Power plants (power stations)
by Chris Woodford. Last updated: September 25, 2015.
When Thomas Alva Edison (1847–1931)
constructed one of the first
power stations in Pearl Street, New York City, in 1882, he
revolutionized the way people used energy.
Once energy had to be
produced where and when it was needed. But a power station separates
the producer of energy from the consumer, using electricity as a
go-between. This makes it possible to generate electricity in Detroit
that will be used in California or to use cheap energy produced at
quiet periods during the night to produce electricity for peak periods
during the day. How do power plants actually work? Let's take a closer look!
Photo: A typical coal-fired power plant. Photo by Warren Gretz courtesy of US DOE/NREL (US Department of Energy/National Renewable Energy Laboratory).
How does energy get from a power plant to your home?
A power station is really a machine that extracts energy from a fuel. Some power stations burn fossil fuels such as coal,
oil, or gas. Nuclear power stations
produce energy by splitting apart atoms of heavy materials such as uranium and plutonium.
The heat produced is used to convert water into steam at high pressure. This steam
turns a windmill-like device called a turbine connected to an
electricity generator. Extracting heat from a fuel takes place over a
number of stages and some energy is wasted at each stage. That means power plants are not
very efficient: in a typical plant running on coal, oil, or gas, only about 30–40 percent of the energy locked
inside the fuel is converted to electricity and the rest is wasted.
- Fuel: The energy that finds its way
into your TV,
toaster starts off as fuel loaded into a power plant. Some
power plants run on coal, while others use oil, natural gas, or methane
gas from decomposing rubbish.
- Furnace: The fuel is burned in a giant
furnace to release
- Boiler: In the boiler, heat from the
furnace flows around
pipes full of cold water. The heat boils the water and turns it into
- Turbine: The steam flows at
high-pressure around a wheel that's a bit like a windmill made of tightly packed metal blades. The
blades start turning as the steam flows past. Known as a steam turbine, this
device is designed to convert the steam's energy into kinetic energy
(the energy of something moving). For the turbine to work efficiently, heat must enter it at
a really high temperature and pressure and leave at as low a temperature and pressure as possible.
- Cooling tower: The giant, jug-shaped cooling towers
you see at old power plants make the turbine more efficient. Boiling hot water from the
steam turbine is cooled in a heat exchanger called a condenser.
Then it's sprayed into the giant cooling towers and pumped back for reuse. Most of the
water condenses on the walls of the towers and drips back down again. Only a small
amount of the water used escapes as steam from the towers themselves, but
huge amounts of heat and energy are lost.
- Generator: The turbine is linked by an
axle to a
generator, so the generator spins around with the turbine blades. As it
spins, the generator uses the kinetic energy from the turbine to make
- Electricity cables: The electricity
travels out of the
generator to a transformer nearby.
- Step-up transformer:
Electricity loses some of its energy as it travels down wire cables, but high-voltage electricity loses less
energy than low-voltage electricity. So the electricity generated in
the plant is stepped-up (boosted) to a very high voltage as it leaves
the power plant.
- Pylons: Hugh metal towers carry
electricity at extremely
high voltages, along overhead cables, to wherever it is needed.
- Step-down transformer: Once the
electricity reaches its
destination, another transformer converts the electricity back to a
lower voltage safe for homes to use.
- Homes: Electricity flows into homes
- Appliances: Electricity flows all round
your home to
outlets on the wall. When you plug in a television or other appliance,
it could be making a very indirect connection to a piece of coal
hundreds of miles away!
Photo: Left: Power station transformers. Right: Transmission line (pylons).
Both photos courtesy of US Department of Energy.
NEVER mess with the power of electricity!
Electricity is the most exciting form of energy we've discovered so far.
It's fascinating and amazingly useful—but (as a bolt of lightning
readily shows) it can also be incredibly dangerous.
When electricity buzzes out of a power plant, it's being transmitted
by voltages that are thousands of times higher than the ones you'll find
in your home—and hundreds of thousands of times higher than the ones you'll
find in a flashlight. It is amazingly dangerous!
Don't be crazy! Don't be a fool! Don't touch power-plant equipment!
You will almost certainly die the most agonizing and unpleasant death
you can possibly imagine. If you're extremely lucky, you might be instantly zapped to death.
More likely, though, you'll be cooked and sizzled to death in a very slow and horribly painful way.
You won't enjoy it, believe me. And it's not a cool story you'll be able to share with your friends.
If you don't want to end up like a char-grilled steak,
be sure to follow warning signs like this one and stay well away. Don't ever fly a kite near
power lines and if you do happen to lose a football or something like that near
a power generator or an electricity substation, just leave it there; your life is worth more than
a silly bit of plastic.
Making power the modern way
A typical, old-fashioned coal power station is only about 35 percent
efficient (it wastes about two thirds of the energy in each lump of coal), but new
designs such as combined cycle power stations may be up to 50 percent
efficient. Unlike in a traditional power station, hot exhaust gases
produced in a combined cycle power station are not allowed to escape
and waste energy, Instead, they are used to produce steam and drive a
second turbine and generator. This design is up to 15 percent more
efficient than a traditional power station. Combined heat and power
(cogeneration) plants are another improved design, in which waste energy is used to heat hot water.
Generating electricity does not always mean burning fuel. In a
hydroelectric power station, the energy of rushing water is directed at
a large vaned water turbine connected to an electricity generator. The
water may be released from a large dammed reservoir to satisfy peak
electricity demand during the daytime and pumped back up into the
reservoir when electricity is cheaper at night. This is known as pumped
storage. Hydroelectric power stations make renewable energy:
they're more environmentally friendly because they don't use up Earth's limited supplies of fossil fuels, and
(in theory) we could use them forever without damaging the planet. The trouble is, the huge dams
that hydroelectric power plants need are usually very destructive to build. The Three Gorges hydroelectric dam on the Yangtze river in China, which took almost a decade to build from 1994 to 2012, has displaced around 1.2 million people from their homes. Other hydroelectric projects have caused major damage to rivers.
Photo: Ice Harbor hydroelectric dam produces electricity when water rushes through
its turbines. Photo by US Army Corps of Engineers courtesy of US DOE/NREL (US Department of Energy/National Renewable Energy Laboratory).
Chart: Large, centralized fossil-fueled power plants are very inefficient, wasting about two thirds of the energy in the fuel. About 62 percent is lost in the plant itself as waste heat. A further 4 percent disappears in the power lines and transformers that carry electricity from a power plant to your home. Once the electricity has arrived, your home appliances waste a further 13 percent. All told, only 22 percent of the original energy in the fuel (green slice) turns into energy you can actually use. Source: Figures from "Decentralizing Power: An Energy Revolution for the 21st Century," Greenpeace, 2005.
The generation game
An electric motor turns electrical energy
making a dense coil of iron wire spin around between the poles of a
magnet. An electric generator works in
exactly the opposite
Back in 1831, British chemist Michael Faraday
(1791–1867) found that when he rotated a copper disc between the poles of a magnet an electric
current was produced. Electric generators, from the tiny dynamos on
bicycle lamps to the massive machines producing electricity for entire
cities, still work in exactly the same way today.
When a loop of metal rotates in the magnetic field produced by a
magnet, an electric current is induced (generated) in the metal. If the
coil is connected by terminals to a load, such as a flashlight bulb,
the current will flow through the lamp and make it light up. The amount
of current produced depends on how big the coil is, how strong the
magnets are, and how fast the coil is turned.
Read more in our article on generators.
Photo: An excellent cutaway model of a steam turbine and electricity generator. Steam flows into the turbine through the huge gray pipes at the top, turning the windmill-like turbine in the middle. As the turbine spins, it turns the electricity generator connected to it (the blue cylinder you can just see on the right). This model lives in Think Tank, the science and engineering museum in Birmingham, England.
Charts: The changing nature of power plants. These two charts break down the total population of US electric power industry power plants by the type of fuel or other energy that they use for 2003 and 2013. Fossil fueled plants are shown in blue, nuclear plants in orange, renewable plants in green, and other power plants in yellow. You can see that there has been a slight reduction in coal and petroleum plants, a slight increase in natural gas plants, and a huge increase in renewables (though hydro plants remain about the same). Drawn using data from
How many and what kind of power plants are there in the United States?, US Energy Information Administration, April 2, 2015. Please be aware that the scale on the two charts is different.
Find out more
On this website
Tours of power plants
- How do you make electricity from coal: A great 10-minute animation from FirstEnergy and EDP Video explains the various stages in energy production and has lots of interesting facts and statistics. There's a good explanation of how cooling towers work and why power plants now use smokestack scrubbers to reduce air pollution.
- MidAmerican Energy Coal-Fueled Power Plant Virtual Tour: A simple, 7-minute tour that clearly explains the journey from coal to electricity. Great for young students.
- Duke Energy Power Plant Tour: Unlike the two very simplified animations above, this is an actual video and photo tour of a real gas power plant (the Duke Energy plant in Fayette, Masontown, Pennsylvania), taking in the control room, the cooling towers, the steam turbines, generators, and transmission yard.
Other useful videos
- Power Lines by Alom Shaha, National STEM Centre. In this short video, Alom demonstrates why power plants transmit electricity at high voltages.
- BBC News: How water helps light our homes: Steve Waygood of the Npower company explains how water plays a crucial role in electricity generation at power plants, using the UK's Didcot Power Station as an example.
Books I've written
If you liked this article, you might like some of the children's books I've written on similar topics:
- Energy by Chris Woodford.
New York/London, England: Dorling Kindersley, 2007: A very bright and colorful book about energy in our lives—what it is, where it comes from, and how we use it in different ways. Ages 9–12.
- Power and Energy by Chris Woodford.
New York: Facts on File, 2004. This is a more detailed, 96-page book about how humans have used energy throughout history. Suitable for most ages from about 10+.
- Cool Science: Experiments with Electricity and Magnetism by Chris Woodford. New York: Gareth Stevens, 2010: Learn about electricity by doing simple, safe experiments! Ages 9–12.
- Routes of Science: Electricity by Chris Woodford. New York: Facts on File, 2004: This is the simple story of how humans discovered electricity in ancient times and gradually learned to harness it for their everyday needs. Ages 9–12.
If you liked this article...
You might like my new book, Atoms Under the Floorboards: The Surprising Science Hidden in Your Home, published worldwide by Bloomsbury.
More to explore on our website...