Some of the world’s biggest container ships are now being built, and in one breakthrough case retrofitted, with dual-fuel engines as two-stroke technology providers seek alternative ways to add value
The barriers to the uptake of LNG as a marine fuel are more commercial than technical. But those barriers are being eroded, partly as the cost of gas-fuelled technology falls compared to other environmental compliance options, but also as a difficult market forces shipyards to reduce the premium they charge for such vessels. These are the finding from a study launched early this year, which projected rapid returns on investment for a large newbuild container ship fitted with dual-fuel technology.
The study was conducted by simulation and analytics expert Opsiana for the SEA\LNG consortium, which aims to persuade shipowners of the commercial case for gas fuel in shipping. The researchers analysed the case of a newbuild, 14,000-TEU container vessel operating on an Asia-US West Coast liner route. The report compares six fuel pricing scenarios and, according to SEA\LNG chairman Peter Keller, challenges commonly-held assumptions about the economic performance of LNG bunkers.
He says: “The study unequivocally shows that for this vessel type, on this trade route, LNG as a marine fuel delivers the best return on investment on a net present value basis over a conservative 10-year horizon, with fast payback periods ranging from one to two years.”
The cost of LNG-burning two-stroke engine technology has fallen both relatively and absolutely in recent years. In relative terms, the cost premium for LNG compared to conventionally-fuelled vessels has become more tolerable given the expense of complying with IMO’s global sulphur cap. Conventional ships will comply by using very low-sulphur fuel oil or marine diesel oil, raising operational costs. For ships using exhaust gas cleaning systems and continuing to burn heavy oil, fuel may be cheaper, but LNG is cheaper still.
“LNG as a marine fuel delivers the best return on investment on a net present value basis over a conservative 10-year horizon, with fast payback periods ranging from one to two years”
The absolute cost of dual-fuel technology is also falling. The Opsiana report attributes this to the lower premium that shipbuilders put on gas-fuelled vessels due to the slowdown in shipbuilding. But it is also a result of efforts by engine designers to simplify their systems.
One of the biggest gas-fuelled ship orders in recent years is a case in point. CMA CGM’s nine 22,000-TEU vessels to be delivered in 2020 and 2021 will each be powered by the biggest dual-fuel marine two-stroke engine ever built – WinGD’s 12-cylinder, 920-mm bore X92DF, delivering 63,840 kW at 80 rpm. The engines include several design features that reduce size, weight, complexity and maintenance demands.
The X92DF destined for CMA CGM's ultra-large container ships features cost-cutting new technologies
These engines will be the first to incorporate a new engine control system, MK-E cylinder lube pumps, as well as being the first of their size to deploy an integrated gas pressure regulation system. All the design features offer significant benefits in terms of reduced footprint, complexity and maintenance.
Among the innovations is a new system that brings the function of the gas valve unit (GVU) within the engines, easing installation and improving integration. The role of the GVU is to regulate the pressure of gas from the fuel gas supply system to the engine and to shut down supply quickly and safely. GVUs usually sit in the engineroom, although they can also be housed in a dedicated room. The new integrated gas pressure regulator (iGPR) incorporates that functionality within the X-DF engine.
The new concept results in a space saving in the engineroom as well as a weight saving (of around 1,100 kg compared to the GVU-equipped alternative design in the debut case), easing installation. But according to WinGD manager, marketing and application, Daniel Strödecke, the impact on control and communication is more significant than the weight and space savings.
“Rather than communicating between the GVU and engine via an external system, now there is just internal communication within the engine,” he says.
Integration is improved in other areas too. Interfaces with other equipment are simplified and more of the engine set-up can be completed by the engine builder rather than the shipyards. Mr Strödecke notes that the iGPR design enables the installation of significantly smaller ventilation air fans, for example, and gives WinGD more control over the design and construction in general.
“If we want to optimise the pressure control valve it can be done without liaising with a third party,” he says.
The system has been introduced on the first X52DF engines, destined for two 125,000-DWT shuttle tankers being built for AET by Samsung Heavy Industries. It will also be introduced on the X92DF engines and will eventually be rolled out across WinGD’s X-DF portfolio.
WinGD will also debut its Mk-E cylinder lubrication pumps on the X92DF engines. The pumps inject precise amounts of oil onto the cylinder liners at tightly controlled times to lubricate the main pistons and cylinders.
The new pump has improved priming, both internally and with a button-operated venting valve. It has 45% fewer parts than its predecessor, making it quicker to assemble and install on the engine. As a result, the pump’s weight is reduced by 40% and production costs fall by around 35%. The new pump design has also allowed WinGD to improve the configuration of the outlets, simplifying installation and service on the engine.
The CMA CGM vessels are among the first, but they are not the only container ships to take advantage of cost-saving dual-fuel designs. In March, Singapore-based Eastern Pacific Shipping ordered 11 15,000-TEU ships to be built at Hyundai Samho Heavy Industries. Six of the units will feature LNG-burning engines from MAN Energy Solutions. The MAN B&W 11G90ME-GI dual-fuel engines are scheduled for delivery between 2020-2022.
The engines will feature MAN’s new pump vaporiser unit (PVU) – a low-cost pump unit for pressurising and supplying LNG to the engines. The PVU is designed to pressurise and vaporise the required fuel to the pressure and temperature required by the ME-GI engine. The gas pressure is controlled by the hydraulic flow to the pump. The separate control of the three pump heads provides full redundancy and is secured by a control system with safety functions and a high degree of integration with the ME-GI engine.
MAN's pump vaporiser unit uses exhaust valve actuators to control fuel gas supply pumps
MAN Energy Solutions senior vice president, head of two-stroke business Bjarne Foldager says: “Apart from the reduced cost and weight, ordering both PVU and engine from the same designer provides many other advantages, including easier integration and straightforward installation.”
The PVU is an ingenious simplification of the dual-fuel auxiliary machinery, using pumps driven by the engine’s exhaust valve actuator to compress fuel before vaporising it for injection. Although the Eastern Pacific Shipping order is the biggest order to include the PVU, the system will make its debut on a more noteworthy vessel. Hamburg-based liner company Hapag-Lloyd’s 15,000-TEU vessel Sajir will become the biggest container ship so far to retrofit dual-fuel LNG engines, with the PVU included in the order.
“Hapag-Lloyd’s 15,000-TEU vessel Sajir will become the biggest container ship so far to retrofit dual-fuel LNG engines”
The company has signed a contract with Hudong Zhonghua Shipbuilding (Group) Co to carry out the conversion at Huarun Dadong Dockyard in Shanghai. The vessel’s 54.9 MW MAN B&W 9S90MEC10 engine will be converted to MAN Energy Solutions’ dual-fuelled ME-GI engine concept. Hapag-Lloyd plans to primarily use LNG, with low-sulphur fuel oil as a back-up option.
“By carrying out this unprecedented pilot, we hope to learn for the future and to pave the way for large ships to be retrofitted to use this alternative fuel,” says Hapag-Lloyd managing director fleet management Richard von Berlepsch.
Sajir is one of 17 container ships built as ‘LNG ready’ by United Arab Shipping Co before it was acquired by Hapag-Lloyd. Hapag-Lloyd first revealed its plan to convert one of the LNG-ready vessels when it detailed its compliance strategy for the 2020 sulphur cap last year.
Hapag-Lloyd's first LNG retrofit candidate will feature a 6,700 m3 gas fuel tank, bunkering twice per round trip. The smaller tank size compared to the 18,600 m3 tanks on CMA CGM's large container ships points to greater certainty about bunkering in Asia, as well as space constraints on Sajir, which was designed LNG-ready six years ago.
The ship is already highly efficient, running at -60% to the EEDI reference line thanks to modern efficiency features, including waste heat recovery. Another feature likely to remain is the power take-off (PTO). A recent case study by MAN Energy Solutions highlights how a PTO can optimise energy efficiency by generating electricity from the main engine. Auxiliaries will also be dual-fuel, the line has confirmed.
After conversion, the 54.9 MW MAN B&W 9S90MEC10 will earn the -GI suffix that denotes MAN Energy Solutions' high-pressure, diesel cycle, dual-fuelled engines.
A successful retrofit for a vessel of Sajir’s size would represent a significant milestone for the advancement of LNG as a marine fuel. The high cost of retrofitting has been seen as a barrier to uptake; following the Sajir contract, MAN believes conversions are becoming viable for more vessels and container ships built within the past five years are now seen as good candidates.
MAN head of sales, retrofit projects Klaus Rasmussen notes that the company has been able to refine its conversion strategies as the number of projects has grown. The age range for suitable candidates is not limited by the need for payback time, he explains, but by the fact that vessels must have modern ME-C engines. These feature the electronic controls needed to govern fuel injection and exhaust valve timings on gas engines.
Mr Rasmussen acknowledges that Hapag-Lloyd has paid a higher cost for works on Sajir due to it being the first of its kind. Any further retrofits would be cheaper as a result of this work, he says. Hapag-Lloyd has put the cost of LNG conversions at US$25M-30M.
Further conversions would also offer economies of scale on LNG fuel. The membrane tank, enough for one voyage between Europe and Asia, is the most significant element of the 90-day retrofit. The engine conversion could be completed in around five weeks; the remaining two months will be devoted to installing the tank and the complicated steelwork supporting it.
At 368 m in length and weighing 149,400 DWT, Sajir is the biggest ship ever to be converted for dual-fuel operation. Along with the big new container ships ordered by CMA CGM and Eastern Pacific Shipping, they showcase how improving dual-fuel technology – and particularly the prospect of dramatic fuel cost savings – is helping to bring LNG fuel to the attention of owners of ever bigger vessels.