Download Chapter 13 Achieving Energy Syustainability

Chapter 13
Achieving Energy Sustainability
What is renewable energy?
• Renewable energy can be rapidly regenerated, and
some can never be depleted, no matter how much of
them we use.
• Potentially renewable energy can be regenerated as
long as we do not consume them more quickly than
they can be replenished. An example is biomass: trees
and sugarcane.
• Nondepletable energy is solar, wind, geothermal,
hydroelectric, and tidal energy which cannot be
depleted within a human life span.
What is renewable energy?
•
Figure 13.1 shows both
renewable and
nonrenewable energy
resources. Fossil fuels and
nuclear fuels are
nonrenewable energy
resources. Renewable
energy resources include
potentially renewable
energy sources such as
biomass and
nondepletable energy
sources such as solar
radiation and wind.
What is renewable energy?
•
Figure 13.2 shows global energy use as of 2007. Renewable
energy resources provide about 13% of energy worldwide.
What is renewable energy?
•
Figure 13.3 shows energy use in the U.S in 2008. Only 7% of the
energy used in the U.S. comes from renewable energy resources.
How can we use less energy?
• Energy conservation- finding ways to use less
energy. For example, lowering your thermostat
during the winter or driving fewer miles.
• Energy efficiency- getting the same result from
using a smaller amount of energy.
• Some electric companies bill customers with a
tiered rate system: customers pay a low rate for the
first increment of electricity they use and pay
higher rates as their use goes up.
How can we use
less energy?
• Figure 13.4 shows
different ways
individuals can reduce
their energy use in and
outside the home. One
example is to purchase
Energy Star appliances
that use less electricity
(but do cost a little
more).
Benefits of Conservation and
Efficiency
• Many energy companies have an extra backup
source of energy available to meet the peak
demand, the greatest quantity of energy used
at any one time.
• Variable price structure- utility customers can
pay less to use energy when demand is lowest
and more during peak demand.
Sustainable Design
• Improving the efficiency
of the buildings we live
and work in.
• Building houses close to
where residents work
reduces reliance on fossil
fuels for transportation,
which in turn reduces the
amount of pollution and
carbon dioxide released
into the atmosphere.
Passive Solar Energy
• Thermal inertia is the
ability of a material to
retain heat or cold.
Materials with high thermal
inertia stay hot once they
have been heated or cooled.
• Figure 13.6 shows an
example of thermal
inertia being the “Heatabsorbing floor” made
of concrete, stone, brick
etc…
Sustainable Design
• Figure 13.7 shows the California Academy of Sciences. The
sustainable design of this San Francisco research institution
maximizes the use of natural light and ventilation. The building
generates much of its own electricity with solar panels on its roof
and captures water in its rooftop garden.
Biomass is energy from the Sun
• Figure 13.8 shows the sources of energy types. The sun
is the ultimate source of almost all types of energy.
Biomass is energy from the Sun
• Biomass energy resources encompass a large class of fuel
types that include wood and charcoal, animal products and
manure, plant remains, and municipal solid waste (MSW),
as well as liquid fuels such as ethanol and biodiesel.
• Wood, Charcoal and Manure- used to heat homes
throughout the world.
• Biofuels are when biomass are processed or refined into a
liquid fuels such as ethanol and biodiesel. (Chevy cars and
trucks are know to be flex-fuels cars because they can run on
gasoline or biofuels like E85.)
Modern Carbon vs. Fossil Carbon
• Many people are confused how burning biomass such as
wood is better than burning coal.
• The carbon found in biomass was in the atmosphere as
carbon dioxide, taken in by the tree, and by burning it we
put it back into the atmosphere.
• Burning coal is carbon that has been buried for millions of
years and was out of circulation until we began to use it.
This results in a rapid increase in the concentration of
carbon dioxide in the atmosphere.
Solid Biomass:
Wood, Charcoal, and Manure
• Figure 13.9 shows a picture of a charcoal market in the
Philippines. Many people in developing countries rely on
charcoal for cooking and heating.
• Charcoal is lighter than wood
and contains approximately
twice as much energy per unit
weight. A charcoal fire
produces much less smoke than
wood and does not need the
constant tending of a wood fire.
Biofuels: Ethanol and Biodiesel
• Ethanol is an alcohol, the same one found in alcoholic
beverages. It is made by converting starches and sugars
from plant material into alcohol and carbon dioxide.
• 90% of the ethanol produces in the U.S. are corn-based, some
other crops used are sugarcane, soybean and switchgrass.
• Flex-fuel vehicles can run on either gasoline or E-85.
• Biodiesel is a direct substitute for petroleum based diesel
fuel. Biodiesel is typically diluted to “B-20,” a mixture of
80% petroleum diesel and 20% biodiesel. B-20 is available at
some gas stations scattered around the United States and can
be used in any diesel engine.
The kinetic energy of water
can generate electricity
• Hydroelectricity-
electricity generated by the
kinetic energy of moving
water. This is the second
most common form of
renewable energy in the
world.
• Figure 13.12 shows a
water impoundment
hydroelectric dam.
Arrows indicate the path
of water flow.
Types of hydroelectric power
systems
• Run-of-the-river systems- water is held behind a dam
and runs through a channel before returning to the river.
• Water impoundment- water is stored behind a dam and
the gates of the dam are opened and closed controlling
the flow of water.
• Tidal systems- the movement of water is driven by the
gravitational pull of the Moon.
Advantages and Disadvantages of
hydroelectric power.
Advantages
Nondepletable resources
Low cost to run and operate
Disadvantages
Limited amount can be installed in
any given area
High construction costs
Helps reduce flooding down stream. Threats to river ecosystem (dams
block natural migration of fish)
Recreational use such as boating,
fishing, camping.
Loss of habitat, agricultural land and
cultural heritage, can displace large
numbers of people
Can cause silt to build up above the
dam
Passive Solar Heating
• Using passive solar energy can lower your electricity
bill without the need for pumps or other mechanical
devices. The sun can also be used to cook food.
•
Figure 13.16 shows
a passive solar
cooker. Residents of
this refugee camp in
Chad use solar
cookers to conserve
firewood and
reduce the need to
travel outside of
camp.
Active Solar Energy Technologies
•
•
Active solar energy- capturing
the energy of sunlight with the
use of a pump or photovoltaic
cell and generating electricity.
Figure 13.17 shows a solar
domestic hot water system. A
nonfreezing liquid (antifreeze) is
circulated by an electric pump
through a closed loop of pipes.
This circulating liquid moves
from a water storage tank to a
solar collector on the roof, where
it is heated, and sent back to the
tank. Then the heat exchanger
transfers the heat to water.
Active Solar Energy Technologies
•
Photovoltaic Systems
capture energy from the
Sun as light, not heat, and
convert it directly into
electricity.
• Figure 13.18 (a) shows a
domestic photovoltaic
system, photovoltaic solar
panels convert sunlight into
direct current (DC). An
inverter converts DC into
alternating current (AC),
which supplies electricity to
the house.
Active Solar Energy Technologies
•
•
Concentrating Solar
Thermal Electricity
Generation. Concentrating
solar thermal (CST) systems
are a large-scale application
of solar energy to electricity
generation.
Figure 13.19 shows how a CST
uses mirrors and reflectors to
concentrate the Sun’s energy
onto a “power tower,” which
uses the sunlight to heat water
and make steam for electricity
generation.
Advantages and Disadvantages of
solar power.
Advantages
Disadvantages
Nondepletable resources
Manufacturing materials requires
high input of metals and water
After initial investment, no cost to
harvest energy.
Geographically limited and the sun
doesn’t always shine
Can be used to offset many
applications in your home (heating
space, heating water, electricity,)
High initial costs are often
associated
No plan in place to recycle old solar
panels
Earth’s internal heat produces
geothermal energy
• Geothermal energy- using the heat from natural radioactive
decay of elements deep within Earth as well as heat coming
from Earth. Largest geothermal producers are U.S., China, and
Iceland.
• Iceland is on a divergent plate boundary which gives them
access to molten rock near the surface. Iceland has vast
amounts of geothermal resources and heats 87% of its homes
this way.
Earth’s internal
heat produces
geothermal
energy
•
Figure 13.20 shows a
ground source heat
pump. By exchanging
heat with the ground,
a ground source heat
pump can heat and
cool a building using
30 to 70 % less energy
than a traditional
furnaces and air
conditioners.
Advantages and Disadvantages
of geothermal system.
Advantages
Disadvantages
Nondepletable resources
Emits hazardous gases and
steam (depends on location)
After initial investment, no cost
to harvest energy.
Geographically limited
(Geothermal systems used to
make electricity such as
Iceland)
Can be installed anywhere
(ground source heat pumps)
High initial costs are often
associated
Wind energy is the
most rapidly
growing source of
electricity
• Wind energy- using a
wind turbine to convert
kinetic energy into
electrical energy.
• Figure 13.22 shows how
a wind turbine generates
electricity. The wind
turns the blade, which is
connected to the
generator, which
generates electricity.
Wind energy is the most rapidly
growing source of electricity
• Figure 13.24 shows global
growth of installed wind
energy capacity. Worldwide,
installed wind energy
capacity is now almost 160
gigawatts (GW).
• Some of the most rapidly
growing wind projects are
offshore wind parks, clusters
of wind turbines located in
the ocean within a few miles
of the coastline.
Advantages and Disadvantages
of wind system.
Advantages
Disadvantages
Nondepletable resources
Turbines can be very noisy,
wind doesn’t always blow.
After initial investment, no cost
to harvest energy.
Deaths of birds and bats in
migratory path
Wind has a low up-front start up Geographically limited to windy
cost
areas near transmission lines
Aesthetically displeasing to
some people
Storage batteries required for
off-grid systems.
Hydrogen fuel cells have many
potential applications
• Fuel cell- a device that operates like a common battery where
electricity is generated by a reaction between two chemicals.
• The reaction happens in a closed container to which no
additional materials can be added. Eventually the reactants
are used up, and the battery goes dead.
• Supplying hydrogen is a challenge because free hydrogen gas
is rare on Earth. Hydrogen tends to bond with other
molecules. Producing hydrogen gas requires separating it
from other molecules like water or natural gas.
• Electrolysis is when a electric current is applied to water to
“split” it into hydrogen and oxygen.
Hydrogen fuel
cells have many
potential
applications
•
Figure 13.25 shows how a
hydrogen fuel cell works.
Hydrogen gas enters the
cell from an external
source. Protons from the
hydrogen molecules pass
through a membrane,
while electrons flow
around it, producing an
electric current. Water is
the only waste product.
Advantages and Disadvantages of
hydrogen fuel cells.
Advantages
Disadvantages
Efficient
Producing hydrogen is an
energy-intensive process.
Zero air emissions besides
water vapor
Lack of distribution network
Hydrogen storage challenges
How can we plan our energy future?
• A sustainable energy strategy must combine energy
efficiency, energy conservation and the development of
renewable and nonrenewable energy resources, taking into
account the costs, benefits, and limitations of each one.
• In addition to investing in new energy sources, the U.S.
will have to upgrade its existing electrical infrastructure –
power plants, storage capacity, and distribution networks.
• Smart grid is an efficient, self regulating electricity
distribution network that accepts any source of electricity
and distributes it to end users.
How can we plan our energy future?
• Figure 13.26 shows
a smart house. A
smart grid
optimizes the use of
energy in the home
by continuously
coordinating energy
use with energy
availability.