SIMPLE AND LOW-COST RICE HUSK GAS STOVE DEVELOPED IN INDONESIA

by: Alexis Belonio, Daniel Belonio and Djoewito Atmowidjojo

Indonesia is one of the countries in Asia rich in
biomass resources. Of the available biomass resources
in the country, rice husk accounts for 6.4%. About 12
million metric tons of rice husks is produced annually
in the country which can give a potential heat energy
of 150 x 109 MJ enough to supplement the domestic
energy need for cooking. This energy resource can be
tapped amid the problem on the scarcity and the ever
increasing cost of conventional fuels (e.g., kerosene
and LPG).

With this scenario, the MJ Approtech, in early 2008, embarked its research
and development effort in
finding out solution to
energy problem. One of its
undertakings is focused on utilizing rice husk,
which is abundant in the country, to produce
heat energy for domestic application by
households. Converting rice husk into a
gasified form was proven to be a good
alternative to utilize biomass resources as
replacement to the blue flame and convenience
offered by kerosene and LPG stoves.
In order for the technology to be
available and affordable to all, particularly the
grassroots, the stove must be simple and at the
least cost possible. By simplifying the prototype model of CPU rice husk gas stove
developed in 2005 and by adopting subcontracting method in the production of the
stoves, a simple and low-cost rice husk gas
stove was made commercially available for
Indonesian rural households.

The stove, as shown in x-ray view,
consists of the following components: (1) Cover Assembly, which is composed of the
gas burner and the pot support; (2) Stove Body Assembly, consisting of the casing, the
handle, the shutter, the log, and the fan; and (3) Reactor Assembly, consisting of the
cylindrical-shape reactor and the grate.
Flame Temperature Profile
The Cover Assembly is
removable for easy loading of rice husk
fuel and for discharging the ash. It has a
10-cm opening for the exit of burning
gas. The Stove Body Assembly encloses
the reactor assembly. It has a diameter
of 24 cm and a height of 75 cm. Two
separate handles are fixed into the body
of the stove, opposite to one another, to
facilitate tipping over the stove when
discharging burnt rice husk after
finishing each operation. At the top
portion of the cover assembly is a ring
shatter to control the opening for exit air.
The ring shatter also functions for
cooling the reactor as well as for
regulating the intensity of the flame
coming out of the burner. Four
triangular shape legs are attached to
support the entire structure. They are
made detachable from the stove body for
easy and reduce the space needed in
packaging the stove. In between the two
legs of the stove is a 12-cm diameter
axial fan that is enclosed in a casing to
supply the air needed for gasification.
The axial fan can be energized by AC or
DC current, depending on customer’s
preference. The reactor, where the rice
husk is gasified, has a diameter of 14 cm
and a height of 55 cm. The reactor is
made of 0.8-mm thick stainless steel
sheet with flange at both ends. The
upper part of the reactor has series of 3-mm diameter holes at 2-cm spacing.
Three layers of holes are provided in
each reactor. At the bottom flange, 4
pieces of 3-mm sized holes are provided
as air inlet.


Performance evaluation revealed
that the stove can be operated using
either 16-Watt, 220 volt AC fan or 12
volt, 0.8 Amp DC fan connected to 12
volt motor cycle battery and 1 Amp, 12
volt AC-DC Adaptor. Ignition of fuel
can be done in just a minute with the use
of crumpled pieces of paper as igniter or
by thinly sprinkling kerosene on top of the fuel. The flame produced is yellowish-to-blue
in color. Furthermore, two liters of water can be boiled in 7 minutes and can sustain
continuous
operation for
45 to 60
minutes,
depending on
the rate of
burning the
fuel. The
amount of char
produced after
operation
ranges from 30
to 35%. The
computed fuel
consumption
rate varies from
1.2 to 1.3 kg
per hour,
giving a
specific gasification rate for the stove of 68 to 73 kg/hr-m
2
. The thermal efficiency of the
stove ranges from 23 to 34%, again depending on the operation. The computed power
output varies from 1.0 to 1.6 kW. The temperature of the flame, which was measured
using a thermocouple wire directly at the bottom of the pot ranges from 500 to 850°C.

The stove, with its different components,has a total weight of 12 kg. It is
commercially sold in Indonesia for IDR250,000.00 per unit, including fan and container
box. A rheostat switch, which controls the speed of the fan thereby varying the intensity
of the flame and thus the operating time, can be an added feature of the stove.
Moreover, operating cost analysis showed that the rice husk gas stove only incur a
cost of IDR238.52 per hour which is very much lower than that of kerosene and LPG
stoves with IDR3,042. 83 and IDR915.75 per hour, respectively. At 3 hours per day and
365 days in a year of use of the rice husk gas stove, about a ton ofrice husk is needed by
an average-sized family annually. A savings of IDR3,070,716.67 and IDR741,566.67 can
be realized per year over the use of kerosene and LPG stoves, respectively. And, the
investment for the stove can be recovered in 4 months.
For further information regarding this technology, please contact: The President
Director, PT. Minang Jordanindo Approtech, Techno Park, BSD City, Serpong,
Tangerang, Banten, Indonesia at email address mjapprotech@yahoo.com. You can also
visit our website www.minangjordanindo.comfor more information.
1 US$ = IDR11,610.00
Released: December 2008