New Star Software Collection/NSS_Collection.iso/3-251 oo2 english program/1.ima/RR.ZIP/PENERGYE.SEQ

Text File | 1991-06-30 | 3.9 KB | 74 lines

Since fossil fuels are a finite and increasingly expensive
resource, which also cause pollution when used, architects now
have to design buildings which use energy efficiently. In their
search for a solution, they are turning to both old and modern
ideas; they are studying traditional building designs as well as
examining new ways to exploit solar power, an infinite and
non-polluting source of energy.

Energy-efficient buildings have existed for centuries. In hot,
desert areas, for example, the kind of building materials and
the thickness of exterior walls combine to produce comfortable
temperatures both day and night. During the hot day, the heat of
the sun slowly penetrates the stone or mud walls but is unable
to reach the interior of the house before sunset. Then, at
night, when air temperatures are low, the heat stored in the
walls is radiated to the house interior. In this way,
temperatures indoors are cool during the hot day and warm during
the cool night.

In hot, wet climates, where night temperatures remain high,
buildings are constructed to both attract, and increase the
velocity of, air currents. This movement of air causes cooling
by allowing our body sweat to evaporate more quickly. In these
regions. therefore, houses are raised off the ground and their
exterior walls are made of light, open screens in order to allow
the air to pass through more easily.

In the cooler countries, the problem is not how to prevent
overheating, but rather how to conserve heat energy during cold
winters. In order to obtain the maximum benefit from their fuel,
traditional English cottages were built with low ceilings to
reduce the volume to be heated, while small windows and a
well-insulated roof reduced the heat loss. Great attention is
also being paid to solar energy as an alternative to
conventional fossil fuels. Basically, this energy can be
utilised in two ways--either passively, in the design of the
building, or actively, by providing solar collectors.

Passive utilization is concerned mainly with the size, type and
orientation of the windows. For maximum efficiency, windows are
large and consist of a special kind of glass that is transparent
to solar radiation but opaque to the radiation from indoors. In
addition, the windows of buildings in the Northern Hemisphere
face south in order to exploit the weak winter sun as much as
possible. In summer, on the other hand, when the sun is higher
and its radiation more intense, a specially constructed
roof-overhang prevents overheating.

The active utilization of solar energy requires the installation
of solar collectors and a heat storage system. The collectors
are usually situated on the roof of the building at an angle
perpendicular to the direction of midwinter solar radiation.
They may be permanently fixed, or movable so that they can
follow the path of the sun across the sky. Each collector plate
consists of a layer of glass to admit and trap the radiation, a
second layer of dark coloured metal to absorb the heat, and a
third, insulated, layer behind this to prevent any heat loss.
Air or liquid running through pipes in the plates carries away
the heat to a storage system inside the house, from where it can
be withdrawn as required.

Solar energy has three main advantages over conventional fossil
fuels: it is free, it is renewable, and it does not pollute.
However, some problems remain to be solved. It functions poorly
in areas where, for climatic, geographical or local reasons,
solar radiation is insufficient. Also, the heat storage capacity
in most systems is still so low that a backup system using
conventional fuels is usually necessary.

Architects hope that their study of the past and the present
will help them to solve the design problems of the future. As
the energy shortage and the pollution crisis worsen, the need
for such solutions will become increasingly urgent.