EXPERIMENT NO 1 AIM : To study the evolution of fuel cell advancement THEORY
A fuel cell is an electrochemical device that dynamically converts the energy of a chemical reaction between hydrogen and an oxidant into electrical energy for our consumption. Fuel cells work just like a battery in its basic principles: two electrodes separated by an electrolyte. They differ from batteries in that they are designed for continuous replenishment of the reactants consumed. They produce electricity from an external supply of fuel and oxidant (typically oxygen or air, although chlorine and chlorine dioxide have also been used) as opposed to the limited internal energy storage capacity of a battery. The physical structure of a fuel cell consists of an electrolyte layer separating two electrodes. At the present time fuel cells are in research and are constantly being improved for better performance and application purposes HISTORY OF FUEL CELL:
Despite their modern high-tech aura, fuel cells actually have been known to science for more than 150 years! Though generally considered a curiosity in the 1800s, fuel cells became the subject of intense research and development during the 1900s. In 1800, British scientists William Nicholson and Anthony Carlisle had described the process of using electricity to decompose water into hydrogen and oxygen . This process is named electrolysis.
2H2O(l) - 2H2(g) +O2(g) HOW FUEL CELL WORK
In principle, a fuel cell operates like a battery, consisting of an electrolyte placed between two electrodes: an anode and a cathode. Unlike the battery, a fuel cell does not run down or require recharging It will produce energy in the form of electricity and heat as long as fuel is supplied. Oxygen passes over one electrode and hydrogen over the other, generating electricity, water and heat. Hydrogen fuel is fed into the "anode" of the fuel cell. Oxygen (or air) enters the fuel cell through the cathode. This reaction occurs along a catalyst, the hydrogen atom splits into a proton and an electron, which take different paths to the cathode. The proton passes through the electrolyte. The electrons create a separate current that can be utilized before they return to the cathode, to be reunited with the hydrogen and oxygen in a molecule of water. CHARACTERSTIC OF FUEL CELL
Fuel cells can offer cogeneration efficiencies as high as 80% by producing electricity and thermal energy for applications such as water heating or space heating. Fuel cells are also attractive because of their low environmental impact relative to conventional systems. The fuel cell stack itself operates on hydrogen, thus, water is the only product from the stack reaction.
Fuel cells minimize emissions of regulated pollutants. The emissions of currently regulated pollutants such as carbon monoxide, nitrous oxides, sulfur oxides, and particulates are well below current air quality regulations and typically nearly nonexistent .
Because of their attractive properties,fuel cell have already been developed and used widespreadcommercial use through three main application s; TRANSPORTATION , stationary power generation and portable application. RESULT
Hence, we studied the evolutuion of the fuel cells advancements.
Experiment NO 2 Aim: To study the construction,working, and principal of Alkaline
fuel cell (AFC). THEORY:
The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its British inventor, Francis Thomas Bacon, Bacon, is one of the most developed fuel cell technologies. NASA technologies. NASA has used alkaline fuel cells since the mid-1960s, in Apolloin Apollo-series series missions and on the Space Shuttle. Shuttle. Alkaline fuel cells consume hydrogen and pure oxygen producing potable water, heat, and electricity. They are among the most efficient fuel cells, having the potential to reach 70%. WORKING:
The two electrodes are separated by a porous matrix saturated with an aqueous alkaline solution, such as potassium hydroxide (KOH). Aqueous alkaline solutions do not reject carbon dioxide (CO 2) so the fuel cell can become "poisoned" through the conversion of KOH to potassium carbonate (K2CO3). Because of this, alkaline fuel cells typically operate on pure oxygen, or at least purified air purified air and would incorporate a 'scrubber' into the design to clean out as much of the carbon dioxide as is possible. Because the generation and storage requirements of oxygen make pure-oxygen AFCs expensive, there are few companies engaged in active development of the technology. There is, however, some debate in the research community over whether the poisoning is permanent or reversible. The main mechanisms of poisoning are blocking of the pores in the cathode with K2CO3, which is not reversible, and reduction in the ionic conductivity of the electrolyte, which may be reversible by returning the KOH to its original concentration. An alternate method involves
simply replacing the KOH which returns the cell back to its original output. When carbon dioxide reacts with the electrolyte carbonates are formed. The carbonates could precipitate on the pores of electrodes that eventually block them. It has been found that AFCs operating at higher temperature do not show a reduction in performance, whereas at around room temperature, a significant drop in performance has been shown. The carbonate poisoning at ambient temperature is thought to be a result of the low solubility of K2CO3 around room temperature, which leads to precipitation p recipitation of K2CO3 that blocks the electrode pores. Also, these precipitants gradually decrease the hydrophobicity of the electrode backing layer leading to structural degradation and electrode flooding. On the other hand, the charge-carrying hydroxyl ions in the electrolyte can react with carbon dioxide from organic fuel oxidation (i.e. methanol, formic acid) and/or air to form carbonate species. Carbonate formation depletes hydroxyl ions from the electrolyte, which reduces electrolyte conductivity and consequently cell performance. As well as these bulk effects, the effect on water management due to a change in vapor pressure and/or a change in electrolyte volume can be detrimental as well . Chemistry equation:
The fuel cell produces power through a redox reaction between hydrogen and oxygen. At the anode, hydrogen is oxidized according to the reaction:
Diagram of an Alkaline Fuel Cell. 1: Hydrogen 2:Electron flow 3:Load 4:Oxygen 5:Cathode 6:Electrolyte 7:Anode 8:Water 9:Hydroxyl Ions. CHARACTERSTIC OF AFC:
AFCs are the cheapest of fuel cells to manufacture. The catalyst required for the electrodes can be any of a number of different chemicals that are inexpensive compared to those required for other types of fuel cells The commercial prospects for AFCs lie largely with the recently developed bi-polar plate version of this technology, considerably superior in performance to earlier mono-plate versions. The world's first Fuel Cell Ship HYDRA used an AFC system with 5 kW net output.
Another recent development is the solid-state alkaline fuel cell, utilizing alkali anion exchange membranes rather than a liquid. This resolves the problem of poisoning and allows the development of alkaline fuel cells capable of running on safer hydrogen-rich carriers such as liquid urea solutions or metal amine complexes. RESULT
Hence, the construction ,working & principal of alkaline fuel cell has been studied.
Experiment No-3 AIM : To study the construction ,working and principle of phosphoric
acid fuel cell. THEORY:
The electrolyte consists of concentrated phosphoric acid and a silicon carbide matrix is used to retain the acid while both the electrodes which also function as catalysts are made from Pt or its alloys. The operating temperature is maintained between 300 to 430 deg F or 150 to 220 deg C, at lower temperatures, phosphoric acid tends to be a poor ionic conductor and CO poisoning of the Pt electrocataly in the anode becomes severe.st The phosphoric acid fuel cell has demonstrated its use in a number of commercial building. Worldwide, there are over 40 MW of demonstrators in various phases of testing or under fabrication, mostly in the 50 to 200 kW capacity range. However, larger plants of 1 MW and 5 MW output are also being constructed. The electrochemical reactions occurring in a PAFC are: at the anode: H2 = 2H+ + 2eat the cathode: 1/2O2 + 2H+ + 2e- = H 2O with the overall cell reaction: l/2O2 + H2 = H20 . CONSTRUCTION:
Electrolyte is highly concentrated or pure liquid phosphoric acid (H3PO4) saturated in a silicon carbide matrix (SiC). Operating range is about 150 to 210 °C. The electrodes are made of carbon paper coated with a finely dispersed platinum catalyst. ADVANTAGE OF PAFC:
At an operating range of 150 to 200 °C, the expelled water can be converted to steam for air and water heating (combined heat and power). This potentially allows efficiency increases of up to 70%.[2] PAFCs are CO2-tolerant and even can tolerate a CO concentration of about 1.5 percent, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed.[3] At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe.[4] However, they are much less sensitive to CO than PEFCs and AFCs.
APPLICATION:
PAFC have been used for stationary power generators with output in the 100 kW to 400 kW range and they are also finding application in large vehicles such as buses. RESULT
Hence, the construction,working and principal has been studied.
Experiment No 4 Aim : To study the construction,working and principle of proton
exchange membrane fuel cell. THEORY:
This type of fuel cell also known as the Polymer Electrolyte Membrane Fuel Cell consists of a proton conducting membrane, such as a perfluorosulphonic acid polymer as the electrolyte which has good proton conducting properties, contained between two Pt impregnated porous electrodes. The back of the electrodes are coated with a hydrophobic compound such as TeflonR forming a wet proof coating which provides a gas diffusion path to the catalyst layer. Within the cell, H2 at the anode provides protons and releases electrons which pass through the external circuit to reach the cathode. The protons solvate with water molecules and diffuse through the membrane to the cathode to react with the O2 while picking up electrons and forming water. CONSTRUCTION:
Thus, the electrochemical reactions occurring in a PEMFC are: at the anode: H2 = 2H+ + 2eat the cathode:
1/2O2 + 2H+ + 2e- = H 2O with the overall cell reaction: l/2O2 + H2 = H20 Note that the fuel cell operates on H2 while only a few ppm of CO may be tolerated by the Pt catalysis c atalysis at its operating temperature of 175 deg F or 80 deg C. If a hydrocarbon fuel such as natural gas is used as a fuel, reforming of the fuel by the reaction: CH4 + H2O = 3H2 + CO (in the case of natural gas), ga s), followed by shifting of the reformate by the reaction: CO + H2O = H2 + CO2, and removal of the unconverted CO to ppm levels are required to generate the required fuel by the cell. Any sulfur compounds present in a hydrocarbon fuel have to be removed prior to use in the reformer to a concentration of <0.1 ppmV. There is a limit on the CO concentration in the fuel gas to the fuel cell which is <10ppmV. ADVANTAGES
Some of the advantages of the cell are that it may be operated at high current densities resulting in acell that has a fast start capability, compact and light weight design, and that there is no corrosive fluid spillage hazard because the only liquid present in the cell is water. Thus, a PEMFC is well suited for use in vehicles. A disadvantage associated with this type of fuel cell, however, is that Pt catalysts are required as promoters for the electrochemical reaction. PEFCs are capable of operation at pressures from 0.10 to 1.0 MPa (10 to 100 psig) and with suitable current collectors and supporting structure, these fuel cells may be capable of operating at pressures as high as 3000 psi
The ionic conductivity of the electrolyte increases with the water content. It is necessary to maintain a high enough water content in the electrolyte to avoid membrane dehydration and maintain proper ion conductivity without flooding the electrodes. Thus, the balance between production of the water by the oxidation of the H 2 and its evaporation has to be controlled. RESULT
Hence, we studied construction,working and principle of PAMFC
Experiment No-5 AIM: To study the construction,working & principle of Direct
methanol fuel cell THEORY:
DMFC
are
a
subcategory
of proton-exchange of proton-exchange
fuel
cells in
which methanol which methanol is used as the fuel. Their main advantage is the ease of transport of methanol, an energy-dense yet reasonably stable liquid at all environmental conditions. Efficiency is quite low for these cells, so they are targeted especially to portable applications, where energy and power density are more important than efficiency. It is the direct catalytic oxidation of a dilute water solution of some liquid organic fuel (usually methyl alcohol solution of a few percent) by oxygen (or most often air). This reaction produces electric current, carbon dioxide, water and heat. CONSTRUCTION:
REACTION:
On the anode: CH3OH + H2O => CO2 + 6H+ + 6e
-
-
On the cathode: 3/2O2 + 6H+ + 6e => 3 H2O The complete reaction: CH3OH + 3/2O2 => CO2 + 2H2O
Advantages:
Methanol is easier to transport and store than hydrogen
No fuel cell reformer is needed
Small
Disadvantages:
Although the energy density of methanol is high, due to the low operational temperature its electric efficiency and current density are low
Due to the low operational temperature it requires the use of a catalyst
Methanol is toxic and flammable
Areas of use:
Mobile phones
Laptops
Other portable devices
RESULT :
Hence we studied the construction and working of DMFC
EXPERIMENT NO- 6 AIM: To study the construction,working & principle of Molten
carbonate fuel cell Theory:
Molten Carbonate Carbonate Fuel Cells work at a high temperature. The The high temperature allows operating these cells directly with natural gas. They have been developed in the middle of the 1960’s, and since
then the best results have been achieved in enhancing the efficiency and the lifetime of these cells. This type of cells differs in operation from the other fuel cells. They contain molten carbonate salts as electrolyte, usually a mix of two carbonates. The most frequently used combinations are the mix of lithium carbonate and potassium carbonate, and the mix of lithium carbonate and sodium carbonate. The high operational temperature is needed to melt the electrolyte and to achieve sufficient ion permeability. The molten electrolyte is 2-
able to conduct the carbonate ions (CO3 ). These ions move from the cathode to the anode, where they combine with hydrogen to form water, carbon dioxide and electrons. The electrons flow through an outer circuit and so produce electric current and heat before arriving at the cathode CONSTRUCTION: Materials Due to the high operating temperatures of MCFC’s, the materials
need to be very carefully selected to survive the conditions present within the cell. The following sections cover the various materials present in the fuel cell Anode
The anode The anode material typically consists of a porous a porous (3-6 μm, 45-70% material porosity) Ni based alloy. Ni is alloyed with either Chromium or Aluminum in the 2-10% range. These alloying elements allow for formation of LiCrO2/LiAlO2 at the grain boundaries, which increases the materials' creep materials' creep resistance and prevents sintering prevents sintering of the anode at the high operating temperatures of the fuel cell Cathode
On the other side of the cell, the cathode material is composed of a porous Ni that is converted to a lithiated nickel oxide (lithium is intercalated within the NiO crystal structure). The pore size within the cathode is in the range of 7-15 μm with 60-70% of the material being p Electrolyte. MCFC’s use a liquid electrolyte (molten carbonate) which consists of
a sodium(Na) and potassium(K) carbonate. This electrolyte is supported by a ceramic (LiAlO2) matrix to contain the liquid between the electrodes. The high temperatures of the fuel cell is required to produce sufficient ionic conductivity of oxygen through this electrolyte.Common MCFC electrolytes contain 62% Li2CO3 and 38% K2CO3.
Reactions: 2-
-
On the anode: CO3 + H2 => H2O + CO2 + 2e -
On the cathode: CO2 + ½O2 + 2e => CO3
2-
The complete reaction: H2 + ½O2 + CO2 (katód) => H2O + CO2 (anód)
Advantages:
Due to the high operational temperature no fuel reformer is needed
The high operational temperature allows the efficient usage of heat
Cheap raw materials
Disadvantages:
Sensitive to corrosion
Slow starting
Complicated to regulate the flow of carbon dioxide
Areas of use:
Power plants
Industrial usage
RESULT:
Hence we studied working, construction and principle of o f MCFC.
Experiment No-7 AIM: To study the construction,working & principle of solid oxide
fuel cell THEORY:
Solid Oxide Fuel Cells (SOFC) are the fuel cells of the highest operating temperature at present. The electrolyte is such a thin ceramic (solid oxide) layer that is able to conduct oxygen ions at a high temperature. In the second half of the 1950’s two basic types of
solid oxide fuel cells were developed: the SOFCs of tubular and panel structure. The charge carrying oxygen ions form on the cathode from oxygen molecules and electrons. On the anode, after combining with hydrogen, the electrons are released, which reach the cathode through an outer circuit while producing current and heat. he at. CONSTRUCTION: Anode:
The ceramic anode layer must be very porous to allow the fuel to flow towards the electrolyte .Consequently, granular matter is often selected for anode fabrication procedures. The most common material used is a cermet made up of nickel mixed with the ceramic material that is used for the electrolyte in that particular cell, typically YSZ (yttria stabilized zirconia) nanomaterial-based catalysts, this YSZ part helps stop the grain growth of nickel. Cathode:
Cathode materials must be, at a minimum, electronically conductive. Currently, lanthanum strontium manganite (LSM) is the cathode
material of choice for commercial use because of its compatibility with doped zirconia electrolytes.
ELECTROLYTE:
Popular electrolyte materials include yttria-stabilized zirconia (YSZ) (often the 8% form 8YSZ), scandia stabilized zirconia (ScSZ) (usually 9 mol%Sc2O3 – 9ScSZ) and gadolinium doped ceria (GDC).[6] The electrolyte material has crucial influence on the cell performances. Reactions: 2-
On the anode: 2H2 + 2 O => 2H2O + 4e -
On the cathode: O2 + 4e => 2O
-
2-
The complete reaction: 2H2 + O2 => 2H2O
Advantages:
High electric efficiency
The efficiency can be increased to over 70% by a turbo-motor
Due to the high temperature it is not sensitive to the quality of the fuel
Disadvantages:
Slow starting
Slow reaction to the changes of current demands
Expensive raw materials due to the high temperature
Areas of use:
Power plants
Industrial usage
RESULT:
Hence we studied the working ,construction and principe of SOFC
EXPERIMENT NO-8 AIM: To study the applications of fuel cell in modern day
automobiles. Theory:
Fuel cells have been used in various kinds of vehicles including forklifts, especially in indoor applications where their clean emissions are important to air quality, and in space applications. The first commercially produced hydrogen fuel cell automobiles began to be sold by Toyota and leased on a limited basis by Hyundai in 2015, with additional manufacturers planning to enter the market. As of June 2016, the Toyota Mirai is available for retail sale in Japan, California, the UK, Denmark, Germany, Belgium, and Norway.[3] Furthermore, fuel cells are being developed and tested in buses, boats, motorcycles and bicycles, among other kinds of vehicles. There are also demonstration models of buses,[47] and in 2011 there were over 100 fuel cell buses deployed around the world. Most of these buses were produced by UTC Power, Toyota, Ballard, Hydrogenics, and Proton Motor. A fuel cell forklift (also called a fuel cell lift truck or a fuel cell forklift) is a fuel cell-powered industrial forklift truck used to lift and transport materials. Most fuel cells used in forklifts are powered by PEM fuel cells. In 2005 the British firm Intelligent Energy produced the first ever working hydrogen run motorcycle called the ENV (Emission Neutral Vehicle). The motorcycle holds enough fuel to run for four hours, and to travel 160 km (100 mi) in an urban area, at a top speed of 80 km/h (50 mph).
The world's first Fuel Cell Boat HYDRA used an AFC system with 6.5 kW net output. For each liter of fuel consumed, the average outboard motor produces 140 times less[citation needed] the hydrocarbons produced by the average modern car. The first submersible application of fuel cells is the German Type 212 submarine.Each Type 212 contains nine PEM fuel cells, spread throughout the ship, providing between 30 kW and 50 kW each of electrical power. In March 2015, China South Rail Corporation (CSR) demonstrated the world's first hydrogen fuel cell-powered tramcar at an assembly facility in Qingdao. As of 2015, two fuel cell vehicles have been introduced for commercial lease and sale in limited quantities: the Toyota Mirai and the Hyundai ix35 FCEV. Additional demonstration models include the Honda FCX Clarity, and Mercedes-Benz F-Cell. RESULT
Hence, we studied the application of fuel cell in automobiles.
