Project Summary

Feasibility study exploring opportunities for recharging electric seagoing vessels powered by flow batteries, by pumping electrolyte from a shore based charging system.

Project Achievements

We have engaged with flow battery manufacturers, via the IFBF, to establish electrolyte energy densities. We have run multiple discrete-event simulations (using SimPy) using 2018 ship data provided by Portsmouth International Port. With Marine South East, we have studied the viability of the shore charging system and we have calculated the pumping rates required for electrolyte transfer.

Conclusions

Electrolyte energy densities vary considerably: 15Wh/L for old systems, 30Wh/L claimed for new vanadium electrolytes, 75Wh/L claimed for organic electrolytes promising and R&D projects aspire to ~240Wh/L using novel chemistries such as lithium-flow, zinc-air and graphite-sulphur. Initial calculations suggest that flow battery propulsion (75Wh/L) is viable for short-range ships (100-200 nautical miles). This is the scope of a separate study, working with a naval architect.

The SPIDS simulation showed that the flow battery system studied required only 10-20% of the grid power that would be required for solid ship battery charging, which is highly beneficial. As an illustration, the shore charging system for cross channel ferries visiting Portsmouth would require 4 large onshore electrolyte holding tanks, each at 15m high & 17m diameter.

The ship/shore electrolyte transfer is viable with off-the-shelf pumps and pipes. The pumping uses approximately 1% of the energy stored in the transferred electrolyte. The SPIDS project offers a novel approach to the full electrification of short distance shipping. Our ambition is to deploy a trial system to encourage the shipping industry to consider alternatives to fossil fuels.