Renewable and Alternative Energy Sources
World Wide Energy Production
15.2%
alternative
84.8%
fossil
fuels
U.S. Energy Consumption
The four primary consumers of energy in the
U.S. in 2007 were
Industrial
32%
Transportation
28%
Residential
22%
Commercial
18%
93% of the energy generated and used in the
U.S. are from nonrenewable resources
Alternative Energy Sources
World-wide, with the
exception of coal, which
has known reserves that
will last a couple of
centuries, the known
reserves of oil are
expected to be exhausted
in your lifetime...
Clearly, alternative energy
sources are needed for
the future
Alternative Energy Sources
We will look at:
Solar energy
Geothermal power
Hydropower
Tidal Power
Ocean thermal energy conversion
Wind energy
Biomass
Solar Energy
The Sun is free (nobody owns or controls it)
In principle, the amount of solar energy that
reaches the Earth’s surface could provide for
all human energy needs forever
Solar Energy
The distribution of solar energy over the
continental U.S. in watts per square meter
The desert regions of the southwest U.S.
receive the most sunlight
Clean Solar Energy
Solar energy is clean energy
It produces no hazardous solid, liquid or gas
wastes
It does not create water or air pollution
Solar Energy
The two areas in which solar energy can make
the greatest contribution are in space heating
and in the generation of electricity
These are uses that account for two-thirds of
U.S. energy consumption
Solar Heating
The simplest approach
to solar heating is
passive-solar heating
The building design
should allow the
maximum amount of
sunlight to stream in
through south and
west windows during
the cooler months
This heats the house
and materials inside
Solar Heating
Trees can be positioned
to shade the house in
summer
Wide eaves can shade
windows in summer, but
allow winter sunlight to
enter
Drapes and shutters
can insulate window
areas in winter
Solar Heating
It has been estimated that 40 to 90% of most
homes’ heating requirements could be
supplied by passive-solar heating systems
100% solar homes have been built, but such
homes usually cost many tens of thousands
of dollars more to build
Retrofitting older homes
to be solar efficient can be
too costly
Over insulation can
aggravate indoor pollution
Solar Electricity
Direct production of electricity using sunlight
is accomplished using photovoltaic cells, also
called solar cells
They have no moving parts and are “clean”
energy
They are used to
power the space
station and to
provide electricity in
remote areas on
Earth
Solar Electricity
A major limitation is cost, which greatly
exceeds the cost of producing electricity using
fossil fuels or nuclear power
The best solar cells are only 20% efficient and
only provide 50 watts of electricity per square
meter of cell size
Solar Electricity
A 100 watt light bulb would require 2 square meters
of solar cells
And a 100-megawatt power plant would require 2
square kilometers (0.78 square miles) of solar cells
This represents a
major use of land
and resource,
which would use
far more steel
and concrete
than a fossil fuel
power plant
Storing Solar Electricity
In a solar energy home,
extra electricity is stored
in batteries for later use
This work well for one
house
Unfortunately, no wholly
practical technology has
been developed to store
large amounts of
electricity, despite
advances in batteries
Storing Solar Energy
Some possible schemes for storing the energy
of solar generated electricity include breaking
up water into oxygen and hydrogen to burn
later as fuels
Also pumping water to an elevated reservoir for
later use as hydroelectric power generation
Solar Energy
Currently, solar energy
provide less that 0.5% of
the U.S. power needs,
but even with existing
technology, it could
provide up to 15%
Solar Electricity
In summation, to make
solar energy truly useful
for large-scale power
generation:
We need more efficient
solar cells
We need a means of
better storing electricity
TRADE-OFFS
Passive or Active Solar Heating
Advantages
Energy is free
Net energy is
moderate (active) to
high (passive)
Quick installation
No CO2 emissions
Very low air and water
pollution
Very low land
disturbance (built
into roof or windows)
Moderate cost
(passive)
Disadvantages
Need access to sun
60% of time
Sun can be blocked
by trees and other
structures
Environmental costs
not included in market
price
Need heat storage
system
High cost (active)
Active system needs
maintenance and repair
Active collectors
unattractive
Fig. 16-11, p. 412
Geothermal Power
Geothermal Power
Magma rising from the mantles brings unusually hot
material near the surface
Heat from the magma, in turn, heats any groundwater
This is the basis for generating geothermal energy
Geothermal Power
The steam and/or hot water is used
to create electricity or for heating
Geothermal Power Plants
Worldwide, there are now about 40 geothermal
power plants, especially in Japan, Mexico and
the Philippines
Note that
most
geothermal
power
plants are
built along
plate
tectonic
boundaries
Geothermal Power Plants
How the geothermal energy is used depends
on the temperature of the water
Three types of power plants are used to
generate power from geothermal energy:
Dry steam
Flash
Binary
Types of Geothermal Power
Dry steam plants take steam out of the ground
and uses the steam to turn a turbine that spins
a generator
This was first done in Italy in 1904
Iceland, a volcanic
island, has many
geothermal areas
that produce steam
and are tapped to
generate electricity
Types of Geothermal Power
Flash plants take super heated water, usually
at temperatures over 200°C, out of the
ground, allowing it to boil as it rises to the
surface, then separates the steam from the
water and uses the steam to turn a turbine
generator
A flash power
plant in Japan
Types of Geothermal Power
In binary plants, the hot water flows through
heat exchangers, boiling an organic fluid that
spins the turbine
For all three types of power plants, the
condensed steam and remaining geothermal
fluid are injected back into the hot rock to
pick up more heat
This is why geothermal energy is viewed as
sustainable
It is also very “clean”
Only produces steam
The Geysers, California
The largest U.S. geothermal power plant is
The Geysers in California (it uses dry steam)
By 1989, a total of 10 billion watts of
electricity was being produced by The
Geysers and six other plants in the U.S.
Geothermal Power Plants
By the end of 2005 worldwide use of
geothermal energy for electricity had reached
9.3 billion watts, with an additional 28 billion
watts used directly for heating
In 1999, it was
estimated that
the U.S. could
produce 100
billion watts of
geothermal
energy by 2050
Geothermal Heat
Even if the geothermal water is not as hot as
steam, the warm water can be used to heat
buildings, home and even greenhouses
This is routinely done in Russia and Iceland
In fact, using
geothermal energy
to heat is about 2-3
times as common
as using it to
create electricity
Limitations
Each geothermal field can only be used for a
period of time, a few decades, before heat
extraction is seriously reduced
Simply put, you can take hot water out of the
ground faster than it can be renewed (even if
you pump the water back into the ground)
For example, steam pressure at The Geysers
has declined rapidly over recent years
It peaked at over 2 billion watts by 1991, but
now in 2011 produces about 0.7 billion watts
TRADE-OFFS
Geothermal Energy
Advantages
Disadvantages
Very high efficiency
Scarcity of suitable sites
Moderate net energy
at accessible sites
Lower CO2 emissions
than fossil fuels
Can be depleted if used
too rapidly
Environmental costs
not included in market
price
CO2 emissions
Low cost at
favorable sites
Moderate to high local
air pollution
Low land use and
disturbance
Noise and odor (H2S)
Moderate
environmental
impact
High cost except at the
most concentrated and
accessible sources
Fig. 16-29, p. 428
Hydropower
One-third (33%) of all power plants in the U.S.
are hydroelectric, but they only generate 6%
of U.S. electricity needs
Hydropower
A cross-section of a typical hydroelectric dam
Water flows down the penstock, turns the
turbine blades which power the generators
Hydropower
Water use for generating hydroelectric power is
totally dependent on the available water (duh!!)
The Glen Canyon Dam in Utah is the classic
example of building too big of dam for not
enough water
Hydropower
Hydropower is a very clean, pollution-free,
renewable energy source
The water is not consumed, but rather simply
passes thru the generating equipment, and
since several dams may occur along the
same river, the water can be reused and
reused
Hydropower
If every stream and river in America was dammed
to generate power, you still only provide 20% of
current U.S. power needs
There are about 1000 dams in the U.S. and there is
very little prospect of building any new ones
In fact, some older dams have been removed,
such as the 162 years old Edwards Dam in Maine
Three Gorges Dam
The Three Gorges Dam is now the largest
hydroelectric dam in the world
Three Gorges Dam
As a size comparison, it is 5 times larger than
the Hoover Dam on the Colorado River
Three Gorges Dam
The dam is 185 meters
(600 feet) high and 2.3
kilometers (1.4 miles)
wide
It has 26 hydroelectric
power generators with
a collective generating
capacity of about
18,000 megawatts (the
average nuclear power
plant generates about
1000 megawatts)
Three Gorges Dam
The Chinese began filling the reservoir in 2003
When filled to capacity, the reservoir will hold
22 cubic kilometers of water
Three Gorges Dam
As with any engineering
project of great
magnitude, there are
serious problems
The reservoir will
eventually stretch over
600 kilometers (375
miles) in length
It will submerge 125,000
acres of prime farmland
Three Gorges Dam
1,900,000 people
were forced to
relocate, many
against their will
Entire cities have
been abandoned
Over 1200
historic areas are
being flooded
Three Gorges Dam
Three spectacular river gorges called Qutang,
Wuxia and Xiling, all worthy of being national
parks, have been flooded
Three Gorges Dam
Officials report that the cost is within its US$25
billion budget and insisted early on that the
project would pay for itself through electricity
generation
However, the project is
thought to have cost
more than any other
single construction
project in modern
China, with unofficial
estimates of US$100
billion or more
TRADE-OFFS
Large-Scale Hydropower
Disadvantages
Advantages
Moderate to high net
energy
High efficiency (80%)
Large untapped
potential
Low-cost electricity
Long life span
No CO2 emissions
during operation in
temperate areas
Can provide flood
control below dam
Provides irrigation
water
Reservoir useful for
fishing and recreation
High construction
costs
High environmental
impact from flooding
land to form a reservoir
Environmental costs
not included in market
price
High CO2 emissions
from rapid biomass
decay in shallow
tropical reservoirs
Danger of collapse
Uproots people
Decreases fish
harvest below dam
Decreases flow of
natural fertilizer (silt)
to land below dam
Fig. 16-21, p. 418
Tidal Power
All large bodies of water, including the oceans
and large lakes, have tides
Tidal power captures the energy contained in
moving water mass due to tides
Tidal Power
Two types of tidal energy can be extracted:
Kinetic energy of currents between ebbing and
surging tides
Potential energy from the difference in height (or
head) between high and low tides
Tidal Power
You can use the
flowing water
between low and
high tides to
generate electricity,
similar to
hydropower
Tidal Power
Turbines can be place on the ocean floor, for
example at the entrance of a bay, where the
flowing water can turn the fan to generate
electricity
Tidal Power
Another option is to use under water turbines,
which is like an underwater wind farm
This is currently being tested offshore of
Scotland’s Orkney Islands
The ebbing and surging tidal flows turn 100 foot
propellers, which each produce 1 megawatts of
electricity
OTEC
Ocean energy thermal conversion (OTEC) is a
new, clean technology that is still in the
developmental stage
It exploits the temperature difference between
warm surface water and the cold water at
depth to run a “heat engine”
A heat engine is a device placed between a
high temperature reservoir and a low
temperature reservoir that produces energy
OTEC
Either the warm water is used directly to run a
turbine, or the heat is used to vaporize a
working fluid (ammonia) which runs the turbine
The cold water
is used to chill
down the water
or vapor
Drinkable,
distilled fresh
water is a byproduct
OTEC
The temperature difference must be at least
40oF (22oC) year round, which is only found
near the equator
So this emerging technology is best for tropic
islands
OTEC
A test plant is currently being constructed at
Keahole Pointe on the Kona coast of Hawaii
and should become operational in 2013
Wind Energy
Wind energy has been utilized for thousands
of years
Wind Energy
The wind is free, commonly available and
can provide clean, pollution-free energy
Today’s wind-turbines are very high tech
Wind Energy
In most places, the cost of
commercial wind power on
a large scale is not now
economically competitive
with conventionally
generated electricity
One important factor is that
with a doubling of wind
speed, power output
increases by a factor of 8
Wind Energy
The numbers indicate the percentage of
1990 regional electricity demand that full
utilization of wind energy could meet
Clearly, the great plains have significant
wind energy potential
Wind Energy
U.S. wind power capacity from 1981 to 2002
Wind Energy
U.S. wind power capacity from 1996 to 2008
Wind Energy
The U.S. remains the world leader in wind
energy, but Europe has embarked on an
very ambitious wind-power development
program
It is predicted
that by 2030,
wind energy
will supply at
least twice the
electricity it
does now
Wind Energy Limitations
It would take about 1000 one-million watt
windmills to equal the energy output of one
sizable fossil fuel power plant
The windmills can
be noisy
And they are hard
on migrating birds
TRADE-OFFS
Wind Power
Advantages
Moderate to high
net energy yield
High efficiency
Moderate capital
cost
Low electricity cost
(and falling)
Very low
environmental
impact
No CO2 emissions
Quick construction
Easily expanded
Disadvantages
Steady winds needed
Backup systems
needed when winds
are low
Plastic components
produced from oil
Environmental costs
not included in market
price
High land use for
wind farm
Visual pollution
Can be located at sea
Noise when located
near populated areas
Land below turbines
can be used to grow
crops or graze
livestock
Can kill birds and
interfere with flights of
migratory birds
Fig. 16-23, p. 421
Biomass Energy
Biomass energy is
derived from organic
matter
Stoves that burn wood
are the classic example
In fact, there had been
a 20-25% increase in
the use of wood stoves
over the past several
decades
Biomass Fuels or Biofuels
Biofuels differ from other renewable energy sources,
such as wind, hydroelectric, geothermal and solar,
as they are primarily used in the transportation
sector and are derived from recently living matter,
both plant and animal
Ethanol Fuel
Ethanol fuel is a biofuel alternative to gasoline,
which is gaining popularity world-wide
Car engines can be designed to run on 10%,
50% even 100% pure ethanol
It is cleaner burning
than gasoline
Worldwide, the use
of ethanol is rapidly
increasing
“E” Numbers
Ethanol fuel mixtures have "E" numbers which
describe the percentage of ethanol in the mixture
by volume, for example, E85 is 85% ethanol and
15% gasoline
Low ethanol blends, from
E5 to E25, are also known
as gasohol, though
internationally the most
common use of the term
gasohol refers to the E10
blend
Gasohol
E10 gasohol is becoming more commonly found at
gas stations in the U.S. (Tennessee is way behind)
As the “10” indicates it is made from a mixture of
gasoline (90%) and ethanol (10%)
Gasohol has higher octane,
or antiknock, properties
than gasoline and burns
more slowly, more cooler,
and more completely,
resulting in reduced
emissions of some
pollutants
Ethanol Fuel
Automotive ethanol capabilities vary widely
country to country, but most spark-ignited
gasoline style engines will operate well with
mixtures of up to 10% ethanol
Brazil is the world leader in ethanol fuels
In Brazil, ethanol-powered
and flexible-fuel vehicles
are manufactured to be
capable of operation by
burning hydrated ethanol,
an azeotrope of 93%
ethanol and 7% water
Ethanol Fuel
Ethanol fuel is
produced from sugar
cane in Brazil, which
is a more efficient
source of fermentable
carbohydrates than
corn as well as much
easier to grow and
process in the
tropical climate
UT & Switchgrass
The UT Biofuels Initiative has started testing the
use of switchgrass, which is believed to offer a
greater ethanol yield than corn in a temperate
climate, such as in Tennessee
UT & Switchgrass
The project represents the culmination of years
of corporate research and development and a
highly touted $40.7 million investment from the
state of Tennessee to build a plant for
demonstrating technology developed by
DuPont Danisco Cellulosic Ethanol
TRADE-OFFS
Biodiesel
Advantages
Reduced CO
emissions
Reduced CO2
emissions (78%)
High net energy
yield for oil palm
crops
Moderate net
energy yield for
rapeseed crops
Reduced
hydrocarbon
emissions
Better gas
mileage (40%)
Potentially
renewable
Disadvantages
Increased NOx
emissions and
more smog
Higher cost than
regular diesel
Environmental costs
not included in market
price
Low net energy yield
for soybean crops
May compete with
growing food on
cropland and raise
food prices
Loss and degradation
of biodiversity from
crop plantations
Can make engines
hard to start in cold
weather
Fig. 16-25, p. 424
TRADE-OFFS
Ethanol Fuel
Advantages
Disadvantages
High octane
Lower driving range
Some reduction in
CO2 emissions
(sugarcane bagasse)
High net energy
yield (bagasse and
switchgrass)
Reduced CO
emissions
Can be sold as E85
or pure ethanol
Low net energy yield
(corn)
Higher CO2 emissions
(corn)
Much higher cost
Environmental costs
not included in market
price
May compete with
growing food and raise
food prices
Higher NOx emissions
and more smog
Corrosive
Potentially renewable
Can make engines hard
to start in cold weather
Fig. 16-27, p. 426
Alternative Energy Sources
Most of the world still
relies very heavily on
fossil fuels, but slowly
but surely, attention is
being diverted to
alternative energy
Energy use in the
future will not be
dominated by a single
source
Alternative Energy Sources
The most important
aspects of most
alternative energy
sources is that they
promise clean,
pollution-free energy