COMPARISON OF ALTERNATIVE PROPULSION SYSTEMS - A CASE STUDY OF A PASSENGER SHIP USED IN PUBLIC TRANSPORT

The unique feature of river transport is given by the rivers' flow and the changing cross-sections of the riverbed. Most river vessels operate with a conventional propulsion system. Engine power should be scaled to the maximum expected power demand, which means that the engine is forced to run at medium or low load, almost always downstream and upstream for part of the operating time. In these cases, the engine's operating point is far from ideal, so there is an increase in specific fuel consumption. This is especially true for ships that are forced to stop and start frequently. An example for the circumstances mentioned above is the BKV-100 type ship operated at Budapest as a public transport vessel. A measurement on a schedule route revealed that with given environmental conditions (water level, river flow rate, etc.), the power installed in the vessel is almost double the maximum power demand measured. Due to this reason and to the differences in power demand of downstream and upstream, it may be technically worthwhile to replace the existing conventional propulsion system with an alternative propulsion system. Based on the measurements, in this paper the authors compare 4 alternative drive systems to the existing one with regards to fuel consumption and the investment costs. Beside this, a simple but effective fuel consumption estimation method and a simple cost-benefit analysis are also described.