Units of Energy

In the scientific world, the joule (symbol J) is the unit of energy. It is not frequently used outside of the scientific community in the United States, but it is in other countries. In the United States, for example, the energy content of a food product is most frequently stated in food calories. This energy can be represented in joules, as it is in many places of the world. In Australia, a Diet Coca Cola is labelled Low Joule rather than Low Cal, as it is in the United States. 

Measurement of Energy

Scientists have examined energy and power in a variety of ways over the years. As a result, each sort of energy – electrical, mechanical, chemical, thermal, and nuclear – developed its own measurement method, and almost every energy relevant sector evolved its own vocabulary- for example, car salespeople when discussing horsepower. Tons and BTUs are installed by HVAC contractors. Kilowatt-hours are delivered by electric utilities. Newtons and joules are terms used by scientists.

The International System of Units (SI) was established from the metric system in 1960 to offer a uniform language for all physical entities. The SI is based on seven base units, from which all other physical values may be calculated. A newton (derived unit of force), for example, is stated as 1 kilogram (base unit of mass) accelerated at one metre (base unit of length) per second (base unit of time) squared. We also have some multiples and fractions of units. A megawatt (MW), for example, is one million (106) watts; a milliwatt (mW) is one-thousandth (10-3) of a watt.

Although the energy industry is beginning to utilise SI language, conventional terminologies continue to predominate. Many automobile manufacturers now indicate engine power in kilowatts, but in parentheses following the horsepower rating: 187 hp (140 kW). Next a brief introduction to energy, power, and force, the following sections examine the units most typically employed in renewable energy applications.

Consider the following facts to get a sense of the magnitude of a joule:

• The sound energy in a whisper is approximately 0.01 joule.

• The kinetic energy of a 1,000-kilogram car travelling 25 metres per second (55 miles per hour) is approximately 300,000 joules.

• The energy from burning a barrel of oil is approximately 6,000,000 joules.

• The annual energy use in the United States is approximately 100 billion joules.

• The daily energy input to the Earth from the sun is approximately 10,000 billion joules.

More Energy Units

• 1 cal (IT) = 4.1868 J, 1 cal (th) = 4.184 J, thermochemical calorie 1 cal 15 = 4.1855 J, calories to heat from 14.5 °C to 15.5 °C

• 1 erg = 107 J, cgs = centimeter-gram-second electron volt 1 Eh 4.35975 1018 J, unit 1 eV 1.60218 1019 J Hartree, atomic energy unit 1 Btu = 1055.06 J, British thermal unit according to ISO, to heat 1 pound water from 63 to 64 degrees Fahrenheit.

• 1 tce = 29.3076 109 J, tonne of coal equivalent, 7000 kcal (IT).

• 1 toe Equals 41.868 109 J, tonne of oil equivalent, 10000 kcal (IT).

Large-scale units

It is standard practise to use large-scale units based on the joule, Btu, and kWh when addressing national or global energy budgets:

Exajoule (EJ):

1 EJ = 1018 J

Quadrillion Btu(quad):

1 quad = 1015 Btu = 1.055 EJ

Terawatt-year (TWyr):

1 TWyr = 8.76 x 1012 kWh = 31.54 EJ = 29.89 quad

Other basic units of energy

• Calorie

• Horsepower

• Joule (J) 

• kWh (kilowatt-hour) (kWh)

• Kilowatt (kW)

• One million Joules is one megajoule (MJ).

• Electricity unit

• Voltaic (V)

• Wattage (Electric)

• Watt (Thermal) 

• Watt-hour (Wh)

Conclusion 

Simply explained, energy is the ability to accomplish labour (W), which includes anything from moving a car to heating a home to illuminating a room. Many types of labour include the transformation of energy. Electrical energy is converted into heat and light energy by a light bulb. Chemical energy is converted into heat and mechanical energy by an internal-combustion engine. A dynamo is a machine that converts mechanical energy into heat and electrical energy.