Transcript Document

Module 08
(subjected to continual revision)
New and Emerging Energy Technologies
Fuel cells
Energy storage
Hydrogen economy
Other alternatives to energy use
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
It combines hydrogen and oxygen to produce
electricity via an electrochemical process.
H2 is
split at
anode
O2 is split at
cathode (hard)
H2
+
2H+ + 2e- + ½ O2
-
2H + 2e
Prof. R. Shanthini
09 Feb 2013
Exhaust is water
(not CO2)
H2O
It works quietly.
Fuel Cell
- Individual fuel cells can be placed in a series to form a
fuel cell stack.
- The stack can be used in a system to power a vehicle or
to provide stationary power to a building.
Prof. R. Shanthini
09 Feb 2013
Fuel Cell Car
- At a steady cruising speed,
the motor is powered by
energy from the fuel cell.
- When more power is
needed, for example during
sudden acceleration, the
battery supplements the
fuel cell’s output.
- At low speeds when less power is required, the vehicle runs on
battery power alone.
- During deceleration the motor functions as an electric generator
to capture braking energy, which is stored in the battery.
Prof. R. Shanthini
09 Feb 2013
Fuel Cell Hybrid
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
- All fuel cells have the same basic configuration - an
electrolyte and two electrodes.
- Fuel cells are classified by the kind of electrolyte used.
- The type of electrolyte used determines the kind of
chemical reactions that take place and the temperature
range of operation.
Prof. R. Shanthini
09 Feb 2013
Fuel Cell Type
PEMFC
- Polymer Electrolyte Membrane Fuel Cells
(or Proton Exchange Membrane Fuel Cells )
DMFC
- Direct Methanol Fuel Cells
AFC
- Alkaline Fuel Cells
PAFC
- Phosphoric Acid Fuel Cells
MCFC
- Molten Carbonate Fuel Cells
SOFC
- Solid Oxide Fuel Cells
Prof. R. Shanthini
09 Feb 2013
Proton Exchange Membrane Fuel Cell (PEMFC)
- H2 is the fuel for PEMFC.
- Proton exchange polymer
membrane (PEM) is used as
electrolyte.
- Platinum particles on carbon
(Pt/C) is used as electrodes.
- At the anode, a platinum
catalyst causes the H2 to split
into positive hydrogen ions
(protons) and negatively
charged electrons.
Prof. R. Shanthini
09 Feb 2013
Proton Exchange Membrane Fuel Cell (PEMFC)
- PEM allows only the
positively charged hydrogen
ions to pass through it to the
cathode.
-The negatively charged
electrons must travel along an
external circuit to the cathode,
creating an electrical current.
- At the cathode, the electrons
and positively charged
hydrogen ions combine with
oxygen to form water, which
flows out of the cell.
Prof. R. Shanthini
09 Feb 2013
Proton Exchange Membrane Fuel Cell (PEMFC)
- Suited for applications where
quick startup is required making
it popular for automobiles
- Used in the NASA Gemini
series of spacecraft
Prof. R. Shanthini
09 Feb 2013
Proton Exchange Membrane Fuel Cell (PEMFC)
- Pt/C electrodes are too
expensive to replace internal
combustion engines.
- H2 (produced from light
hydrocarbons) contains 1-3%
CO, 19-25% CO2 and 25%
N2.
- Even 50 ppm of CO poisons
a Pt catalyst.
- Pure H2 is used as fuel,
which is costly.
Prof. R. Shanthini
09 Feb 2013
Proton Exchange Membrane Fuel Cell (PEMFC)
- Electrolytes were sulfonated
polystyrene membranes
- Nafion is used as electrolytes
now
- Nafion is a sulfonated
tetrafluoroethylene based
fluoropolymer-copolymer
discovered in the late 1960s by
DuPont.
Prof. R. Shanthini
09 Feb 2013
Direct Methanol Fuel Cell (DMFC)
- Polymer membrane is used as electrolyte as in PEMFC.
- Pt/C is used as electrodes as in PEMFC.
- Anode is able to draw hydrogen from methanol directly,
unlike in PEMFC.
Methanol
+ water
6H+ + 6e- + CO2
CO2
CH3OH + H2O
H+
Air
6H+ + 6e- + 1½ O2
Prof. R. Shanthini
09 Feb 2013
3H2O
Water +
Excess air
Direct Methanol Fuel Cell (DMFC)
- Operates at about 50-90oC
- Efficiency is about 40%
- Used more for small portable power applications, possibly
cell phones and laptops
Prof. R. Shanthini
09 Feb 2013
Toshiba
Corporation
Alkaline Fuel Cell (AFC)
- Potassium hydroxide in water
is used as the electrolyte
- A variety of non-precious
metals can be used as catalyst
at the electrodes
- Can reach up to 70% power
generating efficiency
- Used mainly by military and
space programs
- Used on the Apollo spacecraft
to provide electricity and
drinking water
Prof. R. Shanthini
09 Feb 2013
Alkaline Fuel Cell (AFC)
- Pure H2 and O2 because it is
very susceptible to carbon
contamination
- Purification process of the H2
and O2 is costly
- Susceptibility to poisoning
affects cell’s lifetime which also
affects the cost
- Considered to costly for
transportation applications
Prof. R. Shanthini
09 Feb 2013
Phosphoric Acid Fuel Cell (PAFC)
- Uses highly concentrated or
pure liquid phosphoric acid as
electrolyte
- This acid is saturated in a
silicon carbide matrix (SiC)
- Uses Pt/C electrodes
- Most commercially developed
fuel cell
- Installed and currently
operating in banks, hotels,
hospitals and police stations.
Prof. R. Shanthini
09 Feb 2013
Phosphoric Acid Fuel Cell (PAFC)
- Efficiency is about 40%
- Operates at about 150-220oC
- One main advantage is that it
can use impure hydrogen
(with less that 1.5% CO) as
fuel
Prof. R. Shanthini
09 Feb 2013
Molten Carbonate Fuel Cell (MCFC)
- Uses an electrolyte
composed of a molten
carbonate salt mixture
- Require carbon dioxide
and oxygen to be
delivered to the cathode
- Operates at extremely
high temperatures
- Primarily targeted for use
as electric utility
applications
Prof. R. Shanthini
09 Feb 2013
Molten Carbonate Fuel Cell (MCFC)
- Because of the extreme high
temperatures, non-precious
metals can be used as
catalysts at the anode and
cathode which helps
reduces cost
- Disadvantage is durability
- The high temperature
required and the corrosive
electrolyte accelerate
breakdown and corrosion
inside the fuel cell
Prof. R. Shanthini
09 Feb 2013
Solid Oxide Fuel Cell (SOFC)
- Uses a hard, non-porous
ceramic compound as the
electrolyte
- Can reach 60% powergenerating efficiency
- Operates at extremely high
temperatures
- Used mainly for large, high
powered applications such as
industrial generating stations,
mainly because it requires
such high temperatures
Prof. R. Shanthini
09 Feb 2013
Fuel Cell Type
Fuel
cell
type
Suitable applications
Operating
Temp (oC)
Efficiency
Domestic
power
Smallscale
power
Largescale
Transport
PEMFC
50-120
40-50


X

AFC
50-90
50-70


X

PAFC
150-220
40-45
X

X
X
MCFC
600-650
50-60
X


X
SOFC
800-1000
50-60



X
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Prof. R. Shanthini
09 Feb 2013
Where do we get the
hydrogen from?
Fuel Cell
Hydrogen from steam reforming:
95% of the hydrogen used is produced this way
HTS – High temperature shift
Prof. R. Shanthini
09 Feb 2013
LTS – Low temperature shift
Fuel Cell
Hydrogen from steam reforming:
95% of the hydrogen used is produced this way
Bulk hydrogen is usually produced by the steam reforming of
natural gas (70-80% efficiency) or methane (lower efficiency):
Steam reforming at high temperatures (700–1100°C) with nickel
catalyst:
CH4 + H2O → CO + 3 H2 + 191.7 kJ/mol
Shift conversion at 130°C:
CO + H2O → CO2 + H2 - 40.4 kJ/mol
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Hydrogen from natural gas steam reforming:
95% of the hydrogen used is produced this way
per kg of H2 produced:
GHG emissions:
10621 g CO2, 60 g CH4 and 0.04 g N2O
GWP :
11.88 kg CO2 eq.
Resource required : 159 g coal, 10.3 g Fe (ore),
11.2 g Fe (scrap),16.0 g CaCO3,
3642 g natural gas and 16.4 g of oil
Water consumption:
19.8 litres
Energy consumption:
183.2 MJ
Solid waste generated:
201.6 g
0.66 MJ of H2 is produced per MJ of fossil fuel consumed.
Prof. R. Shanthini
09 Feb 2013
http://www.nrel.gov/hydrogen/energy_analysis.html
Fuel Cell
Hydrogen from electrolysis:
5% of the hydrogen used is produced this way
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Hydrogen from electrolysis:
hydrogen used is produced this way
Where does the power come from?
Wind
Solar PV
Other..
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Hydrogen from electrolysis of water using
wind electricity:
per kg of H2 produced:
GHG emissions:
950 g CO2, 0.3 g CH4 and 0.05 g N2O
GWP :
0.97 kg CO2 eq.
Resource required : 214.7 g coal, 212.2 g Fe (ore),
174.2 g Fe (scrap),366.6 g CaCO3,
16.2 g natural gas and 48.3 g of oil
Water consumption:
26.7 litres
Energy consumption:
9.1 MJ
Solid waste generated:
223 g
13.2 MJ of H2 is produced per MJ of fossil fuel consumed.
Prof. R. Shanthini
09 Feb 2013
http://www.nrel.gov/hydrogen/energy_analysis.html
Regenerative Fuel Cell
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Hydrogen from water-splitting:
Solar water splitting is the
process by which energy in
solar photons is used to
break down liquid water into
molecules of hydrogen and
oxygen gas.
Hydrogen produced through
solar water does not emit
carbon into the atmosphere.
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Prof. R. Shanthini
09 Feb 2013
Hydrogen from water-splitting:
Fuel Cell
Hydrogen from water-splitting:
Highly dense vertical arrays of nanowires made from
silicon and titanium oxide and measuring 20 microns in
height show promise for the efficient production of
hydrogen through solar water splitting.
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
Prof. R. Shanthini
09 Feb 2013
Fuel Cell
HyPR-MEET
demonstration
plant
Prof. R. Shanthini
09 Feb 2013
Hydrogen from waste:
Concept of the
gasification
system
Fuel Cell
Prof. R. Shanthini
09 Feb 2013
Hydrogen from waste:
http://www.nrel.gov/hydrogen/energy_analysis.html
Fuel Cell
Hydrogen from waste:
Researchers have designed a microbial
electrolysis cell in which bacteria break up acetic
acid (a product of plant waste fermentation) to
produce hydrogen gas with a very small electric
input from an outside source.
Hydrogen can then be used for fuel cells or as a
fuel additive in vehicles that now run on natural
gas.
Prof. R. Shanthini
09 Feb 2013
http://www.solutions-site.org/node/294
Microbial
Fuel Cells
Prof. R. Shanthini
09 Feb 2013
Source: http://parts.mit.edu/igem07/images/2/2d/Fuelcell.JPG
Microbial
Fuel Cells
anode
cathode
Prof. R. Shanthini
09 Feb 2013
Source: http://parts.mit.edu/igem07/images/2/2d/Fuelcell.JPG
Microbial
Fuel Cells
An anode and a cathode are
connected by an external
electrical circuit,
and separated internally
by an ion exchange
membrane.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
Prof. R. Shanthini
09 Feb 2013
Microbes growing in the anodic chamber
metabolize a carbon substrate (glucose in
this case) to produce energy and hydrogen.
Microbial
Fuel Cells
C6H12O6 + 2H2O → 2CH3COOH + 2CO2 + 4H2
or
C6H12O6 → CH3CH2CH2COOH + 2CO2 + 2H2
Hydrogen generated is
reduced into hydrogen ions
(proton) and electrons.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
Electrons are transferred to the anodic electrode,
and then to the external electrical circuit.
The protons move to the
cathodic compartment via
the ion exchange channel
and complete the circuit.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
The electrons and protons liberated in
the reaction recombine in the cathode.
If oxygen is to be used as
an oxidizing agent, water
will be formed.
An electrical current is
formed from the potential
difference of the anode
and cathode, and power
is generated.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
The anode and cathode electrodes are
composed of graphite, carbon paper or carbon
cloth.
The anodic chamber is filled
with the carbon substrate for
the microbes to metabolize to
grow and produce energy.
The pH and buffering
properties of the anodic
chamber can be varied to
maximize microbial growth,
energy production, and
electric potential.
Prof. R. Shanthini
09 Feb 2013
The cathodic chamber may
be filled with air in which case
oxygen is the oxidant.
Microbial
Fuel Cells
Laboratory substrates are acetate, glucose,
or lactate. Real world substrates include
wastewater and landfills.
Substrate concentration,
type, and feed rate can
greatly affect the efficiency
of a cell.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
Microbes should be anaerobic (fermentative
type) because anodic chamber must be free
of oxygen.
Microbes tested are:
E. coli
Proteus vulgaris
Streptococcus lactis
Staphylococcus aureus
Psuedomonas methanica
Lactobacillus plantarium
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
Microbes should be anaerobic (fermentative
type) because anodic chamber must be free
of oxygen.
Some bacteria, like
Clostridium cellulolyticum,
are able to use cellulose
as a substrate to produce
an electrical output
between 14.3-59.2
mW/m2, depending on the
type of cellulose.
Prof. R. Shanthini
09 Feb 2013
Microbial
Fuel Cells
Proton Exchange Membrane (PEM)
The PEM acts as the barrier between the anodic and
cathodic chambers.
It is commonly made from polymers like Nafion and
Ultrex.
Ideally, no oxygen should be able to circulate
between the oxidizing environment of the cathode
and the reducing environment of the anode.
The detrimental effects of oxygen in the anode can
be lessened by adding oxygen-scavenging species
like cysteine.
Prof. R. Shanthini
09 Feb 2013
Real-life MFC
Prof. R. Shanthini
09 Feb 2013
Real-life MFC
Prof. R. Shanthini
09 Feb 2013
The MFC shown in this tabletop setup can
take common sources of organic waste
such as human sewage, animal waste, or
agricultural runoff and convert them into
electricity (Biodesign Institute).
Real-life MFC
Fuel cells like this are now used by a
leading UK brewery to test the activity of
the yeast used for their ales.
Prof. R. Shanthini
09 Feb 2013
Real-life MFC
Prof. R. Shanthini
09 Feb 2013
The black boxes arranged in a ring of the
robot are MFCs, each generating a few
microwatts of power, enough to fuel a
simple brain and light-seeking behaviour in
EcoBot-II.
Storing the Hydrogen
Developing safe, reliable, compact and
cost-effective hydrogen storage is one of
the biggest challenges to widespread use
of fuel cell technology.
Prof. R. Shanthini
09 Feb 2013
http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt
Storing the Hydrogen
- Hydrogen has physical characteristics that make it difficult to
store large quantities without taking up a great deal of space.
- Hydrogen has a
very high energy
content by weight (3
times more than
gasoline) and a very
low energy content
by volume (4 times
less than gasoline).
Prof. R. Shanthini
09 Feb 2013
http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt
Storing the Hydrogen
- If the hydrogen is compressed and stored at room temperature
under moderate pressure, too large a fuel tank would be
required.
- Researchers are trying
to find light-weight, safe,
composite materials that
can help reduce the
weight and volume of
compressed gas
storage systems.
Prof. R. Shanthini
09 Feb 2013
http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt
Storing the Hydrogen
- Liquid hydrogen could be kept in a smaller tank than
gaseous hydrogen, but liquefying hydrogen is complicated
and not energy efficient.
- Liquid hydrogen is also extremely sensitive to heat and
expands significantly when warmed by even a few degrees,
thus the tank insulation required affects the weight and
volume that can be stored.
- If the hydrogen is compressed and cryogenically frozen it
will take up a very small amount of space requiring a smaller
tank, but it must be kept supercold (-120oC to -196oC).
Prof. R. Shanthini
09 Feb 2013
http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt
How can Fuel Cell Technology be used?
Transportation
- All major automakers are
working to commercialize a fuel
cell car.
- fuel cell buses are currently in
use in North and South America,
Europe, Asia and Australia
- Trains, planes, boats, scooters,
and even bicycles are utilizing
fuel cell technology as well
Prof. R. Shanthini
09 Feb 2013
http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt
How can Fuel Cell Technology be used?
Boeing Flies First Ever Hydrogen Fuel Cell Plane:
The experimental airplane climbed to an altitude of 1,000 m
above sea level using a combination of lithium-ion battery
power and power generated by hydrogen fuel cells.
After reaching the
cruise altitude,
batteries were
disconnected, and the
plane flew straight and
level at a cruising
speed of 100 km/h for
about 20 min on power
solely generated by the
fuel cells.
Prof. R. Shanthini
09 Feb 2013
http://www.treehugger.com/aviation/boeing-flies-first-ever-hydrogen-fuel-cell-plane.html
How can Fuel Cell Technology be used?
First Commercial Fuel Cell Powered Aircraft:
Airbus and the German Aerospace Center (DLR) presented
the first commercial aircraft powered by fuel cells at the ILA
Berlin Air Show 2008. The fuel cells cannot replace the
plane's jet engines for powering the heavy plane through
air.replace the
Fuelthe
cells
auxiliary power units
which meet the plane's
power demands when
the plane is on the
ground.
Prof. R. Shanthini
09 Feb 2013
How can Fuel Cell Technology be used?
Fuel Cell Powered Trains:
Visit http://hydrail.org/
Prof. R. Shanthini
09 Feb 2013
How can Fuel Cell Technology be used?
Fuel Cell Powered Buses:
Prof. R. Shanthini
09 Feb 2013
28 litres of Hydrogen /100 km
(compared to 52 litres diesel /100 km)
How can Fuel Cell Technology be used?
Stationary Power Stations:
Prof. R. Shanthini
09 Feb 2013
How can Fuel Cell Technology be used?
Telecommunications:
Prof. R. Shanthini
09 Feb 2013
How can Fuel Cell Technology be used?
Micro Power:
Prof. R. Shanthini
09 Feb 2013
Nanotechnology in Fuel Cells
- Platinum as cathode catalyst is strong enough to break the
oxygen bonds (molecule dissociation) but does not bind to
the free oxygen atoms too strongly (catalyst binding).
- But, cost is high.
- Platinum was combined with copper to create a copperplatinum alloy, and then the copper was removed from the
surface region of the alloy.
- Dealloyed platinum-copper catalyst was found to be more
reactive because the interatomic distance is changed by
dealloying.
- Thereby efficiency is increased.
Prof. R. Shanthini
09 Feb 2013
http://www.understandingnano.com/fuel_cells-platinum-reactivity-lattice-strain.html
Nanotechnology in Fuel Cells
- Depositing one nanometer thick layer of platinum and iron
on spherical nanoparticles of palladium.
- In laboratory scale testing, it was found that a catalyst
made with these nanoparticles generated 12 times more
current than a catalyst using pure platinum, and lasted ten
times longer.
Prof. R. Shanthini
09 Feb 2013
http://www.understandingnano.com/fuel_cells-platinum-reactivity-lattice-strain.html
Nanotechnology in Fuel Cells
- The researchers believe that the improvement is due to a
more efficient transfer of electrons than in standard
catalysts.
- Increasing catalyst surface area and efficiency by
depositing platinum on porous alumina
- Allowing the use of lower purity, and therefore less
expensive, hydrogen with an anode made of platinum
nanoparticles deposited on titanium oxide.
Prof. R. Shanthini
09 Feb 2013
http://www.understandingnano.com/fuel_cells-platinum-reactivity-lattice-strain.html
Hydrogen Economy
The vision of the hydrogen economy is based on two
expectations:
(1) that hydrogen can be produced from domestic
energy sources in a manner that is affordable and
environmentally benign, and
(2) that applications using hydrogen—fuel cell
vehicles, for example—can gain market share in
competition with the alternatives.
Prof. R. Shanthini
09 Feb 2013
http://www.nap.edu/catalog/10922.html
Hydrogen Economy
National Academy of Sciences, 2004.
The hydrogen economy: opportunities, costs, barriers,
and R&D needs.
Washington: The National Academies Press.
Available from http://www.nap.edu/catalog/10922.html
Prof. R. Shanthini
09 Feb 2013
http://www.nap.edu/catalog/10922.html