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ELECTRICAL & ELECTRONICS


FEATURE


SAILING TOWARDS A CLEANER, GREENER, YACHTING INDUSTRY


Mike Torbitt, managing director of marine resistor manufacturer Cressall, examines how resistor technology could help make high-performance, low-emission, yachts a possibility


T


here were approximately 10,800 yachts afloat in 2022, around 5,400 of which were superyachts of over 30m. However,


according to an Indiana University study, a luxury superyacht produces around 7,000 tonnes of carbon dioxide each year. In fact a


superyacht’s annual carbon dioxide (CO2) emissions are said by some to be 1,500 times greater than that of a standard family car. Added to this, diesel-powered yachts produce


high levels of nitrogen oxide (NOx). International Maritime Organisation (IMO) legislation, brought


in during 2021, limits NOx emission levels and this has threatened the viability of superyachts


in recent years. Other marine vessels such as cargo ships use selective catalytic reduction


(SCR) to convert NOx into water and nitrogen. However, since this method requires high exhaust temperatures to decompose the exhaust fluid, it has been less successful in yachts due to a lower average engine load. It is time for the industry to move away from


fossil fuels. But how can this be achieved? ISSUES


The number of electric boat listings more than doubled between 2021 and 2023, according to boats.com data. This includes an increasing number of tenders using electric propulsion systems to transport passengers between the port and the yacht. While decarbonising the yachts themselves


presents a greater challenge due to their size and range of onboard facilities, there has been


significant progress on this front with the development of solar-powered yachts. With a predicted market value of 2.4 billion USD by 2031, solar energy charges the lithium- ion batteries used to power these ships and their facilities. Some recent models have even seen Li-ion batteries replaced with hydrogen fuel cells, which offer improved energy density and range. However, these recent innovations are not without issues. Although a solar yacht can fully benefit from sunlight when on open water, the position of other boats can block light from the vessel while it is docked. In addition, during rapid acceleration or deceleration, the power output of hydrogen fuel cells increases gradually to a point, but then begins to oscillate. This fluctuating power output can cause reliability issues.


HOW DBRs CAN HELP Dynamic braking resistors (DBRs) can help to tackle both problems. To maximise solar efficiency, it is beneficial to place the panels on the ground or sides of the boat so that they can be motor controlled to follow the sun’s position throughout the day. DBRs ensure that the positioning process is safe and precise, by dissipating the excess energy generated as the motors decelerate. As a result, more


MAY 2024 DESIGN SOLUTIONS 53


solar energy can be converted to power the yacht. DBRs can also be used to overcome hydrogen


fuel cells’ reliability issues and fluctuating power output. To make sure the yacht’s power requirements are always met even in the case of output oscillation, it is possible to install a fuel cell that exceeds these requirements. However, this option also requires a DBR to dissipate the excess energy when it is not needed. Cressall’s EV2 DBR offers an ideal solution, as its modular design means that a number of units can be combined to fulfil power requirements of up to 125 kW. As a water-cooled solution, it does not require fans to dissipate heat, making it lightweight and compact. With ten kilowatts (kW) of power per cubic decimetre (dm3


) and 9.3 kW of power per kilogram, it


avoids increasing the yacht’s load. Supporting renewable yachting innovations


with resistor technology will finally make high- performance, low-emission, yachts a possibility.


Cressall Resistors T: 0116 273 3633 www.cressall.com


Cressall’s EV2 DBR


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