EESA01 Lecture12-2011 -...

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Unformatted text preview: EESA01
Lecture
12
–
Final
 Lecture
 Energy
Alterna6ves
&
Wrap‐up
 (Guest
Lecture)
 December
1,
2011
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 1
 Photovoltaic
(Solar)
Energy
 •  Enough
energy
hits
earth
in
ONE
DAY
to
 power
human
electricity
consump6on
for
 25
YEARS;
trick
is
to
efficiently
harness
it
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 2
 Solar
Power
is
Growing
Fast
 •  Increased
use
by
28%
per
year
since
1971.
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 3
 Solar
Power
Benefits
 •  Sun
is
an
inexhaus6ble
resource
 •  Once
we
figure
out
to
harness
it
properly,
 there
is
more
than
enough
energy
that
 could
be
produced
to
fuel
the
world
 •  NO
CARBON
EMISSIONS
IN
USE 

 •  Quiet,
safe,
low‐maintenance
 •  Decentraliza6on
of
control
over
power
 •  “Net
metering”
 •  Job
produc6on
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 4
 Solar
Power
Drawbacks
 •  Spa6al,
daily,
and
seasonal
varia6ons
in
 solar
energy
 Figure 17.9 •  Very
large
upfront
capital
costs,
but
new
 technology
generally
pays
for
itself
in
10‐20
 years
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 5
 Wind
Energy
 •  Kine6c
wind
energy
turns
turbine
blades,
 which
produces
electrical
energy
 •  Wind
velocity
important:
cubic
rela6onship
 to
velocity

double
wind
velocity
=
8X
 more
power
 Figure 17.10 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 6
 Wind
Energy:
Land
vs
Water
 •  Wind
velocity
is
greater
(~20%
greater)
 over
water
compared
to
land
 •  Less
turbulent
as
well
(easier
maintained)
 •  Non‐trivial
transfer
of
energy
back
to
land
 Figure 17.12 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 7
 Wind
Energy:
Pros
and
Cons
 •  Advantages:

 –  No
emissions
other
than
manufacture
and
 installa6on
 –  EROI
close
to
25:1
 –  Can
be
small
or
large‐scale
 •  Disadvantages:
 –  –  –  –  Wind
is
intermilent
 Good
wind
speeds
not
always
near
ci6es
 NIMBY‐ism
 Bird
and
bat
hazard
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 8
 Geothermal
Energy
 •  Underground
water
(usually
very
deep)
 heated
by
magma;
water
and
steam
 produced
is
used
for
direct
hea6ng
and/or
 to
turn
turbines
for
electricity
produc6on
 Figure 17.15 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 9
 Ground
Source
Heat
Pumps
 •  •  •  •  Soil
at
more
constant
temperature
than
air
 Winter:
heat
carried
into
house;
condenser
and
heat
 exchanger
concentrate
energy
and
release
it
into
house
 Summer:
carrier
fluid
takes
heat
away
from
home
 See
“Science
Behind
the
Story”
page
544.
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 10
 Geothermal
Pros
and
Cons
 •  Advantages:

 –  Huge
reduc6on
in
fossil
fuel
emissions;
only
very
small
 emissions
from
dissolved
gases
in
groundwater
 •  Disadvantages:
 –  Direct
geothermal
only
viable
in
limited
places,
usually
 near
tectonic
plate
boundaries
 –  Sustainability
issues
related
to
groundwater
 withdrawal
 –  Tectonic
plates
slowly
move,
so
viability
is
not
 indefinite
 –  Hot
spring/water
usually
high
salt
content

can
 wreak
havoc
on
machineryand
lead
to
pollu6on
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 11
 Hydrogen
Fuel
Cells
 •  Hydrogen‐based
baleries
could
produce
 electricity
with
water
as
a
waste
product
 •  Obtaining
the
hydrogen
is
the
issue
 Figure 17.18 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 12
 Obtaining
Hydrogen
for
Fuel
 •  Hydrogen
gas
(H2)
is
extremely
reac6ve
and
 so
does
not
tend
to
exist
freely
 •  We
must
therefore
“extract”
it
from
other
 substances
 •  Electrolysis:
electricity
applied
to
water
 splits
it
into
O2
and
H2
 •  Needs
electricity
therefore
to
produce
 electricity?

 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 13
 Hydrogen
Fuel
Cells
Pros
and
Cons
 •  Advantages:

 –  Hydrogen
is
most
abundant
element
in
universe,
so
 we’ll
never
run
out
of
it
 –  Clean
and
non‐toxic
and
can
produce
fewer
GHGs
 –  Only
waste
product
is
generally
water
 –  Efficiency
comparable
to
fossil
fuels
 –  Never
need
recharging
as
long
as
fuel
is
available
 •  Disadvantages:
 –  Life‐cycle
GHG
release
highly
related
to
method
for
 obtaining
hydrogen
fuel
 –  Poten6ally
explosive
(but
not
really
more
than
gas)
 –  Possibility
for
contribu6ng
to
ozone
deple6on
 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 14
 Exam
Review
 •  Review
is
en6rely
driven
by
your
ques6ons
 •  A
previous
year’s
exam
is
posted
on
Blackboard,
 but
without
answers.

I’m
willing
to
answer
any
 ques6on
about
that
exam
now.

Otherwise,
you
 are
on
your
own.

 Lecture
12
–
Energy
Alterna6ves
and
Wrap‐Up
 15
 ...
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This note was uploaded on 02/29/2012 for the course ENVIRONMEN eesa01 taught by Professor Mitchel during the Fall '11 term at University of Toronto- Toronto.

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