1. Energy, Power, and Climate Change

2. Chapter 7.1 Energy degradation and power generation

3. Energy Degradation Sankey Diagram of energy flow in a flash light. Degradation of Energy – As energy is transformed from on type to another there is energy lost in the form of heat. This energy becomes less useful and is therefore degraded. The width of the arrow is proportional to energy flow. Efficiency, e = work/input energy If the input is 100 J and the useful work that came from the transfer is 5 J, then e, is 5%.

4. Energy Degradation Can you think of three forms of degraded energy? 1.Heat 2.Sound 3.Deformation Does this violate conservation of energy? US Annual Energy Flow

5. History of Energy Civilization has increased the demand for energy per person from 8 MJ per day to 300 MJ per day. This is an increase of 3750 %. As population increases this equates to an enormous demand for energy. Annual world production of energy is at 1.5 x 10^21 J Where do we get that energy from?

6. Energy Sources RenewablesNon-renewables Infinite sources of energy. Solar, Wind, Wave, Tidal, Geothermal Finite sources which are being depleted and will run out. Fossil Fuels, Nuclear Fuels,

7. Facts About Fuels Type of fuelRenewable?CO 2 emissions? Fossil fuelsNoYes NuclearNo HydroelectricYesNo WindYesNo SolarYesNo WaveYesNo

8. Energy Density FuelEnergy Density (MJ/kg) Fusion fuel300,000,000 Uranium-23590,000,000 Gasoline (Petrol)46.9 Diesel45.8 Biodiesel42.2 Crude oil41.9 Coal32.5 Sugar17.0 Wood17.0 Cow dung15.5 Household waste10 Energy Density – The energy that can be obtained per unit mass. The unit is in Joule/Kg. E=mc 2 is used for nuclear fuels. Potential Energy is used to determine energy density of hydroelectric plants.

9. Fossil Fuels Created over millions of years through natural decomposition of plant and animal matter. By product is CO 2 and H 2 O. Used for transportation and electricity production. Coal burning power plants are 30% efficient. Natural Gas is typically 42% efficient.

10. Fossil Fuel 1.Fossil Fuel is burned in a furnace. 2.This heats water which turns to steam. 3.Steam has pressure to spin a turbine. 4.Turbine converts rotational energy in to electrical energy.

11. Nuclear Fission U 238 is most abundant isotope of Uranium found in nature. U-235 is the isotope (.7% found naturally) used as fission fuel source. Uranium is enriched until 3% of U-235 is present. This creates critical mass for a sustainable reaction.

12. Nuclear Fission Fission: splitting a heavy nucleus into lighter nuclei only plutonium & some isotopes of uranium

13. Nuclear Fission Fission - example ◦ 235 92 U + 1 0 n → 236 92 U → 140 54 Xe + 94 38 Sr +2 1 0 n + energy ◦Fissioning 1.0 g of uranium-235 yields 1.2×10 12 J, enough energy to keep 375 100-watt light bulbs lit for a year. ◦Super High Energy Density

14. Nuclear Fission chain reaction: neutrons in products can cause more fission critical mass: mass, density needed for self- sustaining chain reaction

15. Nuclear Fission Fuel Rods and Control Rods are used to moderate the reaction taking place. (more fuel rods more reactions, and more control rods less reactions). During the Uranium reactions Plutonium 239 is created. This does not occur naturally and is a fuel that can be used in nuclear weapons. (Hence the national security concerns for nuclear power).

16. Nuclear Fusion Fusion – small atoms form a larger atom. 2 1 H + 3 1 H → 4 2 He + 1 0 n + energy Both Deuterium and Tritium at these high temperatures are ionized and therefore positively charged. Conditions must be met to overcome this awesome electric force. Engineering monstrosities such as NIF and Tokamak have been built to do this.

17. Nuclear Fusion - Tokamak Magnetic Confinement Fusion Fusion Fuel is heated to a plasma and then accelerated with electric and magnetic fields to initiate fusion. Fusion has occurred, but not enough to outweigh the energy put in to create it.

18. Nuclear Fusion NIF National Ignition Facility at LLNL Inertial Confinement Fusion 192 Lasers impact target simultaneously to produce environment consistent with the core of our sun.

19. Solar Power Solar power harnesses the brightness of the sun… 1400 W/m 2. What assumptions go into this number? Luminosity of the sun is 3.9 x 10 26 Watts. Active solar devices – Low reflecting materials absorb heat in order to convert solar energy into hot water. Photovoltaic cells – converts sunlight into direct current.

20. Solar Power Solar energy is variable by about 5% What could cause this? Daily insolation- Total amount of energy received by one square meter in a day.

21. Hydroelectric Power Power derived from moving water masses. P = mgh/ Δt = ρΔVgh/ Δt

22. Wind Power P = C p ½ ρ A v 3 ρ = air density A = area spanned by blades v = velocity of wind C p = efficiency factor or power coefficient.

23. Wave Power P/L = ρgA 2 v/2 P /L = power per unit length ρ = density of water g = gravity A = amplitude of wave v = waves velocity