Tidal Energy Simulator

Understanding the HydreManche® simulator

This simulator is an educational tool. It does not predict the actual production of a given site, but it helps users understand the essential orders of magnitude involved in tidal stream energy.

In particular, it shows that:

the recoverable power depends very strongly on current velocity;
the mechanical loads exerted on structures also increase rapidly;
a rated power expressed in MW only makes sense when associated with a rated current velocity;
annual production depends on the full sequence of tidal variations, not on a simple average current speed.

In the short display modes — tide, day or typical week — the maximum site velocity can be adjusted using a slider. These representations are therefore intentionally schematic: their primary purpose is to help users understand the effects of current velocity on power and mechanical loads.

The Year mode, although still simplified, is closer to a site-based reading: it relies on values representative of a high-current area near Pointe de Goury, in the Raz Blanchard / Alderney Race sector.

The central physical point is the following: power varies approximately with the cube of current velocity, while mechanical loads vary with the square of current velocity.

A moderate-current site may therefore be of technical or experimental interest, but only sites with high, regular and exploitable current velocities can reasonably aim for industrial profitability.

The results displayed should therefore be read as orders of magnitude. They do not replace a detailed hydrodynamic study, an energy-yield assessment, or an industrial design study.

Tidal energy: installed capacity or actual production?

Installing 1 MW does not mean producing 1 MW continuously.
Energy policy targets are often expressed in installed capacity (MW), including in France’s Multiannual Energy Programme (PPE).
Actual generation is measured in megawatt-hours produced over time (MWh).

In tidal energy, this gap can be substantial.

Why tidal power output varies so much

The instantaneous power of a tidal turbine is given by:

P = ½ × ρ × C_p × A ×V³
with swept area A = π × D² / 4

It depends on the following factors:

– the density (ρ) of seawater, approximately 1025 kg/m³,

–the rotor swept area (A), which is proportional to the square of the rotor diameter (D²),

– the machine’s power coefficient (C_p) (e.g. 0.25),
– and above all, the cube of the current speed (V³).

As a result, when the geometry and characteristics of the machine remain broadly unchanged in the short term, current speed becomes the key factor determining instantaneous power. Even a modest change in speed can produce a very large change in power. At sea, current speed varies cyclically under the effect of the tides, driven by lunar and solar cycles.
Instantaneous power therefore varies sharply over time, because it depends on the cube of the current speed (V³).
Annual production results from the integration of these successive variations, and not from a simple calculation based on the average current speed.

What this simulator shows

Production depends on the cube of the current speed (V³).
Structural loads depend on the square of the current speed (V²).
The rated current speed (V_nom) determines the declared installed capacity in MW.
A rated power (P_nom) declared without its associated rated current speed (V_nom) has no usable physical meaning.
To understand what this model simplifies, and what additional constraints a real site introduces, see the page. 👉Technical background.

Quick user guide

Simulator available in English and French.

Start by setting the main turbine and site parameters in the left-hand column: rated power, rated current velocity, rotor diameter or swept area, selected coefficients and MWh price.

Then choose the observation period: tide, day, typical week or year. The short modes are mainly intended to show the immediate effects of current variation. The Year mode provides a broader view of estimated production.

Compare the curves and indicators displayed: current velocity, injected power, structural loads, energy produced and capacity factor. The aim is to visualise how the same machine can produce very different results depending on current velocity and the assumptions used.

The help icons (?) provide additional explanations of key technical notions: rated power, rated current velocity, Cp / Ct coefficients, mechanical loads, annual production and model limitations. They are worth consulting during a first use of the simulator.

Hydrolien — Simulateur V²/V³ (v07a CLEAN)

Simulateur hydrolien — vitesse, effort et puissance

Lang

Comparer la vitesse du courant, les efforts sur la structure et la puissance récupérable.

Vitesse maximale du site à 100 % (m/s)

Vsite(100%) = 4.20 m/s

Amplitude marée (coef 20 à 120)

Amplitude = 70% · coef 84

Échelle de temps

Puissance nominale Pnom (MW)

Pnom = 1.0 MW

Vitesse nominale Vnom (m/s)

Vnom = 3.50 m/s

Coefficient de performance Cp

Cp = 0.40

Rendement hydrodynamique du rotor.

Diamètre du rotor D (m)

Calculer D pour atteindre Pnom à Vnom

D = 19.5 m → Surface A ≈ 299 m²

D recalculé automatiquement selon Pnom, Vnom et Cp.

Coefficient de poussée (Ct)

Coefficient de poussée Ct = 1.20

Effort de poussée du rotor.

Inclure structure (approx.)

Effet de structure (× rotor)

Effet de structure ≈ 1.0 × celui du rotor

Paramètre simplifié à affiner selon la conception. La mutualisation de plusieurs machines sur un même support peut réduire ce facteur par machine.

Effort max (scénario) :
Moment max (scénario) : (bras z ≈ 0.7×D)

Prix (€/MWh)

Prix = 100 €/MWh

Puissance moyenne (fenêtre)

Facteur d’utilisation (fenêtre)

— %

Estimation fondée sur la puissance moyenne de la fenêtre affichée.

Lecture instantanée (curseur vertical)

Vitesse instantanée

m/s (±), km/h, nd

Puissance injectée

pics “flash”

Voir le calcul

Effort structural ~ V²

tonnes (≈ t)

CA instantané

€/h (P×prix)

Axe vertical de lecture

Position = 50% • V=— m/s • P=— MW • F=— kN

When power output becomes a structural issue

The simulator highlights a fundamental trade-off: improving regularity of production often leads to increased mechanical loads on the supporting structures.

The simulator visualises the effects of current variations on mechanical loads and on recoverable power.

In very high-current areas, the issue is therefore no longer only about energy. It also becomes a structural question: how can large-diameter machines be installed durably in extreme hydrodynamic conditions? The HydreManche raft principle is part of this line of thinking.

👉 Discover the structural approach

Limitations of the simulator

This simulator is a pedagogical tool designed to illustrate orders of magnitude relating to tidal currents, loads exerted on structures, recoverable tidal-stream power and estimated production.

It does not replace a detailed hydrodynamic study, industrial design work, real-world testing, a yield assessment, or a contractual performance forecast.

The results displayed are based on simplified assumptions. These assumptions are specified in the technical supplements and should be interpreted as elements for understanding, not as design data or guarantees.