Energy and  Energy Consumption

 Much of the energy that is used by people on Earth, especially in non-industrialized countries, is created or harnessed on a very local to individual level, from drying clothes in the sun to burning a small bundle of twigs to heat water.  Another large sector of energy production is the commercial or industrial sector, where energy is generated in centralized facilities and then transmitted or distributed for use.

 The United States consumes 25% of the world's commercial energy production, importing energy from around the globe.  Commercial energy sources are typically divided into non-renewable (on short human time scales) and renewable (in theory) sources.  Non-renewable energy is produced from burning "fossil" fuels (oil/petroleum and its byproducts, natural gas, coal, peat) and from nuclear fission.  Nuclear power at present is non-renewable because there is a finite (though large) supply of uranium-rich ore on Earth; nuclear fusion would be renewable.  Current (potentially) renewable sources of energy include biomass (particularly wood), hydropower (dominated by hydroelectric), geothermal, solar and wind.  Except for hydroelectric energy, renewable energy sources do not contribute much to commercial energy production in the United States.

 A minor though increasing source of energy comes from burning municipal and industrial waste, which is composed of all sorts of non-renewable and renewable materials, such as plastics, wood construction debris and carrot peelings.

 Energy production varies a lot from place to place in the United States.  Washington State produces a tremendous amount of hydroelectricity from the many dams on the Columbia, Snake and Skagit Rivers, and some energy from coal deposits, but has no oil or gas production and only one currently operating nuclear plant.  Washington was a net exporter of electricity up until the 1980's, and now is a net importer.  Wyoming has vast quantities of coal and several large coal-fired power plants, plus some producing oil wells, but no major hydroelectricity or nuclear power production.  Wyoming is the least densely populated state in the US, and therefore exports a tremendous amount of its energy.  California has several nuclear facilities and several large oil and gas fields, but has an enormous population, and imports much of its energy.

 Some consider energy conservation to be a source of energy; the "negawatt" approach to energy production.  Energy conservation can and has reduced or mitigated the need for more energy production in many instances.   From a social or economic viewpoint, one can conserve a "nuke's worth" of electricity.   But from a physical standpoint, conservation is not production.

 Energy consumption is typically organized by end-use sector.  Residential, municipal and/or commercial consumption of energy goes to heating, cooling, cooking, washing, lights and other appliances or devices.  Transportation, both individual and commercial/industrial, is a major energy consumer; automobiles, trains, planes, boats and other motorized vehicles consume mass quantities of high-end petroleum byproducts such as jet fuel, gasoline and diesel.  Manufacturing can be a major energy consumer.  For example, Washington State is home to many aluminum processing plants, despite the fact that unprocessed aluminum ore (bauxite, for example) must be imported via ship over great distances (the Caribbean, for example) and at large cost.  Washington has large quantities of relatively cheap, subsidized hydroelectric power, necessary to zap the stubborn aluminum oxides into aluminum metal.  Agriculture can also be a large energy user.

 Energy use is highly variable from place to place and  from time to time.  France generates a large percentage of its high quality energy (electricity) from nuclear fission, whereas some parts of Sweden burn peat to generate electricity (Sweden has a ban on nuclear power, few dams, and no other fossil fuels).  Energy consumption goes up in the winter in New York, and goes up in the summer in Florida.  Energy consumption is very high in the daytime and drops off dramatically at night; the cost of energy is often much lower after 11 p.m.

 Energy is measured in joules (metric), BTUs (British thermal units), calories or Calories (= 1000 calories), where .24 joules = 1 calorie = 252 BTU.  Power is energy per time, and is measured in watts (1 watt = 1 joule per second), kilowatts kW (= 1000 watts) or horsepower, where 1.341 kilowatts is one horsepower.  Recall also that a million watts is a megawatt and a billion watts is a gigawatt.

 The difference between power and energy  can be confusing to students.  Power is the rate of energy production or consumption.  A 1000 watt amplifier on a sound system uses 1000 joules of energy every second when operating at full capacity.  A gigawatt-capacity nuclear facility generates 1 billion joules of energy every second.  A million people simultaneously cranking their stereos up to the max will therefore use up the generating capacity of a single nuclear power plant.  Energy is the power used over a period of time.  Operating just one 1000 watt amplifier at maximum capacity for 24 hours uses 8,6400,000 joules of energy.

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