The present thesis investigates the innovative energy ship concept for offshore wind energy conversion. In this concept, wind is used to propel a ship. Electricity is generated using water turbines attached underneath the hull. The electricity is converted through electrolysis into hydrogen which is then stored aboard. An energy ship is a complex system composed of many sub-systems.
In the first part of the thesis, a system engineering approach is used in order to develop a analysis framework for the comparison of solutions for the subsystems. A case study is conducted for the wind propulsion subsystem of an energy ship. Among the five technologies studied (soft and rigid sails, Flettner rotors, turbo-sails and kite wings), Flettner rotors are selected for an application on the energy ship.
In the second part a numerical model of the ship is developed in quasi-static conditions. It is based on the resolution of the equation of motion of the ship and on a potential flow method for the hydrodynamic part of the model. It shows that an energy ship with a catamaran hull of 80 m long is able to produce an electrical power of 1 MW in a 10m/s beam wind. This electrical power is equivalent to a weekly production of 2.9 tons of hydrogen. The nominal power of the ship (1.73 MW) is achieved at a wind speed of 12 m/s.
In the last part, hull optimization is performed using a genetic algorithm (NSGA II). The purpose is to maximize the energy production. Both symmetrical and non-symmetrical catamaran shapes are generated. Results show that non-symmetrical shapes, similar to “proa” ships, achieve the best efficiency. A gain of 15% of power production is obtained compared to the previous results (equivalent to a weekly production of 3.3 tons of hydrogen).
This PhD is linked to the FARWIND project and the eponymous company FARWIND ENERGY.
Stakeholders or Phd/Writer name
- Gaël CLODIC