Excellence
Europe Towards The Development Of Ocean Energy
Developing a significant contribution to the market
Europe’s 2050 Energy Strategy has established a target to reduce greenhouse gas emissions by 80%-95% compared to 1990 levels and renewable energy accounting for at least 64% and up to 97% of the electricity consumed.
The European wave energy industry is a world leader with a first mover advantage and is a job creating industry in an innovative sector with high skills requirement. The European Union is at the forefront of technology development, with about 60 % of wave energy developers being located in the EU. The majority of ocean energy infrastructure, such as ocean energy test centres, is also hosted in the European Union. The supply chain is spread across Europe, and the creation of ocean energy market is expected to have a positive effect on many European regions.
This ocean energy industry is and will be based on the use of the so-called Wave Energy Converters (WECs) which produce electricity from the wave energy. The heart of a WEC is the Power Take-Off (PTO), which transforms a mechanical movement into electrical energy in one or several steps. Those PTOs transforming in a single step are called Direct Drives and have shown to be a reliable, robust, efficient and cost affordable solution, although they require to produce very big forces working at relatively high speeds. Increasing their Force to Mass Ratio Capacity (Force Density) becomes a primarily objective for the ocean energy industry.
The overall objective of the SEA-TITAN project is to make a step change in the wave energy sector by designing, building, testing and validating an innovative second generation Direct Drive Linear Electric Generator Power Take-Off solution
A high peak force for short intervals is critical to the overall PTO functions and in particular to end-stop control, whilst higher overall force density is essential to allow WECs to take advantage of advanced control strategies and to maximize energy capture from large sea-states in a wider range of wave periods. Nevertheless high force values with poor efficiencies are useless, since most of the extra captured energy would be lost in the PTO.
This solution will also contribute to reduce significantly the Levelized Cost-of-Energy (LCOE) of any WEC based on the proposed PTO system. Also Capital Expenditure (CapEx) can be reduced, at the time the overall system efficiency (Float-to-Wire Efficiency (FtWE)) can be augmented. The term FtWE is defined as the ratio between the mechanical energy absorbed by the WEC and the electricity fed into the grid.
Making a step change in the wave energy sector.
Develop
A second generation of direct drive electrical PTOs: an Azimuthal Multitranslator Linear Switched Reluctance Machine.
Include
In this development two basic features which are closely related: Modularity and Crosscutting, to allow an easy adaptation to different WEC technologies.
Explore
The possibilities for developing a third generation of superconducting linear generators aimed at increasing the Integrated Power Capture Ratio
Advance
In business models based on “open hardware models” (new concept to be developed and implemented within SEA-TITAN project).
The Concept
The technical concept underpinning SEA-TITAN proposal comprises the development of a disruptive linear electric direct drive power take-off (PTO) for wave energy converters (WEC). The innovative type of PTO proposed is an Azimuthal Multitranslator Switched Reluctance Machine (AMSRM) that will be complemented by the appropriate power electronic converters and control platform to develop the power transformation from the mechanical power in the WEC to the electric power supplied into the grid.
This invention is both novel and inventive, achieving three substantial improvements compared to current tubular generators and non-direct drive systems: a) concentrated and static coils and simpler translator made just of magnetic laminations that means a robust and cost effective solution, b) higher density force without the use of permanent magnets, by using a multitranslator topology, c) higher power density that means a compact PTO able to fit in the geometry of most wave energy converters.
These improvements will contribute to increased energy production, reduced system mass, increased reliability and increased availability. Together these innovations will reduce significantly the Levelized Cost-of-Energy (LCOE) delivered by the SEA-TITAN crosscutting PTO system.
SEA-TITAN is created to accelerate the advent of wave energy by opening the innovation process to the open source community by means of the implementation of an open business, which facilitates the technology development, providing free use of patents by other competitors (Wave Energy Technology Developers), the ones who are in the Consortium or additional companies willing to join in the future.
State of the Art and Progress Estimated
State of art
Present Direct Drive PTOs are limited in vertical displacement velocity. Since the Power that a PTO is able to produce is the product of its force times its velocity, limitations in the velocity will reflect in the extracted power.
How do we meet the objective
A new machine is proposed to overcome the previous limitations based on two concepts: Multi-translator topology (already developed by the proponents) and azimuthal magnetic configuration to optimize adaptation to the WEC geometry. The resulting machine is named Azimuthal Multi-translator Switched Reluctance Machine (AMSRM).
Alternatively a long term solution based on superconducting technology will be analyzed, although is not the core activity of the project.
State of art
Non Direct Drive PTOs are based on mechanical, hydraulic or pneumatic solutions, with a limited efficiency and high maintenance requirements, while some Direct Drive PTOs use expensive materials such as rare earth permanent magnets. The high cost of these materials has an especial impact on the LCOE when considering long stroke PTOs, which is currently the tendency in order to increase the power by augmenting the speed with a limited force.
How do we meet the objective
The solution proposed in SEA-TITAN requires no failure-prone gearing or expensive material such as rare earth magnets. It is based on the very well-known concept of magnetic reluctance, which is especially appropriate for the application of a linear electric machine with a long translator, as it is the case of interest for wave energy generation.Alternatively a long term solution based on superconducting technology will be analyzed, although is not the core activity of the project.
State of art
Present technologies used in direct-drive PTOs achieve a Stator Force Density limited to around 20 N/kg. This includes the present Rectangular Multi-translator Switched Reluctance Machine (RMSRM) developed by WEDGE with a Stator Force Density of 17.5 N/Kg
How do we meet the objective
This proposal is aimed at doubling the force density value of the present RMSRM from 17.5 N/kg to a minimum of 30 N/kg, which will have a significant impact in the energy capture increase, also doubling the value of the Integrated Power Capture Ratio (IPCR). The path of a superconducting PTO will be explored to further increasing the Force Density and the Efficiency
State of art
Present Direct Drive PTOs are limited in vertical displacement velocity. Since the Power that a PTO is able to produce is the product of its force times its velocity, limitations in the velocity will reflect in the extracted power.
How do we meet the objective
This proposal also aims at developing a PTO with capability of achieving speeds up to 3ms-1. The possibility to achieve such velocities is especially positive when the WEC is designed to work close to Float resonance, operating the system with resonant (or reactive) control strategy, where the maximum electric power is obtained from the waves.