Date:Apr 30, 2018
There are geographic locations where fuel oil prices are high and electric power prices comparatively low. Such locations enhance the business case to operate electric propulsion along inland waterways and coastal services. New battery technologies include carbon-foam sulfuric acid technology, sodium sulfate electrolyte technology and silicon dioxide batteries.
Introduction
In maritime history, submarines sailing near their depth limits utilized rechargeable electric battery propulsion. Lead-acid battery technology of an earlier era is now becoming obsolete for transportation based applications. In the area of battery-powered vehicles, maritime transportation offers several advantages over battery-powered road or railway transportation. In road transportation, the space requirements and weight of batteries becomes problematic while the vibration, jolts and shock loads involved in railway transportation puts many electric battery technologies at a competitive disadvantage. Maritime transportation can provide the weight carrying capacity, the volumetric space and the jolt-free smoothness to utilize electric battery energy storage.
Maritime transportation is compatible with electric battery energy storage technologies that would otherwise be impractical in road transportation and even in railway transportation. Maritime transportation can utilize grid-scale storage battery technologies that involve the physical movement of electrolyte or that involve lower levels of energy storage density that would in turn require additional volumetric and weight carrying capacity. A battery-electric tug boat built to double the width and triple the length of existing tugs and able to carry high weight levels could propel and navigate a train of coupled barges along an inland waterway.
Present Technologies
At present, battery-powered maritime vessels use one of three grid-scale storing technologies that include lithium-ion battery technology, flow-batteries that involve movement of the electrolyte and molten sodium-sulfur battery technology that involves high temperature. While maritime vessels can carry the weight of sodium-sulfur batteries, the technology also requires considerable insulation as these batteries typically operate in excess of 300oC with up to six hours of power delivery, with delivery durations of up to 18 hours being possible. More recent research aims to reduce the operating temperature of the battery to 100oC, making the technology more attractive to maritime application.
There are several variations of flow battery technology that include using such materials as vanadium and even uranium in the electrolyte. When electrolyte flows through the battery, it can simultaneously deliver electric power while also being recharged. Such an event could occur when a vessel sails at low speed through a narrow canal or transits through a series of navigation locks where overhead trolley power collection is available. Lithium-ion storage technology avoids the problem of having to operate at sustained high temperature and has no need to flow the electrolyte through the battery in order to operate.
