The UK tidal stream resource could meet up to 11% of national energy demand. Realising this potential depends on rotor blades that are both structurally reliable and cost-effective to design. Tidal stream technology has progressed through key deployments such as Orbital Marine Power's O2 and the MeyGen array, the world's largest operational tidal array at 6 MW, which has demonstrated grid reliability over six years.

Existing design tools are inherited from wind turbine blade structural design, developed for long, slender structures in air. Wind rotors can exceed 0.25 km in diameter, where self-weight becomes a governing structural concern; tidal rotors, such as Orbital's 20 m diameter O2, operate in an entirely different structural regime.

Tidal blades are shorter and stockier. Operating in water which is 800 times denser than air, hydrodynamic loading is concentrated at far higher intensity over a much shorter span. This makes structural depth and stiffness the critical design drivers, rather than self-weight. Preliminary structural design for tidal blades currently lacks an integrated framework that couples tidal-specific critical design drivers with fatigue assessment at the material level.

This work presents two connected design tools. The first rapidly identifies structurally viable blade layouts under strength and stiffness requirements. The second estimates how fatigue damage accumulates in blade materials over time. The methodologies being developed are informed by hands-on experience from tidal blade design, manufacturing, and testing at FASTBLADE and within the MAXBlade project.

These tools are being developed as part of the CoTide tidal energy programme. They provide a preliminary design pathway that couples early-stage structural design with fatigue-informed lifetime predictions, initialising detailed design for more reliable and cost-effective blade deployment.