Inventive owners are finding that battery retrofits can boost efficiency and reduce emissions, even for modern gas-fuelled vessels
Four years ago, platform supply vessel (PSV) Harvey Energy became the first US ship fuelled by LNG when it went on charter to Shell in the Gulf of Mexico. Harvey Energy will soon make history once again as the first US-flag, dual-fuel, battery hybrid-powered PSV, after a retrofit at New Orleans-based Harvey Gulf International Marine’s shipyard.
“The vessel can already outperform any PSV in the [US Gulf of Mexico] today in terms of speed, emissions, cost for fuel and fuel burn,” says Harvey Gulf International Marine chief executive Shane Guidry. “We want to continue to bring lower emissions and lower fuel cost savings to our customers.”
Harvey Gulf International Marine (HGIM) has contracted Wärtsilä to supply an energy storage system, energy management system, transformer and drive, all mounted inside a single container. Wärtsilä will deliver its battery-hybrid module to HGIM’s Gulf Coast Shipyard Group (GCSG) in Gulfport, Mississippi in December.
According to Wärtsilä, installing a 1,450-kW battery module will reduce exhaust emissions, fuel consumption and noise levels. Overall fuel costs are estimated to be reduced by 10-20%. Additionally, Harvey Energy will be able to sail to and from Port Fourchon, Louisiana on electric power only, using its battery at the dock to lower noise and emissions. The retrofit should also result in less running hours on the engines, reducing maintenance costs.
Harvey Energy was one of a series of six PSVs built at GCSG to a Vard 1 311 design from Vard Marine (formerly STX Marine). It has an overall length of 92 m, beam of 19.5 m, with a clear deck area of 974 m2 and dynamic positioning class 2 capability. Five of the PSVs were delivered for contracts in the US Gulf of Mexico.
"Most vessel projects begin with discussion on propulsion, including LNG and batteries. Owners are familiar with these but often aren't always aware that they can be combined"
Retrofitting Harvey Energy is only the start of the transformation of HGIM’s fleet, says Mr Guidry. All of HGIM’s LNG-fuelled PSVs will have battery-hybrid power installed. An order has already been signed for the next vessel, Harvey Supporter.
There are at least two clear justifications for retrofitting batteries on to dual-fuelled ships. The first is about the clear efficiency gains. LNG can reduce SOx and NOx emissions to virtually zero and reduce CO2 emissions by around 20% compared to diesel. Batteries can be added to that to further reduce fuel consumption and therefore emissions.
They also offer on-demand power with fast dynamic response – crucial for the kind of DP work that is the staple of these vessels. Further, batteries used for peak shaving make extra sense for LNG engines, which need to be operated with consideration for optimal loading due to the careful control of fuel-air mix required to avoid knocking or misfiring.
This is not the first time Wärtsilä has worked with HGIM. Each of the owner’s LNG-fuelled PSVs have three Wärtsilä 6L34DF dual-fuel gensets that generate 7.5 MW of power and Wärtsilä’s LNGPac fuel storage and supply system, which can hold 295,000 litres of LNG. Integrating the existing Wärtsilä power distribution and management and integrated automation systems will be part of the retrofit project.
Mr Guidry says that this existing relationship made Wärtsilä the natural choice for a partner on the battery-hybrid retrofit: with Wärtsilä’s support, none of the five LNG-fuelled PSVs in Harvey Gulf’s fleet experienced unscheduled downtime. “We believe our mutual project will have a considerable impact in the market and will further the environmental drive towards sustainable solutions in the offshore market space,” explains Mr Guidry.
He also sees advantages of battery power in dynamic positioning (DP) operations. The retrofitted vessels will be able to position in much harsher environments and offload below-deck cargo 40% faster, he says. The ability to operate on battery power will also assist manoeuvrability during these operations. As compared with combustion engines, batteries respond well to the rapid load changes needed for positioning in rough sea conditions.
Harvey Energy is not the first gas-fuelled vessel to undergo a battery retrofit with Wärtsilä. Most recently, Norway-based Eidesvik Offshore replaced one of the dual-fuel engines in PSV Viking Princess with a Wärtsilä hybrid power module. This points to an emerging trend in gas-fuelled vessels being retrofitted with batteries.
DNV GL principal engineer Sverre Eriksen confirms that hybrid vessels are becoming more popular. “Most vessel projects today begin with a discussion on propulsion including LNG and batteries. Owners are familiar with these but often aren't always aware that they can be combined. We are seeing increased interest.”
A recent DNV GL collaboration with shipyard group Keppel Offshore & Marine is a case in point. The companies have agreed to co-operate to promote LNG as a marine fuel. While the partnership has begun with the design of LNG bunker vessels, there is a specific reference to “LNG-related assets employing battery and hybrid technologies”.
Another reason for adding batteries to an LNG-fuelled offshore ship reflects the shifting demands of oil majors. Since the first round of dual-fuelled vessels were built for the Norwegian offshore market pre-2015, the demand for LNG has grown globally, while its environmental benefits are increasingly questioned, principally because of methane slip at production and across the supply chain. Big oil charterers are now looking to battery solutions to both cut fuel bills and slash emissions on the ships they hire.
DNV GL confirms that the growth rate for battery-hybrid and fully electric vessels is now greater than that of LNG-fuelled vessels. “The technology has advanced rapidly in just a few years, and there is mounting data to support the benefit-case for the use of energy storage,” says technology and LNG business development director Anthony Teo. “The success and safety of these projects, however, depends on understanding the key technical limitations, selecting the optimal battery technologies, and integrating them into the platforms and infrastructure network.”
Those complexities were front of mind for offshore vessel owner Seacor Marine, the operator of the first hybrid-powered vessels in the Gulf of Mexico. The company completed the retrofit of its first OSV, Seacor Maya, to a hybrid diesel-electric solution last year. The battery system developed with system integrator Kongsberg Maritime and battery maker Corvus, is held in a 28-tonne, 20-foot container. It keeps generators from running more than necessary and at their sweet spot: between 75% and 80% of the maximum continuous rating. At higher power demands, the batteries are supplying power, and at lower power demands the generators are recharging the batteries, enabling the generators to run constantly near or at their operational load sweet spot.
“The success and safety of these projects depends on understanding the key technical limitations, selecting the optimal battery technologies, and integrating them into the platforms and infrastructure network”
The vessel was converted at Bollinger Shipyards in Morgan City, Louisiana, followed by sea trials in May 2018. The integration was completed within 90 days, reducing the vessel’s average fuel consumption by 20%. As a result of this performance, Seacor adapted three more vessels for service with plans to adapt an additional six. The programme won Seacor recognition as Shipowner of the Year at the 2019 Offshore Support Journal Conference & Awards in London earlier this year.
Seacor’s investment makes up a large proportion of the hybrid vessel projects scheduled for 2019. But it is by no means the only operator planning to harness battery power. Whether combined with dual-fuel or conventional diesel engines, expect energy storage orders to continue to mount as more offshore owners are convinced of its merits.
Remote engine overhaul refreshes diving support vessel
One of the world’s biggest diving support vessels has re-entered service after an engine overhaul that included having key components tested and repaired at a remote workshop.
A remote engine overhaul has prepared advanced dive support vessel Seven Atlantic for extended service
The engines and turbochargers on the 140 m-long Seven Atlantic, owned by Subsea 7, were serviced 10 years after the vessel was built, with Royston Diesel completing the work. Seven Atlantic is powered by six 3,360 kW Wärtsilä W7L32 engines running on marine gas oil, each paired to a 3,360 kVA Van Kaick generator. The diesel-electric arrangement drives three 2,950 kW stern azimuth thrusters, two 2,400 kW retractable bow azimuth thrusters and a 2,200 kW bow tunnel thruster.
One of the engines was disassembled to install new cylinder heads, air start valves, indicator cocks, injectors, and cylinder seals. Relief valves, pistons and conrods, cylinder liners, bearing blocks, crankshaft and turbocharger were sent to UK headquartered Royston’s Newcastle workshop for checking and essential repair work, before being returned ahead of the final reassembly and inspection of the engine.
Engineers also overhauled the turbocharger on another engine. The NA297 Napier turbochargers from both engines were removed, stripped, cleaned, inspected and balanced at Royston’s dedicated turbocharger facility. Following the service, incremental load testing in line with the engine manufacturer’s specification was also completed by engineers.
Royston service manager Shawn Doering said that the company’s experience with the engine and vessel type ensured a quick re-entry into service. Shipowners can save up to 30% on the cost of overhauls by using third-party service providers instead of OEM services, he said.
Seven Atlantic has a 24-person saturation diving system as well as a 120-tonne heave compensated crane. The vessel’s DP3 system is designed to support diving operations in wave heights of up to 4.5 m. This requirement led to an unusual propulsion layout, with three engine rooms housing two diesel generator sets and three switchboards each.