SULZER ANALOGY
How nature makes use of solar energy
Thanks to the rays of the sun, selfrenewing materials and energy sources
are available on earth. Today, humans
increasingly use these renewable
resources. In the world of plants and
animals, however, renewable resources
have been widely used since time
immemorial.
Meridian termites enjoy an optimal living climate thanks to solar energy.
T
ermites make passive use of solar
heat in the operation of their enormous residential castles. The meridian
termites in the North Australian steppe
have to live with the fact that temperatures can fall to 5 °C at night but can
reach tropical values during the day.
This species builds itself a nest that is
optimally adapted to this climate. The
base resembles a strongly slanted eye,
with its longitudinal axis aligned exactly
to the local North-South meridian. The
castle becomes increasingly narrow in
height, and finally ends as a narrow
ridge—similar to an axe lying on its
back. When the sun rises above the horizon in the morning, the complete broadside of the structure is exposed to the
sun—after the cool night, the whole nest
benefits from the warmth of the sun’s
radiation. During the hot midday period,
however, the sun is above the narrow
contour of the castle, which protects the
nest from excessive heat.
Hornets create artistic nests from renewable materials.
12 | Sulzer Technical Review 1/2012
Sunlight produces nutrients
tinually refreshed, which facilitates the
Leaves of plants have performed photo- diffusion of gases and water vapor
synthesis for millions of years. They pro- through the stomata on the leaf.
duce vital nutrients from sunlight using
the green chlorophyll pigments. Thereby, Renewables in the hornet’s nest
The use of renewable resources—curthey also provide food for humans and
rently a much discussed topic in technoanimals.
logy—has long been a rule for plants
Cold-blooded animals like reptiles
and animals. Natural organisms cannot
and amphibians make passive use of the
survive over the long term without
sun’s energy to maintain a constant body
sustainable and resource-efficient housetemperature. They use the heat of the
keeping. From the cellulose of vegetable
sun to achieve their optimal operating
cell walls to the chitin of the armored
temperature.
beetles, renewable materials serve as
In addition to solar energy, nature also
makes use of wind energy, which, ulti- natural tools. The paper nest of wasps
mately, is also a variant of solar energy, and hornets are architectural masterpieces.
as the air masses are moved by the ther- Starting from old wood slats, telephone
poles, or old trees, the insects chew off
mals in the atmosphere. The American
fine splinters and shape them into balls
prairie dog, a rodent, builds its extensive
using saliva as glue. From these basic
underground burrow with a number of
exits. One of the
exits ends up in a
The sun heats up and moves air masses.
dome crater that is
Many animals and plants use the energy of
considerably higher
the wind in a clever way.
than the surrounbiological materials, the fertilized female
ding ground. When the prairie wind
hornet builds a first hexagonal cell in
sweeps over this topographical rise, a
the spring to start the nest and glues it
negative pressure arises, which ventilates
under a cover. Over weeks and months,
the burrow, as explained by the Bernoulli
the growing population of hornets builds
principle.
up the nest until a mighty, tiered tower
The typical oscillating movement of
hangs from the cover like an inverted
poplar leaves in the wind also fulfills a
pagoda.
specific purpose. The leaf shape, with
its slightly offset lateral suspensions, and
the elastic leaf stem cause the leaf to
quickly vibrate in the wind. The layer
of air at the leaf’s surface is thereby con- Herbert Cerutti
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