Where Does Electricity Come From?

[Bernard NebelKeymaster]

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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