How many ways have you used electricity today?
In the modern world, electricity is an essential part of day-to-day life. In fact, it is probably impossible to count all the ways we use electricity. From the moment we wake up we use electricity to toast our bread, listen to the radio or refrigerate our orange juice. Electricity powers the lights in the classrooms and offices where we work. The clothes we wear, even the cars we drive, are made by machines that use electricity.
Where does electricity come from?
To see where electricity comes from all we need to do is look inside a aluminum wire. The problem is what we are looking for is too small to see. But, if you could look past the protective covering, past the aluminum wire’s shiny surface, you would see that the wire is made up of tiny particles. These are atoms, the basic building blocks from which everything in the universe is made.
If you could look closely at an atom you would see that the atom itself is made up of even smaller particles. Some of these particles are called electrons. Usually, electrons spin around the centre, or nucleus, of the atom. However, sometimes electrons are knocked out of the outer orbit of an atom. These electrons become “free” electrons.
All materials normally have free electrons that are capable of moving from atom to atom. Some materials, such as metal, contain a great number of free electrons and are called conductors. Conductors are capable of carrying electric current. Other materials, such as wood or rubber, have few free electrons and are called insulators.
If free electrons in a conductor can be made to jump in the same direction at the same time then a stream, or current, of electrons is produced. This is an electric current. In an electrified wire, the free electrons are jumping between atoms, creating an electric current from 1 end to the other. But, how can the electrons jump in the same direction at the same time? By using magnets.
Surrounding the end of every magnet are invisible lines of force called magnetic fields. If you move a straight wire through a magnetic field, the force will push the free electrons from 1 atom to another, creating electric current. If you move several coils of wire quickly and continuously through the field of a powerful magnet, a great quantity of electric current can be produced.
How does Manitoba Hydro produce electricity?
Manitoba Hydro uses machines called generators to produce electricity. In a generator, a huge electromagnet, or rotor, is rotated inside a cylinder, called a stator, containing coils and coils of electric wires. Some rotors are 12 metres across and weigh as much as 8 railway cars, nearly 380 tonnes. A great deal of energy is needed to rotate something that size. Manitoba Hydro uses the province’s abundant supply of water.
Electricity generated using waterpower is called hydroelectricity. A hydroelectric generating station uses the natural force of a river as energy. The same water flow or current that pushes a floating canoe down a river can also turn a generator’s rotor.
Typically, there are 2 components to a generating station. A powerhouse which houses the generators and a spillway that allows any water not being used to bypass the powerhouse.
At the heart of a hydroelectric generating station is the turbine runner. Looking like a giant propeller, some turbine runners are nearly 8 metres across. Attached to the rotor by a 5-metre shaft, the turbine runner converts the physical energy of the water into the mechanical energy that drives the generator.
Water flows into a station’s powerhouse through the intake and enters into the scroll case. The scroll case is a spiral area surrounding the turbine. The spiral shape gives the incoming water the spiral movement which pushes the blades of the turbine. As the turbine is turned, the attached rotor also spins, generating electricity. The potential energy of the river is converted into the mechanical energy of a generator which produces electric energy. Just 1 of the 10 generators at the Limestone Generating Station can produce 133 million watts or 133 megawatts of electricity. That’s enough to supply power to over 12,000 homes.
When the natural flow of a river is adequate, a run-of-river plant is built. The run-of-river design reduces the need for a large reservoir of water, or forebay, behind the station. Instead, the water flowing into a generating station upstream is used immediately, not stored for later use. The Limestone Generating Station located on the Nelson River is an example of a run-of-river design.
When the natural flow of water is inconsistent or inadequate, a more extensive network of dams is constructed to create a large forebay to provide for times when the river’s water level is low. The dam also creates a head of water, or waterfall, to ensure the water has enough force to spin the turbines. The Grand Rapids Generating Station on the Saskatchewan River is an example of a station that uses a water reservoir.
When you plug a toaster or a stereo into a wall socket there is electricity waiting to toast your bread or play music. But have you ever wondered how that electricity gets from the generator in a hydroelectric station to the socket in your wall? For the answer, we need to take another look at those electrons in our aluminum wire.
Remember, magnets passing over a wire or coil of wire will push electrons causing them to jump between atoms. As the electrons jump they are transferring a charge to the next atom. As the next atom receives the charge its electron will jump. The magnets trigger a chain reaction which moves down the wire. The electric energy can travel down the wire because aluminum is a conductor. It is conducting the electricity. Manitoba Hydro has an extensive system of wires of varying sizes that conduct electricity throughout the province. But, that is only part of the answer.
In Manitoba, nearly 80% of our electricity is produced by hydroelectric generating stations on the Nelson River in northern Manitoba. So, Manitoba Hydro must transmit the electricity it generates about 900 km to southern Manitoba where most people live and work.
But, electricity does not travel long distances easily. In fact, for many years the problems associated with transmitting electricity long distances prevented Manitoba Hydro from building stations on the Nelson River.
Then Manitoba Hydro turned to high voltage direct current (HVDC) technology to solve the problem of transmitting electricity from the north. Direct current (DC) is electric current that flows in 1 direction only. It is the type of power produced by batteries used in cameras, flashlights and cars. The electricity in your home is alternating current (AC), electric current which reverses direction approximately 60 times a second. The advantage of DC is that the power loss over long distances is considerably less than with AC. Also construction of a DC transmission line costs about 1/3 less than an AC transmission line.
A higher voltage is used with DC transmission to increase energy transmission and reduce losses. To explain why, we can make a comparison between the electricity flowing through a wire and water flowing through a pipe. Just as great quantities of water can be moved through a large diameter pipe, a great quantity of electricity can be moved through a large diameter wire. Great quantities of water can also be moved through a small diameter pipe, such as a garden hose, by increasing the pressure. Similarly, electricity can be moved in greater quantities through a small diameter wire by increasing the voltage.
Manitoba Hydro has built 2 HVDC transmission lines, known as Bipole I and Bipole II, to bring electricity from the north.
Let’s say the electricity in your house has the same force as a baseball pitched towards you at 100 km per hour. The force of the electricity on the HVDC line would be over 4,000 times more powerful. Imagine trying to stop a car travelling 100 km per hour with a baseball glove.
As generators spin they produce AC electricity that has about 25 kV of force. So, the electricity generated by the hydroelectric stations on the Nelson River must be converted to DC and transmitted at an even higher voltage to reduce the power losses experienced over long distances. This conversion is accomplished at the Henday and Radisson converter stations located near Gillam, Manitoba.
Once the electricity has been converted it travels south to the Dorsey Converter Station. At Dorsey, the electricity is converted back to AC because the refrigerators and other appliances people use in their homes are designed to run on AC electricity. From Dorsey, eleven 230 kV lines supply southern Manitoba and interconnections to Saskatchewan, Ontario and the U.S.
The high voltage lines transport the electricity to substations which are located throughout the province. These substations contain a variety of equipment used to transform voltages to lower levels, switch current in a line on or off, and analyze and measure electricity.
The transformation of electricity from high voltage to low voltage is accomplished using the same principle as generation. The magnetic field of a coil of wire carrying an alternating, or fluctuating current, is capable of causing a fluctuating current in a second coil. In a transformer, 2 separate coils of wire are wrapped around a magnetic iron core. The electricity in the first coil of wire creates a fluctuation in the magnetic field of the iron core. That fluctuation then passes through the iron core, electrifying the second coil of wire. If the second coil of wire has half as many turns the electricity will have half the voltage. If the second coil has twice the number of turns, then the voltage will be doubled.
From the substations, the electricity runs through overhead lines, or underground cables to transformers located near a customer’s home or business. Located near the tops of hydro poles or at ground level where there is underground service, these transformers complete the voltage reduction.
From the pole, electricity travels through wire into your home, going first to the meter and the main switch. The wires then lead to a distribution panel. From there, circuits hidden inside the walls lead to the power outlets and light fixtures.
Electricity today and tomorrow: alternative sources
Next time you are boiling water, put a lid on the top of the pot. As the water boils, it expands and turns into steam. The pressure of the expanding steam will eventually shake or raise the lid. A thermal generating station uses this same energy to turn turbines that drive electric generators. The fuel used to heat the water can be coal, oil, natural gas or a nuclear energy source.
We maintain 2 small thermal generating stations, in Brandon and Selkirk. The thermal stations are used to help meet power demand during times of low water flows or to provide extra electricity during periods of high demand, particularly in winter.
Unlike hydroelectric generating stations, thermal generating stations can be built almost anywhere. However, the major disadvantage of thermal stations is that fossil fuel, like the natural gas used by Manitoba Hydro, is not self-renewing like water power.
When you’re outside on a windy day, you can feel the wind push against your body. That push can also spin blades on a wind turbine which produces electricity.
Though not practical in all locations, wind generators are a good idea in those areas where they can be used because wind, like water, is a renewable resource. However, wind generators have 2 main drawbacks. First, they are expensive. Second, not all locations have consistent strong winds.
Biomass is a general term used to describe organic or living matter such as wood. Biomass generation means burning organic matter rather than fossil fuels to create electricity. Potential biomass fuels include residue from the forestry and agricultural industries. Everything from rice hulls to coffee grounds could be burned to create steam.
Plants are able to create food from the light of the sun. This process is called photosynthesis. The word photo means light and the word synthesis means to change. We can also use the sun’s light to make electricity. Panels made from silicon are able to convert sunlight to electricity through the photovoltaic process. Voltaic is another word for electricity.
Photovoltaic (PV) panels can be used to power everything from calculators to appliances in your home. One of the advantages of solar energy is that it doesn’t need fuel. Unfortunately, PV panels are very expensive. So, the widespread use of solar energy is not yet practical when compared to hydroelectric generation.
If you blow up a toy balloon and then let go of the neck, the balloon will shoot away. The force that pushes the balloon, expanding air, is the same force that drives a gas combustion turbine.
A combustion turbine looks and operates something like a jet engine. In a combustion turbine, fuel such as natural gas is mixed with compressed air and combusted. The gases produced during combustion are hot and under pressure. In most combustion turbines, the combustion gases can reach up to 1,300°C. The super hot, high pressure gases are pushed into the turbine section where they are allowed to expand and apply pressure across the blades of a rotating turbine that drives an electrical generator.
Over the last decade, combustion turbines have gained importance as an electric generation option. In fact, we operate 2 natural gas combustion turbines as part of its Brandon Generating Station.