Redesigning deck machinery with batteries to store power can help owners reduce genset sizes and emissions
Green technology trends influencing tug design and construction also have an impact on the type of deck equipment, including the winches and cranes owners require on vessels. Tugs with batteries and electric propulsion need additional power to drive electric winches and deck equipment.
Owners are under pressure to cut their vessels’ environmental footprint and minimise spills from the hydraulic oil used to control and power deck machinery.
Tug operations have different demands for deck equipment, such as varied bollard pulls, line speed, winch line force direction and the type of line used. All these factors mean manufacturers need to tailor deck gear to meet owners’ evolving requirements to reduce emissions, prevent hydraulic oil spills and handle next-generation ships.
DMT Marine Equipment chief executive Piet ter Schure says demand is increasing for compact winches with lower power demand and less weight, as naval architects design smaller tugs with shorter deck space.
There is also growing pressure to lower engine and generator sizes and reduce fuel consumption and emissions. In response, DMT is developing a hybrid winch for tugboats, with batteries to store energy that would otherwise need to be produced from the tug’s generator sets. Mr Schure says this could help reduce the size of onboard gensets from 200 kWe to 50 kWe.
“We are changing our philosophy on winches as it is not just reliability but also what we can eliminate, with a focus on compact sizes, mainly due to the dimensions on board,” he explains.
“We have to lower weights and the environmental footprint, but we must never forget the high reliability needed for winches – there should be no downtime.” This means eliminating areas of weakness and energy consumption on winches, such as internal clutches and the dynamic brake, and finding innovative ways to store energy. The dynamic brake controls payout of the line, but it turns energy into heat and friction and causes a lot of wear and tear.
DMT’s new hybrid winch concept eliminates clutches and the dynamic brake by having four in-line motors and batteries to store energy generated from line rendering.
“Our hybrid winch can generate and store power in batteries for later reuse,” says Mr Schure. “It would be reliable, responsive and efficient, while the major gain is the possibility of lowering the capacity of gensets on board.”
Generators are selected for the highest consumer, often the winch on tugs, so there could be a 50% reduction in power requirements with a hybrid winch.
“Our new concept would contribute to lowering fuel consumption and emissions, with a lower footprint, less wear and tear and lower operating expenditure, but still with the responsiveness and safety on board,” says Mr Schure. Capital expenditure will be higher, but this could be paid back within five years. “Electric-hybrid winches have emerged as a crucial technology.”
DMT plans to test the first electric-hybrid winch before the end of this year. But there are still challenges to overcome with its development. “One of the most significant obstacles was finding the perfect battery pack that could rapidly absorb energy during wave-compensating mode,” Mr Schure explains.
“We were faced with daunting peaks that required ingenious solutions beyond the conventional use of dynamic brake or brake resistors. The specific deep knowledge of electric motors, dynamos and batteries is a benefit, but it is challenging to find a supplier that has the capacity to invest time and financial resources in developing their part of the system for us.”
DMT has established the best combination of speed and force, “while a special setting will always make sure that during manoeuvring, a back tension will remain on the wire rope, allowing the user to move fast from starboard to portside without worrying about the rope itself,” he continues.
This hybrid-electric winch would be a high-end system, designed as a new unit with minimal use of components and a minimal power input. “We are revolutionising the way winches operate and unlocking a new world of possibilities,” says Mr Schure.
Through research and development, DMT has discovered a significant amount of heave movement that was previously wasted could be captured and converted into electric energy and stored in batteries to be used later on the tug.
“Our electric-hybrid winches represent a game-changing solution that not only improves performance but also supports global efforts to reduce greenhouse gas emissions,” says Mr Schure.
Tailored approach
Even without technologies for reducing energy use, manufacturers still need to tailor deck machinery to the plethora of owner requirements.
“Tailor-made equipment has become a necessity as standard designs no longer fulfil the evolving needs of ship designers,” says Mr Schure. “Customisation is useful as it addresses specific needs and is more efficient when it comes to material usage.”
DMT uses analyses requests for tailor-made deck equipment to identify trends that stand out: high power in a compact design, lightweight, certified electric components for an explosive environment, and complex render and recovery systems.
“We have supplied customised, compact, automatised and lightweight winches, to support the efficiency of different propulsion systems,” he adds.
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