1. Conservation of Energy If only conservative forces act (e.g. only gravity), then Mechanical Energy is constant: KE i + PE i = KE f + PE f Today we will generalize this to include all forms of energy!

2. ITAIPU (Brazil/Paraguay) http://www.solar.coppe.ufrj.br/itaipu.html 12.6 GW capacity

3. ITAIPU (Brazil/Paraguay) 18 turbines, each producing roughly 715 MW 12.9 GW total output! (700 m 3 /s, effective height ~110m for each turbine) http://www.solar.coppe.ufrj.br/itaipu.html

4. Residential Electric Power Bill $145.6/1948 kWh = $0.0747/kWh Avg. Power: 1948kWh/31day.24h/day = 2.6 kW.

5. Commercial Power Costs Energy cost estimates for a project out at IUCF: use (i.e. energy) charge: $3105/(360hr*575kW)=$0.0147/kWh peak use (i.e. maximum power demand) charge: $13.11/kW Why is this different from the residential calculation?

6. DVB: Energy can be neither created nor destroyed; It can only be changed from one form to another First Law of Thermodynamics (generalized energy conservation) Quantify: W + Q =  PE +  KE +  TE Work+Heat exchanged= Change in (PE, KE and Thermal E) The rub, as we shall see, is that not all forms of energy are equally useful. In particular, thermal Energy is very easy to produce, but difficult to use.

7. Energy Conversions (Table 2.2) Automatically Happens! digestion thermal A key question to consider is with what EFFICIENCY can each of these Conversions be accomplished (Useful energy output/ total energy input)

8. Efficiency Efficiency = (useful E transferred)/(total E input) DeviceTransfer effectedEfficiency GeneratorsKinetic-Electrical70-99% Elec. MotorsElect.-Kinetic50-90% TransformerElectrical-Electrical95-99% Gas FurnaceChem.-Thermal70-95% Wind TurbineKinetic-Electrical35-50% Power PlantNucl/Chem-Elect.30-40% Fuel CellChem-Electrical50-70% Solar CellRadiant-Electrical5-28% Fluoresc. LightElectrical-Radiant20% Incandescent lightElectrical-Radiant5%

9. Energy Losses in a Car http://www.fueleconomy.gov/feg/atv.shtml NOTE: only 13% gets to the wheels and ALL of that goes to thermal energy (eventually) http://www.fueleconomy.gov/feg/hybrid_sbs_cars.shtml See also:

10. Efficiency example (H&K p75)

11. Not all hybrids are created equal! http://www.fueleconomy.gov/feg/hybrid_sbs.shtml

12. BMW hydrogen sports car “Our long-term EfficientDynamics strategy can be summed up with one vehicle: the BMW Hydrogen 7. As the world's first luxury performance sedan with hydrogen drive, it runs on the most plentiful element in the world and emits virtually nothing but water vapor. And because the infrastructure for refueling a hydrogen internal combustion engine is not yet complete, the V-12 engine also runs on gasoline at the push of a button, though emissions will result. “ http://www.bmwusa.com/uniquelybmw/EfficientDynamics?PANELID=4

13. Coal-fired Electric Power Plant

14. Lighting: Overall efficiency Incandescent light!

15. The Electromagnetic Spectrum

16. DVB: Energy can be neither created nor destroyed; It can only be changed from one form to another First Law of Thermodynamics (generalized energy conservation) Quantify: W + Q =  PE +  KE +  TE Work+Heat exchanged= Change in (PE, KE and Thermal E) The rub, as we shall see, is that not all forms of energy are equally useful. In particular, thermal Energy is very easy to produce, but difficult to use.

17. Efficiency Efficiency = (useful E transferred)/(total E input) DeviceTransfer effectedEfficiency GeneratorsKinetic-Electrical70-99% Elec. MotorsElect.-Kinetic50-90% TransformerElectrical-Electrical95-99% Gas FurnaceChem.-Thermal70-95% Wind TurbineKinetic-Electrical35-50% Power PlantNucl/Chem-Elect.30-40% Fuel CellChem-Electrical50-70% Solar CellRadiant-Electrical5-28% Fluoresc. LightElectrical-Radiant20% Incandescent lightElectrical-Radiant5%

18. Lighting: Overall efficiency Incandescent light! Roughly 1/3 of the residential/commercial energy sector goes to providing lighting; there are gains to be made here!

19. Light from hot objects Visible UVIR 6000K 2500K (x10)

20. Lighting efficiency comparison http://www.mge.com/home/appliances/lighting/comparison.htm LED’s (white)

21. Light Emitting Diodes (LED) http://alt-e.blogspot.com/2005/04/energy-efficiency-led-lights-to.html $58/bulb Consumes 6 W; “replaces” 50 W incandescent bulb http://store.starrynightlights.com/ledlightbulbs.html LED’s are best in cases where you want directional lighting (e.g. “task lighting”, or stop lights), since they emit a beam (unlike most other lights that emit in all directions)! They are not yet ready for high-luminosity applications. (e.g. street lights) due to power limitations.

22. What is Temperature? It is the quantity that determines the direction of heat flow (from higher Temperature to lower temperature) when two objects are brought into thermal contact. (“zeroth law of thermodynamics”) For gases under normal circumstances this is related to the average energy per molecule, BUT this relationship is not valid in all circumstances nor for all materials.

23. Example (H&K p95) You can heat up a beaker of water (or anything else) by either doing work (friction converts work to thermal energy) or by “heat transfer”

24. Generalized Energy conservation (H&K p79) Energy OUT Energy IN Energy Stored

25. Specific Heats Ice (near 0 o C) 2090 J/kg.K=2090 J/kg.C o Water (near 0 o C) 4186 J/kg.K=1000 cal/kg.C o Aluminum 900 J/kg.K Copper 387 J/kg.K This is how thermal energy and temperature are related!! Temperature Scales: 0 o C = 273.15 K ice melts at this temp 100 o C = 373.15 K water boils at this temp 0 K: absolute zero, the coldest temperature possible. Note that 1C o = 1 K. The Celsius degree and the Kelvin are the same size! The only difference in the scales is the position of the origin, hence the two scales are equivalent for talking about temperature DIFFERENCES, but not for talking about absolute temperatures.

26. Phase transitions in water