Exploring new avenues for gas turbines

Outside of the naval sector the role of gas turbines in vessel propulsion is shrinking. Dual-fuel diesel-electric configurations and more efficient gas-burning two-stroke engines have dented the uptake of gas and steam turbines in both the gas carrier and cruise ship segments. But there are a handful of new projects, concepts and technology upgrades that suggest the technology could yet experience a marine renaissance.

It is 13 years since the last turbine-powered cruise ship, Noordam, was delivered from Fincantieri’s Marghera shipyard in Italy, in February 2006. Boasting one GE LM2500 gas turbine and generator working in combination with four diesel gensets, the Holland America vessel took the turbine-powered cruise fleet up to 11, according to data provider VesselsValue.

The mainstay of turbine propulsion in shipping has been the gas carrier sector, with 228 active vessels using either steam turbines or a combination of gas and steam or gas and diesel. But here too activity has shrunk of late: since 2010 just 15 such vessels have been built, compared to 147 between 2002 and 2009.

Will Holland America's Noordam be the last cruise ship to be powered by turbines?

After two years in which no turbine-powered LNG carriers were built, in 2014 and 2015, there has been a modest revival. Proving that the concept of turbine propulsion is not dead in the gas carrier segment, Mitsubishi Heavy Industries has named a fifth gas carrier to rely on its unique hybrid arrangement of steam turbines and gas engines (STaGE) driving electric propulsion.

Earlier this year the 177,000 m³ Marvel Crane was delivered to Mitsui & Co, which will deploy the vessel to serve the Cameron LNG Project in the US. It is the latest in Mitsubishi Heavy Industries’ (MHI) Sayaringo STaGE series of LNG carriers which began with the Diamond Gas Orchid last year.

The STaGE propulsion concept uses an asymmetrical configuration for twin shaftlines. The starboard line is driven by three Wärtsilä medium-speed, dual-fuel engines powering an electrical propulsion motor. The port-side shaftline is driven by a steam turbine developed by MHI, the UST (ultra-steam turbine plant), which uses waste heat from engine exhaust and cooling water. This means that very little fuel is required to power the turbine.

According to MHI public affairs spokesman Genki Ono, the company is contractually prevented from disclosing the total installed power of the vessel. On the starboard side, the Wärtsilä 6L50DF engines in diesel-electric applications each have an output of 5,700kWe at 500 rpm and 5,850kWe at 514 rpm.

“By effectively using the exhaust heat to generate electricity to serve as auxiliary power for the ship, the system contributes to reducing carbon dioxide and fuel for the generator engines”

The vessel, one of four remaining on order, also features a modified Moss spherical that is designed to expand the ship's capacity without increasing its width, allowing it to pass through the new Panama Canal.

MHI received the order for the new vessel through MI LNG Co, a joint venture for the design and sale of LNG carriers established by MHI and Imabari Shipbuilding.

The combination of turbines with waste heat recovery is not confined to MHI’s gas carriers. In January, Japanese shipowner K Line installed an experimental binary cycle waste heat recovery system (WHRS) on 91,000 m³ coal carrier Corona Youthful.

The system, developed by Kobe Steel, can generate 100kW of electricity from main engine exhaust heat. The three-year pilot study aims to verify the system’s durability and performance under operating conditions.

Kobe Steel began developing a binary cycle system for ships in 2014, following earlier land-based projects. A sea trial using a prototype was conducted in 2016.

The system, which can be used with main engines of more than 5MW, has received approval from class societies ClassNK, Lloyd’s Register and DNV GL.

Binary cycle power generation produces electricity by using a steam turbine. Low-temperature heat sources, including warm water, low-pressure steam or air, are used to vaporise a substance with a low boiling point, which drives the turbine.

Kobe Steel notes that the novel WHRS is designed to help ships achieve the greenhouse gas emissions reductions that IMO is hoping to achieve. “By effectively using the exhaust heat to generate electricity to serve as auxiliary power for the ship, the system contributes to reducing carbon dioxide and fuel for the generator engines,” the company says.

Micro turbines

StAGE is not the only hybrid development in turbines. In late 2018, Dutch maritime system integrator RH Marine partnered with Feadship, Seven Turbine Power and Boskalis to introduce a micro turbine that is aimed to function as part of a hybrid power configuration on smaller vessels. The solution consists of a DC65-D Marine turbine generator, a 65kW turbine-generator set that can run on a variety of fuels, such as marine gas oil, and delivers direct current to the grid, based on a Capstone C65 micro turbine.

In combination with waste heat recovery, the potential efficiency of the micro turbine matches that of a conventional diesel generator. The compact design means that it would be possible to stack the units in parallel in a rack to deliver sufficient power. The partners claim it produces extremely low emissions, operates quietly without vibrations and requires very little maintenance.

RH Marine technical product manager Michiel Post says: “The DC power output of the micro turbine is perfectly suited to a hybrid-battery-based solution. It is highly efficient thanks to the lack of an AC to DC conversion step and the waste heat recovery functionality.”

The micro turbine has received approval in principle by Lloyd’s Register.

There are further partnerships that suggest there is more to come in the gas turbine sector – including one collaboration involving one of the biggest builders of both naval and cruise vessels, Fincantieri. Italian investment bank CDP Group has signed an agreement with Fincantieri and gas utility company – both companies in which CDP holds stakes – to explore energy efficiency technologies in the marine sector.

CDP Group CEO Fabrizio Palermo says: “Fincantieri and Snam will share their knowledge and technical expertise to make a concrete contribution to the competitiveness of maritime transport, a key sector for both the Italian and wider European economies.”

A co-operation agreement between the two companies commits to identifying, developing and implementing medium-term strategic projects focused on innovation and energy efficiency. The partnership is driven by Italy’s Integrated National Energy and Climate Plan, which includes proposals to develop LNG fuelling infrastructure at Italian ports.

Ports and coastal areas are a focus area of Fincantieri’s and Snam’s joint investigations, with projects examining the construction of infrastructure for the supply of LNG and alternative energy sources in maritime transport. However, new technologies to take advantage of LNG and other fuels will also be explored. Among the technologies highlighted – drawing on Fincantieri’s significant experience on deploying gas turbines in cruise ships and naval vessels – are LNG-fuelled turbines.

Also on the list for investigation are containment and management systems for methane (in both liquid and gaseous states) and innovative energy sources, including hydrogen and fuel cells. The plan will allow Fincantieri to leverage its shipbuilding experience while tapping Snam’s utility expertise in LNG and hydrogen to explore their use as a marine fuel. And turbines have been identified as a key path.

The emerging interest in new fuels and hybrid technologies could, it seems, be offering a new avenue of development for a technology that was beginning to lose ground in the commercial sector.

Turbine-powered LNG carrier newbuilds, 2002-2018
Year	Vessels built
2002	11
2003	13
2004	19
2005	17
2006	26
2007	26
2008	21
2009	14
2010	5
2011	4
2012	1
2013	1
2014	0
2015	0
2016	1
2017	1
2018	2
Source: VesselsValue