Interest is growing rapidly in technology that can make crew transfer vessels more fuel efficient and reduce their emissions
An industry-wide push to reduce the environmental effects of shipping is underway. It takes many forms, depending on the sector, but most initiatives focus on using new technology to reduce CO2 emissions, fuel consumption and costs.
Not only does this benefit companies economically, it also reflects the responsibility the shipping and offshore sectors have in addressing climate change. Given that they are designed to support generation of clean energy, vessels in the offshore wind industry are an obvious choice for adopting emissions-reducing technology.
This trend was reflected in a June 2019 announcement that the Carbon Trust’s Offshore Wind Accelerator (OWA) had launched a competition to accelerate the development of technology with potential to reduce vessel emissions and fuel consumption. Up to £100,000 (US$127,000) in funding will be awarded to the winning technologies, from a total funding pot of £300,000 (US$381,000), to support technology development or demonstration.
Designs submitted to the competition will be assessed for overall cost, operations and safety advantages to ensure they are viable solutions for offshore wind operations. Vessel designs, power and propulsion technologies as well as energy-providing systems will be considered within the scope of the competition. The OWA study aims to reduce vessel emissions, fuel costs and vessels’ operational maintenance costs for offshore wind operations; understand and evaluate the cost/benefit of existing and future powering and storage technologies, particularly from other industries; and determine the infrastructure required for integrating this new technology into offshore wind operations. It is being delivered by the Carbon Trust and Black & Veatch on behalf of the Scottish Government and the nine OWA industry partners: EnBW, Eon, Equinor, innogy, Ørsted, Scottish Power Renewables, Shell, SSE, and Vattenfall Wind Power.
The Carbon Trust project is only now getting underway, but owners of CTVs have already begun investing in alternative fuels such as hydrogen, and investigating using batteries to reduce emissions. In March 2019, for instance, Vattenfall signed a contract with Windcat Workboats for CTVs for the Hollandse Kust Zuid 1 & 2 offshore windfarm in the Dutch sector of the North Sea that will use hydrogen as a fuel. Windcat Workboats is working with CMB Technologies on the CTV design, and believes that, should Vattenfall wish to do so, a hydrogen-powered vessel could be available to Vattenfall as early as 2020. If it takes up the option of using hydrogen-powered CTVs it could be the first to do so.
Another leading owner of crew transfer vessels also recently announced it is introducing a new class of vessel, in this case with a hybrid propulsion system that will enable it to operate with much reduced emissions – or without creating CO2 emissions at all. Northern Offshore Services said it believes its E-class vessels will be significantly more fuel-efficient than earlier classes of CTVs. The vessels will be fitted with diesel engines but will also have batteries fitted that can be charged from shore or when offshore, in a windfarm.
Northern Offshore Services said its E-class vessels would be the largest in its fleet. They will be designed inhouse and “will combine high energy efficiency and fuel savings without compromising performance and power.”
The innovative E-class will have four main modes of propulsion, including ECO-mode, when the CTV will be operated on a diesel genset at low speed with support from the batteries. This mode of operation will result in significant fuel savings and reduced emissions when the CTV is in standby mode. The E-class will also be able to operate in pure battery mode, without any CO2 emissions, when operations allow. They will have large diameter propellers that will operate at slower speed than conventional vessels to ensure a particularly high level of propulsion efficiency resulting in lower fuel consumption during transit and a higher bollard ‘push’ during docking. A growing number of commercial vessels are using shore power rather than diesel engines to reduce emissions, but Northern Offshore Services’ new vessels will also be the first CTVs prepared for battery charging while in a windfarm.
As Northern Offshore Services’ chief executive David Kristensson explains, “The future is green and the E-class is our first step towards a fully electrified CTV fleet. We believe electrification is a central part of the future of safe and environmentally friendly CTVs and we will continue to improve and develop our services. We are confident the E-class will be a great contribution to our fleet today and further strengthen our position in the CTV market.” The first E-class vessel, Energizer, is due to be delivered to the company at the end of 2020.
Working closely with Norwegian ship design company ESNA, another leading owner of crew transfer vessels, UK-based CWind, has developed a crew transfer vessel with hybrid propulsion that also incorporates batteries and a surface effect ship (SES) hullform that provides a form of air cushion damping, enhancing the ride quality for those on board. The company believes the hybrid SES has many potential advantages compared with conventional CTVs, including significant fuel savings and reduced emissions.
CWind senior project manager Ross McDonald tells OWJ achieving faster long distance travel while reducing CO2 was central to the vessel’s development. He explains that the CWind/ESNA team explored hybrid diesel/electric and hybrid diesel/hydrogen options. The team came to the conclusion that electric propulsion works best over shorter distances but, despite technological innovation that has reduced battery weight, it was not enough to counteract the need for a large, heavy battery needed for greater distances. However, in the longer term, says Mr McDonald, better battery technology could mean that a fully electric CTV comes to market before too long. For the time being, the current state of battery technology means that diesel engines were needed to supplement the electric pack.
CWind also considered hydrogen as a fuel, but Mr McDonald says that, at this point, CWind believes that hydrogen technology is not sufficiently developed to offer a suitable solution, although one could be retrofitted with fuel cells that would use hydrogen when the technology matures. The hybrid diesel/hydrogen was unable to deliver the CO2 savings to make it viable at this time, but CWind found that the hybrid diesel/electric option with a battery pack can deliver the speed and distance required while achieving a lower CO2 value.
A hybrid arrangement enables the innovative SES design to provide battery-assisted sprint speed and enhances its bollard pull. Using battery power as and when suitable – such as when idling or on standby in a windfarm or when transiting at low speed in harbour – reduces fuel consumption and emissions and reduces engine hours. This has a beneficial knock-on effect on engine maintenance because they would have to spend less time operating inefficiently at low power.
Such is its faith in the new design, that CWind has commissioned boatbuilder AMC to deliver the first example of the Hybrid SES by April 2020. It believes that, once in service, it will offer a step change in operational capability, performance and efficiency in support of offshore windfarm O&M and construction activities.