Energy Efficiency Terminology
Energy efficiency is similar to fuel efficiency but the input is usually in units of energy such as British thermal units (BTU), megajoules (MJ), gigajoules (GJ), kilocalories (kcal), or kilowatt-hours (kW·h). The inverse of "energy efficiency" is "energy intensity", or the amount of input energy required for a unit of output such as MJ/passenger-km (of passenger transport), BTU/ton-mile (of freight transport, for long/short/metric tons), GJ/t (for steel production), BTU/(kW·h) (for electricity generation), or litres/100 km (of vehicle travel). Litres per 100 km is also a measure of "energy intensity" where the input is measured by the amount of fuel and the output is measured by the distance travelled. For example: Fuel economy in automobiles.
Given a heat value of a fuel, it would be trivial to convert from fuel units (such as litres of gasoline) to energy units (such as MJ) and conversely. But there are two problems with comparisons made using energy units:
- There are two different heat values for any hydrogen-containing fuel which can differ by several percent (see below).
- When comparing transportation energy costs, it must be remembered that a kilowatt hour of electric energy may require an amount of fuel with heating value of 2 or 3 kilowatt hours to produce it.
Read more about this topic: Fuel Efficiency
Famous quotes containing the words energy and/or efficiency:
“Just as we need to encourage women to test lifes many options, we need to acknowledge real limits of energy and resources. It would be pointless and cruel to prescribe role combination for every woman at each moment of her life. Life has its seasons. There are moments when a woman ought to invest emotionally in many different roles, and other moments when she may need to conserve her psychological energies.”
—Faye J. Crosby (20th century)
“Never hug and kiss your children! Mother love may make your childrens infancy unhappy and prevent them from pursuing a career or getting married! Thats total hogwash, of course. But it shows on extreme example of what state-of-the-art scientific parenting was supposed to be in early twentieth-century America. After all, that was the heyday of efficiency experts, time-and-motion studies, and the like.”
—Lawrence Kutner (20th century)