Two-in-one Solution Trounces 'Tandem Machine' Approach


Published Jun 23, 2020 2:45 PM by The Maritime Executive

Mulling a drive-train investment for a newbuilding or vessel upgrade? You might have been considering two motors running in tandem, but in my opinion there’s a much better way to save fuel, space and weight. Ville ParpalaDirector, Product Marketing, Yaskawa Environmental Energy / The Switch, explains why separate power drives feeding one larger machine with multiple windings provides a competitive alternative

I meet a lot of chief engineers tasked with sourcing drive solutions that are more fuel efficient and reliable than what’s gone before. It’s a demanding job with a lot of options to weigh up. What’s best in terms of extending available power while reducing fuel burn and increasing redundancy? Most importantly, can I justify the expense and the payback time?

Often due to a perceived lack of alternatives, many might mistakenly think that for offshore vessels, workboats and merchant ships, a so-called “tandem machine” setup involving two rotating motors on the same shaft line is the best way forward to achieve fuel savings.

There is a better way
At Yaskawa Environmental Energy / The Switch, we’ve noticed an increasing market trend in this kind of enquiry. We try to put people straight immediately. Many are surprised to hear there’s an even more effective, viable alternative that is significantly cheaper and investment saving.

The tandem approach really doesn’t make sense in all cases when you scratch the surface. Why double things up with a more expensive, bulky solution that requires longer shafts, couplings between machines, more bearings, more moving parts and more maintenance?

Less space, less weight
Our optimized solution uses a single larger machine with dual (two-in-one), triple (three-in-one) or even quadruple (four-in-one) windings on the same stator, plus up to four individually connected drives to achieve the same thing and more. The increasing “in-1” options will depend on the vessel’s operational power requirement. The setup takes up less space, which means more space for cargo. It weighs substantially less, which in turn, reduces fuel burn. Crucially, for a 2-in-1, you’ll pay up to 30% less than a tandem machine. For me, it’s a “no-brainer.” But that’s not my opening gambit when I’m chatting to chief engineers!

The redundancy factor
There’s also less power loss from one large machine instead of two smaller ones. The individually connected drives also increase redundancy. There may not be “demand” for the full power of the larger machine in normal operations, but the power is there to ensure safety. For example, with two drives feeding a 2-in-1 machine, no matter if one drive fails, the other half remains available, giving around 50% uninterrupted power – or 75% in the case of a 4-in-1 setup.

Bespoke is best
Our unique value proposal offers dynamic engineering where we customize the system to fit the available space. That’s obviously easiest on a newbuilding for which the yard can specify the dimensions of the machine rather than those of the hull. Plus, our modular power drives can be adapted to multiple locations on the ship. Again, reduced space and weight result in less fuel consumption, while a smaller engine room allows more room for freight, enhancing the vessel’s earning potential. As an example, we saved around 40 tons of weight in a fishing vessel that could be used to transport product, not the equivalent mass in engine machinery!

For vessel upgrades, our recommended optimal solution is installing a permanent magnet shaft generator that can also be up to 4-in-1, as the machine construction is the same. For example, for a bulker on long voyages, the shaft generator can be used as fuel-saving backup to the main engine with a payback time of as little as two years.

It’s electrifying
Alternatively, if the ship is being wisely hybridized, a permanent magnet shaft generator can be combined with batteries and used as the main propulsion motor with limited power, which is surely enough for port maneuvering or anchoring purposes. Here, our portfolio really supports the shift to a sustainable mindset.

I know many owners are concerned and want to do the right thing to meet increasingly tough regulations. Ship electrification is our mission, providing hybrid solutions supported by permanent magnet machines and our DC-Hub that can connect everything with any energy source, both existing and emerging fuels. Things are moving fast!

At Yaskawa Environmental Energy / The Switch, we’re especially proud of our flexibility and ability to deliver bespoke solutions in small volumes, which the “in-1” solution exemplifies. We’ll fit one ship or as many as needed with robust equipment that future-proofs our customers’ OpEx.

During these times when the only certainty is uncertainty, serving as a single trusted supplier of both the machine and drives is something I believe they really value.

The products and services herein described in this press release are not endorsed by The Maritime Executive.