4.4 Producing Electricity from water
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There are many different ways that we can generate electricity from water. Some include hydroelectric power, tidal energy and wave energy.
A dam prevents water from passing down river. The water is then let through at a controlled rate. As the water is let through it turns a turbine and thus generates electricity.
Hydroelectric Power
The three Gorges dam in China is an example of a hydroelectric power station. At most hydroelectric power plants, they flood a valley by building a large dam in the way of a river. The river then feeds the dam, which leads to a build-up of water. Whilst the water is behind the dam it has gravitational potential energy. The water is then let through the dam at a controlled rate. The kinetic energy of the water turns the turbines and generates electrical energy. They can change the rate depending on the amount of demand for electricity at that given time.
The advantages of a hydroelectric power plant is that it can respond to changes in demand for electricity as they can allow more water to pass through the dam. Also, the plant has minimal running costs. It is also a useful way to generate electricity in remote areas.
However, the initial costs of a hydroelectric power plant are huge. The three Gorges Dam in China costs around 180 billion yuan, which is around £18 billion. Also, there is a great impact on the environment due to a significant amount of land behind the dam being flooded. This will cause humans and animals to be displaced from their land. Furthermore, if there is a drought the hydroelectric power station may not be able to generate electricity. But, the dams tend to hold significant amount of reserves of water, so the complete drying up of the dam is unlikely.
The three Gorges dam in China is an example of a hydroelectric power station. At most hydroelectric power plants, they flood a valley by building a large dam in the way of a river. The river then feeds the dam, which leads to a build-up of water. Whilst the water is behind the dam it has gravitational potential energy. The water is then let through the dam at a controlled rate. The kinetic energy of the water turns the turbines and generates electrical energy. They can change the rate depending on the amount of demand for electricity at that given time.
The advantages of a hydroelectric power plant is that it can respond to changes in demand for electricity as they can allow more water to pass through the dam. Also, the plant has minimal running costs. It is also a useful way to generate electricity in remote areas.
However, the initial costs of a hydroelectric power plant are huge. The three Gorges Dam in China costs around 180 billion yuan, which is around £18 billion. Also, there is a great impact on the environment due to a significant amount of land behind the dam being flooded. This will cause humans and animals to be displaced from their land. Furthermore, if there is a drought the hydroelectric power station may not be able to generate electricity. But, the dams tend to hold significant amount of reserves of water, so the complete drying up of the dam is unlikely.
Pumped storage has a high and low reservoir. Water is pumped to the high reservoir when there is surplus energy. The water is then released when there is high energy demand.
Pumped Storage
Pumped storage is a way of meeting electricity demand. There are two reservoirs; a high and low reservoir. Surplus energy is used to pump water from the lower reservoir to a higher reservoir. The water in the high reservoir has gravitational potential energy. When there is a sudden increase in demand for electricity, water (with gravitational potential energy) is released from the upper reservoir. As the water travels to the lower reservoir it turns turbines that generate electricity. These sudden increases in demand could be because everyone is cooking dinner/ people are coming back from work and putting the kettle on. Pumped storage can supplement the steady delivery of energy from power stations (base load).
Surplus energy usually comes about at night. This is because the boilers in power stations are kept running all the time despite electricity demand being very low.
We need to remember that pumped storage is not a way of generating new power. It is only a way of storing power.
Pumped storage is a way of meeting electricity demand. There are two reservoirs; a high and low reservoir. Surplus energy is used to pump water from the lower reservoir to a higher reservoir. The water in the high reservoir has gravitational potential energy. When there is a sudden increase in demand for electricity, water (with gravitational potential energy) is released from the upper reservoir. As the water travels to the lower reservoir it turns turbines that generate electricity. These sudden increases in demand could be because everyone is cooking dinner/ people are coming back from work and putting the kettle on. Pumped storage can supplement the steady delivery of energy from power stations (base load).
Surplus energy usually comes about at night. This is because the boilers in power stations are kept running all the time despite electricity demand being very low.
We need to remember that pumped storage is not a way of generating new power. It is only a way of storing power.
A wave powered turbine uses air to generate electricity.
Wave Powered Turbines
We turn wave energy into electrical power by having many small wave turbines like the diagram shown below. As the waves come to the shore they provide an up and down motion pushing air through a turbine that is attached to a generator, which generates electricity. The generated electricity is then sent through electrical cables and will usually join a grid. There is no pollution created when the wave-powered turbines are creating power. However, wave turbines tend to be unsightly and spoil a view. Also, they are not able to respond to increases in demand as the amount of energy that they produce is dependent upon how large the waves are. Furthermore, the initial costs of wave energy are high and they tend to generate trivial amounts of energy
We turn wave energy into electrical power by having many small wave turbines like the diagram shown below. As the waves come to the shore they provide an up and down motion pushing air through a turbine that is attached to a generator, which generates electricity. The generated electricity is then sent through electrical cables and will usually join a grid. There is no pollution created when the wave-powered turbines are creating power. However, wave turbines tend to be unsightly and spoil a view. Also, they are not able to respond to increases in demand as the amount of energy that they produce is dependent upon how large the waves are. Furthermore, the initial costs of wave energy are high and they tend to generate trivial amounts of energy
Tidal power has turbines that generate electricity.
Tidal Power
Tidal power can be turned into electricity by using a tidal barrage, which is a dam that is built across a river estuary. An estuary is a part of a river where the tide meets the sea. The water level of this part of the river will rise and fall with the tide. There are turbines in the tidal barrage. When the tide comes in, it fills up the estuary and turns the turbines in the tidal barrage. The barrage traps the water on the other side and lets the water through at a controlled speed, whilst the tide is receding (the water on the sea side of the barrage is lower than the water on the river side of the barrage). Tidal power is a renewable energy resource as the energy is created from gravity, the sun and the moon. Also, there is no pollution caused when using this way to generate electricity. Furthermore, we can predict the heights of tides and at what time they will occur with a good degree of accuracy. However, the height of tides does vary throughout the year. The turbines will also not work four times a day when the water level is the same on sea side and river side. It is four times because the tide comes in twice a day and the level will be the same when coming in and out (2x2=4). The running costs of a tidal barrage are low.
However, the initial costs are high. Also, the barrage can affect boats from going passing. Furthermore, it can look unsightly and effect wildlife.
Tidal power has the potential to generate a significant amount of energy.
Tidal power can be turned into electricity by using a tidal barrage, which is a dam that is built across a river estuary. An estuary is a part of a river where the tide meets the sea. The water level of this part of the river will rise and fall with the tide. There are turbines in the tidal barrage. When the tide comes in, it fills up the estuary and turns the turbines in the tidal barrage. The barrage traps the water on the other side and lets the water through at a controlled speed, whilst the tide is receding (the water on the sea side of the barrage is lower than the water on the river side of the barrage). Tidal power is a renewable energy resource as the energy is created from gravity, the sun and the moon. Also, there is no pollution caused when using this way to generate electricity. Furthermore, we can predict the heights of tides and at what time they will occur with a good degree of accuracy. However, the height of tides does vary throughout the year. The turbines will also not work four times a day when the water level is the same on sea side and river side. It is four times because the tide comes in twice a day and the level will be the same when coming in and out (2x2=4). The running costs of a tidal barrage are low.
However, the initial costs are high. Also, the barrage can affect boats from going passing. Furthermore, it can look unsightly and effect wildlife.
Tidal power has the potential to generate a significant amount of energy.