For over 20 long years Dr. H. S. Mukunda of Indian
Institute of Science [IISc], Bangalore has devoted his attention to an
obdurate lad of much promise in the world of alternate energy sources -
the gasifier! Step by patient step, he has made it a viable technology
and a critical scientific community is beginning to take notice.
Gasifiers were darlings of the petroleum starved world
during the war years of the 1940s. Despite the problems that riddled
them, people endured them since they burnt wood chips or coal to produce
gas that drove trucks and buses built originally for petrol and diesel.
Once the war was over they were forgotten -- with a sigh of relief --
except by a few enthusiasts.
The first spark:
As interesting as the story of the gasifier's rebirth,
is that of Mukunda himself. He is of that breed of Indians who come from
modest backgrounds, educate themselves, arrive at fields of study that
are global in vision and proceed to make their mark. Mukunda is one of
the several thousand Indians who quietly work away with dedication and
reinforce hope in the future of the country.
He was born in Hunsur in Mysore district where his
father was a school teacher. Powered by nothing more than intellect and
diligence, he had arrived -- a graduate engineer just out of his teens
-- at IISc in 1969 for his masters work. By 1969 he had earned his
doctorate in Combustion Engineering and joined the IISc faculty.
His adventures with gasifiers began in 1981 when Dr. A.
K. N. Reddy -- a venerable elder at IISc -- was trying to interest
several young scientists there in energy issues. The idea was to
re-explore non-petroleum energy sources -- such as wind, solar, biomass
etc -- that had been abandoned by a lazy world. Earlier in 1975, the
Karnataka State Council for Science and Technology [KSCST] had begun to
support research effort in these areas. Dr. Satish Dhawan the then
Director of IISc was an enthusiast for the programme too.
Thus in 1981, when Dr. Reddy spoke to young Mukunda
about the potential of gasifiers, it was happily a time when many
interests had converged and created the right climate.
Mukunda's fire was lit.
A technology primer:
"Solar energy captured by photosynthesis and
stored in biomass can be converted by the process of gasification into a
high-energy fuel that can be used in internal combustion engines for
power generation," says Dr. Mukunda. The combustible gas --
popularly, producer gas -- is composed of about 20% Hydrogen, 20%
Carbon Monoxide, 3% methane, 10% Carbon di Oxide and the rest Nitrogen.
"The gas will fuel a spark-ignition engine delivering about 60% of
the power of gasoline, or it will run a combustion-ignition [diesel]
engine in dual-fuel mode, eliminating the need for 75 to 85% of the
Obviously the promise was vast. But the equipment then,
was strewn with problems. Gas production was erratic, the gasifier
quickly clogged with tar and consequently maintenance was frequent and
messy. Gasifier design called for getting too many conflicting elements
right and that's what tired researchers.
Around the same time as IISc began to be interested, in
far Colorado, USA Dr. Thomas B. Reed was also conducting his
re-examination of the old promise. Dr. Mukunda credits him with many of
the insights that have revived the gasifier.
Till the 1980s the gasifier was broad in diameter,
stood short, and was loaded with wood chips by opening the top, which
was then closed. The thermal paths within were biased and not all of the
wood chips was utilised in the process.
The key parameters in gasifier design are the diameter
of the machine, its height, the 'throat' from which the gas issues, the
ports through which air is supplied and the construction materials
chosen. Further, if the technology was to be seriously considered for
power production, issues like ease of feeding the gasifier, hours
between maintenance, level of skill required in operating them and cost
competitiveness had to be looked to.
The Bangalore version:
In the early 1980s a 'study-model' was built at IISc
and observations began. The debate in the gasifier world then, in the
main concerned three areas: the virtues of closed top models versus the
open top, how the 'throat' was to be designed and how tar build-up was
to be minimised and slowed.
In May, 1985 the Bangalore version was ready. It
addressed many of the problem areas and incorporated many departures
from past practice. It was a small diameter, tall machine with an open
top. The 'throat' was nearly non-existent. A single air-feed nozzle was
set at a calculated angle, replacing a set of horizontal ones that was
the current practice. It employed a 'reburn' process to fully burn the
feed, reduce tar build-up and improve efficiency. Ceramic lining
components were proposed. [Click
for a technical illustration]
In operation, this version worked longer hours between
maintenance than was the current experience then. Encouraged, the team
began to experiment with several types of fuel and the classical old
'wood' gasifier soon became a 'biomass gasifier'. The idea was to make
use of India's abundant and varied biomass. Mukunda estimates that we
generate 6 to 10 MT of usable urban waste per hectare per year. This too
can now be pelletised and used as an alternate source of energy.
CGPL is born:
In 1972 Mukunda's work having attracted sufficient
interest, Combustion, Gasification and Propulsion Laboratory [CGPL] came
into being in the IISc campus. Funded largely by the Department of
Non-Conventional Energy Sources [DNES], CGPL has been at work tweaking
the gasifier design, scaling it up, commercialising it, creating
intellectual property [it has 6 patents] and popularising it.
Mean hours between overhauls have risen from 1200 hours
to the current 2500 hours. Feeding of the gasifier has been automated
and integrated systems have been built. Mukunda's team has models all
the way from 3.5 kW for farms to nearly 1 mW for industries.
The big break came in 1994. Dr.Hari Sharan a legendary
name in power engineering had left India's BHEL and had joined DASAG,
Switzerland. On one of his visits to India he saw Mukunda's gasifier and
was excited. "Are you open to an independent evaluation?," he
asked. Mukunda was. Soon, 4 men arrived from Switzerland and tests
devised by them began and lasted over 12 days. A European gasifier then
would gum up in 10 to 15 minutes; the Bangalore machine lasted 100
The Swiss were impressed and a
gasifier incorporating Indian innovations was on its way overseas [Chatel
St.Denis, Switzerland]. Soon
an order came from far Chile [Butachaques Island]. In India meanwhile, a one megaWatt plant
is being planned. Arati HiTech Biopower, Sultanpet plans to use coconut
shells available in the neighbouring areas, as feed. The plant will
produce electricity and coconut shell charcoal, a high value industrial
product. The outlay for the project is Rs.3.5 crores. [For
a complete list of installations click here]
Amidst all this, the village boy Mukunda has not
forgotten his origins. As we end the tour of his rambling workshop, he
holds out a tiny application. "This too is a gasifier,"
he says. "It is a domestic stove for rural India that can be
fuelled by fallen leaves. It is in fact a simple upside down gasifier
that gives a clean smoke-free blue flame. I hope it will help reduce the practice
of lopping off branches and felling trees for household cooking."
Dr H S Mukunda
Indian Institute of Science
Bangalore - 560 012
Phones: 01-80-3600536; 3092338; 3092645 &