1Reminders:• Research Project #1 due on Friday- Make sure to review paper requirements- See me if you have questions- Must be handed in (not emailed)• Next homework will be assigned on Wednesday, and due the next Wednesday.• Reminder of Extra Credit #5 – Forum this Thursday.Energy Balance? Carbon Neutral?Does farming produce more energy than it uses?– Fertilizers, water transport, farm machinery• Estimate in the text based on solar energy conversion is not the main issueCan we grow enough plant material to make adifference?– Switchgrass, other non-food crops– Change to more vegetarian dietShould we divert agricultural products from food to fuel?NIMBY ?= “Not In My Back Yard”People do not like incinerators.High costs for separation. Currently about 15% of waste is burned.Few Other Renewables Discussed in Chapter 5…• Ocean Thermal Energy Conversion (OTEC)• Geothermal Energy•Tidal EnergySome of these seem like obvious big energy sources, but there are very significant practical issues.These and others are very interesting, but not major players right now. Read some details in Chapter 5.Ocean Thermal Energy Conversion• Heat engine driven by thermal gradient between surface and deeper ocean layers– Very small Carnot efficiency• Turbine driven by ocean currents– Potentially serious environmental impacts• Very large capital costs2Geothermal Energy PotentialWarm core of earth (radioactive in origin).Heat flow out from core < (1/1000) of flow in from sun.Most places the flow rate is too low to make use of, but “hot spots” (geysers, volcanoes) might be tapped.Places like Iceland have this working quite well (1/3 of their energy).World wide all operating and planned facilities Æ 1% of current global electrical production.Hydrothermal systemsHot dry rock (igneous systems)Normal geothermal heat (200 C at 10 km depth)Many sources are not renewable (e.g. “Geysers” in California).Over time one uses up the local heat source!1.3 GW capacity in 1985Summary on RenewablesKey message: there is no “easy fix”.Even maximizing and combining all of wind, solar, OTEC, biomass, geothermal, tidal, etc., we are still not able to match our current (and increasing) energy demands.We need to provide incentives to develop these alternatives and they can be expanded by factors of 10-100 !However, a key part has to be reducing demand. Remember that our demand is doing the opposite (it is increasing). Watch out for numbers that quote the demand per person since the number of people is also increasing.Nuclear EnergyClicker QuestionWhat is the first thing you associate with the word “nuclear”?A) The solution to our energy problemsB) The Atomic BombC) Magnetic Resonance Imaging (MRI)D) Three Mile IslandE) DeathF) Words that are difficult to pronounceIs that pronounced "nu-clear" or "nuke-ular"?MRI is really nuclear magnetic resonance imaging, but for some reason people were more apprehensive about a “nuclear test”.3HiroshimaNuclear fission chain reactions are the current power source for nuclear reactors. Isotopes of Uranium for example are the fuel.Nuclear weapons now utilize both fission and fusion reactions.The sun is powered by fusion reactions in the core. The sun will continue to “burn” for 10 billion years before it runs out of fuel.Did you grow up frightened about nuclear war?A) Yes, it was a fairly constant threat on my mindB) Yes, but I only thought of it very occasionally.C) I was vaguely aware of the threat, but never took it very seriouslyD) No, I have always completely ignored the threatE) I wasn't really aware there was any such threat.How about the fear of a serious (Chernobyl scale or worse) nuclear accident in the US?I grew up in the 1980's with President Reagan (e.g. the evil empire…), and so my answer is somewhere between A and B Clicker QuestionHave you ever been exposed to ionizing radiation from nuclear processes?A) Not as far as I'm awareB) Only medical X-raysC) Yes, once in a while from multiple sourcesD) Yes, a number of times from multiple sourcesE) I'm exposed all the time, continuously.Answer is E - we're exposed all the time continuously. Typical annual dose something like 3-400 milliREM/year.Radiation from the sun, from rock (granite), medical x-rays, all kinds of sources.We will need to define what milliREM is !Clicker QuestionUnited States of America104 reactors with 99,000 MegaWatts20% of electricityIn 1990, the Public Service Company of Colorado initiated steps to decommission the Fort St. Vrain high temperature gas cooled reactor and to convert the site to a peaking plant, fired by natural gas.4USA has 104 reactors with 99,000 MegaWattsFrance alone has 59 reactors with 63,000 MegaWatts, 77% of their electricity generation !World has 443 reactors, 367,000 MegaWatts capacity.USA electricity from nuclear ~ 20%France electricity from nuclear ~ 77%Germany and Japan electricity from nuclear ~ 25%South Korea electricity from nuclear ~ 40%The fraction of US electricity coming from nuclear plants over the past 10 years has been:A) steadily increasingB) stayed about the sameC) steadily decreasingD) not sure/otherAnswer C: Steadily decreasing, because the number of plants has stayed fixed, but our electricity from other sources continues to rise. Very similar to hydroelectric story….Clicker Question Clicker QuestionHow many people were killed in the Three Mile Island nuclear accident in 1979.A) 0B) 10C) 100D) 1,000E) 10,000Note that no new nuclear power plants have been orders in the United States since then.Start with the BasicsNuclear power is still a significant source of US electricity (100 GigaWatts or 20% of our electric grid).No new plants since 1970’s and so the percentage is dropping in the US (similar to hydroelectric).Much larger player in other parts of the world (especially France) and growing in Asia (India, S. Korea, China, Taiwan, Japan,…).Daya Bay,
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