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MAT 1153 Alternative fuel technology. Chapter 5 - Hydrogen & Fuel Cell Vehicle. MOHD FAIRUS JAMID fairus@icam.edu.my. H ydrogen F uel C ells: T he power of tomorrow. W hat is a Fuel Cell?.
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MAT 1153 Alternative fuel technology Chapter 5 - Hydrogen & Fuel Cell Vehicle MOHD FAIRUS JAMID fairus@icam.edu.my
What is a Fuel Cell? • Is an electrochemical reactions device that combines hydrogen and oxygen to produce electricity, with water and heat as its by-product. • Unlike a battery, chemicals are not stored in the fuel cell; they must be replenished • Using a fuel and an oxidant • Possible fuel sources: hydrogen, alcohols, hydrocarbons, gasoline • Possible oxidants: oxygen, chlorine, chlorine dioxide
what is a fuel cell? Structural characteristics of PEMFC membranes
what is a fuel cell? • Anode (-) and Cathode (+) on each side of the fuel cell, divided by an electrolyte • Hydrogen gas is channeled through anode side; oxygen passes through cathode • Platinum catalyst oxidizes hydrogen atoms into H+ and electrons • Electrons pass along external circuit; conduct electricity before entering cathode • Electrolyte allows H+ to pass into the cathode • In cathode, catalyst combines H+ , O2- and electrons, forming H2O and heat
what is a fuel cell? • Anode:2H2 => 4H+ + 4e- • Cathode: O2 + 4H+ + 4e- => 2H2O • Net Reaction:2H2 + O2 => 2H2O • Exact opposite of electrolysis
what is a fuel cell? Fuel cell stack components
Construction of Hydrogen Fuel Cell Vehicle The P2000, zero-emission vehicle that utilizes a direct hydrogen polymer electrolyte fuel cell.
Types of Hydrogen Fuel Cells • Polymer Electrolyte Membrane (PEM) Fuel Cells • Direct Methanol Fuel Cells • Alkaline Fuel Cells • Phosphoric Acid Fuel Cells • Molten Carbonate Fuel Cells • Solid Oxide Fuel Cells • Regenerative Fuel Cells
Types of Hydrogen Fuel Cells Proton Exchange Membrane (PEM) • This is the leading cell type for passenger car application • Uses a polymer membrane as the electrolyte • Operates at a relatively low temperature, about 175 degrees • Has a high power density, can vary its output quickly and is suited for applications where quick startup is required making it popular for automobiles • Sensitive to fuel impurities.
Importance of Hydrogen Source • Hydrogen is a secondary energy resource, meaning it must be made from another fuel • Hydrogen can be produced from a wide variety of energy resources including: • Fossil fuels, such as natural gas and coal • Nuclear energy • Renewable resources, such as solar,water, wind and biomass
hydrogen production • The biggest challenge regarding hydrogen production is the cost • Reducing the cost of hydrogen production so as to compete in the transportation sector with conventional fuels on a per-mile basis is a significant hurdle to Fuel Cell’s success in the commercial marketplace • There are three general categories of Hydrogen production • Thermal Processes • Electrolyte Processes • Photolytic Processes • Thermal Processes • Natural Gas Reforming • Gasification • Renewable Liquid Reforming
hydrogen production • Natural Gas Reforming • Steam Methane Reforming • Hydrogen is produced from methane in natural gas using high-temperature steam • Methane reacts with the steam in presence of a catalyst to produce hydrogen • This process accounts for about 95% of the hydrogen used today in the U.S. • Partial oxidation • Produces hydrogen by burning methane in air • Gasification • Process in which coal or biomass is converted into gaseous components by applying heat under pressure and in the presence of steam • A subsequent series of chemical reactions produces a synthesis gas which reacts with steam to produce more hydrogen that can be separated
hydrogen production • Renewable Liquid Reforming • Biomass is processed to make renewable liquid fuels, such as ethanol or bio-oil, that are then reacted with high-temperature steam to produce hydrogen • This process is very similar to reforming natural gas • Electrolytic Processes • Electrolytic processes use an electric current to split water into hydrogen and oxygen • The electricity required can be generated by using renewable energy technologies such as wind, solar, geothermal and hydroelectric power • Photolytic Processes • Uses light energy to split water into hydrogen and oxygen • These processes are in the very early stages of research but offer the possibility of hydrogen production which is cost effective and has a low environmental impact
hydrogen storage • Developing safe, reliable, compact and cost-effective hydrogen storage is one of the biggest challenges to widespread use of fuel cell technology • Hydrogen has physical characteristics that make it difficult to store large quantities without taking up a great deal of space • Hydrogen will need to be stored onboard vehicles, at hydrogen production sites, refueling stations and stationary power sites • Hydrogen has a very high energy content by weight (3x more than gasoline) and a very low energy content by volume (4x less than gasoline) • 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
hydrogen storage • 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- around -120 to -196 degrees Celsius
Disadvantages • Fuel cells require specific humidity, pressure, etc. • Catalysts are pricey and sensitive to poisoning • Difficult to produce hydrogen • Difficult to store optimum amounts of Hydrogen • If fuels other than hydrogen are used, some greenhouse gasses are emitted • Very few cars currently running on hydrogen
Advantages • Environmental Benefits - Reduce air pollution. • Create less than one ounce of pollution per 1,000 kilowatt-hours of electricity produced • Conventional combustion generating systems produce 25 pounds of pollutants for the same electricity • The only byproducts of these Fuel Cell vehicles are water and heat • Battery replacement/alternative • Fuel Cell replacements for batteries would offer much longer operating life in a packaged of lighter or equal weight • Additionally, Fuel Cell replacements would have an environmental advantage over batteries, since certain kinds of batteries require special disposal treatment • It is a clean, quiet and highly efficient process- two to three times more efficient than fuel burning.
conclusion • Hydrogen fuel cells are efficient, and clean • Also expensive, and require specific humidity, temperature, pressure • With more technological advancements, could be used in mass production for various applications • Not an instant fix for the energy crisis, but definitely a major component • Promising technology • Most viable for niche market use in the near future • Widespread marketplace acceptance and use is still many years away
