Sean Keller, DEX Renewables, Ireland
The rapid expansion of wind energy in the last 20 years has often resulted in a rush to get new technologies to market. Inevitably this has led to reliability issues that can directly affect a wind farm’s revenue stream through downtime and in addition there is a cost associated with additional operations and maintenance events.
Like many ISPs, DEX Renewables’ workshop in Dublin, Ireland, has a wealth of electronics repair expertise
It is a feature of these new technologies that the incidence of failure of control systems and power electronics is high in comparison with other parts of the system such as the generator. According to figures from the Institute of Solar Energy Technology in Germany, approximately 54 per cent of all wind turbine failures are due to control electronics, electrical systems and sensors.
It is also the case that unlike many of the mechanical components in a wind turbine, the majority of the electronics/electrical systems only have a single supply source the OEM. Often, therefore, the only option for owners is to purchase new replacement parts from the OEM. The parts generally have a high unit cost therefore the cost of a new replacement part can be as much as three times the cost of repairing an existing part. In addition, supply chain issues can result in costly long lead times.
For example, in 2008 a major European wind farm operator had a failure on a rotor current controller part. The company found that there was a five-month lead time for this particular part. This resulted in the operator being forced to purchase additional power from the grid to meet its contractual obligations. The cost of the extensive downtime has been estimated at around €250 000 ($353 000).
When such a problem arises finding a fast and cost-effective solution is vital. Can the part be repaired? Does it need to be replaced? Is there inventory available? In our experience many operators find it especially difficult to source parts which have become obsolete or out of warranty. DEX Renewables worked with the company to develop a full test and repair solution for the entire rotor current controller system to enable the wind farm to resume full production.
Professional customer support
It seems logical that independent service providers (ISPs) with their wealth of repair expertise would be engaged by OEMs as has been happening in other industries such as the IT sector for decades. In this sector, the ISPs focus solely on their core expertize of service, and repair and so more often than not the customer experience remains positive.
However, there are currently poor links between OEMs and ISPs in the wind energy sector and so the required level of professional customer support has not yet happened. Although the ISPs have a wealth of experience and expertise, the lack of support and technical documentation can usually prevent ISPs from setting up a reliable and repeatable repair solution in the area of electronics.
So is there a solution to this dilemma? A second source repair solution for electronics and electrical parts must be developed by ISPs with capability to provide an on-time value proposition. As stated above this is not a straightforward task in the face of poor OEM support and lack of technical documentation. Therefore best in class electronics engineering techniques must be deployed to find repeatable and reliable solutions.
Often the most difficult part of the task is to ensure parts are exercised to their full design specifications. The majority of electronic control parts are custom made for the wind turbine environment. Therefore it is not practical or reliable to try and test these parts using standard off-the-shelf equipment.
In addition, it is not practical to use a wind turbine to exercise the parts. This has necessitated the development of complex software, tooling and test jigs from scratch in order to carry out full testing and validation procedures. To replicate an often highly intelligent series of electronic interfaces and inputs/outputs, signals are analyzed in great detail and software and hardware emulation techniques are used to design tooling equipment capable of ensuring full test coverage on all areas of functionality of the parts.
This was a method DEX Renewables applied to great effect with the Vestas rotor current controller parts. Six months of development work uncovered a surprising amount of functionality with these parts. Ultimately a combined system of software and hardware emulation was used to develop an effective test process.
Validation and verification of the system took another six months. We were able to apply a series of risk assessment and validation procedures adopted from over a decade of experience in the medical industry to ensure an effective process was in place from day one. We now employ these repair techniques on a daily basis for over 30 products used in wind turbines across Europe and recently North America. These products include controller systems; rotor current controllers; insulated gate bipolar transistor banks; power supplies; and human machine interfaces (HMI) systems.
Proper asset management
The wind turbine sector has also thrown up a number of other challenges when it comes to operation and maintenance issues. Parts are frequently stored in inappropriate environments — such as sheds or containers — close to the wind farm site, which means that when needed the parts are often in poor condition and need to be repaired or refurbished before they can be put into service. This can impact on operational efficiency.
As the offshore wind market expands minimizing failure of control systems and power electronics become paramount
It is therefore essential to have proper asset management systems in place to track where parts are and assess their current condition. Wind turbine parts are generally high value items and electronic components in particular are susceptible to humidity and static. In many cases parts will be hard to find and sometimes undocumented. When a part fails it is important to analyze the root cause of the failure so that recommendations can be made to the OEM on quality improvements.
If there are reliability issues with a turbine, further investigation can be required. This will involve site visits to analyze failure modes, review trigger files and error logs, interview site staff and monitor wind turbien generator functionality and application. Careful analysis of this data is used as the basis for recommendations for corrective action. In addition, monitoring equipment may be installed to help with analysis and performance.
As already mentioned, frequently documentation does not exist for parts requiring repair so it is assumed that the only option is to buy a new replacement. However, there is a high cost differential between repairing and renewal. Using highly specialised engineering skills it is possible to repair and refurbish such parts in the absence of technical documentation. There is also a strong environmental argument in reusing existing parts instead of scrapping them and buying new.
The repair process must be carefully managed to ensure the parts are repaired within appropriate time-scales and in a cost-effective way. This involves the use of detailed workflow and quality procedures so that each stage in the repair process is monitored and certified according to ISO standards. Where possible a swap-out process should be implemented so that when a part becomes defective it is immediately taken away for repair and replaced with a functional part so that a good stock of parts is always available.
In summary, by adopting a strategic approach to repairs, maintenance, parts procurement and logistics wind farm operators can reap the benefits of reduced downtime, lower costs and ultimately greater profitability.
Sean Keller is business unit director of DEX Renewables, a new division of DEX Europe that is focused on the European renewable energy sector, For more information visit www.dexrenewables.com.