Steam enters a turbine at 450 lbf/in.2, 900 F, expands in a reversible adiabatic process, and exhausts at 130 F. Changes in kinetic and potential energies between the inlet and the exit of the turbine are small. The power output of the turbine is 800 Btu/s. What is the mass flow rate of steam through the turbine?
3/22/16 Lecture 13 Groundwater and Rivers Hydrology Why do we care Water is resource we cannot survive without There is a fixed amount of water on Earth (limited resource) Hydrologic Cycle Notice how much water is in each step… o Ocean is the main major reservoir o Glaciers is second major reservoir o Groundwater supply is the third major reservoir Notice how much smaller the water source is in rivers and lakes Groundwater Runof: water runs off the surface of the earth Infiltration: water soaks into the ground and makes its way deeper and deeper Infiltration Properties Porosity: how much void space is present in an area (measured in percentage) o 3 main types Intergranular porosity happens when the pores all intergranular pores or pore spaces in-between grains that water can seep into accumulate with water and creates a decently large porosity Fractures: cracks rock that water can seep into and fill Vuggy porosity happens when vugs or a part of the rock dissolved away and allows water storage in the hole created Controls on Porosity Determined by sediment/rock properties: o Sorting: well sorted sediment tends to have high porosity, poorly sorted sediment has lower porosity o Cementation: higher cementation, lower porosity and vice versa (cementation is when a new mineral fills the gaps between grains of the other material) o Permeability: measures how easily the water can flow through the sediment material, higher permeability higher porosity Groundwater (GW) Water Table (WT): water goes deeper and deeper until it can’t go any further, than begins to fill up the pores from the base up (why the base is the saturation zone) o Above water table, pores spaces are mainly empty o Below water table, pores spaces are mainly full Aquifer: any layer of sediment/rock that will holds a water supply **Recover for human use via wells o Unconfined aquifer: body of water below the water table that o Aquitard: impermeable layer that acts as a barrier to keep the water in aquifer from sinking lower o Confined aquifer: an aquitard above and below the aquifer makes a barrier that doesn't allow water to be added to the aquifer o Artesian well: confined aquifer on slope has more pressure at the base of the slope, so drilling into the aquitard at the base of the slope will have enough pressure to push the water up (no need to building a pump thus a cheaper well) o Perched Aquifer (Perched WT): secondary aquifer perched halfway up a hillside because of an impervious layer that keeps is from reaching an aquifer down below (relatively small) Question: Where should town build a new mall Site A or B 10 km A TOWN B Answer: Water needs a recharge area; so do not build over the recharge area b/c that will prevent the water from reaching the aquifer below. o People will want site A b/c it’s closer to town so to settle dispute, look for third option (site C could be in-between A an B on the right edge of town) Water Supply o Recharge: the amount of water added back into aquifer o Discharge: the amount of water is flowing out of aquifer (natural or man- made discharge) o If Recharge > Discharge, water table rises Can cause difficulty with construction when building foundations o If Recharge < Discharge, you’re overdrafting Effects of Overdrafting o Cone of depression: depressed the surface of the water table close to the well so the well can run dry even if there is water left o Cone stops growing when flow from the well balances water pumped from well o Subsidence: ground level sinking (diagram below) Dates on the pole show how much the ground level has changed over the years. Change is not from erosion but from subsidence o Salinity Contamination: salt water can contaminate the aquifer o Desalinization: filtering the salt out (expensive, requires a large plant) Water bills higher for residence who live near places that deal with salinity contamination GW Movement Typically GW moves very slowly o Good: groundwater tends to stay in one spot for a long time so the water supply will be around for while o Bad: when water gets contaminated, it sits and stays contaminated for a long period of time (no water flow to flush contamination out) Erodes even at slow speeds o Groundwater carries dissolved substances CO2 and SO2 Dissolve carbonate rocks o Threat of sink holes Case Study: Groundwater Contamination Love Canal, Niagra Falls NY Early 1900s: a canal system was started to connect to a river but never was finished o Canals lined with cement 1940s: chemical plant bought canals to dump their chemical waste product o Buried it with fine grain sediment o Fenced if off an called it a day 1960s: love canal had a lot of house development o The people bought the land from the chemical company decided to build on the property despite it was where the chemical waste had been dumped o Sold for $1 o Wet rainy season caused the water table to rise, so the contaminated water started moving closer to the surface 1970s: health issues increased for the people living in the love canal area o Birth defects, asthma, cancer, etc. 1978: local homeowners learn there’s 21,000 tons of chemical waste underground o Who’s responsible o Situation was so bad that children would get chemical burns from playing in the grass Aug. 7, 1978: Federal declaration of emergency to evaluate the people in some of the neighborhoods (same declaration as 9/11 very serious situation) 1980: Superfund Act allowed for government money to go to the cleanup of contaminated area 1994: legal proceedings drug out until for 16 years until finally the chemical company was held responsible, and everyone promised never all this situation to happen again 2008: YET survey of 4 states found 500,000 kids are in schools less than ½ a mile from waste dumps, including one on top of a PCB dumpsite (PCB has high correlation with cancer) 3/29/16 Geology Lecture 14 Coastlines Geology in the News Mt Pavlof in Alaska is erupting Ash being spewed 37,000 ft high 3 eruption in 3 years Rivers and Streams Why should we care Major agent of weathering and erosion Forming a River Drainage basin: area on either side of river where water is flowing down into that particular river o Water has to flow downhill – duh Channels: carved out path that water will flow o Water likes the flow the easiest path it can V-shaped valley: V shape of a valley that was formed by a river flowing through Tributaries: a river or stream flowing into a larger river or lake. o Branching/dendritic: branches of tributaries that all flow into one larger river o Radial: hill/mountain that tributaries are flowing down, the white area in the center is the peak of elevation o Rectangular: fractures/joints in the rock that the tributaries follow Levee: naturally raised area on the banks of the river made by natural sediment deposits Floodplain: flat plain where the water will go if it floods over the banks of a river Channels Braided streams (or braided channel): multiple channels that have been molded together o Causes: Variable discharge: the amount of water flowing through the area changes a lot, multiple channels added to help obtain any extra water Large sediment supply: too much sediment will clog the river, and the water will have to find another route around the natural made dam Easily erodible banks: water continually erodes its banks and spreads out Steep elevation gradients o Channels tend to be straighter with steep elevation gradients b/c the amount of water/the speed of the water increase the energy and allows the river to cut/erode through the rock Lower gradient o Channels start to meander with lower gradient (each loop called a meander) b/c lost velocity/energy so it has to flow around rocks/obstacles instead of eroding through them o Meanders Cut bank: in a curve of river, water on the outer side of curve moves faster and causes erosion Point bar: water on the inner part of the curve that is moving slower and cannot cause erosion Compare this concept to race cars going around the bend o Meanders migrate over time Oxbow lakes (oxbows): as the meander migrates, a meander can be cut off from stream/river and left to dry (seen in time 4 of diagram above) o Meander vs. Man Meandering causes problems for people Artificially straighten, but that also causes problems Can increase water velocity and eventually causes flooding Floods How much water moves part a point in a given amount of time o Discharge = velocity * area If Discharge increases until channel cannot contain all the water, flooding occurs Floodplain development Floods deposit lots of fine-grained sediment o Good for farms b/c sediment is nutrient rich o Bad for developed areas b/c the damage that comes with flooding “How often and how big are the floods here” Recurrence interval: probability that a flood of the given size is going to hit that area in any given at time o Probability in a given year = 1 / interval Example: Q: What is the probability of a 5-yr flood happening this year A: 1 / 5 = 0.2 20% o Caveats about interval (warnings): Probability calculation, not a guarantee Varies from river to river Practice Problem: You buy a house along the Honey Badger River. Your property would be affected by a 50-year flood event. What is the probability of a 50-year flood event occurring this year along the Honey Badger River o 1/50 = 0.02 ~ 2% The End of the River • Mouth: where the river is emptying out into a body of water • Erosion ends, deposition starts • Distributaries: when the main channel breaks into many smaller channels • Deltas: distributaries/mouth all create the delta of a river Delta Processes Subsidence: excess weight of the sediment causes area to sink lower than sea level o Ex: Venice built on a delta, weight of sediment + weight of construction has caused flooding Water Quality and Availability An average adult can survive on 2-3 Liters/day For cooking, bathing, sanitation, we need about 50 L/day/person Average per capita use in US ~ 6,000 L/day o Agriculture influences that 6,000 o Manufacturing does too Water Quality Potable: water that is safe to drink and tastes good o Almost all water supplies contain some dissolved material o Question is whether a given amount of the material is safe Biological Contamination • Microbes can enter drinking water supplies • Fecal Coliform Count: o # of coliform bacteria per 100 ml o Coliform bacteria used as a proxy o Drinking water = 0 o Swimming/etc = 200 Chemical Contamination • Chemicals commonly added to water via infiltration and runoff o Pesticides o Fertilizers Radiation can also enter water supplies o Mines o Waste disposal Water Quality Clean-Up • Clean-up possible but difficult o takes time & money • Faster recharge = easier to clean once contaminant source is isolated o ‘Fast’ recovery = matter of years Water Availability • Legal fights among states over who gets how much water from a reservoir • ‘Downriver’ states suing ‘upriver’ states for taking too much • Upriver states say old water use agreements are outdated CASE STUDY: SC vs NC • 10 million gallons from the Catawba River annually • Catawaba R accounts for about half the water supply to the SC low country • Taken before US Supreme Court • SC & GA are in contention over the Savannah River CASE STUDY: GA vs TN GA state legislature has proposed legislation to move the state border about 1 mile north Claim is based on an 1818 surveying error placing the border at the wrong location CASE STUDY: Everyone in the SW US vs Everyone else in the SW • Colorado River lawsuits date back to 1931 o CA, AZ, NV, NM, UT, & Native American groups Colorado River Overuse • Providing water to 30 million people • 70% of its water diverted to irrigate 3.5 million acres • 10 years of drought • Water level down 130 ft since 2000 in some areas • Flow est. to drop 5-20% in next 40 yrs due to climate change • Ends 50 miles before even reaching the Pacific Ocean • Delta reduced from 3,000 acres to 250 acres in < 100 years Future Case: Water Wars • What happens in areas where courts aren’t available to settle disputes o 2000: 36 nations are defined as ‘water stressed’ (< 1700 m 3 H2O/person annually) o 2010: 1 billion people in water stressed regions (16% of pop-) o 2050: Est to be 2 billion (22% of pop-) 3/5/16 Geology Lecture 14 Coastlines Geology in the News: Fossil of rare Siberian rhinoceros found Why should we care About 53% (> 3.5 billion) of the world population lives within 120 miles of a coastline Coasts Remember- still on continental crust! Several forces acting on these environments Coastlines are very complex systems. Several processes interact together to create this environment. If one element is changed, the entire system Coastal Processes Tides: water level changing every few hours (higher/lower) covering more land as it comes in, and exposing more land as it recedes o High tide: sides facing towards and away from the moon o Low tide: the in-between sides Tidal flats: when the water recedes for low tide, tidal flats exposed Tide height: Hawaii has a tidal range of 1-2 ft Bay of Fundy has a tidal range of about 40 ft o If your coastline is well connected to the ocean, the tidal ranges are very small (Hawaii surrounded entirely by water well connected) Waves: o Wavelength: how closely spaced are the waves Changes as wave gets closer to shore… Decreases speed: seafloor creates friction (occurs when water depth gets to about half the wavelength) Wavelength decreases: waves get closer together Waves get taller and starts to roll over and break Wave refraction: waves change direction as they move into shallower water o One side of wave gets to shallow depth earlier, slows down earlier other side catches up b/c its deeper and moving faster until it hits the same shallow depth Wave refraction Longshore current: water movement that moves parallel to the shoreline o moves on and off shore, being bushed back and forth by the waves Longshore drift: sediment movement with the longshore current Shoreline Features Shoreline features depend on: o Tectonics o Rock type o Sea level fluctuations Stack o Storm size/strength Types of Coastlines Emergent Coastlines: uplift occurring, so more areas are emerging above the sea level o Stacks: small islands that tend to be very steep a hill that has been submerged underwater, and its peak is exposed above water level o Terraces: wide flat areas that resemble stair cases (each stair is a different age as time goes by, sea level has changed) Emergent Coastline Submergent coastlines: most of the coastline is submerged appears to be flooded o Long, wide beaches and coast plains (SC coastline) o Spit: elongated sand body that is still attached to shore Lots of sediment deposition o Barrier Islands: elongated sand body that is not connected to shore A lot of the Spit southeast shore Move around/change frequently & rapidly bad for building Barrier Island Offshore Features Continental margin: edge of continent underwater Depends on whether or not it is near a plate o Active: continental margin is also edge of continental plate o Passive: continental margin that is not on the edge of continental plate Continental Shelf: landmass which extends from a continent, resulting in an area of relatively shallow water known as a shelf sea o Water is shallow/warm, sediment deposits from rivers, nutrient rich water, lots of biological activity (sea life) Economically important Best fishing (“all you can eat buffet for fish”) Oil and methane gas found on the continental shelf Continental Rise: the very end/edge of continental margin (could be several miles off shore) (see diagram next page) Coastal Erosion Can occur along any type of coasts Emergent and Submergent coasts o Threatening for construction along coastlines Erosion is a natural process so its not a bad thing it just becomes a hazard when people don't consider erosion occurring when they’re building CASE STUDY: Cape Hatteras The Outer Banks of NC o Strong longshore currents: a lot of sediment transported from one end to the other end of the coast The Cape Hatteras lighthouse o 1868: built 1500 ft. inland 1998: just 120 ft. from the ocean Q: What was the average rate of erosion in this area from 1868- 1998 o 10.6 ft./yr To save the lighthouse, in 1999-2000 it was moved 2900 ft. inland over the course of 23 days o Cost: $15 million How to deal with coastal erosion… o Zoning: Build farther inland Setback distance: how far away from the shoreline is it considered safe to build Erosion lines (aka E lines): line along the coast marking where erosion will move the shoreline to in the future Formula: erosion rate x interval = E-line distance EX: you want to know where the coastline will be 10 years from now o Given: erosion rate = 10 ft/yr o 10 ft/yr * 10 yrs = 100 feet How far inland should the setback distance be in order to keep buildings safe National: E-60 line (most construction current day is expected to last 50 yrs) SC: E-40 Why doesn't SC use the E-60 line o Tourism: the #1 revenue source for SC 2010: ~$18 billion for SC b/c of tourism o Barriers Protect the shore in one of two ways… Weakens Waves Keeps sand from moving away Types of Barriers: Seawalls : takes the blunt of the waves hits o Very effective soak up wave energy o Expensive to build/repair o Not very scenic Groins: walls build perpendicular to shore built to mess up the longshore drift so the sediment stays o Expensive to build o Need a series of groins, not just one o Hard to get permission to build b/c the problems they cause o Beach (Re)nourishment Replace the eroded sediment Some wildlife issues o Natural beach sand is ideal (light and fluffy) for wildlife to move through it o Added beach sand tends to be more compact and makes it harder for wildlife to move through Ex: turtles have a hard time digging down in the sand either give up, or burry their eggs to shallow CASE STUDY: Miami 1950s: erosion washed out the sand and the water was coming up right next to the buildings 1980s: replenished beach with beach nourishment o Expensive but tourism made up for the cost New Jersey 1980s: tried to copy Miami o 5 million dollars of sand added to their coast o A few years later, all the added sand was gone New Jersey had diff environment than Miami Geologist studied these differences With geologists help, New Jersey tried again and was successful 3/7/16 Geol Lecture 15 Nonrenewable energy Geology in the News Archean Eon glaciation (3.5 Ga) may have been greater than previously thought Why do we care Everything we use almost requires a source of energy Effects our economy, politics, etc Energy Sources 1. Renewable: replenish themselves fast enough for human consumption a. Ex: sunlight 2. Nonrenewable: either do not replace themselves or replace themselves slowly on geologic time scales Fossil Fuels • ~ 82% of energy consumption in the US and globally (by far the most important source we have) – Coal = 22.6% – Oil = 36.8% – Nat gas = 22.9% – Hydroelectric = 6.3% – Nuclear = 6.0% – All others = ~ 1.4% • Reserve: the amount of the material you have for immediate use • Resource: the total amount of material whether you can use it or not • General Advantages – Historically, cheap & abundant – Technology (techniques) well developed – Infrastructure built to run on them • General Disadvantages – Nonrenewable – Deposits not uniformly distributed • Some countries have huge amounts of fossils fuels while other ones have none – Costs going up – Environmental damage • Climatology/global warming/health issues • Hydrocarbons: things you can combust/break down/burn – Combustible H-C compounds – Requires: • Area of high biological productivity (plankton type creatures) • Relatively low oxygen in waters/sediments (just deep enough) • Ex) continental shelves 1. Methane aka Natural Gas – Advantages Resources growing in recent years Don't have access to many of these deposits right now Burns much cleaner than other FFs 30% less CO e2itted per unit energy compared to oil Price often cheaper than oil – Disadvantages Safety issues. Sour gas (contains H 2 or dihedron sulfide) that you don't want to burn NG heat system malfunctions can create CO as a byproduct CO build up is deadly) Still contributes to atmospheric C0 2uildup 2. Oil – Oil Window (ideal oil conditions) Hard to form needs to be 2- 5 km down and < 150°C – 62% is in the Middle East 22% in Saudi Arabia alone 2.5% in the US (enough to sustain us) – The US uses 7.5 billion barrels each yr 2010: US had to import 61% of the oil we needed – Cost of that 61% = $337 billion $640,000 per MINUTE $48 million during this class – US Oil Production and Consumption The gap has grown for decades… 1973: importing ~50% 2007: importing ~75% 2004: importing ~66% 2010: importing ~61% – Fracking: Uses pressurized fluids to shatter rock below ground (creates permeability for oil to be pumped out) We’re seeing a boost in production in the past couple of years due to fracking. Advantage: o Gets oil out of areas where traditional drilling cannot Disadvantage: o Contamination: fluids used for fracking are not pure H2O May 2015: water supplies in PA contaminated with fracking fluids Fights over regulating the industry (regulations will prolong the process) o Seismic Activity: increases earth quake activity (magnitudes 4 and 5) Oklahoma looking at putting restrictions on fracking b/c of the amount of issues/seismic activity in their state – How much oil is left Debatable o Lots! Find new deposits Improve technology to get more out of deposits o Little! Existing fields producing less New oil fields being found less often – CASE STUDY: ANWR Arctic National Wildlife Reserve Resource estimated to be = 20-30 bbls (billion barrels) Reserve estimated to be = 4-12 bbls (billion barrels) Q: Should we drill for oil in ANWR PRO-drilling o 30 bbls = enough to last the US 60 years! o US free us from foreign oil o Lower gas prices o Tiny area affected ANTI-drilling o Only 12 bbls…that’s not even enough to fuel the US for even 2 years! o Spills devastate the environment Problems with pro-drilling side… “30 bbls = enough to last for about 60 yrs” assumes all 30 billion barrels are available “Would free us from using foreign oil” o By their numbers, ANWR would produce… o 30 billion barrels / 60 years = 500 million barrels/yr o The US imports ~ 5 billion barrels/yr o 5 billion – 500 million = 4.5 billion barrels still have to be imported o Cuts imports by only 10% improvement, but does not make US free from foreign oil by any means “Drilling will keep gas prices low” o OPEC production drives gas prices OPEC: made of group of countries in middle east o Not all ANWR oil would be used by the US o Ex: In 2008, the US EXPORTED > 500 mbls “Tiny area drilled” o That ‘point’ on the map doesn’t include infrastructure Roads Pipelines Power lines Tankers Problems with anti-drilling side “Spills devastate the environment” o Exxon-Valdez clean-up cost > $2 billion o 20 years later oil was still on the beaches o Gulf spill est cost $40 billion This point is a legitimate concern, BUT a major spill may never occur “12 billion barrels = enough to only last ~ 2 yrs” o Assumes 12 billion barrels available o The US uses ~ 15 bbls in 2 years o 12 billion < 15 billion TRUE o BUT: this does not mean ANWR would be pumped dry within 2 years! Production Rate: 12 bbls/2 yrs = 6 bbls / yr o Impossible to pump the oil that quickly – Other Oil Sources Oil Shales (OS) & Tar Sands (TS) o Shales /sands have high organic content Problem: oil not fully formed o Can mine the rock/sed & ‘cook’ it Specific Advantages: o Extensive deposits o Estimated OS resource has 4x more oil than Saudi Arabia o Estimated TS resource is 2x the global oil resource Disadvantages o Produce more GGs than other fossil fuels 25-50% more CO pro2uced than normal oil o Not profitable at low oil prices High production cost o Cooking = use energy to make energy o Extensive mining operations 13 million tons of OS to fuel the US for 1 day o Uses lots of water > 2 billion gallons of water to pro 3. Coal – Not a hydrocarbon o Similar requirements for formation swamps and bogs (vegetation/plants) – Stages of Coal Formation o Peat (50% C) o Lignite (70% C) o Bituminous coal (70-90% C) o Anthractie coal (90+% C) – Advantages o US coal reserve big enough to last 100+ yrs at current rate of use (= 1 billion tons/yr – Disadvantages o Creates more pollution than other fossil fuels Produces 25% more CO than2oil Mercury, arsenic, etc produced during mining & burning Ash disposal: 130 million tons/yr in the US o Acid Rain Coal burning releases sulfur from pyrite (FeS )2SO +3H O 2 = H 20 4hich leads to acid rain **Effects of Acid Rain 1. Weathering damage 2. pH changes in aqueous habitats (ponds/lakes) 3. Leaches nutrients out of soil 3/12/16 Geol Lecture 15b Nonrenewable 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 U isotopes ( 235U vs. 23U) separated o Centrifuges: separate isotopes o U-235 produces the power Want the fuel enriched in 235U relative to 23U 238 235 o Filter out enough U ( U 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 neutrons takes time and energy 235 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 238 U 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 st • 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 • Currently being re-visited, especially in Europe 137 • 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