07-12-2012, 06:20 PM
Economics of generation and production of electricity
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INTRODUCTION
The selection of electricity production modes and their 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.
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, but since most of the power plants built before 1990 use hard water as a coolant, setting them up near a source of hard water is the only viable economic option. Recent disasters in Japan have raised concerns over the safety of nuclear power.
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.) are currently expensive to produce, though with advancements in technology their cost of production is coming down. Many governments around the world provide subsidies to offset the high cost and make their production economically feasible.
Production
The production of electricity in 2009 was 20,053TWh, which was 11% of the solar energy the earth receives in one hour (174,000TWh). Sources of electricity were fossil fuels 67%, renewable energy 16% (mainly hydroelectric, wind, solar and biomass), and nuclear power 13%, and other sources were 3%. The majority of fossil fuel usage for the generation of electricity was coal and gas. Oil was 5.5%, as it is the most expensive common commodity used to produce electrical energy. Ninety-two percent of renewable energy was hydroelectric followed by wind at 6% and geothermal at 1.8%. Solar photovoltaic was 0.06%, and solar thermal was 0.004%. Data are from OECD 2011-12 Factbook (2009 data)[10]
Environmental concerns
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 of carbon dioxide.[14]
In the United States, fossil fuel combustion for electric power generation is responsible for 65% of all emissions of sulfur dioxide, the main component of acid rain.[15] Electricity generation is the fourth highest combined source of NOx, carbon monoxide, and particulate matter in the US.[16]
In July 2011, the UK parliament tabled a motion that "levels of (carbon) emissions from nuclear power were approximately three times lower per kilowatt hour than those of solar, four times lower than clean coal and 36 times lower than conventional coal".[17]
Water consumption
Most large scale thermoelectric power stations consume considerable amounts of water for cooling purposes and boiler water make up - 1 L/kWh for once through (e.g. river cooling), and 1.7 L/kWh for cooling tower cooling.[18] Water abstraction for cooling water accounts for about 40% of European total water abstraction, although most of this water is returned to its source, albeit slightly warmer. Different cooling systems have different consumption vs. abstraction characteristics. Cooling towers withdraw a small amount of water from the environment and evaporate most of it. Once-through systems withdraw a large amount but return it to the environment immediately, at a higher temperature