Community Research and Development Information Service - CORDIS


PowerKite Report Summary

Project ID: 654438

Periodic Reporting for period 1 - PowerKite (PowerKite - Power Take-Off System for a Subsea Tidal Kite)

Reporting period: 2016-01-01 to 2017-03-31

Summary of the context and overall objectives of the project

The PowerKite project is developing a power take-off system (PTO) for a novel tidal energy collector concept, the Deep Green subsea tidal kite. The overall objective of the PowerKite project is to enhance the structural and power performance of the PTO for a next generation tidal energy converter to ensure high survivability, reliability and performance, low environmental impact and competitive cost of energy in the (future) commercial phases.
The core innovation of the project resides in the electro-mechanical design of the PTO, including a design for the complete array layout and grid connection allowing the array to be deployed in sites with low velocity currents. The project will build scale models of selected components for the PTO system and integrate them in a scale model for open sea testing in Strangford Lough, Northern Ireland. Component development has been guided by modelling using component and system simulation models developed within the project.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the first phase, work concentrated on creating the project infrastructure, collecting data to establish a baseline, concept definitions, building component models and initiating component development. Simulation models for turbine and power electronics were also developed from start.
Tests with the ¼ scale kite provided data for input into the system analysis and optimization. A method for simulation of the full scale power plant performance based on ¼ scale was proposed.
Measurements of ambient noise from a high tidal flow environment and understanding noise propagation from the ¼ scale power plant have been carried out. Additionally, marine animal observations have begun as part of WP2. Data collected will be used for further development and validation.
Two new turbine designs were developed. By tailoring the optimisation to the specific conditions of a moving kite rather than a fixed turbine, two new turbine design reached increase in performance of around 20% as measured in model scale cavitation tunnel tests.
The PTO system design has been further developed by a thorough investigation and simulation work of potential converters, generators and cables. A new tether fairing, a bottom joint connector and a top joint connector have been designed and will be installed in ¼-scale at the test site in Strangford Lough.
Detailed models of generator and converters were developed and used to model the baseline system from which selected components were chosen for the improved system. Multilevel converters are proposed to achieve higher voltages and the advanced models are used to study the effect of system voltage on cost, dimension and performance. A dedicated emulator rig for component testing has been designed and is under construction.
Hydrodynamic characteristics i.e. force and moment coefficients of the PowerKite and tether have been computed for the envelope of conditions experienced during energy production. These characteristics are key to kite flight control and simulation.
An unsteady analysis method has been developed and used to compute forces and moments experienced by the kite during energy production. This more complex method was shown not to add value compared to the quasi-steady approach within the accuracy of the methods. This confirms the quasi-steady approach as an appropriate method for determination of hydrodynamic characteristics during energy production.
A base case for the complete array layout and grid connection was developed. Standard calculations of key parameters as reactive power, voltage levels, earth fault currents were used to check the design and chose components.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Tidal and ocean current energy offers safe, reliable and locally produced renewable energy not subject to geopolitical risks. The Powerkite project aims at reducing the time to market for a step-change tidal and ocean current energy converter which is suitable for installation sites with low velocity currents, where no other technologies are known to be efficient. Deep Green’s unique characteristics make it possible to reach twice as much of Europe’s sites compared to other tidal energy converters, thereby contributing to solving the global climate and energy challenges and improving EU energy security
The project pushes technologies in several areas beyond state of the art. Development; off shore and laboratory testing, simulations and modelling will build world leading knowledge that strengthens the European renewable industry. Manufacturing of components and power plants, installation and maintenance will create a number of new jobs, both local (close to the site of exploitation) and also in production and R&D throughout the supply chain.
The main focus in the Powerkite project has been the PTO (Power Take Off) system and one of the most important results so far from the project is the substantial increase in power output that has been achieved with new turbine designs developed. This together with the development of power electronics and electrical system topologies that minimizes losses in the complete array design will contribute to higher power output in future implementations. Having a high energy conversion and a high efficiency in the PTO system together with a reliable system increases substantially the probability for a successful market introduction.
The environmental interaction studies, i.e. noise measurements, marine monitoring and collision risk modelling is already building important understanding that can be used by the tidal industry and regulatory bodies, notably to facilitate site permit processes. The development of both specific and generic models and simulation methods are of great value for the Deep Green technology development, but can also contribute to many different sectors. The consortium is using a renowned certification body as a sub-contractor, in order to contribute to the development of pre-standards for the next generation of tidal energy converters.
The project specifically targets the challenges of high reliability and long lifetime in marine energy. The development of a more reliable and optimised PTO will reduce the number of planned and unplanned maintenance operations required per device, thus reducing the cost. Service and maintenance costs are studied and a generic simulation model based on weather and site conditions is under development.
Produced electricity needs to be transferred to the grid, i.e. the power plants in an array need to be grid connected and therefore grid compliance is an important area of work within the Powerkite project. A first array structure set-up has been proposed and the grid compliance requirements have been addressed. Notably, as a result of the development in Powerkite the earthing strategy has been revised for the Deep Green technology
The perceived high cost of energy is a major barrier to the adoption of marine energy technologies, especially in the current economic climate. For these targets to be achieved technologies will have to be adopted soon, and the lower the financial risk, the more likely this is to happen. Recent evolution in off shore wind and solar technologies with significant cost reductions puts even more pressure on tidal energy to be competitive. The Cost of Energy (CoE) model that Minesto has is under revision with input from the Powerkite project, such as performance improvements and decreased losses within the system.

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