Energy and Power

Energy is a measure of the ability to move things ("do work") or to supply heat, sound, electromagnetic radiation (e.g., light, X-rays), or bind atoms and molecules together.   Power is the average amount of energy expended per unit of time:   Running a hundred yards in 20 seconds expends an amount of energy in the runner.   Running that distance in 10 seconds uses the same amount of energy, but uses twice as much power as running it in 20 seconds.   In this case, the energy is the same, but the power is different.   Improvements in energy and power generation are great enhancers of living standards because they save human effort in every production process in a long production chain and many industries, thus multiplying the cost savings and price reductions of consumer goods and services throughout an economy and, by means of international trade, throughout the world.

There are many energy forms:   (1) mechanical, (2) gravitational, (3) electrical, (4) electromagnetic ("EM" or solar, including light), (5) chemical, (6) sound, (7), thermal (heat), and (8) nuclear (atomic).   Energy forms can also be subdivided into 2 groups: potential (positional, stationary) and kinetic (motion, non-positional).   Energy can be converted from one form to another, which is vital to life, work, and living standards:   Water at the top of a waterfall has gravitational potential energy.   As it falls, it loses gravitational energy and gains mechanical kinetic energy by its motion.   When it strikes the bottom of the waterfall, it has lost all its gravitational energy (but only at that particular location) and gained mechanical kinetic energy and heat (due to turbulence, i.e., random motion of the water particles).   The nuclear reactions occurring in the sun are transformed into electromagnetic energy (EM, solar radiation) that reaches the earth, making life possible.   EM energy is transformed into chemical energy on earth, such as plant food through photosynthesis, electrical, such as battery storage, etc.   A compass transforms potential magnetic energy into mechanical kinetic energy as the compass needle moves.   The potential chemical energy stored as molecular bonds in gasoline is combined with electrical energy of a spark to break the gasoline bonds that are transformed to mechanical kinetic energy and heat in a gasoline engine.   Chemical and EM energy are transformed in photochemistry, where chemical reactions absorb or emit light.   The mechanical kinetic energy of the piston is transformed into other mechanical energy in the crankshaft, transmission, and wheels to make the car move.   Some of the mechanical energy is lost to friction, i.e., heat, and dissipated throughout the vehicle and atmosphere.   An airplane in flight at a high speed compresses air to produce a "shock wave" that produces sound energy that produces a chemical reaction in an animal ear that produces electrical energy in connecting nerves and a chemical reaction in the brain.   Wind is moving air and therefore has kinetic energy that was caused by the kinetic energy of a moving earth and heat produced by EM from the sun.   The energy in the wind causes a sailing ship to move; that is, the ship acquired kinetic energy.   Heat in the earth (geothermal) causes the motion (kinetic energy) of geysers and volcanic eruptions.   Food is potential chemical energy that is transformed in plants and animals into other forms of chemical energy that is transformed into growth, metabolism and motion (kinetic energies).   Energy is useful or useless, depending on human wants and needs.   It is necessary for life, but causes environmental degradation.   The heat produced by friction is normally useless, but the traction caused by friction enables animals to move, and that is useful.   Friction can even do useful work (force x displacement in the same direction), as when box on a truck accelerates with the truck as it begins to move and gains speed.   Energy and power, good and bad, are everywhere!

A fuel is material with chemical energy that can be converted into motion, heat, sound, or light.   Fuels can be solids (coal, coke, wood, charcoal, uranium), liquids (biomass, kerosene, gasoline), or gases (hydrogen).   The chemical energy of fuels converts water into steam in a boiler to drive steam engines and turbines, burns gasoline to drive gasoline engines and turbines, converts uranium into heat in nuclear reactors to make steam to drive turbines that drive electric generators that produce electricity, etc.   Most fuels burn (oxidize), but uranium used in atomic reactors releases energy by fission, the release of heat and radiation when a radioactive material disintegrates from one element to another.   In animals, fuels are called food, which supplies energy to organism cells.   Coal and petroleum, and natural gas are known as fossil fuels, which are hydrocarbons formed from the fossilized remains of dead plants and animals.

There are many measures of energy and power, each developed in association with different industries:   The international standard (SI) definition of the joule (newton-meter) is the energy expended when a force of one newton is applied over a displacement of one meter in the direction of the force.   Other measures of energy are the calorie and Calorie.   1 Calorie = 1 kilocalorie = 1000 calories.   Currently, the SI definition of the calorie is 1 calorie (c) = 4.187 joules (J), so 1 Calorie (C) = 4187 joules (J).   An older definition of the calorie is the amount of energy in the form of heat required to raise 1 gram of water 1°C between 14.5°C and 15.5°C at atmospheric pressure.   Nutritionists and food labels use the Calorie (not calorie). The energy (heat content) of fuels is often measured in the British Thermal Unit (BTU).   1 BTU = 778.2 ft-lbs = 1055 J.

The watt (w) is the international standard (SI) for power, the amount of energy per unit of time.   The kilowatt and horsepower are also common measures of power.   1 watt = 1 joule / second. (Home night lights are 4 to 7 w, reading lights are 50 to 150 w.)   1 kw = 1000 w = 1000 joules / sec.   Another old measure of power, still in use to rate engines, is the horsepower (hp), where 1 hp = 745.7 watts.   Also, 1 hp = 33,000 foot-pounds of work per minute, which is the definition originated by James Watt to compare the power of his new steam engine to a horse.   Converting power units to energy units is accomplished by multiplying power units by time units: 1 joule = 1 watt-second, a very small amount of energy.   A more common energy unit is the kilowatt-hour (kwh), the measure on house meters: 1 kwh = 3,600,000 watt-seconds.