Tidal Energy Potential Calculator

Tidal energy flux is calculated using P = ½ × ρ × A × v³, where ρ is seawater density (~1,025 kg/m³), A is the turbine swept area or channel cross-section, and v is tidal current velocity. The cubic relationship means that a 1 knot (0.51 m/s) difference in peak current translates to a ~50% difference in power. Prime tidal sites require: (1) Peak spring tide currents >2.5 m/s (~5 knots) — slower currents are uneconomic. (2) Channel constriction (headlands, narrow straits) that accelerates flow — the Pentland Firth (Scotland) reaches 5.5 m/s. (3) Water depth 25-50m for turbine installation. (4) Proximity to grid infrastructure. (5) Minimal environmental impact on marine ecosystems. Unlike wind and solar, tidal energy is predictable decades in advance — the tides follow astronomically determined cycles. A site with 3 m/s peak neap and 4.5 m/s peak spring produces ~3.4× more power during spring tides (since P ∝ v³). Annual energy can be estimated from the tidal velocity duration curve, which typically follows a Rayleigh or Weibull distribution.

Two fundamentally different approaches: (1) Tidal Range (barrages/lagoons) — uses the potential energy of the height difference between high and low tide. P = ½ × ρ × g × A × h², where A is basin area and h is tidal range. Key sites need >5m tidal range (Brittany, France: 13.5m; Bay of Fundy, Canada: 16m; Bristol Channel, UK: 15m). La Rance (France, 240MW) has operated since 1966. Environmental impact: significant — alters sediment transport, fish migration, and intertidal ecosystems. (2) Tidal Stream (turbines) — uses kinetic energy of moving water, similar to wind turbines underwater. P = ½ × ρ × A × v³ × Cp. Environmental impact: much lower — turbines sit on the seabed, minimal visual impact. Installed capacity: 30MW (2025), with MeyGen (Scotland, 86MW planned) being the largest. Tidal stream is favored today because it is modular, scalable, and has lower environmental impact. The global tidal stream resource is estimated at 1,200 TWh/year (~5% of global electricity).

Seawater is ~825× denser than air (1,025 vs 1.225 kg/m³), giving tidal stream a huge advantage in power density. At 2.5 m/s tidal current: P_density = ½ × 1,025 × 2.5³ = 8,008 W/m². Compare to wind at 10 m/s: P_density = ½ × 1.225 × 10³ = 612.5 W/m². A 1m² tidal turbine at 2.5 m/s captures 13× more power than a 1m² wind turbine at 10 m/s! This means tidal turbines can be much smaller for the same power output. Predictability: Tidal energy is perfectly predictable — we know tidal currents decades in advance through harmonic analysis of astronomical cycles (M2, S2, N2, K1, O1 constituents). Capacity factor: 30-40% for tidal stream vs 25-40% for onshore wind vs 40-55% for offshore wind. Key challenge: tidal turbines face extreme loads (10× higher than wind turbines), require robust sealing against seawater corrosion, and are far more expensive to install and maintain (marine operations cost 5-10× offshore wind). LCOE for tidal stream: $150-280/MWh (2025) vs $40-80/MWh for offshore wind.

Four main tidal stream turbine designs: (1) Horizontal axis turbines (most common) — similar to wind turbines, mounted on monopile or gravity base. Examples: SIMEC Atlantis (MeyGen, 1.5MW AR1500), Orbital Marine (2MW O2, floating). (2) Vertical axis turbines — cross-flow design, works in reversing currents. Examples: Bluewater (22ft tall, 500kW). (3) Oscillating hydrofoils — a wing-like foil moves up/down as tidal flow passes. Example: Pulse Tidal (pilot scale). (4) Enclosed turbines (venturi/duct) — duct accelerates flow through a shrouded turbine. Example: OpenHydro (defunct after 2018). Current global deployment (2025): ~35MW total. Levelized Cost of Energy has fallen from $500/MWh (2010) to ~$200/MWh and is projected to reach $100/MWh by 2030 with >100MW deployment. Key projects: Normandie Hydro (France, 12MW), MeyGen Phase 2 (Scotland, 86MW), Ulsan (South Korea, 200MW planned). The UK has ~50% of Europe's tidal resource and is leading deployment. India and Indonesia have significant potential in their island archipelagos.