2What is a Fossil Fuel?Burn to change chemical structure and release energyCoalplants hardened by sand and mud (photosynthesis energy)Must be dug up (expensive and difficult)rate used greater than rate of production (non renewable)
3What is a Fossil Fuel? Oil and Gas microscopic organisms hardened over timeeasier to extract (liquid form)non renewable
4Geography Easy to find (as of 4000 years ago) Must use coal near source (hard to transport)eg: trains must carry coalOIl is easily pumped - can be transported (pipes)Drill technology allows drilling across world
5History Originally wood used - more suited to needs Coal accessible 1769 (Industrial Revolution)Coal has twice the energy density of woodCrude oil refined to kerosine (1852)oil has higher energy density than coalAs of years of coal left (1E15kg)As of about 1E14 liters of crude oil left
6Transportation and Storage CoalRequired a lot of time and energy to transportCombustion risksMore efficient to produce electricityOil and Natural GasCan be pumped through pipesTransportation Environmental problemsStored indefinitely
7Energy DensityEnergy Density( of Fuels) : The ratio of the energy released from the fuel to the mass of the fuel consumedThe 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.
9Power StationsA 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.
10Coal-fired Power Stations Coal SteamSteam ElectricitySteam Water
11Coal-fired Power Stations Sources of waste heat:exhaust gasturbine condensingfriction40% Efficiency
12Oil-fired Power Stations Same set-up as Coal-fired Power StationsOil is burnt to produce energy needed to boil the waterCleaner, easier to get out of the ground, and easier to transport than coalEfficiency is about 59%
13Gas-fired Power Station More Efficient than coalTwo stages of energy useBurning gas goes through a turbine => heat produced is used to boil water => steam powers a steam turbine
14Gas-fired Power Stations Up to 59% efficientIf wasted heat goes to homes => 80% efficient
15Environmental Repercussions Coal-fired and Gas-fired Power Stations= harmful pollution from exhaustOil refinement=efficiency… but also= oil spillsSerious consequences (i.e. BP Oil Spill)Power Station developments focus on recovering exhaust (by different trapping techniques) back into the ground for reuse
16Practice Problem #1When a car is driving at 80 km/h it is doing work against air resistance at a rate of 40kWa) How much work does the car do against air resistance in 1 hour?40E3(J/s) * 60 * 60 = 1.44 E8 Jb) If the engine is 75% efficient, how much energy must the car get from fuel?
17Problem 1 (cont)1.44E8 J/.75 = 1.92E8 Jc) If the energy density of the fuel is MJ/kg, how many kg of diesel will the car use?1.92E8 J/45.8E6 J/kg = 4.2kg
18Practice Problem #2A coal-fired power station gives out 1000 MW of powera) How many joules will be produced in one day?1000E6 J * 60 * 60 * 24 = 8.64E13b) If the efficiency is 40%, how much energy goes in?
19Problem 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 = 6.65E6kgd) How many rail trucks containing 100 tons each are delivered per day?1 ton = 1000 kg
22The Fission Reaction Big nucleus splits into two smaller nuclei Loss of mass and energy, E=mc2i.e. 236U → 92Kr + 142Ba + 2nSome neutrons are lost, so mass is lostThe total number of protons remains the same
23The Chain Reaction Splitting a nucleus requires energy Can be gained by adding a neutronAdding a neutron increases the binding energy of the nucleusNucleus can’t get rid of this energy and splits in twoResults in too many neutrons, so some are releasedReleased neutrons are captured by other nuclei, resulting in more nuclei splitting and a chain reaction
24Moderation of Neutrons Chain reaction only occurs if neutrons are moving slowlyOtherwise they pass through the nucleusKE should be about 1 eVNeutrons must be slowed downModerator nuclei are placed between nuclei where fission must occur in order to slow them down
26Critical MassDefinition: the minimum mass required for a chain reactionSize of the reacting element, i.e. uranium, mattersIf it’s too small, the neutrons will pass the uranium before they slow down enough
27Nuclear FuelNatural 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.in nuclear reactors the fuel is stored inside small cylinders that are stacked together to make rodsDepleted uranium is used to penetrate armored vehicles, is 40% less radioactive than typical uraniumWhen U-235 is used up it makesPu-239 that goes through fissionand can then be used for energyproduction or bombs
28Controlling the rate of reaction The 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 downIn order to keep the bomb from exploding before hitting the ground the uranium and moderator are kept separate from each otherWeapon grade amount of Uranium and isotope:85% 235-U is considered ‘weapon grade’ (about the same amount as a soft drink can would work)20% isotope is possible to make a bombThe only way to slow down the reaction is to introduce neutron absorbing rods (such as Boron) in between the fuel rods
29The Nuclear Power Station nuclear reactorIt’s mechanism is similar to that of a furnace in a steam generator
30The Nuclear Power Station nuclear 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 elementsmoderatorcooling rods
31The Nuclear Power Station fuel elementsheavy fissile elements235U or 238Uwhen these fuels are struck by neutrons, they are in turn capable of emitting neutrons when they break apart.chain reaction
32The Nuclear Power Station Moderatorslows down neutronsheavy water (deuterium)
33The Nuclear Power Station control rodscontrol the rate of fission reactionsabsorb neutronsBoron or Cadmium
34Problems with Nuclear Energy getting the uraniumyou can mine it, but…open-cast mining hurts the environmentunderground mining can hurt the workersyou can use “leaching,” but…this can lead to contamination of groundwater
36Problems with Nuclear Energy Steps to Achieve a Meltdown1. do a bad job of controlling a nuclear reaction2. allow fuel rods to melt3. let the pressure vessel burst4. release radioactive material into the atmosphere
37Problems with Nuclear Energy meltdowns can be caused by:a malfunction in the cooling systema leak in the pressure vesselthe reactor would be severely damaged, but external damage is limited by the containment buildingprotects the outside from dangerous material, protects the inside from missilesTyler
38revisiting the diagram, but examining different components
39Wastelow level wastetraces of radioactive material that need to be carefully disposed ofkept away from humans for yearsold reactorsleft alone for many years before demolitionencased in concrete
40Waste high level waste (spent fuel rods) plutonium isn’t safe for at least 240,000 yearssuggestions:send it to the Sunput it at the bottom of the oceanbury it in the icecapsdrop it into a very deep holecurrent plan: store it underwater at the site of the reactor for several years, then seal in steel cylinders
41Waste weaponizing fuel not enough 235U to be used process that enriches uranium into fuel, could be used to make it weapons gradeplutonium is most commonly used, can get it by reprocessing spent fuel rods
42Benefits of Fission Doesn’t produce CO2 or other greenhouse gases Fission results in increased sustainabilityPlutonium can be created through the fission process, resulting in 2000 years of fuelNaturally found uranium is estimated to only last 100 years
43Fusion 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 energyfusion reactors have come close to creating more energy than what was put in but is still not enough to commercially produce energyPlasma (a gas in which nuclei and electrons are separate) is used to create energy in the systemmagnetic fields are used to move theparticles through the system
44Burning 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 fusethe fusion bomb (hydrogen bomb) gives out a huge amount of energy but is not controllable
45The Sungravity pulls all of the mass inward → creates super duper high pressure (100,000,000,000 atm)hydrogen atoms fuse together → nuclear fusion15 million degrees Fahrenheit at the core
48Origin of waves The movement of air disturbs the water, causing waves As waves spread out, they spread their energy, which can be used to turn turbines
49Oscillating Water Column (OWC) Ocean-Wave Energy Converter 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
53Advantages/Disadvantages No Greenhouse Gas EmissionsRenewable Form of EnergyEnormous Energy Potential (30 to 100 kW per meter)Reliable (Most in the winter season)Area Efficient (half square mile -> 30MW)Offshore Wave PowerD1. Environmental Effects (sea life and tourism)2. Expensive3. Regular Maintenance4. Still Developing
56Practice ProblemsWaves 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
57a. v = m/s120 meters/12 seconds = 10 m/sb. 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
61Turbines are turned as tide comes in and goes out
62Advantages/Disadvantages No Greenhouse Gas EmissionsRenewable Form of EnergyPredict TidesMaintenance CheapLong LifespanHigh Energy DensityD1. Environmental Effects (sea life and tourism)2. Expensive3. Few Viable Locations4. Still Developing5. Unpredictable Tidal Energy6. Short Duration of Power Generation7. Energy Transmission expensive and difficult
71Free 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^3c. Calculate the potential energy of one wave.d. Calculate the power of one wave.
72Free 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?
74Kinetic Energy of Turbine WindSolar energySun heats earth, creates windSolar EnergyKinetic Energy of TurbineKinetic Energy of WindElectrical Energy
75Coastal Winds Due to different rates of heating of the land and sea Sea has a larger specific heat capacity than the landExample: Wind at beaches
76Katabatic WindsFormed when high air pressure is caused by dense cold air pressing down at the top of a mountainAir flows downhillExamples:When cold air from Alps and Massif flow down towards Mediterranean coast
78The Wind Turbine Similar to a fan or a propeller on an airplane Air pushes the fan blades causing a generator to turn, creating electrical energyUsually turbines grouped together in “wind farms”
79The Wind Turbine Energy Calculations Mass of column of air passing trubine in one second =𝜌𝑣𝜋 𝑟 2𝐾 𝐸 = 1 2 𝑚 𝑣 2 = 1 2 𝜌𝑣𝜋 𝑟 2 𝑣 2 = 1 2 𝜌𝜋 𝑟 2 𝑣 3
80The 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
81Places for Wind Turbines A windy placeRegular windTurbine doesn’t have to change orientationEasy to lay power linesEasy to build
82Advantages Clean production Renewable energy source Free energy source No harmful chemicalsRenewable energy sourceFree energy sourceAfter initial cost
83Disadvantages Wind is unreliable Low energy density Large area required for significant energyRuins country landscapeCan be noisyBest places often far from population centers
84Sample 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-2Deduce the average power output required for one turbineEstimate the blade radius that will give a power output found in part a (Density of Air = 1.2kgm-3)
85Sample ProblemDeduce the average power output required for one turbine𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 𝑖𝑛 𝑂𝑛𝑒 𝑌𝑒𝑎𝑟= 100 × ×60×24×365There are 20 turbines3.1× =1.6× 𝑊
86Sample ProblemEstimate the blade radius that will give a power output found in part a (Density of Air = 1.2kgm-3)𝑃𝑜𝑤𝑒𝑟 𝑂𝑢𝑡𝑝𝑢𝑡= 1 2 𝜌𝜋 𝑟 2 𝑣 31.6 × 10 5 = 1 2 (1.2)𝜋 𝑟 2 (9) 3𝑟≈10.8 𝑚
87By Ceres, Jace, Michael, and Terry Solar PowerBy Ceres, Jace, Michael, and Terry
88Energy from the SunThe sun emits 3.9E26 J per second of electromagnetic radiationThis energy spreads out by the inverse square law since the energy is distributed in a sphere
89Inverse Square Law Intensity can be found by the formula I=P/(4πr2) I=Intensity (power per unit area)P= total power of point sourcer= distance away from the point source
90Solar Power intensity on earth Power 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= W·m-2
91Solar Power on Earth’s Surface Amount of solar radiation that reaches the Earth surface depends on how much atmosphere the light has to get throughDifferent latitudes on the Earth’s surface will receive different amounts of radiationWill also vary with the seasons
95Solar ExampleA 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
96Solar ExampleIf 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?
97Solar ExampleIf 1 kg of water flows through the system in 1 minute, how much will its temperature increase? (Specific heat capacity of water Jkg-1K-1)q = mcT T = q/(mc)1600 W*(60 s/1 min)/(1 kg*4200 Jkg-1C-1) = K
98Photovoltaic Cell Converts solar radiation into electrical energy Semiconductors release electrons when photons of lights are absorbedDifferent types of semiconductors create an electric field
99Photovoltaic Cell Only produce a small amount of p.d. and current Using in series will get higher voltagesUsing in parallel can provide higher current
101Photovoltaic ExampleA photovoltaic cell of 1 cm2 is placed in a position where the intensity of the sun is Wm-2.If it is 15% efficient, what is the power absorbed?1 cm2 = .0001m21000 Wm-2 * m2 = .1W
102Photovoltaic Example .1 W * .15 = .015 W If 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
103Advantages vs. Disadvantages No harmful chemical by-productsRenewableFree energy sourceDisadvantagesOnly utilized during the dayUnreliable (cloudy days)Large area needed for significant amount of energy
105What is hydroelectric power? The production of electricity through the conversion of gravitational potential energy from falling or flowing water.
106Origin 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.
108Gravitational PE PE=mgh h is the difference between the outlet from the lake and the turbine.Average height is used where the height is uneven.
109Pumped Storage Schemes 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.
111Run-of-the-river power stations 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.
112Issues 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.
113Pros: Renewable Emission-free Dams can provide a storm surge barrier Local environmental impact, in contrast to globalRegulate water flow
114Cons: Construction costs Requires specific locations Harm habitats along riversNon-continuous