Renewable Energy: Hydropower, Tidal & Waves, Solar, Wind, Biomass, Geothermal - Prof. Kimb, Study notes of Geology

Download Renewable Energy: Hydropower, Tidal & Waves, Solar, Wind, Biomass, Geothermal - Prof. Kimb and more Study notes Geology in PDF only on Docsity! Geology Notes Exam #3 RENEWABLE energy sources: hydropower, tidal and waves, solar, wind, biomass, geothermal *all but geothermal are dependant on the sun HYDROPOWER Includes hydroelectric power from turbines turned by water through a damn to tidal power where dams across bays capture the twice daily tidal surges Supplies about 6% of our electricity and probs can’t increase much because most dam sites have been built on. Clean power but has environmental issues. *Three Gorges Dam on the Yangtze River China is the worlds Largest 22,500 MegaWatts, lifespan of 70 yrs displaced over a million people and destroyed countless archeological sites Pumped storage hydropower: During times of low electricity usage the electricity is used to pump water uphill into a storage basin as potential energy for use during higher usage periods Smith mountain lake damn-560 MegaWatts pumped storage Bath County VA damn-2772 MegaWatts Problems with Dams: Limited lifespan When they fail...oh shit Effects on rivers ecosystem, environmental havoc Displaces people with the reservoir Teton, Idaho Dam Failure 1976 –tallest dam to fail 14 deaths $11 bill in damages Tidal Hydroelectric Harnesses the twice daily tidal surges SOLAR Includes passive solar systems which are just buildings that allow for maximum use of natural sunlight for heat etc: thermal mass, orientation around sun, selective shading Active solar systems: require mechanical systems like pumps to circulate air/water/other fluids from solar collectors to a heat sink which stores the heat until it is needed Large scale solar thermal-lenses/mirrors that concentrate sunlight which can heat water to steam to generate electricity Solucar, Seville, Spain-11 Megawatts Photovoltaic’s that use silicon semiconductor materials to directly convert sunlight into electricity-life spans of at least 25 years *fastest growing sources of renewable energy in the world WIND POWER Produced by the changes in heat which create air masses of differing densities. It is possible that sufficient wind resources exist in Tx, S. Dak, and N. Dak alone to generate all the electrical needs of the USA Cleanest possible fuel Turbines generate 600 kw to over 5 mw each T. Boone Pickens, is building loads of wind farms that will supply electricity to over 1.2 million Texas homes BIOMASS Is a bilological material that includes wood, alcohol (from corn), waste, biodiesel, maybs even algae ` Biofuels: include ethanol derived from the fermentation of plant material like corn, sugar cane, beets and can be used directly to power cars or also used more commonly as petroleum fuel additive. Require a lot of energy to make-net energy gain is usually negligible Flexfuel can run on any combo of ethanol and petroleum up to 85% ethanol but get less mpg GEOTHERMAL Useful conversion of the earth’s natural heat to heat buildings and generate electricity Most heat that comes close enough to the surface to be useful is found along converging plate boundaries (Japan/NZ) and diverging plate boundaries (IceL) Geysers power plant-Cali. Worlds largest geothermal electricity plant Hard Path vs. Soft Hard: business as usual, relying on ever depleting fossil fuels like coal/oil/ gas. No new thinking SOFT: finding energy alternatives that are renewable, flexible, enviro friendly Fuel Cells: hydrogen economy Are electrochemical energy conversion devices. Fuel cells convert hydrogen and oxygen that are stored separately, into water-produces electricity and no pollutants. Could take decades to perfect Like plug in cars NON RENEWABLE: w/ only 5% of the worlds population, we consume 25% of the worlds energy all fossil fuel is non renewable. 80-90% is produced from non-renewable sources a. the rock that can prevent the escape of petroleum to the surface. It caps off the reservoir rock. MUST be an impermeable, low porosity rock like a shale 4. trap a. in order for the cap rock to do its work is must be draped over the reservoir rock like a blanket, trapping the petroleum inside. Most traps are structural traps that are either anticlimes (domes) or faults 5. subsiding basin hydrocarbons are low density, light than the rock and groundwater they are in, so they slowly rise towards the surface unless they are trapped. As they work their way upwards, they may escape to the surface as a seep, the volatiles are lost and tar is produced. Petroleum exploration: exploring for oil and gas has become an incredibly complex science, technology, and artful enterprise. Use of seismic surveys (using sound waves that reflect and refract off different earth materials) has become indispensable Petroleum production: most oil and gas today is recovered by drilling holes into the ground either on the land or more and more often even in hundreds of feet of water on the continental shelves Use of rotary drills (drill bits with rotating teeth covered with diamonds) at the end of 30/60 ft pipes. Drilling fluids and mud are pumped down the center to fool the pipe Primary recovery uses the natural reservoir pressure to force the oil to the surface and some additional pumping; maybe 25% of the total reserve below ground. Secondary and enhanced recovery involves techniques that enhance production of some of the remaining more recalcitrant oil: up to 60%. May include injecting natural gas, water, steam, CO2, or chemicals back down into the well under pressure and then pumping the oil out. Oil recovery always includes a lot of salt water which must be disposed of by injecting it back down as part of secondary recovery or letting it evaporate in ponds Exxon valdez-1989 11 million gallons of crude oil..spill Natural gas: almost always found with oil and can be burned off or recovered and pumped for hundreds of miles. It is the cleanest, most easily handeled, and provides the most BTU per weight of any fossil fuel. Its also used in the production of plastics, detergents, drugs, and fertilizers and can be liquefied as LNG and transported by double hulled ships Other sources of petroleum Coal bed methane: gas found with coal: enough to supply us with years of natural gas Methane Hydrate: a white, ice-like compound of frozen water and natural found in sediments on the very deep sea floor; will be difficult to extract Oil shales & tar sands: large deposits of sedimentary rocks that contain organic-rich kerogen (oil shales-lake deposits) or asphalt (tar sands). Large deposits in western states and will cause many environmental problems Peak Oil-Hubbert Peak Rate of production of nonrenewable resources follows a bell shaped curve reaching a peak of production followed by a decline. When consumption exceeds production, shortages result. Fossil fuel and acid rain: major environmental effects 1. damage to vegetation due to the effects of acid on the solids fertility 2. lake ecosystems are drained of their nutrients by the acidic water leading to the loss of aquatic plants and animals 3. damage to human structures as acids deteriorate materials, especially limestone and marble structures Nuclear Energy 1. fission: breaking atoms apart, what we have today 2. fusion: joining atoms together-promise for the future Fission: Splitting of uranium or plutonium by neutron bombardment releases fragments of atoms, 3 nuetrons and heat. The released neutrons strike other uranium nucleuses which split them releasing more neutrons and heat. A-bomb(fission bomb atomic) Rapidly bringing together subcritical masses (won’t produce uncontrolled chain reaction) of uranium or plutonium to create a critical mass will produce an A bomb H-bomb (fission bomb hydrogen) Uses a very high temperature fission weapon as a trigger to fuse the hydrogen together. Produces much more energy than an A bomb Fission: three isotopes of uranium occur in nature U 238/235/234 As only U 235 works as a fissionable material for reactors, it must be concentrated to around 3-4%-enriched uranium, a difficult process Enriching Uranium The mix or uranium isotopes must be converted into a gas to enable the isotope separation. More highly enriched uranium is also used to make research reactors and medical isotopes, not just bombs. Fission: U238 is not naturally fissionable but it can be bombarded by neutrons and converted to P 239 which is fissionable. This is done with a breeder reactor and is a very easy way to make weapon-grade material. A breeder reactor makes more fissionable material than it uses. It is estimated that the waste or depleted u238 already produces could produce enough p239 to supply the total electrical energy demand of the US for 100 years Where does Uranium come from: Uraninite or pitchblende are the major ores uranium. U occurs at about 2 parts/million in the earth’s crust. Originates in igneous magma and is concentrated to about 4 parts/million in granites Many ore deposits are in sandstones where is was leached out of granite by groundwater and then precipitated in the sands under low o2 conditions The uranium ore is milled (ground to powder) and leaches with sulfuric acid to produce “yellow cake” Coles Hill Deposit, Pittsylvania Co, Virginia Over 110 million lbs of ore worth over 10 billion dollars. Largest in usa Nuclear reactors: Containment structure: reinforced concrete protecting the reactor Reactor vessel: stainless steel, contains control rods, moderator, fuel rods Fuel rods: contain enriched uranium oxide fuel pellets Control rods: boron absorbs neutrons to slow or speed the chain reaction Moderator: graphite or deuterium (heavy water) surrounds the fuel rods to slow the neutrons enough so they can be captured by the u235 nucleus Plumbing: primary coolant loop takes the heat from the reactor and transfers it to the steam generator, secondary loop transfers it from the steam generator to spin turbine-generating electricity Cooling tower: cools the water from the turbine in order to make it an efficient heat engine Three mile island: most serious nuclear accident in US occurred in PA in 1979. Malfunction of pumps in the cooling system compounded by human error resulted in a partial core meltdown but the containment structure only allowed a small escape of radiation into the environment. 1.5 billion clean up Chernobyl Worst nuclear accident. Ukraine 1986. Batched test to test the failsafe systems and faulty equipment designs. They were turned off draining the water