forum solar energy
Global warming – the basic calculations?
I am looking for simple information such as how chemical energy is much more in a barrel of oil? How much solar energy can be captured by any means per square mile? If you can compare Ethanol vs. vs. photo-voltaic water bio-diesel vs. heating power a dynamo, it would be great. When solar energy is converted into what part comes from visible light, which part of the infrared and ultraviolet which part? I am asking a lot. If you do not have the answer, Perhaps you can suggest a forum or an organization that has this info. Thank you.
Crude oil contains approximately 6119 megajoules (MJ) per barrel of 42 gallons. Pure pure gasoline contains about 130 MJ per gallon, less if it is a mixture of ethanol. A metric ton of coal contains 24,137 MJ. http://www.eia.doe.gov/kids/energyfacts/science/energy_calculator.html above the atmosphere, the sun's energy contains about 1365 watts per square meter, while the square meter is at right angles to the rays sun. (A watt is a joule per second.) Down here on the ground, you have to deal with the clouds and dust, and atmospheric scattering, so you're lucky to get 1000 watts per square meter. So, theoretically, an area of square meters which is at right angles to the Sun at any time could receive approximately 43 MJ in clear weather. But a solar panel is usually only 15% to 20% efficiency, so you get much less than that: maybe 8 MJ per day. And most solar panels are "passive" meaning they do not follow the sun during the day, and are not usually the rays of Sun at a right angle, we must allow that too. Solar-to-heat conversion systems are generally the same level of efficiency than the PV (15-20%), although some recent installations of solar Stirling engines have demonstrated a direct effect as high as 30%. http://www.nrel.gov/docs/fy04osti/33875.pdf Almost all the energy from the sun is visible in the spectrum.
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