Inland waterway transport already covers a significant proportion of freight transport volumes. Its further expansion is part of the European strategy to shift freight transport from road to rail and waterways.¹ Electric propulsion concepts represent important approaches for climate-neutral inland shipping. This is accompanied by a considerable improvement in air quality. Hybrid solutions with hydrogen and batteries are currently in the spotlight.

Use of battery storage

There are two different basic concepts for the use of battery storage in the propulsion technology of inland vessels: battery-electric and hydrogen-based drives. In battery-electric drives, the entire drive energy is carried in traction batteries. In hydrogen-based drives, hydrogen is converted into electricity by means of a fuel cell, which is then used for the electric drive via a battery.⁵ In addition to the propulsion energy, the energy for the on-board electronics can also be provided accordingly on the ship. This is then usually done by using independent batteries and thus detached from the traction battery. The loading and discharging process in port with the corresponding machinery is also occasionally the subject of electrification measures.

The considerations of Holbach offer an orientation to the possible applications of electromobility on the water.⁵ The hydrogen concept presented by him requires 3 fuel cells with an output of 100 kW each as well as a battery capacity of 2 x 1,160 kWh for propulsion and 2 x 116 kWh for the on-board electronics.⁵ For bridging short ranges (in the range of 65 km/day) and medium operating times (8 hours/day) he recommends purely battery-electric drives, for medium ranges (100-130 km/day) and longer operating times (16 hours/day) hydrogen-based drives. Depending on the infrastructure, a charge-stop strategy is recommended for the latter for ecological and economic reasons, which uses repeated intermediate charging of the battery to reduce fuel cell use.

Batteries can also be used in hybrid concepts with fossil fuels. Here, diesel generators produce electricity for the ship's electric motor. By decoupling the mechanical connection between the ship's engine and the ship's propeller, which is common in combustion engines, and by using a buffer battery, the entire system can be operated at optimum efficiency. In this way, fuel consumption as well as pollutant emissions can be reduced to a considerable extent.⁶

Performance requirements

Inland shipping is increasingly becoming the focus of public discussion due to its negative environmental impact. Environmental compatibility therefore also plays a central role in the battery technology used. In view of the average operating life of the vessels, investment security in conjunction with high safety requirements also play a key role. The batteries used should last at least 30 years and present the lowest possible risks in terms of flammability and explosion.

The fast-charging capability of the battery determines how much power can be charged for the onward journey during the discharging or charging process in port. It is thus an important factor for route planning.