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