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who you know
hydrogen power of
from the Sun and throughout the universe 0
that's the most plentiful element no to humanity
they were just beginning to harness its power fuel cells
clean energy for the future of
of
by I'm Ira Flatow 07 PR Science Friday
and I'm here today to share with you what we know about fuel cells
but first just imagine for a moment
energy source that could literally prevent millions of tons of emissions
from polluting our air was significantly reducing our dependence on imported oil
a supply of power so clean so quiet
so safe and it could be located right in the middle of populated cities
or even in your own backyard device with no moving parts
the power everything from an electric utility
to a motor scooter it might sound like fantasy
but it's not it's a future just around the corner
and it's called the fuel safe
Sir William growth this well scientists built the first fuel sale in 1839
but it wasn't until 1950 that another British scientist
Francis Bacon demonstrated its practical use
any fuel cell stack only then did the fuel cell begin to take off
with the US manned space program building and bacon success
let's see how it works like a battery
fuel cell has the electrodes and electrolyte and produces electricity
unlike a battery a fuel cell doesn't store energy
it produces power as long as hydrogen and oxygen are supply
refueling not recharging is needed
this is what happens hydrogen fuel is fed to the anode
upon contact electrons are free
beginning the flow of electricity the hydrogen ions then travel across the
electrolyte
to the cathode where they we combined with free electrons and with oxygen
forming
electricity water and heat are released
as byproducts in certain types of fuel cells other ions travel from cathode to
anode instead I've
anode to cathode but nevertheless the premise
remains the same that electricity is generated
through an electrochemical reaction by combining hydrogen
and aXIGEN to form water
you also create electricity
with no combustion whatsoever and this is what makes it so clean
in addition to high efficiencies and lower emissions
one of the most attractive features a fuel cells is there my jewel arity
fuel cell stacks consistent individual cells
which are repeated until the desired power output is reached
to change the output you just increase or decrease the number of cells
in a typical fuel cell a rip bipolar separator plate axes a gas manifold
provides the electrical connection between the sales
and creates a gas barrier keeping the fuel in air streams in their respective
compartments
there are five major types of fuel cells
each using different electrolytes an operating at different temperatures
each is well suited for specific markets
today we'll talk about the following fuel cells
alkaline phosphoric acid
proton exchange membrane solid oxide
and the molten carbonate fuel cell
the most successful application of alkaline fuel cells
has been in the US space program providing electricity and drinking water
to all manned space mission since apollo in the late sixties
the alkyl in fuel cell uses only pure hydrogen in pure oxygen
because if its sensitivity to carbon dioxide contamination its electrolyte
consists if I highly conductive potassium hydroxide
its be electrodes consisted of crystallite structures
with gold plated nickel mesh conductors card research is focusing on terrestrial
applications
including lower cost components operation in near ambient temperature
and pressure
and using simple air as the accident when other fuel cells
don't be choir pure hydrogen but can use hydrogen rich fuels
such as methanol or natural gas but
first the fuel must be processed one method is called the steam reforming
process
here's how it works first unused hydrogen from the fuel cell
is mixed with care and burn to heat the catalyst
up
fuel and water are 10 vaporized using the fuel sales by product heap
mixture flows through the catalyst bed which accelerates the chemical reaction
producing carbon dioxide in hydrogen
phosphoric acid fuel cell
is the most commercially developed it can operate on a variety a reformed
hydrocarbon fuels
and uses ambient air to provide the aXIGEN it's already being used to
generate power for hospitals
hotels
and office buildings among others
and its application goes beyond stationary power generation
recently a phosphoric acid fuel cell bus was built by the US Department of Energy
the US Department of Transportation and california's south coast Air Quality
Management District
a next-generation forty-foot fuel cell bus
is currently under development by the US Department of Transportation
and is being considered for use in a large fleet
here's what's so exciting about fuel cells and transportation
compared with diesels the bus produces only half the greenhouse gases
250 times fewer carbon monoxide
practically no nitrogen oxides and 0 particulars
as with all fuel cells the lack of moving parts
will significantly reduce maintenance this kind of clean fuel cell driven
vehicle
is ideally suited for urban transit operations
and there are a number of other fuel cell vehicles being built today
by various manufacturers are also undergoing row tests
phosphoric acid fuel cells operate at more than 40 percent efficiency
and nearly eighty-five percent if the heat by product
is used for cogeneration this fuel cell operates effectively at ambient pressure
in a moderately low temperatures near 400 degrees Fahrenheit
the future of fuel cells and transportation
is well worth watching
the proton exchange membrane fuel cell
or ham has been demonstrated in buses and vans
anne's the prime candidate for passenger car application
currently holds the greatest promise for reaching the
18 miles per gallon goal set by the government
industry partnership for a new generation a vehicle
and it's expected to do this of
far exceeding clean air requirements the world's automakers
including the US big three are actively pursuing its development the Pens low
operating temperature
about 200 degrees Fahrenheit and high power density
make it quite suitable for automobiles where quick startup is required as with
the phosphoric acid fuel cell the Pam can use hydrogen rich gas
from reform fuels but first most to be carbon monoxide
must be removed its most efficient operation occurs at higher pressures
development is continuing to help broadened its efficient operation
under a variety of conditions the proton exchange membrane fuel cell differs from
others
that uses a salad proton conducting Electra life
but unlike household plastic wrap take
this a mobile rather than liquid electrolyte simplify ceiling in the
production process
reduces corrosion and is expected to extend cell life
studies have concluded that these qualities give the pen fuel cell system
the potential to be comparable in cost to current internal combustion engines
both solid oxide and molten carbonate fuel sales
operate at much higher temperatures making the internal processing up
hydrocarbon fuels possible
further simplifying the system and reducing costs
because of the improved economics solid oxide fuel cells
are showing promise for applications such as industrial and electric
generating stations
already 225 kilowatt demonstration units
are being tested in Japan with 120 kilowatt unit operating in southern
california
solid oxide systems use a ceramic electrolyte allowing temperatures to
reach
1800 degrees Fahrenheit power generating efficiencies
up to 45 percent have a demonstrated an overall system efficiency
is much higher in applications which take advantage
up the heat by product through cogeneration solid oxide fuel cells are
configured in plainer stacks
or in monolithic or tubular structures a typical tubular sale
insist 75 basic components a porous ceramic support to
cathode a solid electrolyte
in an old and electronically conducting interconnection
air flows through the centre beach to well gaseous fuel babysit exterior
in the monolithic solid oxide fuel cell
each electrode is comprised of a corrugated layer
fuse 22 flat layers a solid electrolyte is sandwiched between the two electrodes
as fuel and air flow through the car gated channels
the electrochemical reaction releases electrons
starting the flow of current although more difficult to fabricate
the monolithic fuel cell configuration is projected to have a higher power
density
and either tubular or plainer solid oxide fuel cells
of
the molten carbonate fuel cell is currently in the final stages of
prototype testing
for utility power generation like this solid oxide
the molten carbonate fuel cell also promises high fuel efficiencies
and low emissions because have high operating temperatures
around 1200 degrees Fahrenheit because of their high temperatures
these fuel cells are also well suited for cogeneration applications
both systems are ideal where electricity and heat are needed
on a continuous basis the molten carbonate electrolyte is made of a
mixture of
potassium and lithium carbonate switch when melted
become I am ically conductive similar to the solid oxide monolithic structure
the molten carbonate fuel cell as these car a gated flow channels for fuel and
air
but here they're made of stainless steel well the electrodes themselves are made
of porous nickel
and nickel oxide again because I've high temperatures
the molten carbonate and solid oxide fuel cells
eliminate the need for higher cost platinum catalysts
used in lower temperature fuel cells these fuel cells are inherently simpler
and potentially more cost-effective another advantage is that carbon
monoxide
considered a catalyst poisoning other fuel cells can be used directly in the
sale
providing additional fuel and further simplifying the system
so how good is this efficient and clean machine the fuel cell
weather for stationary operation or for transportation
fuel cell far surpasses any other energy conversion device
in its purity operational compared with any
current internal combustion engine emissions with fuel cells
using hydrocarbons are minute
and when the fuel sailors fueled with pure hydrogen
pollutants are literally of Sierra
and compared with existing turbines and other internal combustion engines
fuel cells generate electricity at far higher efficiencies
fuel cells are here today and more and more will become part of our everyday
lines
isn't it time we learned more about them Subtitles End: mo.dbxdb.com