It's a well-known fact that the world is dependent on fossil fuels. But how dependent? A survey shows that approximately 95% of our energy, and specifically around 66% of the world's electrical power, is provided by oil, natural gas, and coal.(1) Transportation and petrochemical industries are other examples of areas where oil is used, while natural gas is mainly used for heating systems and as fuel in engines and power stations. As for coal, it is used for producing steam and melting minerals such as iron; but more importantly, it takes the first place in generating electricity, as it provides nearly 60% of the world's demands.(12) Oil, gas, and coal are expected to run out in more or l ...view middle of the document...
In such volcanically active countries as Japan, Italy and the Philippines, hot rocks underground heat water and produce steam. People drill holes into the rocks so that the steam comes up to drive turbogenerators, or passes through heat exchangers to warm houses.(2) Most hot rocks have underground water anyway, and if not, more holes need to be drilled so that water can be pumped in. Geothermal power stations appeared for the first time in Landrello, in Italy and then in New Zealand.(2) Now there are many in Iceland, Japan, the Philippines, and the United States.(2) Because this kind of power relies on the existence of hot rocks and therefore volcanoes, only limited number of countries has benefited from it. Unfortunately, this gives no hope for those countries which don't already have it.Geothermal power has strengths and weaknesses. On the one hand, geothermal power causes no pollution and doesn't harm the environment.(2) Besides, the power stations don't take up much room.(2) What's more, there is no need for fuel, which makes the energy almost free as long as the station is built.(2) Little energy is needed for running the pumps _if there is no water, but even that can be taken from the energy produced.(2) On the other hand, the stations can't be built everywhere. The site should not only consider the hot rocks, but also the depth and the type of rocks above them.(2) It should be easy to drill. In addition, it is difficult to get rid of minerals and hazardous gases if they come up.(2) But the worst drawback is that the steam may run out for decades if the water that is pumped in is too cold.(2)This brings us to another example of a renewable energy resource. Solar power is the energy from the sun. In fact, every minute, enough energy arrives at the Earth to meet the demands of a whole year.(3) There are three main ways of using solar power. Firstly, solar cells, or as they are really called "photovoltaic" or "photoelectric" cells, directly convert light into electricity.(3,8) They were originally developed to provide energy for satellites that orbit the Earth, but nowadays, many of us use them in low-power applications such as calculators.(3) Actually, one square metre of solar panel can run a 100W light bulb.(3) Secondly, solar water heating is a good solution to reduce electricity bills, in which water passes through black painted pipes placed under glass panels on the roof. The pipes absorb sunlight warming the water before it goes back to the tank.(3,8) This method can be successful in places where there is lots of sunshine like California and Australia.(3) Finally, solar furnaces, where large mirrors are arranged to concentrate the sun's energy into a small space, are used for producing extremely high temperatures up to 33,000ºC.(3) A good illustration of this is the Odellio solar furnaces in Fran...
