4.3 Renewable Energy: Geothermal & biofuels
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A diagram of how geothermal energy works.
Geothermal energy generates electricity from heat in the ground. It can only be used in areas where there are hot rocks a few miles below the earth’s surface. The hot rock heats up water, which is pumped to the earth’s surface. The steam and hot water turn a turbine, which is connected to a generator, thus electricity is generated. There is little environmental impact of using geothermal energy. However, there are very few suitable locations around the world. Iceland and the United States are places where geothermal energy is used.
In the Western States of the United States, they use geothermal reservoirs. The power plants use the steam from the reservoirs to generate electricity. Others geothermal power plants use water that vaporises a working fluid that turns a turbine.
Some locations use geothermal energy to directly heat homes. (maybe find an example of how this is exactly done).
The cost of setting up a geothermal energy power plant is high in comparison to the amount of energy that is generated, thus making this method of electricity generation not very economically viable.
In the Western States of the United States, they use geothermal reservoirs. The power plants use the steam from the reservoirs to generate electricity. Others geothermal power plants use water that vaporises a working fluid that turns a turbine.
Some locations use geothermal energy to directly heat homes. (maybe find an example of how this is exactly done).
The cost of setting up a geothermal energy power plant is high in comparison to the amount of energy that is generated, thus making this method of electricity generation not very economically viable.
Sugar cane, which is used to make bioethanol.
Biofuels
Biofuels are produced from plant materials. They are renewable as we can grow more of the plants that are used in biofuel in less than a year. Whereas, fossil fuels, such as coal and oil, take millions of years to form. We can use biofuels to run our power stations or fuel our cars. Biofuels can be solid (wood and straw), liquids (ethanol and biodiesel) and gases (methane).
When we use biofuels in power stations, they are used in the same way that we use normal fossil fuels. They are burnt to create heat energy, which heats water. The hot water, turns into kinetic energy by turning the turbines. The turbines are attached to a generator, which turns kinetic energy into electrical energy.
We can also use biofuel to run vehicles. The two main types of biofuels that cars can be run off are biodiesel and bioethanol. Biodiesel is made from rapeseed oil and other plant oils. It can be used in diesel-powered vehicles without any engine modifications.
Bioethanol is not a hydrocarbon as it contains oxygen (hydrocarbons only contain hydrogen and carbon). It is a liquid fuel that burns well. It is made from fermenting sugar from sugar cane, wheat and other plants. Normal petrol engines can use up to 10% ethanol mixed into their fuel without modification but further modification is required as bioethanol makes up more than 10% of the fuel. Most petrol sold in the UK contains some amount of ethanol.
Biofuels are renewable resources as they can be grown fairly quickly. Also, when they are burnt, they release the same amount of carbon dioxide as they have taken in when they were grown. However, they are not carbon neutral because greenhouse gases will be produced during the production of the crops (the planting, watering, fertilising, harvesting and processing of the fuel all produce greenhouse gases). Having said this, they are considerably better for the environment than burning fossil fuels.
Biofuels are produced from plant materials. They are renewable as we can grow more of the plants that are used in biofuel in less than a year. Whereas, fossil fuels, such as coal and oil, take millions of years to form. We can use biofuels to run our power stations or fuel our cars. Biofuels can be solid (wood and straw), liquids (ethanol and biodiesel) and gases (methane).
When we use biofuels in power stations, they are used in the same way that we use normal fossil fuels. They are burnt to create heat energy, which heats water. The hot water, turns into kinetic energy by turning the turbines. The turbines are attached to a generator, which turns kinetic energy into electrical energy.
We can also use biofuel to run vehicles. The two main types of biofuels that cars can be run off are biodiesel and bioethanol. Biodiesel is made from rapeseed oil and other plant oils. It can be used in diesel-powered vehicles without any engine modifications.
Bioethanol is not a hydrocarbon as it contains oxygen (hydrocarbons only contain hydrogen and carbon). It is a liquid fuel that burns well. It is made from fermenting sugar from sugar cane, wheat and other plants. Normal petrol engines can use up to 10% ethanol mixed into their fuel without modification but further modification is required as bioethanol makes up more than 10% of the fuel. Most petrol sold in the UK contains some amount of ethanol.
Biofuels are renewable resources as they can be grown fairly quickly. Also, when they are burnt, they release the same amount of carbon dioxide as they have taken in when they were grown. However, they are not carbon neutral because greenhouse gases will be produced during the production of the crops (the planting, watering, fertilising, harvesting and processing of the fuel all produce greenhouse gases). Having said this, they are considerably better for the environment than burning fossil fuels.
Biodiesel.
However there are some negatives. The growing of plants that are used in biofuels takes up land that could have been used to grow crops that would feed the world. This could potentially lead to food shortages or increase the price of food. Alternatively, the growing of biofuels could lead to more deforestation/ destruction of the wild so that we have more room to grow both food and biofuels. There is also a human resource issue as more labour is needed for biofuels than for using conventional fuels. This is because of the planting, maintaining (watering and fertilising), harvesting and processing of biofuels. Normal fossil fuels are just pumped directly out of the ground.
An arguable advantage of biofuels is that they can increase the income of farmers, because fuel prices may rise and the when the price of petrol/ diesel is high, farmers can make more money from growing biofuels instead of normal crops. Another arguable advantage of biofuels is that they can decrease the price of fuel because of an increase in the supply (an increase in the supply leads to more being consumed at a lower price). This can be good for countries’ economic growth and inflation, but a lower price will lead to more consumption of fuels and will increase the amount of carbon dioxide (and other harmful substances) being released into the environment, which is not desirable.
An arguable advantage of biofuels is that they can increase the income of farmers, because fuel prices may rise and the when the price of petrol/ diesel is high, farmers can make more money from growing biofuels instead of normal crops. Another arguable advantage of biofuels is that they can decrease the price of fuel because of an increase in the supply (an increase in the supply leads to more being consumed at a lower price). This can be good for countries’ economic growth and inflation, but a lower price will lead to more consumption of fuels and will increase the amount of carbon dioxide (and other harmful substances) being released into the environment, which is not desirable.