Transcript Chapter 29 - Mr. Tanaka`s Website

On the Grid
Soung Sik-Kim
Chapter 29
Summary
A chemical engineer Soung- Sik-Kim
• Describes optimizing the efficiency of coal-fired
power plants
• Discusses the benefits as an energy source:
plentiful, easy to store and transport, and many
power plants are already designed to burn it.
• Discusses downsides: air pollution and acid rain
• Describes how a power plant generates
electricity and distributed through the grid.
• Describes the grid as a large interconnected set
of circuits, and explains some of the basics
Electricity and Electronics
• Electricity is charge flowing in wires.
• Energy is required to make charge move.
• A power plant is designed to use the
chemical energy in fossil fuels to move
charges through wires.
Circuit
• A circuit is a closed continuous conducting
path along which charge can flow.
• A circuit has an energy source (a battery or
a power plant), a conductor (often a wire),
and a load (an electrical device that uses
the energy carried buy the charge to do
work.
Grid
• The electrical distribution grid
is a vast system connecting
millions of end users to electric
power.
• Power plants are connected to
the grid and supply the voltage
difference to move charge
through the grid.
• When more loads are
connected to the grid, electrical
generation at power plants
increases.
• Energy is not stored anywhere
in the grid.
Power
• Is a rate at which energy is produced or
consumed.
• The unit for power is the watt (W).
• One watt equals one joule/ second.
Engineers often describe power in terms of
kilowatts (1000x( or magawatts (1 million x).
Question 1
Question
• What is Soung referring to when she talks about “the grid,”
and how does “the grid” supply our electrical power?
Answer
• “The grid” is a massive system of interconnecting circuits that
provides electric power to end-users. There are ten grids in
North America. The electricity that power plants generate
enters the grid directly. Power companies provide grid access
to end-users and charge for energy consumed. Power
companies also make sure that power plants provide enough
electrical power to the grid to meet their end-users’ needs
Question 2
Question
• What caused the U.S. government to start funding clean coal
research like the kind that Soung does?
Answer
• In the 80’s, there was public outrage over acid rain, which was
created when sulfur dioxide and nitrogen oxide in the air
combined with rainwater, making the rainwater acidic. The
acid rain hurt plants and animals in entire ecosystems and
damaged buildings and statues made of marble and
limestone. In response to public concern, the US
Environmental Protection Agency (EPA) placed limits on the
amount of toxic gasses power plants may release. The
government started funding clean coal research in an effort to
help power plants meet those limits.
Question 3
Question
• Describe two ways that Soung is making coal-fired power plants
more efficient and cleaner for the environment.
Answer
• Installing sensors to monitor the temperature of gasses in the
combustion chamber makes it possible to adjust the flame size or
oxygen level so that as much energy as possible transferred to the
water in the boiler.
• Removing soot from the boiler tubes so as to remove unwanted
insulation in order to transfer as much heat as possible to the water
in the boiler.
• Reducing waste by using fly ash from coal burning as an ingredient in
concrete, and using molten ash, called slag, in roof shingles.
• Reducing atmospheric pollution by using a “scrubber” to remove
sulfur from the exhaust and combining it with limestone to make
Gypsum, which is used as a building material.
Question 4 and 5
Question 4
• What is necessary for charge to flow through a circuit?
Answer 4
• The circuit must be a continuous, closed conducting path.
Also, energy is required to make charge move, so there must
be a power source.
Question 5
• What is the relationship between energy and power? What
are the units for each?
Answer 5
• Power is the rate at which energy is consumed or produced.
The units used most frequently for energy are the joule, the
BTU, and the kilowatt-hour. The units used most often for
power are the watt (j/s), the kilowatt, and the megawatt.