Q&A: Glosten’s Peter Soles on new methanol-hybrid tug design

Written by Heather Ervin
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Peter Soles

Back in September, naval architecture firm Glosten and ABB announced that they have joined forces to develop a methanol-hybrid ship assist tug design that provides operators with a viable path to carbon-neutral operations while minimizing operating costs.

Referred to as the SA-100, the 100-foot ASD harbor tug is propelled by two methanol-compatible CAT 3512E gensets powering electrically driven L-drives. The gensets are complemented by battery banks for zero-emission operation when transiting, peak shaving during general operation, and as boost for achieving the tug’s peak bollard pull of 90 short tons.

Glosten’s Peter Soles, who has 22 years of marine industry experience—including seven years as an ASD (Z-Drive) tug operator and five years in ship operations management. At Glosten, Soles consults on projects involving tug and barge design and operation, navigation and ship handling, and marine logistics planning. He also leads the development of Glosten’s new concept design offerings for the workboat sector.

In this Marine Log exclusive Q&A, Soles tells us more about the SA-100 tug design and what’s new coming out of Glosten.

Marine Log (ML): What led Glosten to undertake this new design?

Peter Soles (PS): Simple. We wanted to introduce a harbor assist tug to the U.S. market that struck a balance between future-readiness, improved environmental performance, and total cost of ownership—but in all other respects resembled the form and function of modern assist tugs in use today.  This includes the ability to work around the clock in port districts with longer transit distances and high variability in daily ship movements. 

Most private operators don’t voluntarily adopt new technologies for reducing their environmental footprint because it introduces considerable commercial risk. Unless their competitors are compelled to do the same, the higher costs associated with adopting such technologies can put operators at a competitive disadvantage. At present, most shipping companies are unwilling to pay a premium for greener assist tugs.

However, when we learned that major U.S. engine manufacturers were close to unveiling high speed diesel cycle engines that could run on methanol, we began to see design pathways for a low-emission tug that could be commercially viable.  If we could manage to remove some of that commercial risk by minimizing total cost of ownership over the life of the vessel, we believed the demand was there.  Simply put, SA-100 was about introducing a low-emission tug design that is compatible with the business environment in which US towing companies are operating.


ML: Are there limitations to the boat as a result of using methanol as its primary power source?  Can it operate in the same way as tugs in service today or does it need to plug-in?

PS: Selecting methanol propulsion does require the operator to consider certain design tradeoffs.  Because methanol has roughly one-half the energy density of diesel, achieving those substantive reductions in NOx, SOx, and PM generally means sacrificing range and endurance, or, conversely, sacrificing valuable cargo or accommodation space to allow for increased tank volumes. 

But for many vessel operators, these are sacrifices that can be accepted.  Particularly for assist tugs and other harbor craft that generally don’t make long transits as part of routine operations, even a significant reduction in achievable range or endurance may be only minimally disruptive.  Generally speaking, it means more frequent stops to refuel the boat, which can be practically managed between jobs without impacting overall service availability. 

Apart from that, a methanol powered tug, and SA-100 specifically, can be operated in the exact same way as any other modern assist tug.  It is quite well suited to operation in geographically large port districts, like the San Francisco Bay Area, or ports that have frequent and/or unpredictable ship movements where tugs are crewed and working round-the-clock. There is no need to return to the dock for recharging. The battery systems are recharged by the gensets during normal operations and are onboard principally to deliver boost power. This allows propulsion engines to be appropriately sized for actual operational demands, as opposed to sizing them for full bollard, which results in needlessly high maintenance and operating costs.

ML: What led you away from an all-electric design?

PS: Apart from CapEx cost, both on the vessel side and for shoreside charging infrastructure, it was precisely that need to return to the dock to recharge after only a few hours of operating time. This is very limiting—to the point of being a non-starter for service in most major metropolitan port districts where ship movements are basically constant. 

All-electric tugs will still have their place; but when you think about a private, for-profit towing company that’s operating unsubsidized in a major international shipping hub, and competing for work against other towing companies, it is hard to imagine all-electric being commercially attractive. For applications like the one I just described, liquid fuels are going to remain the preferred energy source for the foreseeable future.

ML: What was the biggest technical challenge in developing this design?  What were the tradeoffs?

PS: Hands down, the biggest challenge in developing the SA-100 was trying to balance low gross regulatory tonnage (grt) with classification society requirements for hull-integrated methanol tanks.  The tank cofferdam requirements, specifically, remain the one serious obstacle to the adoption of methanol propulsion on small vessels.

The requirements are taken from the IGF Code, which was originally developed for oceangoing ships to use LNG as a fuel.  This regulatory framework was later applied to low flashpoint fuels, generally, because there was an urgent need to find guidelines for a number of alternative fuels that could help the industry cut greenhouse gas emissions. Unfortunately, it has something of the opposite effect on small vessels, and thus the appropriateness of this ruleset remains a matter of debate.  It is also still unclear to what extent flag-state regulatory bodies, including USCG, will attempt to mirror current class requirements for methanol fueled vessels.

Despite all this, we have managed to develop a selection of workable tank arrangement options for SA-100 that are consistent with present classification society requirements and maintain tonnage between 100 and 200 grt.

ML: Can we expect to see more methanol-powered vessel designs coming out of Glosten?

PS: Absolutely. This was not a one-time market experiment. This was a very deliberate act on our part to continue leading the development and introduction of viable next-generation vessel design concepts. 

Methanol is increasingly regarded by major ocean carriers as the most practical alternative fuel for broad adoption by the maritime industry. Engine manufacturers are already rolling out dual-fuel, diesel/methanol engines, so even if operators do not have a supply of methanol today, they can operate on diesel.  It also happens to be the least impactful to the design, construction, and operation of small vessels where all-electric is not an option. If you are a for-profit company looking to transition off diesel but are unable to accept the limitations of battery only propulsion, this is precisely the sort of vessel you should be considering. 

With the viability of methanol as a diesel replacement becoming increasingly clear to regulators and vessel operators around the world, you can expect to see many more methanol-powered vessel designs from Glosten in the future.

Categories: Engines & Fuel, Naval Architecture, Q&As Tags: , , , , , , , ,