ASSIGNMENT 2 by monkey6


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									                                     ASSIGNMENT 2

 16) How can solar energy be developed for economic domestic use?

  The sun is the earth’s power station and the source of all energy on our planet. The sun’s energy
cannot be used up, so it will never run out. If we can find good ways of using the energy it gives
us, we will have a power supply that is safe, cheap and clean.

  Passive solar systems are systems that are able to capture and use solar energy, without using
any mechanical or electric devices (Many of our homes are passive solar systems). This is
because we use windows or skylights to benefit from solar energy. When sunlight energy comes
into contact with an object (which is not transparent) it converts into heat energy. Modern homes
are designed to keep it warm in winter, but when summer comes, we will have to adjust this
system. In most cases we use simple shades or blinds which will control the amount of energy
entering the room.
  These are examples of passive solar heating:
  In cold climates, houses are usually built facing the sun, and it supplies only one fifth of all
heating needs. This heat can be prevented from escaping by insulating the walls and roof and
using windows with two layers of glass. A glass covered area facing the sun, like a conservatory,
can trap even more of its heat.

  A new French design can provide warm air as required. Houses have a wall facing the sun
painted black, which can absorb a lot of heat. An outer layer of glass stops heat from escaping.
The sun heats up the wall and produces a rising column of warm air, which can be circulated
throughout the house. Because the wall holds the heat for several hours, the system carries on
working after dark and during cloudy periods, when it is most needed. People who live in similar
houses in England found their heating bills went down by 50 percent.

                                     Example of a solar home:
 Solar collectors fitted to the roof, can use the sun’s energy to heat water for household uses. On
our Summer days the solar collector can supply the needs of a household. Electricity is used only
when necessary, and so less energy is wasted. Solar heat systems are designed to heat water to
60° in good weather conditions.

  There are enormous environmental benefits of a solar water heater. Water heating requires
energy. With a solar heat hot water system one can save up to 85% of energy needs. Alternatively
electricity generated from some form of purchased fossil fuel. Indirectly, the burning of fossil fuel
to produce energy causes air pollution as well as consuming a resource which is finite. Countries
like Australia have done studies to show if all users of electric geysers were converted to solar, a
massive 20% reduction of present green house gas emission would result. Each individual solar
hot water system can prevent approx. 4 tons of carbon dioxide from entering the atmosphere
annually. This fact has been taken up by governments around the world who have endorsed solar
hot water system as being an important means of controlling greenhouse gas emission. Besides
the economic benefit of a solar heat hot water system, the environment is also being protected.
  E.g. of a solar heat hot water system
  Another way of harnessing solar energy for economic domestic use is: using solar cookers,
these consist of an insulated box, which has a glass lid; this glass lid captures solar energy and
uses it to heat the food. It uses no electricity and no firewood or paraffin. It uses only the suns
energy, which costs nothing. Using a solar cooker, you can prepare a meal for a family in three to
four hours.

 E.g. of a solar cooker

  Solar dryers can also be used by harnessing solar energy - these are used to create warm
convection currents (hot air rises). Clothes can be dried out by solar energy rather than a tumble
dryer which is noisy and needs electricity.
 Below is a picture of a solar kettle in Tibet. They can be used instead of firewood.

  Some collectors concentrate the suns energy by focusing its rays on a small area. The highest
temperatures are reached by these. Some have curved reflectors which focus the rays onto tubes
containing water to absorb the heat, and some use flat mirrors. Small curved dish reflectors are
now used as solar ovens by campers, and by families in countries where there is often a shortage
of firewood.

 Solar panels can even be used to power refrigerators. In Africa and Asia, travelling teams of
doctors use solar panels to power the refrigerators which store the medicine.

 Today solar energy is used in many household items, like watches and calculators and to
generate power in isolated places. Soon we will be living in homes that keep warm with a
“Thankful of sunshine” – even on cloudy days and winter nights. Instead of switching on a heater
we’ll use saved up heat from the sun.

 Living science: Sound and electricity – Alexander Parson
                  Machines – David Glover

 101 Great Science Experiments – Neil Ardley

 Solar Energy – Graham Rickard

 Energy – Jack Challoner

 Encarta 2001

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