This document summarizes research investigating how the volume of water inside a Badgir (wind tower) affects temperature reduction through evaporative cooling. The researcher constructed a model Badgir out of wood and adobe. They found that increasing the volume of water available inside the model, by adding more wet cloths, increased the cooling effect. During the experiment, warm air was blown into the model tower, causing evaporation of the water in the cloths and a decrease in temperature. The results supported the hypothesis that a greater volume of water provides more molecules to absorb heat from the air through evaporation, thus producing a larger cooling effect.

1. Evaporative cooling using Badgirs
Research Question: How does the volume of water available inside a Badgir (wind tower) affect temperature reduction
due to evaporative cooling?
Introduction
 Solar energy and warming up
 Temperature
 Water Evaporation
 Factors affecting rate of evaporation
 Entropy
Uncomfortably hot living around the world has led to many
innovative technological solutions to make life more
comfortable for the inhabitants. In the Middle-East, one of
the most successful solutions has been the Badgirs. A Badgir
is a wind-tower consisting of a tower whose top is rising
between 30cm to 5m above the building and its end is
connected to the underground. On the sides of the tower,
there is one vent or more to catch the wind and direct it
inside the building. Inside the tower, there is water in the
form of wet materials attached to the tower lid, a fountain or
a pool of underground water. When the hot wind is directed
inside the tower; it evaporates the water causing a
temperature reduction due to evaporative cooling.
I investigated Badgirs using a model constructed of wood
and adobe. I managed to answer the research question and I
found that as the volume of water available inside the model
increases, the cooling effect increases. Badgirs can naturally
use sun’s energy, wind power and evaporation to air
condition buildings, without producing CO2.
Physics of Badgirs

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Experiment
Making a Model
The model consisted of a tower and a room.
Its inner surface was covered with mud mixed
with horse straw to give it the thermal
properties of a real Badgir.
Providing Water
Five cloths equally sized are attached to the
tower lid so that they can hang inside the
tower and provide water for evaporation.
Providing Heat
A room is heated up to 50℃ , and a fan is used
to blow the warm air inside the model. When
the warm winds blow inside the tower, it
evaporates the water in the wet cloths,
resulting in a decrease in temperature.
Hypothesis
During evaporation, water molecules in the
wet cloths take energy from the warm wind to
escape into air, resulting in a decrease in
temperature inside the model.
As the volume of water is increased, the
number of molecules that can absorb heat
from the hot air increases: Thus, the energy
required to evaporate it increases, resulting in
a greater temperature reduction inside the
model.
Results
The results supported my hypothesis. The
scientific explanation of this phenomenon is
that more cloths offer larger surface area for
more water molecules to evaporate. More
evaporation results in more intake of energy,
therefore greater cooling effect will be. Also,
the heat absorption of adobe walls plays a role
in taking in energy and cooling down the
Model.

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