Alternative sources of energy

Since the time of ancient Egypt, people have used the energy of flowing water to operate machinery and grind grain. However, hydropower had the greatest influence on people’s lives during the 20th century. It played a major role in making the wonders of electricity a part of everyday life and helped spur industrial development. Hydropower continuously produces 24 percent of the world’s electricity and supplies more than 1 billion people with electric energy. Hydropower converts the energy of flowing water into electricity. It comes from damming rivers and utilizing the potential energy stored in the water. As the water stored behind a dam is released at high pressure, its kinetic energy is transferred to turbine blades and used to generate electricity. This system has enormous costs at the beginning, but has relatively low maintenance costs and provides power quite cheaply.

Solar energy is one of the most promising sources of energy for the future. The use of solar energy can be either passive or active. If the heat from direct solar radiation is used in the appropriate construction and orientation of buildings without further technical measures, we talk about the utilization of passive solar energy. However, many technologies have been developed to make use of solar radiation. Some of these technologies, such as solar collectors, are being used to heat rooms or water, while others produce electricity. Solar energy could be used to run cars, power plants, and spacecraft.

Wind power is another alternative energy source and could be used without producing byproducts that are harmful to nature. Electricity generated by wind turbines is absolutely free of emissions, although research is still needed on reducing the noise levels of the turbines. Like solar power, harnessing the wind is highly dependent upon the weather and the location. The application of wind energy converters is attractive only in areas with a high average wind speed, e.g., coastal regions. However, wind turbines can spoil the view of the landscape; aesthetics are therefore another big problem in using wind power.

Geothermal energy is an alternative energy source, although it is not plentiful enough to replace more than a minor amount of future energy needs. Geothermal energy is obtained from the internal heat of the planet and can be used to generate steam to run a steam turbine. This in turn generates electricity. Furthermore, geothermal energy can be used for heating houses and other buildings, the direct heating of greenhouses, or keeping roads free of snow and ice with heat pipes.

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Vitamins

The vitamins necessary for a healthy body are normally supplied by a good mixed diet, including a variety of fruit and green vegetables. It is only when people try to live on a very re­stricted diet, or when trying to lose weight, that it is necessary to make special provision to supply the missing vitamins.

An example of the dangers of a restricted diet may be seen in the disease known as "beri-beri", which large numbers of Eastern peoples who lived mainly on rice used to suffer from. In the early years of this century-a Dutch scientist called Eijkman was trying to discover the cause of beri-beri. At first he thought it was caused by a germ. He was working in a Japanese hospital, where the patients were fed on rice which had the outer husk removed from the grain. It was thought this would be easier far weak, sick people to digest.

Eijkman thought his germ theory was confirmed when he noticed the chickens in the hospital yard, which were fed on scraps from the patients' plates, were also showing signs of the disease. He then tried to isolate the germ which he thought was causing the disease, but his experiments were in­terrupted by a hospital official, who gave out the order that the huskless, milled rice, even though left over by the patients, was too good for chickens, and that it should be recooked and the chick­ens fed on cheap, coarse act with the outer covering still on the grain.

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