Portable Devices Running on Hydrogen

Two billion chargers are sold each year through the mobile phone charger market. The travel charger sub-segment is the fastest grow­ing charger segment, with an estimated market value of more than €11 billion. A number of new fuel cell companies using hydrogen fueled fuel cells are now actively trying to establish sales in this market.

Singapore-based Horizon Fuel Cell Technologies28 is a fuel cell manufacturer that offers a wide range (10 W to 5kW) of standard PEM fuel cell systems, as well as customized fuel cell system configurations up to 30kW.

The company recently commercialized the table-top hydrogen refueling station Hydrofill (Figure 4.22) and the portable emergency fuel cell back-up generator HydroPak. The Hydrofill system allows con­sumers to refill solid state cartridges in a simple way, using water and electricity as the only inputs.

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The HydroPak (Figure 4.23) is the result of a collaborative effort with Millennium Cell,29 a pioneering US fuel cell company that went out of business in 2008, to bring forth a low cost ($400) portable generator that uses $20 disposable cartridges, making it affordable and effective.

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Figure 4.24 Hydrogen storage – Comparison of chemical hydrides in terms of weight percent.

(Reproduced from Y. Wu. Hydrogen Storage via Sodium Borohydride. Current Status, Barriers, and R&D Roadmap, GCEP – Stanford Uni­versity, April 14-15, 2003, with kind permission.)

 

As a result, by adding water only, and plugging the Hydrofill into an electrical wall-socket (or a solar panel), consumers can automatically generate hydrogen and store it in a safe, solid form in Hydrostik car­tridges. For example, 25 W DC power is enough to produce 10 L of hydrogen per hour, and to fill one Hydrostik cartridge with hydrogen stored in solid form.

With the Hydrofill desktop refueler (Figure 4.25), users no longer need to wait for the infrastructure for hydrogen to be developed, because water is ubiquitous and the device can use power either from the grid or from solar PV modules. Once full, the battery-like refillable Hydrostik can be unplugged from the Hydrofill and placed into a new portable power device named Minipak (or other fuel cell devices) to deliver 1.5 W via the USB port to power smartphones, lights and other devices.

Each Hydrostik can store 11 Wh of energy, which is enough for one or two charges of a 3G smartphone or two to three charges for the average cellphone. In comparison with current primary and rechargeable bat­teries, with 1 W power consumption, most AA batteries can only last 1 hour, while a Hydrostik has enough energy to last 10 hours. In other words:

1 Hydrostik = 10 disposable AA batteries at 1W continuous power consumption.

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Figure 4.25 The Hydrostik is competitive on cost/performance with existing battery devices, providing a low-cost (the whole system costs about $200) por­table energy option for users.

(Reproduced from Ref. 25, with kind permission.)

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Figure 4.26 The MINIPAK includes a passive air-breathing PEM fuel cell, able to draw hydrogen stored as solid hydride inside the specially designed HYDROSTIK cartridge.

(Reproduced from Ref. 25, with kind permission.)

Given that one cartridge can be refilled 100 times, the same Hydrostik over its lifetime replaces 1000 (10 x 100) disposable AA batteries.

The cartridges are inserted into the portable power charger and power extender Minipak (Figure 4.26), which is compatible with a variety of portable electronic devices and thus positioned to address the needs of users of power-hungry devices.

At the Consumer Electronics Show in 2012 in Las Vegas, the Swedish company myFC introduced its PowerTrekk (Figure 4.27) fuel cell charger (and PowerPukk fuelling cartridges), also aimed at the portable electronics market.31

Again, users simply insert a fuel ‘‘puck’’ and add water to allow rapid recharging of their cellphones, cameras and global positioning system (GPS) devices. Using sodium silicide (NaSi) storage, the fuel cartridges are activated by a small quantity of water and produce up to 4 L of hydrogen gas. Sodium silicide is a pyrophoric material. The fuel employed in the PowerTrekk is made of a specially formulated NaSi powder that is easily handled, does not react with dry oxygen, and absorbs moisture from air slowly without ignition.

Sodium silicide is a pyrophoric material that requires special storage and handling. The fuel developed by SiGNa Chemistry, Inc.32 is made of Na4Si4 powders that react rapidly, but controllably, with water to produce hydrogen. The company has achieved the highest hydrogen

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Figure 4.27 The new myFC portable, water-powered fuel-cell charger PowerTrekk can be used to recharge a smartphone. The PowerTrekk will be sold initially for $299, and will be on sale in the USA from May 2012. (Reproduced from Ref. 31, with kind permission.)

production yield of 9.5 wt%, i. e. 0.095kg H2 per 1 kg fuel, according to the reaction in Equation (4.2):

2NaSi(s) + 5H2O(l) ! Na2Si2O5(aq.) + 5H2 + Heat(~175kJmol“ ^ (4.2)

In other words, the reaction produces five moles of hydrogen, almost instantaneously, from the reduction of five moles of water and only two moles of NaSi. As a result, sodium silicide provides greater power density per unit of weight than amorphous, sol-gel silica doped with sodium (Na-SG, Figure 4.28).33

At the heart of the fuel cell chargers is the FuelCellStickers pro­prietary technology. Made from foils and adhesives, these ‘‘stickers’’ – which are reliably and efficiently produced via a roll to roll, high volume manufacturing process – are assembled into a flexible assembly less than 2.75 mm thick. The company claims to be the world leader in micro fuel cell, planar technology featuring power density over 600 mW cm~3.

The modular and scalable FuelCellStickers can also be assembled into ‘‘Blades’’ (Figure 4.29), providing higher power and efficient perfor­mance in a form factor less than 3 mm thick. These flexible components can be easily integrated on to the front or back covers, lids, bottoms and sides of mobile devices.

Подпись: Figure 4.28 Production of hydrogen by the two SiGNa Chemistry materials. (Reproduced from Ref. 31, with kind permission.)
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Figure 4.29 Flexible ‘‘Blades’’, made by myFC, are fuel cell components with a form factor less than 3 mm thick, ideally suited for customizable integration. (Reproduced from Ref. 31, with kind permission.)

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