Page 316 - (DK) The Ultimate Visual Dictionary 2nd Ed.

PHYSICS AND CHEMISTR Y

Energy SANKEY DIAGRAM SHOWING ENERGY
FLOW IN A COAL-FIRED COMBINED
HEAT AND POWER STATION
ANYTHING THAT HAPPENS—from a pin-drop to an Heat energy produced by
burning each kilogram
explosion—requires energy. Energy is the capacity for
of coal (25 million J) Useful electrical
“doing work” (making something happen). Various forms of energy (7 million J)
energy exist, including light, heat, sound, electrical, chemical,
nuclear, kinetic, and potential energies. The Law of
Conservation of Energy states that the total amount of energy in
the universe is fixed—energy cannot be created or destroyed.
It means that energy can only change from one form to another
(energy transfer). For example, potential energy is energy that is
“stored,” and can be used in the future. An object gains Waste heat Heat used in local
potential energy when it is lifted; as the object is released, (5 million J) schools and housing
(13 million J)
potential energy changes into the energy of motion (kinetic
energy). During transference, some of the energy converts into
CROSS-SECTION OF HYDROELECTRIC POWER
heat. A combined heat and power station can put some of the STATION WITH FRANCIS TURBINE
otherwise “waste” heat to useful effect in local schools and Transformer Insulator High voltage
housing. Most of the Earth’s energy is provided by the Sun, in cable
the form of electromagnetic radiation (see pp. 316-317). Some Switch gear Bushing
including Rotor house
of this energy transfers to plant and animal life, and ultimately circuit braker
Generator
to fossil fuels, where it is stored in chemical form. Our bodies unit
Gate
obtain energy from the food we eat, while energy needed for
Generator rotor
other tasks, such as heating and transport, can be obtained by turned by turbine
burning fossil fuels—or by harnessing natural forces like wind
Shaft
or moving water—to generate electricity. Another source is Francis turbine
nuclear power, where energy is released by reactions in the
Curved blade
nucleus of an atom. All energy is measured by the international
unit, the joule (J). As a guide, one joule is about equal to the
Gate
amount of energy needed to lift an apple one meter.
Screen Afterbay
Water in
CROSS-SECTION OF NUCLEAR POWER STATION WITH reservoir
PRESSURIZED WATER REACTOR Potential energy Penstock Tailrace
of water intake Draft
Steam generator turns turbine tube Water that flows
out has lost some
Concrete Water in heat energy
shielding exchanger turns Turbine shaft
to steam turns generator
Water Transformer
pressurizer Steam drives Generator produces increases voltage
turbine electric current at to 300,000 volts
Steel girder 25,000 volts
framework
High voltage
Control rod cable
Reactor core
Tower carries
Pump high voltage
electricity
Moderator
(water) Hot water to
Heat Pump cooling tower
Enriched Coolant (water) exchanger Water cools used steam
uranium fuel takes heat from Cold water
reactor core to Water pumped back into Steam loses energy to turbine from cooling
heat exchanger steam generator and condenses back to water tower

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