RENEWABLE ENERGY
SOURCES
Our power, our future
Residential Solar Power
Using the sun to heat your home
Photovoltaics
In PV cells, sun’s energy powers a
chemical reaction -> electricity
Commercial residential PV modules
anywhere from 10 to 300 watts
Can be used en masse to create power
plants
Direct current generated must be
inverted into alternating current energy
Pollution Reduction
Over 20 years, a 100-megawatt plant
avoids 3 million tons of carbon dioxide.
1000 kWh of solar power saves:
8 pounds of sulfur dioxide
5 pounds of nitrogen oxide
1,400 pounds of carbon dioxide
Expensive!
5-kW systems can cost up to $40,000!
Power costs up to $9/watt!
Over 30 states offer incentives
California is the leader in encouraging
solar power use
Biomass Fuels
Solid Fuel Combustion
Combustion of biomass instead of coal
tends to be cleaner and helps eliminate
waste efficiently
Products burned are usually wood
matter, vegetation, waste from lumber
yards, etc (cellulosic)
Digestion
Occurs naturally - bacteria feed
on decomposing waste
Releases gases like methane,
hydrogen, CO, etc
Pipelines running thru waste
collect gases (landfills, feedlots,
zoos)
Synthesis gases can become
any kind of hydrocarbon fuel.
Pyrolysis
Intense heat (above 800° F) and
pressure makes a product like
charcoal, doubling the energy density
Highly transportable and efficient
Ethanol
A.k.a. alcohol; chemical formula
CH3CH2OH.
Produced using the dry mill method.
81 plants in 20 states can produce 4.4
billion gallons each year
Any cellulosic biomass can be
converted into ethanol.
Ethanol in Cars
Mixed with gasoline to form either E10
or E85
Number is percentage of ethanol in
mixture
Increases octane rating and decreases
emissions
Ethanol is favored oxygenate under Clean
Air Acts Amendments of 1990
Many incentives encourage its use
Wind Energy
Fastest Growing Source of
Renewable Energy
History and Definition
First use as early as
5000 B.C.
First used to
generate electricity
in Denmark as early
as 1890.
Now, windgenerated electricity
is very close in cost
to the power from
conventional utility
generation in some
locations.
•Wind is a form of solar
energy.
•Caused by uneven
heating of atmosphere
by the Sun, irregularities
of the Earth’s surface,
and rotation of the Earth.
•The amount and speed
of wind depends on the
Earth’s terrain and other
factors.
Horizontal-Axis Wind Turbine
Vertical-Axis Wind Turbine
Advantages and Disadvantages
Wind is free, wind
farms need no fuel.
Produces no waste
or greenhouse
gases.
The land beneath
can usually still be
used for farming.
Wind farms can be
tourist attractions.
A good method of
supplying energy to
remote areas.
•Not always predictable.
•Price of land.
•Changing landscape.
•Can kill birds migrating flocks tend to
like strong winds.
•Can affect television
reception if you live
nearby.
•Noisy. A wind generator
makes a constant, low,
"swooshing" noise day
and night.
Hydroelectric Power
America’s leading renewable
energy source
History and Basics
The earliest reference
from 4th century BC
Greek literature.
“hydro” comes from
the Greek word for
“water.”
By 1980, accounted
for 25% of global
electricity and 5% of
total world energy
use, totalling 2,044
billion kilowatt hours
(kW h).
•Water flows from a
high potential energy
(high ground) to lower
potential energy (lower
ground), the potential
energy difference is
partially converted into
electric energy through
the use of a generator.
•There are two major
designs in use that
utilize water to produce
electricity
Hydroelectric Dam
Advantages:
The energy is virtually
free.
No waste or pollution
Reliable
Can cope with peaks
in demand.
Can increase to full
power very quickly,
unlike other power
stations.
Electricity can be
generated constantly.
•Disadvantages:
–Expensive to build.
–Environmental
concerns upstream
and downstream
–Siting
Pumped-Storage Plant
Advantages:
Without some means of storing energy for quick
release, we'd be in trouble.
Little effect on the landscape.
No pollution or waste.
Disadvantages
Expensive to build.
Once it's used, you can't use it again until you've
pumped the water back up.
Good planning can get around this problem.
Important Concept:
These plants are not really power stations, but a
means of storing energy from other power
stations.
Ocean Energies
Waves, tides, ocean currents,
ocean thermal energy
General Information
70% of Earth’s surface is covered by oceans
Huge potential: “a mere .1% of total energy
potential in oceans would satisfy all of mankind’s
energy needs five times over.”
United States faces siting challenges and
economic obstacles
Europe: leader in ocean energies
Exploiting Location and natural geography
Winds blown across Atlantic (West -> East)
create bigger waves -> more energy potential
Areas for underwater currents and tides
Wave Power vs. Ocean Currents
Waves push high-pressure
oil through hydraulic
motors to generate
electricity; fed to grid via
underwater cable
Wave farms: 30 MW / sq.
km; enough to power
20,000 homes
All systems manipulate
wave motions to power
hydraulic pumps or spin
turbines
European power costs
roughly 9 cents/kWh
•Britain’s example
•Turbines anchored to
ocean floor, currents spin
blades, generate electricity.
•More efficient than wind:
8 mph ocean current vs.
230 mph wind
•10 cents/kWh estimate
•Verdant Power company
plans to build 5-10 MW field
in East River in New York
Tidal Power
Damming estuaries, water flows through turbines
One method: ebb generation
High and low tides are very predictable
Can only produce electricity at certain times
Not many places in the world where it’s efficient
5-10 meter difference between high and low tides
High costs to build deters private investors
Negative impact on estuarine ecosystems
Ocean Thermal Energy
Conversion (OTEC)
Hawaii can exploit this technology because of its
location near the equator
Sun heats water to depths of 100 meters to
temperatures around 24-30 degrees Celsius
Flashing into steam
Cold water from deeper in ocean condenses the steam,
produces desalinated water!
OTEC can serve much of Hawaii’s energy needs, but
not really any of the contiguous United States
Geothermal
Exploiting Earth’s temperatures to
produce electricity and heat our homes.
Direct Heating vs Generating Electricity
Immediate, usable energy
Can heat buildings or
entire areas
Relatively warm air in
winter
Warm water piped
under streets in
Klamath Falls, OR
melts snow
Same principle of relative
temperatures allows for
cooling of buildings in
summer
•Different types of plants
depending on
geothermal area
–Hot water/steam
–Not-so-hot water
•Using steam directly to
spin turbine
•“Flashing” steam to spin
turbine
Advantages
Reliability – the Earth’s heat provides a constant
source of energy
Low impact on environment
Room for improvement: 2,300 MW in 2004, D.O.E.
estimates could be 15,000 MW by 2014
Hot Dry Rock
How does it work?
If the technology works, we could tap geothermal energy
ANYWHERE!
Disadvantages
Depletion of water
Re-injecting water
Earthquakes…should plants be responsible?
Heat depletion
Natural cooling of Earth’s crust cannot be avoided
Plants become less and less efficient
Economics
Building costs: $1175-1750 per kW installed capacity
Geothermal areas aren’t always near electricity grids…
Projections for Geothermal
National Commission on Energy Policy
estimates 4-6 cents per kWh
Compares favorably with other renewables
(solar: 20-25 cents per kWh)
Compares favorably with coal and NG: 4-5
cents per kWh
Estimates depend on availability of
geothermal resources and success of HDR
technology
Encouraging Development
Through Government
Policies
Energy Policy Act of 2005, Tradable
Permits, State Renewable Portfolio
Standards (RPS)
National Level
Congress passed Energy Policy Act of 2005
To expand renewables so they become economically
competitive energy sources
Increase US consumption of renewable energy
At least 3% from 2007-09
Developing existing renewable sources
Hydroelectric: $10,000,000 budget for incentives to plants
Up to $750,000 to any particular plant
Goal: increase efficiency by at least 3%
Biomass: synergy between forest-clearing and biomass facilities;
expand markets for products of forest clearing
National Commission on Energy Policy
Tradable permits system
State Level
State Renewable Portfolio Standards
(RPS)
AZ, CA, CO, CT, IA, ME, MD, MA, NJ, NM,
NY, NV, PA, RI, TX, WI
States with ample renewable resources
Hawaii, Illinois, Minnesota shifting towards
adopting them
Most have adopted them in the past five
years, more will catch on as conventional
energy sources run out.
The Future…
Energy Policy Act means we will see more
renewables in the next ten years; efficiency will
increase
Tradable-permits system, if passed, will provide
huge economic boost to renewables
consumption of renewables will increase by up to
60%
depends on solving problems of initial allocation of
permits, and other countries’ cooperation
Action at the state level will increase as the
nation seeks to find alternatives to fossil fuels
More renewables legislation will undoubtedly be
put into effect as we run out of energy