Transcript Lecture4x

Tuesday night’s State of the Union Address: President Obama
At this moment, with a growing economy, shrinking deficits, bustling industry,
booming energy production, we have risen from recession freer to write our
own future than any other nation on Earth. It’s now up to us to choose who we
want to be over the next fifteen years, and for decades to come.
“We believed we could reduce our dependence on foreign oil and
protect our planet. And today, America is number one in oil and
gas. America is number one in wind power. Every three weeks, we
bring online as much solar power as we did in all of 2008.
And thanks to lower gas prices and higher fuel standards, the
typical family this year should save about $750 at the pump.”
US Wind Power:
2008: 8,366 MW
2009: 10,010 MW
2010: 5,216 MW
2011: 6,810 MW
2012: 13,131 MW
2013: 1,084 MW
2014 (Jan-Oct): 1,254 MW, with >13,600 MW under construction
“And thanks to lower gas prices and higher fuel standards, the
typical family this year should save about $750 at the pump.”
“Our manufacturers have added almost 800,000 new jobs. Some
of our bedrock sectors, like our auto industry, are booming. But
there are also millions of Americans who work in jobs that didn’t
even exist 10 or 20 years ago: jobs at companies like Google, and
eBay, and Tesla.”
“And no challenge, no challenge, poses a greater threat to future
generations than climate change.
2014 was the planet’s warmest year on record.
Now, one year doesn’t make a trend, but this does: 14 of the 15
warmest years on record have all fallen in the first 15 years of this
century.
I’ve heard some folks try to dodge the evidence by saying they’re
not scientists, that we don’t have enough information to act. Well,
I’m not a scientist either. But you know what? I know a lot of really
good scientists at NASA and at NOAA and at our major
universities, and the best scientists in the world are all telling us
that our activities are changing the climate, and if we don’t act
forcefully, we’ll continue to see rising oceans, longer, hotter heat
waves, dangerous droughts and floods, and massive disruptions
that can trigger greater migration and conflict and hunger around
the globe. The Pentagon says that climate change poses
immediate risks to our national security. We should act like it.”
“That’s why, over the past six years, we’ve done more than ever to
combat climate change, from the way we produce energy, to the
way we use it. That’s why we’ve set aside more public lands and
waters than any administration in history. And that’s why I will not
let this Congress endanger the health of our children by turning
back the clock on our efforts. I am determined to make sure
American leadership drives international action.
In Beijing, we made a historic announcement: the United States
will double the pace at which we cut carbon pollution, and China
committed, for the first time, to limiting their emissions. And
because the world’s two largest economies came together, other
nations are now stepping up, and offering hope that, this year, the
world will finally reach an agreement to protect the one planet
we’ve got.”
“That’s why, over the past six years, we’ve done more than ever to
combat climate change, from the way we produce energy, to the
way we use it. That’s why we’ve set aside more public lands and
waters than any administration in history. And that’s why I will not
let this Congress endanger the health of our children by turning
back the clock on our efforts. I am determined to make sure
American leadership drives international action.
In Beijing, we made a historic announcement: the United States
will double the pace at which we cut carbon pollution, and China
committed, for the first time, to limiting their emissions. And
because the world’s two largest economies came together, other
nations are now stepping up, and offering hope that, this year, the
world will finally reach an agreement to protect the one planet
we’ve got.”
“That’s why, over the past six years, we’ve done more than ever to
combat climate change, from the way we produce energy, to the
way we use it. That’s why we’ve set aside more public lands and
waters than any administration in history. And that’s why I will not
let this Congress endanger the health of our children by turning
back the clock on our efforts. I am determined to make sure
American leadership drives international action.
In Beijing, we made a historic announcement: the United States
will double the pace at which we cut carbon pollution, and China
committed, for the first time, to limiting their emissions. And
because the world’s two largest economies came together, other
nations are now stepping up, and offering hope that, this year, the
world will finally reach an agreement to protect the one planet
we’ve got.”
“That’s why, over the past six years, we’ve done more than ever to
combat climate change, from the way we produce energy, to the
way we use it. That’s why we’ve set aside more public lands and
waters than any administration in history. And that’s why I will not
let this Congress endanger the health of our children by turning
back the clock on our efforts. I am determined to make sure
American leadership drives international action.
In Beijing, we made a historic announcement: the United States
will double the pace at which we cut carbon pollution, and China
committed, for the first time, to limiting their emissions. And
because the world’s two largest economies came together, other
nations are now stepping up, and offering hope that, this year, the
world will finally reach an agreement to protect the one planet
we’ve got.”
Table 3-1, p. 82
Fig. 3-3, p. 80
Table 3-5a, p. 94
Fig. 3-4, p. 83
?
?
Table 3-5b, p. 94
10%
Table 3-5b, p. 94
10%
18%
Table 3-5b, p. 94
It takes a LOT of energy to get water to change its phase
(to get ice to melt, and to get liquid water to boil)!
Fig. 3-3, p. 80
It takes a LOT of energy to get water to change its phase
(to get ice to melt, and to get liquid water to boil)!
Heat of Fusion: It takes 335 kJ to turn 0°C ice into 0°C
water
Heat of Vaporization: It takes 2260 kJ to turn 100°C
water into 100°C steam
How much energy does it take to turn 1 kg of 0°C ice
into 100°C steam?
How much energy does it take to turn 1 kg of 0°C ice
into 100°C steam?
E = 335kJ + (4.19 kJ/°C)(100°C) + 2260 kJ
= 335 kJ + 419 kJ + 2260 kJ = 3014 kJ
HEAT flow by three mechanisms:
Conduction
Convection
Radiation
Fig. 4-7, p. 106
CONDUCTION:
k = thermal conductivity
CONDUCTION:
R = δ/k = “R value”
Qc = A x (T2 – T1)
t
R
Table 5-2a, p. 134
Table 5-2b, p. 134
Equivalent thicknesses needed to provide an R value of
R = 22 (ft2hr°F/Btu)
CONVECTION:
RADIATION (Electromagnetic):
RADIATION (Electromagnetic):
RADIATION (Electromagnetic):
Many energy-related machines
are examples of a “Heat Engine”
 Transforms Heat into Work
Ex/ Steam engines, combustion
engine, heat pump (refrigerator
or air conditioner)
Efficiency = Work out x 100%
Energy in
Efficiency = Work out x 100%
Energy in
= (Heat in – Heat out) x 100%
Heat in
Efficiency = Work out x 100%
Energy in
= (Heat in – Heat out) x 100%
Heat in
= (TH – TC) x 100%
TH
Efficiency = (TH – TC) x 100%
TH
The HOTTER an engine runs, the
more efficient it is.
Efficiency = (TH – TC) x 100%
TH
The HOTTER an engine runs, the
more efficient it is.
Ex/ If TH = 400K and TC = 300K
then Max possible efficiency =
(400K – 300K)/400K = 25%
Efficiency = (TH – TC) x 100%
TH
The HOTTER an engine runs, the
more efficient it is.
Ex/ If TH = 400K and TC = 300K
then Max possible efficiency =
(400K – 300K)/400K = 25%
Ex/ If TH = 1000K and TC = 300K
then Max possible efficiency =
(1000K – 300K)/1000K = 70%
Efficiency = (TH – TC) x 100%
TH
The HOTTER an engine runs, the
more efficient it is.
Ex/ If TH = 400K and TC = 300K
then Max possible efficiency =
(400K – 300K)/400K = 25%
Ex/ If TH = 1000K and TC = 300K
then Max possible efficiency =
(1000K – 300K)/1000K = 70%
It can never be 100%!
Second Law of Thermodynamics
1) Heat can flow spontaneously (by itself) only from a hot
source to a cold sink.
Second Law of Thermodynamics:
1) Heat can flow spontaneously (by itself) only from a hot
source to a cold sink.
2) No heat engine can be 100% efficient; some heat
always has to be discharged to a sink at a lower
temperature
Which of these will happen?
Second Law of Thermodynamics:
 In ANY system, the result of an interaction will be an
INCREASE in disorder (Entropy)
 Time has a direction! (toward disorder)
Which of these will happen?
How does an air conditioner work?
How does an air conditioner work?
What happens to a gas when you compress it?
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
HIGH PRESSURE
1. HOT
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
HIGH PRESSURE
2. Cools off
1. HOT
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
HIGH PRESSURE
2. Cools off
1. HOT
3. Ambient
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
2. Cools off
1. HOT
3. Ambient
4. COLD
LOW PRESSURE
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
2. Cools off
1. HOT
5. Warms up
3. Ambient
4. COLD
LOW PRESSURE
A heat pump (air conditioner, refrigerator) uses the trick
that gases become hot when compressed, cold when
expanded.
6. Ambient
2. Cools off
1. HOT
5. Warms up
3. Ambient
4. COLD
LOW PRESSURE
You can also do
this by changing
the phase – from
liquid to gas and
back again.
You can also do
this by changing
the phase – from
liquid to gas and
back again.
The gas GIVES OFF
heat when you
compress it into a
liquid and it
becomes hot
You can also do
this by changing
the phase – from
liquid to gas and
back again.
The gas GIVES OFF
heat when you
compress it into a
liquid and it
becomes hot
The gas
ABSORBS heat
when you let it
expand back
into a gas