Module 08
(subjected to continual revision)
Fuel cells
Energy storage
Hydrogen economy
Other alternatives to energy use
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell It combines hydrogen and oxygen to produce electricity via an electrochemical process.
H
2 is split at anode
H
2
2H
+
+ 2e
-
Mar 03, 2012
Exhaust is water
(not CO
2)
O
2 is split at cathode (hard)
2H
+
+ 2e
+ ½ O
2
H
2
O
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
Mar 03, 2012

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
Mar 03, 2012

Fuel Cell Hybrid
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

Fuel Cell Type
PEMFC - Polymer Electrolyte Membrane Fuel Cells
(or Proton Exchange Membrane Fuel Cells )
DMFC - Direct Methanol Fuel Cells
AFC
PAFC
- Alkaline Fuel Cells
- Phosphoric Acid Fuel Cells
MCFC - Molten Carbonate Fuel Cells
SOFC - Solid Oxide Fuel Cells
Prof. R. Shanthini
Mar 03, 2012

Proton Exchange Membrane Fuel Cell (PEMFC)
- H
2 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 H
2 to split into positive hydrogen ions
(protons) and negatively charged electrons.
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

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
Mar 03, 2012

Proton Exchange Membrane Fuel Cell (PEMFC)
- Pt/C electrodes are too expensive to replace internal combustion engines.
- H
2
(produced from light hydrocarbons) contains 1-3%
CO, 19-25% CO
2
N
2
.
and 25%
- Even 50 ppm of CO poisons a Pt catalyst.
- Pure H
2 is used as fuel, which is costly.
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

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
CH
3
OH + H
2
O 6H
+
+ 6e
-
+ CO
2
CO
2
H
+
Air
Prof. R. Shanthini
Mar 03, 2012
6H
+
+ 6e
+ 1½ O
2
3H
2
O
Water +
Excess air

Direct Methanol Fuel Cell (DMFC)
- Operates at about 50-90 o C
- Efficiency is about 40%
- Used more for small portable power applications, possibly cell phones and laptops
Prof. R. Shanthini
Mar 03, 2012
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
Mar 03, 2012

Alkaline Fuel Cell (AFC)
- Pure H
2 and O
2 because it is very susceptible to carbon contamination
- Purification process of the H
2 and O
2 is costly
- Susceptibility to poisoning affects cell’s lifetime which also affects the cost
- Considered to costly for transportation applications
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

Phosphoric Acid Fuel Cell (PAFC)
- Efficiency is about 40%
- Operates at about 150-220 o C
- One main advantage is that it can use impure hydrogen
(with less that 1.5% CO) as fuel
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

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
Mar 03, 2012

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
Mar 03, 2012

Fuel Cell Type
Fuel cell type
PEMFC
Operating
Temp ( o C)
Efficiency
50-120 40-50
Domestic power

Suitable applications
Smallscale power

Largescale
X
Transport

AFC 50-90 50-70
 
X

PAFC
MCFC
SOFC
150-220
600-650
40-45
50-60
800-1000 50-60
X
X




X


X
X
X
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell Hydrogen from steam reforming:
95% of the usage
Prof. R. Shanthini
Mar 03, 2012
HTS – High temperature shift
LTS – Low temperature shift

Fuel Cell Hydrogen from steam reforming:
95% of the usage
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:
CH
4
+ H
2
O → CO + 3 H
2
+ 191.7 kJ/mol
Shift conversion at 130 °C:
CO + H
2
O → CO
2
+ H
2
- 40.4 kJ/mol
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell Hydrogen from natural gas steam reforming:
95% of the usage per kg of H
2 produced:
GHG emissions: 10621 g CO
2
, 60 g CH
4 and 0.04 g N
2
O
GWP : 11.88 kg CO
2 eq.
Resource required : 159 g coal, 10.3 g Fe (ore),
11.2 g Fe (scrap),16.0 g CaCO
3
,
3642 g natural gas and 16.4 g of oil
Water consumption:
Energy consumption:
19.8 litres
183.2 MJ
Solid waste generated: 201.6 g
0.66 MJ of H
2 is produced per MJ of fossil fuel consumed.
Prof. R. Shanthini
Mar 03, 2012 http://www.nrel.gov/hydrogen/energy_analysis.html

Fuel Cell Hydrogen from electrolysis:
5% of the usage
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell Hydrogen from electrolysis:
5% of the usage
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell per kg of H
2
Hydrogen from electrolysis of water using wind electricity:
5% of the usage produced:
GHG emissions: 950 g CO
2
, 0.3 g CH
4 and 0.05 g N
2
O
GWP : 0.97 kg CO
2 eq.
Resource required : 214.7 g coal, 212.2 g Fe (ore),
174.2 g Fe (scrap),366.6 g CaCO
3
,
16.2 g natural gas and 48.3 g of oil
Water consumption:
Energy consumption:
26.7 litres
9.1 MJ
Solid waste generated: 223 g
13.2 MJ of H
2 is produced per MJ of fossil fuel consumed.
Prof. R. Shanthini
Mar 03, 2012 http://www.nrel.gov/hydrogen/energy_analysis.html

Regenerative Fuel Cell
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

Fuel Cell Hydrogen from water-splitting:
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

Fuel Cell
Prof. R. Shanthini
Mar 03, 2012

Fuel Cell Hydrogen from waste:
HyPR-MEET demonstration plant
Concept of the gasification
Prof. R. Shanthini
Mar 03, 2012 system

Fuel Cell Hydrogen from waste:
Prof. R. Shanthini
Mar 03, 2012 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
Mar 03, 2012 http://www.solutions-site.org/node/294

Microbial
Fuel Cells
Prof. R. Shanthini
Mar 03, 2012 Source: http://parts.mit.edu/igem07/images/2/2d/Fuelcell.JPG

Microbial
Fuel Cells anode cathode
Prof. R. Shanthini
Mar 03, 2012 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
Mar 03, 2012

Microbial
Fuel Cells
Microbes growing in the anodic chamber metabolize a carbon substrate (glucose in this case) to produce energy and hydrogen.
Prof. R. Shanthini
Mar 03, 2012

Microbial
Fuel Cells
C
6
H
12
O
6
C
6
H
12
O
6
+ 2H
2
O → 2CH
3
COOH + 2CO
2 or
→ CH
3
CH
2
CH
2
COOH + 2CO
2
+ 4H
+ 2H
2
2
Prof. R. Shanthini
Mar 03, 2012
Hydrogen generated is reduced into hydrogen ions
(proton) and electrons.

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
Mar 03, 2012

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
Mar 03, 2012

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.
The cathodic chamber may be filled with air in which case oxygen is the oxidant.
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

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
Mar 03, 2012

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/m 2 , depending on the type of cellulose.
Prof. R. Shanthini
Mar 03, 2012

Microbial
Fuel Cells
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
Mar 03, 2012

Prof. R. Shanthini
Mar 03, 2012

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).
Prof. R. Shanthini
Mar 03, 2012

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
Mar 03, 2012

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
Prof. R. Shanthini
Mar 03, 2012
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
Mar 03, 2012 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
Mar 03, 2012 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
Mar 03, 2012 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 (-120 o C to -196 o C).
Prof. R. Shanthini
Mar 03, 2012 http://www.kentlaw.edu/ faculty/fbosselman/class es/EnergyLawSp07/Pow erPoints/BonnettFuelCell PresentationFinal.ppt

How can Fuel Cell Technology be used?
- 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
Mar 03, 2012 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
Mar 03, 2012 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 auxiliary power units which meet the plane's power demands when the plane is on the ground.
Prof. R. Shanthini
Mar 03, 2012

How can Fuel Cell Technology be used?
Fuel Cell Powered Trains:
Visit http://hydrail.org/
Prof. R. Shanthini
Mar 03, 2012

How can Fuel Cell Technology be used?
Fuel Cell Powered Buses:
Prof. R. Shanthini
Mar 03, 2012
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
Mar 03, 2012

How can Fuel Cell Technology be used?
Telecommunications:
Prof. R. Shanthini
Mar 03, 2012

How can Fuel Cell Technology be used?
Micro Power:
Prof. R. Shanthini
Mar 03, 2012

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 copper-platinum 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
Mar 03, 2012 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
Mar 03, 2012 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
Mar 03, 2012 http://www.understandingnano.com/fuel_cells-platinum-reactivity-lattice-strain.html

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
Mar 03, 2012 http://www.nap.edu/catalog/10922.html

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
Mar 03, 2012 http://www.nap.edu/catalog/10922.html