environmental and concers

Upload: amitguptaujj

Post on 04-Jun-2018

217 views

Category:

Documents


0 download

TRANSCRIPT

  • 8/13/2019 Environmental and Concers

    1/4

    Most scientists agree that emissions of pollutants and greenhouse gases from fossil fuel-based

    electricity generation account for a significant portion of world greenhouse gas emissions; in the

    United States, electricity generation accounts for nearly 40% of emissions, the largest of any source.

    Transportation emissions are close behind, contributing about one-third of U.S. production ofcarbon

    dioxide.[16] In the United States, fossil fuel combustion for electric power generation is responsible

    for 65% of all emissions ofsulfur dioxide,the main component of acid rain.[17] Electricity generation

    is the fourth highest combined source ofNOx,carbon monoxide,andparticulate matter in the

    US.[18] In July 2011, the UK parliament tabled a motion that "levels of (carbon) emissions from

    nuclear power were approximately three times lower perkilowatt hour than those of solar, four

    times lower than clean coal and 36 times lower than conventional coal".[19] Though Solar PV

    generation is positioned as environmentally friendly, fabrication of PV cells utilizes substantial

    amounts of water in addition to toxic chemicals such as phosphorus and arsenic. These are often

    overlooked when promoting PV. Because of strict environmental regulations in the United States, for

    example, PV fabrication is often performed in countries with lower standards,such as China,which

    produces approximately half the world's PV panels.The selection of electricity production modes andtheir economic viability varies in accordance with demand and region. Hydroelectric plants, nuclear

    power plants, thermal power plants and renewable sources have their own pros and cons, and

    selection is based upon the local power requirement and the fluctuations in demand. All power grids

    have varying loads on them but the daily minimum is the base load, supplied by plants which run

    continuously. Nuclear, coal, oil and gas plants can supply base load, with the low-carbon option

    being nuclear. Thermal energy is economical in areas of high industrial density, as the high demand

    cannot be met by renewable sources. The effect of pollution is also minimized as industries are

    usually located away from residential areas. These plants can also withstand variation in load and

    consumption by adding more units or temporarily decreasing the production of some units. Nuclear

    power plants can produce a huge amount of power from a single unit. However, recent disasters in

    Japan have raised concerns over the safety of nuclear power, and the capital cost of nuclear plants is

    very high. Hydroelectric power plants are located in areas where the potential energy from flowing

    water can be harnessed for moving turbines and the generation of power. It is not an economically

    viable source of production where the load varies too much during the annual production cycle and

    the ability to stop the flow of water is limited. Renewable sources other than hydroelectricity (solar

    power, wind energy, tidal power, etc.) due to advancements in technology, and with mass

    production, their cost of production has come down and the energy is now in many cases cost-

    comparative with fossil fuels. Many governments around the world provide subsidies to offset the

    higher cost of any new power production, and to make the installation of renewable energy systems

    economically feasible. However, their use is frequently limited by their intermittent nature. If natural

    gas prices are below $3 per millionBritish thermal units,generating electricity from natural gas is

    cheaper than generating power by burning coalTurbines

    Large dams such asThree Gorges Damin China can provide large amounts ofhydroelectric power; it

    has a 22.5GWcapability.

    All turbines are driven by a fluid acting as an intermediate energy carrier. Many of the heat engines

    just mentioned areturbines.Other types of turbines can be driven by wind or falling water. Sources

    include:

    Steam - Water is boiled by-

    http://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-16http://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-17http://en.wikipedia.org/wiki/NOxhttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/Atmospheric_particulate_matterhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-18http://en.wikipedia.org/wiki/Kilowatt_hourhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-19http://en.wikipedia.org/wiki/Solar_power_in_Chinahttp://en.wikipedia.org/wiki/British_thermal_unithttp://en.wikipedia.org/wiki/British_thermal_unithttp://en.wikipedia.org/wiki/British_thermal_unithttp://en.wikipedia.org/wiki/Three_Gorges_Damhttp://en.wikipedia.org/wiki/Hydroelectrichttp://en.wikipedia.org/wiki/Watt#Gigawatthttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Watt#Gigawatthttp://en.wikipedia.org/wiki/Hydroelectrichttp://en.wikipedia.org/wiki/Three_Gorges_Damhttp://en.wikipedia.org/wiki/British_thermal_unithttp://en.wikipedia.org/wiki/Solar_power_in_Chinahttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-19http://en.wikipedia.org/wiki/Kilowatt_hourhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-18http://en.wikipedia.org/wiki/Atmospheric_particulate_matterhttp://en.wikipedia.org/wiki/Carbon_monoxidehttp://en.wikipedia.org/wiki/NOxhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-17http://en.wikipedia.org/wiki/Sulfur_dioxidehttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-16http://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxide
  • 8/13/2019 Environmental and Concers

    2/4

    Nuclear fission The burning offossil fuels (coal, natural gas, or petroleum). In hot gas (gas turbine),

    turbines are driven directly by gases produced by thecombustion of natural gas or

    oil.Combined cycle gas turbine plants are driven by both steam and natural gas.

    They generate power by burning natural gas in agas turbine and use residual heat togenerate additional electricity from steam. These plants offer efficiencies of up to

    60%.

    Renewables. The steam is generated by: Biomass Solar thermal energy (the sun as the heat source):solar parabolic

    troughs andsolar power towers concentrate sunlight to heat a heat transfer

    fluid, which is then used to produce steam.

    Geothermal power.Either steam under pressure emerges from the groundand drives a turbine or hot water evaporates a low boiling liquid to create

    vapour to drive a turbine.

    Ocean thermal energy conversion (OTEC): uses the small difference betweencooler deep and warmer surface ocean waters to run a heat engine (usually

    a turbine).

    Other renewable sources:Large dams such asHoover Dam can provide large amounts ofhydroelectricpower; it has

    2.07GW capability.

    Water (hydroelectric) - Turbine blades are acted upon by flowing water, producedbyhydroelectric dams ortidal forces.

    Wind - Mostwind turbines generate electricity from naturally occurring wind.Solarupdraft towers use wind that is artificially produced inside the chimney by heating it

    with sunlight, and are more properly seen as forms of solar thermal energy.

    Reciocating engines[edit]

    Small electricity generators are often powered byreciprocating engines burningdiesel,biogas or

    natural gas.Diesel engines are often used for back up generation, usually at low voltages. However

    most large power grids also usediesel generators,originally provided as emergency back up for a

    specific facility such as a hospital, to feed power into the grid during certain circumstances. Biogas is

    often combusted where it is produced, such as a landfill or wastewater treatment plant, with a

    reciprocating engine or a microturbine, which is a small gas turbine.

    A coal-fired power plant in Laughlin, Nevada U.S.A. Owners of this plant ceased operations after

    declining to invest in pollution control equipment to comply with pollution regulations.[8]

    Photovoltaic panels[edit]

    http://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Fossil-fuel_power_stationhttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Biomasshttp://en.wikipedia.org/wiki/Solar_thermal_energyhttp://en.wikipedia.org/wiki/Solar_parabolic_troughhttp://en.wikipedia.org/wiki/Solar_parabolic_troughhttp://en.wikipedia.org/wiki/Solar_power_towerhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Ocean_thermal_energy_conversionhttp://en.wikipedia.org/wiki/Hoover_Damhttp://en.wikipedia.org/wiki/Hydroelectrichttp://en.wikipedia.org/wiki/Watt#Gigawatthttp://en.wikipedia.org/wiki/Hydroelectricityhttp://en.wikipedia.org/wiki/Tidal_powerhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Solar_updraft_towerhttp://en.wikipedia.org/wiki/Solar_updraft_towerhttp://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=5http://en.wikipedia.org/wiki/Reciprocating_enginehttp://en.wikipedia.org/wiki/Diesel_fuelhttp://en.wikipedia.org/wiki/Biogashttp://en.wikipedia.org/wiki/Diesel_enginehttp://en.wikipedia.org/wiki/Diesel_generatorhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-8http://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=6http://en.wikipedia.org/wiki/Electricity_generation#cite_note-8http://en.wikipedia.org/wiki/Diesel_generatorhttp://en.wikipedia.org/wiki/Diesel_enginehttp://en.wikipedia.org/wiki/Biogashttp://en.wikipedia.org/wiki/Diesel_fuelhttp://en.wikipedia.org/wiki/Reciprocating_enginehttp://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=5http://en.wikipedia.org/wiki/Solar_updraft_towerhttp://en.wikipedia.org/wiki/Solar_updraft_towerhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Tidal_powerhttp://en.wikipedia.org/wiki/Hydroelectricityhttp://en.wikipedia.org/wiki/Watt#Gigawatthttp://en.wikipedia.org/wiki/Hydroelectrichttp://en.wikipedia.org/wiki/Hoover_Damhttp://en.wikipedia.org/wiki/Ocean_thermal_energy_conversionhttp://en.wikipedia.org/wiki/Geothermal_powerhttp://en.wikipedia.org/wiki/Solar_power_towerhttp://en.wikipedia.org/wiki/Solar_parabolic_troughhttp://en.wikipedia.org/wiki/Solar_parabolic_troughhttp://en.wikipedia.org/wiki/Solar_thermal_energyhttp://en.wikipedia.org/wiki/Biomasshttp://en.wikipedia.org/wiki/Gas_turbinehttp://en.wikipedia.org/wiki/Combined_cyclehttp://en.wikipedia.org/wiki/Combustionhttp://en.wikipedia.org/wiki/Fossil-fuel_power_stationhttp://en.wikipedia.org/wiki/Nuclear_fission
  • 8/13/2019 Environmental and Concers

    3/4

    Unlike the solar heat concentrators mentioned above,photovoltaic panels convert sunlight directly

    to electricity. Although sunlight is free and abundant, solar electricity is still usually more expensive

    to produce than large-scale mechanically generated power due to the cost of the panels. Low-

    efficiency silicon solar cells have been decreasing in cost and multijunction cells with close to 30%

    conversion efficiency are now commercially available. Over 40% efficiency has been demonstrated in

    experimental systems.[9] Until recently, photovoltaics were most commonly used in remote sites

    where there is no access to a commercial power grid, or as a supplemental electricity source for

    individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic

    technology, combined with subsidies driven by environmental concerns, have dramatically

    accelerated the deployment of solar panels. Installed capacity is growing by 40% per year led by

    increases in Germany, Japan, California and New Jersey.

    Other generation methods[edit]

    Wind-powered turbinesusually provide electrical generation in conjunction with other methods of

    producing power.

    Various other technologies have been studied and developed for power generation. Solid-state

    generation (without moving parts) is of particular interest in portable applications. This area is

    largely dominated bythermoelectric (TE) devices, thoughthermionic (TI)

    andthermophotovoltaic (TPV) systems have been developed as well. Typically, TE devices are used

    at lower temperatures than TI and TPV systems.Piezoelectric devices are used for power generation

    from mechanical strain, particularly inpower harvesting.Betavoltaics are another type of solid-state

    power generator which produces electricity from radioactive decay. Fluid-

    basedmagnetohydrodynamic (MHD) power generation has been studied as a method for extracting

    electrical power fromnuclear reactors and also from more conventional fuel combustion

    systems.Osmotic power finally is another possibility at places where salt and fresh water merges

    (e.g. deltas, ...)Electrochemical electricity generation is also important in portable and mobile

    applications. Currently, most electrochemical power comes from closed electrochemical cells

    ("batteries"),[10] which are arguably utilized more asstorage systems than generation systems; but

    open electrochemical systems, known asfuel cells,have been undergoing a great deal of research

    and development in the last few years. Fuel cells can be used to extract power either from natural

    fuels or from synthesized fuels (mainly electrolytichydrogen)and so can be viewed as either

    generation systems or storage systems depending on their use.

    There are seven fundamental methods of directly transforming other forms of energy into electrical

    energy:

    Static electricity,from the physical separation and transport of charge(examples:triboelectric effect andlightning)

    Electromagnetic induction,where anelectricalgenerator,dynamo oralternator transformskinetic energy (energy of motion) into

    electricity. This is the most used form for generating electricity and is based onFaraday's

    law.It can be experimented by simply rotating a magnet within closed loops of a conducting

    material (e.g. copper wire)

    http://en.wikipedia.org/wiki/Photovoltaicshttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-9http://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=7http://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Thermoelectricityhttp://en.wikipedia.org/wiki/Thermionic_converterhttp://en.wikipedia.org/wiki/Thermophotovoltaichttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Power_harvestinghttp://en.wikipedia.org/wiki/Betavoltaicshttp://en.wikipedia.org/wiki/MHD_generatorhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/Osmotic_powerhttp://en.wikipedia.org/wiki/Electrochemistryhttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Electricity_generation#cite_note-10http://en.wikipedia.org/wiki/Electricity_storagehttp://en.wikipedia.org/wiki/Fuel_cellhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Static_electricityhttp://en.wikipedia.org/wiki/Triboelectric_effecthttp://en.wikipedia.org/wiki/Lightninghttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Dynamohttp://en.wikipedia.org/wiki/Alternatorhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Faraday%27s_law_of_inductionhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Alternatorhttp://en.wikipedia.org/wiki/Dynamohttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Electromagnetic_inductionhttp://en.wikipedia.org/wiki/Lightninghttp://en.wikipedia.org/wiki/Triboelectric_effecthttp://en.wikipedia.org/wiki/Static_electricityhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Fuel_cellhttp://en.wikipedia.org/wiki/Electricity_storagehttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-10http://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Electrochemistryhttp://en.wikipedia.org/wiki/Osmotic_powerhttp://en.wikipedia.org/wiki/Nuclear_reactorhttp://en.wikipedia.org/wiki/MHD_generatorhttp://en.wikipedia.org/wiki/Betavoltaicshttp://en.wikipedia.org/wiki/Power_harvestinghttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Thermophotovoltaichttp://en.wikipedia.org/wiki/Thermionic_converterhttp://en.wikipedia.org/wiki/Thermoelectricityhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/w/index.php?title=Electricity_generation&action=edit&section=7http://en.wikipedia.org/wiki/Electricity_generation#cite_note-9http://en.wikipedia.org/wiki/Photovoltaics
  • 8/13/2019 Environmental and Concers

    4/4

    Electrochemistry,the direct transformation ofchemical energy into electricity, as inabattery,fuel cell ornerve impulse

    Photoelectric effect,the transformation of light into electrical energy, as insolar cells Thermoelectric effect,the direct conversion of temperature differences to electricity, as

    inthermocouples,thermopiles,andthermionic converters.

    Piezoelectric effect,from the mechanical strain of electricallyanisotropic molecules orcrystals. Researchers at the US Department of Energy's Lawrence Berkeley National

    Laboratory (Berkeley Lab) have developed apiezoelectric generator sufficient to operate

    aliquid crystal display using thin films of M13 bacteriophage.[7]

    Nuclear transformation, the creation and acceleration of charged particles(examples:betavoltaics oralpha particle emission)

    Static electricity was the first form discovered and investigated, and theelectrostatic generator isstill used even in modern devices such as theVan de Graaff generator andMHD generators.Charge

    carriers are separated and physically transported to a position of increased electric potential. Almost

    all commercial electrical generation is done using electromagnetic induction, in whichmechanical

    energy forces anelectrical generator to rotate. There are many different methods of developing the

    mechanical energy, includingheat engines,hydro, wind and tidal power. The direct conversion

    ofnuclear potential energy to electricity bybeta decay is used only on a small scale. In a full-size

    nuclear power plant, the heat of a nuclear reaction is used to run a heat engine. This drives a

    generator, which converts mechanical energy into electricity by magnetic induction. Most electric

    generation is driven byheat engines.The combustion offossil fuels supplies most of the heat to

    these engines, with a significant fraction fromnuclear fission and some fromrenewable sources.The

    modernsteam turbine (invented bySir Charles Parsons in 1884) currently generates about 80% of

    theelectric power in the world using a variety of heat sources.

    http://en.wikipedia.org/wiki/Electrochemistryhttp://en.wikipedia.org/wiki/Chemical_energyhttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Fuel_cellhttp://en.wikipedia.org/wiki/Nerve_impulsehttp://en.wikipedia.org/wiki/Photoelectric_effecthttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Thermoelectric_effecthttp://en.wikipedia.org/wiki/Thermocouplehttp://en.wikipedia.org/wiki/Thermopileshttp://en.wikipedia.org/wiki/Thermionic_converterhttp://en.wikipedia.org/wiki/Piezoelectric_effecthttp://en.wikipedia.org/wiki/Anisotropichttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-7http://en.wikipedia.org/wiki/Betavoltaicshttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Static_electricityhttp://en.wikipedia.org/wiki/Electrostatic_generatorhttp://en.wikipedia.org/wiki/Van_de_Graaff_generatorhttp://en.wikipedia.org/wiki/MHD_generatorhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Nuclear_potential_energyhttp://en.wikipedia.org/wiki/Beta_decayhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Renewable_sourcehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Charles_Algernon_Parsonshttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Electric_powerhttp://en.wikipedia.org/wiki/Charles_Algernon_Parsonshttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Renewable_sourcehttp://en.wikipedia.org/wiki/Nuclear_fissionhttp://en.wikipedia.org/wiki/Fossil_fuelhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Beta_decayhttp://en.wikipedia.org/wiki/Nuclear_potential_energyhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Electrical_generatorhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/Mechanical_energyhttp://en.wikipedia.org/wiki/MHD_generatorhttp://en.wikipedia.org/wiki/Van_de_Graaff_generatorhttp://en.wikipedia.org/wiki/Electrostatic_generatorhttp://en.wikipedia.org/wiki/Static_electricityhttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Betavoltaicshttp://en.wikipedia.org/wiki/Electricity_generation#cite_note-7http://en.wikipedia.org/wiki/Liquid_crystal_displayhttp://en.wikipedia.org/wiki/Piezoelectrichttp://en.wikipedia.org/wiki/Anisotropichttp://en.wikipedia.org/wiki/Piezoelectric_effecthttp://en.wikipedia.org/wiki/Thermionic_converterhttp://en.wikipedia.org/wiki/Thermopileshttp://en.wikipedia.org/wiki/Thermocouplehttp://en.wikipedia.org/wiki/Thermoelectric_effecthttp://en.wikipedia.org/wiki/Solar_cellhttp://en.wikipedia.org/wiki/Photoelectric_effecthttp://en.wikipedia.org/wiki/Nerve_impulsehttp://en.wikipedia.org/wiki/Fuel_cellhttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Chemical_energyhttp://en.wikipedia.org/wiki/Electrochemistry