2 The fuel cell is a unique power converter That is efficient, nonpolluting, and flexible.For many, it is the technology that will weanUs from our strong dependence uponImported oil, especially the transportation sector.It combines a fuel (usually natural gas or hydrogen)With oxygen from the air by an electrochemicalProcess to produce electricity.
3 Fuel cells are being developed to power passenger Vehicles, commercial buildings, homes, andEven small devices such as laptop computers.These systems are effective over a large rangeOf sizes, from 1kW to hundreds of MW, withOver all efficiencies of 80% or more!(when heat production is combined withThe power generation)They are clean, highly reliable (no moving parts),And offer a unique opportunity for energyIndependence.
4 The fuel cell was invented more than a hundred Years ago, but didn’t come of age inThe 1970’s when it was first used on space missions.They offer a large power-to-weight ratio,Compactness, and reliability.This makes it a popular power source for suchUses as vehicle propulsion, andSmall scale electric facilities.
5 The high cost of fuel cells and future Unknowns have hindered their commercialization.The present price of about $4000 per kilowattCan be offset by fading government grants.In its most basic form, it is a batteryThat has a constant supply of fuel toAlways “recharge” it.It provides direct current through anElectro-chemical process.
6 H2 + ½ 02 H22+ 02- + energy The 2 chemical reactants in a fuel cell Are generally hydrogen and oxygen, whichAre fed into the cell throughPorous electrodes.The fuel cell reaction can be thought of asA very slow hydrogen gas combustion process.H2 + ½ 02 H energy
7 In a fuel cell the electrons are transferred Slowly to the oxygen via an external circuit.At the positive electrode, hydrogen atoms areStripped of their electrons and enter into theElectrolyte.At the negative electrode, the hydrogen ionsCombine with the oxygen atoms and electrons toForm water and heat.
8 The electrons flow through an external circuit Connecting the electrodes.The net result is the reaction ofOxygen and hydrogen to formWater.
10 There are 5 different types of fuel cells that Are in research, testing, or development stages.The proton exchange membrane (PEM), theMolten carbonate cell, the solid-oxide ceramicCells are all in the demonstration stage.The phosphoric acid cell has been operatedIn a commercial size of 200 kW and testedWith an 11MW unit.
11 The alkaline process has been used by NASA in its space program, in theGemini space capsules in the 1960s.
12 The phosphoric acid cell (PAFC) is considered to Be the “1st” generation of fuel cells.It was also the first to be used commerciallyWith over 200 units currently in use.They are usually used for stationary power generationSince they are heavy.They are 85% efficient when used forElectricity and heat.
13 Polymer electrolyte membrane (PEM) fuel cells Deliver high power density and are lower inWeight compared to other types.PEM uses a solid polymer as an electrolyte andPorous carbon electrodes containing a platinum catalyst.They require only hydrogen, oxygen from the airAnd water to operate.Can also use methane and methanol but aFuel processor is necessary.These are the most popular choice for smallElectronics and vehicle propulsion.
15 Alkaline fuel cells were the first to be used in the Space program to produce electricity andOnboard spacecraft.They use a solution of potassium hydroxide inWater as the electrolyte and a variety of preciousMetals as the anode and cathode.They have demonstrated efficiencies asHigh as 60%.
16 Molten metal carbonate fuel cells use an Electrolyte of molten carbonate salt mixture inA porous, chemically inert ceramic lithiumAluminum oxide (LiAlO2).They operate at a high temperature, so theyCan use lower quality fuels.Efficiencies reach 60%.
17 Solid Oxide fuel cells (SOFC) use a hard, nonporous Ceramic compound as the electrolyte, allowingSolid construction.These also operate at a very high temperature,So they require a long start up time, makingThem more suitable for stationary functions.Efficiencies of around 50%.
19 Direct methanol fuel cell (DMFC) And regenerative fuel cells. There are more types:Direct methanol fuel cell (DMFC)And regenerative fuel cells.Methanol uses methanol, which has aHigher energy density than H2.Regenerative fuel cells use solar panels toSplit water through electrolysis and useThose gases to run the fuel cell.
20 The fuel stack is the heart of the system. A single cell produces only about 1 volt DC andA small current.Therefore, fuel cells use layers of cells toProduce the desired voltage and current needed.
21 The costs of fuel cells are not yet competitive with Conventional power technologies.In general, they are $30/kW, so theyCannot replace the ICE.At the moment, there are only a handful ofFuel cell systems in the U.S.The largest one being in Anchorage, Alaska.
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