A study on the integration of a novel NaBH4 fueled hybrid system for a small inland vessel

Abstract

Even though shipping is one of the mos fuel-efficient modes of transport, the industry was responsible for over 900 million tonnes of CO2 equivalent emissions in 2015. This is equivalent to the annual emissions of Germany. Besides greenhouse gas (GHG) emissions ships engines also cause particulate matter, NOx and noise pollution. As a result, the shipping industry is already facing strict rules and regulations, and these are expected to become even more strict in the near future. These developments have led to an increased interest in zero-emission solutions and one especially promising area is hydrogen-electric propulsion. By combining hydrogen produced from excess renewable energy with oxygen in a fuel cell, water and electricity are produced. The problem, however, is the storage method for hydrogen, traditionally hydrogen is stored in compression tanks under 300 to 700 bar. But due to the low density of hydrogen, this still results in large installations. Additionally dealing with large amounts of hydrogen gas requires extra safety precautions. An alternative way of storing hydrogen is by binding the gas to another substance like sodium borohydride or NaBH4. This substance is in a solid form and reacts with water to produce hydrogen and sodium metaborate (NaBO2). The NaBH4 crystals can be stored as a powder and are safe to handle under atmospheric conditions. Also, the substance has a high energy density, even comparable to that of conventional diesel fuel.