Measuring energy

1. Terminology    

  • Kilo – thousand(103) ;    Mega – million(106) ;     Giga – billion 10;  
  • Tera – Trillion (1012);    Peta- Thousand-billion   (1015);    Exa – Quintillion  (1018)           
  • See:  http://en.wikipedia.org/wiki/Order_of_magnitude

2. Energy      

2.1 Watt   (W) =  1 joule per second 

  • Kilowatt –   One thousand (103) watts   / as in kilowatt hours   kWh 
    • Ex: In 2012, the average annual electricity consumption for a U.S. residential utility customer was 10,837 kWh, an average of 903 kilowatt hours (kWh) per month. Louisiana had the highest annual consumption at 15,046 kWh and Maine the lowest at 6,367 kWh per month.    
    • Ex: Rooftop PV systems on residential buildings typically feature a capacity of about 5 to 20 kW installed capacity.   
  • Megawatt —  One million (106) watts 
  • Ex: Massive energy projects such as Indonesia’s 5 GW coal fired power plant, or Georgia’s  Vogel twin nuclear reactors at 4GW.   
  • Ex:  Large offshore wind turbine = 7 megawatts    
  • Ex:  Large coal plant = 1,000 megawatts (1 gigawatt)   
  • Gigawatt — One  billion watts  (109)   

2.2  Joule  (J) =  1 watt second

(force) One Newton per meter;   (electrical)

One ampere through a resistance of one ohm for one second.  http://en.wikipedia.org/wiki/Joule   

  • Kilojoule (kJ) is equal to one thousand (103) joules. One kilojoule per second (1 kilowatt) is approximately the amount of solar radiation received by one square metre of the Earth in full daylight.[10] 
  • Megajoule (MJ) is  one million (106) joules,  kinetic energy of a one ton vehicle moving at 160 km/h. 
  • Gigajoule (GJ) is equal to one billion (109) joules.
  • Exajoule  (EJ) is equal to one quintillion (1018) joules.   Energy in the United States used per year is roughly 94 EJ.
  • Zettajoule (ZJ) is equal to one sextillion (1021) joules. Annual global energy consumption is approximately 0.5 ZJ.
  • Yottajoule (YJ) is equal to one septillion (1024) joules. This is approximately the amount of energy required to heat the entire volume of water on Earth by 1 °C.

Ex:  The thermal output of the Sun is approximately 400 YJ per second.       

2.3 Power    (Oak Ridge data) 

  • 1.0 watt = 1.0 joule/second = 3.413 Btu/hr
  • 1.0 kilowatt (kW) = 3413 Btu/hr = 1.341 horsepower
  • 1.0 kilowatt-hour (kWh) = 3.6 MJ = 3413 Btu
  • 1.0 horsepower (hp) = 550 foot-pounds per second = 2545 Btu per hour = 745.7 watts = 0.746 kW

2.4 British Thermal Unit (BTU)   — 1 BTU = 1055 joules   — Energy  to heat one pound of water by one degree F.

  • Ex: One BTU is about the amount of energy in a wooden match.

3. Measuring oil and oil equivalents         555http://www.eia.gov/cfapps/ipdbproject/docs/unitswithpetro.cfm       

  • Barrel of oil is 42 gallons, 158 liters  (6 GJ)    
  • Metric ton of oil  = 39 mbtu, 41.8 GJ   / So about 8 barrels of oil is a metric ton           
  • Gallon of gasoline is 3.785 liters.   120 MJ,   120,000 BTUs  (hhv)     
  • Gallon of alternative fuel  / ethanol 84,500 BTUs,  methanol 65,200  BTUs  (hhv)    http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf     
  • Octane – gasoline 84,  Ethanol 110, Methanol 112    (Note that gasoline has more BTUs,  but ethanol and methanol have higher octane).       

4 More links   

Oak Ridge   https://bioenergy.ornl.gov/papers/misc/energy_conv.html