Tidal Energy Calculator

The calculator uses the kinetic energy formula: P = 0.5 × η × ρ × A × v³, where η is turbine efficiency, ρ is water density, A is the rotor swept area (π × r²), and v is tidal flow velocity. This is the standard formula for tidal stream turbines, analogous to wind turbine calculations but using water instead of air.

Tidal energy harnesses the kinetic and potential energy of ocean tides caused by the gravitational pull of the Moon and Sun. Tidal stream turbines work like underwater wind turbines — spinning rotor blades capture kinetic energy from moving water currents and convert it to electricity via a generator. The predictable, twice-daily tidal cycle makes it one of the most reliable renewable energy sources.

Most commercially viable tidal sites require a minimum mean spring peak velocity of around 2–2.5 m/s. Because power scales with the cube of velocity, sites with 3–4 m/s currents produce significantly more energy — a doubling of velocity produces 8× the power. World-class sites like the Pentland Firth (Scotland) and Bay of Fundy (Canada) regularly exceed 3 m/s.

The theoretical maximum efficiency for any turbine extracting kinetic energy from a fluid is ~59.3%, known as the Betz limit. In practice, real tidal turbines achieve 35–45% overall efficiency when accounting for mechanical, electrical, and hydrodynamic losses. This calculator allows up to 59% to reflect the Betz limit ceiling.

Capacity factor is the ratio of actual energy produced over a year to what the turbine would produce if running at full rated power continuously. Tidal turbines typically achieve 25–40% capacity factors because tides vary in speed throughout each tidal cycle. Knowing the capacity factor is essential for estimating realistic annual energy yield and project economics.

The best tidal energy sites feature naturally accelerated tidal flows, typically in channels, straits, and headlands. Top global sites include the Pentland Firth (UK), Bay of Fundy (Canada), Alderney Race (Channel Islands), and various sites around South Korea and Australia. These locations combine high current speeds with manageable seabed conditions for turbine installation.

Tidal energy is highly predictable — tidal cycles can be forecast centuries in advance — unlike wind or solar which are weather-dependent. Water is ~800 times denser than air, so tidal turbines produce substantial power from smaller swept areas at lower velocities. The main drawbacks are higher installation costs and limited suitable sites compared to wind and solar.

Water density (ρ) appears directly in the power formula, so it linearly affects output. Seawater averages 1025 kg/m³, while colder or saltier water can reach up to ~1030 kg/m³. Freshwater is ~1000 kg/m³. Using the correct density for your site ensures an accurate power estimate — the difference between fresh and salt water represents about a 2.5% variation in power output.