Environmental concerns are influencing a greater need for renewable and sustainable energy across the world with specialist technologies being at the forefront of new designs and solutions. The environmental impact of shipping includes air pollution, water pollution, acoustic, and oil pollution. Commercial ships are responsible for more than 18 percent of some air pollutants, including greenhouse gas emissions. The International Maritime Organization (IMO) estimates that carbon dioxide emissions from shipping were equal to 2.2% of the global human-made emissions in 2012 and expects them to rise 50 to 250 percent by 2050 if no action is taken.
There is a perception that cargo transport by ship is low in air pollutants, because for equal weight and distance it is the most efficient transport method. This is particularly true in comparison to air freight. However, because sea shipment accounts for far more annual tonnage and the distances are often large, shipping’s emissions are globally substantial. A difficulty is that the year-on-year increasing amount shipping overwhelms gains in efficiency, such as from slow-steaming and improved designs. The growth in tonne-kilometres of sea shipment has averaged 4 percent yearly since the 1990’s. There are now over 100,000 transport ships at sea, of which about 6,000 are large container ships.
In 2019, new legislation stipulated that all new ships for UK waters ordered from 2025 should be designed with ‘zero-emission capable technologies’. This commitment is set out in the Clean Maritime Plan, part of the Government’s Clean Air Strategy, which aims to cut down air pollution across all sectors to protect public health and the environment. It will also help deliver the United Kingdom’s commitment to be net zero on greenhouse gases by 2050. As maritime industries begin to tackle climate change issues, ports and shipping companies are looking for carbon-free alternatives by testing potential solutions for vessels. The requirement to make a move toward greener shipping is imminent.
Wind Propulsion Technology
To address the problem of global commercial shipping, the introduction of WPT (Wind Propulsion Technology) has been evaluated. According to some recent studies, wind-assisted ship propulsion using rigid wings, sails, kites, Magnus rotors or other novel devices on some specific vessel types such as bulk carriers and tankers, have the potential of fuel savings and emission reductions around 10%. Windship Technology Ltd, a sail power concept being developed by a consortium of key players in the global shipping industry, have evolved the latest advancements in wind turbine blade design and high performance composite solutions to achieve a much higher emission reduction of 30% on average. Their concept design could revolutionise the way tomorrow’s vessels carry goods across the world’s oceans.
The solution, known as the Windship Auxiliary Sail Propulsion System (WASPS), uses fixed wing sail technology, whereby three 35m high masts installed on the deck of a vessel will each have three aerodynamic solid wing sails to exploit the power of the wind. Using their expertise in ship design and composite technology, the mast rigs are highly engineered for performance, strength, lightweight and efficiencies, to ensure maximum driving force. The system allows reductions in engine power to be made in order to achieve the same speed and so maximise fuel-saving and emissions reduction.
The patented UK designed Windship rig system is consistently regarded as the most powerful fuel and emission saving wind system in the market, which will materially help the shipping industry move closer towards achieving its reduction in emissions. The IMO have recently acknowledged wind propulsion as one of the solutions for the shipping industry to meet decarbonisation targets.
In order for the shipping industry to adopt these new technologies, the accurate analysis of the potential savings and the results must be presented to all stakeholders involved. In order to achieve this, improved simulation techniques are needed to optimise design and routing. Several factors need to be accounted for, including the aerodynamics of the thrust producing devices, the vessel hydrodynamics, propulsion system and the optimal routing.
Computational Fluid Dynamic Simulations
Due to our renowned experience and specialist technology, we are able to offer a holistic analysis of the benefits of Wind Propulsion Technology (WPT).
Dr.-Ing Rodrigo Azcueta, Managing Director of Cape Horn Engineering, comments ”We are extremely proud to be part of the team led by Windship Technology for this exciting project, running a Computational Fluid Dynamic programme to further improve the design of the solid wings. One of the key focuses of our project is to provide a clearer, unbiased and more detailed analysis of the new technologies available. This allows interested parties to be confident in the investment of greener technology. The analytical evidence provided will give businesses a clearer understanding of the potential savings that can be realised with the implementation of the green propulsion systems. Without significant mitigating action it is projected that the global shipping industry could account for almost a fifth of carbon emissions by 2050.”
A multitude of wing assembly shape configurations were analysed in varying wind conditions. In total, almost one thousand, high-fidelity CFD simulations were performed and analysed. The simulations were used to set up force models needed to describe the vessel’s hydrodynamic and aerodynamic behaviour. Operating conditions for the WPT devices are apparent wind angle and speed, wind shear and wind gradient (variation of wind speed and direction with height above the water surface), and angle of attack of the wings and its flaps.
A 2 digit percentage improvement in the aerodynamic performance of the wing assembly was obtained. Some selected simulation points were compared and validated with the wind tunnel testing, as well as with previous CFD analysis provided by Lloyds Register. Experts from the Wolfson Unit (University of Southampton) were also involved in the analysis of the CFD results. Extreme wind load cases were delivered to structural experts from Gurit for assuring optimum weight and safety of the structures.
Key industry experts, prospective clients in the shipping, commodities and petrochemical sectors together with UK government officials attended the R.J. Mitchell Wind Tunnel of the University of Southampton to view the testing of the Windship Technology model in February 2020.
Simon Rogers, Technical Director of Windship said, “We are delighted with the results of the wind tunnel testing, they validate our CFD modelling and further illustrate how we will help the shipping industry to make a significant reduction in CO2 emissions. We are in discussions with potential development partners to build and install the prototype system.
These environmental benefits must be realised as soon as possible. The sooner these fuel-saving propulsion systems are used, the sooner the daily emissions are reduced. There are currently very few ships in operation that harness the power of the wind for propulsion, and there are no ships in operation that implement a wing design. The UK has always been a leader in the shipping industry, we are taking the next step to solidify the UK’s position in the market with the forward-thinking and innovative technological solutions”.
Further design optimisation
Further CFD design optimisation in 2020 will take the Windship concept ship into consideration as a whole, including the ship hydrodynamics, engine and propulsion, aerodynamics and optimal routing. The operating conditions for the vessel will be the advance speed and the drift, heel and rudder angles. Furthermore, windage on superstructures and the added resistance due to sea state will be modelled and taken into account.
Dr.-Ing Rodrigo Azcueta, comments “When it comes to building a new ship, the design must be optimised to fit the wings on deck efficiently from both an operational and performance perspective. The design of hull features such as skegs or bilge keels might be required to balance the transversal instability induced by the installation of the WPT. Having a CFD model comprising of both the hydrodynamic and aerodynamic artefacts of the design will allow highly targeted design optimisations. Currently, wind propulsion systems and ship design are considered as two entities, hence they are designed independently. It is reasonable to believe that they should be designed as a whole from the earliest stage, due to the dependency of each aspect on the other. The optimisation process and predicted potential performance will determine the optimal operational points resulting in the lowest required engine power, fuel consumption and total emissions. The aim of our project is to facilitate the uptake of WPTs. Moreover, we hope to enable the implementation of these technologies in the shortest timeframe possible”.