems | 10 | Low | Generic R?D | Offshore Technology |
| Combined wind/wave/tidal energy devices | 10 | Low | Generic R?D | Offshore Technology |
| Design for future re-use | 10 | Low | Incremental development | Offshore Technology |