System-level comparison of ammonia, compressed and liquid hydrogen as fuels for polymer electrolyte fuel cell powered shipping

Abstract

With the aim to reduce emissions from marine transport, electric propulsion systems for a water taxi and container ship powered by a hydrogen polymer electrolyte membrane fuel cell system are designed and analyzed compared to the current fuel-oil engine systems in terms of system energy and exergy efficiency, fuel consumption, mass and volume, environmental impacts and cost. Hydrogen is stored either as a compressed gas (GH 2 ), cryogenic liquid (LH 2 ) or produced from liquid ammonia (LNH 3 ) and can deliver 91%,91% and 88% greenhouse gas reductions, respectively. All hydrogen sources fit within ship volume and mass constraints apart from GH 2 in the cargo ship. In the absence of carbon policy measures, the costs over a 25-year system life are 108% (GH 2 ), 112% (LH 2 ), 116% (LNH 3 ) greater for the container ship and 43% (GH 2 ), 105% (LNH 3 ) greater for the water taxi. A carbon tax of £75-191/tonne CO 2 eq would allow the low carbon options to become cost competitive. • Comparison of diesel and fuel cell propulsion for marine freighter and water taxi. • Liquid/gaseous H 2 and cracked NH 3 compared to fuel oil (with/without) NH 3 . • Fuel cell power plants meet all operational requirements (weight, volume,power). • Fuel cell propulsion reduces lifecycle greenhouse gas emission by 88%–91%. • A CO 2 tax of 75-191 £/tonne CO 2 eq would equalise total cost over a 25 year lifespan.