Damages at the foundations of wind energy plants
A great risk: invisible, underestimated and with enormous consequences
Damages at the foundation of wind energy plants have become more and more acknowledged as a risk but remain largely invisible. They are still underestimated but have enormous consequences: high repair costs, recourse claims from operators, shutoffs, temporary blackouts or even complete loss of the plant. Mostly, the damages come creeping and are hidden as the foundations are covered after completion. The consequences of cracks or spallings are not recognized properly. The possible causes are discussed a lot but the question is if they are addressed at the right time, which means already during the construction phase.
Modern construction methods have reduced the weight of a wind energy plant about around 50%. Moreover, new designs and new sealing systems have been developed to reduce damages at the foundation. However, the biggest causes for damages are based on the insufficient supervision of the construction work and bad construction quality. The foundation is the main carrying element and extremely important when it comes to stability. The foundation is a relatively small part of the whole investment, anyway builders try to save money here and disregard the quality. Nevertheless, turbine producers, shareholders and operators should be able to rely on the safety of the foundation and on the long term usage of the wind energy plant already when construction begins. It has to be guaranteed for the investors that the foundation is absolutely free of damages and defects, so that the energy plant can operate for the calculated long term period.
In Germany requirements for the stability are governed by numerous norms and standards and monitored by an accredited testing center (ÜK II). Yet, the control is not always consistent and extensive enough. So far, there has not been any statistical analysis of foundation damages. According to experts, the estimated number of unreported cases is high.
Causes for damages based on too little preparation can be found in the details and the list of damages at foundations of wind energy plants is long. Some examples for sources of damages include: Inadequate drainage, improper implementation of existing norms and standards in the concrete mix used, missing needling in the concrete deliveries, lack of compaction and lack of concrete curing, use of defective material for lightning protection, improper installation of the soft layers respectively the inadequate coverage of the armoring or too early loading, when the tower structure is added to the construction.
Under the inspection of more than 500 foundation structures, experts from the BKS GmbH have found that the errors often occur in the practical implementation of project plans. Experience has shown that workers often have to deal with enormous time pressure on foundation construction sites, which is a possible cause for errors. Additionally there is a lack of professionals and of detailed knowledge of foundation construction and no complete documentation of the construction process is made. Moreover, communication is often bad and reduced sense of responsibility from all parts.
Due to the dynamic development in the wind energy sector, the solution of the problem is a matter of urgency and can be found in the consistent optimization of quality. For this purpose, the BKS has developed a complete and effective quality control concept. The terminal BKS evaluation is a real benefit for construction businesses and turbine manufacturers.