This project will validate in a real-world environment, an innovative direct drive Power Take-Off (PTO) for a tidal turbine that will move tidal energy a step closer to competing on a commercial basis with other renewable sources of energy generation. The PTO is the component that translates the mechanical power in the prime mover (the tidal turbine rotor) into electricity that is exported into an electricity network.
A project of this nature requires the involvement of organisations with a wide range of skills coming together and working closely in collaboration as a Consortium. The starting point for this project is a tidal turbine with a conventional drive train, as developed and demonstrated by Nova Innovation in partnership with SKF and Siemens; which has been deployed and operated in Nova’s grid-connected tidal site in The Shetland Isles, Scotland. In parallel, Nova has carried out research with the University of Edinburgh to develop a direct-drive PTO designed to replace the existing PTO and make a step-change improvement in the performance, reliability and survivability of the turbine.
Figure : Conventional PTO vs TiPA PTO
The focus of this project will be to replace the gearbox and conventional generator in the turbine with a PTO featuring a high-efficiency, low-maintenance direct drive generator.
Successful development of a direct-drive PTO will significantly increase the commercial viability of tidal turbines. Reducing the cost of operation and maintenance of tidal arrays will increase Return on Investment for turbine customers, allowing turbine technology development companies to sell more devices into an emerging global market.
AIM AND OBJECTIVES
The Consortium’s aim is to reduce the lifetime cost of tidal power by 20%, demonstrated by accelerated life testing of a next-generation tidal turbine PTO solution. The expected outcome of this project is successful validation of a world-leading, commercially viable PTO solution for a tidal turbine.
Project outputs will be independently verified, with the objective of achieving :
- Improved performance: Experimental validation of 20% Lifetime Cost of Energy improvement over conventional PTO;
- Improved reliability: Accelerated testing showing that PTO can extend service intervals from 2 years; and
- Verified survivability: Accelerated testing to demonstrate PTO lifetime of 20 years.
This project is being delivered using an integrated research and development approach that brings together world-leading partners with a wide range of expertise with the aim of developing an innovative PTO solution for the tidal energy sector.
The successful development of the proposed PTO system requires cutting-edge technical research into the reliability of electrical and mechanical components and materials in the hostile subsea environment. This will include:
- A review of literature and the development of models of reliability and performance to inform the prototype design stage;
- Combining PTO system models (mechanical, structural, thermal, fluid and materials) into an integrated turbine model that calculates the lifetime cost of electricity of a turbine incorporating the PTO system;
- Modelling including analytical techniques, Computational Fluid Dynamics (CFD) and Finite Element Methods (FEM); and
- Determining the techno-economic and social impacts of the technology developed in TiPA to underpin the commercialisation strategy and business plan for exploiting the PTO system.
The potential of the proposed PTO design will be explored by building a prototype PTO system.
Design validation testing:
The prototype PTO will be tested to confirm and validate that the performance, reliability and survivability targets meet the design specification. This will be conducted in a laboratory environment by RWTH Aachen University at their independent Chair for Wind Drives test facility in Aachen, Germany, and then in sea conditions by Nova Innovation at a site in Scotland.
Accelerated life testing:
Given the importance of reliability for commercial tidal energy it is vital to understand and to maximize the reliability and survivability of the PTO system. Traditional life data analysis involves analysing times-to-failure and aging data obtained under normal operating conditions. However, in the case of a system designed to operate for 20 years, such data can take years to collect. Accelerated life testing therefore allows designers to force systems to age and fail more quickly than they would under normal use conditions.
The prototype PTO will subjected to conditions (stress, strain, temperatures, voltage, vibration rate, pressure etc.) in excess of its normal service parameters in both a controlled laboratory environment and then in the sea – a real operational environment, in an effort to uncover faults and potential modes of failure in a short amount of time. From the analysis of the PTO’s response to such tests, predictions can be made about the service life and maintenance intervals of a product.
A key barrier to the development of commercial tidal energy is the confidence level of clients and investors, who need to know that the product will perform as specified. For this reason, independent verification of the PTO performance by Wood Group is at the core of this project.
The ultimate objective of TiPA is to develop a successful PTO product with significant benefits for the wider tidal energy industry. As such, the needs of relevant stakeholders need to be clearly understood and incorporated into the product design and performance.
The Work Breakdown Structure (WBS) defines the project activities into work packages to deliver the project. It is a breakdown which helps to easily plan, communicate and manage the work and processes involved to execute each work package of the project. The WBS has been used to develop the overall project schedule, as well as the resource requirements and cost budgets.
Figure : Diagram illustrating the project approach and the relationship between TiPA work packages.
A large number of deliverables will be produced throughout the 3 year duration of the project, and a proportion of those are to be accessible to the wider community to raise awareness on the challenges and progress of tidal energy technologies. These deliverables will be made available through this website in due course and at various conference events to maximise the benefit of TiPA to the ocean energy sector, and to raise investor and market confidence in the emerging tidal energy industry.