UDT 2020 Will LIHC (Liquid Inorganic Hydrogen Carriers) be the next breakthrough in underwater propulsion? Y . Shaham 1 1 Electriq Global, Tirat Carmel, Israel The entrance of AIP (Air Independent Propulsion) systems into the conventional submarine market, made a tremendous improvement in the operational capabilities of submarines. One of the most common AIP systems is a fuel cell system. In order to get the electrical power, the fuel cell requires constant supply of hydrogen and oxygen and the storage medium is a key limitation. Electriq~Global presents a solution in developing a hydrogen-based power generator technology through a safe and cost-effective H 2 on-demand solution, using hydrogen-rich liquid carrier operated in ambient pressure, activated by a low-cost catalyst. 1 Introduction Easy to implement Layout on board (compare to - metal hydride cylinders) e.g., only tanks inside or outside The entrance of AIP (Air Independent Propulsion) the pressure hull and a relatively small size system. No additional O 2 consumption for H 2 production . systems into the conventional submarine market, made a - No Carbon emissions – no CO 2 discharged. tremendous improvement in the operational capabilities - of submarines. The higher endurance enables submarines Low temperature range: 80-100°C, cooling by sea - to extend their operational time and thereby provides two water. Low signature footprint – acoustic and magnetic. crucial benefits: it postpones the need to charge the - Safety – no hydrogen refueling on board. batteries and allows the submarine to conduct its - operative mission in a stealthier manner. Engineering system easy to construct. - One of the most common AIP systems is a fuel cell Low CapEx investment. - system. In order to get the electrical power, the fuel cell Pressure Range and hydrogen purity suitable for - requires constant supply of hydrogen and oxygen. Fuel cells. Suitable for all submarine sizes. Despite its common use, the fuel cell system currently - has a key limitation – the hydrogen storage medium, In order to provide a clear power generation on-board energy density and capacity. a submarine, Electriq~Global developed its patented A typical way for carrying the hydrogen on board, is Electriq~System, that produces hydrogenation, by using a metal hydride cylinders, installed in the keel area immersing the catalyst (Electriq~Switch) in Electriq~Fuel outside of the pressure hull. (LIHC) with. However, Storing the hydrogen on-board the submarines The catalyst innovation can be summarized as: implies significant weight and volume constrains, due to - Highly active: nanoclusters ensuring fast release of the low weight and volume hydrogen density of the metal H 2 . hydride cylinders (less than 1.5% of H 2 storage capacity), - Resilient and durable catalyst. which is used to carry the hydrogen. - Low cost: Catalyst is based only on non-precious This limitation forces submarine manufactures to and widely available material and commonly used build a bigger pressure hull and due to general procedures. arrangement aspects, the amount of hydrogen is limited To ensure the fuel will be “cost competitive”, and so is the endurance. In the quest of providing the ideal power generation Electriq~Global is currently developing a recycling solution for AIP systems, Electriq~Global is developing a process, where used fuel can be recycled and replenished hydrogen based power generator technology through a with hydrogen and turned into fresh fuel that can be reused. safe and cost-effective H 2 on-demand solution, using hydrogen-rich liquid carrier operated in ambient pressure, activated by a low-cost catalyst. 2 Technology The LIHC, ranges in hydrogen weight density of 2.7%-8%. The LIHC can be stored inside the pressure Our technology is based on three components: hull or in tanks outside. The benefits of using this type of hydrogen source are 2.1 Fuel substantial as detailed below: Increased weight efficiency. -
UDT 2020 ) has been known and The reaction of borohydride ( studied since the 1950s. [1] Borohydride combined with alkali metal (M= , , etc.) are the most well- known composite of borohydride. Their attraction is linked to the high gravimetric percentage of hydrogen that they store. The reaction, where H 2 (together with MBO 2 ) is released, is either thermolysis or hydrolysis. [2] When the potassium borohydride comes in contact with water, it produces 4 moles of H 2 for every mole of KBH 4 , as the following hydrolysis reaction shows: Most of studies has been focused on sodium borohydride (NaBH 4 ). Sodium borohydride is stable in dry air and easily handled. [3] Our fuel is based on different novel approach, using Potassium Borohydride (KBH 4 ). The hydrolysis with NaBH 4 releases more energy than KBH 4 (- mol and - mol respectively, see table 1) and has higher kinetics. This result in faster, hotter, less controllable reaction. Consequently, although KBH 4 has lower gravimetric percentage of Hydrogen, it makes him a safer, non-flammable, non-explosive solution and a better candidate for more certain applications. [4,5] Table 1- Energy releases in the hydrolysis [8] Fig. 1 - Solubility of KBH 4 in water as a function of weight percent and KOH weight percent at 25°C We work with several types of fuel that can be X= K X= Na roughly divided in to 2 groups, liquid fuel and paste like XBO 2 -981.6 -977 fuel. Liquid fuel contains different amounts of KBH 4 and XBH 4 -227.4 -188.6 KOH and will work only when in contact with catalyst 0 H 2 (that will be discussed later). Paste like fuel contains H 2 O -285.8 higher concentration of KBH 4 and without any KOH. f This fuel takes advantage of the spontaneous release mol -182.6 -216.8 that occurs when water meets the borohydride. After first contact, a catalyst is inserted and stimulate the reaction even more. Both types of fuel harness different and There are many parameters that can affect the KBH 4 opposite advantages of the KBH 4 and are ideal for hydrolysis. Amongst are concentration, pH, and different applications. temperature. Higher temperature can accelerate the In figure 2 we can see an experiment of hydrogen reaction by kinetic manners, while the highest spontaneous release. The experiment was done with paste temperature that can be achieved is C as it’s the like fuel with relatively small concentrations of KBH 4 . water boiling point. H 2 can also release in low 50g of 5.3M KBH 4 solution was prepared and a reaction temperatures as 25°C has been tested in our lab. occurred at 40°C. After six minutes a total of 0.8L of H 2 Adding alkaline to the solution can help control the was released without any external stimulant in form of 5 . In figure 1, we see a H 2 spontaneous release by KBH 4 catalyst or heat. When mixing 50g of 7.5M KBH 4 solubility test of KBH 4 in water at 25°C as a function of solution, the reaction started spontaneously at 60°C. After its weight percent and the KOH weight percent. We can 6 min, 2.65L of H 2 was released. The reaction was see that when KOH is present, KBH 4 above 9wt% (the exhausted after 5.5 hours while most of the reaction g solubility of KBH 4 is g at 25°C), display happened after 4 hours. At the end of the reaction, the fuel produced 25.73L of H 2 while the theoretical H 2 solubility issues and adding more KOH does not production of 7.5M KBH 4 is 31.18L, only 17% less than necessarily benefit us. However, experiments in higher the theoretical value. temperature of 65°C, show us that KOH can delay the H 2 spontaneous release and that is why it is necessary.
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