Ferry Rheinthal, © Jobst Johann

A ferry over the Rhine has for many years been the link between Rüdesheim and Bingen, a cross-over between the federal German states of Hesse and Rhineland-Palatinate. The car ferry is highly frequented: both by local tourism and by commuters who want to get to Ingelheim and Mainz, but also into the other direction to Wiesbaden and the Frankfurt area, including its adjacent communities. This part of the Rhine belongs to the world heritage site Upper Middle Rhine Valley, meaning it is protected by law. This also means that there are no plans to build a new bridge at this section of the Rhine; the ferry is and will be the only local connection between both sides of the Rhine for many years to come. A group made up of different stakeholders from the industry, science and the two initiatives for hydrogen and fuel cells from Hesse and Rhineland-Palatinate has now conducted a feasibility study to determine whether electric engines could meet the necessary technical requirements for an emission-free ferry operation.

The calculations of the feasibility study were based on the actual conditions under which Bingen-Rüdesheimer Fähr- und Schiffahrtsgesellschaft operates the current Rheinfähre ferry line (see figure 2).

Feasibility study: objective and design
The aim of the study was to investigate in several steps whether it was possible to replace the existing ferry line by emission-free water transportation or if insurmountable hurdles would prevent such an endeavor. The steps included measuring the performance of the diesel engine, in order to obtain points of reference for the design of a fuel cell engine, and to answer the question if and how the fuel cell system would have to be complemented by batteries. Additionally, there was the issue of the H2 infrastructure that needed to be resolved, as the ferry line is not far away from the Energiepark Mainz (around 30 kilometers). The Energiepark generates 200 tons of hydrogen each year in a sustainable way through a Power-to-Hydrogen plant. Other steps dealt with the energy balance of the engine, the H2 supply, approval procedures and last but not least, economic viability.

The water transportation industry depends on the high reliability of its ships. This means that the conventional design of ship engines includes high power reserves as well as safety margins. Thus, the first step was to determine how much engine power was actually used when the ferry was in operation and how much energy would be needed on board in case of an emergency. In the framework of a master thesis, a measurement project collected ferry data on standard operation across several days and compared the measurements with the power output of the engines.

The Rheinfähre is equipped with four identical engines of 215 kW each. One trip requires only two engines and the other two are used as a reserve. The power required was determined by recording the output of one of the engines. The results showed that the usual output per engine during normal ferry operations amounted to no more than 33 kW, which represents merely 15% of the engine power installed. Thus the engines are far removed from optimal levels. The measurements and actual consumption values of the diesel refills enabled the research group to calculate the consumption of a fuel-cell engine and the dimensions of a hydrogen engine needed to match actual consumption.

To avoid overloading the fuel cell systems and to be able to meet peaks in demand, the group found a hybrid system of fuel cells and batteries to be the best solution in terms of energy demand and safety. Requests were sent to manufacturers of such systems and calculations were ultimately based on those which had already had maritime approval of Germanischer Lloyd (now DNV GL). The power train design with two fuel cell systems to supply the engine with energy was designed with redundancy in mind: The systems for propulsion and onboard power supply were supposed to be available twice to allow a so-called N+1 redundancy. The calculated hydrogen demand added up to 120 kg per day in summer and 80 kg per day in winter, corresponding to the difference in seasonal frequency of ferry runs.

Storage design
The aim was to use sustainably sourced “green hydrogen” from the beginning. Currently, the ferry tanks are refilled with diesel at a special dock every other week. A similar scenario was requested for a hydrogen refill. But it proved impossible to adapt the planned hybrid system of fuel cells and batteries to fit a two-week interval. Business partner Linde thoroughly investigated different options until ultimately, the plan was to integrate an H2 container co-developed by Linde for pressure levels of 300 to 500 bar. This container is a fast-exchange version, which allows the operators to replace an empty container by a full one within a short period. It would mean that refilling the ferry tanks could be done during the usual unloading and loading times.

Legal issues
When the feasibility study was conducted, one focus area was the if and how of approval of this kind of car ferry, the question of which authorities would be responsible for the approval, what legal, safety or other regulations had to be observed and whether the approval of such a ferry would be possible at all. All of these questions could be answered with yes, as some of the rules had already been adapted for retrofitted engines. The relevant technical regulations can partly be found among existing rules of the Inland Waterway Vessel Inspection Ordinance (BinSchUO from 2013) or can be derived from them. The added application of regulations issued by Germanischer Lloyd on the use of fuel cells onboard water vehicles (GL, 2002) leads to a high legal certainty regarding approval of the ferry.

Funding
To get an idea of the costs, the research group conducted a rough investment estimate during the project run. Additionally, it calculated the cost of capital, consumption and operation and compared them with the old values.

Regarding the design favored by the study, costs were estimated at around EUR 9.1 million based on current prices of fuel cells and the related hydrogen infrastructure. A conventional ferry costs around EUR 5.5 million today, plus VAT. This means that costs would be at least 65% above the ones for the conventional version.

But it is not only the high additional investment – which could be offset by subsidies – that poses a challenge to possible realization. Today’s combustion technology, whether it is based on diesel or diesel and electricity, also still has an edge over fuel cells regarding economic and useful life. Simulations showed that the fuel cell stacks would likely have to be replaced after six years. It can be assumed, however, that it will be possible to overcome this limitation within the next years.

Regarding operational costs, the research group investigated – in addition to regular maintenance of the technical systems, engines, fuel cells and batteries – especially the consumption costs for diesel in comparison with hydrogen. The current price of around EUR 10 per kilogram (Linde Gas, 2015) does not constitute an advantage over diesel. This means that the use of hydrogen in ferries would require both initial investment subsidies for ship and infrastructure (e.g., for a demonstration project or a later market introduction) and subsidies to cover operation costs or funds to offset the added fuel costs for hydrogen (e.g., through higher taxes on fossil fuels).

To create the feasibility study, the consortium planners, together with the two research organizations, Transferstelle Bingen and Hochschule RheinMain, submitted an application to the ministries of economy in Mainz and Wiesbaden. At that time, the ferry operator was planning to purchase a new ferry, although it was clear that such an H2-fuel cell ferry would be a prototype and the research or demonstration aspect would up the price tag. It meant that the plan could not be realized by the ferry operator without government support.

To present the results of the feasibility study in detail and to discuss further applications of fuel cell systems in the water transportation industry, the Transferstelle für Rationelle und Regenerative Energienutzung Bingen and HA Hessen Agentur organized a workshop, Sustainable Marine Propulsion Systems – Water Transportation on Rhine & Main Using Batteries and Fuel Cells, together with the hydrogen fuel cell network from Rhineland-Palatinate (H2BZ Kooperationsnetzwerk RLP) and the hydrogen and fuel cell Initiative from Hesse (H2BZ-Initiative Hessen) in the Rhine-Main area on Feb. 24, 2016.

The project partners were HA Hessen Agentur, Hochschule RheinMain, Transferstelle für Rationelle und Regenerative Energienutzung Bingen, Linde Gas, H2BZ-Initiative Hessen, H2BZ Kooperationsnetzwerk RLP as well as Bingen-Rüdesheimer Fähr- und Schiffahrtsgesellschaft. The project was subsidized by the State Ministry of Rhineland-Palatinate for Economic Affairs, Climate Protection, Energy and Regional Planning and the Hessian Ministry of Economy, Energy, Transport and Regional Development.

References: Machbarkeitsstudie Rhyntal, B. Scheppat, M. Werner, O. Türk, J. Schied, J. Walter

Authors:
Professor Dr. Birgit Scheppat, Matthias Werner
Both from Hochschule RheinMain

Professor Dr. Oliver Türk, Jochen Schied, Joachim Walter
All from Transferstelle für Rationelle und Regenerative Energienutzung Bingen (TSB)

Markus Lämmer
HA Hessen Agentur GmbH, Geschäftsstelle Wasserstoff- und Brennstoffzellen-Initiative Hessen