The Shedding Light on Electricity series exposes the shocking truth about electricity. Yes, positively a bad pun to begin with, but we promise to conduct ourselves really well from now on. This series teaches students watts of stuff (sorry, couldn’t help ourselves) about electricity including how it’s produced, how it’s used in our homes, how it’s controlled, and how we keep ourselves safe from nasty shocks. This is high-voltage education that is hard to resist!
In Episode 1, Sources of Electricity, we take a detailed look at where our electricity comes from: thermal and hydroelectric power stations, wind farms, and solar farms. We also examine the advantages and disadvantages of these sources of electricity.
A 4-minute excerpt.
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The Transcript (which can be used as a textbook)
Part A: Introduction
Part B: What is Electricity?
Part C: Thermal and Hydroelectric Power Stations
Part D: Intermittents (Wind and Solar)
Part E: The Supply Mix
Part F: Advantages and Disadvantages
Part A: Introduction
In this series, we’re going to study electricity! Electricity has become indispensable to modern living.
Electricity is used to produce light, heat in for example electric heaters and ovens, movement in electric motors which are in, for example drills and trains, it’s used in communications and a whole lot more.
Millions of people are employed in industries that are directly related to the production of electricity, to the design and production of things that use electricity, and to the infrastructure (the wires and all that) needed to get the electricity from where it’s produced to (and around) our homes, schools, and businesses.
At a simple level, whenever you want something, like a light globe, to use electricity there are four things that are required.
Firstly, there needs to be a source of electricity.
Most of our electricity, by far, comes from huge generators in large power stations, monster versions of my small hand-cranked generator. When a generator spins it generates electricity. We’ll get into the detail later. Solar panels also produce electricity, as do batteries.
Secondly, you need what’s called a “load”, something that uses electricity. Light globes, motors, heaters and millions of other things that use electricity are all collectively called loads.
Thirdly, you need wires to conduct the electricity from the source of the electricity to the load. The wires include the huge transmission lines that connect large power stations to our cities and to the tiny wires inside electronic equipment.
Fourthly, you need a switch so that you can turn the load on or off. Now you could argue that you don’t really need a switch because you can just unplug something, but switches make electrical devices much safer and more convenient to use.
In this series, were going to look at how electricity is produced and at how switches, light globes, wires and other things are all connected to each other. We’ll be discussing electrical circuits, voltage, current, power and a whole lot more.
We’ll begin though with a brief explanation of what electricity is and how it’s generated.
Part B: What is Electricity?
Electricity is, basically, the movement of electrons through a material.
Atoms are made of protons and neutrons that are held together in the nucleus of the atom and electrons that move around the nucleus at really high speeds, making the atom kind of spherical. Each electron has a mass of only about 1/2000 of the mass of a proton.
Electrons are arranged in what are called “electron shells”. In all metals, the outermost electrons in the outer shells actually just randomly bounce around all over the place from atom to atom.
However, if a metal wire is connected to an electrical source, like a battery, the outermost electrons are forced to move along the wire from atom to atom. This flow of electrons along a wire is called an electric current because it’s a bit like a river current. The whole set up is called an electric circuit.
So, electricity is basically the movement of electrons through a material. What are the main sources of electricity though? This light globe is being powered by this battery, but where is the electricity powering this light globe coming from?
Well, most of the world’s electricity comes from coal-fired power stations, gas-fired power stations, nuclear power stations, hydroelectric power stations, wind farms, and solar panels. All of these generate electricity and the electricity is fed in to wires which carry the electric current to our homes and industries. This whole system of wires is called the grid. The things that produce electricity feed electricity into the grid. Let’s take a closer look at them.
Part C: Thermal and Hydroelectric Power Stations
This is a simple generator. When I turn the coils of wire that are surrounded by these magnets, electricity is produced.
This is another, much smaller generator. When I turn it you can see from the voltmeter that it produces electricity. If I connect it to some LEDs, the LEDs light up when I spin the generator.
Most of the electricity that is generated in the world to power our homes and schools and industries is produced by generators.
Over the past 100 years or so, the huge generators in coal-fired power stations, like this one, have been the number 1 source of electricity in the world. So how do they work?
Firstly, the coal is dug up by huge excavators. This one’s called a bucket-wheel excavator. It’s about 200 metres long but most aren’t quite this big.
The coal is then carried by conveyor belts into the power station and it’s fed into huge boilers many stories high, where it is set on fire.
The water in the boiler boils and turns to steam. The steam is forced up though pipes into huge turbines. The turbines are kind of like wind mills, and they spin as the steam pushes on them. This is what the turbines look like. They’re normally enclosed but here they were undergoing maintenance. Each turbine is connected to a generator, so that as the turbine spins, the generator spins as well. As we’ve seen, electricity is produced when any generator is made to spin. The hot steam is then cooled down in the condenser so that it condenses, and then the water is pumped back into the boiler so that the cycle can repeat. The condenser is kept cool by cool water that is pumped into it either from a nearby river or lake, or from what are called cooling towers. The white clouds that are often seen above cooling towers are made of water that has evaporated in the cooling process.
Coal-fired power stations need huge amounts of coal of course and, because it’s difficult to transport coal large distances, most of them are built near coal mines so that the coal doesn’t have to be transported very far. Transmission lines are constructed to carry the electric current to our towns and cities.
Now gas-fired power stations work in pretty much the same way as coal-fired power stations. All you need to do is change the heading on the animation, stop burning coal and burn natural gas instead, the same natural gas our gas cook tops burn.
Nuclear power stations, like coal- and gas-fired power stations, also boil water in huge boilers and the steam is used to turn turbines. However, the heat doesn’t come from burning fuels, it comes from the nuclear energy of uranium atoms.
If you recall, the nucleus of an atom is made of protons and neutrons. Nuclear power stations use uranium atoms that have 92 protons and 143 neutrons in their nucleus.
They’re called uranium-235 atoms because they have a total of 235 protons and neutrons. Here I’m not showing any electrons.
In the 1930s, it was discovered that if a uranium-235 atom was struck by a lone neutron which could be generated using certain radioactive elements, it would split into two roughly equal parts and release a huge amount of heat energy. Also, the splitting atom would typically release more neutrons which could then be made to split more uranium-235 atoms.
This chain reaction is used to produce a steady amount of heat, heat which is used to boil water to make steam to turn turbines to turn generators which generate electricity.
Coal-fired, gas-fired, and nuclear power stations are called thermal power stations because they rely on heat to operate. The word thermal refers to anything to do with heat.
Hydroelectric power stations also use generators, but the generators aren’t turned by steam, they’re turned by water, liquid water.
A dam is built across a river and a reservoir of water builds up behind it. Pipes are built into the wall of the dam to allow water to flow through it. The flow of water can be controlled. The pipes direct water through water turbines which spin as the water flows through them. The turbines are connected by steel shafts to generators, which generate electricity as they turn.
In Australia, coal-fired power stations produce about 73% of all the electricity generated and gas-fired power stations about 9%. We don’t have any nuclear power stations. Hydroelectric power stations produce about 7%.
Worldwide, coal-fired power stations account for about 38% of all electricity generation, gas-fired power stations for about 23%, nuclear power stations for about 10%, and hydroelectric power stations for about 16%. All of these figures are approximate. Thermal and Hydroelectric power stations can generate electricity continuously and they can be cranked up or powered down depending on how much power is needed.
However, some of our electricity comes from sources that operate intermittently, that is, sometimes they’re on, and sometimes they’re off. Let’s take a look at them.
Part D: Intermittents
So, we’ve seen how steam and liquid water can be made to turn generators. Generators can also be turned by the wind.
Behind me are some wind turbines. They’re about 100 metres tall.
From a distance, it’s hard to gain an idea of how tall they are. The huge turbine blades, some 30 metres long, are connected to a generator inside this housing. When the wind is blowing, the blades turn, which turn the generators, which generate electricity. Cables inside the tower connect the generator to the grid.
Here I’ve connected a small model of a wind turbine to a small generator. When I turn the fan on to create wind, the model wind turbine is pushed by the wind and once the generator attached to the wind turbine starts spinning fast enough, the electricity generated powers up the LEDs.
We call groups of wind turbines that are near each other wind farms.
Obviously when the wind isn’t blowing, wind turbines don’t generate electricity, so they are only ever built if additional electricity from non-weather-dependent sources, like say, coal-fired power stations, is available. They are usually built in regions that gets lots of wind.
Another contributor to our electricity supply is solar. Solar panels produce electricity when light shines on them.
Here we’ve set up some solar panels that are producing electricity. The exact process by which they work is pretty complicated, but basically the panels are made up of layers of certain high-tech materials. When light strikes one layer, the electrons jump across to another layer and then move around the circuit, powering, in this case, the LEDs.
Solar panels are often installed onto rooves by homeowners, or companies or governments set up what are called solar farms. Obviously, solar panels don’t generate electricity at night, so most houses still stay connected to the grid.
Some owners install batteries into their systems. The batteries are charged by the solar panels during the day (as long as the solar panels are generating more electricity than what the house is using of course). The batteries can then be used at night to provide electricity. However, battery technology is still nowhere near good enough to power large factories.
In Australia, wind turbines supply about 8% of our electricity, while solar accounts for about 3%. Worldwide, wind supplies about 5% of all the electricity that is generated while solar panels produce about 3%. A small percentage is also generated by other means.
Wind turbines and solar panels are said to be intermittent sources of energy because they can’t provide electricity 100% of the time. The word intermittent means irregular, sometimes on and sometimes off.
Now these percentages are long-term averages, but the actual percentages at any given moment change throughout the day. The total amount of power being generated also changes throughout the day. Let’s take a look.
Part E: The Supply Mix
So, these are the main sources of the electricity that we use in our homes and industries.
Now the thing about electricity is that it can’t be stored in large quantities. A phone battery can supply a small amount of electricity, and a car battery can supply a little more, but no batteries can supply whole cities with electricity. The huge amount of electricity that we use in our cities has to be generated in real time as we use it. When we need more electricity, more electricity has to be generated, and when we use less electricity, less electricity is generated.
This graph shows how much electricity was being used in Victoria, my home state, over a 24-hour period in the month of April when the weather was quite pleasant. During the night, when most people were asleep and most businesses and factories were shut, electricity demand was relatively low. As a result less electricity was being generated. By the way the unit here is the megawatt, so at about 4 am, just under 4,000 MW of power was being generated, which is 4000 million watts. This light globe is a 4 W light globe, so even at its lowest point, there was enough electricity being generated to power 1 billion of these globes.
At around 5, 6, 7 in the morning, people started waking up and turning on lights and things, the trains and trams started running, factories fired up and so on. More electricity was required so more was generated, and we’ll look at how this happened in a second. During the day, electricity usage decreased a little and this is fairly common; the trains and trams, which are big users of electricity were on a reduced schedule and we had switched off everything at home because fewer of us were at home. In the afternoon and evening, electricity demand increased. We travelled home, we turned on lights and ovens and things, and so the electricity suppliers had to produce more electricity. It peaked at about 6 pm which is very common. Gradually, as most people wound down for the evening and then went to bed, the demand for electricity decreased, and it was at its lowest again at around 4 am.
Generally when it’s cold in the middle of winter and the days are shorter, electricity demand is higher as we need more heating and lighting. It’s also higher on really hot days when everyone wants air conditioning. When it’s not too hot and not too cold, the electricity demand is lower, so less electricity is generated.
The companies and government departments that produce and co-ordinate electricity production have to adjust how much electricity is produced depending on how much electricity is needed.
This graph shows how much electrical power was being generated in the eastern states of Australia over a 48-hour period in March and what the sources of power were.
At about 5 am on March 16, when the demand was fairly low, about 83% of the electricity supply was coming from coal and gas, about 12% was coming from wind and about 5% was coming from hydro. None was coming from solar, because the sun hadn’t risen.
The demand rose during the morning, so more electricity had to be generated. This was achieved in two ways. Firstly, the coal-fired power stations fed more fuel into their boilers so that the generators produced more power.
Also, the hydroelectric power stations opened up their gigantic valves so more water flowed and this also produced more power. You can see here that hydro was contributing only about 5% of the total power at about 5 am but by about 7 am, it was producing about 10% of the total. When the sun rose, solar power came into play so the coal-fired, gas-fired, and hydroelectric power stations reduced their output a little.
At about 6 am on both days, the wind was blowing steadily and so the gas-fired power stations didn’t need to generate much. However, at about 6 pm on both days, the wind dropped off and the sun went down just when we needed the most electricity. The coal-fired, gas-fired, and hydroelectric power stations had to ramp up generation enormously, so it was a good thing that we had them and that we had the spare capacity to make up for wind power’s instability.
There are actually teams of people whose job it is to forecast as accurately as they can what they think the demand for electricity will be.
For example, on a really hot day, more people will be using air conditioners, which use a lot of electricity.
They have to factor in weather conditions like how hot, how sunny, and how windy it will be, sunrise and sunset times, the day of the week (demand is a little lower on weekends), any major events (at stadiums, for example), public holidays (people often stay up until late on New Year’s Eve), and more. They then communicate with all the electricity suppliers and try to make sure that enough electricity is being generated so that when we flick the switch the power comes on and we don’t get blackouts. Nothing’s really automatic. People have to make decisions.
Let’s now take a look at the advantages and disadvantages of the main forms of electricity generation.
Part F: Advantages and Disadvantages
All types of electricity-generation systems have advantages and disadvantages.
Coal- and gas-fired power stations can produce electricity continuously, day and night. The electricity they produce is also relatively cheap, as long as you have a good supply of coal and gas, which Australia does. These are two huge positives and they account for why these types of power stations have dominated electricity generation. A disadvantage of using coal and gas is that they may run out one day, although on current usage, Australia has about 500 years’ worth of coal. Another disadvantage is that burning coal and gas releases carbon dioxide into the atmosphere. Carbon dioxide is a greenhouse gas, and many climate scientists believe that too much of it may cause our atmosphere to warm up too much.
Nuclear power stations also produce electricity continuously. The main problem they have is that they produce nuclear wastes that are very radioactive and dangerous, and no one knows exactly what to do with the wastes. Currently they’re stored underground in disused mines.
There are also high set up costs involved in nuclear power because the buildings have to fully enclose the radioactive materials and stop them from getting out.
One advantage of hydroelectric power stations is that their power output can be adjusted very quickly. They can go from zero to full capacity in minutes, so they can easily be cranked up when more power is needed. Thermal power stations take much longer to adjust. So the people who forecast the electricity demand don’t have to get it 100% right, because hydroelectric power stations can adjust quickly. Another advantage is that they have low running costs because the rain water that flows into the reservoirs is free. They also don’t produce waste products while they’re operating.
A big disadvantage of hydroelectric power stations is that they can’t be built just anywhere; they need the right mix of mountainous terrain and rainfall. Australia actually has very few sites left where we could build more of these power stations. Also, if an area experiences a drought, and the water runs out, they can’t produce any power at all. During a drought in 2016 in Tasmania, which generates about 90% of its electricity from hydro, electricity generation had to be decreased and a few large industries had to be shut down so that there would be enough power for the rest of the state. Undersea cables to Victoria’s grid have now eliminated that problem, but other parts of the world still occasionally suffer power cuts when the rains don’t come.
Another disadvantage is that when the water level rises up behind the wall of the dam, huge reservoirs are created in what had been normal land with rivers running through it. You essentially flood the natural habitats of the animals and plants that lived there, or the farms of the humans that lived there, and you affect the way that the river runs.
The main advantage of wind turbines is that they don’t produce wastes (once they’re in operation), because they just use the wind. When the wind is blowing, coal and gas, nuclear, and hydro can reduce their output, so wind turbines help a nation conserve fuel and water, in other words, when it’s windy you don’t have to for example burn as much gas or use up the water in your reservoirs.
However, their big disadvantage is that they’re unreliable because the wind doesn’t blow all the time and when it is blowing its speed fluctuates a lot, so states and countries have to build more reliable electricity sources to provide power when the wind turbines can’t.
So, though the thousands of wind turbines in Australia provide an average of about 8% of our electricity, quite often their production falls to less than 2% when it’s calm, and occasionally it even gets down to below 1%, so if we didn’t have coal- and gas-fired power stations and tried to rely mainly on wind turbines, we would have to build tens of thousands more of them and we would still get blackouts a few times every year when there’s no wind at all.
Wind turbines are also expensive to set up (for the amount of power that you get out of them). Some people say they’re ugly and they reduce the visual appeal of the country side, but that’s a matter of opinion.
The advantages of solar are similar to those of wind. The biggest disadvantage of solar panels is that they too, like wind turbines, can’t produce a continuous supply of electricity. At night they need a backup.
So now we know the basics of where most of our electricity comes from. In our next episode, we’re going to look at how electrical equipment like lights and thing are connected. See you then.
Written and directed by Spiro Liacos
Footage of various hydroelectric power stations in Tasmania by ARENA (the Australian Renewable energy Agency)
Creative Commons Attribution 2.5 Australia licence
Footage of bucket-wheel excavator (SchaufelradBagger 288 – Bucket-wheel excavator 288 (Open Pit Mine Garzweiler II, Germany) https://www.youtube.com/watch?v=imFah9EHSkw by DerNaut1,
https://www.youtube.com/user/DerNaut1. Creative Commons license.
Energy Mix Graphs adapted from data at AEMO (the Australian Energy Market Operator), https://aemo.com.au
Check out their excellent interactive graphs at https://aemo.com.au/en/energy-systems/electricity/national-electricity-market-nem/data-nem/data-dashboard-nem for real-time information about Australia’s electricity generation. How much electricity are we getting from coal, from wind, from gas…?
Nuclear Power in the 21st Century (https://www.youtube.com/watch?v=kwn8rAYgZVw) by the IAEA (the International Atomic Energy Agency). Creative Commons license.