Energy and the Environment Lecture 4 PHYS/ENVS 3070 Professor Dmitri Uzdensky Sept. 3, 2014 PHYS/ENVS 3070 1Announcements: • Read Chapter 1 of E&E textbook • CAPA Homework #1 due this Friday 11 PM • Pick up your paper copy of CAPA (with this week’s PIN) in Duane 2B hallway on Friday. • Office hours Tuesdays 11 AM – 12 noon (Gamow Tower F835) Sept. 3, 2014 PHYS/ENVS 3070 2Real%World%Limita.ons%on%Exponen.al%Growth%%%• In#real#natural#and#human#systems#exponen2al#growth#does#not#con2nue#indefinitely…##• Real#systems#are#subject#to#finite#resource#constraints#that#limit#unchecked#growth:##– resource#deple2on#for#non?renewable#sources##(e.g.,#fossil#fuels,#fossil#aquifers);##– finite#replenishment#rate#for#renewable#sources#(e.g.,#ocean#fisheries,#hydro?electric#power,#etc.);#– external#factors#(predators,#wars,#asteroids,#etc.).##Sept.#3,#2014# PHYS/ENVS#3070# 3#What is this graph telling us? How can we verify that it is reasonable? Limita.ons%on%Growth%Example%1:%Fossil%Fuel%Deple.on%Sept.#3,#2014# PHYS/ENVS#3070# 4#What are the axes? X-Axis = time in units of years Y-Axis = 1012 = 1 trillion or 1 Tera something (units?) Units = kW hr / yr = kilo-Watt hour / year = = some unit of energy/time (we will be learning about this!) Sept.#3,#2014# PHYS/ENVS#3070# 5#MESSAGE: • For hundreds of millions of years the supply of fossil fuels has been steadily building. • The plot asserts that all the fossil fuel reserves on Earth will be used up by people in a few hundred years! • What do we need to know to roughly check this calculation? Sept.#3,#2014# PHYS/ENVS#3070# 6#Coal Annual Energy Consumption (QBtu) Sept.#3,#2014# PHYS/ENVS#3070# 7#How much energy is used per time (today)? Global coal use is ~ 100 QBtu / year Global coal reserves ~ 1 trillion tons à 20,000 QBtu Thus the coal will provide us energy for how long? Timeper UseCoalSupply Coal Total coal up use toTime =years! 200QBtu/year 100QBtu 20,000 coal up use toTime ==Sept.#3,#2014# PHYS/ENVS#3070# 8#Key#Point#(as#a#focus#for#this#semester):##• Fossil#Fuels#are#finite.###• If#we#take#“es2mated#resources”#and#divide#by#the#“current#rate#of#consump2on”#we#find#that#gas#and#oil#will#last#several#decades#and#coal#for#a#few#hundred#years.#• If#you#factor#in#the#increasing#rate#of#consump2on,#this#2me#scale#goes#down#(poten2ally#by#a#large#factor).##Sept.#3,#2014# PHYS/ENVS#3070# 9#How%big%is%the%world%popula.on%today?%%#A)#7.2#milli o n#B)#315#million#C)#3.6#billion#D)#7.2#billion#E)#18#billion#Sept.#3,#2014# PHYS/ENVS#3070# 10#Room Frequency DC Clicker Question Limita.ons%on%Growth%Example%2:%%World%%Popula.on%Growth%What#happened#here?#Limita.ons%on%Growth%Example%2:%%World%%Popula.on%Growth%Sept.#3,#2014# PHYS/ENVS#3070# 11#Human Population Problem Currently population growth is ~ 1.2 % per year (80 million = population of Germany per year). If it follows an exponential and continues at this growth rate, the doubling time = 70 / 1.2 = 58 years. Thus, the world’s population would be ~ 14 billion in 2070. Sept.#3,#2014# PHYS/ENVS#3070# 12#If%this%growth%rate%c on.nued%for%950%years,%the%human%popula.on%would%grow%to%500%trillion.%How%big%is%500%trillion?%The%en.re%surface%area%of%the%earth%is%500%trillion%square%meters%(land%and%ocean).%%That%would%mean%one%person%per%square%m eter.%Feeling crowded ☺ Clearly, something would happen well before then…. Sept.#3,#2014# PHYS/ENVS#3070# 13#Actually, the rate of population growth has been slowing down. This is why projections of when the world’s population will double keep changing and depend on our assumptions. Sept.#3,#2014# PHYS/ENVS#3070# 14#Slowing%down%of%the%world%popula.on%growth%hap://www.census.gov/ipc/www/world.html#Sept.#3,#2014# PHYS/ENVS#3070# 15#Popula.on%growth%projec.on%Sept.#3,#2014# PHYS/ENVS#3070# 16#Popula.on%growth%projec.on%Sept.#3,#2014# PHYS/ENVS#3070# 17#exponen.al%rise!%UNITS%Sept.#3,#2014# PHYS/ENVS#3070# 18#Unit%Conversions%See#inside#jacket#cover#of#the#textbook!##Example:##What#is#10#cm#(cen2?meters)#in#inches?#cm 2.54 inch 1 =cm 2.54inch 1 1 =inches 3.9 cm 2.54inch 1 cm) (10 1 cm 10 cm 10 =⎟⎠⎞⎜⎝⎛×=×=or#No2ce#that#the#“cm”#cancel#out#above.#Sept.#3,#2014# PHYS/ENVS#3070# 19#105%seconds%sounds%like%a%big%number.%%As#an#Order#of#Magnitude#es2mate,#how#many#days#is#this?#(do#not#use#a#calculator!)##A)#0.01#days#B)#1.0#days#C)#10.0#days#D)#100.0#days#E)#None#of#the#above# hours 24day 1min. 60hour 1sec. 60min. 1 sec. 10 Time5⎟⎠⎞⎜⎝⎛×⎟⎠⎞⎜⎝⎛×⎟⎠⎞⎜⎝⎛×= (OOM)day 1hours 10day 1min. 100hour 1sec. 100min. 1 sec. 10 Time5≈⎟⎠⎞⎜⎝⎛×⎟⎠⎞⎜⎝⎛×⎟⎠⎞⎜⎝⎛×≈Sept.#3,#2014# PHYS/ENVS#3070# 20#Room Frequency DC Clicker QuestionStandard#Interna2onal#(SI)#Units##hap://www.physics.nist.gov/cuu/Units/current.html###SI#unit#of#energy#=#Joule,####SI#unit#of#power#(energy/2me)#=#Waa#Sept.#3,#2014# PHYS/ENVS#3070# 21#800#Horsepower#Automobile#5,150#BTU#Room#Air#Condi2oner##*#BTU#or#Btu#=#Bri2sh#Thermal#Unit#Sept.#3,#2014# PHYS/ENVS#3070# 22#What#is#the#energy#output#(in#units#of#“Joules”)#from##burning#1#pound#(lb)#of#coal?#Table#2.6#says#that#the#best#coal#(Anthracite)#which#is#88%#carbon,#has#an#energy#content#of#13,300#Btu#/#lb.####We#will#discuss#different#units#of#energy!#For#now#note#that#Btu#and#Joules#are#both#units#of#energy.##Book#inside#jacket#says#1#Joule#=#9.49#x#10?4#Btu.#Btu 300,13(coal) lb 1Btu 13,300 (coal) lb 1 Energy =×=Joules 104.1Btu 10 9.49Joule 1Btu 300,13 Energy 74-×=××=Sept.#3,#2014# PHYS/ENVS#3070# 23#Order%of%magnitude%es.mates%(OOM)%Olen#we#want#a#quick#answer#that#gives#us#the#an#approximate#scale#of#the#problem.##In#this#case,#we#are#not#interested#in#being#accurate#within#a#factor#of#2#or#3,#but#only#being#accurate#within#a#factor#of#ten#(some2mes#called#an#order#of#magnitude#=#factor#of#ten).#How#many#jelly#beans#are#in#this#jar?##à#Volume#of#Jar#à#Size#of#a#single#jelly#bean#à#Packing#frac2on#!#Sept.#3,#2014# PHYS/ENVS#3070#
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