Hydrogen fuel cell


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Hydrogen fuel cell

  1. 1. `` Hydrogen Fuel Cell in Automobiles Panchal Girishkumar R.*§, Mehta Het D. § and Panchal Vinay A. § * Corresponding Author, Email Id: girishp099@gmail.com § Mechanical Engineering Department, K. J. Somaiya Polytechnic, Vidyavihar, Mumbai-400 077 Abstract: This paper describes about the technique of hydrogen fuel cells adopted in automobiles and storage technologies for hydrogen and thus stepping to the way of green technology with economic power generation. The purpose of this paper is to widespread the knowledge of hydrogen fuel cells which is taking its new place in the field of automobile engineering as a green fuel and storage techniques which is major limiting factor. Few patents and papers are available on the subject under study as very few people are aware about it. Keywords: Hydrogen fuel cells, green fuel, green technology. 1. Introduction: Both from the point of view of global warming and from that of the inevitable exhaustion of Earth's oil reserves; it has become highly desirable to develop an alternative energy source for automobiles. Since the development of the hydrogen fuel cell, which is fueled by hydrogen and oxygen (air) and produces only water, hydrogen has generally been seen to be the most promising approach. However, although the development of Fig No.1 Fuel Cell hydrogen fuel cell technology appears to be Source: http://www.nrel.gov/hydrogen/photos.html progressing smoothly towards eventual commercial exploitation, a viable method for storing hydrogen on board a vehicle is still to be established. (Ross, 2006) 2. Research methodology: The research methodology requires gathering relevant data from the specified documents and compiling information in order to analyze the matter. I hope to shed the light on the following questions through my research: how are automobiles operated with hydrogen fuel cells? What actually takes place in the working of fuel cell? What are the specifications of hydrogen fuel cell? How it is better than gasoline and electrically operated vehicles? How to store hydrogen under specific conditions? 3. Automobiles Operated With Fuel Cell: Terminology: a) Fuel cells: A fuel cell is a device that converts the chemical energy into electrical energy, water and heat through chemical reactions. b) Hydrogen tank: A cylinder tank used for storing hydrogen in a car. c) Traction inverter module: The traction inverter module is used to convert supplied energy as efficiently as possible and make it available to the drive motors in a suitable way. ( http://www.voith.com/en/productsservices/power-transmission/traction-inverter-10375.html) d) Turbo compressor: A dynamic-type compressor is used for the compression and injection of gases (oxygen). e) Transaxle: An automotive part that combines the transmission and the differential and is used on vehicles with front-wheel drive. (http://www.thefreedictionary.com/Transaxles)
  2. 2. `` How to use hydrogen to fuel a car? Fig No.2 Actual Layout Of Hydrogen Car Source: http://www.autoconcept-reviews.com/cars_reviews/ford/ford-hydrogen-fuel-cell-prototypes/cars_reviewsford-hydrogen-fuel-cell-prototypes-2008.html Hydrogen gas from the hydrogen storage tank is supplied to the fuel cell and from the other side atmospheric air is also supplied in it by using turbo compressor. Reaction of oxygen from the air and hydrogen takes place in fuel cell which results in the generation of electricity that is sent to the traction inverter module. The traction inverter module plays an important role of converting the electricity and using it for driving the electric motor which ultimately imparts rotary motion to the wheel. What actually takes place in fuel cell? Pressurized hydrogen gas (H2) enters cell on anode side. Gas is forced through catalyst by pressure. When H2 molecule comes contacts platinum catalyst, it splits into two H+ ions and two electrons (e-). Electrons are conducted through the anode which makes their way through the external circuit (doing useful work such as turning a motor) and return to the cathode side of the fuel cell. On the cathode side, oxygen gas (O2) is forced through the catalyst forms two oxygen atoms, each with a strong negative charge. Negative charge attracts the two H+ ions through the membrane, combine with an oxygen atom and two electrons from the external circuit to form a water molecule (H2O). http://static.howstuffworks.com/flash/fuel-cell-animation.swf Fig No.3 Working Of Fuel Cell Source: www.fuelcelleducation.org
  3. 3. `` Anode reaction: H2 = 2H+ + 2eCathode reaction: O2 + 2H+ = 2H2O Heat and electrical energy is formed after the fusion of electrons. Therefore, electrical energy is used to drive the vehicle and we get water (H2O) as our exhaust. The heat energy converts water into water vapor and thus our exhaust from the vehicle is in the form of water vapor which ultimately has no effect to the environment. Thus, no pollution is created using this technology. Parts of fuel cell: 1) Anode • Negative post of the fuel cell. • Conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external circuit. • Etched channels disperse hydrogen gas over the surface of catalyst. 2) Cathode • Positive post of the fuel cell • Etched channels distribute oxygen to the surface of the catalyst. • Conducts electrons back from the external circuit to the catalyst • Recombine with the hydrogen ions and oxygen to form water. 3) Electrolyte • Proton exchange membrane. • Specially treated material, only conducts positively charged ions. • Membrane blocks electrons. 4) Catalyst • Special material that facilitates reaction of oxygen and hydrogen • Usually platinum powder very thinly coated onto carbon paper or cloth. • Rough & porous maximizes surface area exposed to hydrogen or oxygen • The platinum-coated side of the catalyst faces the PEM. Types of fuel cells: Alkaline fuel cell (AFC) This is one of the oldest designs. It has been used in the U.S. space program since the 1960s. The AFC is very susceptible to contamination, so it requires pure hydrogen and oxygen. It is also very expensive, so this type of fuel cell is unlikely to be commercialized. Phosphoric-acid fuel cell (PAFC) The phosphoric-acid fuel cell has potential for use in small stationary power-generation systems. It operates at a higher temperature than PEM fuel cells, so it has a longer warm-up time. This makes it unsuitable for use in cars. Solid oxide fuel cell (SOFC) These fuel cells are best suited for large-scale stationary power generators that could provide electricity for factories or towns. This type of fuel cell operates at very high temperatures (around 1,832 F, 1,000 C). This high temperature makes reliability a problem, but it also has an advantage: The steam produced by the fuel cell can be channeled into turbines to generate more electricity. This improves the overall efficiency of the system.
  4. 4. `` Proton exchange membrane fuel cell (PEMFC) In the polymer electrolyte membrane (PEM) fuel cell, also known as a proton-exchange membrane cell, a catalyst in the anode separates hydrogen atoms into protons and electrons. The membrane in the center transports the protons to the cathode, leaving the electrons behind. The electrons flow through a circuit to the cathode, forming an electric current to do useful work. In the cathode, another catalyst helps the electrons, hydrogen nuclei and oxygen from the air recombine. When the input is pure hydrogen, the exhaust consists of water vapor. In fuel cells using hydrocarbon fuels the exhaust is water and carbon dioxide. (http://www.news.cornell.edu/releases/Nov03/Fuelcell.institute.deb.html) Fig No. 4 PEM Cell Source:http://en.wikipedia.org/wiki/Proton _exchange_membrane_fuel_cell Auto Power Efficiency Comparison: Technology System efficiency Fuel cell 24-32% Electric battery 26% Gasoline engine 20% Fig No.4 Efficiency vs. Range Source: http://www.howstuffworks.com/fuel-cell.htm/printable Comparison based on Calorific Value: For hydrogen: Higher calorific value: 141,790 kJ/kg Lower calorific value: 121,000 kJ/kg For petrol: Calorific value: 48,000 kJ/kg (http://www.engineeringtoolbox.com/fuels-higher-calorific-values-d_169.html) Heat generated from the hydrogen is more than that of petrol or other gasoline fuels as the calorific value of hydrogen is more. Thus, the power developed is more in vehicles running on hydrogen fuel cells. Hydrogen Storage Technologies In the development of fuel cell vehicles, hydrogen storage is “the biggest remaining research problem” according to the January 2003 Office of Technology Policy report, Fuel Cell Vehicles: z to a New Automotive Future. Current hydrogen storage systems are inadequate to meet the needs of consumers in a fuel cell vehicle. The OTP report continues, “Hydrogen‟s low energy-density makes it difficult to store enough on board a vehicle to achieve sufficient vehicle range without the storage container being too large or too heavy.”
  5. 5. `` Existing and proposed technologies for hydrogen storage include: a) Physical storage: pressurized tanks for gaseous hydrogen and pressurized cryo-tanks for liquid hydrogen; b) Reversible hydrogen uptake in various metal-based compounds including hydrides, nitrides, and imides; chemical storage in irreversible hydrogen carriers such as methanol; c) Cryo-adsorption with activated carbon as the most common adsorbent; and d) Advanced carbon materials absorption, including carbon nano tubes, alkali-doped carbon nano tubes and graphite nano fibers. (Craig et al., 2003) Fig.No.5 Hydrogen Storage Source: Craig et al., 2003 Hydrogen Fuel Storage Safety Hydrogen has a reputation for being explosive and therefore raises concerns about the safety of carrying a substantial quantity of H2 in a vehicle fuel tank. However, because H2 is the lightest gas, it has a tendency to diffuse away quickly in case its container is breached and consequently may represent less of a hazard than gasoline. The simplest way to carry hydrogen fuel in a car or other vehicle is as a high-pressure gas 3-10 kpsi (21-69 MPa) in metal or composite-reinforced (fiberglass, carbon fiber, Kevlar) tanks. This is similar to the way compressed natural gas (CNG) vehicles operate. The authors conclude that “hydrogen is no more or less dangerous than any other energy carrier and furthermore that hydrogen has properties that in certain areas make it safer than other energy carriers: it is not poisonous, and has the ability to dissipate quickly into the atmosphere because of its light weight compared to air.” (Craig et al., 2003) Method High pressure in cylinders Metal hydride Cryogenic liquid Methanol Sodium hydride pellets NaBH4 solution in water Table 1: Data for comparing the methods of storing hydrogen fuels Gravimetric storage Volumetric mass (in kg) Comments efficiency,% mass H2 of H2 per litre 0.7 – 3.0 0.015 „cheap and cheerful‟ widely used 0.65 0.028 Suitable for small systems 14.2 0.040 Widely used for bulk storage 6.9 0.055 Low-cost chemical. Potentially useful in wide range of systems 2.2 0.02 Problem of disposing of spent solution 3.35 0.036 Very expensive to run Table 2: Hydrogen storage parameters goals Metric System energy per unit weight for conventional vehicles with 300 mile range System energy per unit volume for conventional vehicles with 300 mile range Usable energy consumed in releasing H2 H2 release temperature Refueling time H2 ambient release temp. range Durability (to maintain 80% capacity) Goals > 6 MJ/kg > 6 MJ/kg > 5% ~ 80% < 5 minutes -40/+45°C 150,000 miles
  6. 6. `` 4. Limitations: The hydrogen is not so readily available, however. Hydrogen has some limitations that make it impractical for use in most applications. a) For instance, you don't have a hydrogen pipeline coming to your house, and you can't pull up to a hydrogen pump at your local gas station. b) Hydrogen is difficult to store and distribute, so it would be much more convenient if fuel cells could use fuels that are more readily available. c) Technology is currently expensive. 5. Conclusion: Thus, it can be said that there will be a bright future if this hydrogen fuel cell is put up to use in all vehicles by properly considering the safety matter first. And if this eco-friendly technology is used, the rate of pollution is surely going to come down. It is not only eco-friendly but, also serves to be a great fuel source. Since the conventional sources of fuel may not prove to be sufficient, there arises a need to develop a new alternative source of energy. Although there are a few problems related with the storage of hydrogen gas, which might be overcome as the technology develops further. “Hydrogen holds the great promise to meet our future energy needs concerned with our environment.” 6. Future scope: There is a lot of advancement been done by the RnD sectors and it is an on-going process of developing new technologies, it is sure that the there will be many changes done in hydrogen fuel cells in automobiles and its storage facilities. 1.) The technology should be made cost effective. 2.) Developing more safety features to the onboard hydrogen tank and also at refilling stations by making the use of „Auto-locking of supply valves by using hydrogen detector.‟ In this technique, if the hydrogen is leaked from the cylinder or supply line then hydrogen will be detected by the sensor provided to it by sensing the tlv (threshold limit value) of hydrogen. When the gas is detected, the supply valves from the hydrogen tank are closed. Thus, hydrogen gas leaking is thus avoided. 3.) The other technique is to splash the water where the hydrogen gas is leaked. But for this, there will be separate water storing facility required. Thus, hazards expected from hydrogen gas leaking are thus avoided This initiative, supported by legislation in the Energy Policy Act of 2005 (EPACT 2005) and the Advanced Energy Initiative of 2006, aims to develop hydrogen, fuel cell and infrastructure technologies to make fuel-cell vehicles practical and cost-effective by 2020. (Nice, Strickland) Reference: [1] [2] [3] Brand, D. Cornell Chronicle (31 Oct,2003) (http://www.news.cornell.edu/releases/Nov03/Fuelcell.institute.deb.html) Craig, D. Edelstein,B. Evenson,B. Brecher,A. Cox,D. (12 June,2003) “Hydrogen fuel cell vehicle study” Ford hydrogen fuel cell prototypes (2009) (http://www.autoconcept-reviews.com/cars_reviews/ford/ford-hydrogen-fuel-cellprototypes/cars_reviews-ford-hydrogen-fuel-cell-prototypes-2008.html) [4] Freedom CAR and Fuel technical partnership: Technical goals (http://www.eere.energy.gov/vehiclesand fuels/about/partnerships/freedomcar/index.shtml) [5] Fuel Cell Animation (http://static.howstuffworks.com/flash/fuel-cell-animation.swf) [6] Fuel Cells (www.fuelcelleducation.org/wp.../pdf/Intro%20to%20Fuel%20Cells.ppt) [7] Houghton Mifflin Company (2009) (http://www.thefreedictionary.com/Transaxles) [8] Nice, K. Strickland, J. “How fuel cell works” (http://www.howstuffworks.com/fuel-cell.htm/printable) [9] Proton exchange membrane fuel cell (http://en.wikipedia.org/wiki/Proton_exchange_membrane_fuel_cell) [10] Ross, D.K.( 3 August 2006) “Hydrogen storage: The major technological barrier to the development of hydrogen fuel cell car, Vacuum.”Volume80, Issue 10, Pages 1084-1089 [11] The Engineering Toolbox (http://www.engineeringtoolbox.com/fuels-higher-calorific-values-d_169.html) [12] Traction Inverter (http://www.voith.com/en/products-services/power-transmission/traction-inverter-10375.html)