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For a long time, manufacturers explored ways to replace the electrochemical battery. Higher energy densities, smaller size, lower cost per watt and faster charging times are on the wish list. Electrical energy from rechargeable batteries is expensive when considering the high purchase price, the limited life span and the limited power this portable source can deliver. Read more about Batteries against Fossil Fuel.
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Will the fuel cell replace the battery?
Since the invention in 1839 by Sir William Grove, the fuel cell remained a scientific oddity. It was only in the 1950s that this power generator was used for the first time as part of US space and military programs. In the 1980s, the fuel cell had another rebirth when scientists and stock promoters envisioned a world powered by a clean power source fed by an inexhaustible fuel, hydrogen. They forecasted cars running by fuel cells and households deriving electrical power from back-yard fuel cell units. In the late 1990s, fuel cell technology gained hype status and many saw this power source as the gateway to the future. High manufacturing costs and short service life were in the way to make this dream a reality.
The fuel cell uses hydrogen and oxygen as fuel. Combining the two gases generates electricity and water. There is not combustion and no pollution. The byproduct is pure water. The system runs so clean that Ballard, a developer of fuel cell stacks, offered the guests tea from the hot water produced by the fuel cell. The absence of exhaust fumes enables running a fuel cell in an enclosed room, such as an office of living room. The theoretical energy output of the fuel cell is high, but over half is lost in heat.
During the past years, portable versions of the fuel cells have emerged. The most promising miniature fuel cell is the direct methanol fuel cell. Read more about Fuel Cell Technology. DMCF is inexpensive, convenient, does not require pressurized hydrogen gas and provides a reasonably good electrochemical performance. Current systems produce 900Wh of power and offer an energy density of 102Wh/l, but this volumetric dimension is still large compared to a lithium-ion battery. Charging consists by replacing the cartridge on the fly. This provides a continued source of energy, similar to fueling a car. Figure 1 shows a miniature Toshiba fuel cell, also known as micro fuel cell; Figure 2 demonstrates refueling with methanol that is 99.5 percent pure.
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Figure 1: Micro fuel cell. This prototype micro fuel cell is capable of providing 300mW of continuous power.
Courtesy of Toshiba |
Figure 2: Toshiba fuel cell with refueling cartridge. The fuel in a 10ml tank is 99.5 percent pure methanol.
Courtesy of Toshiba |
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Manufactures of micro fuel cells admit that a direct battery replacement with high power, small size and competitive price is still several years away. Rather than offering an outright battery replacement, today’s micro fuel cell serves as a charger to provide continuous operation for the onboard battery.
Miniature fuel cells are still in development and the reasons are multifold. A typical micro fuel cell has an output of 300mW and can only supply enough power to keep a cell phone battery charged. A laptop consuming 30 watts would need 100 miniature fuel cells to sustain continuous operation. Furthermore, transportation authorities prohibit passengers from carrying bottled fuel on an aircraft, a rule that might soon change. The Dangerous Goods Panel (DGP) of the International Civil Aviation Organization (ICAO) has already made an exclusion to allow the transport and operation of methanol fuel cells on commercial flights. This provision does not yet extend to bottled hydrogen.
Improvements are being made, and Toshiba unveiled prototype fuel cells for laptops and other applications generating 20 to 100 watts of power. At 100 Wh/l, the units are compact and the specific energy is comparable with a NiCd battery. (I appreciate the honesty of Japanese manufacturers in describing the technology as being in its “infancy.”) Toshiba has given no indication as to when the product could be commercially available. Meanwhile, Panasonic claims to have doubled the power output from 10 watts to 20 watts with similar size. Panasonic specifies a calendar life of 5,000 hours if the fuel cell is used intermittently for eight hours per day. Durability had been standing in the way of commercializing its use.
Angstrom Power is developing a portable fuel cell that runs on stored hydrogen and takes oxygen from the air. The system has no pump and fan and is totally silent. Increased efficiency and smaller size are the advantages of pure hydrogen over methanol. The aim is to offer a power source that is clean, quiet and can be refueled on the fly. Similar applications are possible for cellular phones. Figure 3 illustrates an application as a bicycle lamp.
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Figure 3: Fuel cell powered bicycle lamp.
The 21cc cartridge provides the equivalent energy of about 10 AA disposable alkaline batteries. The only by-product is water vapor. The runtime between refueling is 20 hours.
Courtesy of Angstrom Power |
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According to Angstrom Power, the micro hydrogen™ bike lights have delivered good performance in winter and spring conditions and the user feedback is positive. The hydrogen fuel is stored in a 21cc cartridge and provides the equivalent energy of about 10 AA disposable alkaline batteries. The only by-product is water vapor. Refueling takes a few minutes and provides a continuous runtime of about 20 hours.
Current draw is not critical on a small bicycle light, especially when using low-drain LED technology. A laptop, on the other hand, requires about 40 watts of power, and a small fuel cell cannot provide enough output to sustain the demand. The system needs a battery as back up. In essence, the fuel cell becomes a slave to the battery and serves in the capacity of a charger. The same scenario applies to fuel cell-powered cell phones and cameras.
Military and recreational users are also experimenting with the miniature fuel cell. Figure 4 illustrates a portable fuel cell made by SFC Smart Fuel Cell. The EFOY fuel cell comes in different capacities that ranges from 600 to 2160 watt hours per day.
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Figure 4: Portable fuel cell for consumer market
The fuel cell converts hydrogen and oxygen to electricity and clean water is the only by-product. Fuel cells can be used indoors as an electricity generator.
Courtesy of SFC Smart Fuel Cell AG
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As good as the fuel cell may look from the outside, the product leaves many unresolved problems that prevent broad consumer acceptance. One of the drawbacks is a slow start-up, and another is the low electrochemical activity at the anode. This is especially apparent with the DMCF. Each cell produces about one volt and when loaded, the relatively high internal resistance causes the voltage drops quickly. The inherent limited power bandwidth causes this phenomenon. A third weakness is the relatively short life span. The capacity may be high when new but the output begins to fade with use similar to an aging battery. One of the inhibiting factors is the gradual rise of internal resistance, which limits applications drawing heavy load currents. High device and operating costs are another disadvantages. Read more about Fuel Cell Technology.
It is regretful that the fuel cell has not enjoyed the same breakthroughs as microelectronics. The Moore’s law does not apply here. When examining alternative power sources to the struggling fuel cell, the traditional battery begins to look surprisingly good. A battery pack is small, clean, quiet, and provides an instant source of high power on demand, even at cold temperatures. It is our hope, however, that the fuel cell will eventually succeed as a clean energy source to extend the range of portable power and reduce pollution. |
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dear sir I can not understand how it can be use portable , my questions are following.
1. the source for oxygen and hydrogen
2. storage of water
3. running cost(how much electric can produce by how much gas)
4. can it be use commercially