HBM Makes Case for Fiber Optical Foundation Monitoring Technology

With first subsidy-free offshore wind projects now on the horizon, the effect of cost reduction efforts becomes more ‘tangible’, as the industry is looking for further solutions that are cost-effective and more advantageous at the same time. HBM, a supplier of foundation monitoring systems including both resistive and fiber-optical strain gauges, has weighed the technical advantages and costs of both technologies, ultimately advocating the use of fiber-optical strain gauges on offshore wind foundations. 

Installing bare optical fibers for load monitoring (left). Optical gauges on wind turbine structure (right). Image source: HBM

“15-25% of the investment cost of offshore wind turbines lies in the foundations,” said Richard Sargeant, HBM’s Engineering Services Manager for North West Europe, referring to a report from the European Environment Agency on environmental and economic constraints in utilising Europe’s onshore and offshore wind energy potential.

“With falling prices there is a greater focus on reducing the cost of these foundations. Revisions of existing foundation designs to save costs means that design calculations need verifying with actual measurements, which can be an expensive exercise in itself,” Sargeant said. “HBM designs, supplies and commissions measurement systems for use in these foundations and now aims to help reduce cost by using optical technology in increasingly innovative ways.”

The company had put all the main aspects of using strain gauges on paper and produced a whitepaper discussing both upsides and downfalls of each of the two technologies. As a conclusion, HBM made a case for fiber-optical strain gauges, arguing that fiber-optical technology lends itself well to large structures with many measurement points and, in addition to the technical benefits, brings cost advantages as well.

Despite the fact that the use of fiber-optical technology is not new, there had been a relatively slow uptake in its utilisation for offshore wind turbine foundation monitoring, the company said.

In an industry requiring a design life of perhaps 25 years, with strain gauges often installed in a position unreachable after installation, there can be no room for experimentation, HBM stressed, further discussing the benefit of continued long-term accurate measurement when using fiber-optical technology.

According to the whitepaper, fiber-optical technology – when installed correctly – also provides a cost-effective solution for accurate foundation monitoring with lower installation cost at time of construction. Here, HBM considered installation of a fibre-optical strain gauge by a qualified engineer, which led to 15% lower cost of installation.