Investigation of a Spiral Planar Coil on Coreless Axial Flux PM Generator for Pico-Hydro Applications

The axial flux permanent magnet (AFPM) topology provides interesting advantages for Pico hydroelectric energy generators. AFPM Pico hydroelectric generators can be deployed in low head and low flow waterways at low cost with low supporting infrastructure and minimal impact to climate and the waterway ecosystem. Coreless designs with high power and torque density may be achieved with new coil and magnet topologies which are simpler to fabricate using additive manufacturing technologies. Here we present a novel planar coil design utilizing dual reverse spiral with overlapping and non-overlapping coil layouts which may be surface printed on a graphite sheet substrate and NdFeB N54 trapezoidal permanent magnets. We validated the design with finite-element simulations and evaluated the power and electrical generation properties, magnetic flux distribution of the coils and thermal distribution. Overlapping spiral planar coils is superior and achieved a simulated performance of 92W at 230V and 1.30A peak generated voltage and current at 500rpm and demonstrated no significant thermal hotspots but exhibits a chirped sinusoidal current at initiation. We demonstrate here the feasibility of using spiral planar coils for Pico hydroelectric generators and anticipate further performance gains from improvements in the spiral coil geometry and magnet arrangement in future work.