Periodic Reporting for period 1 - DESTINY (Moment-based nonlinear energy-maximising optimal control of wave energy systems to secure a renewable future)
Berichtszeitraum: 2021-06-01 bis 2023-05-31
Ocean waves have an enormous potential, capable of fulfilling 20% of the global energy demand, making a decisive contribution towards a low-carbon energy society, addressing number 7 (affordable and clean energy), 11 (sustainable cities and communities), and 13 (climate action) of the United Nation Development Goals. As a matter of fact, to achieve the 2030 Climate & Energy Framework and the Roadmap 2050 targets, the European Union (EU) highly encourages development of the ocean renewable energy field, which can potentially mitigate EU dependence on fossil fuels, directly contributing to Europe’s decarbonisation goals by 2030 and 2050. Despite being a vast resource, wave energy converters (WECs) have not yet been successfully commercialised. The lack of proliferation of wave energy can be attributed to its current levelised cost of energy (LCoE), which is currently substantially higher than other renewable energy sources.
Appropriate control system technology can impact WEC design and operation, by maximising energy extraction from waves, and optimising energy conversion in the system. In particular, the central problem in WEC control is to find a technically feasible way to ‘act’ on the device so that energy absorption from waves is maximised while minimising the risk of component damage. It is already clear that control technology can enhance WECs performance in a wide range of ocean conditions, substantially reducing the LCoE. In other words, the design of appropriate control technology, together with an economy of scale facilitated through array configurations, constitute key stepping-stones towards successful commercialisation of WEC technology.
In an effort to assist in the pathway towards making wave energy technology widely available, Destiny is a project dedicated to advance the state-of-the-art of WEC control technology by providing a novel and reliable nonlinear optimal control framework, maximising energy absorption for a wide range of ocean conditions for single and multiple devices, exhibiting real-time capabilities and globally optimal performance. In particular, Destiny focuses in a development of a reliable energy-maximising WEC controller based on the mathematical concept of a moment, which is essentially an object connected to the dynamical response of the system.
The major overall objectives of the project are to: (1) laid the foundations for a control framework capable of handling a wide class of WEC systems, which can be potentially highly complex and nonlinear; (2) assess and validate the performance of the control technique in realistic scenarios, to provide a tangible proof of reliability and energy absorption enhancement; (3) include WEC arrays (that is, multiple devices) within the framework, to fully assist in the pathway towards commercialisation; and (4) release an open-source software for smooth and straightforward implementation of the results of the project.
Appropriate control system technology can impact WEC design and operation, by maximising energy extraction from waves, and optimising energy conversion in the system. In particular, the central problem in WEC control is to find a technically feasible way to ‘act’ on the device so that energy absorption from waves is maximised while minimising the risk of component damage. It is already clear that control technology can enhance WECs performance in a wide range of ocean conditions, substantially reducing the LCoE. In other words, the design of appropriate control technology, together with an economy of scale facilitated through array configurations, constitute key stepping-stones towards successful commercialisation of WEC technology.
In an effort to assist in the pathway towards making wave energy technology widely available, Destiny is a project dedicated to advance the state-of-the-art of WEC control technology by providing a novel and reliable nonlinear optimal control framework, maximising energy absorption for a wide range of ocean conditions for single and multiple devices, exhibiting real-time capabilities and globally optimal performance. In particular, Destiny focuses in a development of a reliable energy-maximising WEC controller based on the mathematical concept of a moment, which is essentially an object connected to the dynamical response of the system.
The major overall objectives of the project are to: (1) laid the foundations for a control framework capable of handling a wide class of WEC systems, which can be potentially highly complex and nonlinear; (2) assess and validate the performance of the control technique in realistic scenarios, to provide a tangible proof of reliability and energy absorption enhancement; (3) include WEC arrays (that is, multiple devices) within the framework, to fully assist in the pathway towards commercialisation; and (4) release an open-source software for smooth and straightforward implementation of the results of the project.
The objective (1) has been achieved by incorporating relevant nonlinear effects into the controller calculations, while keeping real-time feasibility. This has been performed both by developing novel theoretical extensions to the underlying theory of moment-based control, and a suitable integration with data-based modelling and model reduction for nonlinear WEC systems. Furthermore, a composite control loop has been proposed alongside with the mathematical formulation, which features a two-level control architecture, suitable for practical implementation, and exhibiting enhanced robustness features. (2) has been achieved via exhaustive testing in experimental environments, using different wave energy conversion concepts, to fully showcase the capabilities of the strategy in real-life scenarios. In particular, both experimental hardware-in-the-loop (dry testing), and in-tank experiments (wet testing), have been performed, for pitching and heaving devices, including e.g. a flap-type WEC and a point absorber system, under realistic sea state conditions. Several control architectures have been tested, with convergence to a two-level controller based on moment-based optimal reference generation and robust variable structure tracking control. Furthermore, arrays of WEC devices have also been considered within experimental assessment and validation, in several layout configurations and with different number of devices, further demonstrating the reliability of the developed technique. (3) has been achieved via centralised and decentralised controller formulations, where the associated models, used for design and synthesis of moment-based control, have been obtained in a data-based fashion. Furthermore, and given the unmeasurable valuable for the WEC community behind availability of data for arrays of WEC systems, an open dataset has been released as part of the action, containing the experiments carried out as part of this campaign, in a post-processed and user-friendly fashion. Finally, (4) has been achieved by releasing an open-source Matlab-based software, termed CONTRALL. This particular software provides a user-friendly implementation of the validated moment-based controller, for any interested stakeholder, requiring minimum intervention from a coding perspective. In particular, any user can change the controller parameters and adapt these to a particular device, being a valuable ready-to-use implementation of the technology developed during Destiny, without the added trouble of coding the technique from scratch.
Overall, Destiny has provided the WEC community with a sophisticated optimal control technique, capable of accommodating a large class of devices with potentially very different dynamical behaviour, being validated in several experimental instances, including single and WEC array systems. Furthermore, thanks to the open-source software CONTRALL, any stakeholder can test and implement the technique straightforwardly, having the direct possibility of exploiting the project results and push towards efficient design and operation of WEC technology.