Wind-assisted ship propulsion can transform shipping
Originally posted in The Ray.
By Giovanni Bordogna and Nico van der Kolk
Blue Wasp is an engineering consulting firm specializing in wind assisted ship propulsion that offers independent technical advice to support decision making for stakeholders in the shipping industry. Drawing on 10 years of subject-specific research experience at TUDelft (in the Netherlands), the company helps realize the unique economic and environmental benefits of wind assistance.
Giovanni Bordogna holds a doctorate in the aerodynamics of wind vessels from TUDelft. He is a goal-oriented engineer with a strong passion for green technologies and entrepreneurship.
Nico van der Kolk is an experienced engineer with extensive experience in numerical experimentation and simulation and a keen interest in environmental policy and regulation. He holds a doctorate in the navigation behavior of wind vessels from TUDelft.
The global shipping industry transports around 90% of global trade by weight, which accounts for almost 3% of human-made CO2 emissions. In collaboration with TUDelft (in the Netherlands), the design office Blue Wasp wants to change the course of things.
Left to the status quo, the industry’s greenhouse gas emissions are expected to increase by 50-250% by 2050 from 2012 levels. In addition, most of the world’s fleet is still burning. heavy fuel oil (HFO), which is unrefined residual petroleum containing a high percentage of sulfur. As a result, the maritime transport sector is responsible for approximately 13% and 15% respectively of global emissions of sulfur and nitrogen oxides due to human activities. To put it in perspective, only the 15 largest ships emit more of these noxious gases than all the cars in the world combined.
Although slowly, things started to change. In April 2018, the International Maritime Organization (IMO) identified ambition levels to reduce total annual greenhouse gas emissions by at least 50% by 2050 compared to 2008 and to pursue efforts to gradually eliminate them. Some regulations aimed at improving the efficiency of newly built and existing ships have already been applied, but several academic studies have indicated that these efforts are insufficient, especially if the shipping industry is to align with the objectives set out in the Agreement from Paris. Several measures are currently under discussion and it is likely that more stringent regulations, which will have a considerable impact on day-to-day shipping operations, will be applied in the short term.
Along with political environmental policies, various private initiatives have also emerged. For example, the Getting to Zero coalition, an alliance of more than 120 major players in the maritime, energy, infrastructure and financial sectors, has committed to âbuilding commercially viable zero-emission offshore vesselsâ during over the next 10 years. It is a grand declaration that requires radical and urgent interventions to follow it up.
To make the decarbonisation of the maritime sector sustainable, many technical solutions have been proposed and several projects are underway to demonstrate their feasibility. The vast majority of these include new types of fuels like biofuels, ammonia or hydrogen that promise to completely eliminate any harmful greenhouse gas emissions when burned. While very promising, in the event that these fuels are sustainably sourced, these solutions may still be a decade away as they require a whole new infrastructure to be produced and distributed.
Among the technologies proposed for the energy transition, wind propulsion for ships (WASP) stands out. Wind propulsion, in fact, is a so-called primary renewable energy. It does not require new infrastructure or storage because wind energy is directly transformed into propulsive energy on site. This considerably reduces the costs of its application and avoids the efficiency losses associated with the storage and transformation of energy. Another huge advantage is that wind is a free source of energy and several WASP technologies are already available and ready for large-scale adoption.
It might sound like a throwback to the old days, when large clippers, powered solely by the power of the wind (and dozens of sailors) were employed in world trade. But, in fact, things are very different these days. As the name suggests, wind-assisted propulsion is a hybridization for ships, where the ship’s propulsion is split between a “sail” system and a main thruster. The operation of ships does not depend on the availability of wind, as one might think. Instead, if there is a lack of wind along a given voyage, the ship must rely on the main engine to get to the next port on time.
These steel sails (some being actually aluminum or composite construction) help propel the ship, thus saving fuel and improving transport efficiency. Modern wind-assisted propulsion devices can be of different types. There are wing sails (like stiff and highly efficient sails), kite sails that take advantage of stronger winds at high altitudes, and active devices like Flettner rotors (large rotating cylinders) and Ventifoils. (wings aspirated). The latter two are high lift devices that require an input of energy to operate, but in return they can provide much more aerodynamic thrust than the square rig sails of yesteryear. This is good because ships have also gotten bigger, where the power needs of larger commercial vessels are similar to the power demands of a small town.
This extra aerodynamic thrust can be applied directly to move the vessel forward (unlike the transmission losses involved with the main engine), but there are a few complications. Like any wing profile, the lift and drag properties of a WASP sail system will produce beneficial thrust, but also transverse heel force. The ship’s hull will need to balance this new transverse force, resulting in a new operating condition for the ship. Being otherwise optimized for a very specific and symmetrical operating condition, the resistance of the vessel will increase and this increase can in fact counteract the aerodynamic thrust. Finally, the new operating conditions can have a significant impact on the controllability of these vessels, in particular if large installations are envisaged.
Nonetheless, existing vessels with a WASP retrofit can expect savings in the order of 10-20%, depending on the wind conditions and how the vessel is operated. On the other hand, a new WASP vessel designed for full use of available wind energy promises savings of over 50%. This is a remarkable result which can only be achieved if the wind assist devices are correctly integrated into the ship from its initial design.
While the timing of these hybrid vessels does not depend on wind availability, the amount of fuel that can be saved on a voyage is certainly influenced. Therefore, active routing of vessels to find the most favorable wind conditions is an important part of the story here. To take full advantage of the beneficial wind conditions, the vessel should be operated differently from what it is today. It must be able to change course and speed, while keeping the arrival time unchanged from the status quo. With the 10 WASP vessels currently in service, this is not yet the case. A change of mind is needed first, but it will be worth it as active ship routing is proven to dramatically increase the amount of fuel that can be saved.
Responding to the call for greening the maritime sector, a new generation of engineers and entrepreneurs are developing the technical and practical feasibility of several effective WASP devices and full integration with vessel operating and financing models . It’s time to embrace the promise of wind assistance. This is a compelling short-term intervention alongside the shutdown of fossil fuel engines, and going forward will be a key part of the energy mix of the new zero-carbon fleet.