2023-09-08 06:30:42
The start-up Farwing Energy is developing a concept for an energy ship that moves using the wind and produces electricity using hydrogenerators installed under the hull of the boat. This energy is then stored on board, before being used on land. Interview with the ship technical director of this company.
Today, more and more competition sailboats, but also pleasure boats, are equipped with a hydrogenerator to produce energy. The rotation of a propeller underwater then makes it possible to power an alternator and produce the electricity necessary for the boat’s needs. In 2016, the École Centrale de Nantes began to take an interest in the design of an energy ship, whose sole function would be to produce energy in large quantities, store it on board, and then release it. valorize on land. From this research work, the start-up Farwind Energy was born in 2020, which continues to develop this concept. Antoine Caillaud, the ship technical director of Farwind Energy, talks to us regarding this project.
Engineering Techniques: Describe the concept developed by Farwind Energy to us?
Antoine Caillaud, ship technical director of Farwind Energy. Credit: Farwind Energy
Antoine Caillaud: It is a sailboat, that is to say a ship propelled by the wind, using Flettner rotors, which are in the form of vertical cylinders rotating around their axis. We chose them because they are better suited than other sails to crosswinds. Under the hull of the boat, hydrogenerators are placed whose role is to produce electricity by means of a propeller which turns thanks to the movement of the boat. Depending on market needs, the energy produced is stored in three different ways: in lithium batteries, in the form of hydrogen, and finally in a more distant future, in the form of e-fuel such as methanol, by taking CO2 on board.
How much electricity is produced on the boat?
An illustration of the energy ship concept. Credit: Farwind Energy
The ship has a useful power of between 2 and 2.5 MW and which corresponds to the remaining energy that can be stored and then recovered. To achieve this, approximately 3.5 MW must be produced by hydrogenation, because approximately 1 MW is consumed on the boat by the on-board utilities, the pipeline, as well as the Flettner rotors. These rotors are part of the active sail category and are equipped with motors, which consume electrical energy, but provide propulsive power far greater than their consumption. The whole challenge of our concept is to optimize the production of electricity, that is to say to move the boat forward using these rotors, then to brake it optimally using the propellers. hydrogenerators. If you brake too much, the boat does not move forward enough and the energy produced becomes very low; conversely, if we do not brake at all, it becomes equal to zero. Between these two extremes, there is an optimum to be found.
What innovations have been made to design this energy ship?
We are developing Flettner rotors that are larger than those currently available on the market and measure 5 meters in diameter by 35 meters high. To achieve a useful power of more than 2 MW, they must measure 7 meters in diameter and 50 meters high. We are working in particular on new bearings which are capable of withstanding the forces associated with these rotors, which rotate at more than 100 revolutions/minute and whose weight exceeds 100 tonnes.
We are also developing new blade profiles for hydrogenerators. Their shape does not resemble propulsion propellers, nor the propellers present on hydrogenerators already fixed in the ocean floor and which operate thanks to sea currents. We seek to optimize their shape to slow down while having optimal electricity production efficiency.
The energy storage part also involves innovation, particularly when it is transformed into hydrogen. Solutions for producing water by electrolysis and then storing it in compressed or liquefied form already exist, but the marinization of these systems requires us to remove several technological obstacles. The same goes for unloading, that is to say the way in which we transfer this hydrogen once stored.
Finally, engineering work is carried out regarding the overall design of this energy ship. The structure of the boat must be sufficiently rigid and stable, while being inexpensive, and be sufficiently efficient from a hydrodynamic point of view, to minimize the drag of the vessel and therefore lose the least energy.
What are the advantages of your concept?
When we look at maps of offshore wind potential, we see that the strongest winds are located offshore. The advantage of the boat is that it can move to areas inaccessible by installed or floating wind turbines. Given that the boat is far from the coast, there are few conflicts of use, whether with local residents, visually, or with fishermen, who want to protect their fishing areas. As the boat is mobile, its trajectory is potentially different for each energy production campaign, depending on wind forecasts. For example, if it leaves Saint-Nazaire, it can head towards the North Sea, towards Ireland or head towards the Bay of Biscay, if stronger winds are forecast in this area. Our concept is also a quickly deployable solution, which does not require a soil study for example, nor the design of a specialized vessel for its implementation. Finally, the energy is delivered to the port, so it is close to the users and there is no need for land connection or distribution installations.
How long does a sea campaign last to “fill up on energy”?
An illustration of the boat at sea. Credit: Farwind Energy
For battery storage, this time is short, being approximately one day. It would be possible to increase this time, but the more capacity we install on board, the heavier the boat becomes, and the less efficient it becomes in terms of energy production. Conversely, if it is less heavy, we spend our time going back and forth. We have worked on several typical cases, notably in Guadeloupe and with the officials who develop the PPE (multi-annual energy programming), a document which defines the energy strategy of the French territories, in mainland France and in the overseas territories. sea. By 2035, several energy ships might be deployed in the Caribbean. One of the possibilities would be to send an energy ship from Basse-Terre so that it makes two to three round trips per load in the south of the islands, where the trade winds are strongest, before returning to the quayside. to unload.
For compressed hydrogen, a production campaign would take around a week, while for liquefied hydrogen and e-fuel it would take around two to three weeks.
When will we see the first energy ship on the sea?
We are still at the study stage. Last year, our efforts focused on the design of ships with battery storage. This year, as part of an Interreg project called Maghic and financed by European funds, we are working a lot on the hydrogen version. A priori, it represents the best storage method to begin manufacturing the first boat by 2027.
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