Transitioning from traditional to alternative fuels

Transitioning from traditional to alternative fuels

Around 70,000 ships of the 90,000 that make up the global fleet could potentially adopt alternative propulsion solutions such as batteries, fuel cells, hydrogen or methanol fuel, and there is a huge market for these solutions to make a dent in the reduction of greenhouse gas (GHG) emissions from international shipping, says Anders Valland, research manager at SINTEF, one of Europe’s largest independent research organisations.

However, the challenge is that the other 20,000 or so ships, approximately 22.5 per cent of the 90,000, are the biggest emitters of GHG and are unfortunately less suited to alternative fuels and propulsion solutions. This is a real challenge and one of the major barriers to meeting the IMO’s 2050 target of reducing GHG emissions by at least 50 per cent compared with a 2008 baseline.

Shipping today consumes 250 million tons of fuel annually, with 75 per cent of fuel consumption from HFO, 23 per cent being distillates and 2 per cent being liquefied natural gas (LNG) and other alternative fuels. With shipping contributing 2-3 per cent of global GHG emissions and responsible for 12 per cent of local air emissions, there is a real pollution problem and a need to use alternative low carbon fuels, Mr Valland explained to us during a visit to the SINTEF facility in Trondheim.

Energy density of marine fuels

While there is no ‘perfect fuel’ or one size fits all solution to the reduction of greenhouse gases from global shipping, according to Mr Valland, the most widely applicable and low GHG emissions fuels are those in the green in figure 1, including methanol, ethanol, butane, LNG, LPG, and propane. He believes that while most ships can easily adopt such fuels, the issue is that many of these fuels have lower energy densities than HFO and MDO, requiring more space to provide the same energy. “It is more challenging for these fuels to bring the required energy for the operation of larger ships, and those that contribute the highest GHG emissions.”

Figure 1. Volumetric energy density vs gravimetric energy density. Figure courtesy of SINTEF

Liquid hydrogen from renewable energy is one of the cleanest fuels available today and has the potential to drastically cut GHG emissions from international shipping. However, it has a very low energy density and a large storage volume. DNV GL previously reported[2] that the energy density per mass of hydrogen is around three times more the energy density of HFO. The volumetric density of liquid hydrogen is around 7 per cent that of HFO, resulting in approximately five times the volume compared to the same energy stored in HFO.

According to Mr Valland, this has a lot of implications. “If you have a really low energy density fuel you will probably only be able to carry enough for one or maybe legs of your journey. This means coming into port with low fuel supply.”

Mr Valland went onto say that these large ships will fuel wherever the fuel oil is cheapest. The fuel supplier knows these ships are looking for the cheapest fuel. “If you change this and say that any vessel coming into port is going to have to refuel, you put this into a seller’s market rather than a buyer’s one. This has huge implications,” he explained.

Anders Valland, research manager at SINTEF speaking in Trondheim, Norway about the different options for GHG emissions reduction

“There are also consequences if ships have to refuel much more often than they do today. We already have congested harbours that will become even more congested. Fuel stations will pile up because of this.

“It is therefore challenging to see how fuels like hydrogen could be a solution for large commercial ships and directly replace their current fuel.”

An alternative is LNG, a fuel that contains no sulphur and emits very low levels of CO2. However, its release of unburned methane has led to widespread debate around LNG as a long-term sustainable fuel suited to achieving the IMO’s 2050 target. The release of methane, a GHG, is up to 30 times more than HFO and MGO, according to DNV GL. However, it has an energy density per mass of approximately 18 per cent higher than that of HFO[3], with a volumetric density only 43 per cent of HFO. This means that LNG is around twice the volume compared to the same energy stored in the form of HFO.

The emissions chain

While alternative low-carbon fuels like hydrogen offer the potential to make shipping cleaner by emitting lower levels of GHGs compared with conventional fuel oil when burned, it is wise to consider the sustainability of their production and associated emissions prior to use onboard ships. “Today, 80 per cent of hydrogen production is from natural gas. It means there really is a lot of carbon emissions,” stated Mr Valland.

“The overall GHG emissions of fuels depends on how you produce it. At the moment there are no zero GHG fuels on a well to wake basis, although work is in progress.”

Available fuel vs shipping’s energy needs

Figure 2 ‘Availability of fuel vs energy needs in shipping’ illustrates the current annual production of all fuels against the current percentage used for shipping. LNG for instance is produced in much higher quantity that what is currently used by shipping. In contrast, the production of methanol and hydrogen would need to increase to meet shipping’s energy needs.

Figure 2. Availability of fuel vs energy needs in shipping. Figure courtesy of SINTEF

 

During London International Shipping Week (LISW) held in September 2019, DNV GL experts stated that ammonia could claim up to 25 per cent of the fuel market by 2050. However, SINTEF research indicates that current global production would have to increase by at least 2.5. times to be able to reach this figure. “This is a real challenge,” said Mr Valland. “These fuels are energy intensive and more energy is needed to be put in that we get out.”

Testing a hydrogen fuel cell

In order to start addressing some of the challenges mentioned, SINTEF is working with Havyard to prepare the Havila Kystruten vessel for 3.2 MW hydrogen fuel cells – 3.5 tons of LH2, which according to Mr Valland is, “way beyond what anyone else has on the table.” The majority of fuel cell projects today are around 1MW.

The project has been granted NOK 104 million by from Pilot-E, the Research Council of Norway, Innovation Norway and Enova. The purpose of the project is to achieve five times longer zero-emission voyages than other existing or planned vessels.

“The vessel already has 6MW hours installed of batteries, which is a biggest installation of batteries to ships. This battery installation allows the vessel to sail in the Norwegian Word Heritage Fjords, but it doesn’t cover the hotel, only the propulsion.

“What we are trying to do with hydrogen is to sail the entire World Heritage Fjords area, around 3.5 hours sailing at 15 knots. We are also looking at how to increase endurance up to 10 hours. The longest leg on this vessel’s route is from Trondheim to a location far up north that takes 9 hours to sail. If we can do this on hydrogen then we have covered more than we need to.”

The next challenge for SINTEF is where to obtain the hydrogen. Mr Valland confirmed they are looking into this to ensure the production of the fuel has as little environmental impact as possible.

Currently, SINTEF is operating its own hybrid power systems laboratory to test liquid hydrogen fuel cells for maritime applications. The laboratory includes:

  • 2 x variable speed diesel generating sets
  • 2 x maritime batteries (50 kWh, 65 kWh)
  • 1 x supercapacitor cabinet
  • 2 x 30 kW hydrogen fuel cells
  • DC- and AC-grid capabilities
  • X-in-the-loop testing facilities
  • Coupled to SINTEF vessel simulator VeSim
  • Verification and validation of models, simulations
  • Demonstration of concepts

Mr Valland also confirmed that SINTEF has looked into compressed hydrogen as a possibility as liquid is more expensive but further research is needed to assess its viability as a fuel for marine propulsion.

References 

[2] DNV GL, June 2018, Assessment of selected  alternative fuels and technologies

[3] DNV GL, June 2018, Assessment of selected  alternative fuels and technologies

[4] DNV GL and SEA\LNG, July 2019, Comparison of alternative marine fuels