Geol101 Lecture 15b and 16
Geol101 Lecture 15b and 16 Geol101
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This 11 page Class Notes was uploaded by Shelby Green on Thursday April 14, 2016. The Class Notes belongs to Geol101 at Clemson University taught by Dr. Coulson in Spring 2016. Since its upload, it has received 23 views. For similar materials see Physical Geology in Geology at Clemson University.
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Date Created: 04/14/16
3/12/16 Geol Lecture 15b Nnonrenewable Energy Geology in the News Antropocene hypothesis has new evidence human activity changing earth strata forming today contain noticeable evidence of human activity Nuclear Energy • Fission- splitting of an atom • Releases a lot of energy in the form of radiation • Have to harness the energy safely Nuclear Fuel Uranium Ore (high concentration) Yellowcake: processed uranium 235 238 U isotopes ( U vs. U) separated o Centrifuges: separate isotopes o U-235 produces the power 235 238 Want the fuel enriched in U relative to U o Filter out enough 23U (235U is good) Power plants: 3-5% enrichment Weapons: 90% enrichment o UN samples materials to see if fuel is enriched 3-5% Why is 235U needed? o Firing neut235s takes time and energy o Splitting U atoms starts a chain reaction By product, 3 extra neutrons hit/break down uranium atoms that release 3 more extra neutrons continue Neutrons good for energy 23U doesn't produce neutrons (have to produce energy themselves) Nuclear Power Generation • Chain reaction is controlled • Control rods soak up/catch extra neutrons before they can break down too much uranium and create too much energy • Cooling system has water run through and remove the heat energy • Requires lots of water • 4 million gal/yr in some plants • “Smoke takes” = cooling towers Cooling tower that is releasing heat as steam and Nuclear Advantages • Large US Reserve (supply ready to use right away) • Estimated 130+ yr supply assuming current production rate • Reduce Carbon emissions • No combustion • Decrease fossil fuel dependence • Produces tremendous amounts of energy • 1 kg of U produces 3 million times more energy than 1 kg of coal • Good safety record*** • Misconception that nuclear power is extremely dangerous Current US Use • ~100 plants, ~20% of US electricity • Use declining since 1996 • Half the active plants will close by 2020 • No new reactors ordered between 1978- ~2010 – The plants built during this time were approved before 1978 – 48% of the ones ordered before ‘78 were never built • These numbers tell us something is odd… Nuclear Disadvantages • Nuclear electric price tripled between 1970-1990 • Reactor safety • Nuclear proliferation (ppl using power pants as a cover story to build weapons) – Iran: making electricity or making weapons? • Nuclear waste disposal – Not carbon but other by products that are dangerous Radioactive Waste • Avg power plant creates 25-30 tons of waste per yr • 2007: US has 50,000 tons of stored radioactive waste • Radiation levels vary, so safety protocols also vary Types of Nuclear Waste • Low Level (LL) Waste: little levels of radiation, relatively safe, stuff that was not radioactive to begin with but was exposed to radiation • Ex: tools • Class A-C: each letter has a higher level of radiation associated with it • GTCC (called Intermediate Level in Europe): Greater than Class C • High Level (HL) Waste: weapons research and the remains of uranium that produced energy • Main type from power plants/weapons rsch • Heavy shielding & deep burial • Globally we generate ~ 12,000 tons/yr Types of HL Waste • Spent Nuclear Fuel: fuel/energy cell that is taken out of power plant and replaced – ~20 tons/yr/plant • Trans-uranic: isotopes that are high on the periodic table, greater than 20 yr half-life – Emits radiation for a long period of time b/c how long its half life is – Generated primarily during weapons research What do we do with radioactive waste? 1. Store It Want to ensure stability and safety Very few storage facilities in this country • Only 3 sites in the entire US for LL waste • Clive, Utah Only accepts Class A • Richland, Washington Accepts Class A-C from 11 NW states • Barnwell, South Carolina Class A-C waste from the other 39 states until 2008 when it closed it gates to all but 3 states (Kentucky and New Jersey) • Barnwell ran out of space to store things b/c those two states offered enough cash • HL waste Sites • Yucca Mountain in Nevada: US’s 1 site for spent nuclear fuel • Supposed to open in 1985, still not started… • Geologic concerns (faults, seismic activity) • Can’t predict earth quakes, can’t predict the risk • Legal challenges: “not in my backyard effect” • Everyone wants the benefits, but no one wants it in “their backyard” • Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico • Only US site for trans-uranic waste disposal • 20 yrs planning • 1999-2006: over 5,000 shipments deposited • Buried about ½ mile into the ground carved into 3,000 ft thick salt deposit • Walls made out of halite b/c of it is impermeable • Containers cannot be high-temp, cannot contain fluids, and must be ventilated to prevent explosion • Long term Plans at WIPP • Site expected to be full by 2070 but onitored for safety until 2170 • Marked as off-limits for drilling, excavation, & development until 12,170 (!) with stone pillars carved in 12 diff languages (10 thousand yr period) 2. Dump in the Ocean • Ocean connects to everything • Radioactivity could contaminate the water and the animals we rely on for food • Also, the ocean temp is not regulated and the pressure of the ocean would smash the container 3. Put in subduction zones • Plates move slowly (3 cm per yr) 4. Launch into space • Accidents happen • What if rocket carrying radioactive material explodes before it reaches space? 5. Transmutation: instead of using it as waste, use it as a resource • Big in 1970s until banned in the US • Current137being re-visited, especially in Europe • Cs used for food irradiation (generated from bomb research during the cold war) • Killed microbes on food not enough radiation hurt anyone • 241Am used for smoke detectors • The decay detects smoke Radiation Levels • Many ways to measure radtion – Lots of units easy to get confused • Curies, Becquerels, Grays, Rads, Sieverts, etc • Rem: dose (or amount) x quality factor’(how likely it will cause biological problems) for a particular radioactive material Background levels • Annual exposure from natural sources in millirems (mrem): • Cosmic rays- 30 • Radon- 95 • Medical- 100 • Fallout- 4 • Terrestrial- 55 • Total = 284 mrem (= ~ 0.3 rem) How much is safe/unsafe? • (per episode of exposure) • < 5 rem/yr: no problems • 5-20 rem: possible long-term problems • 20-100 rem: mild radiation sickness (ppl don't even know they have it) • 200+ rem: hair loss, 1/3 chance of death • 600+ rem: 100% fatality rate w/in 14 days Contamination • 108+ sites in the US are considered unsafe due to radioactive contaminants • Accidents, mismanagement, unsecure storage • Ex: Oak Ridge Natl Lab, TN – Over 167 sites where contaminants were released Reactor Failure • Three Mile island Accident: • Pennsylvania 1979- partial core meltdown when the cooling system failed • No serious radiation release (still debated) • Why there was a 30 yr gap in nuclear power plant production • Chernobyl Accident 1986 • They were testing the emergency plan • Fallout 30x > than the bombs dropped on Japan • 336,000 people permanently evacuated • 19 mile exclusion zone still exists 3/14/16 Lecture 16 Renewable Energy Geology in the News Estimated 75% of species going extinct leave no fossil record Implications for modern species going extinct without ever being discovered by scientists Renewable Energy Sources • Lots of types being studied to help reduce fossil fuel use • General Points: 1: Each has advantages and disadvantages – No ‘magic material’ that comes without any drawbacks 2: No one source will provide all our energy needs – Need a varied approach Advantages • Abundant • Produce little pollution • Low maintenance • Safe Disadvantages • Technology still being developed • Takes time and money to improve strategies • Expensive • Because we’re having to invest so much to improve them • Infrastructure compatibility • Most buildings aren’t built to run off renewable energy sources • Acceptance by society Solar Power • If we were to capture all the sunlight on earth for 1 hour = a year’s supply of energy • How can we harness solar energy? Solar Farms • Use mirrors to focus/reflect sunlight onto a receiver • Receiver has a high heat capacity like salt traps heat energy puts it to use • Photovoltaics (PV): soaking up light and immediately turning it into electricity • Sunlight on material soaks it up electrons nock around into a current electricity • Kind of inefficient… • Takes a lot of sunlight to make even a weak current of electricity • PV Cells: materials used for PV • Constantly improving tho New organic material being studied • Use ~ 7.5% of the Sahara desert as solar farms = provide half the world’s energy needs • Assumes 10-15% PVC efficiency Solar Use • Energy Payback (EPB): amount of time it takes you to generate enough energy to offset the power you used to get started • Solar Power Since 2000 solar’s EPB has dropped to 2-3 yrs Disadvantages • Insolation Variations – If it rains for a few days and everything you have runs on sunlight… – Night time – Cloudy days • Some pollution from making older PV cells – Ex: cadmium = good flow of electrons • Cadmium is harmful to lots of organisms when disposed • Already been fixed • Where to put solar farms? – SW US is prime real-estate but there are a lot of state parks/wildlife reserves • Companies are trying to get the gov’t to allow them to build on the reserves to save money instead of actually having to buy land Hydroelectric • Flowing water used to turn turbines that generate electricity • 6-7% in US already Advantages • Doesn’t pollute the water • Quick profit: ~ 5 years to recover plant construction costs via sale of electricity Disadvantages • Reservoir creation floods areas – Area has to be evacuated by both animals/humans • Dams alter downstream environments – Sediment gets deposited at the dam instead of being carried downstream • Erosion problems • Fish population crashes without sediment to lay their eggs • Site selection – Efficiency: Most prime places are already taken so the places left wont be very efficient – Safety: • If dam breaks… • When reservoir floods… Case Studies: Banqiao Dam in China • Built to resist a 1,000 yr flood event • Aug 6-7 1975: experienced a 2,000 yr flood event. – Area typically gets 41+ in/yr but rained that much in 24 hrs • 700 million tons H O2released in 6 hrs – A wave 6+ mi wide and 20 ft high killed 171,000 died Hydroelectric: Tides and Waves • Convert kinetic energy into electricity – Magnet up down motion generates electricity • Old devices too complicated • New buoy system is just 2 components Specific Advantages: – Simple device – Very consistent: waves are consistent Concerns – Rough environment: salt water corrosion, storms/hurricanes, wildlife could have bad effect on devices – Changes coastal environments – Reduces wave energy – Some areas aren’t very close to the coastal (ex: Kansas) – Effects on wildlife: device could have bad effect on wildlife Wind Power • Winds generate ~ 5x more power than total global energy consumption • N. Dakota could provide 1/3 of US electrical needs • 2008: wind generates 1.5% of global electrical supply – Percent of power generated by wind… • > 20% Denmark, ~15% Spain & Portugal, > 10% Germany & Ireland Advantages • Cost down 80% in last 20 years (disputed) • Energy Payback only ~ 1 yr Disadvantages • Not consistent in many areas – Areas defined by classes 1-7 (7 being best) – Anything less than Class 3 = wind energy not viable • Best sites often far from population centers • “Not in My backyard” syndrome – Home turbine = 30 ft tall, blades 7-25 ft long – Industrial turbine = 20 stories tall, blades about 100 ft long Case Study: Cape Cod, MA • People objecting to a windfarm that would be built 5.5 miles offshore • “Ruining our view” WARP Turbines chancing the design of wind turbines – Wind Amplified Rotor Platform • Each platform has several mini turbines on it – Just as it not more efficient than old turbine – Is it safe? • Concerns about birds being killed • Gov’t has reduced fines for wind farm bird deaths for the next 30 years (if they kill protected/endangered birds) • On avg. wind turbines kill 1 bird/yr • What about other flying animals? Biofuels • Use of biological materials as fuel – Ex: wood • Renewable IF managed properly – If you chop down all the trees without replacing them, it would take a while for the area to recover Algae • Grow algae, then convert their lipids into biofuel • Extract lipids (~oils) after algae dies • Algae farms = oil crops Advantages • Doesn’t need freshwater – Can use water that you wouldn't drink • Doesn’t need cropland/soil – Not taking up any crop land • Waste is biodegradable – No harmful by products • Multiple harvests per year – Can yield 15-300x more energy per acre than other biofuel crops (ex: corn grown for ethanol) • Ex: corn grown for ethanol Disadvantages • Currently expensive – New technique published in Dec 2013 that are improving efficiency • What’s best algae species for the most algae? • What’s the best angle to grow the algae from the light? • What’s the best temp to grow it in? • Doesn’t lower atmospheric CO level2 as some claim – Photosynthetic (take CO2 out of atmosphere for photosynthesis) – BUT when algae dies, gets harvested, and lipids extracted, the CO2 is released back into the atmosphere Conclusions • Every energy source will work well in some places but not in others • Utilize several different ones – Wind turbines in North Dakota – Geothermal near Yellowstone – Tidal buoys on the West Coast • Have to accept some drawbacks – Weigh the pros and cons to decide what is best
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