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What is Energy?
Electricity
You probably know that in Ontario - hydro, nuclear power and coal plants generate most of the electricity we use. But how does the electricity get from a place like the Sir Adam Beck hydro-electric generators at Niagara Falls to your home many kilometres away?
How does power get to you?
The road that electricity travels to your home starts from the point it is produced by the power plant generator. The electricity produced at the power plant has a current in the range of 1,000’s of volts. However, in order to be transmitted long distances, electricity must have a voltage of 100,000’s of volts. This is necessary to overcome the losses that occur as the electricity travels along kilometres of power lines. This increase in voltage is done at the power plant by a Step-Up Transformer Station. The Step-Up Transformer converts the electricity to a current level in the range of 115,000 V – 500,000 V. The electricity is then transported across the province by high-voltage transmission lines. High-voltage transmission lines are recognizable by the distinctive large steel towers seen across the countryside, to which the lines are attached.
Once electricity reaches your community, it goes through a Power Substation or Step-Down Transformer. This equipment takes the high-voltage current and lowers it to around the 44,000 volt range to make it more manageable for distribution to smaller areas like cities or towns.
The electricity continues to travel along distribution power lines until it reaches your neighbourhood where it is stepped-down again to the 7,200 volt range. At this point, the electricity is in the wires that run by your home. Transformers on poles on your street lower the current level of the electricity one final time to 120/240 volts that you use in your home or business.
Ontario ’s provincial power grid consists of over 29,000 kilometres of high voltage power lines that deliver electricity to about 140 industrial and municipal electric users. There are also over 115,000 kilometres of low voltage lines that serve residential, commercial and smaller municipal users, not including the thousands of kilometres of distribution lines run by your local distribution utility! In fact, if you placed all of Ontario's provincial power lines end to end, they would stretch around the earth over 20 times.
So the next time you turn on a light switch, take a moment to think about how far the electricity traveled!
How Hydro-Electricity is Made
When you look at a fast flowing river, you can imagine the natural power and strength of rushing water. If you dive in and try to swim against the flow, you really begin to understand the force of the water.
The concept behind hydro-electricity is the idea of harnessing that force and turning it into electric power through simple mechanics. Hydropower plants are based on a concept that has been around for thousands of years – the water wheel. Water rushes by, pushes against the blades of a wheel, the wheel turns and as it does, it turns another machine that can be used for many purposes. Thousands of years ago, the wheel would turn a machine that ground wheat into flower. Today, while the basic technology is the same, the wheel turns a machine that generates electricity, but our hydro power plants are a little more complicated than a flour mill!
The main parts of a modern hydro-electric power plant are:
Forebay – Most hydroelectric stations use either the natural “drop” of a river or build a dam across a river to raise the water level enough to provide the drop needed to create a powerful driving force. This water reservoir collected at the higher level is known as the “forebay”.
Intake – Gates control the flow of the water from the forebay into an intake pipe, which is also called the “penstock”. The force of gravity pulls the water down through the intake pipe into the turbine.
Turbine – The turbine is the “water wheel” part of the system. The rushing water pushes the blades of the turbine causing it to turn or spin.
Generator – The spinning turbine is connected to electro-magnets inside the generator. These electro-magnets spin inside a coil of copper wire and create a flow of electrons that produce alternating current (AC) electricity.
Outflow – The falling water, having served it’s purpose, exits the generation station through pipes called tailraces where it rejoins the main stream of the river.
The final step in the process is taking the electricity produced by the generator and sending it to a transformer. The transformer coverts the electricity to a high voltage current, which is necessary to distribute it through the long distance power lines that run to your community.
How Natural Gas is used to generate electricity
Natural Gas, also called methane, is considered one of the cleanest burning sources of energy we use. The earliest reference to natural gas has been found in writings from around 125 A.D. that describe “eternal fires” that escaped cracks in the ground and were ignited by lightning. For years many people considered this mysterious gas to be worthless. Even today, some countries burn off their unwanted gas in flames so bright they can be seen from space. However, in North America natural gas is considered one of the most valuable fuels available.
Methane gas was originally used in the 1800’s as a source of fuel for city street lamps. It was during this time that people began referring to it as “natural gas”, to distinguish it from the manufactured “coal gas” that they were accustomed to. In 1885, the inventor Robert Bunsen proved that gas could be used for cooking and heating buildings when he introduced his “Bunsen Burner”. Today, natural gas is used in industry, homes and increasingly in the production of electricity.
Natural gas can be found in a number of different underground formations, including shale, sandstone, coal seams, and deep, saltwater aquifers. It is often found in the same geological formations as oil. A typical formation will supply about 1200 cubic metres of gas for each barrel of oil.
Natural gas is produced by drilling into the areas where pockets of methane were created and trapped during a process that occurred over hundreds of thousands of years. After the gas is pumped to the surface, it is refined to remove impurities, like water and sand, then distributed through large pipelines that span across the country. Large users like factories and electric power plants may get their natural gas directly from the pipeline, while residential and small businesses usually buy natural gas from a local distribution company or utility.
At an electric power plant natural gas is often used as fuel that is burned to create the heat needed to turn water into steam. This steam is then used to turn a turbine that turns a generator that produces electricity.
Since natural gas is clean, easy to pipe from one location to another and convenient to use, it is in many ways considered the ideal fossil fuel and the future will bring many more different and unique ways to utilize this resource.
How a Nuclear Power Plant Makes Electricity
The basic requirement for production of electricity is simple - a force must be used to turn a turbine that generates electricity. With hydro-electric plants, the force of water generates power. Other types of power plants burn coal or natural gas to produce heat that converts water into steam that spins a turbine or generator.
Nuclear reactors operate on the same principle. A nuclear power plant produces heat by splitting uranium atoms, the heat converts water into steam and, as with conventional power plants, the steam spins a turbine or generator that makes electricity. Splitting uranium atoms is known by the technical term – fission.
How does Fission Make Heat?
Almost all atoms have a tiny sub-atomic particle known as a neutron. When a neutron strikes an atom of uranium, the uranium atom splits apart. As the atom splits, it produces heat.
When a uranium atom splits, it not only produces heat, it also releases one to three more neutrons that then go on to strike and split other uranium atoms. This is what is called a “chain reaction”, as more uranium atoms are split they produce more neutrons which then split even more uranium atoms and so on. Throughout the process, more and more heat is released.
Part of the design of a nuclear reactor is the ability to control this chain reaction so that only the amount of heat needed to generate a specific amount of electricity is produced. This is accomplished through the use of a “moderator”. The moderator slows, or moderates, the speed of the neutrons resulting from the fission so they are more likely to collide with, and split, more uranium atoms. The moderator in Canadian reactors is heavy water which is very efficient at slowing down neutrons while not absorbing too many of them. Heavy water is 10% heavier than ordinary water because it incorporates a heavy form of hydrogen called deuterium. The chain reaction can be stopped completely through the use of “control rods” which are inserted into the reactor to absorb the flying neutrons so they do not hit or split any more atoms.
From Heat Comes Steam. From Steam Comes Electricity.
The fission process of a nuclear reactor is designed to produce a large amount of heat. This heat then must be transferred to boilers that make steam. Again pressurized heavy water is used as it is pumped through fuel channels in the reactor where the heat raises its temperature to 300ºC. This extremely hot heavy water is then sent to a boiler where it heats ordinary water into high-pressure steam that spins a turbine that turns a generator that produces electricity. The heavy water is then cooled and returned to the reactor to begin the process over again. At the same time, the ordinary water is cooled and recirculated into the boiler to be reheated.
The final step in the process is taking the electricity produced by the generator and sending it to a transformer. The transformer converts the electricity to a high voltage current, which is necessary to distribute it through the long distance power lines that run to your community.
Nuclear Power Point
Did you know that at a nuclear power plant, pellets of uranium (also called fuel) are packed together into a bundle? Each fuel bundle weights about 22 kilograms and can produce the same amount of heat as 400 tonnes of coal.
How Coal generated electricity is made
Coal is globally an abundant fossil fuel and has a long and distinctive history. Even though you may never see or even think of coal, you use several tonnes of it every year. The amount of coal needed to power the average family electric stove is about a tonne a year, an electric water heater would use about four tonnes of coal a year and an electric refrigerator would consume another tonne a year.
We are not the first people to make use of this resource; in fact, society has benefited from coal since the cave man. Historians have found evidence that the Romans in England used it in the second and third centuries. In the 1700s, the English discovered that coal burned cleaner and hotter than wood charcoal and it became a key factor in the Industrial Revolution. Machines like steamships and steam-powered railroads only became practical after coal was used as fuel for their boilers. By 1875, coal replaced charcoal as the primary fuel for iron blast furnaces in the process of making steel. In the 1880’s coal began being used to generate electricity for homes and factories. While current technology is much more efficient, the generation of electricity is still based on the principle of burning coal to turn water into steam. The steam is then used to turn a turbine that turns a generator that produces electricity.
Coal Power Point
Did you know that coal can be transported by pipeline? Once coal is mined it is crushed into smaller pieces which can be distributed by truck, ship, railroad, or barge. However, crushed coal can also be mixed with oil or water (the mixture is called slurry) and pumped through a pipeline to an industrial user.
Solar Energy
Solar energy has been harnessed for centuries. The earliest reference to solar energy is in the 7th century B.C. when magnifying glass lenses were used to concentrate sunlight to create fire.
Ancient Greeks and Romans would design homes and buildings to make use of the sun’s capacity to light and heat indoor spaces and offset the need to burn wood, which was often in short supply.
In the late 1800’s in France, scientist Auguste Mouchout used heat from a solar collector to make steam to drive a steam engine.
Today, people use solar energy to heat buildings and water and to generate electricity.
How Solar Energy Works
Solar energy is thinly distributed over a large area and must be collected and concentrated to produce usable power. As a result, it currently costs more to produce electricity using solar energy compared to fossil fuels.
The sun’s energy travels via electromagnetic radiation like radio waves, but in a different frequency range. There are two main ways the sun’s energy can be converted into electricity:
- Directly, in a process called photovoltaic conversion ["photo" meaning light and "voltaic" meaning electricity], which requires solar panels.
When sunlight hits a solar panel, it causes electrons in the silicon layered on the panel to move and flow through wires built into the panel to produce electricity.
- Solar thermal conversion, which converts light to heat and then to electric power. Most solar thermal devices heat water to produce steam, which drives a steam turbine.
Available solar energy is often expressed in watts per square metre (W/m²). The amount of energy available from the sun is about the same as a high power hair drier per square metre of sunlight. However, about a quarter of that energy is absorbed as it passes through the Earth’s atmosphere.
Available solar energy is primarily dependent upon how high the sun is in the sky, cloud conditions and on location.
Wind Power
Wind is powered by the sun, which heats our planet to different temperatures in different places and at different times.
The unequal distribution of heat creates wind as warm air rises and cooler air descends to fill the void. Wind is the ongoing movement of this air.
Capturing the Wind
Over 5,000 years ago, ancient Egyptians used wind to sail ships on the Nile River. Later, people built windmills to grind wheat and other grains. The earliest known windmills were in Persia (Iran). The design was further refined centuries later by the Dutch.
North American colonists used windmills to grind grains, pump water and cut wood. As late as the 1920s, North American farmers used small windmills to generate electricity in rural areas without electric service. When power lines began to transport electricity to rural areas in the 1930s, local windmills were used less and less, though they can still be seen on some ranches.
The blades in modern wind turbines work much the same way, spinning to convert wind into electricity. Wind turbines often sit high atop towers so that the blades are free of obstacles and take advantage of higher and more constant wind speeds.
Mechanical power is created when the blades turn in the wind. Turbines use this power to turn a generator and produce electricity.
Turbines are built to adapt to all kinds of wind conditions. Typically the blades begin to turn when the wind reaches 13 km/h and shut off when the wind is too strong – 90 km/h and above. Blade assemblies can rotate to face the wind to optimize electric generation from wind coming from nearly any direction.