Transcript of What is hydroelectricity?

What is hydroelectricity? (6:14)

WARNING: Aboriginal and Torres Strait Islander viewers are warned that the following video may contain images and voices of deceased persons.

Narrator - Hydroelectricity is a renewable form of energy, one that harnesses the power of flowing water to generate electricity. In this episode, we'll explore the following questions: What is hydroelectricity? And how does the Snowy Mountains Hydroelectric Scheme generate electricity? Hydroelectricity is power that is generated using the energy supplied by falling water. Hydroelectricity produces no greenhouse gases and does not pollute the atmosphere. It is a clean renewable way to sustainably produce electricity. In the Snowy Hydro Scheme, water from rain and snow melts is collected and stored behind several large dams at varying heights above sea level. This water has stored gravitational potential energy. As the water falls and flows through the pipes from the higher to lower dams, potential energy is converted to kinetic energy. The water flows from the upper dam via tunnels and pipelines into a power station where it passes through massive turbines. Here the kinetic energy of moving water is converted to mechanical energy and turns the turbines. Each turbine spins a large electromagnet, inside a fixed wire coil in a generator converting mechanical energy into electrical energy. The Snowy Hydro Scheme is essentially a system that uses energy stored in water as it falls from higher to lower dams and reservoirs to produce electricity. In your home, the electrical energy can be converted by devices into light, heat and sound energy. The amount of electricity able to be generated depends on the distance the water falls, and the volume of the water which flows through the turbine. The greater the fall, the greater the kinetic energy, and the greater the amount of electricity produced. Kent Allen, Area Manager with Snowy Hydro explained this process to us.

Kent Allen - That it is a very simple process in terms of how you produce power from water. So we're trying to get this water through to the wires and back out to all our customers out on the network. But what we have above the power station is a reservoir. So it's 280 metres above us in this particular power station travels through a four and a half kilometre long tunnel, down some pressure shafts and down to the turbine here. Now this is a large valve that sits here just in front of where we convert that water flow and pressure into power. So this large valve is sitting here holding the water back. So no water is flowing, that 280 metres of elevation of water converts into 2800 kilopascals of pressure. When we want to start the machine up, we actually bypass water around here and pressurise what we call a spiral casing. So then we open this large valve, we still don't have any water flowing as such. So it's just sitting there pressurised. And we have what look like aircraft wings, just little short things we call guideveines that actually sit around a big, what we call a turbine runner. And the water passes through that, but we have to regulate. And these things that look like aircraft wings--guideveins that actually open and close to regulate the water. So we can increase the water flow through it or reduce the water flow through it. As we increase the water flow that applies a pressure and a force onto blades on the runner. The thing that looks like a merry go round, and it rotates the shaft. So the more pressure and more force, more mechanical power, so more kinetic energy that we we're transferring back up this shaft, the water's flowing through and back out to the next reservoir. This shaft's transferring mechanical power back up into this area here which is the generator. This is where all the electrical things happen. In here is what we call the generator Rotar. It actually is like a big rotating magnetic field, lots of north and south poles. And that's what we call exciting the stator. So it's actually pushing electrons out through the stator. Those electrons are flowing out through the wires out to your networks around your local towns, through your wires into your house, through to your lights, your toaster, your microwave, your air conditioner, and all happening at the speed of light!

Narrator - At Tumut 3 Power Station for example, water falls more than 150 metres from Talbingo Reservoir to the generators in the power station, the Scheme's largest Each of the six generators at Tumut 3 can generate about 1,500 megawatts of electricity. That's more than enough electricity to power Canberra. Hydro power plants are a way of producing a sustainable electricity supply. They have what is known as pumped storage. Energy produced from renewable sources, such as wind or solar is used to pump water from the lower reservoir into the upper reservoir at times of low demand. When demand is higher water is released back into lower reservoirs running downhill through turbines to generate electricity. Being able to use water over and over again makes the generation of hydroelectricity more energy efficient and sustainable.

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