May 2013 by; OM PRAKASH MEENA PANKAJ PINGOLIYA RAKESH JOTAR

Overview  Introduction  Hydrogen full cells  Production of hydrogen  Advantage of hydrogen fuel  Disadvantages of hydrogen fuel  Hydrogen vehicles

Fossil fuels (i.e. Petroleum, Natural gas, coal ) which are meet most of the world’s energy demand today, are being depleted rapidly. Also their combustion products are causing global problems, such as the Green house effect, ozone layer depletion, acid rain and pollution,which are posing great danger for our environment and eventually, for the total life on our planet. All the these problems can be remove by the uses of hydrogen fuel. hydrogen is a very efficient and clean fuel. Its combustion will produce no Green house gases, no ozone depletion chemicals and little or no acid rain ingredients and pollution. Hydrogen produce from renewable energy (solar, wind etc.) sources, would result in a permanent energy system which would never have to be changed. The most common source of hydrogen is water. Hydrogen fuel does not produce harmful carbon content and harmful gases.

Types of Fuel Cells  Alkaline Fuel Cell (AFC)  Molten Carbonate Fuel Cell (MCFC)  Phosphoric Acid Fuel Cell (PAFC)  Proton Exchange Membrane Fuel Cell (PEMFC)  Solid Oxide Fuel Cell (SOFC)  Direct Methanol Fuel Cell  Fuel cell types are generally characterized by electrolyte material. The electrolyte is the substance between the positive and negative terminals, serving as the bridge for the ion exchange that generates electrical current.

What is a hydrogen fuel cell?  Hydrogen fuel cells (HFCs) are a type of electrochemical cell. HFCs generate electricity by reduction and oxidation reactions within the cell. They use three main components, a fuel, an oxidant and an electrolyte. HFCs operate like batteries, although they require external fuel. HFCs are a thermodynamically open system. HFCs use hydrogen as a fuel, oxygen as an oxidant, a proton exchange membrane as an electrolyte, and emit only water as waste.

How do they work ? Fuel (H 2 ) is first transported to the anode of the cell Fuel undergoes the anode reaction Anode reaction splits the fuel into H + (a proton) and e - Protons pass through the electrolyte to the cathode Electrons can not pass through the electrolyte, and must travel through an external circuit which creates a usable electric current Protons and electrons reach the cathode, and undergo the cathode reaction

Chemistry behind the technology Oxidation At the anode of the cell, a catalyst (platinum powder) is used to separate the proton from the electron in the hydrogen fuel. Anode half-reaction: 2H 2  4H + + 4e - E o = 0.00V Reduction At the cathode of the cell, a second catalyst (nickel) is used to recombine the protons, electrons, and oxygen atoms to form water. Cathode half- reaction: 4H + + O 2 + 4e -  2H 2 O E o = 0.68V In electrochemistry, the E o cell value (energy) of a fuel cell is equal to the E o of the cathode half-reaction minus the E o of the anode half-reaction. For a hydrogen fuel cell, the two half reactions are shown above. So to calculate the energy of one fuel cell, we need to subtract the anode energy from the cathode energy. For a HFC, the E o cell = 0.68V – 0.00V which equals 0.68V

Alkaline Fuel Cells  Molten KOH as electrolyte  Conducts OH- from cathode to anode  Circulating electrolye, removes heat and water/or a stationary paste needs H 2 + 2OH - → 2H 2 O + 2e- 1/2O 2 + H 2 O + 2e- → 2OH - Removal of water is critical

Advantages  Low temp  Fast start up  High efficiency  Little or no platinum catalyst needed  Minimal corrosion

Production of hydrogen Hydrogen mainly produced from-  From Fossil fuels  From water

Production from fossil fuels  Coal -converted to mixture of hydrogen (50%), methane (35%), and carbon monoxide (8%)  Steam Reforming Methane (SRM) -Most efficient, widely used, and cheapest  Partial Oxidation -Range of feed stocks, 75% SRM  Directly cracking Methane or other hydrocarbons

Production from water  Electricity + H 2 O → H 2 + O + H 2 O (steam)  Large-scale units using alkaline electrolyte can run at 70–75% efficiency (EE - H 2 )  Smaller systems with polymer electrolytes reach 80–85% efficiency (EE - H 2 )  Steam electrolyzers in development may be able to reach 90% efficiency (EE - H 2 )

Uses of hydrogen fuel cells There are many different uses of fuel cells being utilized right now. Some of these uses are… Power sources for vehicles such as cars, trucks, buses and even boats and submarines Power sources for spacecraft, remote weather stations and military technology Batteries for electronics such as laptops and smart phones Sources for uninterruptable power supplies.

Advantages of hydrogen fuel  Clean; only product is H 2 O and heat.  More efficient than heat engine.  Higher part load efficiency  Excellent response time  Co-generation  No recharging required  Does not produce harmful gases  It produce nitrous oxide that can be used in nitrous system

Disadvantages of hydrogen fuel  H 2 is difficult/expensive to produce, store and transport.  Fuels cells require pure fuel.  Platinum catalysts are expensive and rare  Proton exchange membranes must be kept moist  Hydrogen fuel cell stacks are heavy  It produce nitrous oxide that causes for acid rain  It produce small amount of carbon di oxide

Conclusion  Hydrogen fuel cells will dramatically change our cars, how are homes and businesses are powered and heated, and it both positively and negatively change places like the Middle East and third world countries. They will also clean up the world’s air.

Thank You