Alternative and Renewable Energy
Alternative energy refers to those methods of generating heat and electricity that are not part of traditional power generation. These are not necessarily renewable forms of energy, as we want to promote debate on some of the major energy issues in discussion at the moment, such as nuclear power, 'clean' coal, local combined power and heat stations and hydrogen. Other examples of alternative energy include wind power, solar power, geothermal power, hydroelectric power, wave power, tidal power and biofuels.
Wind power is a source of renewable energy. It has been used for centuries in the traditional form of the windmill. Windmills were used to capture the power of the wind to turn millstones that would grind the wheat into flour for baking bread. More recently they were used extensively in remote, arid areas of Australia's outback to pump water from great depths up to the surface. They are still used for this purpose today across the world.
During the twentieth century, windmills were combined with electricity-generating turbines to produce electricity. The rotation of the blades can be used to turn the giant magnets inside the turbines, which induces an electric current in the wire coils around them. In the past twenty years, wind power as an electricity-generating tool has come on in leaps and bounds. Now, a single wind turbine can produce enough inexpensive electricity to power tens of thousands of homes.
Solar energy is arguable the most renewable of all renewable energy sources. It is estimated that there is enough solar radiation passing into the earth's atmosphere every day to power the world thousands of times over. Ultimately, everything on the planet is solar powered. The wind is even produced by the sun, heating up the air on one side of the world making it expand, creating differences in pressure. The differences in pressure cause the air to move as it tries to even the pressure out again. This is basically what the wind is: an effect of the sun on the atmosphere.
The sun's power can be used to heat water using solar panels. This water can be used to heat homes and businesses, or as a hot water supply. It can also be used to generate electricity. Electricity generation can be done in two ways: By boiling water to drive steam generators, or by taking advantage of the photoelectric effect of certain substances using Solar Photovoltaic (Solar PV) Panels.
Geothermal power is energy extracted from heat within the Earth. Water is pumped downwards through pipes to depths of hundreds of metres below ground level. At this depth the rock is very hot, heated by the magma layer (hot liquid rock) that lies beneath the Earth's crust. The pressure of the water is high enough to force the water back up to surface, where it may have a temperature of over 300 degrees Celsius. When the pressure is released, the water instantly vaporises. When it does this it expands rapidly as steam and drives a turbine to produce electricity. The hot water can also be used to heat homes or as a hot water source.
Another, less spectacular version of geothermal energy is the ground source heat pump system. A long trough is dug to a depth of about a metre, usually in the garden of a house. Water pipes are laid in this trough and then buried. Water is pumped through the pipes and becomes the same temperature as the ground. As the temperature of the earth beneath the surface varies very little throughout the year (usually between 10-15 degrees Celsius), the water can be pumped back into the house where it can help to warm the house during winter and cool it during summer.
Whilst ground source heat pump systems will not always provide enough energy to heat or cool a house by itself, it can be used as an energy saving measure. This means that less gas has to be burnt to warm the house, and less electricity consumed to power fans or air conditioning systems to cool the house.
Ground source heat pump systems can be used anywhere in the world and are inexpensive if they are installed during the construction of the building. Geothermal power, however, is only economically viable if built on a geological hotspot. This means an area with a history of volcanic eruptions or earthquakes. Islands on the volcanic Mid-Atlantic Ridge such as the Azores and Iceland are able to take advantage of geothermal power. The 'Blue Lagoon' in Iceland is actually a man-made lake created by the warm wastewater of a nearby geothermal power station.
Biofuels and Biomass
Biofuels are made from crops such as wheat, sugar cane and oil seed rape. Alcohol and vegetable oil can be made from these crops, which can then be burnt to make energy. Whilst burning the oil or alcohol produces carbon dioxide, the growing of the crops consumed carbon dioxide so the process is said to be carbon neutral.
In counties with large, government-subsidised agricultural industries, biofuels offer a good way to use surplus crops produced by farmers. In France, Diesel fuel is often made up of 90% diesel and 10% biofuel. Vegetable oil can actually be burnt in a modern diesel engine without any modifications. This can get you into trouble, however, as the government will want you to pay fuel duty on any vegetable oil that you consume as fuel.
In Brazil, car engines are often modified to run off ethanol (pure alcohol). Oil is expensive for most Brazilian industries and individuals, particularly in remote areas where supply is problematic, but they are able to grow lots of sugar cane. The sugar cane is fermented and distilled to make an alcoholic solution that they use as fuel.
Biomass includes woodchips and rotting waste. Woodchips can be burnt to heat water in a carbon neutral fashion. Rotting waste from compost heaps and other sources gives off methane, which can be used in gas burners.
Hydroelectric power is the generation of energy from the motion of water, usually by building a dam across a river. Hydroelectric power was one of the first renewable energy sources to find major industrial use. The Hoover dam on the Colorado River in the USA and the Aswan dam on the Nile in Egypt generate huge quantities of inexpensive clean energy. Even Niagara Falls diverts a significant portion of its water through hydroelectric systems to generate energy for nearby cities, including Toronto and Buffalo.
When a dam is built across a river, the water builds up behind it to form a large lake that exerts high pressure on it. The water rushes through pipes within the dam, turning the turbines and generating electricity. It then emerges on the downstream side of the dam and continues on its course down river.
Nuclear power has probably provoked more debate than any other form of energy generation. A controlled nuclear reaction of a radioactive element such as Uranium gives off a lot of heat. This heat can be used to boil water to drive steam turbines.
The only difference between a nuclear power station and a nuclear fission bomb is that the reaction at a power station is prevented from getting out of control. This means that it gives off heat gradually, rather than all at once as it would in a bomb. It is this element of control that is the major cause of worry over the safety of nuclear reactors. The events at Chernobyl in the Ex-Soviet Union and Three Mile Island in the USA are examples of nuclear reactions getting out of control.
However, if operated safely, nuclear energy provides a very consistent supply of energy. It is not entirely carbon free, as the Uranium has to be mined and transported to the power station using carbon dioxide-producing equipment. The radioactive waste then has to be treated and stored for 5000 years. The process of energy generation at the plant does not produce carbon dioxide.
Hydrogen is the most common chemical element in the universe and one of the most reactive. When burnt in oxygen, it gives off more energy than any fossil fuel and the exhaust gas is water vapour. The main problem with using hydrogen as a fuel is that it is not commonly found in its pure form. A lot of energy has to be used to extract the hydrogen from methane or water, and at the moment no one has been able to prove that they can get more energy back from the hydrogen than they put into extracting it.
Most scientists are of the opinion that to do so would violate the physical law of conservation of energy. Some bold claims have been made to the contrary, but none have been proven.
Hydrogen does have a very realistic as an 'energy carrier', rather than an energy source. It could be produced at plants and then used as an alternative to petroleum-based fuels in vehicles. Your car might, one day, run partly or entirely off hydrogen fuel. It would still require the other methods of power generation listed above to produce the pure hydrogen, but could eliminate greenhouse gas emissions from transport.