Download CH01b/energyc1.ppt

Heat and Work: Part 2
•
•
•
•
•
Conservation of Energy
Heat Engines
Second Law of Thermodynamics
Energy Efficiency
OTEC
Energy in the News
• Possible solutions to Energy Problems
–
–
–
–
1) Smart Buildings and Machines
2) Superconductive Cables
3) Fewer Phantom Loads
4) Distributed Generation
•
•
•
•
•
A) Solar Cells
B) Wind
C) Diesel Generators
D) Microturbines
E) Fuel Cells
Equilibrium of Heat Loss
Heat Loss
• Hypothermia-what causes it? Basic physics
• Lakes-ice and summer warmth. Why
retained?
• Space blankets-very thin-what do they do?
• Why cold when standing near a window in
winter?
• Why warm near a fire?
Heat Engines
Two basic types of heat engines
• What are they?
Vapor or Rankine Cycle
• Steam engines
• Heat pumps
Gas Cycle
• Automobiles (Internal Combustion)
• Jet Engines (External Combustion)
• Where is the fuel burned?
• What does the force from burning move?
Ocean Thermal Energy
Conversion
Practicalities of OTEC
•
•
•
•
•
Maximum Efficiency (Carnot efficiency)
=100% * ( Thigh-Tlow)/Thigh
T in degrees Kelvin
What is more efficient?
Thermal engines with large or small
temperature differences?
• When will it be 100% efficient?
Second Law of Thermodynamics
• Entropy (Disorder) always increases Unless
energy is added
• Examples:
• Kids room
• Spontaneous heat flow (Hot to Cold yes,
never cold to hot)
• Waste Heat is always present
Ideal Case
• A completely reversible process
• Do common heat engines use reversible
processes, why or why not?
Heat Pumps-How They Cool
Why Pump from Ground Rather
Than Air?
Heat Pump in Winter
Why Do Animals Burrow ?