(www.MaritimeCyprus.com) Under the European Green Deal, the EU has pledged to become climate neutral by 2050, with an intermediate goal of a 55% reduction of greenhouse emissions by 2030. Maritime transport, which has traditionally relied on the use of conventional fossil fuels, is preparing for a transformation to meet EU and international climate targets.
To this end, and to support the European Commission, national administrations, and industry in the ongoing decarbonisation of the maritime sector, particularly in the context of the FuelEU Maritime initiative, EMSA has produced a series of reports, studies, and guidance on alternative fuels and sources of power.
Wind
Wind-assisted propulsion systems (WAPSs) are seen as a technology that could reduce the fuel consumption from ships and consequently lower their greenhouse gas (GHG) and other emissions. There are several types of WAPSs that have been developed for the maritime industry; still others remain in development. These systems differ not only in terms of maturity, costs involved and fuel savings potential, but also in terms of their suitability for specific ship types.
Six categories of wind propulsion technologies are distinguished:
Rotor sails
Hard sails
Suction wings
Kites
Soft sails and
Hull technology
Aside from these systems/designs, wind turbines for electricity generation on board ships also are being developed.
The focus of this study, however, concentrates on the wind propulsion systems that can directly contribute to the propulsion of a ship. It presents an overview of current wind propulsion technologies for maritime shipping, based on literature reviews, internet research, information from the technology providers and input from the International Windship Association (IWSA).
Sustainability
Wind energy is a sustainable and renewable source of energy, which is abundant and inexhaustible. Wind propulsion systems allow ships to use this free energy source by converting wind power into thrust, supplementing or even replacing the main engine power of a ship. This leads to less fuel consumption, GHGs and other emissions.
It is difficult to specify an average effectiveness of WAPSs, because the reduction of the fuel consumption depends on several factors, ranging from WAPS characteristics (e.g., type, number and size of units) and ship characteristics, to operational (WAPS and ship related) and environmental factors.
In this study, publicly available results from numerical simulations and measurements, assessing the fuel and emission reduction potential from WAPSs, have been gathered. A big variation in the savings has been noticed due to the reasons stated above. Nevertheless, it can be concluded that under favourable environmental conditions the savings can be significant. As an example, rotor sails, which is the technology with the most available data so far, have been found to reveal up to 30% savings.
However, for an investment decision to be made, a ship specific assessment should be opted. Numerical simulations should be carried out, considering the ship and WAPS specific
characteristics, together with the intended trade ship’s routes and expected weather conditions. Crew training is expected to be crucial for the efficient use of WAPS.
Suitability
In case a WAPS is installed on a ship there are several aspects that should be considered. Firstly, deck space is required, the availability of which is often dictated by the ship’s type and size. For example, container ships and passenger ships traditionally have less available deck space than bulk carriers or tankers. For ships with space constraints, innovative solutions such as a towing kite or the use of a tug equipped with a towing kite are potentially alternative options. Containerised WAPSs have also been developed.
Additionally, a WAPS might prevent a ship from passing through bridges or it could hinder loading or unloading by cranes. Potential interference with cargo-handling infrastructure and land-based infrastructure (e.g., bridges) is thus another issue that needs to be addressed. These challenges are often tackled by foldable or tiltable WAPS solutions. Such solutions are also used to limit the undesired effects in adverse weather conditions.
Moreover, there are placement criteria which must be fulfilled to guarantee the safe and
comfortable use of WAPS (e.g., to avoid obstruction to bridge visibility or locating WAPS next to cabins on passenger ships).
The weight of the units varies significantly among WAPS types, but the subsequent effect on the vessels’ cargo capacity is not considered crucial. The ships’ structure might require reinforcement for a safe transmittance of the forces generated by a WAPS, but it is not expected to create any technical or financial barriers.
WAPS can be retrofitted on existing vessels or installed on newbuildings and it is worth
highlighting that the current share of retrofits is significant.
Availability
In this study, the availability of WAPS is considered along with the availability of wind itself.
The availability of WAPS is only seen as a possible short-term barrier to their potential wider adoption by the maritime shipping sector.
The availability of wind clearly impacts the efficiency of WAPS and this is greatly dependent on the proximity to the coastline, on the specific routes and their direction, as well as seasonal variations. To gain maximum efficiency from WAPSs, voyage optimization will be needed. Trade routes will need to be adjusted to find a balance between wind availability and route length. Also, switching ship deployments to specific trading areas with more favourable wind speeds and directions may be considered. Chartering commitments and clauses would need to be considered.
Risk and Safety
This study assesses several designs for ships equipped with WAPS from the risk-and-safety
perspectives; three specific ship types are analysed:
- A Ro-Pax Ferry using Rotor Sails
- A General Cargo using VentoFoils© (Suction Wings)
- A Wind Propelled H2 Assisted Container Carrier
The analysis demonstrated that the major concerns related to WAPS for shipping are related to vessel’s stability and maneuverability, change in air-draft, operational and navigational obstructions, obstruction in cargo loading/unloading (e.g., for bulk carriers), impact of adverse weather, ice accumulation, fire and lightning protection, noise and vibrations, system and component failures, maintenance.
The issues described above may require further studies for better understanding of the risks as well as for defining the necessary safeguards that will need to be implemented to prevent or mitigate the major hazards. Based on the Hazard Identification (HAZID) studies, preventive and mitigative safeguards as well as recommendations for various ship types are presented, which may help to inform prescriptive requirements and develop inherently safer designs and arrangements. While some safeguards are regulatory requirements, many of these are considered additional safeguards due to the inherent risks of WAPS. Overall, the studies did not identify any major risk that cannot be resolved.
To conclude, for the shipping industry, wind-assisted propulsion is not a new technology. To
facilitate its wider uptake on commercial vessels some additional safeguards need to be
considered, while WAPS reliability and availability may need to be further improved for the
maximum potential benefit to be realised.
Click on the below image to download the full EMSAÂ Report on the Potential of wind-assisted propulsion for shipping:
Source:Â EMSA
