How lifetime analysis can make wave power more reliable
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Ocean Harvesting Technology
Generated/enhanced by AI
Wave energy systems need to operate year after year in a marine environment where loads are constantly changing. In the European research project INFINITY, RISE is developing methods to understand how critical components are affected over time. This knowledge can contribute to longer lifetimes, smarter maintenance and lower costs.
– Wave energy systems operate in a highly demanding marine environment. They need to withstand the most severe storms while remaining reliable during long periods of normal operation, says Pär Johannesson, Senior Researcher at RISE specialising in mechanical reliability, fatigue and load analysis, and one of the researchers in INFINITY.
How long components last is not only a technical issue. Maintenance and servicing account for a significant share of the cost of wave energy, particularly because the systems operate offshore. INFINITY therefore has a strong focus on both reliability and maintenance. The project aims to develop methods that can extend service intervals, increase availability and reduce operation and maintenance costs. It is also working with circular design and ways of extending component lifetimes.
For RISE, this work is also part of a broader research field. Lifetime analysis, fatigue and statistical methods are used to assess the reliability of critical components in areas such as renewable energy, vehicles and other industrial applications.
– The goal is to be able to consider performance, lifetime and reliability together from the very beginning of system development. The better we understand how components are loaded and how they age, the better our chances of designing them correctly from the outset and avoiding unnecessary costs later on, says Pär Johannesson.
Loads are constantly changing
Unlike many other technical systems, a wave energy system operates under conditions that are constantly changing. In severe weather, components can be exposed to extreme loads. During normal operation, they are instead subjected to repeated and varying loads that can affect their lifetime over time.
An important part of RISE’s work is therefore to understand how loads accumulate over time and what this means for critical parts of the system. One INFINITY report examines the ball screws used in the power take-off system of InfinityWEC, the wave energy technology being developed by project partner Ocean Harvesting Technologies. The ball screws help convert the motion of the waves into electricity and are subjected to varying loads during operation.
RISE and Ocean Harvesting Technologies have jointly developed a model describing how these loads affect the components over time. The model is based on established ISO standards and has been adapted to the conditions within INFINITY. Using information on factors such as force and motion, it is possible to analyse how the components are affected during operation.
– The challenge is to capture the mechanisms that actually affect lifetime without making the model so complicated that it becomes difficult to use in practice. That is the balance we need to find, says Pär Johannesson.
From modelling to smarter control
Lifetime analysis is not only intended to provide knowledge about how long a component can be expected to last. The next step is to use that knowledge as the technology is tested and further developed. Within INFINITY, models and technologies will be verified in controlled test environments. The project is also working with condition monitoring and predictive maintenance, where information from the system can be used to plan interventions before problems occur.
In the longer term, this information could also influence how the wave energy system is controlled. If a component is exposed to particularly high loads, for example, the control strategy could be adapted to reduce wear while still taking energy production into account.
– If we can monitor how components are affected during operation, we also have better opportunities to make decisions about how the system should be operated and when maintenance is needed. This allows us to start balancing energy production against loads and lifetime in a more informed way, says Pär Johannesson.
INFINITY is a three-year European research project coordinated by RISE and carried out together with Ocean Harvesting Technologies in Sweden, NILU in Norway, VGA and Politecnico di Torino in Italy, and Maynooth University in Ireland. The project is funded through the Clean Energy Transition Partnership, CETPartnership, the European Commission and national funding organisations.
The aim is to develop the next generation of wave energy technology through a new power take-off system, known as a PTO system, combined with advanced control. The technology is intended to become more reliable and efficient while reducing operation and maintenance costs. RISE is leading, among other areas, the work on lifetime analysis and mechanical reliability.
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