Energy:

• kJ
• BTU = 1.055 kJ
• kwh = 3600 kJ = 3412 BTU
• note 1 kwh is equivalent to a power of 1 kw for one hour
• therm = 100,000 BTU
• quad = 10¹⁵ BTU

Power:

• kw = kJ/s = 1000 watts = 1000 J/s
• kw = 0.746 hp (almost 3/4^th hp)
• MW (megawatt) = 1000 kw
• GW (gigawatt = billion) = 1000 MW

Volume:

• liter = 1000 cc
• cubic foot = 28.32 liters
• cubic meter = 1000 liters
• US gallon = 3.785 liters
• Barrel = 42 US gallons
• scf = std cubic foot, meaning the gas in one cubic foot has a pressure of 1 atm (normal pressure) and std temperature (15 deg C = 59 deg F, or frequently in US, 70 deg F). The weight of air in one scf is about 0.075 pounds. That is, the density of the air is 0.075 pounds/scf. In SI units, the density of air is about 1.2 kg/std cubic meter.

Mass:

• kg (kilogram) = 1000 grams
• kg = 2.205 pounds (lbm)
• metric ton = tonne = 1000 kg
• ton = short ton = 2000 pounds

Heating Values (typical):

• Barrel of crude oil: 5.8x10⁶ BTU
• Gasoline: 125,000 BTU/US gallon.
• Natural gas: 1000 BTU/scf
• note this varies with the source of the natural gas (ie, the gas field) and with modification along the way to the end user – in Western Washington the heating value of the gas delivered is typically 1020 to 1030 BTU/scf.
• Propane: could you figure out the heating value of the fuel in the propane tank you bought for your back-yard grill? Could you figure out the energy content of the fuel in the tank?
• Coal: what is heating value of coal? This is normally expressed as BTU per short ton, or as kJ per tonne. Do you think this would vary a lot with the source of the coal (ie, the location of the coal mine)?

For the auto engine discussed in class on Wednesday, we converted from:

Chemical energy (fuel) Þ

Thermal energy (the hot combustion gases in the cylinders) Þ

Mechanical energy (the output torque of the engine shaft)

We also generated some electrical energy from the output mechanical energy of the engine’s output shaft.

Thus, we have converted from chemical energy to three other forms of energy. Energy is convertible!

What is the original source of the chemical energy in the fuel?

• Gasoline Spark Engine in a typical automobile: 15-20% efficiency.

• Diesel Engine in typical highway service: somewhat better the gasoline engine.

• Spark Engine operated at optimum conditions – modest rpm and wide throttle opening: 30-40%

• Average Steam-Electric Generating Station: 32-33%

• Range for Fossil-Fired Steam-Electric Generating Stations: 25-45%

• Nuclear-Fired Steam-Electric Generating Station: 29-33%

• Combined Cycle Combustion Turbine Electric Generating Station: 50-60%

• Combustion Cycle Combustion Turbine with Solid Fuel Gasifier: 35-45%

• Comined Heat and Power (Co-gen): 70-90%