The offshore wind industry has been facing rough seas in Japan, where literally rough seas, deep water, and other factors have stymied development. Nevertheless, Japan is finally poised to take advantage of its generous coastline, and electric boats could play a key role.
The Offshore Wind Industry Needs More Electric Boats
For all the clean kilowatts generated by offshore wind turbines, the carbon footprint of the construction phase needs some tidying up. Offshore wind farm developers generally use the same fossil fueled service boats to ferry crews and equipment back and forth that are used in other offshore industries.
That is beginning to change. Electric boats are beginning to make an appearance alongside at-sea charging systems. The UK firm MJR Power offers one example of an innovative approach to at-sea charging. The company’s award-winning charging system deploys electricity directly from offshore wind turbines. In addition to providing electricity for back-and-forth traffic, the system will enable service vessels to turn off their diesel engines while idling at the site.
The Battery-Swapping Electric Boat Solution
Another type of electric boat charging solution is brewing in Japan, where the UK’s Zephyrus Marine collaborative watercraft electrification hub has hooked up with Japan’s Mirai Ships to build an electric boat to service offshore wind farms. The British firm Ad Hoc Marine Designs Ltd will provide the design.
Actually, it’s not just one electric boat. The project involves building a Zephyrus “Mothership” electric boat that doubles as a floating charging station and hotel for offshore wind crews, who will be ferried around on a whole fleet of electric “daughter” crew transfer vessels, aka CTVs.
“These daughter vessels will be lifted off the Mothership and launched into the field. When the charge is low, these CTVs will return to the Mothership to dock at the stern, allowing for the spent batteries (“e-pods”) to be lifted and replaced with fully charged ones within minutes,” the partners explained in a press release last week.
Battery Charging Vs. Battery Swapping
If you caught that thing about e-pods, that refers to a battery swap. Technically speaking, the daughter vessels are not recharging their batteries at the Mothership. Instead, they are swapping out their spent batteries for fresh ones, deploying the PwrSwäp system developed by the British Columbia-based company Shift Clean Energy.
The swap-out system compares favorably to recharging the same battery because it saves time. Swapping can also save space and weight on the CTV boats, because it offers the opportunity to right-size the batteries down to the minimum needed to run a route.
The PwrSwäp model also provides a cost-cutting subscription service rather than an up-front investment in energy storage technology.
“The Zephyrus Zero Carbon Offshore wind service operation will utilize Shift’s PwrSwäp technology — a pay-as-you-go energy subscription service that delivers instant renewable, clean energy to vessels without risk,” the partners explain. “As a result, vessels can utilize only the energy they need without committing to a fixed energy storage system.”
Keep an eye out for more news about Shift. The company is new to the CleanTechnica radar, but its cloud-based service and management model seems to be catching on. Shift has already opened offices in the US, UK, and the Netherlands, and another one is forthcoming in Singapore.
Sturdy Electric Boats For Rough Seas
Another interesting aspect of the Zephyrus electric boat partnership is the choice of daughter electric boats.
“With Japanese waters known for the rough seas all year around, it was a natural fit to use Ad Hoc’s SWATH CTVs, which are tailor designed to withstand such harsh annual conditions,” the partners stated.
There is more to that statement than it may seem. Last December, the 4C offshore wind analysis and consulting firm got a rundown on SWATH technology from the owner of Ad Hoc Marine Design, John Kecsmar, who is well known as a naval architect and designer of SWATH vessels.
SWATH stands for Small Waterplane Area Twin Hull, a design that has begun to catch on in the offshore wind field. However, 4C writer Sue Allen notes that the number in use is still relatively low, at 21 CTVs compared to more than 440 vessels in action for the offshore wind industry overall.
Allen also counted just one SWATH service operations vessel in operation, though two more are under construction at a shipyard in Turkey.
Compared to conventional monohull construction, the twin hull approach for service operation vessels (aka SOVs) could offer some additional efficiencies and cost-cutting opportunities for the offshore wind industry. That remains to be seen, though a study published last May by a research team from China and Australia suggests that SWATH SOVs may have some significant advantages.
“With the average operability greater than 95% in the study, SWATH has proven to be an attractive type of vessel against monohull whose operability may drop to 60% to 80% in case of unfavorable heading or transfer approach,” the team wrote.
In terms of fielding a SWATH SOV fleet of electric boats, that also remains to be seen. The research team noted an increase in fuel consumption for the SWATH SOV under high seas compared to the monohull vessel. Its possible that electrification could nullify could level the playing field in that regard.
More Offshore Wind For Japan
The Zephyrus electric boat venture may seem to be jumping the gun, considering that Japan’s offshore wind industry has yet to get into gear. However, the timing could be right as Japan moves into the floating wind turbine field.
Back in 2016, Japan’s NEDO (New Energy and Industrial Technology Development Organization) launched an R&D program for a floating wind turbine design that can withstand the same conditions needed to operate a fleet of electric boats, including typhoon-force winds as well as rough seas.
In 2020, the firms MODEC, Inc. Toyo Construction Co., Ltd. and Furukawa Electric Co., Ltd. signed a contract with NEDO to come up with a floating offshore wind design that cuts both capital and operating expenses. The basic idea is to replace the spread of catenary-type cables for mooring the floating platform with a more contained “tension leg platform” arrangement.
“TLP systems are expected to reduce the cost of power generation because the high stability of tension mooring to a seafloor foundation enables installation of large 15 MW-class wind turbines, which have the potential to become mainstream in the future, on compact floating platforms,” the partners explained in an update in January of 2022.
In addition to bottom line savings, the partners note that reducing the footprint of the mooring system also has follow-on benefits, including a reduced impact on fisheries and other marine operations.
Last summer survey work began in Ishikari Bay to determine if the new TLP design could be suitable there, so stay tuned for more on that.
Image: TLP floating offshore wind mooring compared to catenary mooring (courtesy of Furukawa)
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