Tidal power refers to extracting electrical energies out of the tide streams in oceans. Various techniques exist. Tocardo is a provider of axial turbines, and our guest, Pieter de Haas, is their CTO. In this episode we talk about tidal power in general, siting, the design and engineering of Tocardo’s turbines as well as the overall economic and technical trade-offs in making the turbines work over the long run.
Tidal stream generators
Horizontal axis turbine | Francis turbine | Vertical axis turbine | Far field effect | Mass spring effect | Wake | Power = force x velocity | Turbine | Rotor | PTO (power take-off) | Generator | Housing/Nacelle
Tide | Tide prediction | Tidal currents | Ebb and flood | Ebb and flow | Lunar cycle | Spring and neap tides | Electrical grid | Weather effects | Direct drive | Permanent magnet generator | Frequency converter | Hydraulic Brake | Semi-submersible | Orbital wave motion | Feed-in tariff | Ocean current | Off-the-grid | Distributed generation
Sea creatures avoid strong currents | Tip speed 20m/s vs 80m/s in wind turbines | Increase speed for efficiency when currents deter creatures | Fixed pitch turbine for reliability instead of variable pitch | Speed is measured by frequency converters | Speed is controlled by frequency converters by varying amount of energy harvested (Balance efficiency vs reliability – aim for reliability and minimise risk) | Numerical modelling | Model for energy output, reliability & engineering cost | Over-engineer | 60 tones thrust load | 150 tonne-meter torque | Economic engineering | Emerging technology | Rare-earth magnet | Superconductivity | Cost of energy increasing | Future turbine cost reduction expected | Extreme fatigue | Material curve | Currently 35% efficient | Efficiency currently acceptable | Bi-blade patent | Blade direction is flipped by reverse-powering the generator as a motor
10 turbines currently running & connected to the grid | Turbines running up to 8 years so far | All running in the Netherlands | Type T1 6m blade diameter 110kw | Type T2 10m blade diameter 235kw | Mission is to manufacture and service turbines | 25 employees