ENVS 1126 Lecture Notes - Lecture 21: Intermittent Energy Source, Solar Constant, Net Metering
23 Nov 2016
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Why switch to renewable energy: burning fossil fuels has increased co2 in the air by 40% to 400 parts per million (ppm) At present rates of use, by 2050 co2 will be 600 ppm and by 2100 it would be. Putting solar energy to work: energy comes from the sun"s thermonuclear fusion. Solar constant: radiant (solar) energy reaching earth. Ultraviolet, visible, and infrared (heat) energy is emitted. 50% of the energy makes it to earth, 30% is reflected, 20% is absorbed by the atmosphere: the amount of sunlight reaching earth is vast. Full sunlight delivers 700 watts/m2 to earth"s surface. 700 mw (equals a large power plant) fall on 390 mi2. The sun gives 10,000 times the energy used by humans. Using solar energy is difficult: using solar energy does not change the biosphere"s energy balance. Energy absorbed by water or land, in photosynthesis, or used by humans is ultimately lost as heat: solar energy is abundant but diffuse (scattered)
