The energy produced is clean, however, wind power can only be harvested in areas where the wind blows with enough energy throughout the year. Despite the clean energy, wind farms are an eyesore and are also fairly noisy and so in rural areas there are often campaigns to prevent the building of a wind farm. This is a good reason why, as shown in the image of the “Virginia Coastal Energy Research Consortium”, wind farms are often built out to sea, where there are no people to complain about noise pollution and an eyesore.
Water:
We have three main different ways of harnessing the power
water has to offer, these are:
Hydroelectric Power:
The kinetic energy available in large bodies of moving water is phenomenal and has been used as a prominent source of energy for many hundreds of years, to help grinding corn into flower, as with wind, in medieval times and even in Roman and Greek times for the same purpose. These people always used the water wheel to do this work however in more modern times, turbines have been invented, these are used to turn generators in a hydroelectric power station, such as Hoover Dam shown in the image. These power stations use stored gravitational potential energy of water in high reservoirs built in mountains. The gravitational potential energy is converted into kinetic energy as the water flows down the mountain below.
The energy produced in this way is renewable. The sun causes the water to evaporate continuously and to be drawn up into the atmosphere. This water then falls as rain to be collected in reservoirs and used again.
Tidal Power:
The tides also involve the movement of huge amounts of water. Tidal power generation schemes, such as that at La Rance, Brittany, generate power by turning turbines as the tide flows into a dammed river estuary. As the tide falls, the turbines are spun again.
The energy for the movement of the tides is provided by the gravitational pull of the moon and sun. This is a renewable energy source, using a small fractional of the continuous supply of gravitational energy.
Wave Energy:
Energy can also be extracted from waves. The continuous movement of the seas and oceans is the result of the combination of tides and wind. A variety of methods have been developed to make use of the rise and fall of water due to waves. Again, this energy is renewable, as the movement of energy of the waves is continuously available.
Water power is clean, producing no greenhouse gases or unwanted waste products. One drawback of harnessing water power is the visual impact on the environment of features like dams. Another drawback is the means of converting energy from the kinetic energy of water is only available in suitable geographic locations, for example high mountains for hydro-electric power stations and wide estuaries with a big variation in tide for tidal power.
Geothermal:
Geothermal energy is the energy that is stored deep within the core of the earth. The heat in regions of volcanic activity was produced by the decay of radioactive elements, such as uranium. Volcanoes are an indication of the enormous heat sources beneath the earth’s surface, however these do not provide a safe and reliable resource. Heat from the ground, however, can be used safely, countries such as Iceland geothermal energy heats up water in geysers and springs. This is used to drive steam turbines in electric generators. The hot water is also used to provide a domestic heating system by pumping it through pipes directly through houses. This is a renewable resource which does not produce pollution or have a great impact on the environment. Geothermal springs also provide a huge source of relaxation in some areas of the world such as (in the image) Iceland.
Solar Energy:
Solar Heating Systems:
Solar heating panels take up radiated heat from the sun and use it to heat water. They are placed to obtain as much light as possible from the sun. In the northern hemisphere, the must face south in order to achieve this and vice versa in the southern hemisphere.
The composition of a classic solar heating panel is shown on the next page.
Water is pumped through
Copper pipes fixed into a copper
sheet. Copper is used because it
is an excellent conductor. The
surfaces of the sheet and the pipes
have a matt black finish in order
to absorb as much heat radiation as possible. The glass traps a level of air above the copper to help insulate the unit and preserve heat. The backing is also designed to stop heat escaping to the surroundings. This kind of panel is reasonably efficient and the energy produced is more cost effective than that of the photovoltaic cell that is described next. Solar heating panels are used widely to provide water heating. Curved mirrors can also be used to focus thermal radiation onto a boiler or pipes containing water in order to heat them up and so produce steam. The produced steam may then be used to drive a turbine and generate electricity.
Non-renewable Energy Sources:
No-renewable energy sources, such as fossil fuels, will run out, in other words, once we have used them, it will take millions of years to replenish those resources.
Fossil Fuels:
Burning fossil fuels affects the environment, mainly by releasing CO2 into the atmosphere. CO2 is a greenhouse gas, this means that it traps the sun’s heat in the earth’s atmosphere and so cause the average temperature of the atmosphere to rise, and so hence the term “global warming”. Burning coal releases more CO2 than burning oil or gas. Of the most commonly used fossil fuels, natural gas produces the least CO2 for the same energy output. There is no practical way of avoiding the release of CO2 into the atmosphere when burning fossil fuels.
Most types of coal and oil contain sulphur, which, when burned produce sulphur dioxide which in turn is released into the atmosphere. Once in the atmosphere, it reacts with the water molecules that will form rain and so producing sulphuric acid. When sulphuric acid is rained, it causes damage to everything it lands on, from people to buildings and plants. It is possible to remove the sulphur from its source in the coal and oil but this greatly increases the cost of the energy produced. Fossil fuels also provide valuable chemicals that can be used in the manufacture of a wide range of useful products, for example synthetic dyes and gore-tex, however once the fossil fuel has been burned, these useful chemicals are lost forever and so this can be looked upon as being wasteful.
Nuclear Power:
Nuclear reactors use uranium 235 to produce energy, the isotope 235 is needed otherwise the nuclear process cannot proceed. Although a reactor only needs a small amount of uranium, the uranium source is highly limited. Uranium was formed in the unique conditions at the start of the universe so there is no way of increasing our supplies of the radioactive material and so it is non-renewable.
Power generated by the nuclear process has the big advantage of being clean energy and so does not produce any greenhouse gases or other pollutant. The cost per unit of electricity is very low but nuclear power stations are expensive to build. Two large drawbacks of nuclear power is the risk of accidents and the problem of disposing of the nuclear waste once it has been used. The release of uranium or plutonium into the atmosphere can cause long term risks to all living things, such as the nuclear explosion at Chernobyl rendering the area unusable for decades.
Nuclear power stations can be seen in more economically developed countries such as France and America. The image shows a nuclear power plant in Springfield, America(!)
