Deepsea shipping sectors including tankers have been cautious about embracing battery technology, but landmark projects are now proving the case for on-board energy storage
The electric revolution is finally coming to tankers. The unbeatable efficiency of the two-stroke engine driving a large, slowly rotating propeller has previously discouraged owners of deepsea tonnage from looking at batteries. Energy storage offers the most obvious benefits for vessels with a widely varying operating profile – such as shortsea or coastal ships – rather than those tending towards a steady, long-range speed. But some pioneering projects could prove that even big tankers can benefit from battery installations.
Two 17,500 dwt chemical tankers for Stenersen, the most recent delivered in January, are understood to be the first tankers to deploy batteries as part of a power and propulsion package that also incorporates shaft generators. Sten Tor and Sten Odin operate entirely within the Baltic and North Sea emission control areas, so reducing SOx emissions to 0.1% – lower than the impending 0.5% global cap – was a main design requirement.
“Batteries alone do not solve the problem, but they enable the solution”
The Corvus battery packs are used as a spinning reserve when the vessels are manoeuvring into and out of port. They also replace one auxiliary engine during discharge operations. A 400 kW shore power connection means that auxiliaries can be switched off when the ships are idling quayside or in drydock, with the battery meaning that there is no interruption in power between turning off the engines and connecting to shore electricity.
The project has raised interest from counterparts in the chemical tanker sector. In March one of the biggest operators, Odfjell, joined the technology cluster NCE Maritime CleanTech in Bergen to explore emerging sustainable solutions. Although it is too early for the company to lay out concrete plans, batteries are high on the list.
“Batteries are something that we have ruled out for our fleet until now, but the technology is becoming more efficient,” says Odfjell vice president technology Erik Hjortland. “We would like to learn more about the cluster companies’ experiences with batteries. We are also looking into alternative fuels, such as LNG and hydrogen.”
Beyond the chemical sector, an innovative use of batteries is planned for four Teekay Offshore shuttle tankers being built by Samsung Heavy Industries (SHI) – including one, the Aurora Spirit, launched in late March. The vessels feature LNG-burning engines that are also capable of using the volatile organic compounds emitted by the crude oil cargo. The power distribution system supplied by Wärtsilä also employs batteries to further reduce fuel costs by peak-load shaving. As a result, total annual energy consumption is expected to be reduced from 110 GWh for a conventional vessel to 75 GWh.
Teekay’s 130,000 dwt newbuilds are not only the first tankers to deploy batteries for propulsion, but the first vessels of this size in any segment to do so. The batteries will handle dynamic load variations while engines operate at a stable load, meaning that additional generators do not need to be started to handle transient load variations.
The Teekay concept could mark a tipping point in the introduction of hybrid propulsion to the tanker and other deepsea segments. It has already inspired Wärtsilä and SHI to launch a project aimed at developing hybrid solutions for the tanker and LNG carrier markets.
According to Wärtsilä sales director, merchant segment Stein Thorsager, the Teekay project had encouraged SHI’s interest in hybrid propulsion. “They see the advantage of using batteries as part of the energy demand on board and strongly believe this will be of value for other tankers and gas carriers,” he says.
SHI is also interested in entering the marine market with its own batteries. It will be able to use Wärtsilä’s hybrid centre in Trieste – a facility that enables the full-scale testing of hybrid propulsion arrangements – to explore the best battery properties and specifications for marine use.
A case for batteries
Tanker and gas carrier propulsion is usually provided by two-stroke engines, with medium-speed engines catering for on-board power demand. Batteries can be used most easily to replace auxiliary engines and tackle peaks in energy demand. But the partnership will explore propulsion applications too.
“Batteries are something that we have ruled out for our fleet until now, but the technology is becoming more efficient”
“We believe in electric propulsion for some of the smaller tankers and LNG carriers,” says Mr Thorsager. “In the future you could see a row of generators on one deck with an electric propulsion motor down in the hull connected to the propeller shaft. We already see interest in such concepts from shipowners and charterers who are looking at all options to reduce their emissions to meet IMO targets.”
The partnership could also extend to retrofit hybrid solutions. Wärtsilä has already developed containerised retrofit solutions comprising batteries, switchboards and controls, mainly deployed on offshore vessels. Solutions could be developed for larger vessels.
The partnership is not entirely driven by speculation and an interest in battery sales. DNV GL reports seeing an increase in the number of battery queries being raised by tanker owners at an advisory, pre-build stage. While admitting that many of these projects will not reach fruition, maritime systems leader Sondre Henningsgård confirms the growing curiosity.
“In tankers we see a lot of interest in batteries, although owners don’t necessarily know too much about it,” he says. “All projects today begin with a discussion about propulsion, including diesel-electric, LNG and batteries, and more owners are seeing that actually a combination of these may work.”
From the class perspective, safety is a priority. But there are not automatically concerns about batteries on tankers, says Mr Henningsgård. “Catching fire is the key safety concern and the consequence may be bigger on a tanker than a ferry. You will have bigger limitations on where you can locate batteries. But the batteries should not be a safety concern once their location is chosen.”
DNV GL recently concluded a project focused on the long-term benefits of lithium-ion battery systems for auxiliary power management on board smaller-sized oil or product tankers of around 17,000 dwt – similar in size to the breakthrough Stenersen ships. The project partners – oil major Total, ship designer FKAB Marine Design, battery manufacturer Saft, shipowner Viken Shipping, and ship operator Wallem Shipmanagement – used reference data from six sister ships and identified four possible hybrid auxiliary power system configurations. Across several different purposes for batteries, all hybrid configurations investigated offered better financial returns over a 20-year period than the conventional base scenario.
“In the future you could see a row of generators on one deck with an electric propulsion motor down in the hull connected to the propeller shaft”
Mr Henningsgård notes that the different operational profiles of coastal and deepsea tankers still make a difference to the viability of battery uptake for the time being. Smaller tankers, which do their own manoeuvring rather than using tugs close to port, have different requirements for redundancy. But he argues that even big vessels can benefit from using batteries as a spinning reserve, or to reduce the number of auxiliary engines.
“I don’t think we will see VLCCs using batteries to support their main propulsion,” he says. “You can’t beat the two-stroke and large propeller. But with the 2050 emission targets coming, that option may not be available. Then what? Batteries are likely to have a role. For example, one of the potential clean fuel options is hydrogen with fuel cells. If you use fuel cells you will need batteries to store the electricity generated. It will be similar if big vessels start looking at wind propulsion. Batteries alone do not solve the problem, but they enable the solution.”
Emissions-free propulsion
While the designers of bigger tankers begin to consider hybrid battery propulsion, on the smaller, coastal segment attention is turning towards the prospect of purely electric tankers. Asahi Tanker Co and Exeno-Yamamizu Corporation Tokyo have developed a new domestic shipping tanker design that will feature emission-free battery propulsion.
According to Asahi Tanker Co innovation and business development manager Takeyoshi Ichikawa, Japan’s 5,000-plus domestic fleet of coastal vessels will need replacing in the next decade. The aim of the current project is to replace the current fleet of bunker tankers operating in Tokyo Bay, with the partners hoping to build the first vessel by the end of 2020. The companies are also launching a feasibility study with electricity providers and trading companies on installing power supply facilities in ports.
“All projects today begin with a discussion about propulsion, including diesel-electric, LNG and batteries”
The e5 bunker tanker is an all-electric, lithium battery concept from naval architect Groot Ship Design. The 60-m long vessel will have a cargo tank capacity of 1,300 m3. ClassNK has been appointed to advise on the ship design and electric propulsion. The initial design shows a propulsion power demand of 830 kW across two azimuth thrusters and a bow thruster. The designers have yet to size the batteries.
The Asahi-Exeno 'e5' bunker vessel could be the first all-electric tanker in service by the end of 2020
It has been less than a year since Sten Odin, the first battery-equipped tanker, was delivered. There are already signs that the solution will gain a far wider acceptance in the segment. It will still be a while before bigger tankers look to batteries for anything beyond auxiliary roles; it will be far longer before all-electric deepsea tankers are viable. But the level of interest around batteries suggests uptake may be quicker than previously expected.
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