Nedostatucite na tazi bateria kato cialo e tegloto i, koeto e 10 paunda - az lichno ne mislia che bih nosil tozi (work station) v chantata si,sveta bi triabwalo da vurvi kum mobilnost.
(source: gizmodo.com)
No eto oshte edna statia na tema fuel cells kudeto se kazwa che niakoi ot golemite vendori planirat/ili veche sa vkliuchili v producite si tozi vid baterii, malko ili mnogo kato chovek koito
e smenil 4 laptopa i nai serioznia mu problem do sega e bil towa kolko vreme shte mi izdurji bateriiata - towa e liubopitna tema za men.
(source: extremetech.com)
What is Fuel Cells and How the technology work?
A fuel cell is an electrochemical energy conversion device. It produces electricity from external supplies of fuel (on the anode side) and oxidant (on the cathode side). These react in the presence of an electrolyte. Generally, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate virtually continuously as long as the necessary flows are maintained.
Fuel cells differ from batteries in that they consume reactants, which must be replenished, while batteries store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and relatively stable.
Many combinations of fuel and oxidant are possible. A hydrogen cell uses hydrogen as fuel and oxygen as oxidant. Other fuels include hydrocarbons and alcohols. Other oxidants include air, chlorine and chlorine dioxide[1].
Technology
In the archetypal example of a hydrogen/oxygen proton exchange membrane fuel cell (PEMFC), which used to be called solid polymer electrolyte fuel (SPEFC) around 1970 and now is polymer electrolyte membrane fuel cell (PEFC or PEMFC, same as the short writing of proton exchange membrane) while the proton exchange mechanism was doubted, a proton-conducting polymer membrane, (the electrolyte), separates the anode and cathode sides.
On the anode side, hydrogen diffuses to the anode catalyst where it later dissociates into protons and electrons. The protons are conducted through the membrane to the cathode, but the electrons are forced to travel in an external circuit (supplying power) because the membrane is electrically insulating. On the cathode catalyst, oxygen molecules react with the electrons (which have traveled through the external circuit) and protons to form water. In this example, the only waste product is water vapor and/or liquid water.
In addition to pure hydrogen, there are hydrocarbon fuels for fuel cells, including diesel, methanol (see: direct-methanol fuel cells) and chemical hydrides. The waste products with these types of fuel are carbon dioxide and water.
The materials used in fuel cells differ by type. The electrode/bipolar plates are usually made of metal, nickel or carbon nanotubes, and are coated with a catalyst (like platinum, nano iron powders or palladium) for higher efficiency. Carbon paper separates them from the electrolyte. The electrolyte could be ceramic or a membrane.
A typical fuel cell produces about 0.86 volt. To create enough voltage, the cells are layered and combined in series and parallel circuits to form a fuel cell stack. The number of cells used is usually greater than 45 but varies with design.
Fuel cell design problems
- Costs. In 2002, typical cells had a catalyst content of USD $1000 per kilowatt of electric power output. The goal is to reduce the cost in order to compete with current market technologies including gasoline internal combustion engines. Many companies are working on techniques to reduce cost in a variety of ways including reducing the amount of platinum needed in each individual cell. Ballard Power Systems have experiments with a catalyst enhanced with carbon silk which allows a 30% reduction (1 mg/cm² to 0.7 mg/cm²) in platinum usage without reduction in performance.[2]
- The production costs of the PEM (proton exchange membrane). The Nafion® membrane currently costs €400/m². This, and the Toyota PEM and 3M PEM membrane can be replaced with the ITM Power membrane (a hydrocarbon polymer), resulting in a price of ~€4/m². One of the bigger companies is using Solupor® (a porous polyethylene film).[3]
- Water management (in PEMFCs). In this type of fuel cell, the membrane must be hydrated, requiring water to be evaporated at precisely the same rate that it is produced. If water is evaporated too quickly, the membrane dries, resistance across it increases, and eventually it will crack, creating a gas "short circuit" where hydrogen and oxygen combine directly, generating heat that will damage the fuel cell. If the water is evaporated too slowly, the electrodes will flood, preventing the reactants from reaching the catalyst and stopping the reaction. Methods to manage water in cells are being developed by fuel cell companies and academic research labs.
- Flow control. Just as in a combustion engine, a steady ratio between the reactant and oxygen is necessary to keep the fuel cell operating efficiently.
- Temperature management. The same temperature must be maintained throughout the cell in order to prevent destruction of the cell through thermal loading.
- Durability, service life, and special requirements for some type of cells. Stationary applications typically require more than 40,000 hours of reliable operation at a temperature of -35 °C to 40 °C, while automotive fuel cells require a 5,000 hour lifespan (the equivalent of 150,000 miles) under extreme temperatures. Automotive engines must also be able to start reliably at -30 °C and have a high power to volume ratio (typically 2.5 kW per liter).
- Limited carbon monoxide tolerance of the anode.
Source: wikipedia.org
