Fossil Fuels. What is a Fossil Fuel? ●Burn to change chemical structure and release energy ●Coal ○ plants hardened by sand and mud (photosynthesis energy)

Fossil Fuels

What is a Fossil Fuel?

● Burn to change chemical structure and release energy

● Coal○ plants hardened by sand and mud

(photosynthesis energy)○ Must be dug up (expensive and difficult)○ rate used greater than rate of production

(non renewable)

What is a Fossil Fuel?

● Oil and Gas○ microscopic organisms hardened over time○ easier to extract (liquid form)○ non renewable

Geography

● Easy to find (as of 4000 years ago)● Must use coal near source (hard to

transport)○ eg: trains must carry coal

● OIl is easily pumped - can be transported (pipes)

● Drill technology allows drilling across world

History

● Originally wood used - more suited to needs

● Coal accessible 1769 (Industrial Revolution)○ Coal has twice the energy density of

wood● Crude oil refined to kerosine (1852)

○ oil has higher energy density than coal

● As of 2006 - 155 years of coal left (1E15kg)

● As of 2003 - about 1E14 liters of crude oil left

Transportation and Storage● Coal

○ Required a lot of time and energy to transport

○ Combustion risks○ More efficient to produce electricity

● Oil and Natural Gas○ Can be pumped through pipes○ Transportation Environmental problems○ Stored indefinitely

Energy Density

Energy Density( of Fuels) : The ratio of the energy released from the fuel to the mass of the fuel consumed

● The amount of energy that can be extracted per kg of fuel.

● Fuels with high energy density are easier to transport than those with lower densities.

Energy Density Chart

Power Stations A Power Station: An industrial place for the generation of electric power.

• Has a generator, a rotating machine that converts mechanical power into electrical power by creating relative motion between a magnetic field and a conductor.

• The energy source harnessed to turn the generator varies widely.

• It depends chiefly on which fuels are easily available, cheap enough and on the types of technology that the power company has access to.

Coal-fired Power Stations

● Coal Steam● Steam

Electricity● Steam Water

Coal-fired Power Stations

● Sources of waste heat:○ exhaust gas○ turbine condensing○ friction

● 40% Efficiency

Oil-fired Power Stations

● Same set-up as Coal-fired Power Stations ➢ Oil is burnt to produce energy

needed to boil the water➢ Cleaner, easier to get out of the

ground, and easier to transport than coal

● Efficiency is about 59%

Gas-fired Power Station ● More Efficient than

coal➢ Two stages of energy use ➢ Burning gas goes

through a turbine => heat produced is used to boil water => steam powers a steam turbine

Gas-fired Power Stations

● Up to 59% efficient

● If wasted heat goes to homes => 80% efficient

Environmental Repercussions

• Coal-fired and Gas-fired Power Stations= harmful pollution from exhaust

• Oil refinement=efficiency… but also= oil spills ➢ Serious consequences (i.e. BP Oil Spill)

Power Station developments focus on recovering exhaust (by different trapping techniques) back into the ground for reuse

Practice Problem #1

When a car is driving at 80 km/h it is doing work against air resistance at a rate of 40kW

a) How much work does the car do against air resistance in 1 hour?40E3(J/s) * 60 * 60 = 1.44 E8 J

b) If the engine is 75% efficient, how much energy must the car get from fuel?

Problem 1 (cont)

1.44E8 J/.75 = 1.92E8 Jc) If the energy density of the fuel is 45.8 MJ/kg, how many kg of diesel will the car use?1.92E8 J/45.8E6 J/kg = 4.2kg

Practice Problem #2

A coal-fired power station gives out 1000 MW of power

a) How many joules will be produced in one day?1000E6 J * 60 * 60 * 24 = 8.64E13

b) If the efficiency is 40%, how much energy goes in?

Problem 2 (cont)

8.64E13 J/ .4 = 2.16E14 Jc) The energy density of coal is 32.5 MJ/kg. How many kg are used?2.16E14 J/32.5E6 J/kg = 6.65E6kg

d) How many rail trucks containing 100 tons each are delivered per day?1 ton = 1000 kg

Problem 2 (cont)

6.65E6/(1000*100) = 66.567 rail trucks

Nuclear Power

Austyn HowardCiara JasinskiDillon LabbanTyler Ritter

The Fission Reaction

• Big nucleus splits into two smaller nucleio Loss of mass and energy, E=mc2

i.e. 236U → 92Kr + 142Ba + 2n Some neutrons are lost, so

mass is lost The total number of protons

remains the same

The Chain Reaction• Splitting a nucleus requires energy

o Can be gained by adding a neutron

• Adding a neutron increases the binding energy of the nucleuso Nucleus can’t get rid of this energy and splits in twoo Results in too many neutrons, so some are released

• Released neutrons are captured by other nuclei, resulting in more nuclei splitting and a chain reaction

Moderation of Neutrons

• Chain reaction only occurs if neutrons are moving slowlyo Otherwise they pass through the nucleuso KE should be about 1 eV

• Neutrons must be slowed downo Moderator nuclei are placed between nuclei where

fission must occur in order to slow them down

Critical Mass

• Definition: the minimum mass required for a chain reactiono Size of the reacting element, i.e. uranium, matters

If it’s too small, the neutrons will pass the uranium before they slow down enough

Nuclear Fuel

• Natural Uranium is mostly made up of 238-U (99.3%) and 235-U (0.7%). Before it can be used as nuclear fuel it needs to go through fuel enrichment.o in nuclear reactors the fuel is stored inside small cylinders that are

stacked together to make rods

• Depleted uranium is used to penetrate armored vehicles, is 40% less radioactive than typical uranium

• When U-235 is used up it makes

Pu-239 that goes through fission

and can then be used for energy

production or bombs

Controlling the rate of reactionThe loss of control: The atom bomb

• If more than one neutron from each fission goes on to make another fission then the reaction will accelerate; if less than one then it will slow down

• In order to keep the bomb from exploding before hitting the ground the uranium and moderator are kept separate from each other

• Weapon grade amount of Uranium and isotope:o 85% 235-U is considered ‘weapon grade’ (about the same amount as

a soft drink can would work)o 20% isotope is possible to make a bomb

• The only way to slow down the reaction is to introduce neutron absorbing rods (such as Boron) in between the fuel rods

The Nuclear Power Station

It’s mechanism is similar to that of a furnace in a steam generator

nuclear reactor

The Nuclear Power Stationnuclear reactor:

an apparatus or structure in which fissile material can be made to undergo a controlled, self-sustaining nuclear reaction with the consequent release of energy (heat).

3 crucial components:● fuel elements● moderator● cooling rods

The Nuclear Power Station

fuel elements

• heavy fissile elements o 235U or 238U

• when these fuels are struck by neutrons, they are in turn capable of emitting neutrons when they break apart.

chain reaction

The Nuclear Power StationModerator

• slows down neutrons

• heavy water (deuterium)

The Nuclear Power Station

control rods

• control the rate of fission reactions

• absorb neutrons

• Boron or Cadmium

Problems with Nuclear Energy

• getting the uraniumo you can mine it, but…

open-cast mining hurts the environment underground mining can hurt the workers

o you can use “leaching,” but… this can lead to contamination of groundwater

an open pit uranium mine in Namibia

Problems with Nuclear Energy

• Steps to Achieve a Meltdown1. do a bad job of controlling a nuclear reaction

2. allow fuel rods to melt

3. let the pressure vessel burst

4. release radioactive material into the atmosphere

Problems with Nuclear Energy

• meltdowns can be caused by:o a malfunction in the cooling systemo a leak in the pressure vessel

• the reactor would be severely damaged, but external damage is limited by the containment buildingo protects the outside from dangerous material,

protects the inside from missiles

Tyler

revisiting the diagram, but examining different components

Waste

• low level wasteo traces of radioactive material that need to be

carefully disposed of kept away from humans for 100-500 years

o old reactors left alone for many years before demolition encased in concrete

Waste

• high level waste (spent fuel rods)o plutonium isn’t safe for at least 240,000 yearso suggestions:

send it to the Sun put it at the bottom of the ocean bury it in the icecaps drop it into a very deep hole

o current plan: store it underwater at the site of the reactor for several years, then seal in steel cylinders

Waste

• weaponizing fuelo not enough 235U to be usedo process that enriches uranium into fuel, could be

used to make it weapons gradeo plutonium is most commonly used, can get it by

reprocessing spent fuel rods

Benefits of Fission

• Doesn’t produce CO2 or other greenhouse gases

• Fission results in increased sustainabilityo Plutonium can be created through the fission

process, resulting in 2000 years of fuelo Naturally found uranium is estimated to only last 100

years

Fusion

• was thought of as the answer to energy problems in the 1950s

• the total mass of the larger nuclei is less than that of the smaller two combined, the extra mass is turned into energy

• fusion reactors have come close to creating more energy than what was put in but is still not enough to commercially produce energy

• Plasma (a gas in which nuclei and electrons are separate) is used to create energy in the system

• magnetic fields are used to move the

particles through the system

Burning Plasma and Fusion Bombs

• the problem with creating fusion through energy is that every time more plasma is added the temperature has to be significantly increased in order for the nuclei to fuse

• the fusion bomb (hydrogen bomb) gives out a huge amount of energy but is not controllable

The Sun• gravity pulls all of the

mass inward → creates super duper high pressure (100,000,000,000 atm)

• hydrogen atoms fuse together → nuclear fusion

• 15 million degrees Fahrenheit at the core

The Sun

Wave PowerCatrina Letterman

Joseph LeungCyam Cajegas

The movement of air disturbs the water, causing waves

As waves spread out, they spread their energy, which can be used to turn turbines

Origin of waves

Device built on land that uses the kinetic energy of waves to force [compress] air in and out of a turbine which generates electrical energy

Oscillating Water Column (OWC) Ocean-Wave Energy Converter

Generating Electricity from Waves

A1. No Greenhouse Gas

Emissions2. Renewable Form of

Energy3. Enormous Energy

Potential (30 to 100 kW per meter)

4. Reliable (Most in the winter season)

5. Area Efficient (half square mile -> 30MW)

6. Offshore Wave Power

Advantages/Disadvantages

D1. Environmental Effects (sea life and tourism)

2. Expensive3. Regular Maintenance

4. Still Developing

Calculating Energy in a wave

Calculating Power in a wave

Waves of amplitude of 1 metre roll onto a beach at a rate of one every 12 seconds. If the wavelength of the waves is 120 metres, calculate:a. the velocity of the wavesb. how much power there is per metre along the shorec. the power along a 2km length of beach

Practice Problems

a. v = m/s120 meters/12 seconds = 10 m/s

b. Given that power = pvgA^2/2,(1kg/m^3 * 10 m/s * 9.8 m/s^2 * 1^2 m^2)

2= 49 kWc. 49 kW * 2000 m = 98 MW

Tidal Power

Origin of tides

Tides due to gravitational change of moon

Movement of tides can be used to drive turbines

Turbines are turned as tide comes in and goes out

A1. No Greenhouse Gas

Emissions2. Renewable Form of

Energy3. Predict Tides4. Maintenance Cheap5. Long Lifespan6. High Energy Density

Advantages/Disadvantages

D1. Environmental Effects (sea life and tourism)

2. Expensive3. Few Viable Locations4. Still Developing5. Unpredictable Tidal Energy

6. Short Duration of Power Generation

7. Energy Transmission expensive and difficult

TEST TEST TEST TEST TEST TEST

From what energy source are waves directly derived from?

a. The Sunb. Windc. Geothermald.The Moon

1.

What is NOT required to determine the power of a wave?

a. Densityb. Wavelengthc. Amplituded. Temperature of water

2.

The tides are mainly caused by…

a. The Sunb. The earth’s rotationc. The Moond. The wind

3.

How much power (approximately) can a pelamis generate

a. 150 horsepower b. 150 kJ/sc. 750 kWd. 750 kJ

4.

An oscillating water column generates power by…

a. Air compressionb. Tidal Changec. Wave’s Momentumd. Magnetic A/C Generator Buoy

5.

Waves off the 1.5km Leung Coast are used to generate power. A wave is modeled below

Free Response Question

a. Determine the wave velocity.b. Determine the mass of 1 wave approaching the coastline. The Density of Seawater is 1027 kg/m^3

c. Calculate the potential energy of one wave.

d. Calculate the power of one wave.

Free Response Question

e. BONUS: What should the wave velocity be in order to power the 30000kW mega-awesome laserlight show in Joseph’s Coastal Mansion?

Free Response Question

Ray WinKC Sumner

Seanna MorinJakob Hernandez

Wind Energy

WindSolar energySun heats earth, creates wind

Solar Energy

Kinetic Energy of

Wind

Kinetic Energy of Turbine

Electrical Energy

Coastal WindsDue to different rates of heating of the land

and seaSea has a larger specific heat capacity than

the landExample: Wind at beaches

Katabatic WindsFormed when high air pressure is caused by

dense cold air pressing down at the top of a mountainAir flows downhill

Examples:When cold air from Alps and Massif flow

down towards Mediterranean coast

The Wind TurbineSimilar to a fan or a propeller on an

airplaneAir pushes the fan blades causing a

generator to turn, creating electrical energyUsually turbines grouped together in “wind

farms”

The Wind TurbineEnergy Calculations

Mass of column of air passing trubine in one second

The Wind TurbineFormula assumes wind stops moving after

it passes turbineAll kinetic energy is not transferred to the

turbineTheoretically, maximum percentage of wind’s

energy that can be extracted using a turbine is 59%

Also finds power due to the calculation using mass of air that passes through in one second

Places for Wind TurbinesA windy placeRegular wind

Turbine doesn’t have to change orientationEasy to lay power linesEasy to build

AdvantagesClean production

No harmful chemicalsRenewable energy sourceFree energy source

After initial cost

DisadvantagesWind is unreliableLow energy density

Large area required for significant energyRuins country landscapeCan be noisyBest places often far from population

centers

Sample ProblemsA community wants to build a wind farm to

fit its needs.Total required annual energy output: 100 TJSpace for 20 wind turbinesAverage annual wind speed: 9 ms-2

Deduce the average power output required for one turbine

Estimate the blade radius that will give a power output found in part a (Density of Air = 1.2kgm-3)

Sample ProblemDeduce the average power output required

for one turbine

There are 20 turbines

Sample ProblemEstimate the blade radius that will give a

power output found in part a (Density of Air = 1.2kgm-3)

Solar PowerBy Ceres, Jace, Michael, and Terry

Energy from the Sun

• The sun emits 3.9E26 J per second of electromagnetic radiation

• This energy spreads out by the inverse square law since the energy is distributed in a sphere

Inverse Square Law

• Intensity can be found by the formulaI=P/

(4πr2)I=Intensity (power per unit area)P= total power of point source

r= distance away from the point source

Solar Power intensity on earthPower per meter squared of solar energy above the Earth’s atmosphere: (solar constant)

Earth’s orbital radius: 1.5E11 mIntensity = 3.90E26 / (4π X 1.5E11)2= 1380 W·m-2

Solar Power on Earth’s Surface

• Amount of solar radiation that reaches the Earth surface depends on how much atmosphere the light has to get through

• Different latitudes on the Earth’s surface will receive different amounts of radiation

• Will also vary with the seasons

North

More

Less

Atmosphere Travel Distance

Solar Heating Panel

• Panel uses heat from sun to heat water for household use. o Sunlight goes through glass panel and is

absorbed by black metal plate.o Hot metal plate then heats water for use.

Solar Heating Panel

Solar Example

A 5 m2 solar heating panel is in a place where the sun’s intensity is 800 Wm-2.

What is the power incident on the panel?800 Wm-2 * 5 m2 = 4000 W

Solar Example

If it is 40% efficient, how much energy is absorbed per second?

4000 W * .4 = 1600 WIf 1 kg of water flows through the system in 1 minute, how much will its temperature increase?

Solar Example

If 1 kg of water flows through the system in 1 minute, how much will its temperature increase? (Specific heat capacity of water 4200 Jkg-1K-1)

q = mcT T = q/(mc)1600 W*(60 s/1 min)/(1 kg*4200 Jkg-1C-1) = 22.9 K

Photovoltaic Cell

• Converts solar radiation into electrical energy

• Semiconductors release electrons when photons of lights are absorbed

• Different types of semiconductors create an electric field

Photovoltaic Cell

• Only produce a small amount of p.d. and currento Using in series will get higher voltageso Using in parallel can provide higher current

Photovoltaic Cell

Photovoltaic Example

A photovoltaic cell of 1 cm2 is placed in a position where the intensity of the sun is 1000 Wm-2.

If it is 15% efficient, what is the power absorbed?1 cm2 = .0001m2

1000 Wm-2 * .0001 m2 = .1W

Photovoltaic Example

.1 W * .15 = .015 WIf the potential difference across the cell is 0.5 V, how much current is produced?

P = IV I = P/V0.015 W/0.5 V = .03 A

Advantages vs. Disadvantages

Advantages• No harmful chemical

by-products

• Renewable

• Free energy source

Disadvantages• Only utilized during

the day

• Unreliable (cloudy days)

• Large area needed for significant amount of energy

Energy, Power, and Climate

Change: Hydropower

Michele WangTori Barr

Diego MartinezJacobo Grimaldo

What is hydroelectric power?

The production of electricity through the conversion of gravitational potential energy from falling or flowing water.

Originally from the sun:• Heat from the sun turns the water into vapor,

which turns into clouds, which go over the land and rain over the land.

• Rain water on high ground has PE, and can be converted into electricity through rivers and lakes.

Origin

Water Cycle

PE=mgh● h is the difference between the outlet from the

lake and the turbine. ● Average height is used where the height is

uneven.

Gravitational PE

• Turn off hydroelectric power at night.• Excess power from coal-fired power stations can

be used to pump water into a reservoir. (costly to turn off and back on)

• Water from reservoir can drive turbines during night.

• Reduces amount of fossil fuel used.

Pumped Storage Schemes

Pumped Storage Schemes Cont.

• Use water diverted from a fast-flowing river without damming the river.

• For areas where there would be need to dam river valley to create a difference in height for the turbines.

Run-of-the-river power stations

• Supplying electricity can be done through wires.• Result in energy loss since wires get hot.• Factories dependent on this energy are located

closer to the power stations. • Some build small-scale power stations near

where people live.

Issues

Pros:• Renewable• Emission-free• Dams can provide a storm surge barrier• Local environmental impact, in contrast to global• Regulate water flow

Cons:

• Construction costs• Requires specific locations• Harm habitats along rivers• Non-continuous