Fujitsu Laboratories: a new step in fuel cells development
Fujitsu Laboratories developed a new prototype of a passive notebook fuel cell. The new materials enable the use of 30% methanol as an energy source providing longer notebook, PDA, mobile handset operation and also higher energy capacity. This forced fuel injection system fully based on gravity and natural convection is considered optimal for small machines.
The press release states that as notebook PCs, PDAs and mobile phones evolve to deliver higher performance and greater functionality, they have also come to demand more electrical power. But the lithium-ion (Li-ion) batteries commonly used today have already approached the limits of their capacity, which has made the development of a higher-capacity power source a matter of greater urgency.
Micro fuel cells, envisioned for use in mobile devices, generally use alcohol solutions as fuel. In terms of energy density, these fuel cells offer up to 5-10 times the power per unit weight of a Li-ion battery. From the user´s perspective, micro fuel cells have advantages in that they offer cheap and easy means to power electronic devices by simple refueling, enabling continuous use when traveling with no access to the power grid.
According to the press release, passive systems are best suited for micro fuel cells to help keep the package compact and light, as they do not require fuel pumps or circulatory fans. Thus, in order to obtain long runtimes without such functions, the fuel cells must be able to handle concentrated methanol as its fuel.
To date, micro fuel cells mainly have employed fluorinated polymers for their solid electrolytic material. But fluorinated electrolytes are too readily permeated by the methanol molecules in the fuel, so that when concentrated fuels are used, fuel is lost in the generating process and power capacity suffers, and the sub-reaction of methanol and air drastically reduces wattage, creating a problem known as methanol crossover.
And Fujitsu developed a new material technology for the membrane electrode assembly (MEA) (*2). An aromatic hydrocarbon solid electrolyte material, which allows slow methanol permeation, is covered with a high density of highly active platinum-based nano-particle catalyst with methanol blocking properties. This reduces the total MEA methanol crossover effect to one-tenth that encountered with typical fluorinated polymers.
This new material technology for MEA enables the direct use of methanol concentration of 30%, previously too high to use, resulting in greater capacity from passive fuel cells. Applying this technology in a prototype micro fuel-cell system with 300ml of 30% methanol enables a notebook PC to run for eight to ten hours. Furthermore, the prototype fuel cell has been slimmed down to a thickness of a mere 15mm, while delivering power output levels of 15 watts.
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