Palle Wedstrom, head of engines and propulsion department at Maersk Line

Marine Energy & Offshore Technology: Can you tell me about your history with the WHR system?

Palle Wedstrom: The first Waste Heat Recovery (WHR) system was in use in the early Sixties, we installed it on one of our tankers, Eli Maersk, in 1967. Maersk line were installing it on the A ships in the early Eighties. Today we have approximately 70 ships that have WHR installed and that will increase to 78 once the huge Triple-E ships are delivered. The Triple-E are under construction in Daewoo in Korea. We have been at the forefront of this technology for a long time.

MEOT: Can you describe your system?

PW: The WHR system installed on our ships usually consists of both a gas turbine, utilising pressurised exhaust gas as well as a steam turbine utilising steam from the exhaust gas boiler. These two turbines are then connected to a generator to generate electricity.

For the steam turbine we extract heat from the exhaust gas, but also from any other heat source on the ship and then we convert this into electric power. Because of the efficiency of the turbochargers we are able to bypass the turbocharger with a part of the exhaust and feed it to the gas turbine. We can put the electric power back onto the propeller, when an electrical shaft motor/generator is installed, to move the ship or we can use it for services on-board.

MEOT: Can the system be retrofitted?

PW: If you look at the system it takes up a substantial amount of space. It needs to be integrated with the boiler and main engine systems. It also needs power management to be integrated with the electrical system so it needs to be installed as a new build.

MEOT: Were there any other technology options?

PW: It is possible to take the exhaust gas and use it in the boiler system, but we saw the bigger opportunities offered by having combined turbines and combined cycle; it is more efficient. In general, if you look at WHR in marine we have it in many aspects of the ship’s operation such as producing freshwater by utilising the jacket water temperature. We used waste heat as a pre-heater for other media, so waste heat recovery in general is a well-known technology on board ships.

MEOT: As an operator what are the main benefits?

PW: As alternative to power produced by the WHR you will need to operate a diesel engine to generate electricity. The benefits are not only for the operator but for everyone. Using WHR you reduce the SOX, NOX and CO2 emissions. It’s good for the environment. I won’t say it’s free of charge, but you take out heat that is already available which reduces the emission and fuel consumption.

MEOT: Is there any loss of efficiency?

PW: We normally say that we gain up to eight per cent on the normal engine power by utilising the exhaust gas depending where we are on the operating profile of the ship – full speed or slow steaming. In certain operation profiles we have alternatives to gain more efficiency by dual speed strategy.

MEOT: What are the challenges with WHR?

PW: We are lucky that our marine crews are veryskilled. That is important because you need skilled crews to operate these types of technologies to ensure that you gain the full advantage of the systems. It would probably be easier for some operators simply to start a diesel gen-set and bypass the waste heat recovery.

MEOT: What are the technology drivers for WHR?

PW: It is both economic and environmental. At Maersk we have decided to focus very much on the environment. That forms part of the discussion as does the fuel cost and potential savings. They run in parallel. We are continuing to install the technology on our current new builds including the Triple-E that is a display of our belief in the technology.