2008. augusztus 12., kedd


Hydroelectricity is a form of hydropower, and is the most widely used form of renewable energy. It produces no waste, and does not produce carbon dioxide (CO2), a greenhouse gas. Hydroelectricity now supplies about 715,000 MWe or 19% of world electricity (16% in 2003), accounting for over 63% of the total electricity from renewable sources in 2005.
Although large hydroelectric installations generate most of the world's hydroelectricity, small hydro schemes are particularly popular in China, which has over 50% of world small hydro capacity. Some jurisdictions do not consider large hydro projects to be a sustainable energy source due to human and environmental impacts, though this judgment depends on the definition of sustainability used.
(from wikipedia)

Fuel economy

In theory, all fuel-driven vehicles have a fuel economy (measured as miles per US gallon, or liters per 100 km) that is directly proportional to the fuel's energy content. In reality, there are many other variables that come in to play that affect the performance of a particular fuel in a particular engine. Ethanol contains approx. 34% less energy per unit volume than gasoline, and therefore in theory, burning pure ethanol in a vehicle will result in a 34% reduction in miles per US gallon, given the same fuel economy, compared to burning pure gasoline. This assumes that the octane ratings of the fuels, and thus the engine's ability to extract energy from the fuels, are the same. For E10 (10% ethanol and 90% gasoline), the effect is small (~3%) when compared to conventional gasoline, and even smaller (1-2%) when compared to oxygenated and reformulated blends. However, for E85 (85% ethanol), the effect becomes significant. E85 will produce lower mileage than gasoline, and will require more frequent refueling. Actual performance may vary depending on the vehicle. The EPA-rated mileage of current USA flex-fuel vehicles should be considered when making price comparisons, but it must be noted that E85 is a high performance fuel, with an octane rating of about 104, and should be compared to premium. In one estimate the US retail price for E85 ethanol is 2.62 US dollar per gallon or 3.71 dollar corrected for energy equivalency compared to a gallon of gasoline priced at 3.03 dollar. Brazilian cane ethanol (100%)is priced at 3.88 dollar against 4.91 dollar for E25 (figures July 2007).
(from wikipedia)


Ethanol is considered "renewable" because it is primarily the result of conversion of the sun's energy into usable energy. Creation of ethanol starts with photosynthesis causing the feedstocks such as switchgrass, sugar cane, or corn to grow. These feedstocks are processed into ethanol.
About 5% of the ethanol produced in the world in 2003 was actually a petroleum product. It is made by the catalytic hydration of ethylene with sulfuric acid as the catalyst. It can also be obtained via ethylene or acetylene, from calcium carbide, coal, oil gas, and other sources. Two million tons of petroleum-derived ethanol are produced annually. The principal suppliers are plants in the United States, Europe, and South Africa. Petroleum derived ethanol (synthetic ethanol) is chemically identical to bio-ethanol and can be differentiated only by radiocarbon dating.
Bio-ethanol is obtained from the conversion of carbon based feedstock. Agricultural feedstocks are considered renewable because they get energy from the sun using photosynthesis, provided that all minerals required for growth (such as nitrogen and phosphorus) are returned to the land. Ethanol can be produced from a variety of feedstocks such as sugar cane, bagasse, miscanthus, sugar beet, sorghum, grain sorghum, switchgrass, barley, hemp, kenaf, potatoes, sweet potatoes, cassava, sunflower, fruit, molasses, corn, stover, grain, wheat, straw, cotton, other biomass, as well as many types of cellulose waste and harvestings, whichever has the best well-to-wheel assessment.
Current, first generation processes for the production of ethanol from corn use only a small part of the corn plant: the corn kernels are taken from the corn plant and only the starch, which represents about 50% of the dry kernel mass, is transformed into ethanol. Two types of second generation processes are under development. The first type uses enzymes and yeast to convert the plant cellulose into ethanol while the second type uses pyrolysis to convert the whole plant to either a liquid bio-oil or a syngas. Second generation processes can also be used with plants such as grasses, wood or agricultural waste material such as straw.
(from wikipedia)

Anhydrous ethanol

Anhydrous ethanol (ethanol with less than 1% water) can be blended with gasoline in varying quantities up to pure ethanol (E100), and most spark-ignited gasoline style engines will operate well with mixtures of 10% ethanol (E10). Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and the use of 10% ethanol gasoline is mandated in some cities where harmful levels of auto emissions are possible.
Ethanol can be mass-produced by fermentation of sugar or by hydration of ethylene (ethene CH2=CH2) from petroleum and other sources. Current interest in ethanol mainly lies in bio-ethanol, produced from the starch or sugar in a wide variety of crops, but there has been considerable debate about how useful bio-ethanol will be in replacing fossil fuels in vehicles. Concerns relate to the large amount of arable land required for crops, as well as the energy and pollution balance of the whole cycle of ethanol production. Recent developments with cellulosic ethanol production and commercialization may allay some of these concerns.
According to the International Energy Agency, cellulosic ethanol could allow ethanol fuels to play a much bigger role in the future than previously thought. Cellulosic ethanol offers promise as resistant cellulose fibers, a major component in plant cells walls, can be used to generate ethanol. Dedicated energy crops, such as switchgrass, are also promising cellulose sources that can be produced in many regions of the United States.
(from wikipeida)

Ethanol fuel

Ethanol fuel is ethanol (ethyl alcohol), the same type of alcohol found in alcoholic beverages. It can be used as a fuel, mainly as a biofuel alternative to gasoline, and is widely used in cars in Brazil. Because it is easy to manufacture and process, and can be made from very common crops, such as sugar cane and maize (corn), it is an increasingly common alternative to gasoline in some parts of the world.
(from wikipedia)

2008. július 7., hétfő

Non-conventional oil

Non-conventional oil is oil produced or extracted using techniques other than the traditional oil well method. Currently, non-conventional oil production is less efficient and some types have a larger environmental impact relative to conventional oil production. Non-conventional types of production include: tar sands, heavy oil, oil shale, biofuels, thermal depolymerization (TDP) of organic matter, and the conversion of coal or natural gas to liquid hydrocarbons through processes such as Fischer-Tropsch synthesis. These non-conventional sources of oil may be increasingly relied upon as petro motor fuel for transportation when conventional oil becomes "economically non-viable" due to depletion. Conventional sources of oil are currently preferred because they provide a much higher ratio of extracted energy over energy used in extraction and refining processes. Technology, such as using steam injection in tar sands deposits, is being developed to increase the efficiency of non-conventional oil production. (from wikipedia)

2008. május 4., vasárnap

About alternative fuel source

(from Wikipedia) The definition of alternative fuel varies according to the context of its usage. In the context of petroleum substitutes, the term 'alternative fuel' can simply any available fuel or energy source, and does not necessarily refer to a source of renewable energy. In the context of environmental sustainability, alternative fuel often implies an ecologically benign renewable fuel. Often, they produce less pollution than gasoline or diesel. Alternative fuels, also known as non-conventional fuels, are any materials or substances that can be used as a fuel, other than conventional fuels. Conventional fuels include: fossil fuels (petroleum (oil), coal, propane, and natural gas), and also in some instances nuclear materials such as uranium. Some well known alternative fuels include biodiesel, bioalcohol (ethanol, butanol), chemically stored electricity (batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil and other biomass sources.