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renewable energy — English
Energy derived from a source that is perpetually present or replenished within a short period such as hours or days. Consequently, renewable energy can – theoretically – never be depleted. Solar energy (sunlight) is available during every day that the sun shines and it can be used to heat water, charge batteries which could power ordinary light bulbs, or cook food in a special solar stove (even a cheap, homemade model). Solar energy is nowadays very commonly used all over the world for a variety of installations and equipment; these range from pocket calculators, to cell phone towers, warm water geysers, cookers (stoves), domestic lighting, to power entire buildings, and many more. The only limitations for using solar energy are geographic location (certain regions, such as the polar regions do not receive much sunlight for a few months of the year), cloudy and rainy regions, the high capital outlay to buy and install the solar equipment (these costs are high because the equipment and solar panels are expensive), and so forth. However, even in European countries that receive much less solar energy than we do in South Africa, solar energy is commonly used, and all homes and buildings have to install solar panels. In fact, the entire African continent receives so much sunlight that solar generated electricity could be available to every human being in Africa, but the expense of solar panels, installations and batteries is beyond the financial capability of most Africans. Other forms of renewable energy are falling water which generates hydro-electric power, tidal energy (in the oceans), and wind energy. Hydro-electricity is generated at a number of places in Africa, namely the Cahora Bassa Dam in Mozambique, the Gariep Dam in South Africa, the Katse Dam in Lesotho, the Kariba Dam in Zimbabwe, the Ruacana waterfall on the border between Namibia and Angola, the Owen Falls in Uganda, the Aswan High Dam in Egypt, and some others. In parts of the world – like Canada, Scandinavia, parts of the USA, parts of South America, and New Zealand – where water is more abundant than in Africa, hydro-electricity is the main source of electricity. Wind energy is what is used by an ordinary windpump, of which there are many thousands in Africa. Wind turbines are remarkably effective electricity generators, and they range in size from a small, domestic turbine smaller than a satellite dish and a car battery, to large “wind farms” which generate a lot of electricity which is fed into the general energy network of a country or region. We have one such wind farm in South Africa, namely at Darling in the Western Cape and one is currently under construction at Mossel Bay. The main drawbacks of wind turbines are the limited capacity of the batteries to store the electricity, and the extreme noise caused by the turbines themselves. A wind turbine would be of little help in Pretoria where the wind frequency is exceptionally low, but in regions like the Southern and Eastern Cape and the Free State, wind turbines would be highly successful. Nuclear energy is normally classified as a renewable source of energy (see “nuclear energy”). Strictly speaking, that is incorrect since the plutonium and/or uranium used cannot regenerate, but such small quantities of these materials are used to generate so much electricity that the available supplies on the Earth could never run out. On top of that, the “waste material” remains radio-active for so many thousands of years that we might find out how to use it and thereby lengthen the use of the resource. In practice, nuclear energy can be regarded as a perpetual source of energy. There are, however, many negative factors associated with nuclear energy: the first is the high cost, and the second is the danger of an “accident” causing radio-activity to “leak” into the environment, like at Three Mile Island in the USA, and Chernobyl in Russia, and the Fukushima plant in Japan (see “hazardous waste” and “nuclear energy”). Owing to the dangers inherent to nuclear energy plants and radio-active waste, nuclear energy would probably always be much disputed and controversial. (Note that there are quite a number of environmentally friendly, or relatively so, alternatives to fossil fuel energy, particularly biofuels – [see “fossil fuels”], but thus far certain limitations and high costs have always tipped the scale to the use of dirty, but relatively cheap, fossil fuels. Biofuels are really not even to be considered in low-rainfall and semi-arid environments like South Africa, simply because they do not have the climate to make it viable.)
