Want to be a wind farmer?

Interest in wind industry is increasing due to high oil prices and a cleaner public energy focus. Wind technology is evolving, and investors are open to the idea of being wind farmers. However, DNV suggests stakeholders seek deeper insight into reliability and safety, and not just the financial and environmental risks involved, before turning business ideas into reality.

Considering the past year’s focus on cleaner energy and higher oil prices, the profitability of wind energy has increased to the extent that there is now unparalleled interest for investing in wind farms. However, there are a number of technological, environmental and financial challenges, in addition to certification and verification processes, which investors and developers should have deep knowledge of before embarking on a wind project.

Safeguarding the industry
Since the early days of the wind industry in the 1980s, independent certification by third parties has played an important role in minimizing the number of design errors and creating confidence between the manufacturers, developers, owners, finance and insurance companies and authorities. Due to the impressive technological pace of the industry, wind turbines are designed and type tested within narrow timeframes, with rapidly growing turbine dimensions.

As a minimum, wind turbines generally have type certification according to a recognized certification scheme – typically IEC (2005), Dutch or Danish – and additional local national requirements may also be applicable to the chosen project-specific approval scheme. DNV offers type certification services according to a scheme defined by the International Electrotechnical Commission (IEC) in the document IEC WT-01 and also according to various other national schemes. Type certification comprises design evaluation, type-testing and manufacturing evaluation. Type certification is concluded by the issue of a type certificate that must be maintained.

The design evaluation is normally carried out as a review of the design documentation submitted by the manufacturer, and in addition independent analyses should be carried out. Independent load calculations are performed using an aeroelastic program that is different from the one used by the manufacturer. For this purpose, DNV uses two advanced aeroelastic programs: FLEX5 and HAWC. DNV’s program NV5053 is used for the independent gear-rating calculations, and has been developed on the basis of the DNV classification note 41.2. FEM analysis may also be carried out on critical components.

Type testing is performed in order to verify the wind turbine performance with respect to power production, noise and power quality. Furthermore, type tests and measurements are carried out to verify the load calculations and blade design. Type testing will normally comprise power production/power curve, noise emission, functional testing, load measurements, and dynamic and static full-scale blade testing.

For the manufacturing evaluation, DNV carries out an audit of a representative turbine according to IEC WT01. Wind turbine manufacturers normally operate a certified quality system according to the ISO 9000 series. For such certified quality systems, an audit is performed to confirm that the work instructions, purchase specifications, quality control procedures and records, etc. comply with the design covered by certification. Extended audits are relevant for quality systems that are not certified.

When the wind turbine – subject to type certification through design evaluation, type testing and manufacturing evaluation – is found to comply with the applicable code/standards/require¬ments, a final verification report and a type certificate will be issued, with a typical period of validity between 1-5 years with extensions. Annual surveys of randomly selected turbines are then carried out during the validity period to verify the manufacturer’s design procedures, as well as their maintenance and implementation in relation to the initially approved design procedures and design parameters.

Making offshore wind energy a breeze
Wind power is gaining momentum in the quest for renewable sources of energy, and more and more wind farms are now situated offshore where the winds blow harder and the turbines represent less of an issue in terms of visual interference with the surrounding landscape. Because of these conditions, the planning and execution of offshore wind farm projects involve a number of particular technological and process-related challenges.

Each concept needs to be adapted to capture the opportunities and overcome the challenges at hand. In turn, this means that the certification approach needs to be site-specific. One particular challenge is to ensure that the turbine and its foundation work safely together as an integrated structure. Often, problems only become evident and have to be corrected during installation. This means that the certification partner will need to respond quickly to avoid unacceptable project delays. DNV’s ability to provide online assistance during installation has proven to be an essential part of the delivery, helping the operator combine total project safety with efficient installation and operation.

It is recommended that the certification process starts as soon as the data acquisition for soil, wind and wave site-specific investigations starts. A step-by-step certification will minimize the total project risk, and the following phases can be concluded with an approval as part of the final project certification: design basis, including external conditions; concept design for tender package; detailed design; manufacturing; and installation.

The basis for the project certification is the DNV Offshore Standard DNV-OS-J101, “Design of
Offshore Wind Turbine Structures”. The standard was originally issued in 2004 and is currently being revised to serve as an interpretation of the new IEC 61400-3 standard acting as the basis for the structural design of offshore wind turbines.

Safeguarding investor capital
Second and third party verification services are also offered to the wind industry in all stages of the wind turbine design, as well as during the wind farm project development. Verification offers confidence to the key stakeholders during the wind industry’s typically complex developments.

During the design development phase, this may include verification of the design basis, a review of engineering assumptions and approaches, an independent technical review of design concepts , and verification of phase completion. During the wind farm project development phases, this may include verification of wind estimates and the project basis, verification of the turbine design, verification of the manufacturing of wind turbines and major components (particularly blades), verification of specialist equipment fitment, and verification of transport and installation.