During the early days of the Industrial Revolution, most industries powered their grain mills and other mechanical contraptions directly, using wind mills and water wheels. With the invention of the coal-powered steam engine in the late 1700s, factories could be located anywhere fuel was available, whether or not a wind or water power source was nearby. By the end of the 1800s, scientists had learned how to transform the mechanical energy of these steam engines into electricity.

Electricity, which is the flow of electrons through materials known as conductors, is one of the most useful forms of energy, in part because it can be transmitted over long distances from a source of production to users (Figure 9.11). Today, when you cook a meal in your microwave or charge your laptop, it’s easy to forget the long path that the electricity may have taken to reach you.

A device capable of producing electricity, commonly called a generator, includes two basic components: a magnet and a conductor (Figure 9.12). The magnetic component of a generator creates a magnetic field. The movement of a conductor, generally rotating copper wire, through the generator’s magnetic field induces a flow of electrons in the conductor. That flow of electrons can be harnessed to do work ranging from lighting a room to running an electric car. However, we need to remember that it takes energy to move the conductor and generate a flow of electrons. Globally, fossil fuels are the source of approximately two-thirds of electrical generation (Figure 9.13).

Generating electricity is as easy as boiling a pot of water. OK, it’s not that easy—but any fuel source that can heat water enough to turn it into steam may be used to generate electricity. Currently, the most common source of this heat is the burning of fuels, especially coal and natural gas.

Let’s take a look at the workings of a typical coal-fired power plant (Figure 9.14). Coal is first pulverized into tiny pieces so it burns more completely. The heat of combustion is used to boil water, which produces steam. The steam creates pressure that turns a turbine attached to an electrical generator. After passing through the turbine, the steam is cooled, condenses back to liquid water, and returns to the boiler, where it is heated to form steam once again. The electricity produced can then flow through the power grid and into homes and businesses.

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Each step in the process results in a loss of usable energy. On average, about 35% of the energy content of coal or other combustible fuel is converted into electrical energy. The remainder is lost to the environment as heat (see Figure 2.17, page 47).

Electrical energy can be generated using other combustible fuels, including natural gas, oil, and biomass, in the form of wood or agricultural wastes. Although the physical nature of these materials requires different handling, the principle of their use is the same as in coal-fired power plants: The chemical energy released during burning is used to produce steam that turns a turbine.

With the increased availability of petroleum in the late 1800s, it became possible to develop a more compact engine that didn’t require a separate steam chamber and furnace. In an internal combustion engine, combustion directly drives a set of pistons or turbines hooked up to a crank arm. Most internal combustion engines are used in vehicles, such as automobiles, diesel-powered trains, jet airplanes and boats. They are also used in power tools such as lawnmowers, leaf blowers, and chainsaws, as well as for portable diesel and gasoline power generators.

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Combined cycle power plants combine a type of internal combustion engine known as a gas turbine engine with a steam power plant. When operated on its own, a gas turbine engine burns natural gas, sending a hot, high-pressure stream of gas through a turbine connected to an electrical generator. A combined cycle power plant takes advantage of the potentially wasted heat of combustion to boil water and spin an independent steam turbine. Combined cycle power plants can increase the efficiency of power generation from 35% to 60%.