How Electricity is Generated
How coal, water, wind, uranium, and solar power is turned into power
Everything seems so simple these days. If we’re curious about peanuts, we have the ability to press a couple buttons and boom! In seconds we have access to everything we could ever want to know about peanuts. Sometimes we take for granted everything that had to happen in order to power the devices we love. This article will let you know what we get electricity from and how it is converted into the electricity that will eventually reach your home. It’s amazing to think these resources actually turn into the thing that powers the things we use everyday.
The most common resource we get our electricity from is coal, but you probably already knew that. The process of extracting electric power from the energy (carbon) stored in coal is multi-step one, carried out by burning the coal. Here is the exact technique used to get the coal into a usable form:
- First a crushing machine called a pulverizer grinds the coal into a fine powder. The coal powder mixed with hot air helps it burn more efficiently.
- Primary air fans blow the mixture through coal pipes into the furnace.
- The burning hot coals heat water that is a huge boiler, creating steam.
- Steam from the boiler spins the blades of a turbine. (This transforms heat energy from the burning coal into mechanical energy which spins the turbine).
- That spinning turbine is used to power a generator (a machine that turns mechanical energy into electrical energy). This energy is converted when magnets spin inside a copper coil in the generator.
- Next, a condenser cools the steam after it exits the turbine. As the steam is condensed, it turns back into water.
- That water is pumped back into the boiler, and the cycle begins again.
- FInally the electricity generated can be sent to through the transmission system and begin its journey to your home.
Note: The basic process of converting coal to electricity has not changed in 60 years but the United States’s advancements in the technology for removing emissions have led to cleaner coal.
Natural gas is another big supplier of power for our homes. While it is is much more complicated to harness, it requires very little processing to be usable. It is high in heating value, or BTU content, and has few impurities as compared to some other fossil fuels, so you can see why it’s advantageous. Here are the steps to producing power with natural gas:
- Exploration – Natural gas is found underground in deposits. Over the span of 2-10 years geologists and geophysicists use of technology to make educated guesses as to the location of these deposits. The geologists usually begin by geological surveys at the top of the earth’s surface, looking for characteristics of natural gas deposits on the ground. They use seismographs (similar to the ones used to record earthquake fluctuations), magnetometers (to record magnetic properties) and gravimeters (to measure gravitational fields) to explore the composition of the earth below.
- If these tests show that the land is favorable for natural gas deposits, exploratory wells are dug allowing geologists to see the underground characteristics and confirm if deposits are present.
- Extraction – To extract from a site with a high probability of gas deposits drillers start a 3 week, 24 hour a day process of digging straight down, sometimes more than 20 thousand feet below the surface (still unsure if there will be a natural gas deposit). The drillers use 2 methods to drill down:
- percussion drilling – raising and dropping an extremely heavy metal bit into the ground, which creates a hole.
- rotary drilling – using a sharp, rotating bit to dig. (it looks and acts like a giant handheld drill) This is the most common way of drilling today.
- Finally, if natural gas is found a well is built. If it is not found, the the site becomes considered a “dry hole,” it gets cleaned up, and the process starts over again. Unfortunately between the years of 1995 and 2005, 60% of the wells drilled were deemed dry holes.
- If the site is not a dry hole, a conduit (a channel for conveying water or other fluid) is made. Since natural gas is lighter than air, the pressurized gas will rise to the surface with little or no interference.
- In some cases, drillers send an electric charge down into the well to break up the rock around it. Then a highly-pressurized liquid fracking solution, composed of over 99% of water and sand, is sent down the well further breaking up the rocks, and releasing the natural gas.
- Since the gas is lighter than the solution, it rises to the top of the well where it can easily be captured. Once it is successfully lifted out of the well, the gas travels through a network of pipelines to be treated and processed for use.
- Processing – The gas is then sent to processing plants where excess water, fluids, sulfur, carbon dioxide and hydrocarbons are removed, resulting in pure natural gas.
- Arrival to the Power Plant – The processed gas is brought to the power plant in a mainline transmission pipe. The pipe connects to the power plant’s gas yard where the gas it is filtered even more to remove impurities and excess moisture.
- The gas yards are also used to adjust the pressure to meet combustion turbine’s requirements. They do this by keeping the natural gas in a gaseous state. It can not be condensed into droplets of liquid. If does get condensed or turn into liquid, it could cause internal equipment damage. (One way to maintain the required gaseous state is by using gas heaters to ensure the natural gas remains above the dew point).
- Combustion Turbines/Generator – Once the natural gas is at the proper pressure and temperature, it travels to the combustion turbine (which is very similar to a jet engine). The natural gas is then combined with compressed air generated in the forward part of the engine, or the combustion chamber. The burning of the natural gas causes the blades of the turbine to spin. The turbine is connected to a generator using a shaft that causes the generator to spin, transforming mechanical energy into electrical energy by using magnets and copper wire to create an electrical charge.
- This power is then transferred to the power plant’s step-up transformer and switch yard before entering the transmission system.
Wind machines, or wind turbines, produce power using blades to collect the wind’s kinetic energy; a lot of us have seen wind turbines in pictures or have driven passed them before. Places with many wind turbines are called “wind farms.” As the wind blows, it flows over the blades creating lift, (just like the effect of airplane wings) which causes them to turn. The blades are connected to a drive shaft that turns an electric generator. This seems simple enough, but there are many drawbacks to using wind farms.
The major challenges of using wind as a power source is that the wind is that does not always blow when electricity is needed, wind energy cannot be stored, and not all winds can be harnessed to meet the timing of electricity demands. Also there are higher construction costs for offshore wind turbines and there is a risk of destruction from hurricane-force winds sometimes encountered on our southern coasts. Yet another problem is that large wind farms need to be in locations far removed from the populated areas where the energy is needed. Those kinds of places are not that easy to find on a large scale.
It’s weird, but water is actually one of the oldest ways of producing electricity. Hydropower has been around around for hundreds of years and is used widely in the United States. In fact in 2013, hydropower accounted for approximately 6% of total U.S. electricity generation and 52% of generation from all renewables. The total hydropower capacity in the U.S. is about 100,000 megawatts (MW), providing electricity to more than 28 million American homes. Additionally, in the U.S., hydropower is produced for an average of 7 cents per kilowatt-hour (kWh) in comparison to other renewable averages such as wind – 18 cents per kWh, solar – 13 cents per kWh and biomass – 10 cents per kWh.
- Dam – a dam holds back water, creating a large reservoir.
- Intake – the gates on the dam open and gravity pulls the water through the penstock (a pipeline that leads to the turbine). The water builds up pressure as it flows through this pipe.
- Turbine – water hits and turns the large blades of a turbine, which is attached to a generator above it by a shaft. Modern hydro turbines can convert as much as 90% of the available energy into electricity.
- Generators – as the turbine blades turn, so do a series of electromagnets on the rotating portion of the generator. The giant magnets rotate past copper coils, creating electricity. After the generators produce electricity, it is transferred to an electrical power substation and then transmitted to your home.
- Outflow – finally the used water is discharged from the turbine and is sometimes carried through pipelines (tailraces) and re-enters the river downstream. The water in the reservoir is considered stored energy. The level of the reservoir above the turbine is referred to as “head” and determines the amount of pressure and volume available to generate electricity. A greater amount of head means there is more available energy for electrical generation.
- When the gates are open, the water flowing through the penstock becomes kinetic energy because it’s in motion. The rotating turbine in turn drives the generator.
Although nuclear power is efficient, it’s another one of those energy sources that take many steps to get it into a usable form of energy for your home. This is an example of how uranium is converted into power for your home:
- Mining – miners search for uranium ore, a very good fuel for nuclear power production. Underground uranium mining has the same basic steps as coal mining. (see Coal section above on “Exploration” and “Extraction”)
- Milling – involves a sequence of physical and chemical treatments. The final product of milling creates yellowcake, named for its powdery texture and yellowish color.
- Conversion and Enrichment – the drums of yellowcake must go through another process to be transformed into a fuel that can be used by power plants. Natural uranium is composed of two types: U-235 and U-238. Only U-235 is capable of being used for energy production, but it only makes up less than 1% of natural uranium.
- To be turned into U-235, the U-238 must be enriched into a gaseous state. To do this the molecules are blown through thousands of filters or sieves, one after another. Because the lighter U-235 particles travel faster than the heavier U-238 particles, more of them penetrate each sieve. As more sieves are passed, the concentration of U-235 increases and the process continues until the concentration of U-235 is raised, or enriched, to 3-5%.
- Fuel Fabrication – enriched uranium fluoride ( a gas) is now changed to uranium dioxide (a solid). It is then pressed into ceramic pellets the size of the tip your little finger. The fuel pellets are inserted and stacked end to end into slender, heat-resistant metallic tubes, or fuel rods which can range in size from 12-17 feet tall. The fuel rods are then combined to form fuel bundles.
- Power Generation – when the fuel bundles are placed in the reactor, it is the process of the uranium atoms splitting as they are bombarded with free neutron (also known as fission) that creates energy which is given off as heat. That heat is sent to a Pressurized Water Reactor (PWR) where it heats water to 500°F but does not allow it to boil, much like a pressure cooker.
- Steam generators then take river water and run it against pipes that contain the PWR heated water to convert the river water into steam. The steam is then sent to turbines to begin the electricity power production process.
- The steam is then released through cooling towers.
- Disposal – most U.S. nuclear plants store waste either in on-site dry storage tank or a spent fuel pool. Since water is a natural radiation barrier, spent fuel is loaded into airtight steel, or concrete and steel containers (known as casks) and then carefully delivered to a steel-lined, concrete pool of water for storage.
- On-site dry storage is done in a similar matter, with the used fuel being placed into engineered concrete and steel casks that are set on a special pad. Each cask can weigh 300,000 pounds and is strong enough to take a hit from a fast moving truck or even a train without any damage.
Note: U.S. nuclear plants are well-designed and operated. They are also defended against attack and prepared in the event of an emergency. In addition to backup systems that monitor and regulate what goes on inside the reactor, U.S. nuclear power plants also use a series of physical barriers to prevent the escape of radioactive material. Everything from the fuel pellets to the fuel rods are encased in materials that limit radiation exposure. All of these items are further contained in a massive reinforced concrete structure (called the containment) with walls that are four feet thick. Also note that the lack of a containment structure is what helped lead to the failure of the Chernobyl plant in Russia. This tragedy is something that cannot happen in the United States since all plants are required to have these containment structures and other safety features.
Solar energy is converted to electricity by utilizing photovoltaic (PV) devices, or “solar cells.” The solar energy (heat) boils water; the steam drives a turbine; the turbine turns an ordinary generator, which then generates electric power.
Seems simple enough but the big problem with using solar energy as an electricity source is that solar photovoltaic panels create DC power – your home uses AC power. The price the converters is far too high because not enough companies support the production of solar electricity, mostly due to the fact that they have made money off of other power producers. As solar energy begins to receive more subsidies the price of the panels will drop and solar energy can become a more widely used source of electricity. In Florida, that will be a great thing. If you think it’s time for your home to be equipped with solar panels have our licensed electricians here at ProMag a call, and you can utilize the easiest way to get power into your home.