Energy Consumption and Renewable Energy Sources: A Physics Perspective, Exams of Food science

Download Energy Consumption and Renewable Energy Sources: A Physics Perspective and more Exams Food science in PDF only on Docsity! Energy Consumption and Sources of Renewable Energy Amitabh Lath Dept. of Physics and Astronomy Rutgers, The State University of New Jersey SMAP Piscataway HS, April 10, 2003 What is Energy? The Physics Definition: The capacity to do Work. So, what is Work? To produce a Force on an object to move it a Distance. Force? Accelerates an object of mass M. F = ma. Energy Use Effects Population. each dot represents 1 million people John H. Tanton, "End of the Migration Epoch," reprinted by The Social Contract, Vol IV, No 3 and Vol. V, No. 1, 1995. Settlements in Fertile Crescent, Asia, shore regions. Population Increases Gradually. More settlement in temperate shore regions. Organized Agriculture, reduction of forests. Pre-Industrial Age Population Post WWII Refined oil (gasoline) in use for transport. Nuclear power introduced. Population spreads through commercial air transport. The Recent Past, and Today. Improvements in efficiency (agriculture, medicine, transport). Air conditioning allows arid climates to be settled. The Near Future P 2020 x ? 8 billion mE o Energy effectively decoupled from geography. More Hydrocarbons 2 Carbon Atoms ETHANE 3 Carbon Atoms PROPANE 4 Carbon Atoms BUTANE And so on. Five Carbon Atoms give you PENTANE. Six Carbon Atoms give you HEXANE. Seven give you HEPTANE. Bigger is Better The bigger the hydrocarbons get: - The more energy per molecule you get from burning. - The easier it is to Liquefy them. Methane is very difficult to liquefy. Propane will liquefy at 40 below zero. Butane will liquefy on a cold winter day. The World’s Favorite Hydrocarbon Octane. Eight Carbons. The main ingredient in gasoline. Can We See the Increase in CO, Carbon dioxide concentration as measured at Mauna Loa, Hawaii. These measurements represent the globally mixed concentration. 380 370 360 350 340 330 CO, Concentration (ppv) 320 310 1955 1865 1975 1985 1905 2005 Year Source: Dave Keeling and Tim Whorf (Scripps Institution of Oceanography? CO2 Levels Historically • 1800: 280 ppm • 1850s: 290 ppm • 1850 – 1960 310 ppm • 1960 – 2000 365 ppm 10 ppm in 50 yrs (pioneer effect) 20 ppm in 100 yrs (industrial rev.) 55 ppm in 40 yrs. Does it Affect Temperature? Problem: We’ve only been looking for a few decades. Answer: Paleoclimatology: ice cores, tree rings, etc. N ot ic e re ce nt a ct iv ity Crowley et al July 14, 2000 Science, 289: 270-277 Nuclear Power • Excellent energy output: 1014 J/kg, = 10,000 gallons of gasoline. • Need good, solid containment vessels. • Final products are still radioactive, (alpha, beta decay). Need long term disposal solution. Solar Power •Sun’s main process: Turning H to He (fusion). •Sun’s output 4 x 1026 Watts (or Joules/sec). •We see ~200 W/m2 (in the US). So at 15% efficiency, 1 m2, 10 hrs of sunlight 1 MJoule/day. • Problem: Night, clouds. • Answer: Storage. (batteries, fuel cells). Wind Power • Turbines can provide ~ ½ MWatt when running. • Wind farms can have up to 200 turbines. over 500 gallons of gas/day. BBC NEWS: The Irish Government has approved plans for the world's largest offshore electricity- generating wind farm, to be built on a sandbank in the Irish Sea south of Dublin. When completed, the 200 turbines will produce 10% of the country's electricity needs. • Problem: calm. • Answer: storage.fan gearbox dynamo Fuel Cells • A simple but effective chemical reaction: 2 H2 + O2 2 H2O + Energy • Principal components: Anode, Cathode, & Membrane. • Can be run in reverse! Anode: Strips the e- from the hydrogen sends it through a wire, provides power. Membrane: Separates Anode and Cathode. Takes the proton (hydrogen stripped of e-) and pushes it through to the Cathode. Cathode: Strips O2 into two O (platinum catalyst). Grabs two protons through the membrane combine with one O to make one water molecule Fuel Cell Detail 1. Hydrogen goes to Anode, (can use hydrocarbon fuel) Oxygen goes to Cathode. 2. Anode strips electrons from hydrogen, H+ ions enter the membrane 3. Since electrons cannot enter the membrane they go through the external circuit. 4. When electrons get back to the Cathode, they combine with H+ and O to form water. membrane Office of Fossil Energy, U.S. Department of EnergyOffice of Fossil Energy, U.S. De artm nt of Energy Fuel Cell Points • Each individual cell provides ~0.7 V. Use many in a stack. • Where do you get Hydrogen? can use hydrocarbons, wastewater digesters, landfills, biomass. can also run the fuel cell backward (use solar, wind, etc. power to convert water to H and O).