Units of Energy

1
Units of Energy
Joule (J) 1 Joule 1 Nm 1 Ws 1 m2kg / s2
Therm 100,000 BTU (1 therm 105.5 MJ)
Kilowatt-hour (KWh) 1KWh 1000 W x 3600 s 3.6
MJ
British Thermal Unit (BTU) 1 BTU is equivalent
to energy required to raise the temperature of 1
pound of water by 1 degree Fahrenheit (1 BTU
1055 J).
Calorie (cal) 1 cal is equivalent to energy
required to raise the temperature of 1 gram of
water by 1 degree Celsius (1 cal 4.1855 J).
erg 10-7 J
eV 1.602 x 10-19 J
2
Forms of Energy
1 Mechanical Energy a) Potential
(gravitational) energy b) Kinetic energy 2
Internal Energy Heat 3 Electromagnetic
energy a) Electricity b) Electromagnetic
radiation 4 Chemical energy Molecular bonds 5
Nuclear energy Nuclear bonds
3
Some energy examples
Earth Translational kinetic energy Rotationa
l kinetic energy
Toyota Camry Kinetic energy at 70
mph Vertical ascent if all kinetic energy is
converted into potential
100 W light bulb Energy use per day
Human survival Required Energy per day
4
(No Transcript)
5
Energy balance of the US (in Quadrillion BTU
1015 BTU 1018 J)
6
Energy consumption per person in the US
7
Spectrum of Solar Radiation
8
Solar radiation
9
Energy Conversion Processes
Converted energy form
Initial energy form
Radiant
Heat
Chemical
Mechanical
Electrical
Nuclear
Reactor
Fuel cell, Battery discharging
Burner,Boiler
Chemical
Radiant
Photosynthesis
Absorber
Photovoltaic cell
Electrolysis, Batterycharging
Lamp,Laser
Electric motor
Resistance, Heat pump
Electrical
Electric generator, Magnetohydrodynamic(MHD)
generator
Friction, Churning
Mechanical
Turbines
Thermionic thermoelectricgenerators
Convector, Radiator, Heat pipe
Thermodynamicengines
Heat
10
(No Transcript)
11
Reading for Monday, 17 AprilChapter 3 from L R
Radovic Energy and Fuels in SocietyLaws of
Energy Conversion Chapter 4 from L R Radovic
Energy and Fuels in SocietyEfficiency of
Energy Conversionpdf available on course
website http//www.bren.ucsb.edu/academics/course
.asp?number288