Appendix 1 - Reidar Conradi (Ed.): Some Common Energy Terms - per Oct. 27, 2007

Introduction: first, we define some basic units to measure general properties of any energy carrier or source (like fuel and electricity). Then come a few more specific units for specific energy sources, like nuclear energy and oil. The International System of Units (SI) is used whenever appropriate, e.g. joule == Ws for energy. Ultimately, the SI units are based on three core ones - meter (length), kilogram (mass), and second (time).

List of energy units:

• Calorie ("cal", cal-15th_degree) == amount of thermic energy required to heat 1 gram of air-free water from 14.5 to 15.5 degrees C at a constant atmospheric pressure of 1 bar.
  Nowadays, 1 cal-intl =~= 4.1868 joule (SI unit).
  NB: cal means implicitly "kilo"cal, when applied to food and fysiology.

• Btu ("British Thermal Unit") == amount of thermic energy required to heat one pound (BP =~= 0.454 kg) of air-free water from 39 to 40 degrees F (Fahrenheit) at a constant atmospheric pressure of 1 bar.
  Digression: We would expect that one Btu becomes: 454 * 5 / 9 cal = 252.2222 cal, vs. the actual value of 251.9967 cal, or less than 0.1 % off.
  Nowadays, 1 Btu-intl =~= 1055.06 joule (SI unit).
• Therm-UK (pronounced "thm") == 100 000 Btu (aggregated unit).

• Cubic Foot ("CF") == amount of thermic energy released by burning such a volume (not mass!) of average natural gas =~= 1020 Btu.
• Cento Cubic Feet ("CCF" or "100 CF") =~= 102 000 Btu.
  Therm-US == heat energy released by burning one CCF of nat'l gas =~= 102 000 Btu,
  i.e. 2 % more than a Therm-UK.

• In SU-units then, a Therm-UK =~= 100*1000 * 1055 joule ==
  105.5 mill. joule (=Ws) == (105 500 K W) / (3600) h == 29.31 kWh; or inversely:
  1 kWh = 3 600 000 J / (1055.06 J/Btu) = 3412 Btu.
  1 kWh = 3 600 000 J / (4.1868 J/cal) = 852 000 cal = 852 kcal.
  1 cal =~= 0.00396831 Btu; 1 Btu =~= 252 cal.
  1 joule = 0.252 cal; 1 joule = 0.00094281 Btu (or 1 kJ = 0.94281 Btu).

  E = m * c**2 => 30 tWh/kg.
  Electron Volt = ca. 10**(-19) joule.

• Volume of a CF == (0.3048m)**3 == 0.02832 m3 == 28.32 liter.
• Volume of a CCF == 100 that of the CF == 2832 liter.
• The average mass (i.e. "weight") of a corresponding CCF energy carrier, here natural gas, is calculated from its constituents, typically:
  75 % methane (w/ specific weight 0.717 kg/m3),
  15 % ethane (1.28),
  5 % propane/butane etc. (ca. 1.5),
  5 % other gases such as CO2, H2O, sulfor etc. (ca. 1.3).
  We shall assume an average specific weight of 0.8 kg/m3, cf. air weighing 1.3 kg/m3.
• The volume of a therm-US or CCF == 2832 liter, and weighing 2.832 m3 * (0.8 kg/m3) == 2.0xx kg.
• Energy per volume or weight: Burning an average CCF gives a thermic energy of 29.31 kWh,
  i.e. 10.8?? kWh/m3 or 13.5 kWh/kg.
• 25 000 therm/day is an effect unit much used in UK = 30 538 KW.