3 1 A Fuel Cell example essay topic

Introduction 1.0 "Renewable Energy" is the term used to describe those energy flows that occur naturally and repeatedly in the environment, e.g. from the sun, wind and the oceans, and from plants and the fall of water. It also refers to the energy available from wastes and to the emerging clean technology of fuel cells. There are wide ranges of renewable energy sources / technologies, varying in technical and commercial viability. These include: o Solar Power (Photovoltaic) o Hydro - electric Powero Hydrogen Fuel Cells o Geothermal o Wind Powero Nuclear Power 1.1 The modern drive to harness renewable energy began in the 1970's. It was promoted by concerns over the price and availability of fossil fuels - oil, gas, and coal. Fossil fuels are finite - only coal is predicted to be available in significant quantities at the end of the 21st century at current rates of consumption.

Using fossil fuels to generate electricity also produces pollutants, which can lead to environmental problems (such as acid rain and the "greenhouse effect"). By contrast, renewable energy produces few, if any, harmful emissions. Exploiting renewable, which at present meet over 2% of the UK's electricity needs, also reduces the rate at which other energy resources are used up. With the world's population continuing to grow, renewable energy promises to play an increasingly significant role in the future. 1.2 The estimated oil reserves in the Earth's crust are about 1 trillion barrels. Oil consumption is at 25 billion barrels per year and increasing at 1.5% per year.

At current rates of consumption, measured against known reserves, there is only a 30-year supply of oil in the Earth's crust. Even if the reserve estimate were doubled, it is a moral imperative that the population takes immediate action to develop a sustainable energy economy. Solar Energy 2.0 Solar energy is quite simply the energy produced by the sun and collected elsewhere, normally the Earth. The sun creates its energy through a thermonuclear process that converts about 650,000,000 tons of hydrogen to helium every second. The process creates heat and electromagnetic radiation. The electromagnetic radiation (including visible light, infra-red light, and ultra-violet radiation) streams out into space in all directions.

Only a very small fraction of the total radiation produced reaches the Earth. The radiation that does reach the Earth is the indirect source of nearly every type of energy used today. The exceptions are geothermal energy, and nuclear fission and fusion. Much of the world's required energy can be supplied by solar power. 2.1 The first practical solar cell was developed at Bell Laboratories in 1954. With the advent of the space program, Photovoltaic cells made from semi-conductor grade silicon quickly became the power source of choice for use on satellites.

The systems were very reliable, and cost was of little concern. In the early 1970's, the disruption of oil supplies to the industrialized world led to serious consideration of Photovoltaic as a terrestrial power source. This application focused research attention on improving performance, lowering costs and increasing reliability. Due to the nature of solar energy, two components are required to have a functional solar energy generator. These two components are a collector and a storage unit. The collector simply collects the radiation that falls on it and converts a fraction of it to other forms of energy (either electricity and heat or heat alone).

The storage unit is required because of the non-constant nature of solar energy; at certain times only a very small amount of radiation will be received. The storage unit can hold the excess energy produced during the periods of maximum productivity, and release it when the productivity drops. In practice, a backup power supply is added, too, for the situations when the amount of energy required is greater than both what is being produced and what is stored in the container. 2.2 The solar cells that can be seen on calculators and satellites are Photovoltaic cells or modules (modules are simply a group of cells electrically connected and packaged in one frame).

Photovoltaic cells, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. Diagram of Photovoltaic (PV) cell Photovoltaic (PV) cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used. Basically, when light strikes the cell, a certain portion of it is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy dislodges electrons within the material, allowing them to flow freely. This flow of electrons is a current, and by placing metal contacts on the top and bottom of the PV cell, the current can be drawn off to be used externally.

This current, together with the cells voltage (which is a result of its built in electric field or fields), defines the power (or wattage) that the solar cell can produce. 2.3 Most of the PV cells available today operate at an efficiency of less than 15%, that is, of all the radiation that falls upon them, less than 15% of it is converted into electricity. The maximum theoretical efficiency for a PV cell is only 32.3%, but at this efficiency, solar electricity is very economical. Most other forms of electricity generation are at a lower efficiency than this. Unfortunately, reality still lags behind theory and a 15% efficiency is not usually considered economical by most power companies, even if it is fine for toys and pocket calculators.

However, hope for bulk solar electricity should not be abandoned, for recent scientific advances have created a solar cell with an efficiency of 28.2% in the laboratory. This type of cell has yet to be field-tested. If it maintains its efficiency in the uncontrolled environment of the outside world, it will be economical for power companies to build solar power facilities. 2.4 Solar power has two major advantages over fossil fuels.

The first is in the fact that it is renewable, it is never going to run out. The second is its effect on the environment. While the burning of fossil fuels introduces many harmful pollutants into the atmosphere and contributes to environmental problems like global warming and acid rain, solar energy is completely non-polluting. While many acres of land must be destroyed to feed a fossil fuel energy plant its required fuel, the only land that must be destroyed for a solar energy plant is the land, which it is situated on.

This ability to decentralize solar energy is something that fossil fuel burning cannot offer. Of the main types of energy usage, the least suited to solar power is transportation. While large, relatively slow vehicles like ships could power themselves with large on board solar panels, small constantly turning vehicles like cars could not. The only possible way a car could be completely solar powered would be through the use of a battery that was charged by solar power at some stationary point and later loaded into the car. 2.5 Today, solar generated electricity serves people living in the most isolated spots on earth as well as in the center of our biggest cities.

First used in the space program, PV systems are now both generating electricity to pump water, light up the night, activate switches, charge batteries, supply the electric supply grid, and much more. Whether you are a homeowner, farmer, planner, architect, or just someone who pays electric bills, PV may already touch your life in some way. Hydrogen Fuel Cells 3.0 As early as 1839, Sir William Grove (often referred to as the "Father of the Fuel Cell") discovered that it may be possible to generate electricity by reversing the electrolysis of water. It was not until 1889 that two researchers, Charles Langer and Ludwig Mond, coined the term "fuel cell" as they were trying to engineer the first practical fuel cell using air and coal gas. While further attempts were made in the early 1900's to develop fuel cells that could convert coal or carbon into electricity, the advent of the internal combustion engine temporarily quashed any hopes of further development.

Francis Bacon developed what was perhaps the first successful fuel cell device in 1932. Due to substantial number of technical hurdles, it was not until 1959 that Bacon and company first demonstrated a practical five-kilowatt fuel cell system In addition, in the late 1950's, NASA began to build a compact electricity generator for use on space missions. NASA soon came to fund hundreds of research contracts involving fuel cell technology. Fuel cells now have a proven role in the space program, after supplying electricity to several space missions. 3.1 A Fuel Cell is an electrochemical device that produces electricity by separating the fuel (generally hydrogen gas) via a catalyst. The protons flow through a membrane and combine with oxygen to form water - again with the help of a catalyst.

The electrons flow from the anode to the cathode to create electricity. As long as the reactants - pure hydrogen and oxygen - are supplied to the fuel cell, it will produce electrical energy. Diagram of Fuel Cell parts single fuel cell is basically a piece of plastic between two pieces of carbon plates which are sandwiched between two end plates acting as electrodes. These plates have channels that distribute the fuel and oxygen. 3.2 A factor that draws interest to the fuel cell is that it can operate at efficiencies two or three times that of the internal combustion engine, and it requires no moving parts. Since it converts the fuel, hydrogen, and oxygen directly to electrical energy, the only two by-products are heat and water.

Hydrogen can be produced from water, sewage, garbage, landfill accumulations, agricultural biomass, paper product waste, and many other waste streams that contain hydrogen-bearing compounds. Wind power, tides, and falling water (hydro-electric turbines) can also create electricity to split water into hydrogen and oxygen. When hydrogen is produced from the sun or other renewable energy sources it is called "Solar-Hydrogen". 3.3 All fuels need air (oxygen) for combustion. Hydrogen is the only common fuel that is not chemically bound to carbon; therefore when hydrogen burns in air it produces only heat energy, water and trace amounts of oxides of nitrogen.

Water and oxides of nitrogen are natural in our atmosphere. When hydrocarbon fuels (coal, oil, natural gas, propane, wood) burn they may create serious pollutants like carbon monoxide (a poisonous gas which is produced by incomplete combustion), carbon dioxide (a greenhouse gas), an extensive list of complex hydrocarbon chemicals and quantities of particulate matter. 3.4 However, early commercial applications of fuel cells are generally expected to use hydrocarbon fuels, such as natural gas. Practical fuel cell systems are therefore likely to include a fuel processor, which generates hydrogen from hydrocarbons.

There are a number of types of fuel cells currently the focus of development work: o Alkaline fuel cells - A FCo Direct methanol fuel cells - DMF Co Molten carbonate fuel cells - MCF Co Phosphoric acid fuel cells - PAF Co Proton exchange membrane fuel cells - P EMo Regenerative fuel cells - Rico Solid oxide fuel cells - SOFT 3.5 Fuels cells are inherently clean and efficient and are uniquely able to address the issues of energy security and environmental degradation. Now market experience is showing that the technology provides a range of critical benefits that no other single power generation technology can match. o Fuel cells are quiet and reliable with no moving parts. o They produce no emissions (other than water) when using pure hydrogen and very light emissions when using hydrocarbon or alcohol fuel. o They are extremely efficient compared to conventional means of generating electricity typically 40 - 50%. o PEM fuel cells have a very low operating temperature (.