Engine factory Wärtsilä stimulates wind propulsion

Gone are the days when a manufacturer of large marine engines did not have to worry about wind propulsion. Thus, Wärtsilä has all kinds of ideas on how wind propulsion can improve the performance of conventional engines.

In an article on its own website, Wartsila lists a number of benefits of a WAPS (wind-assisted propulsion system) ‘that every ship owner should know’:

“Wind-assisted propulsion can be combined with other technologies to maximise both return on investment and efficiency gains. Here are four examples of technologies that can be used in conjunction with a WAPS.

A gate rudder

A gate rudder consists of two wings on either side of the vessel’s propeller, which can rotate independently of each other. This rotation changes the hydrodynamic load on both the propeller and fins. When manoeuvring in, out and around port, the fins act as a thrust guiding device.

A ship with a WAPS and a conventional rudder needs the flow of the propeller over the rudder to generate rudder forces. The gate rudder is located in the ship’s velocity stream next to the propeller. This means that the force of the gate rudder remains constant at constant sailing speeds, even if the propeller thrust is reduced to accommodate the thrust of the WAPS.

WAPS and voyage optimisation systems, including weather routing

Traditional voyage optimisation systems typically plan routes that avoid wind and optimise for the calmest weather. But if your vessel has a WAPS, you want to take maximum advantage of wind conditions along your route.

By choosing the right voyage optimisation system, this is possible. You can make smarter routing decisions with a Fleet Optimisation Solution (FOS). A good FOS includes a Voyage Optimiser tool that uses weather data, safety parameters and your efficiency targets to plan the most optimal route for your vessel. The optimal route is the one where your vessel’s WAPS can exploit favourable wind conditions to reduce fuel consumption and greenhouse gas emissions.

WAPS and hybrid systems

A hybrid system on board a ship combines an energy storage system, usually batteries, with a conventional engine. The battery captures peaks in power consumption, eliminating the dynamic load on the engine and reducing fuel consumption. Because the engine runs at a more stable load, it can be safely operated at higher load factors and there is less wear and tear.

With a WAPS, you can make an already flexible hybrid-electric system even more flexible. With the extra thrust generated by wind-assisted propulsion, you can further reduce the load on the ship’s engine. This has no negative impact on the efficiency of the electric motor. A hybrid-electric arrangement can also cope with varying wind conditions much better than a conventional arrangement.

WAPS and propulsion control systems and shaft generators

A smart propulsion control system, such as our EcoControl, identifies the most efficient set point between propeller angle and engine speed. These parameters are automatically adjusted in real time, allowing you to get maximum benefit from your WAPS.

If the route is planned so that the vessel can take maximum advantage of wind conditions en route, EcoControl can keep the engine as close as possible to the optimum operating point, where it is most fuel-efficient.

When using a WAPS such as rotor sails to generate thrust on a vessel with a 2-stroke main engine, you can drive the rotor sails using a shaft generator in power take-out mode. In most cases, using a shaft generator in this way helps to reduce the running hours of auxiliary units, thereby reducing maintenance costs.

WAPS and propeller feathering

In some cases, a WAPS can enable such a power reduction that it becomes feasible to switch off one of the ship’s main engines. If the vessel has a controllable pitch propeller (CPP), switching off a main engine will cause drag.

This drag effect can be eliminated by using the feathering capability of the CPP. In circumstances where the WAPS generates more aerodynamic thrust than your vessel needs to maintain the desired speed, you can use the CPP to generate electrical power.

In addition to these five approaches, there are other options. For example, you can tune your vessel’s engine to work optimally with WAPS. For ships with a two-stroke engine, one option is to implement closed-loop controllers between the engine, shaft generator and WAPS.

Source: Wärtsilä.

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