ESCI 380 Post-Midterm- Final
Question and answers already passed
2025/2026
Two ways to price the emissions externality - correct answer ✔1. Tax it! • Government decides what
they think the price should be • Monitor emissions from all sources • Require emitters to pay for each
unit of emission 1 ton co2, pay $40 2. Cap it! • Set a maximum (annual) amount of emissions • Issue
permits for each unit of emissions (give them away for free, or auction them) • Let emitters trade those
permits - those who can reduce emissions inexpensively will sell permits to those who cannot • A.k.a.
ETS (emissions trading scheme)
What is a wedge? - correct answer ✔A wedge" is a strategy to reduce carbon emissions that grows in
50 years from zero to 1.0 GtC/yr. The strategy has already been commercialized at scale somewhere.
• Observations tell us that the climate is - correct answer ✔changing
• Models tell us that when _______ factors are included our observations fit with models - correct
answer ✔anthropogenic
• Climate change is due to a power (or energy) _______ - by trapping more heat the temperature has to
go up until that balance is achieve and energy in=energy out - correct answer ✔imbalance
• The solution will require _______ cooperation—and it will cost money - correct answer
✔international
what basic form of energy we're extracting from the air with a wind turbine? - correct answer
✔Answer: kinetic energy (½mV^2) If we have a mass that has velocity there is KE associated with that
mass
, For a constant wind speed v, normal cross sectional area A, and given period of time, t, and air density ρ,
Air mass m = ρAVt So, KE = ½ ρAtV^3, Wind power density (per unit area and per second) is: Power/Area
= ½ ρ V^3---Harvestable power scales with the cube of the wind speed -in a single second- how much air
will have passed through some swept area- - correct answer ✔that's the velocity-swept area of 20 m^2
and V of 10 m/s-> Volume of cylinder would be 200 m^3 Then- multiply that volume * density== mass-
plug mass into 1/2 mv^2 equation
wind speed distribution with Rayleigh - correct answer ✔(v^3)ave= 1.91v(sub ave)^3 -avg wind speed,
if it follows this distribution-- then the power in the average power in the wind is just 1.91 multiplier in
Power that a windmill can generate per unit land area =• Power per windmill / land area per windmill -
correct answer ✔= (Cp x 1/2 pv^3 x (pi/4)d^2)/ (5d)^2
challenges with wind & solar- - correct answer ✔they produce power intermittently
Power in the wind- equations come from the kinetic energy equation - correct answer ✔KE=1/2mv^2=
Joules= kg(m/s)^2=kgm^2/s^2= Joule •Power= (1/2mv^2)/t= Watts=1/2mass/second x v^2= 1/2 x v x
r^2 x density x v^2 =1/2(r^2)(v^3)
Power in the wind Ex. v= 6 m/s, rotor= 30 m=1.225kgm^3, •What is the power "in the wind" - correct
answer ✔P=1/2(pi)(30^2)(1.225)(6^3) P=3.7 *10^5W
Why might we not be able to extract all this power from that turbine- - correct answer ✔you're not
going to get all that air flowing in, or interacting with the rotor
Betz limit- - correct answer ✔how much power we could possibly extract from the wind
Pwind=1/2(pi)r^2(v^3) •Pelec=1/2(pi)r^2(v^3), eff< 59%, •if wind speed is 3 m/s and 9 m/s - correct
answer ✔Psub3 m/s= 1/2(pi)(30)^2(1.225)(3)^3= 4.7 x 10^4W •Psub9 m/s=1/2(pi)(30)^2(1.225)(9)^3=
1.26 x 10^6W •Pavg=1/2(pi)(r^2)(v^3)x(1.91)x eff
Question and answers already passed
2025/2026
Two ways to price the emissions externality - correct answer ✔1. Tax it! • Government decides what
they think the price should be • Monitor emissions from all sources • Require emitters to pay for each
unit of emission 1 ton co2, pay $40 2. Cap it! • Set a maximum (annual) amount of emissions • Issue
permits for each unit of emissions (give them away for free, or auction them) • Let emitters trade those
permits - those who can reduce emissions inexpensively will sell permits to those who cannot • A.k.a.
ETS (emissions trading scheme)
What is a wedge? - correct answer ✔A wedge" is a strategy to reduce carbon emissions that grows in
50 years from zero to 1.0 GtC/yr. The strategy has already been commercialized at scale somewhere.
• Observations tell us that the climate is - correct answer ✔changing
• Models tell us that when _______ factors are included our observations fit with models - correct
answer ✔anthropogenic
• Climate change is due to a power (or energy) _______ - by trapping more heat the temperature has to
go up until that balance is achieve and energy in=energy out - correct answer ✔imbalance
• The solution will require _______ cooperation—and it will cost money - correct answer
✔international
what basic form of energy we're extracting from the air with a wind turbine? - correct answer
✔Answer: kinetic energy (½mV^2) If we have a mass that has velocity there is KE associated with that
mass
, For a constant wind speed v, normal cross sectional area A, and given period of time, t, and air density ρ,
Air mass m = ρAVt So, KE = ½ ρAtV^3, Wind power density (per unit area and per second) is: Power/Area
= ½ ρ V^3---Harvestable power scales with the cube of the wind speed -in a single second- how much air
will have passed through some swept area- - correct answer ✔that's the velocity-swept area of 20 m^2
and V of 10 m/s-> Volume of cylinder would be 200 m^3 Then- multiply that volume * density== mass-
plug mass into 1/2 mv^2 equation
wind speed distribution with Rayleigh - correct answer ✔(v^3)ave= 1.91v(sub ave)^3 -avg wind speed,
if it follows this distribution-- then the power in the average power in the wind is just 1.91 multiplier in
Power that a windmill can generate per unit land area =• Power per windmill / land area per windmill -
correct answer ✔= (Cp x 1/2 pv^3 x (pi/4)d^2)/ (5d)^2
challenges with wind & solar- - correct answer ✔they produce power intermittently
Power in the wind- equations come from the kinetic energy equation - correct answer ✔KE=1/2mv^2=
Joules= kg(m/s)^2=kgm^2/s^2= Joule •Power= (1/2mv^2)/t= Watts=1/2mass/second x v^2= 1/2 x v x
r^2 x density x v^2 =1/2(r^2)(v^3)
Power in the wind Ex. v= 6 m/s, rotor= 30 m=1.225kgm^3, •What is the power "in the wind" - correct
answer ✔P=1/2(pi)(30^2)(1.225)(6^3) P=3.7 *10^5W
Why might we not be able to extract all this power from that turbine- - correct answer ✔you're not
going to get all that air flowing in, or interacting with the rotor
Betz limit- - correct answer ✔how much power we could possibly extract from the wind
Pwind=1/2(pi)r^2(v^3) •Pelec=1/2(pi)r^2(v^3), eff< 59%, •if wind speed is 3 m/s and 9 m/s - correct
answer ✔Psub3 m/s= 1/2(pi)(30)^2(1.225)(3)^3= 4.7 x 10^4W •Psub9 m/s=1/2(pi)(30)^2(1.225)(9)^3=
1.26 x 10^6W •Pavg=1/2(pi)(r^2)(v^3)x(1.91)x eff
