Industrial Manufacture of Marinised Coils – IMMCoil
The marine energy environment poses substantial challenges that must be addressed if marine renewable energy technology is to proliferate. Key among these issues is the development of an efficient, adaptable electrical power take-off (PTO) system capable of coping with the highly variable forces. Furthermore, with high operation and maintenance (O&M) costs seriously affecting the competiveness of many systems, PTO’s must aim for designs with greater reliability and operational flexibility to lower associated downtimes. Developing integrated modular electrical generator topology and power electronic systems has the potential to improve system reliability and reducing repair time should faults occur. The modularity allows the system to continue operation at reduced capacity should either a fault occur or if sections are required to be removed for maintenance. Additionally, a fully flooded generator provides for a more versatile WEC design enabling a greater degree of integration compared to coupling a device to a mechanically sealed generator.
The UoE demonstrated a fully flooded machine with coils moulded into epoxy for protection, and polymer surface contact bearings were used instead of conventional bearings. The fully flooded coils showed excellent thermal performance with the winding temperature never exceeding 25°C. However, a number of faults occurred due to water ingress, which were related to the manufacturing process. A variety of protective materials are available for use within the marine environment; however, the challenge and novelty of this project comes from the manufacturing process and the operational constraints of the material once combined with an electrically active coil. Such challenges in manufacture come from volume of copper within the mould acting as a heat sink, altering the ability of the material to bond or cure uniformly throughout the blade. Fluctuating machine operational characteristics, such as those found in wave energy extraction, result in thermal cycling of windings, pulsating vibrations, variable load profiles acting on the stator assembly. The reciprocal nature of the motion in a wave device results in variable voltage and frequency waveforms at the output, with high dV/dt states across the windings from the power converter. The composite blade must be able to survive these electrical and mechanical stresses whilst maintaining protection, structural stability and efficient operation. By engaging research with industrial development and feeding real world applications and manufacturing practicalities back into product development, the UoE research team hope that the FEMM Grand Challenge 1 and 2 targets are realised.
The IMMCoil feasibility study will assess the effectiveness of various protective potting or impregnation methods for the production of stator blades for use in a fully flooded marine environment. The methods will be assessed for their industrial production merit, while confirming their ability to be integrated with electrical systems, maintain the required structural integrity, heat dissipation levels and material integrity during operation in wet and fully submerged conditions. By investigating the design and material selection of potted stator modules, we will deepen the manufacturing knowledge of the engineering team, and our manufacturing partners at QuartzElec.