Where Does Electricity Come From?
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Bernard Nebel.
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Nearly all the electricity that we use in homes, schools, businesses, industry, etc. comes from turning generators, i.e., rotating a coil of wire within a magnetic field. This would seem to be a simple task. Unfortunately, the energy required to turn a generator exceeds the electrical energy produced. If at all possible, have students experience this for themselves using a small hand-crank generator: https://www.youtube.com/watch?v=JwuO9XrH_aI
The bulk of electrical power used in the US is produced via turbo-generators, i.e., turbines connected directly to a generator as seen in the following video: https://www.youtube.com/watch?v=p1iv-eI0UnE
Turbines are driven by:
High pressure stem produced by boiling water heated by burning:
Coal (see: coal fired power plants images)
Municipal solid waste (see: waste to energy power plants images)
or produced via heat from
nuclear power (see: nuclear power plant cutaway diagram)
solar thermal (see: solar thermal power plant images)
geothermal heat (see: geothermal power plant images)
Direct exhaust from burning natural gas or oil
FlowingWater (see: hydroelectric dams images)
Wind (see: wind turbines images)
The proportion of electrical power produced from each source are given in the table below (Note that nearly two thirds of our (US) electrical power currently comes from burning fossil fuels, i.e., coal, natural gas, and oil.
The one source of electrical power that does not involve turning a generator is the photovoltaic cell (solar cells). (See the following section)
U.S. electricity generation by source, amount, and share of total in 20181 Energy source Billion kWh Share of total Total – all sources 4,171 Fossil fuels (total) 2,653 63.6% Natural gas 1,469 (gas turbo-gen) 35.2% Coal 1,146 (steam turbo-g) 27.5% Petroleum (total) 25 0.6% Petroleum liquids 16 0.4% Petroleum coke 9 0.2% Other gases 13 0.3% Nuclear 807 steam turbo-gen 19.4% Renewables (total) 703 16.9% Hydropower 293 water turbo-gen) 7.0% Wind 273 wind turbo-gen 6.5% Biomass (total) 58 steam turbo-gen) 1.4% Wood 41 1.0% Landfill gas 11 0.3% Municipal solid waste (biogenic) 7 0.2% Other biomass waste -1 <0.1% Solar (total) 64 1.5% Photovoltaic 60 1.4% Solar thermal 4 steam turbo-gen 0.1% Geothermal 16 steam turbo-gen 0.4% Pumped storage hydropower3 -6 -0.1% Other sources 13 0.3% (The above table is from: https://www.eia.gov/tools/faqs/faq.php?id=427&t=3)
Engage students in a discussion of the advantages and disadvantages of each power source. (See the text.)
Please post questions and/or comments.
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