Ten rules energy efficient cost effective brick firing
Practical Action
One thing which
emerged from Practical
Action's international
work was the need for
agreement on basic
principles of energy
efficient, cost effective
brickmaking. These
notes propose and
briefly explain ten rules
- good guidelines - for
energy efficiency. The
rules should prove
useful for brickmaking
on any scale with any
technology. They are not
presented in any sort of
priority order.
Figure 2: Slopmaking in a triple mould, Zimbabwe. ©Practical
Action/Theo Schilderman
The Rules
1. Bigger kilns are more efficient
The bigger a kiln is, the smaller its surface area compared to its volume. The volume of a kiln
is proportional to the number of bricks in it. Heat is lost from the surface area of a kiln. So, if
this cooling area becomes proportionally less compared to the volume, more bricks are fired
for relatively less heat loss.
The table below shows how the ratio of surface area to volume decreases as kilns get bigger
and hence, proportionally, the reduction in the energy needed. The table is for a cubic kiln
built with bricks of 230 x 110 x 70 millimetres. Cubic kilns are considered as having four
cooling faces. The heat loss from the top of the kiln - in exhaust gases - and the small loss to
the ground can be considered separately.
Length of side
(m)
2.62
3.30
4.16
5.24
Cooling area, A
(m2)
27.46
43.56
69.22
109.83
Volume, V (m3)
18
36
72
144
No. of bricks
10,000
20,000
40,000
80,000
Ratio A/V
1.53
1.21
0.96
0.76
2