SOS 314, Unit 2 Notes (continued)
SOS 314, Unit 2 Notes (continued) SOS 314
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This 3 page Class Notes was uploaded by Taryn O'Boyle on Saturday September 10, 2016. The Class Notes belongs to SOS 314 at Arizona State University taught by Dr. Jonathan Kelman in Fall 2016. Since its upload, it has received 6 views. For similar materials see Basic Energy Science in Sustainability at Arizona State University.
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Date Created: 09/10/16
SOS 314 ~ Unit 2 (Part 2) Natural gas What is it? How do we extract it? Up and coming! Made up of compressed plankton that becomes karogen o Mostly methane w/ some ethane, butane, etc. o Length of time underground determines whether it becomes oil or eventually nat. gas and increases purity (highest carbon content and burns the cleanest) Extraction o Old school vertical method, increasingly horizontal o Often more than an mile deep and a mile or so long under a cap rock o Used to flare nat. gas as it was thought to be a waste product! Wastes $ and energy, pollutes, could at least be reinjected into the ground Some still flare bc expensive to capture, cheap to come by right now, and so there's no economic incentive Fracking (invented in 1940s) o Hydraulic (using pressurized fluid) fracturing (making cracks) o Used after hole is drilled to crack the rock and release gas o Fluid is mostly water and proppant to prop cracks open, some chemicals o Estimated that 70% of US nat. gas extraction will come from fracking in the future Controversy o Requires a lot of water o Flowback (produced water) is contaminated, risk of polluting aquifers, fracking fluid have unknown chemicals (80140 tons over the course of a well's life) o Connection to earthquakes (flowback lubricates fault plates, ex: OK small quakes) o Methane leakage = green house gas Refining o Advantage: very little o Cons: can contain hydrogen sulfide (removing that = sweetening), produce SOCS when burned, smells bad, corrosive and can break down pipes o Add sulfide so it's detectable Transportation o Using pipelines, kept under pressure for movement o 1 million miles of pipes in US, can be run under the sea o Cons of pipelines: expensive, can rupture during earthquake, not practical over large distances (which is important for an island like Japan) o Liquify Natural Gas (LNG) by cooling it down, far more dense, economically viable Piped to terminal, chilled, loaded onto ships for export, warmed and piped Natural gas Making electricity pros and cons Direct burning like space heating, gas cooking How is the electricity made? o Sometimes thermoplants that just set it on fire (Ocotillo Generating Station by ASU) o Usually combustion turbines, essentially jet engines, actually gases turning blades instead of steam to power generator o Modulate which ones are run to meet demand, can start up in about 10 minutes o Efficiency: around 3540%, size: 50400 megawatt capacity Combined cycle power plant o Combustion turbine, use hot exhaust gases to boil water to make more steam > electricity, ups efficiency o Kyrene plant in Tempe and Santan plant o No sulfur emissions, some NOX, not really any particulate matter, half the CO2, variable greenhouse gas leakage o Transportation fuel? Not often yet but burns cleaner and is cheaper than diesel Not as energy dense so needs larger tank, only so many CNG stations o Amount? about 55 years of reserves at current consumption rate Overall pros: high energy content, little refining, cleanest, combined cycle very efficient, relatively plentiful, currently nominally cheap Cons: finite, still emits, methane leakage during extraction, fracking and water pollution, limited transportation (pipelines or LNG), safety, price fluctuations Should fracking be banned? My discussion board post: I would like to start by saying that I don't think completely banning fracking in certain areas is going too far. Highly populated cities with nearby watersheds need to be carefully regulated, as we've all been educated on the effects such as those shown in Gasland. However, there are many rebuttals concerning the extent of these effects as well, such as the "Will fracking put to much fizz in your water?" paper. This states that there is very little evidence to suggest natural gas leaking up through the minute cracks quickly sealed with the pressure of the earth above. As one of the most widely used and efficient sources (when processed with a combined cycle power plant especially), it would be hard to argue that we need to completely cut off all use at this time. The sulfur oxide emissions and CO2 released are dramatically less than the amounts produced by coalpowered plants as well. The various greenhouse gas leakage from pipes is important to note. This could likely be reduced by heavily regulating pipe design. Appropriate material, structure, and location should be determined carefully in order to minimize these pollutants. Improved cementing in wells could be implemented as well to reduce gas escape and the waste storage should be regulated as well. In this time, I imagine we'll be able to improve other energy producing processes to similarly efficient and cost effective levels.
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