Energy and the Environment
Energy and the Environment PHYS 3070
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This 15 page Class Notes was uploaded by Mrs. Peter Toy on Friday October 30, 2015. The Class Notes belongs to PHYS 3070 at University of Colorado at Boulder taught by Staff in Fall. Since its upload, it has received 51 views. For similar materials see /class/232116/phys-3070-university-of-colorado-at-boulder in Physics 2 at University of Colorado at Boulder.
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Date Created: 10/30/15
CT renewIIl What does quotrenewable energyquot mean again A The energy is not actually used B the energy comes from living things C The energy that is used is returned to the environment in a reusable form D the source of energy is not depleted by using it E the energy is quotgreenquot it does not damage or signi cantly alter the environment CT renewH2 Even sitting still human metabolism requires constant energy input What is the total energy expended by all human beings in a year 6 billion people we run at about 100 Watts each A lt1 QBtu B about 2 QBtu C about 20 QBtu D about 200 QBtu E gtgt 200 QBtu CT renewH3 You have been asked to study safety aspects of a hydroelectric power plant that uses the force of falling water incident on some turbines choose the plan that would result in the lowest kinetic energy of the incident water if iction is neglected h h 30 h 45lt E All would give the same kinetic energy What if there is friction CT renewII4 A good rainstorm could dump lEll kg of water from a cloud height of 1000 meters How much energy is dumped in this storm A IBM J B IBM J C 1E15 J D 1E18 J E I39m not sure how to compute this How long does a 350 MW electric plant like ours in Boulder have to operate to produce that much energy A one minute B one day C one month D one year E I39m not sure how to compute this CT renewHS Why would I say that you have to stop the Wind in order to get all its energy A Because you wouldn39t get any energy unless you bring its velocity to zero B Because its energy before is 12 mV Z and the Wind Will carry away some energy if V is not reduced to zero C If you didn39t stop the Wind the Windmill wouldn39t turn CT renewH6 What fraction of the energy content of the wind would I get if I only slowed it down to half its original speed A You39d get all of it B You39d get half of the available energy C You39d get 14 of the available energy D You wouldn39t get anything E None of theseyour hat would blow off CT renewII7 The relationship between wind power and wind velocity is written in your textbook as Pm26 lE394 V3 for average conditions If the wind speed doubles what happens to the power output of your windmill A Doubles B Increases by 4 C Increases by 8 D Increases by some other factor E Not sure II If we were to double the wind collecting area but wanted the same amount of power what would be required of the windspeed It could decrease by a factor of A 2 B 4 C 8 D Sqrt2 E None of these III A windmill produced 10 kW of power in a breeze of 5 ms How much power will it produce in a wind of 15 ms A 15 kW B 30 kW C 90 kW D 270 kW E I don39t know how to work this out CT renewH8 Why are Windmills so tall A Wind is stronger up there B Wind is steadier up there C They just have to be to capture a large area D So they don39t interfere With one another E So you can use the land below for something else like grazing CT renewH9 Of the nearly 5 pounds of daily waste the average person disposes of about What percent is a biomass derivative A 2 B 50 C 80 D I have no idea Is coal quotbiomassquot A No B No but it should be called that C Yes CTrenewll 10 What type of power plant emits the highest level or radioactive waste to the environment A hydroelectric plants B natural gas red plants C coal red plants D nuclear plants E All about comparable Let39s do an order of magnitude estimate Data Assume a big 1 GW output coal red plant Coal yields 8000 kWhr per ton front ylea Natural western coal is roughly 1 ppm part per million by weight Uranium How much Uranium is produced each year Modern quotcleanquot plants can recover 995 of the solid wastes How much Uranium is released into the atmosphere every year Natural Uranium is 075 U23 5 that39s the isotope you want for nuclear power plants or bombs How much of that is produced each year on I AOJ l nl CT renewH 11 How much does the ethanol creation process rely on fossils fuels A Not at all it39s a classic form of using solar energy to create quotbiofuelquot B Only a tiny negligible amount C At almost every step of the way Assuming that the amount of energy om fossil fuels consumed in the ethanol creation is a fair bit less than the amount made available in the ethanol is it a good candidate for a gasoline replacement Why or Why not CT renewH 12 Geothermal heat is primarily a result of A primordial solar energy trapped in the earth s center B the pressure of the earth s crust on the core C radioactive decay D gravitational pulls and pushes E all of these CT renewH 13 At this point What do you think the energy future of the US looks like A Much as it does today fossil fuels Will dominate for the foreseeable future B primarily nuclear C primarily solar D a diversity of renewables E a diversity of renewables plus nuclear CT renewH 14 An OTEC plant is built With the top near the surfasce of the sea at 20 C and the bottom 1000 m deeper Where the temperature is 5 C What is the maximum possibile ef ciency for converting the energy of the warm water near the top into usable energy A 75 B 25 C 95 D 5 E Something else Suppose the OTEC plant described above is a test device operating in the waters off Hawaii putting out 100 kWelectric In 1 second What is the amount of thermal energy dumped into the bottom of the ocean A 100000 J B 500000 J C 2 M D 5 k E Something else Some ideas for questions Some uses of ocean thermal energy are in principle exaggerated heat engines With this in mind What precautions would one take to ensure the greatest possible ef ciency Why would turbines on the ocean oor be preferable to Wind farms Is it more bene cial to incinerate out trash and recover the energy or reduce packaging increase recycling etc