Gate Rudder Integrated Wind Assisted Propulsion (GRASP)

Shipping is a vital component of the global economy, but it is also a major contributor to greenhouse gas emissions. According to the International Maritime Organization (IMO), the shipping sector is responsible for about 2.5% of global greenhouse gas emissions, and this share is expected to increase in the coming decades as global trade continues to grow. In response to this challenge, the IMO has established regulations such as the Energy Efficiency Design Index (EEDI) and the Carbon Intensity Index (CII) in an effort to reduce the carbon footprint of the shipping industry. The EEDI is a mandatory standard that applies to new ships and requires them to meet minimum energy efficiency targets, while the CII is a voluntary standard that applies to all ships and aims to encourage the use of low-carbon technologies and operational practices. The Gate Rudder Integrated Wind Assisted Propulsion (GRASP) project is focused on finding ways to meet these regulatory targets through the integration of Gate Rudder System (GRS) with Wind assist ship propulsion (WASP) technologies.

GRS is an energy-saving propulsion and maneuvering device that has been developed as an alternative to a Conventional Rudder System (CRS). It is designed to be more efficient and effective than a CRS, particularly in rough weather conditions. The GRS was first introduced to the market in Japan in 2017 and has been developed further through research and development activities in the UK and EU. The GRS has been applied to several vessels in Japan, including the first purpose-built coastal commercial vessel equipped with the system, which entered service in 2017. Trials of this vessel and a sister ship equipped with a CRS showed that the GRS-equipped vessel was 14-18% more efficient at the same design speed and 25-30% more efficient in rough weather. The GRS is also being demonstrated in a retrofit application on the MV Erge, a 90m coastal cargo vessel, which is expected to improve fuel consumption efficiency by up to 15% in calm water and at least 20% in rough weather.

WASP technologies, which use wind to generate lift and drag forces to propel a vessel forward, have the potential to reduce greenhouse gas emissions in the shipping industry. However, WASP technologies can also have undesirable effects on ships, including an increase in resistance due to heel and leeway angles, reduced main propulsor efficiency due to oblique propeller inflow, and reduced maneuverability due to a strong yaw moment. These effects can limit the potential of WASP technologies to generate significant propulsion thrust and reduce fuel efficiency.

One of the unique features of the GRS is its ability to act as an underwater sail, generating lift and counteracting the undesirable effects of WASP technologies on ships. By integrating the GRS with WASP technologies, it is possible to eliminate or minimize the increase in resistance caused by heel and leeway angles and the resultant resistance, as well as the excess resistance caused by a conventional rudder CRS to counterbalance the heel/drift due to WASP.

The GRASP project aims to demonstrate the feasibility of integrating WASP and GRS technologies and show that this integration can lead to fuel efficiency improvements of between 25-40% depending on the operational area. This could help shipping companies to meet the energy efficiency targets set by the IMO and reduce their greenhouse gas emissions.

The objectives of the GRASP project include:

Develop high fidelity computational fluid dynamics (CFD) simulations of the integrated WASP-GRS system to understand the performance of the system and optimize its design.

Conduct towing tank test experiments to validate the CFD simulations and gather data on the performance of the WASP-GRS system in different operating conditions.

Use propulsion drive simulations to assess the impact of the WASP-GRS system on the overall performance of the vessel, including its fuel efficiency and emissions.

Test the WASP-GRS system on a target vessel to demonstrate its feasibility and performance in real-world conditions.

Disseminate the results of the project and promote the adoption of the WASP-GRS system as a means of improving the energy efficiency of ships and reducing their carbon footprint.