When considering investments into offshore renewable projects, the perception of technical risk is dependent on how confident investors are that device will perform reliably and produce the expected output. In order to achieve this reliability, it is important not only to predict the lifespan of a product, but also to investigate and consider the sources of variability and their influence on lifespan prediction.
As the wave and tidal technologies are approaching a pre-commercial stage, in-sea testing and demonstration on various scales will be a primary focus for the sector over the next three to five years. Currently, the guidance on how to deal with reliability in marine devices is still provided at a generic and therefore insufficient level. This places a demand on test houses to implement rigorous validation programmes such that the reliability of emerging technologies can be robustly and independently verified before they move onto large scale array deployments.
The Reliability in a Sea of Risk (RiaSoR) project, funded by the H2020 OCEANERA-NET programme, was created to address the strategic need for the wave and tidal sector to learn lessons surrounding the key engineering challenges that underpin reliability issues.
The ORE Catapult project team, with strong turbine power converter knowledge to hand, adapted, evaluated and demonstrated the value of utilising a reliability methodology called Variation Mode and Effect Analysis (VMEA) for the wave and tidal sector.
VMEA is a methodology that is well suited to the later design phase of turbine technology to predict the life of the product and determine robust safety factors or tolerances. In RiaSoR, a prediction model (CLAST tool) was used incorporating random variation as well as statistical and model uncertainties. The random variation, i.e. scatter sources, cannot be avoided, and were handled by applying safety factors. Statistical and model uncertainties were decreased by gaining more data or by building better models. The CLAST tool is useful in the turbine design process because it can be used to quantify the most important sources of uncertainty in systems/sub-systems/components and the magnitude of these uncertainties. The predicted uncertainty can then be used to calculate a reliability index which calculates the distance/time before failure.
The use of the VMEA methodology (and tools like CLAST) is helping to establish industry best practices in reliability validation for wave and tidal devices through:
This project has established a framework for reliability assessment within the ocean energy sector, identifying critical components and parameters that influence uncertainties and safety factors. This helps ocean energy developers to achieve optimal reliability while minimizing cost and time to market in the development phase. In the production phase, it will also contribute to a lower operational expenditure and increased performance. The expected impacts are a significant contribution to the Levelised Cost of Energy reduction of ocean energy to make the technology both a technical and economically viable solution for a future low carbon energy system.
ORE Catapult successfully developed and presented the CLAST tool along with a range of reliability testing methodologies developed and demonstrated by the RiaSoR consortium at an invitation only workshop that was attended by key industry stakeholders and academic experts in the field of wave and tidal energy.
Industry interest in RiaSoR has led to a follow-on project, RiaSoR 2, with the ultimate aim to establish industry best practice in reliability validation for wave and tidal devices through reliability guideline development and the provision of training on newly established methodologies.