Edinburgh Research Explorer

Techno-economic assessment of submerged wave energy converter based on Dielectric Elastomer Generators (DEGs)

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Abstract

The Power Take-Off (PTO) unit has usually been identified as one of the most critical components in Wave Energy Converters (WECs). Several studies carried out in the last years have found there is significant room for improvement in that field. Most wave energy devices have traditionally employed a hydraulic system to convert WEC motions into electricity, generally via rotating generators. Alternatives such as pneumatic systems and electrical machines have also been used in a multiplicity of concepts. However, the aforementioned technologies might be costly, unsuitable for the ocean environment and do not adapt efficiently to the low-frequency regimes of waves.
These circumstances have motivated an increasing interest in disruptive innovative and less conventional materials and solutions, such as Dielectric Elastomers (DEs), which are based on soft polymeric materials. DEs are rubber-like materials that can be combined to construct high voltage direct current generators (DE Generators, DEGs). To present date, the employment of DEs has fundamentally focused in low-power small-scale uses, such as actuators or sensors in automotive or biomedical applications. However, the fact that DEGs are highly-deformable electrostatic solid-state capacitors able to convert the mechanical energy absorbed when being deformed into stored electrostatic energy has positioned them as a possible breakthrough technology for wave energy conversion into electricity. Deformation energy stored in a DEG during a wave cycle can be withdrawn from its capacitor and any time during and after the conversion phase, which offers a great potential in harvesting energy from the ocean.
As a consequence, new WEC concepts, merging the primary mover and the PTO sub-components, can be envisioned. A novel body (usually in the form a membrane) is hence responsible for capturing the wave energy but also transforming it into electricity. Compared to other PTOs typically used in WECs, DEGs offer better maintainability (there are no moving parts but the membrane itself), increased resistance against corrosion, potential cheaper costs (because of the lower raw material price), easier manufacturability and handling, and feature a conversion energy density and efficiency which is almost independent of load cycle frequency and amplitude.
Nevertheless, techno-economic studies on the application of DEGs in WECs are needed for a better understanding of their potential commercial viability. The present study examines the techno-economics of a DEG-based WEC, with the aim of analysing the credibility of a path towards commercial Levelised Cost of Energy (LCOE) values in the foreseeable future.
This Techno-Economic Assessment (TEA) investigates the performance of a DEG-based WEC, as well as establishes and quantifies the improvements in LCOE achieved thanks to this innovative solution. The analysis also includes the study if the impact of different sub-systems and parameters in the cost of energy given by the WEC concept, identifying room for future improvements. Alternative metrics, often used in evaluating low Technology Readiness Level (TRL) devices, are also considered, such as Capture Width Ratio (CWR), and energy per unit mass and area. Finally, recommendations about suitable scaling of the DEG-based WEC (i.e. device power rating) are also provided.

ID: 93797416