Topic 8.1 - Energy Sources

8/20/2019 Topic 8.1 - Energy Sources

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Essential idea: The constant need for new energysources implies decisions that may have a serious

effect on the environment. The finite quantity of

fossil fuels and their implication in global warming

has led to the development of alternative sources ofenergy. This continues to be an area of rapidly

changing technological innovation.

Topic 8: Energy production

8.1 – Energy sources


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Nature of science: Risks and problemsolving! "inceearly times mankind understood the vital role of

harnessing energy and largescale production of

electricity has impacted all levels of society.

#rocesses where energy is transformed requireholistic approaches that involve many areas of

knowledge. Research and development of

alternative energy sources has lacked support in

some countries for economic and political reasons.

"cientists$ however$ have continued to collaborate

and share new technologies that can reduce our

dependence on nonrenewable energy sources.




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Understandings:% "pecific energy and energy density of fuel sources

% "ankey diagrams

% #rimary energy sources

% Electricity as a secondary and versatile form of energy

% Renewable and nonrenewable energy sources




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Applications and skills:% "olving specific energy and energy density problems

% "ketching and interpreting "ankey diagrams

% &escribing the basic features of fossil fuel power

stations$ nuclear power stations$ wind generators$pumped storage hydroelectric systems and solar

power cells

% "olving problems relevant to energy transformations in

the conte't of these generating systems% &iscussing safety issues and risks associated with the

production of nuclear power

% &escribing the differences between photovoltaic cells

and solar heating panels




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Guidance:% "pecific energy has units of ( kg1) energy density has

units of ( m*

% The description of the basic features of nuclear power

stations must include the use of control rods$moderators and heat e'changers

% &erivation of the wind generator equation is not

required but an awareness of relevant assumptions

and limitations is required% "tudents are e'pected to be aware of new and

developing technologies which may become

important during the life of this guide




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Data booklet reference:% #ower + energy / time

% #ower + ,1-/ A ρ v *

Utilization:

% 0enerators for electrical production and engines for

motion have revolutionied the world ,see Physics

subtopics 5.4 and 11.2 /

% The engineering behind alternative energy sources is

influenced by different areas of physics ,seePhysics subtopics 3.2 $ 5.4 and B.2 /

% Energy density ,see Chemistry subtopic C.1/

% 2arbon recycling ,see Biology subtopic 4.3/




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Aims:% Aim 4: the production of power involves many

different scientific disciplines and requires the

evaluation and synthesis of scientific information

% Aim 8: the production of energy has wide economic$environmental$ moral and ethical dimensions




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E345#6E! 4 woodburning stove or afurnace convert the chemical energy in

wood or natural gas to heat$ through

burning. The heat is used directly.

E345#6E! 4 windmill or waterwheel can

directly convert the kinetic energy of the

wind or water into mechanical motion of

wheels to grind wheat grain into flour.

Primary energy sources • 4 primary energy source is an energy source$ such

as coal$ wind$ oil$ gas$ or water$ which is used directly

by the consumer.




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Primary energy sources•7ou should have a good idea of these percentages$

from memory.



ossil

fuels29


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#R42T:2E!Primary energy sources



•"un makes biomass through photosynthesis.

•;iomass gathers and grows over time.

•;iomass buried under great pressure and heat.

•;iomass becomes coal$ oil and natural gas over eons.

•2oal$ oil and natural gas are e'tracted.

•2oal$ oil and natural gas are used as fuels.


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Primary energy sources



#R42T:2E! #roved reseres

are resources that we are sure

we can obtain. !roduction

means actual reserves thathave been obtained and

placed on the market.


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E345#6E! Electricity is by far the most common of the

secondary energy sources because of its convenience

in both use and transport.

E345#6E! Dydrogen is a

growing secondary energy

source$ and is being

developed because its

consumption produces only water as a byproduct.

Secondary energy sources • 4 secondary energy source is an energy

source$ such as electricity or hydrogen$

which has been transformed from a primary

energy source before use by the consumer.




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E345#6E! ission of each uranium* produces

*.×1>11 ( of energy. The density of B kg

m*. 2alculate the E "# and the E & of 11 ( / *.@>×1> kg + @.>×1>1* ( kg1.

,b/ E& + ,@.>×1>1* ( kg1/,1.8×1>B kg m*/

+ 1.A×1>18 ( m*.

Seci!ic energy and energy density o! !uel sources •"pecific energy E "# is how much energy ,(/ you can

get per unit mass ,kg/ from a fuel. :ts units are ( kg1.

•Energy density E & is how much energy ,(/ you can

get per unit volume ,m*/. :ts units are ( m*.




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Seci!ic energy and energy density o! !uel sources•5ost of our energy comes from fuels. Dere is the

energy yield of various fuels!



uel uel Type "pecific energy ,5( / kg/

#rotons =uclear *>>$>>>$>>>$>>>$>>>

#etrol ossil BA.@

&iesel ossil B.8

;iodiesel ossil B.

2rude 9il ossil B1.@

2oal ossil *.

"ugar ossil 1?.>

Food ossil 1?.>

2ow &ung ossil 1.Dousehold Faste ossil 1>.>


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"ene#a$le and non%rene#a$le energy sources •#ene$able resources can be replaced in a

reasonable amount of time ,or are not depleted/.




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"ene#a$le and non%rene#a$le energy sources•Renewable energy is better than nonrenewable

because it will not run out.

•9il and gas are better than coal because they burn

more efficiently and produce less 29.•2oal is cheaper and more plentiful than gas and oil.

•=uclear power does not produce 29.

•Dydroelectric systems are useful to have in a grid

because they can be used to store e'tra energy.

•;urning biomass alleviates landfills.

•=uclear waste lasts for thousands of years.

•Find turbines and photovoltaic cells depend on the

weather conditions and have small output.




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E345#6E! 2oal has a specific

energy of *. 5( / kg. :f a city has

a coalfired power plant that needs

to produce *>.> 5F of power$ withan efficiency of G$ how many

kilograms of coal are needed dailyH

"96. + *>.> 5F / inut → inut + 1> 5F

;ut 1 day + B×*A>> s + 8AB>> s so that

inut + ,1> 5(s1/,8AB>> s/ + 1>*A8>>> 5(.

inut + ,1>*A8>>> 5(/,1 kg - *. 5(/ + *>>>> kg.

Solving seci!ic energy and energy density ro$lems



e!!iciency + outut / inut efficiency


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#R42T:2E!

:f coal is transported in rail cars

having a capacity of 1. metric

tons$ how many cars per daymust supply the power plant of

the previous e'ampleH

"96


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#R42T:2E!

:f a nuclear power plant powered

by uranium* has the same

output and the same efficiencyas the coalfired plant of the

previous e'ample$ how many

kilograms of nuclear fuel will it burn per dayH #er

yearH

"96


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#R42T:2E!

E'plain why it is advantageous to

have a submarine which is nuclear

powered$ as opposed to diesel."96


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San&ey diagrams•2ontinuous conversion of energy into work requires a

cyclical process and the transfer of energy from the

system.

•:f youKve ever camped out youKve probablyused a campfire in these two obvious ways!

for cooking$ and for warmth.

•:n both cases!

,1/ :t is the heat released during combustion,a chemical reaction/ that is used.

,/ The heat is used directly.

,*/ "ome %eat is lost to the

environment or wasted.




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San&ey diagrams•2ontinuous conversion of energy into work requires a

cyclical process and the transfer of energy from the

system.

•:f you want to convert the heat to useful work$some sort of engine must be designed.

•or e'ample$ the potential energy of a hot air

balloon can be changed with heatL

• 4nd to make an electricityproducing engineL•9nce the water is used up$ the balloon must

cool do$n$ descend$ and refill its water supply.

•Then it can repeat the motion in a cyclical

process that will keep producing electricity.




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#R42T:2E!

:n the balloonwater electricity engine name

all of the energy conversions that occur.

"96


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#R42T:2E!

:n the balloonwater electricity engine name

all of the energy losses that occur.

"96


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San&ey diagrams

•The second la$ of t%ermodynamics states that

although it is possible to convert mechanical energy

completely into thermal energy$ it is =9T possible to

convert all heat energy into mechanical energy.•The balloon e'ample demonstrates the second part of

the law! 5uch energy is lost or wasted.

• 4nd the e'ample of kicking the block shown ne't

demonstrates the first part!

• 4ll of the blockJs kinetic energy became friction heat.

•9bviously$ this heat cannot ever be used to give the

block back its original kinetic energyI

•This loss of energy during conversion from one

form to another is called energy degradation.




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San&ey diagrams•Energy degradation in systems can be shown

with an energy flow diagram called a "ankey

diagram.

•or the hotair balloon e'ample we have thefollowing "ankey diagram!

•The degraded energy is represented by the yellow

bent arrows$ and shows energy lost by the system.



CHEMICAL

ENERGY

POTENTIAL

ENERGY

KINETIC

ENERGY

ELECTRICAL

ENERGY


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San&ey diagrams

•"ankey diagrams show the efficiency of each energy

conversion.

•"uppose the actual energy values are as shown!

•The efficiency of a conversion is given by

•or e'ample$ the efficiency of the first energy

conversion ,chemical to potential/ is

e!!iciency + 8> 5( - 1>> 5( + >.8> or 8>G.



CHEMICAL

ENERGY

POTENTIAL

ENERGY

KINETIC

ENERGY

ELECTRICAL

ENERGY

100 MJ 80 MJ

70 MJ 50 MJ

e!!iciency + outut / inut efficiency


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FYI

Fhat is the overall efficiency of this engineH

E345#6E!

ind the energy values for each of the degradations in

the "ankey diagram.

"96


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E345#6E!

•Efficiencies for various MmachinesN are shown in the

table.

San&ey diagrams



5achine Efficiency ,G/

"team 6ocomotive to 1>

Duman 5uscle > to

4utomobile less than

2ompressor 8>

Electric 5otor ?> to @


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E345#6E! To give you an idea of why living things are

so inefficient$ consider the caterpillar that eats leaves.

•=ote how the total leaf energy is

used!Fhat is the caterpillarJs overall

efficiencyH

"96> (

+ 1?G

San&ey diagrams




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E345#6E! :n the bigger picture$ energy is degraded in

an ecosystem.

San&ey diagrams



=ote that in eachstage @>G of the

stored energy is

lost to the

environmentI


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Energy diagram for the


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Charles (inard)s 1*+, San&ey diagram sho#ing the num$er o!men in -aoleons 1*12 "ussian camaign army their

movements as #ell as the temerature they encountered on

the return ath. 0ithograh +2 3 cm.

181 9verture on 7ouTube

http://www.youtube.com/watch?v=n82l3rEQSWkhttp://www.youtube.com/watch?v=n82l3rEQSWk


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Electricity as a secondary and versatile !orm o! energy •Electricity is one of the most useable forms of

,secondary/ energy we have because it is

so easily transportable and distributed.

•7ou may recall that movingelectrons produce a

magnetic field.

•:t turns out that the

process is symmetric! 4 moving magnetic field

produces moving electrons

,an electromotive force/.

•Essentially$ an electromotive force ,emf/ is a voltage

that can drive an electrical current.



&

O

ammeter


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Fire

Electrons

Electricity as a secondary and versatile !orm o! energy •The wire coils in a generator e'perience

reversing magnetic fields as they rotate

through action of a turbine of some sort$

usually driven by a primary energysource.

•This changing field produces the emf.

•This emf drives the charges and creates a current.

•=ote how the direction of the current keeps alternating. This is why your current at home is alternating current

,42/. ;ield


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escri$ing !ossil !uel o#er stations•The most common way to generate electrical power is

the coalburning power plant.

•2hemical energy in coal is released by burning.

•Deat boils water.•"team rotates

a turbine.

•The turbine turns

a coil of wire in amagnetic field.

•Electrical power

is produced.



;oiler

Turbine0enerator

2ondenser 2oal


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escri$ing !ossil !uel o#er stations Coal/oil%$urning



COAL

BOILER

STEAM

TURBINE

CONENSER

GENERATOR

!"#$ %ater %a&te$ 'eat

e('a)&t *a&

+r,!t,"-

CHEMICAL

ENERGY

HOT

STEAM

KINETIC ELECTRICITY

e('a)&t

*a&

%a&te$

'eat

+r,!t,"-

.0/

e++,!,e-


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escri$ing !ossil !uel o#er stations as%$urning



G A S

BOILER

STEAM

TURBINE

CONENSER

GENERATOR

!"#$ %ater %a&te$ 'eat

e('a)&t *a&

+r,!t,"-

CHEMICAL

ENERGYELECTRICITY

e('a)&t %a&te$'eat

+r,!t,"-

GENERATOR

GAS

TURBINE

HOT STEAM KINETIC ELECTRICITY

+r,!t,"-

50/

e++,!,e-

+r,!t,"-


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escri$ing nuclear o#er stations•=uclear power stations are the same as fossil fuel

stations$ from the turbine on down.



⇒ Deat ⇒ Pinetic ⇒ Electrical


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E345#6E! 2reate a "ankey diagram for a typical

nuclear reactor! ;ecause of the difficulty of enrichment$

include that energy in the diagram.

"96


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#R42T:2E!

Fhat transformations were not shown in the previous

"ankey diagramH

"96


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FYI

;ecause of the energy

e'penditure of the enrichment

process$ it is often included in

the "ankey diagram.

escri$ing nuclear o#er stations•To work properly$ a reactor needs a higher proportion

of the


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escri$ing nuclear o#er stations




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escri$ing nuclear o#er stations •Nuclear fission is the splitting of a large nucleus into

two smaller ,daughter/ nuclei.

• 4n e'ample of fission is

•:n the animation$ *< is hit by a

neutron$ and capturing it$

becomes e'cited and unstable!

•:t quickly splits into two smallerdaughter nuclei$ and two neutrons$

each of which can split another

nucleus of *


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escri$ing nuclear o#er stations •=ote that the splitting was triggered by a single neutron

that had Cust the right energy to e'cite the nucleus.

•=ote also that during the split$ two more neutrons werereleased.

•:f each of these neutrons splits subsequent nuclei$ we

have what is called a c%ain reaction.

*< O 1n → ,*A3e O @B"r O ,1n/ @ > @ B *8 >



#rimary"econdary

Tertiary

1

B

8

Eonential ro#th


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escri$ing nuclear o#er stations •Fe call the minimum mass of a fissionable material

which will sustain the fission process by itself the

critical mass.

• =ote that*8

< isnot even in this list.

• This is why we

must enrich

naturallyoccurring

uranium for

reactor usage.




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escri$ing nuclear o#er stations •:n a nuclear reactor$ a controlled nuclear reaction is

desired so that we merely sustain the reaction without

growing it.

•:n a nuclear bomb$ an uncontrolled nuclear reaction isdesired so that we have an immense and very rapid

energy release.

controlled

uncontrolled



6al! o! the roduct neutrons are

a$sor$ed $y the control rods

7e# o! the roduct

neutrons are a$sor$ed


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escri$ing nuclear o#er stations •Recall that a typical fission of *< will produce two

,and sometimes */ product neutrons.

•These neutrons have a wide range

of kinetic energies E 8 .•:f the E 8 value of a neutron is too

high$ it can pass through a *<

nucleus without causing it to split.

•:f the E 8 value is too small$ it will Cust bounce off of the *< nucleus

without e'citing it at all.



too

fast

too

slow


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escri$ing nuclear o#er stations •5ost of the neutrons produced in a

reactor are fast neutrons$ unable to

split the *< nucleus.

•These fast neutrons will eventuallybe captured by *8


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escri$ing nuclear o#er stations•:n order to shut down$ start up$

and change the reaction rate in

a reactor$ neutronabsorbing

control rods are used.•Retracting the control

rods will increase the

reaction rate.

•:nserting the controlrods will decrease the

reaction rate.

•2ontrol rods are made

of cadmium or boron

steel.



m " $ e r a

t " r

m " $ e r a t " r

m " $ e r a t " r

m " $ e r a

t " r


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escri$ing nuclear o#er stations•The whole purpose of the reactor

core is to produce heat through fission.

•The fuel rods$ moderator and

control rods are all surroundedby water$ or some other thermal

absorber that can be circulated.

•"ome reactors use liquid sodiumI

•The e'tremely hot water fromthe reactor core is sent to the

%eat e3c%anger which acts like

the boiler in a fossil fuel power

plant.



m " $ e r

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Topic 8.1 - Energy Sources