Direct Generation
This competition is investigating conceptual approaches to integrate and apply Direct Generation technologies as part of wave energy converter systems.
Lead contractor
Wave Energy Scotland Ltd
Overview
Emerging from WES’ ‘Alternative Generation’ investigations, ‘Direct Generation’ is the application of novel electrostatic generation technologies, which use the flexible properties of elastomers and polymers to drive variable capacitance, a characteristic that can directly transform movement (stretching, twisting, bending) of a material, into electrical energy. This results in promising benefits when applied in wave energy:
- Enables a new class of flexible architectures, without reliance on high-cost steel structures
- Simplified power conversation process relative to conventional wave energy architectures
- Adaptable, tuneable and survivable in varying wave energy resources
- Power conversion distributed generation throughout the wave device
- Maximum percentage of the WEC’s mass and cost directly involved in energy generation
- Architectures using cell-based/segmented, modular direct generation subsystems, rather than monolithic direct generation solutions
- Potential for applying mass-manufacture processes
A direct generation solution could replace numerous cost-centres of conventional wave energy architectures, resulting in significant cost reductions. Simply replacing the power conversion subsystem within a conventional wave device structure is a valuable test platform but would miss the transformative opportunity of Direct Generation. The same technologies (or adaptations of) have broad application in other sectors, e.g. as actuators in soft robotics and medical processes, as active motion/vibration control and acoustics devices, as variable stiffness suspension and tyre solutions in automotive. While the applications vary widely, fundamental R&D requirements are common.
Types of Direct Generation Technology
After supporting relevant projects in the WES PTO and Control Systems programmes, an investigative Landscaping Study, a co-funded PhD and a range of cross-sector collaborations, WES has down-selected two direct generation technologies: Dielectric Elastomer Generators (DEGs)and Dielectric Fluid Generators (DFGs).
Dielectric Elastomer Generators - DEGs use dielectric elastomers between flexible electrodes to generate electricity when wave motion or pressure changes stretch and relax the materials. The control system applies electrical charge when the device is stretched (low capacitance) and discharges it at a higher voltage when relaxed (high capacitance) – each strain cycle yields a net gain in electrical energy.
Dielectric Fluid Generators – DFGs use a similar operating principle to DEGs, with the function of the dielectric layer between the electrodes performed by a fluid instead of an elastomer. This could bring significant benefits such as a reduced requirement for high strain in flexible materials and an ability to recover from dielectric breakdown through recirculation of fluid.
Direct Generation programme
Now, WES is delivering a strategy to continue supporting development of direct generation wave technology, through a mix of innovation funding, collaborative R&D activity, cross-sector collaboration and sector coordination.
- The Direct Generation Concept Design Competition programme: to create vision, illustrate and quantify benefits and guide enabling R&D
- Supergen ORE Impact Hub Flexible Fund projects: delivering enabling R&D to improve knowledge and maturity of Direct Generation technologies
- A growing network of collaborative R&D projects Direct Generation guidance WES has developed two documents to guide R&D activities and evaluation of these technologies.
Alternative Generation
Electricity generation from waves typically involves highly complex systems. Alternative generation methods with novel materials could simplify wave energy converters. Wave Energy Scotland is keen to facilitate cross-sector collaboration to drive this forward.
There is an opportunity with alternative generation techniques to realise step-changes in cost and performance that could continue development beyond the current attractive crop of pre-commercial technologies and hasten wave energy’s path to cost competitiveness and subsequent widespread deployment, or application in emerging niche markets. There are challenges that need to be addressed with these technologies, and at this early stage of development this will require a collaborative effort involving materials research, development of cost-effective power electronics, systems integration and wave energy expertise.
In wave energy considerable progress has been made and continues to be made in the development of cost-effective power take off systems (PTOs) which utilise permanent magnets. However, these subsystems have many moving parts and require regular maintenance meaning that they can be highly complex and costly. Alternatives such as Dielectric Elastomer Generators (DEGs) and Triboelectric Nanogenerators (TENGs) provide the potential to reduce the mass, volume and cost associated with a traditional PTO. These solutions can eliminate the need for a separate PTO with the power conversion function being integrated into the WEC structure; or incorporated into existing WECs.
The full technical paper is available to access on the right. For further information on this subject, please contact Jonathan Hodges at Wave Energy Scotland.
Direct Generation Research Agenda
WES has built a research agenda including a list of enabling R&D activities that need to be fulfilled to bring DG closer to exploitation. The Research Agenda document outlines the different areas of R&D requirements ranging from material selection, module design, manufacturability and integration into the WEC. This document will be updated in correspondence to the latest R&D needs identified from WES’ supporting activities. It should be used as a guidance tool for both academic and industry experts for supporting R&D activities.
Evaluation and Guidance
In correspondence with the need to quantify and evaluate emerging technologies to understand their competitiveness, WES has developed a series of quantification criteria based on other frameworks such as IEA-OES and TPL, but tailored to the low-TRL needs of Direct Generation. The evaluation and guidance document outlines several quantification criteria including power density, cost of energy, longevity, practicalities and sustainability. This document will be updated to reflect the state-of-the-art Direct Generation technologies.
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