15.1: Introduction
‘Electrification’ was selected by the US National Academy of Engineering as the greatest engineering achievement of the twentieth century (NAE 2008). Electricity is a primary power source throughout the developed world and many other infrastructure systems depend upon electricity such as buildings and telecommunications.
Figure 15.1.1 shows the historical sources of energy consumption in the United States. Until the twentieth century, wood was a predominant source of energy, with the early twentieth century seeing the growth in coal use. By 1920, petroleum and national gas became large sources of energy. Nuclear power began in 1950 with the development of the atomic industry.
The electricity system was created in the late nineteenth century in the United States for the primary purpose of lighting. Thomas Edison built and promoted a direct current network, while George Westinghouse proposed an alternating current network. In 1881, electricity rates were $ 0.24/kWh (equivalent to roughly $ 5/kWhr in current dollars), while modern electricity rates are around $ 0.10/kWh. Alternating current power grids have become the norm for reasons of efficiency throughout the world, although local direct current wiring can be used for light-emitting diode (LED) lighting and electronics.
US electricity energy flows for 2007 are shown in Figure 15.1.2. Coal, natural gas and nuclear power are the predominant primary energy sources, with renewable energy – including hydroelectric and wind power- fourth in magnitude. Other sources are relatively minor. Conversion losses of primary energy sources to electricity are substantial; moreover, this graphic does not include energy costs of mining, refining and transporting the primary energy sources to power generation sites. Predominant electricity uses are classified by EIA as residential, commercial or industrial.
World primary energy sources for electricity are similar to the US, with coal, natural gas, renewable sources and nuclear energy the primary sources (Figure 15.1.3), although hydroelectric is larger for the world than for the US itself. However, this distribution can vary substantially from region to region. Some countries have developed extensive and inexpensive geo-electric and hydro-electric power generation (such as Iceland), while others emphasize nuclear power generation (such as France.) Qatar is an example of a country dependent upon natural gas and oil sources.
Electricity is an intermediate carrier of energy, with a variety of underlying sources. Figure 15.1.4 illustrates overall US energy use and sources, with petroleum used primarily for transportation and heating.