STORY Commercial Marine

"The gas engines purr quietly like kittens"

Posted on September 29, 2023 by Lucie Maluck

It has something of a premiere atmosphere: Europe's first inland ferry powered by a high-speed pure gas engine is about to go into operation on Lake Constance. It is still being diligently tested.
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Oli Hermann pushes the driving lever all the way forward. Very slowly, then faster and faster, the ferry starts moving. Only a few weeks ago it was christened Richmond. Now she is about to be officially commissioned and the final preparations are underway on board. Oli Hermann is the captain on board. Against the enchanting backdrop of Lake Constance and the Swiss Alps in the background, he is testing the so-called "manoeuvre of the last moment". He accelerates the ferry to its maximum speed of 26 km/h (14 knots) and then brakes abruptly. Within 32 seconds and after about 140 metres, the Richmond comes to a halt, without lurching, almost without jerking. Test passed - the captain satisfied.
Oli Hermann is captain of the Richmond and tests it down to the smallest detail before it is put into service.

World's first high-speed gas engine with dynamic acceleration

The Richmond is the first inland ferry in the world to be powered by high-speed, gas-only engines. The two eight-cylinder mtu engines of the 4000 series each have 746 kilowatts of power. They fall below the nitrogen oxide limits of the current IMO III emissions directive even without exhaust gas aftertreatment, emit no sulphur oxides and the particulate mass is below the detection limit. "A real milestone in the development towards clean and low-emission transport solutions" is what parliamentary state secretary Michael Theurer called the ship at its christening. But the Stadtwerke want more: "In the future, we want to run the ship on bio-LNG and thus be completely climate-neutral," emphasises Christoph Witte, technical manager of the Stadtwerke ferries.

Oli Hermann in the driver's cab of the Richmond is not thinking about that right now. He is really looking forward to the day when passengers can finally travel on the ferry. He has spent many months putting the ferry through its paces - including the propulsion system. He emphasises that the main work was done by his colleagues Timo Bakaric and Dieter Ehinger. While Oli Hermann was up on the bridge enjoying the Lake Constance panorama, the two were mostly to be found in the engine room.  

Timo Bakaric (left) and Dieter Ehinger (right) are the technical specialists on board. They installed the mtu drive system and commissioned it together with Rolls-Royce customer service.

Quieter and with less vibration than a diesel engine

There, below deck, it is not dark, but it is cramped. Shiny silver insulation hangs all over the wall. It is warm. Nevertheless, you feel at ease, because Timo Bakaric and Dieter Ehinger spread an infectious cheerfulness. They both love the sound of the engines - the gas engine is significantly quieter than a comparable diesel engine. mtu diesel engines are familiar to them, as all five ferries of the Constance public utility company that shuttle between Meersburg and Constance around the clock are powered by them.  

The gas processing, the heating and cooling systems, the heat recovery, the nitrogen processing, the alarm systems - the two had to understand all that. Of course there were briefings from the respective suppliers, "but they are gone again at some point, and the questions always come afterwards," says Dieter Ehinger.  

They quickly understood the mtu drive system from Rolls-Royce, also thanks to the good support of the Rolls-Royce contact persons. "We already know each other from previous projects, so it worked out well again this time," says Ehinger. They also visited the Netherlands, where two ferries are already running with mtu gas engines. "The good experiences of our colleagues there motivated us to set up our system," says Ehinger. But how does the system work in detail?  

The mtu gas drive system in detail

First there is the fuel tank: there are two of them on board, one for each engine. Both are white, round and seven metres long. They can be reached via a lock and only if you are equipped with a gas meter. Better safe than sorry. These two tanks each hold 18 cubic metres of LNG - enough to run the ferry 24 hours a day for a week. The LNG is cooled down to minus 160 degrees Celsius so that it remains liquid.  

The LNG is stored in a seven-metre-long and two-metre-high tank surrounded by a ten-centimetre-thick vacuum layer.

Only when it is to be used does the so-called Gas Processing Unit (GPU) bring it back into a gaseous state. The gas then flows on into the two separate engine rooms. In front of each engine, the so-called Gas Regulation Unit (GRU), which is already part of the mtu system, ensures the right pressure. From there, the gas finally reaches the two engines. These thus supply the energy for the two Voith-Schneider propellers and the generators. Because there is no separate on-board power unit on the Richmond.    

Two eight-cylinder mtu gas engines of the 4000 series each generate 746 kilowatts of power. Both engines are housed in separate engine compartments.

It is a complex system of which Oli Hermann, up in his driver's cab, notices very much. The ferry drives like any other - even the acceleration behaviour is unchanged. "Every ferry has its own peculiarities and drives a little differently, whether there is a diesel or a gas engine in the engine compartment, I don't notice that," he says. Dieter Ehinger has a different opinion:  

"The engines have a particularly smooth running culture and purr quietly like a kitten."

Dieter Ehinger, Shipyard Manager

Whether "quiet as a kitten" or "completely normal" - only a few more days and the Richmond will officially enter service. Then the ferry will cross Lake Constance eight to nine times a day - depending on the season - and bring up to 700 passengers and 64 cars from Meersburg to Constance and back. It joins a fleet of five other ferries that are all powered by mtu engines. And hardly anyone will suspect that this is a very special ferry.  

Technology explained: These are the mtu gas engines

What distinguishes mtu gas engines

  • A multipoint gas injection system ensures dynamic acceleration behaviour and low emissions. This means that the IMO III emissions standard is met without the need for an exhaust aftertreatment system. The controlled combustion also ensures that the fuel is burnt efficiently.
  • The turbocharging of the mtu gas engines is single-stage with two parallel-operated, highly efficient exhaust gas turbochargers. The turbocharging system also has a controllable compressor bypass and an intake throttling concept. The engine thus has sufficient power reserves throughout the entire speed range for difficult driving manoeuvres.
  • The mtu gas engine is the only high-speed gas engine on the market that meets the requirements of the IMO IGF Code for a "gas-safe" engine room. Among other things, this means that all gas-carrying lines are double-walled for safety. This means that shipyards can design the engine room to be diesel-like and install the gas engine without any further safety precautions.

The Richmond in detail

  • Length: 82.5 metres
  • Width: 13.4 metres
  • Weight: approx. 840 tons
  • Passengers: 700 people
  • Vehicles: 64 cars
  • Load capacity: 400 tons
  • Engines: two 8-cylinder mtu gas engines from Rolls-Royce  
  • Power per engine: 746 kilowatts
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