U.S. Wind power since 1995 (mQuads energydelivered/year) From EIA website Annual Energy Report: % annual growth DATA FIT

Hubbert Curve H&K fig Exponential extrapolation World Coal Production Curve Data Finite resource -> Final answer is 0 Exponential growth CANNOT be sustained in a World of FINITE resources!!

Renewable Resource A resource that can be replenished on a time scale much shorter than the lifetime of the civilization exploiting it (e.g. wood, crops, hydro- electric). A resources whose expected lifetime is much longer than the lifetime of the civilization exploiting it (e.g. solar, wind, tidal). (NOTE: the book says “a resource that cannot be used up”, technically there is no such thing, but from a practical matter it is the same as above).

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)

Energy Conversions Thermal energy in the sun is converted to radiant energy (light, IR, Visible, UV). Solar cell converts radiant energy to electricity (low efficiency) Electricity is transmitted from the cell to the electric motor) The motor converts electrical energy into mechanical energy.

Inside a Nuclear Power Plant

Seoinchon (?) Power plant: 57% i.e. for every 1000J of energy that comes into the plant (as natural gas), only 570 J, or only a bit more than half, goes out as useful electricity. In the next chapter, we will see that conversions on down the line are also less than 100% efficient. Conventional power plants may be closer to only 35%-40% efficient!

Energy Losses in a Car NOTE: only 13% gets to the wheels and ALL of that goes to thermal energy (eventually) See also:

H&K Car Energy Losses

CAFE standards (Corporate Average Fuel Economy) From the D.O.T. Note that they have been constant since 1990! Just within the last year a mandate came to increase to 37.5 for passenger cars by

CAFE performance pdf standard Recent Changes Mandate Increase to 37.5 mpg by 2015

Newton’s second Law of Motion F = ma F – force (1 Newton = 1 kg * 1 m/s 2 ) m – mass changea - acceleration (rate of change of velocity) velocity – speed and direction Forces cause CHANGES in motion, they do not cause motion itself!!!

Work W = F // d Work is the product of a displacement (change of position) and a force (only the component along the displacement counts) 1 Joule = 1 Newton * 1 meter NOTE: the Work is positive if the force is along the motion, negative if it is directed opposite to the motion.

Newton’s third Law of Motion F 12 = -F 21 If object 1 pushes/pulls on object 2, then object 2 pushes/pulls back on 1 with a force of exactly the same strength but opposite direction. A consequence of this, is that WORK can be seen as a way of exchanging energy between two objects/systems. –One object gains energy (W>0), the other loses it (W<0)!

Potential Energy For “conservative forces” (like gravity and ideal springs), we can define a “potential energy” as:  PE = - work done by the cons. force “  ” means “change in”: only changes in potential energy have any significance. E.G. Lifting a mass “m” through a height h:  PE = mgh Where the force on any object near the Earth’s surface is ‘mg’ and g=9.80m/s 2

Kinetic Energy Recall that kinetic energy is energy associated with MOTION. Numerically, it is given by: KE = ½ mv 2 Note that the units work out, but you’ll have to take my word for the ½ ! –The units for Energy: 1J = 1N.m = 1 (kg.m/s 2 ).m = 1 kg.m 2 /s 2

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 In many problems associated with energy therefore, you just have to be able to do accounting: Add all the energy at the beginning, and at the end, and the total must be the same in both cases!

ITAIPU (Brazil/Paraguay)

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)

Not all hybrids are created equal!

Car Weight vs. Time

Gas taxes in different countries